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Objectives: The usefulness of routine microbiological testing for rationalising antibiotic use in hospitalised patients with community-acquired pneumonia (CAP) continues to be a subject of debate. We aim to determine the effect of positive microbiological testing on antimicrobial de-escalation and clinical outcomes in CAP. Methods: A retrospective analysis of a prospectively collected cohort of non-immunosuppressed adults hospitalised with CAP was performed. The primary study outcome was antimicrobial de-escalation. Secondary outcomes included 30-day case-fatality rate, adverse events, and CAP recurrence. Adjustment for confounders was performed by inverse probability weighting propensity score, logistic regression, and cause-specific Cox model. Results: Of 3677 patients with CAP, 1924 (52.3%) had any positive microbiological test. Antimicrobial de-escalation was performed in 648/1924 (33.7%) of patients with positive microbiological testing and in 179/1753 (10.2%) of those with non-positive results. When propensity score was entered into the multivariate analysis, positive microbiological testing (adjusted OR (AOR)], 2.59; 1.96-3.41) and clinical stability at day 3 (AOR 1.87; 1.45-2.10) were two of the main factors independently associated with antimicrobial de-escalation. After applying an adjusted cause-specific Cox model, antimicrobial de-escalation was not associated with a higher 30-day case-fatality rate (adjusted hazard ratio (AHR), 0.44 (95% CI, 0.14-1.43)), higher frequency of adverse events (AHR, 0.77 (95% CI, 0.53-1.12)), or CAP recurrence (AHR, 0.65 (95% CI, 0.35-1.14)). Discussion: Antimicrobial de-escalation was more often performed in hospitalised patients with CAP who had positive microbiological tests than in those with non-positive results, and it did not adversely affect relevant clinical outcomes.

Animal model; Biofilm; Hyperthermia Model animal; Biofilm; Hipertèrmia Modelo animal; Biofilm; Hipertermia There is currently an urgent need to find new strategies to tackle antimicrobial resistance and biofilm-related infections. This study has two aims. First, we evaluated the in vitro efficacy of hyperthermia in preventing biofilm formation on the surfaces of polyvinyl chloride discs. Second, we assessed the in vivo efficacy of hyperthermia in preventing biofilm formation in endotracheal tubes (ETTs) of a rabbit model. For the in vitro studies, nine clinical extensively drug-resistant/multidrug-resistant Gram-negative isolates of Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa and three clinical methicillin-resistant Staphylococcus aureus strains were studied. For biofilm formation, an adhesion step of 30 or 90 min followed by a growth step of 24 h were performed with application of one, two, and three pulses at 42°C for 15 min each pulse after the adhesion step. For the in vivo studies, New Zealand rabbits were intubated with ETTs previously colonized with K. pneumoniae or P. aeruginosa strains, and three pulses at 42°C for 15 min were applied after the adhesion step. The application of three pulses at 42°C for 15 min each pulse was needed to achieve the prevention of the in vitro biofilm formation of 100% of the tested strains. The application of heat pulses in a rabbit intubation model led to biofilm prevention of 85% against two K. pneumoniae strains and 80% against two P. aeruginosa strains compared to the control group. Hyperthermia application through pulses at 42°C could be a new nonantibiotic strategy to prevent biofilm formation in ETTs. IMPORTANCE Biofilm-producing microorganisms are considered medically crucial since they cause 80% of the infections that occur in the human body. Medical devices such as endotracheal tubes (ETTs) can act as a reservoir for pathogens providing the surface to which microorganisms can adhere and cause biofilm-associated infections in critically ill patients. This biofilm has been related with the development of ventilator-associated pneumonia (VAP), with an incidence of 8 to 28%, a mortality rate up to 17% and its associated high extra costs. Although some VAP-preventive measures have been reported, they have not demonstrated a significant reduction of VAP incidence. Therefore, we present a new nonantibiotic strategy based on hyperthermia application to prevent biofilm formation inside ETTs. This technology could reduce VAP incidence, intubation duration, hospital and intensive care unit (ICU) length stays, and mortality rates. Consequently, this could decrease the antibiotics administered and influence the impact of antibiotic resistance in the ICU. This study was supported by research grants from the Ministerio de Sanidad y Consumo, Instituto de Salud Carlos III (FIS 01162), la Marató TV3 (472/U/2018), the CaixaImpulse Program (Fundació “LaCaixa”), the Fundación para la Innovación y la Prospectiva en Salud en España (FIPSE 3932-21), and the Spanish Network for the Research in Infectious Diseases (REIPI RD19/0016).

Antibacterial agent; Antibiotic stewardship; Primary health care Agente antibacteriano; Administración de antibióticos; Atención primaria de salud Agent antibacterià; Administració d'antibiòtics; Atenció primària de salut Objectives To determine the benefits and harms of discontinuing unnecessary antibiotic therapy for uncomplicated respiratory tract infections (RTI) when antibiotics are considered no longer necessary. Methods Multicentre, open-label, randomized controlled clinical trial in primary care centres from 2017 to 2020 (ClinicalTrials.gov, NCT02900820). Adults with RTIs—acute rhinosinusitis, sore throat, influenza or acute bronchitis—who had previously taken any dose of antibiotic for less than 3 days, which physicians no longer deemed necessary were recruited. The patients were randomly assigned in a 1:1 ratio to discontinuing antibiotic therapy or the usual strategy of continuing antibiotic treatment. The primary outcome was the duration of severe symptoms (number of days scoring 5 or 6 on a six-item Likert scale). Secondary outcomes included days with symptoms, moderate symptoms (scores of 3 or 4), antibiotics taken, adverse events, patient satisfaction and complications within the first 3 months. Results A total of 467 patients were randomized, out of which 409 were considered valid for the analysis. The mean (SD) duration of severe symptoms was 3.0 (1.5) days for the patients assigned to discontinuation and 2.8 (1.3) days for those allocated to the control group (mean difference 0.2 days; 95% CI –0.1 to 0.4 days). Patients randomized to the discontinuation group used fewer antibiotics after the baseline visit (52/207 (25.1%) versus 182/202 (90.1%); p 0.001). Patients assigned to antibiotic continuation presented a relative risk of adverse events of 1.47 (95% CI 0.80–2.71), but the need for further health-care contact in the following 3 months was slightly lower (RR 0.61; 95% CI 0.28–1.37). Conclusions Discontinuing antibiotic treatment for uncomplicated RTIs when clinicians consider it unnecessary is safe and notably reduces antibiotic consumption. This work was supported by the Catalan Society of Family Medicine, grant number FAP1601. The funder of the study had no role in study design, data collection, data analysis, data interpretation, or writing of the report. This trial was registered with the ClinicalTrials.gov database (Identifier: NCT02900820).

Resistencia a los medicamentos; Primeros auxilios; Administración antimicrobiana Drug resistance; Primary health care; Antimicrobial stewardship Resistència als medicaments; Primers auxilis; Administració antimicrobiana Over the last years, the susceptibility activity of the most common microorganisms causing community-acquired infections has significantly changed in Spain. Based on the susceptibility rates of Streptococcus pyogenes, Streptococcus pneumoniae, Haemophilus influenzae, Escherichia coli, and Klebsiella pneumoniae collected from outpatients aged 15 or older with symptoms of respiratory or urinary tract infections in several Microbiology Departments in Catalonia in 2021, penicillin V should be first choice for most respiratory tract infections, amoxicillin and clavulanate for chronic obstructive pulmonary disease exacerbations and a single dose of fosfomycin or a short-course nitrofurantoin should remain first-line treatments for uncomplicated urinary tract infections. Updated information on antimicrobial resistance for general practitioners is crucial for achieving appropriate empirical management of the most common infections by promoting more rational antibiotic use. En los últimos años han cambiado significativamente los porcentajes de sensibilidad de los microorganismos más comunes que causan infecciones adquiridas en la comunidad en España. A partir de los porcentajes de sensibilidad de Streptococcus pyogenes, Streptococcus pneumoniae, Haemophilus influenzae, Escherichia coli y Klebsiella pneumoniae, recogidas de aislados de pacientes ambulatorios de 15 años o más, con síntomas de infecciones respiratorias o urinarias en servicios de microbiología de Cataluña en 2021, fenoximetilpenicilina debería ser la primera opción en la mayoría de los infecciones respiratorias, amoxicilina y ácido clavulánico en las exacerbaciones de la enfermedad pulmonar obstructiva crónica y la monodosis de fosfomicina o la pauta corta de nitrofurantoína como tratamiento de primera línea en las infecciones urinarias no complicadas. Es importante que los médicos de familia dispongan de información actualizada sobre la resistencia a los antimicrobianos para lograr un manejo empírico adecuado de las infecciones más frecuentes al promover un uso más racional de los antibióticos.

In recent years, lignin has drawn increasing attention for different applications due to its intrinsic antibacterial and antioxidant properties, coupled with biodegradability and biocompatibility. However, chemical modification or combination with metals is usually required to increase its antimicrobial functionality and produce biobased added-value materials for applications wherein bacterial growth should be avoided, such as biomedical and food industries. In this work, a sonoenzymatic approach for the simultaneous functionalization and nanotransformation of lignin to prepare metal-free antibacterial phenolated lignin nanoparticles (PheLigNPs) is developed. The grafting of tannic acid, a natural phenolic compound, onto lignin was achieved by an environmentally friendly approach using laccase oxidation upon the application of high-intensity ultrasound to rearrange lignin into NPs. PheLigNPs presented higher antibacterial activity than nonfunctionalized LigNPs and phenolated lignin in the bulk form, indicating the contribution of both the phenolic content and the nanosize to the antibacterial activity. Studies on the antibacterial mode of action showed that bacteria in contact with the functionalized NPs presented decreased metabolic activity and high levels of reactive oxygen species (ROS). Moreover, PheLigNPs demonstrated affinity to the bacterial surface and the ability to cause membrane destabilization. Antimicrobial resistance studies showed that the NPs did not induce resistance in pathogenic bacteria, unlike traditional antibiotics.

CARB-ES-19 is a comprehensive, multicenter, nationwide study integrating whole-genome sequencing (WGS) in the surveillance of carbapenemase-producing K. pneumoniae (CP-Kpn) and E. coli (CP-Eco) to determine their incidence, geographical distribution, phylogeny, and resistance mechanisms in Spain., This research was supported by grants from the Instituto de Salud Carlos III (numbers PI18CIII/00030 and PI21CIII/00039). It was also supported by Plan Nacional de I + D + i 2013–2016, Instituto de Salud Carlos III, Subdirección General de Redes y Centros de Investigación Cooperativa, Ministerio de Economía y Competitividad, Spanish Network for Research in Infectious Diseases (grants RD16CIII/0004/0002, RD16/0016/0001, RD16/0016/0003, RD16/0016/0004, RD16/0016/0006, RD16/0016/0007, RD16/0016/0008, RD16/0016/0010, and RD16/0016/0011). Cofinanced by the European Development Regional Fund “A way to achieve Europe,” Operative Program Intelligent Growth 2014–2020. CIBER – Consorcio Centro de Investigación Biomédica en Red (CB21/13/00095, CB21/13/00012, CB21/13/00049, CB21/13/00054, CB21/13/00055, CB21/13/00068, CB21/13/00081, CB21/13/00084, and CB21/13/00099) (CIBERINFEC) and Instituto de Salud Carlos III, Ministerio de Ciencia e Innovación and Unión Europea – NextGenerationEU also supported this work.

Objectives To investigate if the addition of cloxacillin to vancomycin enhances the activity of both monotherapies for treating MSSA and MRSA experimental endocarditis (EE) in rabbits. Methods Vancomycin plus cloxacillin was compared with the respective monotherapies and daptomycin. In vitro time–kill studies were performed using standard (105 cfu) and high (108 cfu) inocula of five MRSA, one glycopeptide-intermediate (GISA) and five MSSA strains. One MSSA (MSSA-678) and one MRSA (MRSA-277) strain were selected to be used in the in vivo model. A human-like pharmacokinetics model was applied and the equivalents of cloxacillin 2 g/4 h IV and daptomycin 6 mg/kg/day IV were administered. To optimize vancomycin activity, dosage was adjusted to achieve an AUC/MIC ≥400. Results Daptomycin sterilized significantly more vegetations than cloxacillin (13/13, 100% versus 9/15, 60%; P = 0.02) and showed a trend of better activity than vancomycin (10/14, 71%; P = 0.09) and vancomycin plus cloxacillin (10/14, 71%; P = 0.09) against MSSA-678. Addition of cloxacillin to vancomycin (13/15, 87%) was significantly more effective than vancomycin (8/16, 50%; P = 0.05) and showed similar activity to daptomycin (13/18, 72%; P = 0.6) against MRSA-277. In all treatment arms, the bacterial isolates recovered from vegetations were re-tested and showed the same daptomycin susceptibility as the original strains. Conclusions Vancomycin plus cloxacillin proved synergistic and bactericidal activity against MRSA. Daptomycin was the most efficacious option against MSSA and similar to vancomycin plus cloxacillin against MRSA. In settings with high MRSA prevalence, vancomycin plus cloxacillin might be a good alternative for empirical therapy of S. aureus IE.

Incoming

The extracellular matrix protects biofilm cells by reducing diffusion of antimicrobials. Tobramycin is an antibiotic used extensively to treat P. aeruginosa biofilms, but it is sequestered in the biofilm periphery by the extracellular negative charge matrix and loses its efficacy significantly. Dispersal of the biofilm extracellular matrix with enzymes such as DNase I is another promising therapy that enhances antibiotic diffusion into the biofilm. Here, we combine the charge neutralization of tobramycin provided by dextran-based single-chain polymer nanoparticles (SCPNs) together with DNase I to break the biofilm matrix. Our study demonstrates that the SCPNs improve the activity of tobramycin and DNase I by neutralizing the ionic interactions that keep this antibiotic in the biofilm periphery. Moreover, the detailed effects and interactions of nanoformulations with extracellular matrix components were revealed through time-lapse imaging of the P. aeruginosa biofilms by laser scanning confocal microscopy with specific labeling of the different biofilm components.

This article, based on GNEAUPP Technical Paper No. VIII, updates some concepts related to antimicrobials and adds new therapeutic tools to prevent and fight against one of the most important factors that prevent wound healing: problems related to microorganisms, classically infection and now also the impact of biofilms. The GNEAUPP's own evidence grading system is used, which classifies the strength of the recommendation as high, moderate or low. The antimicrobials analyzed in terms of their mode of action, commercial presentation, recommendations for use, contraindications and effectiveness on biofilm are: alcohol, chlorhexidine, sodium hypochlorite, octenidine, silver and iodophors. Also the effects of the so-called antibiofilm agents, although most of them have been performed in vitro. Finally, a series of recommendations are made to researchers to generate new evidence related to antimicrobials and their clinical applicability En este artículo, basado en el documento técnico n.º VIII del GNEAUPP, se actualizan algunos conceptos relacionados con los antimicrobianos y se añaden nuevas herramientas terapéuticas para prevenir y luchar frente a uno de los factores más importantes que impiden que cicatrice una herida: los problemas relacionados con los microorganismos, clásicamente la infección y, ahora, también el impacto de los biofilms. Se asume el sistema propio del GNEAUPP de gradación de la evidencia, que clasifica la fuerza de la recomendación en alta, moderada o baja. Los antimicrobianos analizados mediante su modo de actuación, presentación comercial, recomendaciones de uso, contraindicaciones y efectividad sobre el biofilm son: el alcohol, la clorhexidina, el hipoclorito sódico, la octenidina, la plata y los yodóforos. También los efectos de los llamados agentes antibiofilm, aunque la mayoría se han realizado in vitro. Para finalizar, se realizan una serie de recomendaciones dirigidas a los investigadores para generar nuevas evidencias relacionadas con los antimicrobianos y su aplicabilidad clínica

Antibiotic stewardship programs optimize the use of antimicrobials to prevent the development of resistance and improve patient outcomes. In this prospective interventional study, a multidisciplinary team led by surgeons implemented a program aimed at shortening the duration of antibiotic treatment &lt, 7 days. The impact of the intervention on antibiotic consumption adjusted to bed-days and discharges, and the isolation of multiresistant bacteria (MRB) was also studied. Furthermore, the surgeons were surveyed regarding their beliefs and feelings about the program. Out of 1409 patients, 40.7% received antibiotic therapy. Treatment continued for over 7 days in 21.5% of cases, and, as can be expected, source control was achieved in only 48.8% of these cases. The recommendations were followed in 90.2% of cases, the most frequent being to withdraw the treatment (55.6%). During the first 16 months of the intervention, a sharp decrease in the percentage of extended treatments, with R2 = 0.111 was observed. The program was very well accepted by surgeons, and achieved a decrease in both the consumption of carbapenems and in the number of MRB isolations. Multidisciplinary stewardship teams led by surgeons seem to be well received and able to better manage antibiotic prescription in surgery.

espanolObjetivo. Analizar la sensibilidad a ceftolozano-tazobactam y antimicrobianos comparadores en Enterobacterales y Pseudomonas aeruginosa procedentes de infecciones intraabdominales (IIA), urinarias (ITU) y respiratorias (ITR) y bacteriemias del estudio SMART (Study for Monitoring Antimicrobial Resistance Trends). Metodos. Se analizo (EUCAST-2020) la sensibilidad de 5.351 aislados recogidos en 11 hospitales espanoles (2016- 2018) mediante microdilucion en caldo y se estudio fenotipicamente la presencia de betalactamasas de espectro extendido (BLEE). En aislados resistentes a ceftolozano-tazobactam y/o carbapenemicos se caracterizaron las BLEE y carbapenemasas. Resultados. Escherichia coli fue el patogeno mas frecuente (49,3% IIA, 54,9% ITU, 16,7% ITR y 50% bacteriemia), seguido de Klebsiella pneumoniae (11,9%, 19,1%, 13,1% y 15,4%, respectivamente). P. aeruginosa se aislo en el 9,3%, 5,6%, 32% y 9%, respectivamente. La frecuencia de aislados con BLEE (2016-2017) fue: 30,5% K. pneumoniae, 8,6% E. coli, 2,3% Klebsiella oxytoca y 0,7% Proteus mirabilis. Ceftolozanotazobactam fue muy activo en E. coli no productor (sensibilidad 99,3%) y productor de BLEE (95,2%) y menos activo en K. pneumoniae (98% y 43,1%, respectivamente). CTX-M-15 fue la BLEE mas prevalente en E. coli (27,5%) y K. pneumoniae (51,9%) frecuentemente asociada con OXA-48-like. Un 93% de los aislados de P. aeruginosa fueron sensibles a ceftolozanotazobactam, que mantuvo su actividad (>75%) en aislados resistentes a otros betalactamicos excepto en los resistentes a meropenen o ceftazidima-avibactam. GES-5, PER-1, VIM-1/2 fueron las enzimas mas prevalentes en aislados resistentes a ceftolozano-tazobactam. Conclusiones. Ceftolozano-tazobactam mostro elevada sensibilidad frente a los aislados del estudio SMART, aunque disminuyo en K. pneumoniae y P. aeruginosa con BLEE y/o carbapenemasas. EnglishObjective. To analyse the susceptibility to ceftolozane-tazobactam and comparators in Enterobacterales and Pseudomonas aeruginosa isolates recovered from intraabdominal (IAI), urinary (UTI), respiratory (RTI) and bloodstream infection (BSI) in the SMART (Study for Monitoring Antimicrobial Resistance Trends) study. Methods. The susceptibility of 5,351 isolates collected in 11 Spanish hospitals (2016-2018) were analysed (EUCAST-2020 criteria) by broth microdilution and were phenotypically studied for the presence of extended-spectrum beta-lactamases (ESBL). Ceftolozane-tazobactam and/or carbapenem resistant isolates were genetically characterized for ESBL and carbapenemases. Results. Escherichia coli was the most frequent pathogen (49.3% IAI, 54.9% UTI, 16.7% RTI and 50% BSI), followed by Klebsiella pneumoniae (11.9%, 19.1%, 13.1% and 15.4%, respectively). P. aeruginosa was isolated in 9.3%, 5.6%, 32% and 9%, respectively. The frequency of isolates with ESBLs (2016- 2017) was: 30.5% K. pneumoniae, 8.6% E. coli, 2.3% Klebsiella oxytoca and 0.7% Proteus mirabilis. Ceftolozane-tazobactam was very active against non-ESBL-(99.3% susceptible) and ESBL-(95.2%) producing E. coli being less active against K. pneumoniae (98% and 43.1%, respectively) isolates. CTX-M-15 was the most prevalent ESBL in E. coli (27.5%) and K. pneumoniae (51.9%) frequently associated with OXA-48-like carbapenemase. Overall, 93% of P. aeruginosa isolates were susceptible to ceftolozane-tazobactam, preserving this activity (>75%) in isolates resistant to other beta-lactams except in those resistant to meropenen or ceftazidime-avibactam. GES-5, PER-1, VIM-1/2 were the most prevalent enzymes in isolates resistant to ceftolozane-tazobactam. Conclusions. Ceftolozane-tazobactam showed high activity rates against isolates recovered in the SMART study although it was affected in K. pneumoniae and P. aeruginosa isolates with ESBL and/or carbapenemases.

Documento técnico sobre la microbiología de la herida y la utilización de los antimicrobianos, antibióticos y antisépticos en el cuidado de las heridas crónicas Document tècnic sobre la microbiologia de la ferida i la utilització dels antimicrobians, antibiòtics, i antisèptics en la cura de les ferides cròniques

Background In vitro and in vivo activity of daptomycin alone or plus either cloxacillin or fosfomycin compared with cloxacillin alone and cloxacillin plus gentamicin were evaluated in a rabbit model of MSSA experimental endocarditis (EE). Methods Five MSSA strains were used in the in vitro time–kill studies at standard (105–106 cfu/mL) and high (108 cfu/mL) inocula. In the in vivo EE model, the following antibiotic combinations were evaluated: cloxacillin (2 g/4 h) alone or combined with gentamicin (1 mg/kg/8 h) or daptomycin (6 mg/kg once daily); and daptomycin (6 mg/kg/day) alone or combined with fosfomycin (2 g/6 h). Results At standard and high inocula, daptomycin plus fosfomycin or cloxacillin were bactericidal against 4/5 and 5/5 strains, respectively, while cloxacillin plus gentamicin was bactericidal against 3/5 strains at standard inocula but against none at high inocula. Fosfomycin, cloxacillin, gentamicin and daptomycin MIC/MBCs of the MSSA-678 strain used in the EE model were: 8/64, 0.25/0.5, 0.25/0.5 and 1/8 mg/L, respectively. Adding gentamicin to cloxacillin significantly reduced bacterial density in vegetations compared with cloxacillin monotherapy (P = 0.026). Adding fosfomycin or cloxacillin to daptomycin [10/11 (93%) and 8/11 (73%), respectively] significantly improved the efficacy of daptomycin in sterilizing vegetations [0/11 (0%), P Conclusions The addition of cloxacillin or fosfomycin to daptomycin is synergistic and rapidly bactericidal, showing better activity than cloxacillin plus gentamicin for treating MSSA EE, supporting their clinical use.

Background Despite that measurement uncertainty data should facilitate an appropriate interpretation of measured values, there are actually few reported by clinical laboratories. We aimed to estimate the measurement uncertainty of some β-lactam antibiotics (β-LA), and to evaluate the impact of reporting the measurement uncertainty on clinicians’ decisions while guiding antibiotic therapy. Methods Measurement uncertainty of β-LA (aztreonam [ATM], cefepime [FEP], ceftazidime [CAZ], and piperacillin [PIP]) values, obtained by an UHPLC-MS/MS based-method, was estimated using the top-down approach called the single laboratory validation approach (EUROLAB guidelines). Main uncertainty sources considered were related to calibrators’ assigned values, the intermediate precision, and the bias. As part of an institutional program, patients with osteoarticular infections are treated with β-LA in continuous infusion and monitored to assure values at least 4 times over the minimal inhibitory concentration (4×MIC). We retrospectively evaluated the impact of two scenarios of laboratory reports on clinicians’ expected decisions while monitoring the treatment: reports containing only the β-LA values, or including the β-LA coverage intervals (β-LA values and their expanded measurement uncertainties). Results The relative expanded uncertainties for ATM, FEP, CAZ and PIP were lower than 26.7%, 26.4%, 28.8%, and 25.5%, respectively. Reporting the measurement uncertainty, we identified that clinicians may modify their decision especially in cases where 4×MIC values were within the β-LA coverage intervals. Conclusions This study provides a simple method to estimate the measurement uncertainty of β-LA values that can be easily applied in clinical laboratories. Further studies should confirm the potential impact of reporting measurement uncertainty on clinicians’ decision-making while guiding antibiotic therapy.

Background: Standard treatments against bacterial infections are becoming ineffective due to the rise of antibacterial resistance worldwide. Classical approaches to develop new antibacterial agents are not sufficient to fulfil the current pipeline, therefore new strategies are currently being devised in the field of antibacterial discovery. Objectives: The objective of this narrative review is to compile the most successful strategies for drug discovery within the antibacterial context that are currently being pursued. Sources: Peer-reviewed publications from the MEDLINE database with robust data addressing the discovery of new antibacterial agents in the current pipeline have been selected. Content: Several strategies to discover new antibacterials are described in this review: (i) derivatives of known antibacterial agents; the activity of a known antimicrobial agent can be improved through two strategies: (a) the modification of the original chemical structure of an antimicrobial agent to circumvent antibacterial resistance mechanisms and (b) the development of a compound that inhibits the mechanisms of resistance to an antibacterial agent; (ii) new antibacterial agents targeting new proteins; (iii) inhibitors of virulence factors; (iv) nanoparticles; (v) antimicrobial peptides and peptidomimetics; (vi) phage therapy and enzybiotics; and (vii) antisense oligonucleotides. Implications: This review intends to provide a positive message affirming that several different strategies to design new antibacterial agents are currently being developed, and we are therefore confident that in the near future some of the most promising approaches will come to fruition.

Background Despite their marginal benefit, about 60% of acute lower respiratory tract infections (ALRTIs) are currently treated with antibiotics in Catalonia. This study aims to evaluate the effectiveness and efficiency of a continuous disease-focused intervention (C-reactive protein [CRP]) and an illness-focused intervention (enhancement of communication skills to optimise doctor-patient consultations) on antibiotic prescribing in patients with ALRTIs in Catalan primary care centres. Methods/design A cluster randomised, factorial, controlled trial aimed at including 20 primary care centres (N = 2940 patients) with patients older than 18 years of age presenting for a first consultation with an ALRTI will be included in the study. Primary care centres will be identified on the basis of socioeconomic data and antibiotic consumption. Centres will be randomly assigned according to hierarchical clustering to any of four trial arms: usual care, CRP testing, enhanced communication skills backed up with patient leaflets, or combined interventions. A cost-effectiveness and cost-utility analysis will be performed from the societal and national healthcare system perspectives, and the time horizon of the analysis will be 1 year. Two qualitative studies (pre- and post-clinical trial) aimed to identify the expectations and concerns of patients with ALRTIs and the barriers and facilitators of each intervention arm will be run. Family doctors and nurses assigned to the interventions will participate in a 2-h training workshop before the inception of the trial and will receive a monthly intervention-tailored training module during the year of the trial period. Primary outcomes will be antibiotic use within the first 6 weeks, duration of moderate to severe cough, and the quality-adjusted life-years. Secondary outcomes will be duration of illness and severity of cough measured using a symptom diary, healthcare re-consultations, hospital admissions, and complications. Healthcare costs will be considered and expressed in 2021 euros (year foreseen to finalise the study) of the current year of the analysis. Univariate and multivariate sensitivity analyses will be carried out. Discussion The ISAAC-CAT project will contribute to evaluate the effectiveness and efficiency of different strategies for more appropriate antibiotic prescribing that are currently out of the scope of the actual clinical guidelines. Trial registration ClinicalTrials.gov, NCT03931577.

Concerns have been raised about the long-term accumulating effects of triclocarban, a polychlorinated diarylurea widely used as an antibacterial soap additive, in the environment and in human beings. Indeed, the Food and Drug Administration has recently banned it from personal care products. Herein, we report the synthesis, antibacterial activity and cytotoxicity of novel N,N&prime, diarylureas as triclocarban analogs, designed by reducing one or more chlorine atoms of the former and/or replacing them by the novel pentafluorosulfanyl group, a new bioisostere of the trifluoromethyl group, with growing importance in drug discovery. Interestingly, some of these pentafluorosulfanyl-bearing ureas exhibited high potency, broad spectrum of antimicrobial activity against Gram-positive bacterial pathogens, and high selectivity index, while displaying a lower spontaneous mutation frequency than triclocarban. Some lines of evidence suggest a bactericidal mode of action for this family of compounds.

Objective: The SMART (Study for Monitoring Antimicrobial Resistance Trends) surveillance study monitors antimicrobial susceptibility and extended spectrum β-lactamases (ESBLs) in Gram-negative bacilli recovered from intra-abdominal infections (IAI). Methods: Antimicrobial susceptibility of 5,343 isolates from IAI recovered in 11 centres during the 2011-2015 SMART-Spain program was analysed by standard microdilution (EUCAST criteria) and compared with that from 2002-2010. ESBLs were phenotypically detected. Results: Escherichia coli, the most common isolate, significantly decreased in community acquired IAI (60.9% 2002-2010 vs. 56.1% 2011-2015, P=0.0003). It was followed in prevalence by Klebsiella pneumoniae that increased both in the community (8.9% vs. 10.8%, P=0.016) and nosocomial (9.2% vs. 10.8%, P=0.029) IAI and P. aeruginosa, which significantly increased in community acquired IAI (5.6% vs. 8.0%, P=0.0003). ESBLs were more prevalent in K. pneumoniae (16.3%) than in E. coli (9.5%) of nosocomial origin and were more frequently isolated from elderly patients (>60 years). Considering all Enterobacteriaceae, ertapenem (92.3-100%) and amikacin (95.5%-100%) were the most active antimicrobials. Ertapenem activity, unlike amoxicillin-clavulanate or piperacillin-tazobactam, remained virtually unchanged in ESBL (100%) and non-ESBL (98.8%) E. coli producers. Its activity decreased in ESBL-K. pneumoniae (74.7%) but was higher than that of amoxicillin-clavulanate (14.0%) and piperacillin-tazobactam (24.0%). Interestingly, ertapenem susceptibility was maintained in >60% of ESBL isolates that were resistant to amoxicillin-clavulanate, piperacillin-tazobactam or fluoroquinolones. Conclusions: SMART-Spain results support current guidelines which include ertapenem as empiric treatment in mild-moderate community-acquired IAI, particularly with ESBL producers. These recommendations will need to be updated with the recently introduction of new antimicrobials.

Aim: To assess the properties of a medical device containing xyloglucan, propolis and hibiscus to create a bioprotective barrier to avoid the contact of uropathogenic Escherichia coli strains on cell walls in models of intestinal (CacoGoblet) and uroepithelial (RWPE-1) cells (derived from normal human prostate epithelium). Materials & methods: Two uropathogenic E. coli strains (expressing type 1 fimbriae and P fimbriae) were used to assess, by electronic microscopy and ELISA, the barrier properties of the medical device. The antimicrobial activity was assessed in broth dilution assays. Results: The three components (xyloglucan, propolis and hibiscus) did not alter E. coli cell integrity in intestinal and uroepithelial cell models and were devoid of antibacterial activity. The three components avoided bacterial contact in both cell monolayers. Conclusion: The nonpharmacological barrier properties of xyloglucan, propolis and hibiscus confirm the role of the medical device for the management of urinary tract infections.

Covering: 1947-early 2017, particularly from 2005-early 2017 The rise of bacterial pathogens with acquired resistance to almost all available antibiotics is becoming a serious public health issue. Polymyxins, antibiotics that were mostly abandoned a few decades ago because of toxicity concerns, are ultimately considered as a last-line therapy to treat infections caused by multi-drug resistant Gram-negative bacteria. This review surveys the progress in understanding polymyxin structure, and their chemistry, mechanisms of antibacterial activity and nephrotoxicity, biomarkers, synergy and combination with other antimicrobial agents and antibiofilm properties. An update of recent efforts in the design and development of a new generation of polymyxin drugs is also discussed. A novel approach considering the modification of the scaffold of polymyxins to integrate metabolism and detoxification issues into the drug design process is a promising new line to potentially prevent accumulation in the kidneys and reduce nephrotoxicity.

Objectives: Left-sided methicillin-susceptible Staphylococcus aureus (MSSA) endocarditis treated with cloxacillin has a poorer prognosis when the vancomycin minimum inhibitory concentration (MIC) is >= 1.5 mg/L. We aimed to validate this using the International Collaboration on Endocarditis cohort and to analyse whether specific genetic characteristics were associated with a high vancomycin MIC (> 1.5mg/L) phenotype.Methods: All patients with left-sided MSSA infective endocarditis treated with antistaphylococcal beta-lactam antibiotics between 2000 and 2006 with available isolates were included. Vancomycin MIC was determined by Etest as either high (>= 1.5 mg/L) or low (

Cystic fibrosis (CF) is a genetic disorder in which frequent pulmonary infections develop secondarily. One of the major pulmonary pathogens colonizing the respiratory tract of CF patients and causing chronic airway infections is Pseudomonas aeruginosa. Although tobramycin was initially effective against P. aeruginosa, tobramycin-resistant strains have emerged. Among the strategies for overcoming resistance to tobramycin and other antibiotics is encapsulation of the drugs in nanoparticles. In this study, we explored the antimicrobial activity of nanoencapsulated tobramycin, both in solid lipid nanoparticles (SLN) and in nanostructured lipid carriers (NLC), against clinical isolates of P. aeruginosa obtained from CF patients. We also investigated the efficacy of these formulations in biofilm eradication. In both experiments, the activities of SLN and NLC were compared with that of free tobramycin. The susceptibility of planktonic bacteria was determined using the broth microdilution method and by plotting bacterial growth. The minimal biofilm eradication concentration (MBEC) was determined to assess the efficacy of the different tobramycin formulations against biofilms. The activity of tobramycin-loaded SLN was less than that of either tobramycin-loaded NLC or free tobramycin. The minimum inhibitory concentration (MIC) and MBEC of nanoencapsulated tobramycin were slightly lower (1-2 logs) than the corresponding values of the free drug when determined in tobramycin-susceptible isolates. However, in tobramycin-resistant strains, the MIC and MBEC did not differ between either encapsulated form and free tobramycin. Our results demonstrate the efficacy of nanoencapsulated formulations in killing susceptible P. aeruginosa from CF and from other patients. http://www.mdpi.com/2076-2607/5/3/35

Plasma-sprayed hydroxyapatite coatings were employed industrially for decades to improve osteointegration of articular implants, but many studies have warned about the problems inherent to this procedure (mechanical properties, harmful phases). Consequently, a combination of hydroxyapatite with TiO2 sprayed by high velocity oxy-fuel spray was considered in this study. As infection after joint replacement surgery is one of the most critical concerns when considering implant performance, it is necessary to study possible ways to reduce or eliminate it. Two coating treatments were chosen for this study: addition of a percentage of ZnO and immersion in gentamicin for 24 h. Furthermore, three bacteria were considered: Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The evolution of bacteria viability in solution was measured at 0, 2, and 4 h; and plate assays were performed to study antibacterial effects by diffusion. The results show an important antibacterial effect of the as-sprayed coating, attributed to the presence of -OH radicals on the surface. The presence of ZnO did not have any additional influence on bacteria viability, but gentamicin-treated samples showed an improvement in antibacterial behavior for Gram-negative bacteria in solution, as well as a bactericidal effect in diffusion conditions.

Introduction: Sepsis is a major health issue nowadays. A massive progress has been done since the creation of the Surviving Sepsis Campaign in 2001 in terms of diagnosis, management and outcome, but there still is a long way to go. Still between 10 and 30 per cent of prescribed empirical antibiotics in the ICU are inappropriate (1). It has been proven that inappropriateness of empiric antibiotic treatment is independently associated with a higher mortality (2). Objectives: The goal of this study is to determine if there is an independent association between lactate measurements 24h after diagnosis of sepsis (lactate normalization and lactate clearance) and appropriateness of antibacterial treatment. In order to contribute to reduce the rate of patients receiving inappropriate empiric antibiotics. Methodology: Longitudinal prospective cohort performed in the ICU of the third level teaching facility, Hospital Josep Trueta, in Girona. The study will be performed between 2016 and 2019. Participants: All patients with a community-acquired sepsis or septic shock admitted in the ICU between January 2017 and December 2019

[cat] El problema de la resistència bacteriana ha esdevingut un problema de salut pública global. Cada cop apareixen més soques bacterianes resistents a dos o més fàrmacs i és especialment preocupant la manca d'antibiòtics en el mercat per a combatre les infeccions que aquests provoquen. És per això que un dels grans objectius del descobriment de nous fàrmacs antibiòtics és la recerca de nous compostos capaços de combatre aquests microorganismes. Els pèptids antimicrobians són una classe d'antibiòtics que en el darrers anys han despertat interès degut al seu particular mecanisme d'acció: actuen principalment sobre la membrana bacteriana, i són menys susceptibles de generar resistència per part del bacteris. Destaquem entre aquests pèptids antimicrobians, la polimixina, antibiòtic natural produït pel Bacillus polymyxa. És un compost antibacterià actiu contra bacteris Gram-negatius, però que presenta l'inconvenient de ser tòxic a nivell renal i neuronal. En aquesta tesi es descriu el disseny, la síntesi i l'activitat d'anàlegs de polimixina. Es va simplificar l'esquelet peptídic del producte natural, de manera que fos mes assequible la síntesi química dels anàlegs, la preparació a gran escala, i una potencial reducció de toxicitat. Les modificacions que es van dur a terme van ser substituïr l'enllaç lactàmic que tanca el cicle, per un enllaç disulfur, l'àcid gras natural ramificat, es va substituir per un de lineal, i es van fer substitucions d'alguns aminoàcids per observar l'efecte que provocaven en l'activitat bacteriana. També es van sintetitzar anàlegs retroenantiòmers, per tal de veure la implicació de l'esquelet peptídic en la interacció amb les membranes, i finalment es va preparar un compost conjugat d'un anàleg de polimixina i l'espermina, una poliamina de cadena llarga. Es va estudiar la seva activitat antibiòtica in vitro amb assajos de concentració mínima inhibitòria (CMI). I posteriorment es van realitzar estudis d'activitat biofísica, realitzant assajos amb models de membrana bacteriana, com són els liposomes i les monocapes lipídiques. Aquesta tesi demostra que és possible simplificar l'estructura de la polimixina, obtenint-se compostos antibiòtics actius in vitro que mostren propietats biofísiques similars a les del producte natural., [eng] The problem of bacterial resistance has become a global public health issue. Bacterial strains are becoming resistant to existing drugs and it is particularly worrying lack of antibiotics on the market to fight the infections they cause. That is why one of the major goals of antibiotic drug discovery today is the search for new compounds capable of combating these microorganisms. Antimicrobial peptides are a class of antibiotics that have raised particular interest these recent years due to its mechanism of action: they act primarily on the bacterial membrane, and are less likely to generate resistance by the bacteria. Among these antimicrobial peptides, the polymyxins, natural antibiotic produced by Bacillus polymyxa takes special interest for us. This antibacterial compound is active against Gram-negative bacteria, but it is nephrotoxic an neurotoxic. This thesis describes the design, synthesis and activity of polymyxin analogues. We report a simplified peptide structure, with a chemically accessible scaffold and upscalable, that might show potential toxicity reduction. The modifications that were carried out were substitution of the lactam bond that closes the heptapeptide cycle by a disulphide bond; branched natural fatty acid, was replaced by a linear one, and they were made some amino acid substitutions in order to observe the effect in the bacterial activity. We also synthesize analogues retroenantiomers, to see the involvement of the peptide scaffold when binding to bacterial membranes, and finally it was prepared a conjugate compound of an analogue of polymyxin and spermine, a long chain polyamine. We carried out assays of minimum inhibitory concentration (MIC) in vitro and also studies of biophysics activity, conducting tests with bacterial membrane models, such as liposomes and lipid monolayers. This thesis shows that it is possible to simplify the structure of polymyxin, obtaining active compounds in vitro with biophysical properties that are similar to the natural product.

The magnitudes of MIC for the antibacterial activity and of the IC50 for the antioxidant activity reported in μM are really mM. Thus, in page 84: 0.18-0.34 μM is 0.18-0.34 mM; in Tables 2 and 3: μM is mM; in page 85: 0.12 and 0.14 μM is 0.12 and 0.14 mM; and in page 87: 0.12-0.14 μM is 0.12-0.14 mM. The authors apologize for any inconvenience caused.

This work was supported by grants from the Spanish Ministry of Science and Innovation (Instituto de Salud Carlos III - PI10/01438), the European Regional Development Fund (FEDER), and the Generalitat de Catalunya (2009SGR-108) to EJ, and grants from the Spanish Ministry of Science and Innovation (Instituto de Salud Carlos III - PI081062), the European Regional Development Fund (FEDER),), the Spanish Ministerio de Ciencia e Innovación (BFU2011-24066), the ERA-NET PathoGenoMics, the Ramón y Cajal program and the Catalan and Spanish cystic fibrosis federation to ET. The emergence of multidrug-resistant bacteria has encouraged vigorous efforts to develop antimicrobial agents with new mechanisms of action. Ribonucleotide reductase (RNR) is a key enzyme in DNA replication that acts by converting ribonucleotides into the corresponding deoxyribonucleotides, which are the building blocks of DNA replication and repair. RNR has been extensively studied as an ideal target for DNA inhibition, and several drugs that are already available on the market are used for anticancer and antiviral activity. However, the high toxicity of these current drugs to eukaryotic cells does not permit their use as antibacterial agents. Here, we present a radical scavenger compound that inhibited bacterial RNR, and the compound's activity as an antibacterial agent together with its toxicity in eukaryotic cells were evaluated. First, the efficacy of N-methyl-hydroxylamine (M-HA) in inhibiting the growth of different Gram-positive and Gram-negative bacteria was demonstrated, and no effect on eukaryotic cells was observed. M-HA showed remarkable efficacy against Mycobacterium bovis BCG and Pseudomonas aeruginosa. Thus, given the M-HA activity against these two bacteria, our results showed that M-HA has intracellular antimycobacterial activity against BCG-infected macrophages, and it is efficacious in partially disassembling and inhibiting the further formation of P. aeruginosa biofilms. Furthermore, M-HA and ciprofloxacin showed a synergistic effect that caused a massive reduction in a P. aeruginosa biofilm. Overall, our results suggest the vast potential of M-HA as an antibacterial agent, which acts by specifically targeting a bacterial RNR

Neonatal invasive disease due to Streptococcus agalactiae is life threatening and preventive strategies suitable for resource limited settings are urgently needed. Protective coverage of vaccine candidates based on capsular epitopes will relate to local epidemiology of S. agalactiae serotypes and successful management of critical infections depends on timely therapy with effective antibiotics. This is the first report on serotype distribution and antimicrobial susceptibility of S. agalactiae in pregnant women from a Central African region. Serotypes V, III, and Ib accounted for 88/109 (81%) serotypes and all isolates were susceptible to penicillin and clindamycin while 13% showed intermediate susceptibility to erythromycin.

Introduction The objective of this work was to investigate the risk factors for the acquisition of Pseudomonas aeruginosa and its resistance phenotypes in critically ill patients, taking into account colonization pressure. Methods We conducted a prospective cohort study in an 8-bed medical intensive care unit during a 35-month period. Nasopharyngeal and rectal swabs and respiratory secretions were obtained within 48 hours of admission and thrice weekly thereafter. During the study, a policy of consecutive mixing and cycling periods of three classes of antipseudomonal antibiotics was followed in the unit. Results Of 850 patients admitted for ≥3 days, 751 (88.3%) received an antibiotic, 562 of which (66.1%) were antipseudomonal antibiotics. A total of 68 patients (8%) carried P. aeruginosa upon admission, and among the remaining 782, 104 (13%) acquired at least one strain of P. aeruginosa during their stay. Multivariate analysis selected shock (odds ratio (OR) =2.1; 95% confidence interval (CI), 1.2 to 3.7), intubation (OR =3.6; 95% CI, 1.7 to 7.5), enteral nutrition (OR =3.6; 95% CI, 1.8 to 7.6), parenteral nutrition (OR =3.9; 95% CI, 1.6 to 9.6), tracheostomy (OR =4.4; 95% CI, 2.3 to 8.3) and colonization pressure >0.43 (OR =4; 95% CI, 1.2 to 5) as independently associated with the acquisition of P. aeruginosa, whereas exposure to fluoroquinolones for >3 days (OR =0.4; 95% CI, 0.2 to 0.8) was protective. In the whole series, prior exposure to carbapenems was independently associated with carbapenem resistance, and prior amikacin use predicted piperacillin-tazobactam, fluoroquinolone and multiple-drug resistance. Conclusions In critical care settings with a high rate of antibiotic use, colonization pressure and non-antibiotic exposures may be the crucial factors for P. aeruginosa acquisition, whereas fluoroquinolones may actually decrease its likelihood. For the acquisition of strains resistant to piperacillin-tazobactam, fluoroquinolones and multiple drugs, exposure to amikacin may be more relevant than previously recognized.

[spa] La microscopia de fuerza atómica (AFM) permite estudiar las superficies de materiales biológicos a escala nanométrica y obtener imágenes de elevada resolución de la topografía de la muestra. En este trabajo, la utilización de esta poderosa técnica ha permitido observar, caracterizar y explorar tanto la superficie celular como la estructura del biofilm que forman distintas cepas de Candida albicans, las cuales presentan mutaciones por deleción en genes que codifican por proteínas con un dominio denominado CFEM (Common in several Fungal Extracelular Membrane), que podrían estar implicadas en la formación, desarrollo y/o mantenimiento de la estructura del biofilm en C. albicans. De este modo, se han podido realizar diversos estudios en los que se ha evaluado la rugosidad de las superficies celulares y de los biofilms, parámetro que nos ayuda a caracterizar una superficie; se ha observado la formación, estructura y complejidad de los diferentes biofilms obtenidos; explorado la influencia de diferentes tipos de sustrato en la formación de biofilms y se han analizado las fuerzas de adhesión de las distintas cepas de C. albicans estudiadas ante diversos sustratos, recubiertos con una película formada por componentes de la saliva, mediante la técnica de AFM de espectroscopia de fuerza. Por otro lado, con el fin de estudiar la eficacia de distintos tipos de luz láser de gran aplicación en el tratamiento endodóntico y evaluar el efecto de la terapia fotodinámica en la eliminación de microorganismos, la microscopia de fuerza atómica ha sido de gran utilidad para analizar las lesiones producidas sobre la superficie celular de Enterococcus faecalis tratados con luz láser y terapia fotodinámica, tanto en suspensiones celulares como formando biofilms, mediante la visualización de cambios en la morfología celular y análisis de la rugosidad de superficie. Los estudios realizados aplicando la técnica de AFM han revelado como la falta de expresión de proteínas CFEM por C. albicans puede afectar a la estructura y organización del biofilm, y se ha podido evaluar la influencia positiva de distintos tipos de superficies sobre la adhesión celular. Además, los resultados obtenidos han demostrado un enfoque práctico de la técnica de AFM para examinar alteraciones sustanciales en la superficie celular de E. faecalis, tanto en suspensiones celulares como en biofilms formados por este microorganismo, inducidas después de los tratamientos con luz láser y terapia fotodinámica. El estudio llevado a cabo indica que estos tratamientos podrían ser eficaces en la eliminación de biofilms, erradicación de células persistentes y descontaminación de superficies orales., [eng] The atomic force microscopy (AFM) allows to study several properties of biological surfaces at the nanoscale and also to obtain high resolution images of the sample’s topography. In this work, the use of this powerful technique has allowed us to observe, characterize and explore both the cell surface and biofilm structure forming of different strains of Candida albicans, in which deletion mutations occur in genes encoding proteins with a domain named CFEM (Common in several Fungal Extracellular Membrane). Thus, it was possible to perform various studies that have evaluated the surface roughness parameter, which helped us to characterize cellular and biofilm surfaces; have observed the formation, structure and complexity of the different biofilms obtained; explored the influence of different types of substrate in the formation of biofilms and analyzed the adhesion forces of different strains of C. albicans to various substrates studied by the technique of AFM Force Spectroscopy. Furthermore, in order to study the effectiveness of various types of laser lights of wide application in endodontic treatment and to evaluate the effect of photodynamic therapy in the eradication of microorganisms, atomic force microscopy has been useful for analyzing lesions produced on the cell surface of Enterococcus faecalis treated by laser lights and photodynamic therapy, both cell suspensions as biofilms, by visualizing changes in cell morphology and analysis of surface roughness. Studies using AFM revealed that the lack of CFEM protein expression by C albicans can affect the structure and organization of the biofilm, and we assessed the positive influence of different types of surfaces on cell adhesion. Moreover, the results obtained have shown a practical approach of AFM to examine substantial alterations in cell surface of E. faecalis, both cell suspensions and biofilms formed by this microorganism, induced after treatment with laser light and photodynamic therapy. The study carried out indicated that these treatments could be effective in removing biofilms, persistent cells eradication and decontamination of oral surfaces.

Background: Many interventions aimed at improving the quality of antibiotic prescribing have been investigated, but more knowledge is needed regarding the impact of diff erent intensity interventions. Objectives: To compare the eff ect of two interventions, a basic intervention (BI) and intensive intervention (II), aimed to improve the adherence to recommendations on fi rst-line antibiotics in patients with respiratory tract infections (RTIs). Methods: General practitioners (GPs) from diff erent regions of Spain were off ered two diff erent interventions on antibiotic prescribing. They registered all patients with RTIs during 15 days before (2008) and after (2009) the intervention. GPs in Catalonia were exposed to BI including prescriber feedback, clinical guidelines and training sessions focused on appropriate antibiotic prescribing. The other group of GPs was exposed to an II, which besides BI, also included training and access to point-of-care tests in practice. Results: The GPs registered 15 073 RTIs before the intervention and 12 760 RTIs after. The antibiotic prescribing rate reduced from 27.7% to 19.8%. Prescribing of fi rst-choice antibiotics increased after the intervention in both groups. In the group of GPs following the BI, fi rst-line antibiotics accounted for 23.8% of antibiotics before the intervention and 29.4% after (increase 5.6%, 95% confi dence interval (CI): 1.2 – 10%), while in the group of GPs following the II these fi gures were 26.2% and 48.6% (increase 22.4%, 95% CI: 18.8 – 26%), respectively. Conclusion: Multifaceted interventions targeting GPs can improve adherence to recommendations for fi rst-line antibiotic prescribing in patients with RTI, with intensive interventions that include point-of-care testing being more eff ective.

En la última década hemos asistido a un notable incremento en el número de cepas aisladas en el medio hospitalario que son productoras de β-lactamasas de espectro extendido (BLEE) o, más recientemente, de carbapenemasas. Esta situación hace patente la necesidad de disponer de un sistema de detección rápida de estos mecanismos de resistencia que permita seleccionar de forma precoz el antibiótico más adecuado para poder mejorar la asistencia al paciente. Estudios recientes avalan la posibilidad de usar sistemas de espectrometría de masas (MS), específicamente sistemas MALDI-TOF (Matrix-Assisted Laser Desorption/Ionization, Time-Of-Flight) para identificar determinados mecanismos de resistencia ya que su empleo ofrece diversas ventajas. En primer lugar, el coste económico de cada determinación es claramente inferior al de las técnicas moleculares clásicas de detección de genes de resistencia. En segundo lugar, la detección de resistencias mediante MALDI-TOF permite reducir el tiempo de obtención de resultados en comparación con los métodos de rutina actualmente empleados. Por último, cabe la posibilidad de que nos permita detectar enzimas no descritas previamente, de las que no se dispone de información acerca de los genes que las codifican. Por todo ello, creemos que ésta puede ser una metodología muy útil para implementar en los laboratorios de microbiología clínica. En esta revisión se pretende exponer los últimos avances en esta área.

The antitumor, antibacterial and antioxidant activity, DNA interaction and cathepsin B inhibition of cyclo- ortho -palladated and -platinated compounds [Pd(C,N)] 2 (μ-X) 2 [X = OAc ( 1 ), X = Cl ( 2 )] and trans - N , P -[M(C,N)X(PPh 3 )] [M = Pd, X = OAc ( 3 ), M = Pd, X = Cl ( 4 ), M = Pt, X = Cl ( 5 )] are discussed [(C,N) = cyclo- ortho -metallated benzophenone imine]. The cytotoxicity of compound 5 has been evaluated towards human breast (MDA-MB-231 and MCF-7) and colon (HCT-116) cancer cell lines and that of compounds 1 – 4 towards the HCT-116 human colon cancer cell line. These cytotoxicities have been compared with those previously reported for compounds 1 – 4 towards MDA-MB-231 and MCF-7 cancer cell lines. Compound 3 and 4 were approximately four times more active than cisplatin against the MDA-MB-231 and MCF-7 cancer cell lines, and compound 5 , was approximately four times more potent than cisplatin against the HCT-116 cancer cell line. The antibacterial activity of compounds 1 – 5 was in between the ranges of activity of the commercial antibiotic compounds cefixime and roxithromycin. Complexes 1 – 2 and 4 – 5 presented also antioxidant activity. Compounds 1 – 5 alter the DNA tertiary structure in a similar way to cisplatin , but at higher concentration, and do not present a high efficiency as cathepsin B inhibitors. Compound 5 has not been previously described, and its preparation, characterization, and X-ray crystal structure are reported.

Bacterial biofilms play an important role in urinary tract infections (UTIs), being responsible for persistence infections causing relapses and acute prostatitis. Bacterial forming biofilm are difficult to eradicate due to the antimicrobial resistant phenotype that this structure confers being combined therapy recommended for the treatment of biofilm-associated infections. However, the presence of persistent cells showing reduced metabolism that leads to higher levels of antimicrobial resistance makes the search for new therapeutic tools necessary. Here, a review of these new therapeutic approaches is provided including catheters coated with hydrogels or antibiotics, nanoparticles, iontophoresis, biofilm enzyme inhibitors, liposomes, bacterial interference, bacteriophages, quorum sensing inhibitors, low-energy surface acoustic waves, and antiadhesion agents. In conclusion, new antimicrobial drugs that inhibit bacterial virulence and biofilm formation are needed.

International audience; Background: Acinetobacter baumannii has emerged as an opportunistic nosocomial pathogen causing infections worldwide. One reason for this emergence is due to its natural ability to survive in the hospital environment, which may be explained by its capacity to form biofilms. Cell surface appendages are important determinants of the A. baumannii biofilm formation and as such constitute interesting targets to prevent the development of biofilm-related infections. A chemical agent called virstatin was recently described to impair the virulence of Vibrio cholerae by preventing the expression of its virulence factor, the toxin coregulated pilus (type IV pilus). The objective of this work was to investigate the potential effect of virstatin on A. baumannii biofilms. Results: After a dose-response experiment, we determined that 100 μM virstatin led to an important decrease (38%) of biofilms formed by A. baumannii ATCC17978 grown under static mode. We demonstrated that the production of biofilms grown under dynamic mode was also delayed and reduced. The biofilm susceptibility to virstatin was then tested for 40 clinical and reference A. baumannii strains. 70% of the strains were susceptible to virstatin (with a decrease of 10 to 65%) when biofilms grew in static mode, whereas 60% of strains respond to the treatment when their biofilms grew in dynamic mode. As expected, motility and atomic force microscopy experiments showed that virstatin acts on the A. baumannii pili biogenesis. Conclusions: By its action on pili biogenesis, virstatin demonstrated a very promising antibiofilm activity affecting more than 70% of the A. baumannii clinical isolates.

Over the past three decades, penicillin-resistant pneumococci have emerged worldwide. In addition, penicillin-resistant strains have also decreased susceptibility to other beta-lactams (including cephalosporins) and these strains are often resistant to other antibiotic groups, making the treatment options much more difficult. Nevertheless, the present in vitro definitions of resistance to penicillin and cephalosporins in pneumococci could not be appropriated for all types of pneumococcal infections. Thus, current levels of resistance to penicillin and cephalosporin seem to have little, if any, clinical relevance in nonmeningeal infections (e.g., pneumonia or bacteremia). On the contrary, numerous clinical failures have been reported in patients with pneumococcal meningitis caused by strains with MICs > or = 0.12 microg/ml, and penicillin should never be used in pneumococcal meningitis except when the strain is known to be fully susceptible to this drug. Today, therapy for pneumococcal meningitis should mainly be selected on the basis of susceptibility to cephalosporins, and most patients may currently be treated with high-dose cefotaxime (+/-) vancomycin, depending on the levels of resistance in the patient's geographic area. In this review, we present a practical approach, based on current levels of antibiotic resistance, for treating the most prevalent pneumococcal infections. However, it should be emphasized that the most appropriate antibiotic therapy for infections caused by resistant pneumococci remains controversial, and comparative, randomized studies are urgently needed to clarify the best antibiotic therapy for these infections.

[cat]La presència d’antimicrobians, així com dels seus metabòlits i altres productes de degradació, en el medi ambient ha despertat una forta preocupació durant els últims anys. Com a resultat de l’elevada efectivitat i baix cost d’aquests fàrmacs, el seu ús s’ha estès en medicina humana i veterinària. Pel que fa a la medicina veterinària, aquests compostos s’utilitzen amb finalitat profilàctica, terapèutica i fins i tot com a promotors de creixement en alguns països. Atès que els animals medicats excreten entre un 30 i 90 % de l’agent antimicrobià en la forma no metabolitzada, quan s’utilitzen fems per fertilitzar sòls agrícoles, grans quantitats d’antimicrobians entren contínuament als diferents compartiments ambientals (sòls, sediments, aigües subterrànies i superficials). Els antimicrobians són substàncies bioactives, per tant la seva presència a baixes concentracions, pot afectar la biota, la comunitat microbiana i el que és més preocupant, pot provocar l’aparició de microorganismes patògens resistents. Per tal de preveure destí, comportament ambiental i quantificar la retenció en el sòl d’un fàrmac és important la determinació del coeficient de distribució Kd (L Kg–1). En aquesta tesi s’ha caracteritzat i modelitzat la sorció de les quatre tetraciclines més emprades en veterinària (oxitetraciclina, tetraciclina, clortetraciclina i doxiciclina). S’ha observat que les tetraciclines queden fortament retingudes en el 15 sòls estudiats, amb valors de Kd superiors a 102 L kg–1. Els estudis han posat de manifest que en sòls àcids, el principal mecanisme de sorció és el bescanvi catiònic, mentre que en sòls neutres i bàsics sembla que comencen a ser importants altres tipus d’interaccions (bescanvi catiònic, complexació en superfície, interaccions polars, etc.). El tractament de les dades de sorció mitjançant mètodes quimiomètrics (PCA i PLS) ha permès identificar que les propietats fisicoquímiques del sòl que tenen més influència són pH > CEC > contingut de K2O > contingut de Al2O3 > contingut d’argila. L’estudi de la sorció també ha inclòs el desenvolupament d’un model de sorció que prediu satisfactòriament els log Kd a partir d’aquests 5 descriptors del sòl. D’altra banda, també s’ha establert un model que prediu satisfactòriament els log Kd de tetraciclina, clortetraciclina i doxiciclina a partir de log Kd,oxitetraciclina, pH i CEC corresponents al sòl. El biochar, un tipus de negre de carboni, procedent de la piròlisi de residus de biomassa en absència d’oxigen, s’ha avaluat com a sorbent potencial d’una sulfonamida d’elevada mobilitat (la sulfametazina). En primer lloc, s’han realitzat estudis en el sistema biocharaigua de per tal d’elucidar els mecanismes que tenen lloc en el procés de sorció. S’ha observat que Kd augmenta amb el grau de carbonització (relació H/C) mentre que la linealitat de la isoterma disminueix. D’altra banda, s’ha constatat com el mecanisme i la intensitat de sorció depenen de l’especiació. La sorció segueix el següent ordre: espècie neutra > catiònica > aniònica, amb valors de Kd de fins a 106 L kg-1. Les interaccions Pi-Pi donador-acceptor d’electrons, hidrofòbiques, Van der Waals i ponts d’hidrogen són determinants en la retenció de la sulfametazina en aquests materials. En segon lloc, aquest treball ha posat de manifest que la sorció de sulfametazina en un sòl esmenat amb biochar augmenta amb l’augment del grau de carbonització del biochar i el contingut d’aquest en el sòl. L’estudi també ha demostrat que el temps de contacte entre sòl i biochar poden atenuar aquesta sorció. Per acabar, en aquesta tesi s’ha desenvolupat una nova eina, en un entorn MS-Excel™ pel tractament de dades de sorció: la funció ISOT_Calc i la macro Ref_GN_LM. Aquesta presenta una gran versatilitat en l’estudi d’equilibris de sorció facilitant la selecció del model de sorció, l’ajust de les dades experimentals, etc., [eng]Antimicrobials have long been extensively used to treat infectious disease and promote growth in livestock. Up to 90% of administered sulfonamide drugs can be excreted as the active parent compound and large amounts of sulfonamide residues are released to the environment via land application of contaminated manure. At field concentrations, antimicrobials affect soil microbial community and promote the development of antimicrobial resistance in bacteria. Soil sorption processes dominate transport, fate and possible effects of these chemicals in the environment. Further understanding of mechanisms involved in antimicrobial sorption can definitely help to retard their leaching and run-off to waters. In our studies we have focused on two widely used antimicrobials presenting different environmental mobility: tetracyclines (mostly retained) and sulfonamides (highly mobile). We have determined the sorption coefficients (Kd) of a group of TCs (tetracycline, oxytetracycline, chlortetracycline and doxycycline) in 15 natural soils with different physicochemical properties. The use of multivariate data analyses allowed to elucidate sorption mechanisms involved and to assess the environmental mobility as well. On the other hand, if sulfonamides cannot be prevented from entering soil, we consider of great interest to find means to minimize its transport into ground water and surface waters. Since Biochars is reputed to be a strong adsorbent, we studied the adsorption of the heavily used swine antimicrobial sulfamethazine, to a range of biochars and biochar-amended mixtures to test whether it could reduce pore water concentrations –potentially decreasing sulfamethazine bioavailability– and to provide insights into SMT adsorption. Results showed that depending on biochar physicochemical properties (surface area, surface functional groups, C/H ratio, etc), it could be a potential effective adsorbent for sulfamethazine and decrease its mobility in biochar-amended soils. We have also observed that sulfamethazine retention, significantly decreases with the time of residence of the biochar in soil. This latter phenomenon, commonly known as the “weathering effect”, has been attributed to sorption of native soil substances, such as humic substances. This work has also developed a novel tool (ISOT_Calc/Ref_GN_LM, developed as function and macro for MS-Excel, respectively). The combination of ISOT_Calc/Ref_GN_LM can be used in the evaluation of the isotherm parameters from batch experimental sorption data.

An enantioselective approach to (-)-isoavenaciolide was achieved starting from 1- undecyn-3-ol. The synthesis relied upon the preparation of a chiral 4-silyloxy-2-alkenylborane by hydroboration of a protected 2,3-allenol and subsequent stereoselective addition to 2- thiophenecarboxaldehyde

There is an urgent need for novel antibiotics to treat life-threatening infections caused by bacterial 'superbugs'. Validated in vitro pharmacokinetic/pharmacodynamic (PK/PD) and animal infection models have been employed to identify the most predictive PK/PD indices and serve as key tools in the antibiotic development process. The results obtained can be utilized for optimizing study designs in order to minimize the cost and duration of clinical trials. This review outlines the key in vitro PK/PD and animal infection models which have been extensively used in antibiotic discovery and development. These models have shown great potential in accelerating drug development programs and will continue to make significant contributions to antibiotic development.

Background: Penicillin-resistant strains of Streptococcus pneumoniae are now found worldwide, and strains with resistance to cephalosporin are being reported. The appropriate antibiotic therapy for pneumococcal pneumonia due to resistant strains remains controversial. Methods: To examine the effect of resistance to penicillin and cephalosporin on mortality, we conducted a 10-year, prospective study in Barcelona of 504 adults with culture-proved pneumococcal pneumonia. Results: Among the 504 patients, 145 (29 percent) had penicillin-resistant strains of S. pneumoniae (minimal inhibitory concentration [MIC] of penicillin G, 0.12 to 4.0 μg per milliliter), and 31 patients (6 percent) had cephalosporin-resistant strains (MIC of ceftriaxone or cefotaxime, 1.0 to 4.0 μg per milliliter). Mortality was 38 percent in patients with penicillin-resistant strains, as compared with 24 percent in patients with penicillin-sensitive strains (P = 0.001). However, after the exclusion of patients with polymicrobial pneumonia and adjustment for other predictors of mortality, the odds ratio for mortality in patients with penicillin-resistant strains was 1.0 (95 percent confidence interval, 0.5 to 1.9; P = 0.84). Among patients treated with penicillin G or ampicillin, the mortality was 25 percent in the 24 with penicillin-resistant strains and 19 percent in the 126 with penicillin-sensitive strains (P = 0.51). Among patients treated with ceftriaxone or cefotaxime, the mortality was 22 percent in the 59 with penicillin-resistant strains and 25 percent in the 127 with penicillin-sensitive strains (P = 0.64). The frequency of resistance to cephalosporin increased from 2 percent in 1984-1988 to 9 percent in 1989-1993 (P = 0.002). Mortality was 26 percent in patients with cephalosporin-resistant S. pneumoniae and 28 percent in patients with susceptible organisms (P = 0.89). Among patients treated with ceftriaxone or cefotaxime, mortality was 22 percent in the 18 with cephalosporin-resistant strains and 24 percent in the 168 with cephalosporin-sensitive organisms (P = 0.64). Conclusions: Current levels of resistance to penicillin and cephalosporin by S. pneumoniae are not associated with increased mortality in patients with pneumococcal pneumonia. Hence, these antibiotics remain the therapy of choice for this disease.

Introduction The emergence of multidrug resistant (MDR) Gram-negative bacteria (GNB), including carbapenemase-producing strains, has become a major therapeutic challenge. These MDR isolates are often involved in complicated urinary tract infection (cUTI), and are associated with poor clinical outcomes. The study has been designed to gain insight into the epidemiology, clinical management, outcome and healthcare cost of patients with cUTI, especially in countries with high prevalence of MDR GNB. Methods and analysis This multinational and multicentre observational, retrospective study will identify cases from 1 January 2013 to 31 December 2014 in order to collect data on patients with cUTI as a cause of hospital admission, and patients who develop cUTI during their hospital stay. The primary end point will be treatment failure defined as the presence of any of the following criteria: (1) signs or symptoms of cUTI present at diagnosis that have not improved by days 5–7 with appropriate antibiotic therapy, (2) new cUTI-related symptoms that have developed within 30 days of diagnosis, (3) urine culture taken within 30 days of diagnosis, either during or after completion of therapy, that grows ≥104 colony-forming unit/mL of the original pathogen and (4) death irrespective of cause within 30 days of the cUTI diagnosis. Sample size 1000 patients afford a power of 0.83 (α=0.05) to detect an absolute difference of 10% in the treatment failure rate between MDR bacteria and other pathogens. This should allow for the introduction of about 20 independent risk factors (or their interaction) in a logistic regression model looking at risk factors for failure. Ethics and dissemination Approval will be sought from all relevant Research Ethics Committees. Publication of this study will be considered as a joint publication by the participating investigator leads, and will follow the recommendations of the International Committee of Medical Journal Editors (ICMJE). Trial registration number NCT02641015; Pre-results.

WOS: 000306247300009, PubMed ID: 22658467, This work was focused on the comparison of two clean-up methods to be used for the simultaneous determination of seven cephalosporins in cow muscle. In particular, the performance of novel dispersive solid phase extraction (d-SPE) procedures based on QuEChERS methodologies was assessed and compared with conventional SPE. The separation and detection of the analytes using both methods was carried out by LC-MS/MS to reach enough sensitivity to be compatible with the detection of the maximum residue limits (MRL) of cephalosporins as regulated by EU directives. The optimization of the clean-up step relied on experimental design in order to find the most suitable conditions with a reduced number of assays. Besides, multi-objective responses were used to reach an overall compromise in the recovery of all analytes simultaneously. The validation of the two methods was done according to the Directive 2002/657/EC. Linearity, decision limit, detection capability, detection and quantification limits (4-50 mu kg(-1)), precision (RSD less than 15% except for PIR) and recoveries were determined and adequate results with comparable values using QuEChERS and SPE methodologies. LOQ were better for SPE method (0.1-10 mu g kg(-1)) but both methods show LOQ below MRL values. Precision was slightly better for the QuEChERS method, that also presents better recoveries, higher than 85% except for cephalexin. (C) 2012 Elsevier B.V. All rights reserved., Spanish Ministerio de Educacion y Ciencia [CTQ2010-19044/BQU], We wish to acknowledge the financial support from the Spanish Ministerio de Educacion y Ciencia (Project CTQ2010-19044/BQU).

DE LA TESIS:Desde la aparición de las quinolonas, las resistencias bacterianas a las mismas han evolucionado de forma paralela. Conforme han ido apareciendo nuevas moléculas con mayor capacidad bactericida y mejores parámetros farmacodinámicos y farmacocinéticos, también se han ido identificando nuevos y más sofisticados mecanismos de resistencia, que se han ido adaptando a las necesidades de cada momento. Es por ello que se hace necesaria una nueva metodología para el diseño y la síntesis de nuevos agentes antibacterianos con el objetivo de aumentar su potencia antibacteriana y, al mismo tiempo, disminuir la probabilidad de generar a corto plazo nuevos mecanismos de resistencia. Con este fin, es fundamental conocer todos los mecanismos de resistencia y cuál es, en detalle, su mecanismo de acción, para poder diseñar nuevas moléculas capaces de, manteniendo su capacidad bactericida, eludir dichos mecanismos.En esta tesis nos propusimos como objetivos fundamentales, en primer lugar, investigar las bases moleculares de los mecanismos de resistencia a quinolonas en bacterias Gram-negativas. En concreto, en Escherichia coli, Yersinia enterocolitica y Citrobacter freundii. Por otro lado, se llevaron a cabo cálculos de acoplamiento o "docking" mediante la utilización de programas informáticos con el fin de incrementar nuestros conocimientos respecto al modelo de interacción entra ADN-ADN girasa-quinolona, para de esta manera mejorar nuestra comprensión de los mecanismos de resistencia a fluoroquinolonas asociados a las mutaciones más comúnmente encontradas en el gen gyrA. Finalmente, el último de los objetivos que nos propusimos fue el de diseñar, sintetizar y evaluar diferentes derivados de ciprofloxacino y norfloxacino con el fin de encontrar entre ellos alguno que tuviera la capacidad de interaccionar con la enzima ADN girasa, poseyendo ésta uno o dos cambios aminoacídicos en su subunidad A.

La capacidad de Acinetobacter baumannii para causar infecciones nosocomiales se relaciona con su habilidad para desarrollar rápidamente resistencia a los antibióticos, junto con la capacidad que tiene este organismo para sobrevivir durante largos períodos de tiempo en el hábitat hospitalario.A pesar de ser un problema emergente en la UCIs, falta mucha información sobre los mecanismos de virulencia y resistencia a los antimicrobianos, a la desecación y a la desinfección. Los objetivos principales de este trabajo fueron estudiar los mecanismos de resistencia a diferentes agentes antimicrobianos en cepas clínicas de la especie Acinetobacter, haciendo énfasis en la identificación de nuevas bombas de expulsión y porinas, junto con un estudio del efecto que produce la formación de biopelícula en el éxito de A. baumannii como patógeno.Con A. baumannii, se ha estudiado la prevalencia de bombas de expulsión específicas para tetraciclinas (TetA y TetB) y β-lactamasas en una colección de cepas clínicas españolas. Adicionalmente, se ha estudiado el efecto de la secuencia de inserción ISAba1 como promotor de estas β-lactamasas y se ha concluido que este elemento móvil, que puede ser adquirido o perdido en el ámbito hospitalario, se está convirtiendo en un activador importante de estos genes de resistencia. Paralelamente, se ha analizado la actividad de ceftobiprole y doripenem, dos nuevos β-lactámicos, frente a cepas clínicas de este microorganismo que únicamente ofrecen una pequeña mejoría frente a las antiguas carbapenemas y cefalosporinas. También se ha detectado y secuenciado un gen homológo a mdfA en Escherichia coli que codifica una bomba de expulsión en una cepa clínica de A. baumannii.Aproximaciones genómicas y proteómicas han demostrado ser metodologías importantes para la identificación y caracterización de nuevos mecanismos de resistencia. Se ha hecho un análisis proteómico de una fracción enriquecida en proteínas de membrana en una cepa clínica y un estudio proteómico entre una cepa clínica sensible a quinolonas y un mutante isogénico resistente a quinolonas con la obtención de diversas proteínas de membrana que se sobre-expresaban en el mutante resistente; estas porinas podrían hacer la membrana bacteriana más impermeable a los agentes antimicrobianos. Un análisis de la membrana en mutantes resistentes a colistina demuestran que esta resistencia puede estar asociada a cambios a nivel proteico y a un incremento en la producción de lipopolisacáridos.Finalmente se ha analizado la formación de biopelícula en una colección de cepas clínicas de A. baumannii, estudiando la relación entre la formación de biopelícula y otras características clínicas o microbiológicas. Se ha demostrado que hay una clara asociación entre formación de biopelícula y sensibilidad a imipenem y ciprofloxacino; las cepas resistentes a quinolonas son menos propensas a formar biopelícula que sus equivalentes sensible debido a una expresión reducida de una fimbria de tipo 1, el primer paso en la formación de biopelícula. Además, pacientes tratados previamente con aminoglucósidos tienen un riesgo de ser colonizados o infectados con cepas de A. baumannii formadoras de biopelícula.En este trabajo también se han considerado otras genospecies y se han estudiado los mecanismos de resistencia a quinolonas y colistina, concretamente en cepas de la Genospecie 3 y 13. Cepas clínicas no pertenecientes al grupo A. baumannii están probablemente siendo subestimadas como agentes patogénicos porque las cepas resistentes pueden ser clasificadas como A. baumannii por equivocación. A pesar de que estas cepas son generalmente más sensibles a los antibióticos, están adquiriendo nuevos mecanismos de resistencia.