Search

Carbapenemase-producing Klebsiella pneumoniae infections are an increasing global threat with scarce and uncertain treatment options. In this context, combination therapies are often used for these infections. The bactericidal and synergistic activity of fosfomycin plus amikacin and gentamicin was studied trough time–kill assays against four clonally unrelated clinical isolates of carbapenemase-producing K. pneumoniae, VIM-1, VIM-1 plus DHA-1, OXA-48 plus CTXM-15, and KPC-3, respectively. The efficacy of antimicrobials that showed synergistic activity in vitro against all the carbapenemase-producing K. pneumoniae were tested in monotherapy and in combination, in a murine peritoneal sepsis model. In vitro, fosfomycin plus amikacin showed synergistic and bactericidal effect against strains producing VIM-1, VIM-1 plus DHA-1, and OXA-48 plus CTX-M-15. Fosfomycin plus gentamicin had in vitro synergistic activity against the strain producing KPC-3. In vivo, fosfomycin and amikacin and its combination reduced the spleen bacterial concentration compared with controls groups in animals infected by K. pneumoniae producing VIM-1 and OXA-48 plus CTX-M-15. Moreover, amikacin alone and its combination with fosfomycin reduced the bacteremia rate against the VIM-1 producer strain. Contrary to the in vitro results, no in vivo efficacy was found with fosfomycin plus amikacin against the VIM-1 plus DHA-1 producer strain. Finally, fosfomycin plus gentamicin reduced the bacterial concentration in spleen against the KPC-3 producer strain. In conclusion, our results suggest that fosfomycin plus aminoglycosides has a dissimilar efficacy in the treatment of this severe experimental infection, when caused by different carbapenemase-producing K. pneumoniae strains. Fosfomycin plus amikacin or plus gentamycin may be useful to treat infections by OXA-48 plus CTX-M-15 or KPC-3 producer strains, respectively.

The activity of ceftazidime-avibactam was compared with that of ceftazidime alone and meropenem against a collection of 190 Pseudomonas aeruginosa clinical isolates recovered from a multicenter study of bloodstream infections. The addition of avibactam increased ceftazidime susceptibility in the complete collection of strains (64.7% to 91.1%) and particularly among subsets of isolates showing AmpC hyperproduction (10.9% to 76.1%) or multidrug resistance (MDR) profiles (27% to 77.8%). The MICs of ceftazidime-avibactam, in contrast with those of ceftazidime or meropenem, remained at ≤4 μg/ml for a panel of 16 P. aeruginosa PAO1 isogenic mutants expressing multiple combinations of the most relevant β-lactam resistance mechanisms.

OBJECTIVES To evaluate the proficiency of Spanish laboratories regarding accurate susceptibility testing, detection and interpretation of Pseudomonas aeruginosa β-lactam resistance phenotypes. METHODS Thirteen characterized strains were sent to 54 participating centres: clinical strains producing horizontally acquired β-lactamases [extended-spectrum β-lactamases (ESBLs; PER-1 and OXA-161) and class A (GES-5) and B (VIM-2) carbapenemases] and mutants with combinations of chromosomal mechanisms (AmpC, OprD and/or efflux). The centres were requested to evaluate six antipseudomonal β-lactams, provide raw/interpreted clinical categories and detect/infer the resistance mechanisms. Consensus results from reference centres were used to assign minor, major or very major errors (mEs, MEs or VMEs). RESULTS Vitek2, MicroScan WalkAway and Wider were the most used devices (25%-30% each). CLSI/EUCAST breakpoints were used in 86%/14% of the determinations. Discrepancies exclusively due to the differential application of breakpoints were highest for aztreonam, followed by piperacillin/tazobactam. The lowest percentage of VMEs was for Vitek2, followed by Wider. The highest percentages of VMEs (6%) were for the AmpC-hyperproducing OprD(-) strain and for the GES-5 producer, while among antibiotics the highest percentage of VMEs (22%) involved piperacillin/tazobactam. Appropriate inference of resistance mechanisms was high for the VIM-2-producing strain (83%), but low (

Summary Objectives To investigate the epidemiology and clinical features of infections caused by Enterobacteria producing plasmid-mediated AmpC β-lactamases (pAmpC), which are emerging as a cause of resistance to extended-spectrum cephalosporins. Methods A prospective multicentre cohort of patients with infection/colonisation due to pAmpC-producing Enterobacteriaceae was performed in 7 Spanish hospitals from February throughout July 2009. pAmpCs were characterised by PCR and sequencing. Results 140 patients were included; organisms isolated were Escherichia coli ( n = 100), Proteus mirabilis ( n = 20), Klebsiella pneumoniae ( n = 17), and others ( n = 3). Overall, 90% had a chronic underlying condition. The acquisition was nosocomial in 43%, healthcare-associated in 41% (14% of those were nursing home residents), and community in 16%. Only 5% of patients had no predisposing feature for infection with multidrug-resistant bacteria. Nineteen percent of patients were bacteraemic. Inappropriate empirical therapy was administered to 81% of bacteraemic patients, who had a crude mortality rate of 48%. The most frequent enzyme was CMY-2 (70%, predominantly in E. coli and P. mirabilis ) followed by DHA-1 (19%, predominantly in K. pneumoniae ). Conclusion pAmpC-producing Enterobacteriaceae caused nosocomial, healthcare-associated and community infections mainly in predisposed patients. Invasive infections were associated with high mortality which might be partly related to inappropriate empirical therapy.

Transparency declarations M. J. R. has received speaking honoraria from Cubist, Forest, Novartis and Sunovion, consulting fees from Durata, Cubist, Forest, Cepheid and Theravance, and research grant support from Cubist, Forest and Cerexa Pharmaceuticals. G. S. has received speaking honoraria from Cubist, Forest and Novartis Pharmaceuticals, consulting fees from Cubist and Forest Pharmaceuticals, and research grant support from Forest Pharmaceuticals. K. E. B.: none to declare.

Introduccion Se ha evaluado la actividad y capacidad de penetracion de linezolid y vancomicina en biocapas de Staphylococcus epidermidis. Metodos La actividad de linezolid en comparacion con vancomicina se midio frente a biocapas bacterianas de S. epidermidis formadas sobre segmentos de silicona. La penetracion de estos antimicrobianos se midio en las biocapas formadas sobre membranas microporosas de policarbonato. Ambos ensayos se realizaron comparativamente con una cepa de S. epidermidis productora de slime y otra no productora. Resultados La actividad de linezolid frente a biocapas de S. epidermidis fue significativamente mayor que la de vancomicina tanto en la cepa productora de slime como en la no productora. Ninguno de los antimicrobianos erradico las biocapas de 24 h. La penetracion de linezolid en biocapas de S. epidermidis fue mayor que la de vancomicina en todos los tiempos estudiados para ambas cepas. Conclusiones Linezolid ha mostrado mayor actividad in vitro que vancomicina en biocapas de S. epidermidis formadas sobre cateteres de silicona y este efecto podria ser debido a su capacidad para atravesar la biocapa bacteriana.

Resumen Introduccion La resistencia combinada a quinolonas y β-lactamicos es frecuente en enterobacterias. La aparicion en enterobacterias de metalo-β-lactamasas y determinantes de resistencia a quinolonas mediada por plasmidos constituyen un problema emergente en nuestro pais. Metodos La sensibilidad se determino mediante tiras de E-test. Los genes de resistencia se detectaron mediante PCR y se procedio a la caracterizacion de los plasmidos portadores. Resultados En este estudio se describen 2 cepas (1 Klebsiella oxytoca y 1 Klebsiella pneumoniae) portadoras de los genes blaVIM-1 y qnrS2 en un plasmido transferible de 70-Kb aisladas en cultivos de vigilancia en el Hospital Universitario Virgen Macarena de Sevilla. Conclusion Esta es la primera asociacion de blaVIM-1 y qnrS2 en un mismo plasmido no tipable en nuestro centro.

The activities of carbapenems against Pseudomonas aeruginosa decreased in the presence of siliconized latex urinary catheters (SLUCs). This effect was associated with the loss of OprD. The zinc that eluted from SLUCs is responsible for this phenomenon. We have found that zinc exerts a negative effect on the expression of OprD, the porin responsible for carbapenem entry into P. aeruginosa .

We conducted a prospective multicenter study in Spain to characterize the mechanisms of resistance to amoxicillin-clavulanate (AMC) in Escherichia coli . Up to 44 AMC-resistant E. coli isolates (MIC ≥ 32/16 μg/ml) were collected at each of the seven participant hospitals. Resistance mechanisms were characterized by PCR and sequencing. Molecular epidemiology was studied by pulsed-field gel electrophoresis (PFGE) and by multilocus sequence typing. Overall AMC resistance was 9.3%. The resistance mechanisms detected in the 257 AMC-resistant isolates were OXA-1 production (26.1%), hyperproduction of penicillinase (22.6%), production of plasmidic AmpC (19.5%), hyperproduction of chromosomic AmpC (18.3%), and production of inhibitor-resistant TEM (IRT) (17.5%). The IRTs identified were TEM-40 (33.3%), TEM-30 (28.9%), TEM-33 (11.1%), TEM-32 (4.4%), TEM-34 (4.4%), TEM-35 (2.2%), TEM-54 (2.2%), TEM-76 (2.2%), TEM-79 (2.2%), and the new TEM-185 (8.8%). By PFGE, a high degree of genetic diversity was observed although two well-defined clusters were detected in the OXA-1-producing isolates: the C1 cluster consisting of 19 phylogroup A/sequence type 88 [ST88] isolates and the C2 cluster consisting of 19 phylogroup B2/ST131 isolates (16 of them producing CTX-M-15). Each of the clusters was detected in six different hospitals. In total, 21.8% of the isolates were serotype O25b/phylogroup B2 (O25b/B2). AMC resistance in E. coli is widespread in Spain at the hospital and community levels. A high prevalence of OXA-1 was found. Although resistant isolates were genetically diverse, clonality was linked to OXA-1-producing isolates of the STs 88 and 131. Dissemination of IRTs was frequent, and the epidemic O25b/B2/ST131 clone carried many different mechanisms of AMC resistance.

Combined resistance to quinolones and β-lactams is common in Enterobacteriaceae. The appearance in enterobacteria coding for metallo-β-lactamases and determinants of plasmid-mediated quinolone resistance are an emerging problem in our country.The susceptibility was determined by E-test. The resistance genes were detected by PCR and the corresponding plasmids were characterised.This study describes 2 strains (1 Klebsiella oxytoca, 1 Klebsiella pneumoniae) carrying the genes qnrS2 and blaVIM-1 in a transferable plasmid of 70-Kb isolated in surveillance cultures at the University Hospital Virgen Macarena in Seville.This is the first combination of qnrS2 and bla(VIM-1) on the same non-typeable plasmid isolated in our centre.

Tigecycline showed excellent in vitro activity against 50 clinical isolates of Klebsiella pneumoniae producing extended-spectrum beta-lactamases, plasmid-mediated AmpC-type beta-lactamases, or both. This activity was not affected by porin loss. Porin loss, however, did affect the activity of imipenem against strains that expressed both types of enzymes.

The activity and capacity for penetration of linezolid and vancomycin were comparatively evaluated against Staphylococcus epidermidis biofilms.The activity of linezolid versus vancomycin was assessed against 24-hour S. epidermidis biofilms developed on silicon catheters. Penetration of the two antimicrobial agents was measured in biofilms developed on polycarbonate membrane filters. Penetration and activity were comparatively tested using S. epidermidis, slime-producing and non-slime-producing strains.The activity of linezolid against S. epidermidis biofilms was significantly greater than that of vancomycin for both strains. Neither antimicrobial completely eradicated bacterial survival in 24-hour biofilms. Linezolid penetration in biofilms was greater than that of vancomycin for both S. epidermidis strains.Linezolid showed higher in vitro activity than vancomycin against S. epidermidis biofilms on silicone catheters. This effect may be due to the capability of linezolid to cross the bacterial biofilm.

Bacteria exhibiting elevated mutation frequencies may present an enhanced risk for the emergence of antibiotic resistance during chemotherapy ([1][1]). Galan et al. ([2][2]) described a simple method for detecting hypermutable strains in which commercial disks of fosfomycin (50 μg) and rifampin (

Introduction: Antimicrobial resistance in Enterobacteriaceae is increasing worldwide and is making treating infections caused by multidrug-resistant Enterobacteriaceae a challenge. The use of beta-lactam agents is compromised by microorganisms harboring extended-spectrum beta-lactamases (ESBLs) and other mechanisms of resistance. Avibactam is a non beta-lactam agent that inhibits clinically relevant beta-lactamases, such as ESBL and AmpC. The ceftazidime-avibactam combination (CAZ-AVI) was recently approved for use in certain complicated infections, and may provide a therapeutic alternative for infections caused by these microorganisms. Methods: The in vitro activity of CAZ and CAZ-AVI (AVI at a fixed concentration of 4 mg/L) was tested against 250 clinical isolates of Enterobacteriaceae using broth microdilution. EUCAST breakpoint criteria were used for CAZ, and FDA criteria for CAZ-AVI. Clinical isolates included bacteria producing extended spectrum beta-lactamases (ESBLs) and acquired AmpC beta-lactamases (AACBLs). Porin loss in IClebsiella pneumoniae was also evaluated. Results: The combination of AVI with CAZ displayed excellent activity against clinical isolates of ESBL-producing Escherichia coli and Klebsiella pneumoniae, rendering all the ceftazidime-resistant isolates susceptible to ceftazidime. CAZ-AVI retained activity against porin-deficient isolates of K. pneumoniae producing ESBLs, AACBLs, or both, although MIC values were higher compared to porin-expressing isolates. CAZ-AVI rendered all the ceftazidime-resistant AACBL-producing Enterobacteriaceae tested susceptible to ceftazidime. Conclusion: CAZ-AVI showed potent in vitro activity against clinical isolates of Enterobacteriaceae producing ESBLs and/or AACBLs, including K. pneumoniae with loss of porins. (C) 2016 Elsevier Espana, S.L.U. and Sociedad Espanola de Enfermedades Infecciosas y Microbiologia Clinica. All rights reserved.