Search

Humanity is facing an enormous and growing worldwide threat from the emergence of multi-drug-resistant Gram-negative bacteria such as Escherichia coli, Klebsiella pneumoniae, and Acinetobacter baumannii. Polymyxin B and E (colistin) constitute the last-line therapies for treating multi-drug-resistant Gram-negative bacteria. Polymyxin is a cationic antibacterial peptide that can destroy the outer membrane of Gram-negative bacteria. With the increasing clinical application of polymyxin, however, there have been many reports of the occurrence of polymyxin-resistant Gram-negative bacteria. This resistance is mainly mediated by the modification or complete loss of lipopolysaccharide (LPS). LPS is also a virulence factor of Gram-negative bacteria, and alterations of LPS may correlate with virulence. Although it is generally believed that the biological costs associated with drug resistance may enable benign susceptible bacteria to overcome resistant bacteria when antibiotic pressure is reduced, some studies have shown that polymyxin-resistant bacteria are associated with higher virulence and greater fitness compared with their susceptible counterparts. To predict the development of polymyxin resistance and evaluate interventions for its mitigation, it is important to understand the relative biological cost of polymyxin resistance compared with susceptibility. The impact of polymyxin resistance mechanisms on the virulence and fitness of these three Gram-negative bacteria are summarized in this review.

Resistance to host-defense peptides is a critical feature of many pathogens. Previous work in the McPhee lab has demonstrated that different strains of inflammatory bowel disease-associated Escherichia coli exhibit diverse resistance to host defense peptides. The PhoPQ two-component system is a well-characterized signaling pathway that regulates the expression of genes involved in resistance to these peptides. We hypothesize that strains have an altered capacity to signal through this system, resulting in different resistance profiles. We created a promoter-GFP fusion of two PhoPQ regulated genes, pmrD and ompT, to monitor PhoPQ signaling in eight clinical isolates. Our data shows that strains have robust differences in signaling when cultured identical conditions, supporting our hypothesis. Further, our signaling match polymyxin B resistance when using the same isolates and conditions. Our data strongly suggests that strains have an altered potential to respond to environmental signals, ultimately resulting in a broad level of resistance phenotypes.

The rapid increased multidrug resistance in Klebsiella pneumoniae has led to a renewed interest in polymyxin antibiotics, such as colistin, as antibiotics of last resort, not least in low/middle in...

Bacterial resistance has become a major global concern, affecting about 500, 000 individuals in 22 countries. Thus, it is clear that Gram-negative bacteria have been receiving more attention in this scenario. These bacteria perform several resistance mechanisms, such as modifying lipid A from lipopolysaccharides as a product of the mcr-1 gene expression. This gene was initially identified in animals; however, it quickly spread to humans, spreading to 70 countries. Mcr-1 gene attributes resistance to polymyxin B and colistin, which are drugs established as the last alternative to combat Enterobacteriaceae bacteria. Notwithstanding the prevalence and lack of antibiotic therapies for such bacteria, this article aimed to compile information about natural compounds against the resistance attributed by this gene, including the activity of isolated colistin or its associations with other antibiotics. Among the studies that evaluated colistin's synergistic action with other compounds, azidothymidine and isoalantholactone stood out. On the other hand, the paenipeptin 1 analog showed satisfactory activities when associated with other antibiotics. Besides, it is worth mentioning that molecular docking results between ostole and eugenol toward phosphoethanolamine transferase MCR-1 revealed that these compounds could interact with critical amino acid residues for the catalytic action of this enzyme. Based on this, natural agents' role is evident against infections caused by mcr-1-positive bacteria, directly contributing to the development of new effective pharmacotherapies.

Polymyxin B (PMB) is an essential antibiotic active against multidrug-resistant bacteria, such as multidrug-resistant Pseudomonas aeruginosa (MDRP). However, the clinical use of PMB is limited, because PMB causes serious side effects, such as nephrotoxicity and neurotoxicity, probably due to its cytotoxic activity. However, cytotoxic mechanisms of PMB are poorly understood. In this study, we found that macrophages are particularly sensitive to PMB, when compared with other types of cells, including fibroblasts and proximal tubule (PT) cells. Of note, PMB-induced necrosis of macrophages allowed passive release of high mobility group box 1 (HMGB1). Moreover, upon exposure of PMB to macrophages, the innate immune system mediated by the NLR family pyrin domain containing 3 (NLRP3) inflammasome that promotes the release of pro-inflammatory cytokines such as interleukin-1β (IL-1β) was stimulated. Interestingly, PMB-induced IL-1β release occurred in the absence of the pore-forming protein gasdermin D (GSDMD), which supports the idea that PMB causes plasma membrane rupture accompanying necrosis. Emerging evidence has suggested that both HMGB1 and IL-1β released from macrophages contribute to excessive inflammation that promote pathogenesis of various diseases, including nephrotoxicity and neurotoxicity. Therefore, these biochemical properties of PMB in macrophages may be associated with the induction of the adverse organ toxicity, which provides novel insights into the mechanisms of PMB-related side effects.

Polymyxin B (PMB) has reemerged as a last‐line therapy for infections caused by multidrug‐resistant gram‐negative pathogens, but dosing is challenging because of its narrow therapeutic window and pharmacokinetic (PK) variability. Population PK (POPPK) models based on suitably powered clinical studies with appropriate sampling strategies that take variability into consideration can inform PMB dosing to maximize efficacy and minimize toxicity and resistance. Here we reviewed published PMB POPPK models and evaluated them using an external validation data set (EVD) of patients who are critically ill and enrolled in an ongoing clinical study to assess their utility. Seven published POPPK models were employed using the reported model equations, parameter values, covariate relationships, interpatient variability, parameter covariance, and unexplained residual variability in NONMEM (Version 7.4.3). The predictive ability of the models was assessed using prediction‐based and simulation‐based diagnostics. Patient characteristics and treatment information were comparable across studies and with the EVD (n = 40), but the sampling strategy was a main source of PK variability across studies. All models visually and statistically underpredicted EVD plasma concentrations, but the two‐compartment models more accurately described the external data set. As current POPPK models were inadequately predictive of the EVD, creation of a new POPPK model based on an appropriately powered clinical study with an informed PK sampling strategy would be expected to improve characterization of PMB PK and identify covariates to explain interpatient variability. Such a model would support model‐informed precision dosing frameworks, which are urgently needed to improve PMB treatment efficacy, limit resistance, and reduce toxicity in patients who are critically ill.

Hospital-acquired pneumonia (HAP) is defined as an infection in patients admitted in hospital for more than 48hours, and ventilator associated pneumonia (VAP) can be defined as infection occurring in patients admitted in ICU after 48hrs endotracheal intubation and mechanical ventilation. VAP has a mean of 7.3/1000 ventilator days for medical ICU patients and 13.2/1000 ventilator days for surgical ICU patients. The crude mortality rates for HAP are approximately 10% and are higher for VAP, ranging from 20% to 60%. The culture of endotracheal (ET) aspirates will help know the etiological agent and formulate the antibiotic policy for early treatment. To isolate the bacterial pathogens of ET secretions from patients with VAP and know their antibiotic susceptibility pattern. In the present study, out of 102 endotracheal secretions from cases of VAP, 88 samples (86.27%) were culture positive, and the remaining 14 samples (13.73%) were culture negative. Out of the 88 positive cultures, 62 samples (60.78%) showed growth of single isolates, and 26 samples (25.49%) showed multiple isolates. Out of the 114 isolates, 18 isolates (15.8%) were gram positive organisms, and 96 isolates (84.2%) were gram negative organisms. Of the gram positive isolates, the predominant organism was Methicillin resistant (MRSA) (55.56%), followed by Methicillin sensitive (MSSA) (22.22%) and (22.22%). Out of the gram negative isolates, the predominant organism was (36.46%), followed by Acinetobacter spp (25%), (23.96%), (12.5%), (1.04%), and Proteus mirabilis (1.04%). In the present study, Gram positives isolates showed the highest susceptibility to vancomycin and linezolid (100%), and gram negative isolates showed the highest susceptibility to polymyxin B (100%) and meropenem (47.92%). The study gives insight into the bacterial pathogens and their antibiotic susceptibility patterns of isolates from endotracheal secretions of mechanically ventilated patients to prevent the mortality and morbidity of mechanical ventilation and VAP, helping in formulating an antibiotic policy for appropriate empirical therapy.

The aim of the work was the identification and genetic characterization of Vibrio cholerae O1 strains of the El Tor biovar sensitive to polymyxin B among isolates imported to Russia. Materials and methods . We used 56 toxigenic and non-toxigenic strains of V. cholerae isolated from patients and from the environmental samples on the territory of Russia in 1970-2020. Resistance to polymyxin B was determined according to MR4.2.2218-07. The ability of strains to form a biofilm on the abiotic surface was assessed by a photometric method. Nucleotide sequences of genes were determined using UGENE 1.32 and MEGA X software. Phylogenetic analysis and tree construction were performed using "maximum parsimony" method in MEGA X software. Results and discussion . Two genetically modified strains of V. cholerae O1 biovar El Tor, M1509 and 3265/80, which were imported to Russia from India in 2012 and 2014, respectively, were identified. The analysis of 12 genes responsible for the resistance of V. cholerae O1 biovar El Tor strains to polymyxin B demonstrated that these strains contain the allele of the carR S gene, which is typical for all strains of cholera vibrio sensitive to polymyxin B. Study of V. cholerae M1509 and 3265/80 phylogeny based on SNP analysis showed that they fall into the same cluster with isolates containing the carRS allele isolated in India (2015) and Bangladesh (2018). V. cholerae M1509 and 3256/8 strains had the ability to form a biofilm similar to those observed in other genetically modified strains of cholera vibrio included into analysis. Conclusion . Highly virulent strains of the cholera agent with altered diagnostically significant features are imported into Russia, which should be taken into account when identifying V. cholerae O1 biovar El Tor strains isolated from patients and environmental samples during monitoring studies.

Antibiotic pollution of non-clinical environments might have a relevant impact on human health if resistant pathogens are selected. However, this potential risk is often overlooked, since drug concentrations in nature are usually below their minimal inhibitory concentrations (MICs). Albeit, antibiotic resistant bacteria can be selected even at sub-MIC concentrations, in a range known as the sub-MIC selective window. Using short-term evolution experiments, we have determined the sub-MIC selective windows of the opportunistic pathogen Pseudomonas aeruginosa for seven antibiotics of clinical relevance, finding the ones of quinolones to be the widest, and the ones of polymyxin B and imipenem, the narrowest. Clinically relevant multidrug-resistant mutants arose within the sub-MIC selective windows of most antibiotics tested, being some of these phenotypes mediated by efflux pumps' activity. The fact that the concentration of antibiotics reported in aquatic ecosystems - colonizable by P. aeruginosa - are, in occasions, higher than the ones that select multidrug-resistant mutants in our assays, has implications for understanding the role of different ecosystems and conditions in the emergence of antibiotic resistance from a One-Health perspective. Further, it reinforces the importance of procuring accurate information on the sub-MIC selective windows for drugs of clinical value in pathogens with environmental niches.

Justification for continued use of colistin in veterinary medicine, for example medicated water, relies on pharmacokinetic/pharmacodynamic (PK/PD) studies that require accurate measurement of colistin content in the digestive tract. A method for the detection and quantification of colistin in poultry intestinal material was developed and validated. Colistin is not absorbed after oral administration, and the biophase is the gastrointestinal tract. Extraction of colistin from the matrix was achieved using solid-phase extraction with a methanol:water (1:2; v/v) solution. Polymyxin B was used as an internal standard. Colistin A and colistin B, the main components of colistin, were separated, detected and measured using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS). The method was validated for linearity/quadraticity between 1.1 (LOQ) and 56.7 mg/kg. Mean accuracy was between 82.7% and 107.7% with inter- and intra-day precision lower than 13.3% and 15% respectively. Freeze-thaw, long-term and bench storage were validated. Incurred samples following colistin treatment in poultry at the approved clinical dose of 75,000 IU/kg in drinking water and oral gavage were quantifiable and in line with expected intestinal transit times. The method is considered appropriately accurate and precise for the purposes of pharmacokinetic analysis in the gastrointestinal tract.

Aim: To elucidate the changes in protein expression associated with polymyxin resistance in Klebsiella pneumoniae, we profiled a comparative proteomic analysis of polymyxin B-resistant mutants KPC-2-producing K. pneumoniae, and of its susceptible counterparts. Material & methods: Two-dimensional reversed phase nano ultra-performance liquid chromatography mass spectrometry was used for proteomic analysis. Results: Our results showed that the proteomic profile involved several biological processes, and we highlight the downregulation of outer membrane protein A (OmpA) and the upregulation of SlyB outer membrane lipoprotein (conserved protein member of the PhoPQ regulon) and AcrA multidrug efflux pump in polymyxin B-resistant strains. Conclusion: Our results highlight the possible participation of the SlyB, AcrA and OmpA proteins in the determination of polymyxin B heteroresistance in KPC-2-producing K. pneumoniae.

Objective To investigate how to use polymyxin B rationally in order to produce the best efficacy and safety in patients with carbapenem-resistant gram-negative organisms (CRO) infection. Methods The clinical characteristics and microbiological results of 181 patients caused by CRO infection treated with polymyxin B in the First Affiliated Hospital from July 2018 to May 2020 were retrospectively analyzed. The bacterial clearance rate, clinical efficacy, adverse drug reactions and 28 days mortality were evaluated. Results The overall effective rate of 181 patients was 49.72%, the total bacterial clearance rate was 42.0%, and the 28 day all-cause mortality rate was 59.1%. The effective rate and bacterial clearance rate in the group of less than 24 h from the isolation of CRO to the use of polymyxin B were significantly higher than those in the group of more than 24 h. Logistics multivariate regression analysis showed that the predictive factors for effective treatment of CRO with polymyxin B were APACHEII score, duration of polymyxin B treatment, combination of polymyxin B and other antibiotics, and bacterial clearance. 17 cases (9.36%) of acute kidney injury were considered as polymyxin B nephrotoxicity and 4 cases (23.5%) recovered after polymyxin B withdrawal. After 14 days of polymyxin B use, 3 cases of polymyxin B resistance appeared, and there were 2 cases of polymyxin B resistance in the daily dose 1.5 mg/kg/day group. Conclusion For CRO infection, the treatment of polymyxin B should be early, combined, optimal dose and duration of treatment, which can achieve better clinical efficacy and microbial reactions, and reduce the adverse reactions and drug resistance.

Purpose Previously, we showed that tear fluid protects corneal epithelial cells against Pseudomonas aeruginosa without suppressing bacterial viability. Here, we studied how tear fluid affects bacterial gene expression. Methods RNA-sequencing was used to study the P. aeruginosa transcriptome after tear fluid exposure (5 h, 37 oC). Outcomes were further investigated by biochemical and physiological perturbations to tear fluid and tear-like fluid (TLF) and assessment of bacterial viability following tear/TLF pretreatment and antibiotic exposure. Results Tear fluid deregulated ~180 P. aeruginosa genes ≥8 fold versus PBS including downregulating lasI, rhlI, qscR (quorum sensing/virulence), oprH, phoP, phoQ (antimicrobial resistance) and arnBCADTEF (polymyxin B resistance). Upregulated genes included algF (biofilm formation) and hemO (iron acquisition). qPCR confirmed tear down-regulation of oprH, phoP and phoQ. Tear fluid pre-treatment increased P. aeruginosa resistance to meropenem ~5-fold (4 μg/ml), but enhanced polymyxin B susceptibility ~180-fold (1 μg/ml), the latter activity reduced by dilution in PBS. Media containing a subset of tear components (TLF) also sensitized bacteria to polymyxin B, but only ~22.5-fold, correlating with TLF/tear fluid Ca2+ and Mg2+ concentrations. Accordingly, phoQ mutants were not sensitized by TLF or tear fluid. Superior activity of tear fluid versus TLF against wild-type P. aeruginosa was heat resistant but proteinase K sensitive. Conclusion P. aeruginosa responds to human tear fluid by upregulating genes associated with bacterial survival and adaptation. Meanwhile, tear fluid down-regulates multiple virulence-associated genes. Tears also utilize divalent cations and heat resistant/proteinase K sensitive component(s) to enhance P. aeruginosa sensitivity to polymyxin B.

Aims Carbapenem-resistant Acinetobacter baumannii represents a public health problem, and the search for new antibacterial drugs has become a priority. Here, we investigate the antibacterial activity of biogenic silver nanoparticles (Bio-AgNPs) synthesized by Fusarium oxysporum, used alone or in combination with polymyxin B against carbapenem-resistant A. baumannii. Methods and results In this study, ATCC® 19606™ strain and four carbapenem-resistant A. baumannii strains were used. The antibacterial activity of Bio-AgNPs and its synergism with polymyxin B were determined using broth microdilution, checkboard methods and time-kill assays. The integrity of the bacterial cell membrane was monitored by protein leakage assay. In addition, the cytotoxicity in the VERO mammalian cell line was also evaluated, and the selectivity index was calculated. Bio-AgNPs have an antibacterial activity with MIC and MBC ranging from 0.460 to 1.870 µg/ml. The combination of polymyxin B and Bio-AgNPs presents synergy against four of the five strains tested and additivity against one strain in the checkerboard assay. Considering the time of cell death, Bio-AgNPs killed all carbapenem-resistant isolates and ATCC® 19606™ within 1 h. When combined, Bio-AgNPs presented 16-fold reduction of the polymyxin B MIC and showed a decrease in terms of viable A. baumannii cells in 4 h of treatment, with synergic and additive effects. Protein leakage was observed with increasing concentrations for Bio-AgNPs treatments. Additionally, Bio-AgNP and polymyxin B showed dose-dependent cytotoxicity against mammalian VERO cells and combined the cytotoxicity which was significantly reduced and presented a greater pharmacological safety. Conclusions The results presented here indicate that Bio-AgNPs in combination with polymyxin B could represent a good alternative in the treatment of carbapenem-resistant A. baumannii. Significance and impact of study This study demonstrates the synergic effect between Bio-AgNPs and polymyxin B on carbapenem-resistant A. baumannii strains.

Background Acanthamoeba keratitis (AK) is an important cause of ocular morbidity in both contact lens wearers and non wearers. Medical management comprises prolonged empiric treatment with multiple drugs, leading to adverse effects and suboptimal cure. The present study evaluated the efficiency and safety of common antimicrobial agents used in treatment of AK. Methods Six Acanthamoeba isolates (four AK, two water samples) were axenized and subjected to in vitro susceptibility testing against chlorhexidine, pentamidine isethionate, polymyxin B, miltefosine, and fluconazole to check for trophocidal and cysticidal activity. The safety profile was analysed by observing the cytotoxicity of the highest cidal concentration toward human corneal epithelial cell (HCEC) line. Results Chlorhexidine had the lowest cidal concentration against both cysts and trophozoites (range 4.16-25 μg/ml) followed by pentamidine isethionate (range 25-166.7 μg/ml). Both agents were nontoxic to HCEC. Polymyxin B (range 25-200 μg/ml) and fluconazole (range 64-512 μg/ml) had relatively higher minimum inhibitory concentrations (MIC); fluconazole was nontoxic even at 1024 μg/ml, but cytotoxicity was observed at 400 μg/ml with polymyxin B. Miltefosine was not effective against cysts at tested concentrations. A. castellanii were more susceptible to all agents (except pentamidine isethionate) than A. lenticulata. Clinical isolates were less susceptible to polymyxin B and fluconazole than environmental isolates, reverse was true for miltefosine. Conclusion Chlorhexidine and pentamidine isethionate were the most effective and safe agents against both trophozoites and cysts forms of our Acanthamoeba isolates. Fluconazole had higher MIC but was nontoxic. Polymyxin B was effective at high MIC but therapeutic dose was found toxic. Miltefosine, at tested concentrations, could not inhibit cysts of Acanthamoeba. Clinical isolates had higher MICs for polymyxin B and fluconazole.

AIMS Data regarding clinical pharmacokinetic/toxicodynamic (PK/TD) of polymyxin B is short of direct quantitative data. This study aims to investigate the risk factors of polymyxin B associated acute kidney injury (AKI) and to assess the relationship between polymyxin B plasma levels and its nephrotoxicity. METHODS A retrospective study was performed in adult patients treated with polymyxin B. Risk factors associated with AKI and plasma trough concentrations of polymyxin B were identified via medical record review. A multivariate logistic regression model was established and the risk of polymyxin B-associated AKI were predicted by a receiver operating characteristic curve, with maximal Youden index used to identify safety thresholds among the study population. RESULTS Fifty-four adult patients were included in the study. AKI was detected in 14 patients during polymyxin B treatment (25.9%, 14 out of 54). Cmin (odds ratio [OR] 2.071; 95% confidence interval [CI] 1.235-3.472) and baseline serum creatinine (OR 1.024; 95% CI 1.005-1.043) were significant independent risk factors for developing AKI. The area under the ROC curve of the combined predictor was larger based on the above factors. When the Youden index was at maximum, the optimal cut-off point was 6.678 of the ROC curve. When Cmin ≥ 3.13 mg/L, the probability of AKI was more than 50%. CONCLUSION In this study, when the calculated combined predictor value was >6.678, there was an increased risk of AKI. Maintaining a polymyxin B Cmin level below 3.13 mg/L may be helpful in reducing the incidence of polymyxin B associated nephrotoxicity.

The mortality of septic shock remains high [Ann Intensive Care. 2017;7:19], so apart from usual therapy based on source control and antibiotics, some patients may need rescue therapies. Blood purification systems may play a role by facilitating the nonspecific removal of inflammatory mediators and microbiological toxins. There are different hemoadsorption systems, we describe in this case report the sequential use of Polymyxin B (PMX) endotoxin-adsorbing column (Toraymixin PMX-20R; Toray, Tokyo, Japan) and Cytosorb® (Cytosorbents Corp., New Jersey, USA).

Graphical abstract Coronavirus disease (COVID-19) is an emerging pandemic that threatens the world since the early days of 2020. Development of vaccines or new drugs against COVID-19 comprises several stages of investigation including efficacy, safety, and approval studies. A shortcut to this delicate pathway is computational-based analysis of FDA-approved drugs against assigned molecular targets of the coronavirus. In this study, we virtually screened a library of FDA-approved drugs prescribed for different therapeutic purposes against versatile COVID-19 specific proteins which are crucial for the virus life cycle. Three antibiotics in our screening polymyxin B, bafilomycin A, and rifampicin show motivating binding stability with more than one target of the virus. Another category of tested drugs is oral antiseptics of mouth rinsing solutions that unexpectedly exhibited significant affinity to the target proteins employed by the virus for attachment and cell internalization. Other OTC drugs widely used and tested in our study are heartburn drugs and they show no significant binding. We tested also some other drugs falling under the scope of investigation regarding interference with a degree of severity of COVID-19 like angiotensin II blockers used as antihypertensive, and our study suggests a therapeutic rather than predisposing effect of these drugs against COVID-19.

Resumen Introducción: La polimixina B se ha aplicado como uno de los antibióticos de último recurso para el tratamiento de la multirresistencia entre las infecciones bacterianas Gram negativas. Debido a efectos secundarios como toxicidad renal, el uso de polimixina se asocia con limitaciones. El presente estudio evalúa la actividad antibacteriana in vitro de varios productos comerciales de polimixina B contra Pseudomonas aeruginosa. Métodos: Este estudio incluyó 63 aislados de P. aeruginosa no duplicados que se examinaron para la prueba de susceptibilidad in vitro a la polimixina B utilizando los siguientes discos de polvo: sulfato de polimixina B, otosporina, Poly-Mxb y Myxacort. También se han identificado las MIC50 y MIC90 para los antibióticos de polimixina B. Resultados: Myxacort tuvo una actividad funcional contra la mayoría de los aislados de P. aeruginosa, y sólo siete aislados tuvieron una CIM relativamente alta. Las actividades de Poly-MXb y Myxacort fueron las mismas que las de otosporina. Conclusiones: Nuestros resultados revelaron que el producto genérico nacional de polimixina B (Myxacort), y dos productos externos (Otosporin, Poly-MXb) son similares en términos de actividad microbiológica.

Polymyxins were used for the management of gram-negative infections in clinical practice science1940s. Parenteral administration waned in the seventies owing to polymyxins nephrotoxicity and neurotoxicity. Because of the lack of treatment choices for MDR and/or XDRgram negative superbugs as well as Acinetobacter baumannii, Klebsiella pneumonia, and Pseudomonas aeruginosa, there is a growing need for effective prescribing of old antibiotics that are still effective. However, understanding of polymyxins pharmacokinetics (PK) was restricted and clinical experience is limited which leads to a lack of widespread availability of up-to-date dosing guidelines that could potentially result in the incorrect use of these “last resort” antibiotics. Recently, polymyxin B resistant strains are also a reason of concern. In this review, we discuss the importance of preserving the effectiveness of polymyxins for nosocomial gram-negative infections and strategies to improve polymyxins’ prescription. We recommend that polymyxins should only be used to manage significant MDR and/or XDRgram-negative infections, in optimum doses and if possible, in combination therapy

Several population pharmacokinetics (popPK) models for polymyxin B have been constructed to optimize therapeutic regimens. However, their predictive performance remains unclear when extrapolated to different clinical centers. Therefore, this study aimed to evaluate the predictive ability of polymyxin B popPK models. A literature search was conducted, and the predictive performance was determined for each selected model using an independent dataset of 20 patients (92 concentrations) from the Third Xiangya Hospital. Prediction- and simulation-based diagnostics were used to evaluate model predictability. The influence of prior information was assessed using Bayesian forecasting. Eight published studies were evaluated. In prediction-based diagnostics, the prediction error within ± 30% was over 50% in two models. In simulation-based diagnostics, the prediction- and variability-corrected visual predictive check (pvcVPC) showed satisfactory predictivity in three models, while the normalized prediction distribution error (NPDE) tests indicated model misspecification in all models. Bayesian forecasting demonstrated a substantially improvement in the model predictability even with one prior observation. Not all published models were satisfactory in prediction- and simulation-based diagnostics; however, Bayesian forecasting improved the predictability considerably with priors, which can be applied to guide polymyxin B dosing recommendations and adjustments for clinicians.

Background: Tuberculosis (TB) sputum culture contaminants make it difficult to obtain pure TB isolates.We aimed to study and identify persistent TB sputum culture contaminants post the standard laboratory pre-culture sample decontamination techniques. Methods: This was a longitudinal study of TB sputum culture contamination for a cohort of TB patients on standard treatment at: baseline, during TB treatment and post TB treatment. Sputum samples were decontaminated with 1.5%NaOH and neutralized using 6.8 Phosphate buffer solution.Sputum was then inoculated into MGIT (mycobactrial growth indicator tube) supplemented with 0.8ml PANTA. A drop of each positive MGIT culture was sub cultured onto blood agar and incu- bated for 48 hours at 35 -37OC.Any growth was identified using growth characteristics and colony morphology. Results: From October 2017 through May 2019;we collected 8645 sputum samples of which 8624(99.8%) were eligible and inoculated into MGIT where 2444(28.3%)samples were TB culture positive and 255(10.4%)were positive for contam- inants:237 none-tuberculosis bacteria, 12 fungi and 6 mixed(none-tuberculous bacteria+fungi).There was no statistically significant difference between none tuberculosis bacteria and fungi in the treatment (OR=1.4,95%CI:0.26–7.47,p=0.690) and the post treatment TB phases(OR=2.02,95%CI:0.38–10.79,p=0.411)Vs baseline. Conclusion: None-tuberculous bacteria and fungi dominate the plethora of TB sputum culture contamination and persist beyond the standard laboratory pre-culture decontamination algorithm. Keywords: Bacteria; Fungi; Inoculation; PANTA (Polymyxin B; Amphotericin B; Nalidixic acid; Trimethoprim; Azlocillin).

Acquiring an understanding of the mechanisms underlying antimicrobial action is important for overcoming bacterial resistance to antimicrobials. This study evaluated three different methods (antimicrobial fixed broth dilution method, metabolic inhibitors fixed broth dilution method, and metabolic inhibitor fixed agar recovery method) for determining the target site of Escherichia coli O157:H7 by treatments with various antimicrobials (ethanol, ethylenediaminetetraacetic acid, polymyxin B, thymol, acetic acid, and citrus fruit extract). However, the results indicated only weak relationships between MIC values and mechanisms of antimicrobials known to cause damage or injury. In addition, the results of three measurement methods using metabolic inhibitors were not correlated. These results suggest that measurement methods using metabolic inhibitors alone may not be suitable for determining the target site injured by antimicrobials. Therefore, various measurement methods should be compared and analyzed to determine the damage or injury sites targeted by antimicrobials in pathogenic bacteria. Further studies are needed to compare and analyze the various measurement methods for determining the target site injured by antimicrobials in pathogenic bacteria

The complex reservoir of metabolite-producing bacteria in the gastrointestinal tract contributes tremendously to human health and disease. Bacterial composition, and by extension gut metabolomic composition, is undoubtably influenced by the use of modern antibiotics. Herein, we demonstrate that polymyxin B, a last resort antibiotic, influences the production of the genotoxic metabolite colibactin from adherent-invasive Escherichia coli (AIEC) NC101. Colibactin can promote colorectal cancer through DNA double stranded breaks and interstrand cross-links. While the structure and biosynthesis of colibactin have been elucidated, chemical-induced regulation of its biosynthetic gene cluster and subsequent production of the genotoxin by E. coli are largely unexplored. Using a multiomic approach, we identified that polymyxin B stress enhances the abundance of colibactin biosynthesis proteins (Clb's) in multiple pks+ E. coli strains, including pro-carcinogenic AIEC, NC101; the probiotic strain, Nissle 1917; and the antibiotic testing strain, ATCC 25922. Expression analysis via qPCR revealed that increased transcription of clb genes likely contributes to elevated Clb protein levels in NC101. Enhanced production of Clb's by NC101 under polymyxin stress matched an increased production of the colibactin prodrug motif, a proxy for the mature genotoxic metabolite. Furthermore, E. coli with a heightened tolerance for polymyxin induced greater mammalian DNA damage, assessed by quantification of γH2AX staining in cultured intestinal epithelial cells. This study establishes a key link between the polymyxin B stress response and colibactin production in pks+ E. coli. Ultimately, our findings will inform future studies investigating colibactin regulation and the ability of seemingly innocuous commensal microbes to induce host disease.

Polymyxin B and colistin (polymyxin E) are increasingly used as the last line of therapy for infections caused by multidrug-resistant (MDR) gram-negative pathogens. However, nephrotoxicity is still...

Background Pseudomonas aeruginosa (P. aeruginosa) is an uncommon but fatal causative pathogen for community-acquired pneumonia (CAP). Few case reports described the previously healthy individuals with CAP caused by P. aeruginosa. Case Presentation A 67-year-old male farmer was referred to our hospital with a 6-day history of fever and shortness of breath. The radiologic findings revealed a dense consolidation site in the right lung, considering infection lesion, accompanying with mediastinal and right hilar lymphadenopathy. Sputum sample results showed P. aeruginosa and multidrug-resistant Acinetobacter baumannii. The combination of polymyxin B and amikacin was given to him based on the lab results, the manifestations of the patient were alleviated and he returned to his home after a 35-day hospitalization. Conclusion We need to keep close attention to community-acquired P. aeruginosa pneumonia due to its high mortality, further studies are needed to identify the infectious source, effective examination, and optimal therapy including medications and duration.

Infections by carbapenem-resistant Klebsiella pneumoniae (CRKp) are an increasing global threat with limited therapeutic options. Our objective was to evaluate clinical and microbiological outcomes of patients treated with amikacin for CRKp infections. We did a retrospective cohort of patients > 18 years old, with CRKp infections treated with amikacin in two tertiary care hospitals in Porto Alegre, Brazil. The impact of clinical factors, antibiotic treatment, and amikacin minimum inhibitory concentration (MIC) on patients’ 30-day mortality was assessed. Microbiological clearance and nephrotoxicity (assessed by RIFLE score) were evaluated as secondary outcomes. A Cox regression analysis was done for mortality. We included 84 patients for analysis. Twenty-nine (34.5%) patients died in 30 days. Amikacin MIC values ranged from 0.125 to 8 μg/mL and did not influence on mortality, regardless of the prescribed dose of this antibiotic (P = 0.24). Bacterial clearance occurred in 17 (58.6%) of 29 patients who collected subsequent cultures. Two (16.6%) of the 12 persistently positive cultures changed the amikacin susceptibility profile from susceptible to intermediate. Twenty-nine (37.2%) patients developed acute kidney injury (AKI): risk 13, injury 11, and failure 5. Risk factors for AKI were higher baseline eGFR (P

Summary. The aim of the study was to present an argument for treatment algorithm of patients with extremity gunshot injuries complicated by suppurative inflammation. Materials and research methods. Examination and treatment of 163 patients with gunshot wounds of the extremities were performed. All the wounded were divided into 3 study groups. The patients of group 1 underwent conventional treatment of gunshot wounds. In group 2, negative pressure wound therapy was used. Wounded patients of group 3 received vacuum-assisted therapy supplemented by the proposed scheme of counter-drainage and flow-through flushing irrigation of wounds with antiseptic solutions of 0.02 % decamethoxine and 3 % hydrogen peroxide. Bacteriological study of wound exudate was carried out, and sensitivity of microorganisms to antibiotics was determined. Results and its discussion. Wound microbiology analysis in victims of blast and mine-blast injuries demonstrated predominance of gram-negative bacteria in wound microbiocenosis — Acinetobacter spp. (53 % of cases) and Pseudomonas spp. (15 % of cases). Gram-positive cocci were isolated in 22.2 % of cases. Sensitivity study of nonfermentative gram-negative rods demonstrated them to have high level of resistance to most antibacterial agents. All strains of Acinetobacter and Pseudomonas spp. were sensitive to polymyxin B and colistin but resistant to inhibitor-protected and -unprotected amino penicillin. Beneficial effect of vacuum therapy in patients of groups 2 and 3 was evidenced by significantly reduced time of wound healing and hospital stay. The use of suggested mixture of antiseptics resulted in decrease of inflammation in 94.45 % and 88.89 % of patients in groups 3 and 2, respectively. Besides, in group 3, duration of hydration phase in wound healing process decreased to 5.7 days. The period of complete wound healing was shorter by 2.5 days, and hospital stay decreased from 14.97 to 10.8 days. Conclusions. Thus, predominance of gram-negative microorganisms in gunshot wounds as well as their high resistance to antibiotics should be considered when undertaking empirical antibiotic therapy in wounded patients. The proposed treatment algorithm involving negative pressure wound therapy supplemented with counter-drainage and flow-through flushing irrigation with a mixture of suggested antiseptics proved to be highly efficient in patients with extremity gunshot injuries complicated by suppurative inflammation.

Antimicrobial susceptibility testing with the last-resort antibiotics polymyxins (polymyxin B and colistin) is associated with several methodological issues. Currently, broth microdilution (BMD) is recommended for colistin and polymyxin B. BMD is laborious and the utility of alternative methods needs to be evaluated for polymyxin B susceptibility testing. In this study, using BMD as a reference method, the performance of agar dilution (AD) and MIC test strips (MTS) were evaluated in polymyxin B susceptibility testing. BMD, AD and MTS were used to determine MICs of 193 clinical isolates of Escherichia coli. Seventy-nine were positive for the polymyxin resistance gene mcr-1. Method performances were evaluated based on pair-wise agreements with the reference method (BMD) and statistical testing. AD and MTS showed an unacceptable number of very major errors (VMEs) compared with BMD, 9·3 and 10·7%, respectively. The essential agreement (EA) was low for AD (49·7%), but high for MTS (97·8%). However, statistical testing showed that MTS tended to yield a one-step lower MIC (P

Burn injuries represent a global public health concern. The guidelines for burn care mention that the treatment of burn injuries depends on the type of burn injury, depth of tissue, area of wounds, and site on the body. At present, several topical antimicrobial agents are used in the treatment of burn wounds as a first choice. This study aims to investigate the effectiveness of the compound polymyxin B topical agents for the treatment of burn wounds. PubMed, Web of Science, ProQuest, and China National Knowledge Infrastructure databases were searched for articles published until January 2021. The studies that conducted clinical trials comparing compound polymyxin B ointment with other treatment reagents for burn wound treatment were included. A total of three outcomes, which were investigator-assessed clinical response, including mortality, bacterial counts, efficacy and safety were included for analysis in this study. In total, 12 randomized controlled trials, 1 clinical trial, 2 prospective studies, and 1 retrospective study were extracted. The result of mortality showed no significant difference (risk ratio [RR]: 0.70, 95% CI: 0.21–2.31, P = .56); wound healing revealed an RR of 1.59 (95% CI: 1.40–1.81, P < .001); time to heal revealed a mean difference of −5.09 (95% CI: −6.31 to −3.86) days (P < .001); scar incidence was not significantly lower in the treatment group (RR: 0.70, 95% CI: 0.38–1.30, P = .26); and adverse event incidence was significantly lower in the treatment group (RR: 0.26, 95% CI: 0.09–0.72, P < .01). The compound polymyxin B ointment shows the effectiveness of increase in the wound healing and accelerates the time of healing with fewer adverse effects.

Background Carbapenem-resistant Enterobacter cloacae complex (CREC) is a new emerging threat to global public health. The objective of the study was to investigate the clinical characteristics and molecular epidemiology of CREC infections in the medical center of northeast China. Methods Twenty-nine patients were infected/colonized with CREC during a ten-year period (2010–2019) by WHONET analysis. Antibiotic susceptibilities were tested with VITEK 2 and micro broth dilution method (for polymyxin B and tigecycline). Carbapenemase encoding genes, β-lactamase genes, and seven housekeeping genes for MLST were amplified and sequenced for 18 cryopreserved CREC isolates. Maximum likelihood phylogenetic tree was built with the concentrated sequences to show the relatedness between the 18 isolates. Results There was a rapid increase in CREC detection rate during the ten-year period, reaching 8.11% in 2018 and 6.48% in 2019. The resistance rate of CREC isolates to imipenem and meropenem were 100.0 and 77.8%, however, they showed high sensitivity to tigecycline, polymyxin B and amikacin. The 30-day crude mortality of CREC infection was 17.4%, indicating that it may be a low-virulence bacterium. Furthermore, molecular epidemiology revealed that ST93 was the predominant sequence type followed by ST171 and ST145, with NDM-1 and NDM-5 as the main carbapenemase-encoding genes. Moreover, E. hormaechei subsp. steigerwaltii and E. hormaechei subsp. oharae were the main species, which showed different resistance patterns. Conclusion Rising detection rate of CREC was observed in a tertiary hospital, which showed heterogeneity in drug resistance patterns, resistance genes, and MLST types. Effective infection prevention and control measures should be taken to reduce the spread of CREC.

Peptide and protein therapeutics generally exhibit high potency and specificity and are increasingly important segments of the pharmaceutical market. However, their clinical applications are limited by rapid clearance and poor membrane permeability. Encapsulation of the peptide or protein into a nano-scale carrier can modify its pharmacokinetics and biodistribution. This might be employed to promote uptake in desired cell types or tissues, to limit systemic exposure, or to reduce the need for frequent injections. We have recently described inverse Flash NanoPrecipitation (iFNP), a scalable technique to encapsulate water-soluble therapeutics into polymeric nanocarriers, and have demonstrated improvements in therapeutic loading of an order of magnitude over comparable approaches. Here, we describe the formulation parameters that control release rates of encapsulated model therapeutics polymyxin B, lysozyme, and bovine serum albumin from nanocarriers produced using iFNP. Using a neutropenic lung infection mouse model with a multi-drug resistant Acinetobacter baumannii clinical isolate, we demonstrate enhanced therapeutic effect and safety profile afforded by nanocarrier-encapsulated polymyxin B following pulmonary administration. The encapsulated formulation reduced toxicity observed at elevated doses and resulted in up to 2.7-log10 reduction in bacterial burden below that of unencapsulated polymyxin B. These results establish the promise of iFNP as a platform for nanocarrier delivery of water-soluble therapeutics.

Endotoxin adsorption therapy by polymyxin B-immobilized fiber column direct hemoperfusion (PMX-DHP) has been used for the treatment of septic shock patients. Endotoxin, an outer membrane component of Gram-negative bacteria, plays an important role in the pathogenesis of septic shock. Endotoxin triggers a signaling cascade for leukocytes, macrophage, and endothelial cells to secrete various mediators including cytokines and nitric oxide, leading to septic shock and multiple organ dysfunction syndrome. PMX-DHP directly adsorbed not only endotoxin but also monocytes and anandamide. It reduced blood levels of inflammatory cytokines such as interleukin (IL)-1, IL-6, tumor necrosis factor-alpha and IL-17A, adhesion molecules, plasminogen activator inhibitor 1, and high mobility group box-1. As a result, PMX-DHP increased blood pressure and reduced the dose of vasoactive-inotropic agents. PMX-DHP improved monocyte human leukocyte antigen-DR expression in patients with severe sepsis and septic shock. A post hoc analysis of EUPHRATES (Evaluating the Use of Polymyxin B Hemoperfusion in Randomized Controlled Trial of Adults Treated for Endotoxemia and Septic Shock) trial has shown that PMX-DHP significantly reduced 28-day mortality compared with the control group in septic shock patients with endotoxin activity assay level between 0.60 and 0.89. Longer duration of PMX-DHP may be another strategy to bring out the beneficial effects of PMX-DHP. Further studies are needed to confirm the efficacy of PMX-DHP treatment for septic shock.

As a pathogenic toxin, endotoxins are the culprit for endotoxemia and can be generally removed from the blood by hemoperfusion. Reduced graphene oxide (rGO) is a promising endotoxin sorbent for hemoperfusion owing to its excellent adsorption capacity, but it has the side effect of nonspecific adsorption and low blood compatibility. Polymyxin B (PMB) acts as an organic affinity ligand that can specifically bind endotoxins. As a natural anticoagulant, heparin (Hep) can reduce the risk of coagulation and improve the blood compatibility of materials. Herein, an rGO bead adsorbent was prepared by coupling with PMB and Hep and used for endotoxin adsorption; in this, polydopamine (pDA) served as an active coating for immobilization of PMB and further coupling with Hep. The physicochemical characteristics indicated that PMB and Hep were successfully immobilized on rGO beads with a hierarchical pore structure. PMB endowed rGO beads with higher adsorption capacity (143.84 ± 3.28 EU/mg) and good adsorption selectivity for endotoxins. Hep significantly improved the blood compatibility of rGO beads. These modified rGO beads also achieved good adsorption capacity and adsorption selectivity for endotoxins in plasma, serum, or blood. Therefore, rGO/pDA/PMB/Hep beads are potential adsorbents for endotoxins in hemoperfusion.

Carbapenem-resistant Klebsiella pneumoniae has been classified as an Urgent Threat by the Centers for Disease Control and Prevention (CDC). The combination of two "old" antibiotics, polymyxin and chloramphenicol, displays synergistic killing against New Delhi metallo-β-lactamase (NDM)-producing K. pneumoniae. However, the mechanism(s) underpinning their synergistic killing are not well studied. We employed an in vitro pharmacokinetic/pharmacodynamic model to mimic the pharmacokinetics of the antibiotics in patients and examined bacterial killing against NDM-producing K. pneumoniae using a metabolomic approach. Metabolomic analysis was integrated with an isolate-specific genome-scale metabolic network (GSMN). Our results show that metabolic responses to polymyxin B and/or chloramphenicol against NDM-producing K. pneumoniae involved the inhibition of cell envelope biogenesis, metabolism of arginine and nucleotides, glycolysis, and pentose phosphate pathways. Our metabolomic and GSMN modeling results highlight the novel mechanisms of a synergistic antibiotic combination at the network level and may have a significant potential in developing precision antimicrobial chemotherapy in patients.

With the aim of tackling the increasingly serious antimicrobial resistance and improving the clinical potential of AMPs, a facile de novo strategy was adopted in this study, and a series of new peptides comprising repeating unit (WRX)n (X represents I, L, F, W, and K; n = 2, 3, 4, or 5) and amidation at C-terminus were designed. Most of the newly designed peptides exhibited a broad range of excellent antimicrobial activities against various bacteria, especially difficult-to-kill multidrug-resistant bacteria clinical isolates. Among (WRK)4 and (WRK)5, with n = 4 and n = 5 of repeating unit WRK, the highest selectivity for anionic bacterial membranes over a zwitterionic mammalian cell membrane is presented with strong antimicrobial potential and low toxicity. Additionally, both (WRK)4 and (WRK)5 emerged with fast killing speed and low tendency of resistance in sharp contrast to the conventional antibiotics ciprofloxacin, gentamicin, and imipenem, as well as having antimicrobial activity through multiple mechanisms including a membrane-disruptive mechanism and an intramolecular mechanism (nucleic acid leakage, DNA binding and ROS generation) characterized by a series of assays. Furthermore, (WRK)4 exerted impressive therapeutic effects in vivo similarly to polymyxin B but displayed much lower toxicity in vivo than polymyxin B. Taken together, the newly designed peptides (WRK)4 and (WRK)5 presented tremendous potential as novel antimicrobial candidates in response to the growing antimicrobial resistance.

Antibiotic resistance is a major global health challenge and, worryingly, several key Gram negative pathogens can become resistant to most currently available antibiotics. Polymyxins have been revived as a last-line therapeutic option for the treatment of infections caused by multidrug-resistant Gram negative bacteria, in particular Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacterales. Polymyxins were first discovered in the late 1940s but were abandoned soon after their approval in the late 1950s as a result of toxicities (e.g., nephrotoxicity) and the availability of "safer" antibiotics approved at that time. Therefore, knowledge on polymyxins had been scarce until recently, when enormous efforts have been made by several research teams around the world to elucidate the chemical, microbiological, pharmacokinetic/pharmacodynamic, and toxicological properties of polymyxins. One of the major achievements is the development of the first scientifically based dosage regimens for colistin that are crucial to ensure its safe and effective use in patients. Although the guideline has not been developed for polymyxin B, a large clinical trial is currently being conducted to optimize its clinical use. Importantly, several novel, safer polymyxin-like lipopeptides are developed to overcome the nephrotoxicity, poor efficacy against pulmonary infections, and narrow therapeutic windows of the currently used polymyxin B and colistin. This review discusses the latest achievements on polymyxins and highlights the major challenges ahead in optimizing their clinical use and discovering new-generation polymyxins. To save lives from the deadly infections caused by Gram negative "superbugs," every effort must be made to improve the clinical utility of the last-line polymyxins. SIGNIFICANCE STATEMENT: Antimicrobial resistance poses a significant threat to global health. The increasing prevalence of multidrug-resistant (MDR) bacterial infections has been highlighted by leading global health organizations and authorities. Polymyxins are a last-line defense against difficult-to-treat MDR Gram negative pathogens. Unfortunately, the pharmacological information on polymyxins was very limited until recently. This review provides a comprehensive overview on the major achievements and challenges in polymyxin pharmacology and clinical use and how the recent findings have been employed to improve clinical practice worldwide.

Background Polymyxins is a class of cyclic polypeptide antibiotics with strong antibacterial activity against Gram-negative bacteria. However, bacteria become resistant to Polymyxins. Thus, Polymyxin B (PMB) in combination with other antimicrobials may be a better choice in clinic. This study aimed to evaluate the synergistic bacteriostatic effect of PMB combined with Propofol medium and long chain fat emulsion injection against Escherichia coli in vitro. Methods The Minimal Inhibitory Concentration of Polymyxin B combined with Propofol medium and long chain fat emulsion injection and two drugs used alone against Escherichia coli were detected with the Kirby-Bauer disk diffusion (K-B) method, and the diameter of the inhibition zone was calculated to evaluate bacteriostatic effects. Results Different concentrations of PMB all had obvious bacteriostatic effects on Escherichia coli, while different concentrations of Propofol medium and long chain fat emulsion injection had no bacteriostatic effects on Escherichia coli. The bacteriostatic effect of the combination of PMB with Propofol medium and long chain fat emulsion injection against Escherichia coli was synergistic, and no effects of uncorrelated and antagonism were observed in this combination. Conclusions PMB combined with Propofol medium and long chain fat emulsion injection can improve the bacteriostatic effect for Escherichia coli in vitro.

Therapeutic options for infections caused by Carbapenem-resistant Enterobacterales (CRE) are restricted and include polymyxins-centred schemes. Evaluation of in vitro susceptibility is difficult and time consuming. Agar-based methodologies are an alternative to broth microdilution (BMD) and we aimed to evaluate the accuracy of those methods among Enterobacterales. A total of 137 non-duplicated CRE were subjected to polymyxin B BMD, agar screening test (Mueller Hinton plates containing 3 µg ml-1 of polymyxin B) and agar dilution (antibiotic serially diluted 0·25-64 µg ml-1 ). CRE of 42·3% were resistant to polymyxin B (MICs range: 0·25->64 µg ml-1 ) and 16·8% presented borderline MICs. Sensitivity, specificity, PPV and NPV were 86·2, 98·7, 98 and 90·7% for screening test and 86·2, 97·5, 96·1 and 90·6% for agar dilution. ME was 0·73 and 1·5% for screening and agar dilution respectively; VME was 5·8% for both techniques. In general, agar-based methods had a good performance. As far as we know, this is the first study to propose an agar screening test using polymyxin B instead of colistin.

Introduction: In December 2019, an outbreak of pneumonia caused by a novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) quickly spread and the corona virus disease 2019 (COVID-19) became a pandemic. We report on a 54-year-old patient with SARS-CoV-2 infection suffering from septic shock due to nosocomial infection and pulmonary derangement caused by SARS-CoV-2. The patient was treated with polymyxin B hemoperfusion (PMX-HP), a blood purification therapy against septic shock, followed by continuous low flow extracorporeal CO2 removal therapy. Case Report: A 54-year-old man was hospitalized for coronavirus disease 2019 (COVID-19). Chest computed tomography (CCT) showed extensive non-segmental ground glass opacity. Despite the initiation of standard therapy, respiratory failure progressed. After two days of polymyxin B hemoperfusion therapy (PMX-HP) with adjunctive corticosteroid for multi-resistant Gram-negative infection (Acinetobacter) the patient’s condition improved. In rapidly progressive COVID-19 cases with secondary infection, the early use of PMX-HP may avoid the need for mechanical ventilation by suppressing local inflammation of the lung. Conclusion: The concern of life-threatening bacterial infections in critically ill COVID-19 patients due to antibiotics resistance is high. Secondary bacterial infections may develop during or following COVID-19 infection. The use of PMX-HP in septic shock patients has resulted in decreased dependency on ventilators, which is a serious issue during this COVID-19 pandemic. Combined and less invasive approaches might be considered in COVID-19 patients with multiple organ failure (MOF).

Mounting antimicrobial resistance to carbapenemase-producing Klebsiella pneumoniae (CPKP) highlights the need to optimize currently available treatment options. The objective of this study was to explore alternative dosing strategies that limit the emergence of resistance to preserve the utility of last-line antibiotics by: (i) evaluating the pharmacodynamic (PD) killing activity of simulated humanized exposures to monotherapy and two-drug and three-drug combinations against CPKP bacterial isolates with different resistance mechanisms; and (ii) optimizing polymyxin B (PMB) exposure simulated in the three-drug combination regimens to maximize the killing activity. Two CPKP clinical isolates (BAA2146 (NDM-1) and BRKP76 (KPC-2)) were evaluated over 168 hours using a hollow-fiber infection model simulating clinically relevant PMB, fosfomycin, and meropenem dosing regimens. PMB-based three-drug combinations were further optimized by varying the initial exposure (0-24 hours) or maintenance dose received over the duration of treatment. The area under the bacterial load-versus-time curve (AUCFU) was used to determine PD activity. Overall reductions in PMB exposure ranged from 2 to 84%. BAA2146 and BRKP76 had median (range) AUCFUs of 11.0 (10.6-11.6) log10 CFU hour/mL and 7.08 (7.04-11.9) log10 CFU hour/mL, respectively. The PMB "front loaded" 2.5 mg/kg/day + 0.5 mg/kg maintenance dose in combination with meropenem and fosfomycin was a promising regimen against BRKP76, with an overall reduction in PMB exposure of 56% while still eradicating the bacteria. Tailored triple-combination therapy allows for the optimization of dose and treatment duration of last-line agents like PMB to achieve adequate drug exposure and appropriate PD activity while minimizing the emergence of resistance.

Aim: Whole dead tumor cells can be used as antigen source and the induction of protective immune response could be enhanced by damage-associated molecular patterns. Materials & methods: We generated whole dead tumor cells called B16-immunogenic cell bodies (ICBs) from B16 melanoma cells by nutrient starvation and evaluated the in vivo antitumor effect of B16-ICBs plus ATP and polymyxin B (PMB). Results: The subcutaneous immunization with B16-ICBs + PMB + ATP a 50% of tumor-free animals and induced a significant delay in tumor growth in a prophylactic approach. These results correlated with maturation of bone marrow-derived dendritic cells and activation of T CD8+lymphocytes in vitro. Conclusion: Altogether, ICB + ATP + PMB is efficient in inducing the antitumor efficacy of the whole dead tumor cells vaccine.

Background The existence of multidrug-resistant organisms, including extended-spectrum beta-lactamases (ESBLs), is on rise across the globe and is becoming a severe problem. Knowledge of the prevalence and antibiogram profile of such isolates is essential to develop an appropriate treatment methodology. This study aimed to study the prevalence of Gram-negative isolates exhibiting ESBL at a tertiary care hospital and study their antibiogram profile. Methods A cross-sectional study was conducted at Shahid Gangalal National Heart Centre, Kathmandu, Nepal, from June 2018 to November 2018. A total of 770 clinical samples were collected and identified using the conventional biochemical tests following the Clinical and Laboratory Standard Institute (CLSI) guidelines. Antimicrobial susceptibility testing (AST) was performed using the standardized Kirby-Bauer disk diffusion method. The screening test for ESBL producers was performed as recommended by the CLSI and the confirmatory test was performed phenotypically using the E-test. Results Out of the 92 isolates, 84 (91.3%) were multidrug-resistant, and 47 (51.1%) were found to be potential ESBL producers. Of these, 16 isolates were confirmed ESBL producers by the E-test. Escherichia coli and Klebsiella pneumoniae were the predominant isolates and were also the major ESBL producers. Besides polymyxin B (100% sensitive), meropenem and imipenem showed high efficacy against the ESBL producers. Conclusion Multidrug resistance was very high; however, ESBL production was low. Polymyxin B and carbapenems are the choice of drugs against ESBL producers but should be used only as the last line drugs.

Aims: Polymyxin B (PMB) is known to require reactive oxygen species (ROS) for its bactericidal activity, but the mechanism of PMB resistance in various Pseudomonas aeruginosa strains has been poorl...

Antivirulence therapy by cell membrane coated nanoparticles has shown promise against bacterial infections. However, current approaches remain unsatisfactory when facing Escherichia coli (E. coli) infections, since the E. coli secretes multiple bacterial toxins including endotoxins and exotoxins that are challenging to eliminate simultaneously. What is worse, the absorptive scavengers normally rely on random contact of the diffuse toxins, which is not efficient. For the current cell membrane coated platform, the single type of cell membrane cannot fully meet the detoxing requirement facing multiple toxins. To address these problems, a polymyxin B (PMB)-modified, red blood cell (RBC)-mimetic hybrid liposome (P-RL) was developed. The P-RL was fabricated succinctly through fusion of PMB-modified lipids and the RBC membranes. By the strong interaction between PMB and the E. coli membrane, P-RL could attach and anchor to the E. coli; attributed to the fused RBC membrane and modified PMB, the P-RL could then efficiently neutralize both endotoxins and exotoxins from the toxin fountainhead. In vitro and in vivo results demonstrated the P-RL had a significant anchoring effect to E. coli. Moreover, compared with the existing RBC vesicles or PMB-modified liposomes, P-RL exhibited a superior therapeutic effect against RBC hemolysis, macrophage activation, and a mixed-toxin infection in mice. Potently, P-RL could inhibit E. coli O157:H7-induced skin damage, intestinal infection, and mouse death. Overall, the P-RL could potentially improve the detoxing efficiency and markedly expand the detoxification spectrum of current antivirulence systems, which provides different insights into drug-resistant E. coli treatment.

Pseudomonas aeruginosa is a difficult-to-treat Gram-negative bacterial pathogen causing life-threatening infections. Adaptive resistance (AR) to cationic peptide antibiotics such as polymyxin B impairs the therapeutic success. This self-protection is mediated by two component systems (TCSs) consisting of a membrane-bound histidine kinase and an intracellular response regulator (RR). As phosphorylation of the key RR aspartate residue is transient during signaling and hydrolytically unstable, the study of these systems is challenging. Here, we apply a tailored reverse polarity chemical proteomic strategy to capture this transient modification and read-out RR phosphorylation in complex proteomes using a nucleophilic probe. In-depth mechanistic insights into an ideal trapping strategy were performed with a recombinant RR demonstrating the importance of fine-tuned acidic pH values to facilitate the attack on the aspartate carbonyl C-atom and prevent unproductive hydrolysis. Analysis of Bacillus subtilis and P. aeruginosa proteomes revealed the detection of multiple annotated phosphoaspartate (pAsp) sites of known RRs in addition to many new potential pAsp sites. With this validated strategy we dissected the signaling of dynorphin A, a human peptide stress hormone, which is sensed by P. aeruginosa to prepare AR. Intriguingly, our methodology identified CprR as an unprecedented RR in dynorphin A interkingdom signaling., Phosphoaspartate (pAsp) is a labile posttranslational modification involved in bacterial signaling. To monitor pAsp we designed a chemical proteomics method and revealed insights into the antimicrobial response triggered by a human peptide hormone.

Objectives Polymyxin B is a last-line antibiotic for multidrug-resistant gram-negative bacterial infections. However, limited safety and pharmacokinetic information is available. We investigated the safety and pharmacokinetics of intravenous polymyxin B in healthy subjects. Methods An open-label, single-dose clinical trial was conducted in healthy Chinese subjects. Polymyxin B (sulphate) was administered intravenously at 0.75 or 1.5 mg/kg (n = 10 per dose, 5 males and 5 females) to examine the safety and pharmacokinetics. Results One female subject in the 1.5-mg/kg group discontinued due to abdominal pain during administration. The most frequently reported adverse events were perioral paraesthesia, dizziness, and numbness of extremities (7/10 subjects in the 0.75-mg/kg group, all subjects in the 1.5-mg/kg group). All neurotoxicity-related events dissipated without treatment within a maximum of 23 h. Notably, abdominal pain (3/5) and vulvar pruritus (2/5), colpitis (2/5) or abnormal uterine bleeding (1/5) were reported in female subjects receiving the 1.5-mg/kg dose. In the 0.75-mg/kg group, the total clearance, volume of distribution and half-life of polymyxin B were 0.028±0.002 L/h/kg, 0.219±0.023 L/kg and 5.44±0.741 h, respectively; similar values were observed in the 1.5-mg/kg group. Urinary recovery was 3.7 ± 1.1% and 8.1 ± 1.3% in the 0.75- and 1.5-mg/kg groups, respectively. Population pharmacokinetics of polymyxin B was consistent with a three-compartment model. The clearance and distribution of the central compartment were 0.027 L/h/kg and 0.071 L/kg, respectively. Conclusions This study is the first to examine the safety and pharmacokinetics of polymyxin B in healthy subjects. Our results highlight that acute toxicity is a dose-limiting factor for intravenous polymyxin B.

Objectives The objective of this review was to compare the effectiveness of Colistin monotherapy and combination therapy for the treatment of multidrug-resistant gram-negative bacterial infections. Data sources PubMed, Cochrane Library. Study eligibility interventions and exclusions In this systematic review, we included all retrospective and prospective studies and randomized controlled trials (RCTs) that compared intravenous polymyxin monotherapy and combination therapy with any other antibiotic for treating multidrug-resistant infections. Studies using inhaled polymyxins with 5 or less than 5 patients were excluded. The primary outcome was 30-day all-cause mortality and if not reported at day 30 we extracted and documented the closest time point. Both crude outcome rates and adjusted effect estimates were extracted for mortality. Study appraisal data extraction and synthesis Search string used was "(Colistin OR polymyxin) AND (Enterobacteriaceae OR Klebsiella OR Acinetobacter OR Escherichia coli OR Pseudomonas) AND (random OR prospective OR retrospective OR cohort OR observational OR blind)." Thirty-nine studies were included in our analysis; out of which 6 RCTs were included and 9 studies used carbapenem as the adjunctive antibiotic. Each study was screened and reviewed for eligibility independently by two authors and data extrapolated on an Excel sheet. Results The meta-analysis of polymyxin monotherapy vs. combination therapy in multidrug-resistant infections yielded an odds ratio (OR) of 0.81 (95% confidence interval [CI]: 0.65-1.01) with minimal heterogeneity (I 2 = 40%), whereas pooled analysis of this comparison in studies that included carbapenem as combination therapy yielded an OR of 0.64 (CI: 0.40-1.03; I 2 = 62%). Likewise, the pooled analysis of the RCTs yielded an OR of 0.82 (95% CI: 0.58-1.16, I 2 = 22%). All these showed no statistical significance. However, it was seen that polymyxin combination therapy was more effective in multidrug-resistant infections compared to polymyxin monotherapy. The effectiveness was more glaring when carbapenems were used as the combination drug instead of any other antibiotic and more so in many in vitro studies that used polymyxin combination therapy. Conclusion Although statistically insignificant, it would be prudent to use polymyxin combination therapy to treat multidrug-resistant gram-negative bacilli (GNB) infection over monotherapy with preference to use carbapenem as the adjunct alongside polymyxins. How to cite this article Samal S, Mishra SB, Patra SK, Rath A, Dash A, Nayak B, et al. Polymyxin Monotherapy vs. Combination Therapy for the Treatment of Multidrug-resistant Infections: A Systematic Review and Meta-analysis. Indian J Crit Care Med 2021;25(2):199-206.