Cost-effectiveness analysis of polymyxin B versus colistin for treating patients with carbapenem-resistant gram-negative bacterial infections.

The prevalence of carbapenem-resistant gram-negative bacterial (CRGNB) infection is continuously increasing, and polymyxin B and colistin are considered last-resort drugs. This study compared the cost-effectiveness of polymyxin B with that of colistin for the treatment of intensive care unit patients with CRGNB infection from the Chinese healthcare perspective. A decision-analytic Markov model was constructed to assess the cost-effectiveness of polymyxin B compared with colistin over a period of 5 years using evidence from phase trials and other publicly available studies. The model was developed in Treeage Pro 2022 and comprises a decision tree depicting initial hospitalization and a Markov model with four states projecting long-term health and economic impacts following discharge. Uncertainty was tested with one-way sensitivity analyses and probabilistic sensitivity analyses. The quality-adjusted life years (QALYs), direct medical costs, and incremental cost-effectiveness ratio (ICER) were estimated at willingness-to-pay (WTP) thresholds of $12,674 to $38,024 per QALY. According to the base analyses, the cost incurred by patients receiving colistin treatment was $12,244.77, leading to a gain of 1.35 QALYs. In contrast, patients treated with polymyxin B had a lower cost of $7,306.71 but yielded 1.07 QALYs. The ICRE of colistin was $18032.25/QALY. At a $12,674/QALY threshold, the results were sensitive to several variables, including the probability of cure with polymyxin B, the cost of drugs, the utility of discharge to home, the utility of discharge to long-term care, and the cost of nephrotoxicity with renal replacement therapy. After all model inputs varied across a wide range of reasonable values, only the probability of being cured with polymyxin B resulted in an ICER above the $38,024/QALY threshold. According to the probabilistic sensitivity analyses, colistin was the optimal strategy in 38.2% and 62.8% of the simulations, at $12,674/QALY and $38,024/QALY, respectively. Our study findings suggest that, when considering the Chinese healthcare perspective, colistin is likely to be more cost-effective than polymyxin B for patients with CRGNB infection, especially when the WTP threshold is set at one-time the per capita GDP. However, as the WTP threshold increases from one to three times the per capita GDP, the cost-effectiveness acceptability of colistin improves, increasing from 38.2 to 62.8%.

Innovative Microencapsulation of Polymyxin B for Enhanced Antimicrobial Efficacy via Coated Spray Drying.

This study aims to develop an innovative microencapsulation method for coated Polymyxin B, utilizing various polysaccharides such as hydroxypropyl ß-cyclodextrin, alginate, and chitosan, implemented through a three-fluid nozzle (3FN) spray drying process. High-performance liquid chromatography (HPLC) analysis revealed that formulations with a high ratio of sugar cage, hydroxypropyl ß-cyclodextrin (HPßCD), and sodium alginate (coded as ALGHCDHPLPM) resulted in a notable 16-fold increase in Polymyxin B recovery compared to chitosan microparticles. Morphological assessments using fluorescence labeling confirmed successful microparticle formation with core/shell structures. Alginate-based formulations exhibited distinct layers, while chitosan formulations showed uniform fluorescence throughout the microparticles. Focused beam reflectance and histograms from fluorescence microscopic measurements provided insights into physical size analysis, indicating consistent sizes of 6.8 ± 1.2 µm. Fourier-transform infrared (FTIR) spectra unveiled hydrogen bonding between Polymyxin B and other components within the microparticle structures. The drug release study showed sodium alginate's sustained release capability, reaching 26 ± 3% compared to 94 ± 3% from the free solution at the 24 h time point. Furthermore, the antimicrobial properties of the prepared microparticles against two Gram-negative bacteria, Escherichia coli and Pseudomonas aeruginosa, were investigated. The influence of various key excipients on the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values was evaluated. Results demonstrated effective bactericidal effects of ALGHCDHPLPM against both E. coli and P. aeruginosa. Additionally, the antibiofilm assay highlighted the potential efficacy of ALGHCDHPLPM against the biofilm viability of E. coli and P. aeruginosa, with concentrations ranging from 3.9 to 500 µg/m. This signifies a significant advancement in antimicrobial drug delivery systems, promising improved precision and efficacy in combating bacterial infections.

Potentially effective antimicrobial treatment for pneumonia caused by isolates of carbapenem-resistant and extensively drug-resistant Acinetobacter baumannii complex species: what can we expect in the future?

INTRODUCTION: Acinetobacter baumannii complex (Abc) is currently a significant cause of difficult-to-treat pneumonia. Due to the high prevalence rates of carbapenem- and extensively drug-resistant (CR, XDR) phenotypes, limited antibiotic options are available for the effective treatment of pneumonia caused by CR/XDR-Abc. AREAS COVERED: In vitro susceptibility data, relevant pharmacokinetic profiles (especially the penetration ratios from plasma into epithelial-lining fluid), and pharmacodynamic indices of key antibiotics against CR/XDR-Abc are reviewed. EXPERT OPINION: Doubling the routine intravenous maintenance dosages of conventional tigecycline (100 mg every 12 h) and minocycline (200 mg every 12 h) might be recommended for the effective treatment of pneumonia caused by CR/XDR-Abc. Nebulized polymyxin E, novel parenteral rifabutin BV100, and new polymyxin derivatives (SPR206, MRX-8, and QPX9003) could be considered supplementary combination options with other antibiotic classes. Regarding other novel antibiotics, the potency of sulbactam-durlobactam (1 g/1 g infused over 3 h every 6 h intravenously) combined with imipenem-cilastatin, and the ß-lactamase inhibitor xeruborbactam, is promising. Continuous infusion of full-dose cefiderocol is likely an effective treatment regimen for CR/XDR-Abc pneumonia. Zosurabalpin exhibits potent anti-CR/XDR-Abc activity in vitro, but its practical use in clinical therapy remains to be evaluated. The clinical application of antimicrobial peptides and bacteriophages requires validation.

The multifaceted roles of phosphoethanolamine-modified lipopolysaccharides: from stress response and virulence to cationic antimicrobial resistance.

SUMMARYLipopolysaccharides (LPS) are an integral part of the outer membrane of Gram-negative bacteria and play essential structural and functional roles in maintaining membrane integrity as well as in stress response and virulence. LPS comprises a membrane-anchored lipid A group, a sugar-based core region, and an O-antigen formed by repeating oligosaccharide units. 3-Deoxy-D-manno-octulosonic acid-lipid A (Kdo2-lipid A) is the minimum LPS component required for bacterial survival. While LPS modifications are not essential, they play multifaceted roles in stress response and host-pathogen interactions. Gram-negative bacteria encode several distinct LPS-modifying phosphoethanolamine transferases (PET) that add phosphoethanolamine (pEtN) to lipid A or the core region of LPS. The pet genes differ in their genomic locations, regulation mechanisms, and modification targets of the encoded enzyme, consistent with their various roles in different growth niches and under varied stress conditions. The discovery of mobile colistin resistance genes, which represent lipid A-modifying pet genes that are encoded on mobile elements and associated with resistance to the last-resort antibiotic colistin, has led to substantial interest in PETs and pEtN-modified LPS over the last decade. Here, we will review the current knowledge of the functional diversity of pEtN-based LPS modifications, including possible roles in niche-specific fitness advantages and resistance to host-produced antimicrobial peptides, and discuss how the genetic and structural diversities of PETs may impact their function. An improved understanding of the PET group will further enhance our comprehension of the stress response and virulence of Gram-negative bacteria and help contextualize host-pathogen interactions.

An early and stable mouse model of polymyxin-induced acute kidney injury.

BACKGROUND: Polymyxins have been revived as a last-line therapeutic option for multi-drug resistant bacteria and continue to account for a significant proportion of global antibiotic usage. However, kidney injury is often a treatment limiting event with kidney failure rates ranging from 5 to 13%. The mechanisms underlying polymyxin-induced nephrotoxicity are currently unclear. Researches of polymyxin-associated acute kidney injury (AKI) models need to be more standardized, which is crucial for obtaining consistent and robust mechanistic results. METHODS: In this study, male C57BL/6 mice received different doses of polymyxin B (PB) and polymyxin E (PE, also known as colistin) by different routes once daily (QD), twice daily (BID), and thrice daily (TID) for 3 days. We continuously monitored the glomerular filtration rate (GFR) and the AKI biomarkers, including serum creatinine (Scr), blood urea nitrogen (BUN), neutrophil gelatinase-associated lipocalin (NGAL), and kidney injury molecule-1 (KIM-1). We also performed histopathological examinations to assess the extent of kidney injury. RESULTS: Mice receiving PB (35 mg/kg/day subcutaneously) once daily exhibited a significant decrease in GFR and a notable increase in KIM-1 two hours after the first dose. Changes in GFR and KIM-1 at 24, 48 and 72 h were consistent and demonstrated the occurrence of kidney injury. Histopathological assessments showed a positive correlation between the severity of kidney injury and the changes in GFR and KIM-1 (Spearman's rho = 0.3167, P = 0.0264). The other groups of mice injected with PB and PE did not show significant changes in GFR and AKI biomarkers compared to the control group. CONCLUSION: The group receiving PB (35 mg/kg/day subcutaneously) once daily consistently developed AKI at 2 h after the first dose. Establishing an early and stable AKI model facilitates researches into the mechanisms of early-stage kidney injury. In addition, our results indicated that PE had less toxicity than PB and mice receiving the same dose of PB in the QD group exhibited more severe kidney injury than the BID and TID groups.

Effectiveness of combination therapy with intrathecal or intraventricular administration of polymyxin B for hospital-acquired central nervous system infections caused by carbapenem-resistant Acinetobacter baumannii: a retrospective study.

OBJECTIVES: To evaluate the therapeutic regimen, efficacy and safety of intrathecal or intraventricular (ITH/IVT) administration of polymyxin B for hospital-acquired central nervous system (CNS) infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB). METHODS: A retrospective study was performed on patients with CNS infections caused by CRAB treated with ITH/IVT combination therapy. The primary study outcome was the clinical efficacy after treatment. Secondary outcomes were bacterial clearance rate and safety of therapy. RESULTS: In total, 35 patients who received ITH (13[37.1%]) or IVT (22[62.9%]) polymyxin B as combination therapy were included. The median duration of ITH/IVT polymyxin B therapy was 9 days (interquartile ranges, 7-11). The overall clinical cure and bacterial clearance rate was 77.1% and 85.7%, respectively. No adverse effects deemed related with ITH/IVT polymyxin B were recorded. Clinical failure was independently associated with the initial Acute Physiology and Chronic Health Evaluation II (≥ 15) (odds ratio [OR], 1.24; 95% confidence interval [CI]: 1.05-1.42; P = 0.038) and Glasgow Coma Scale scores (≤ 8) (OR, 0.69; 95% CI: 0.49-0.88; P = 0.029). Early administration (within 4 days) of ITH/IVT polymyxin B therapy can support significantly higher clinical cure rate (OR, 0.65; 95% CI: 0.49-1.12; P < 0.001), and potentially reduce the length of treatment and the adverse effects. CONCLUSIONS: ITH/IVT administration of polymyxin B is a valid alternative for the treatment of CNS infections caused by CRAB. Early use of ITH/IVT polymyxin B can lead to higher clinical success.

A simple HPLC-MS/MS method for the determination of polymyxin B in human plasma and its application in the pharmacokinetic study in elderly patients infected with multidrug-resistant Gram-negative bacteria.

Introduction: Polymyxin B is widely used to treat infections caused by multidrug-resistant Gram-negative bacteria. However, the pharmacokinetic study data of PB in the elderly are scarce. Herein, a simple method to measure the concentration of PB in human plasma was developed and validated by high performance liquid chromatography-tandem mass spectrometry, and it was applied to a PK study in the elderly. Methods: PB was extracted from human plasma by a rapid protein-precipitation method using 0.1% formic acid in methanol and then separated on an ultimate AQ-C18 column using linear gradient elution with a 0.5-mL/min flow rate. Subsequently, PB was detected using a mass spectrometer operated in positive-ion and multiple-reaction-monitoring modes. Results: The lower limits of quantification of the method for Polymyxin B1 and Polymyxin B2 were 1.00 and 0.10 µg/mL, respectively. The linear ranges for PB1 and PB2 were 1.00-20.02 and 0.10-2.04 µg/mL, respectively. Patients receiving a 75-mg maintenance dose every 12h had AUCss, 24 h, and Css, av values of 117.70 ± 37.03 µg h/mL and 4.14 ± 1.74 µg/mL, respectively. For patients receiving a 100 mg maintenance dose, these values were 152.73 ± 70.09 µg h/mL and 5.43 ± 2.85 µg/mL, respectively. Conclusion: The validated HPLC-MS/MS method was successfully applied to a study on the pharmacokinetics of PB in elderly patients infected with multidrug-resistant Gram-negative bacteria. Both two dose strategies in this study would have a excessive PB exposure in the elderly patients then the therapeutic window recommended by guidelines.

Polymyxin B Plus Aerosolized Colistin vs Polymyxin B Alone in Hospital-acquired Pneumonia ("AEROCOL" Study): A Feasibility Study.

Introduction: In hospital-acquired pneumonia (HAP) due to extensively drug resistant gram-negative pathogens, can treatment with high-dose colistin aerosolization using specific aerosol delivery protocol, improve clinical outcome in addition to systemic polymyxin-B? Materials and methods: In a randomized control trial, invasively ventilated adult ICU patients with HAP in whom clinicians decided to start systemic polypeptide antibiotics, were randomized to receive either intravenous polymyxin-B plus high-dose colistin nebulization (5-MIU 8-hourly) using specific protocol or intravenous polymyxin-B alone. Results: The study was closed early after recruiting 60% of planned patients because of slow rate of recruitment (24 patients in over 30 months). Treatment success (Primary outcome) was nonsignificantly higher in intervention group (63.66 vs 30.77%; p = 0.217). There was higher rate of microbiological cure in intervention group (60 vs 9.09%: p = 0.018). Numerically better secondary outcomes including fever-free days, ventilator- or vasopressor free days at day-7, ICU and hospital mortality also did not reach statistical significance. Two episodes of transient hypoxia were seen during aerosol delivery. However, overall incidences of adverse effects were not different between groups. Conclusion: This study could not confirm superiority of high-dose colistin aerosolization plus systemic polymyxin-B strategy over polymyxin-B alone in treating HAP due to extensive drug resistance (XDR) gram-negative pathogens. How to cite this article: Ghosh S. Polymyxin B Plus Aerosolized Colistin vs Polymyxin B Alone in Hospital-acquired Pneumonia ("AEROCOL" Study): A Feasibility Study. Indian J Crit Care Med 2024;28(8):792-795.

Polymyxin B adjuvants against polymyxin B- and carbapenem-resistant Gram-negative bacteria.

Aim: Polymyxin B (PMB) is one of the few therapeutic options for treating infections caused by carbapenem-resistant Gram-negative bacteria (CR-GNB). However, the emergence of PMB-resistant CR-GNB strains has prompted the exploration of antibiotic adjuvants as potential therapeutic avenues. Thus, this study evaluates the potential of 3,5-dinitrobenzoic acid derivatives (DNH01, DNH11, DNH13 and DNH20) and isoniazid-N-acylhydrazones (INZ1-7, INZ9 and INZ11) as adjuvants to enhance PMB efficacy against CR-GNB.Materials & methods: MIC, MBC and drug combination assays were conducted using multidrug-resistant clinical isolates of Enterobacterales and Acinetobacter baumannii. In addition, the effects of PMB and PMB + DNH derivatives were assessed through flow cytometry and scanning electron microscopy (SEM).Results: DNH01, DNH11 and DNH20, unlike the INH-acylhydrazones, significantly restored PMB activity (MIC ≤ 2 µg/ml) in 80% of the tested isolates. Flow cytometry and SEM assays confirmed that DNH derivatives rescued the activity of PMB, yielding results comparable to those expected for PMB alone but at 256-fold lower concentrations.Conclusion: These findings suggest DNH derivatives hold substantial promise as PMB adjuvants to combat PMB-resistant CR-GNB infections.

[Box: see text].

In treacherous waters: detection of colistin-resistant bacteria in water and plastic litter from a recreational estuary.

Colistin resistance poses a major therapeutic challenge and resistant strains have now been reported worldwide. However, the occurrence of such bacteria in aquatic environments is considerably less understood. This study aimed to isolate and characterize colistin-resistant strains from water and plastic litter collected in an urban recreational estuary. Altogether, 64 strains with acquired colistin resistance were identified, mainly Acinetobacter spp. and Enterobacter spp. From these, 40.6% were positive for at least one mcr variant (1-9), 26.5% harbored, extended-spectrum beta-lactamases, 23.4% harbored, sulfonamide resistance genes, and 9.3% harbored, quinolone resistance genes. merA, encoding mercury resistance, was detected in 10.5% of these strains, most of which were also strong biofilm producers. The minimum inhibitory concentration toward colistin was determined for the mcr-positive strains and ranged from 2 to ≥512 µg ml-1. Our findings suggest that Gram-negative bacteria highly resistant to a last-resort antimicrobial can be found in recreational waters and plastic litter, thereby evidencing the urgency of the One Health approach to mitigate the antimicrobial resistance crisis.

Clinical outcomes and safety of polymyxin B versus tigecycline combination therapy for pneumonia of carbapenem-resistant Klebsiella pneumoniae: a retrospective cohort study.

PURPOSE: Infection by carbapenem-resistant Klebsiella pneumoniae (CRKP) has high mortality. There is no clear optimal therapeutic choice for pneumonia caused by CRKP. The aim of this study was to compare the clinical outcomes and safety of the standard doses of polymyxin B-based regimens vs tigecycline-based regimens and to identify risk factors for mortality. METHODS: This retrospective cohort study included patients with pneumonia caused by CRKP between January 1, 2020 and December 31, 2022. The primary outcomes were 7-day bacterial eradication rate and 14- and 28-day all-cause mortality. The secondary outcome was incidence of acute kidney injury. RESULTS: Seventy-three patients were included in this study, 29 in the polymyxin B-based combination therapy group and 44 in tigecycline-based combination therapy group. There were no significant differences between the two groups in terms of the 7-day bacterial eradication rate (31.03% vs 20.45%, p = 0.409), the 14-day all-cause mortality (37.93% vs 22.73%, p = 0.160), and the incidence of acute kidney injury (14.29% vs 6.82%, p = 0.526). The 28-day all-cause mortality in the polymyxin B-based therapy group was higher than in the tigecycline-based group (75.86% vs 45.45%, p = 0.010). Binary logistic regression analysis revealed that male and previous use of carbapenems were independent factors associated with 28-day all-cause mortality for patients treated with polymyxin B (p < 0.05). CONCLUSIONS: Polymyxin B-based combination therapy at the standard dose should be used with caution for patients with CRKP-induced pneumonia, especially for men who used carbapenems prior to CRKP detection.

Pharmacokinetics and safety of colistin sulfate after single and multiple intravenous doses in healthy Chinese subjects.

OBJECTIVE: Increasing antimicrobial resistance has led to the revival of the polymyxins as a last-resort therapeutic option for multidrug-resistant Gram-negative bacterial infections. A parenteral formulation of colistin sulfate is available solely in China. While the onset of action of IV colistin may occur faster than with its prodrug CMS, its pharmacokinetic (PK) profile remains unclear. METHODS: This single-centre, open-label, single- and multi-dose, phase 1 trial examined the PKs and safety of colistin sulfate in healthy Chinese adults. Participants received a single 10,000 units/kg (equivalent to 0.452 mg/kg) dose of colistin sulfate (single-dose group, n = 12) or the same dose q12h for 7 days (multi-dose group, n = 12) via a 2-h IV infusion. Colistin concentrations in plasma and urine were determined using LC-MS/MS, and the PK parameters calculated using non-compartmental analysis. RESULTS: After a single dose the peak concentration (Cmax), area under the curve from 0 to 12 h (AUC0-12h), terminal half-life (T1/2), volume of distribution (Vd), and total body clearance (CL) of colistin were 1.08 ± 0.18 mg/L, 4.73 ± 0.89 h·mg/L, 3.65 ± 0.55 h, 16.82 ± 2.70 L, and 3.24 ± 0.51 L/h, respectively. No accumulation of colistin was observed after multiple doses. The cumulative urinary recovery of colistin was 0.9 ± 0.7% within 24 h after multi-dose administration. No nephrotoxicity was reported. CONCLUSIONS: This study is the first to report colistin PKs in healthy Chinese subjects after single and multiple doses of colistin sulfate. The PK and safety data are required for optimal dose selection in clinical practice.

Maximally precise combinations to overcome metallo-ß-lactamase-producing Klebsiella pneumoniae.

Gram-negatives harboring metallo-ß-lactamases (MBLs) and extended-spectrum ß-lactamases (ESBLs) pose a substantial risk to the public health landscape. In ongoing efforts to combat these "superbugs," we explored the clinical combination of aztreonam and ceftazidime/avibactam together with varying dosages of polymyxin B and imipenem against Klebsiella pneumoniae (Kp CDC Nevada) in a 9-day hollow fiber infection model (HFIM). As previously reported by our group, although the base of aztreonam and ceftazidime/avibactam alone leads to 3.34 log10 fold reductions within 72 hours, addition of polymyxin B or imipenem to the base regimen caused maximal killing of 7.55 log10 and 7.4 log10 fold reduction, respectively, by the 72-hour time point. Although low-dose polymyxin B and imipenem enhanced the bactericidal activity as an adjuvant to aztreonam +ceftazidime/avibactam, regrowth to ~9 log10CFU/mL by 216 hours rendered these combinations ineffective. When aztreonam +ceftazidime/avibactam was supplemented with high-dose polymyxin B and or low-dose polymyxin B + imipenem, it resulted in effective long-term clearance of the bacterial population. Time lapse microscopy profiled the emergence of long filamentous cells in response to PBP3 binding due to aztreonam and ceftazidime. The emergence of spheroplasts via imipenem and damage to the outer membrane via polymyxin B was visualized as a mechanism of persister killing. Despite intrinsic mgrB and blaNDM-1 resistance, polymyxin B and ß-lactam combinations represent a promising strategy. Future studies using an integrated molecularly precise pharmacodynamic approach are warranted to unravel the mechanistic details to propose optimal antibiotic combinations to combat untreatable, pan-drug-resistant Gram-negatives.

Evaluating nephrotoxicity reduction in a novel polymyxin B formulation: insights from a 3D kidney-on-a-chip model.

This study aimed to assess the nephrotoxicity associated with VRP-034 (novel formulation of polymyxin B [PMB]) compared to marketed PMB in a three-dimensional (3D) kidney-on-a-chip model. To model the human kidney proximal tubule for analysis, tubular structures were established using 23 triple-channel chips seeded with RPTEC/hTERT1 cells. These cells were exposed to VRP-034 or PMB at seven concentrations (1-200 µM) over 12, 24, and 48 h. A suite of novel kidney injury biomarkers, cell health, and inflammatory markers were quantitatively assessed in the effluent. Additionally, caspase and cytochrome C levels were measured, and cell viability was evaluated using calcein AM and ethidium homodimer-1 (EthD-1). Exposure to marketed PMB resulted in significantly elevated levels (P < 0.05) of four key biomarkers (KIM-1, cystatin C, clusterin, and OPN) compared to VRP-034, particularly at clinically relevant concentrations of ≥10 µM. At 25 µM, all biomarkers demonstrated a significant increase (P < 0.05) with marketed PMB exposure compared to VRP-034. Inflammatory markers (interleukin-6 and interleukin-8) increased significantly (P < 0.05) with marketed PMB at concentrations of ≥5 µM, relative to VRP-034. VRP-034 displayed superior cell health outcomes, exhibiting lower lactate dehydrogenase release, while ATP levels remained comparable. Morphological analysis revealed that marketed PMB induced more severe damage, disrupting tubular integrity. Both treatments activated cytochrome C, caspase-3, caspase-8, caspase-9, and caspase-12 in a concentration-dependent manner; however, caspase activation was significantly reduced (P < 0.05) with VRP-034. This study demonstrates that VRP-034 significantly reduces nephrotoxicity compared to marketed PMB within a 3D microphysiological system, suggesting its potential to enable the use of full therapeutic doses of PMB with an improved safety profile, addressing the need for less nephrotoxic polymyxin antibiotics.

Identification of Polymyxin Resistance Gene mcr-10 from Different Food Samples in Shanghai, China.

This retrospective investigation (2019-2022) identified two plasmid-mediated mcr-10 from 6800 food samples in Shanghai, China and localized in a conjugative plasmid (pEC1918-mcr10) in Escherichia kobei from ready-to-eat food with high-level polymyxin B resistance, and a nonconjugative plasmid (pEC2001-mcr10) in E. coli from chicken. These genes were adjacent to ISEc36. This report highlights the emergence of mcr-10 from food samples in Shanghai, China. Active surveillance of vital resistance genes along food production chain should be performed.

Increased antimicrobial resistance of acid-adapted pathogenic Escherichia coli, and transcriptomic analysis of polymyxin-resistant strain.

This study investigated the acid adaptation and antimicrobial resistance of seven pathogenic Escherichia coli strains and one commensal strain under nutrient-rich acidic conditions. After acid adaptation, three pathogenic E. coli survived during 100 h incubation in tryptic soy broth at pH 3.25. Acid-adapted (AA) strains showed increased resistance to antimicrobials including ampicillin, ciprofloxacin and especially polymyxins (colistin and polymyxin B), the last resort antimicrobial for multidrug-resistant Gram-negative bacteria. Enterotoxigenic E. coli strain (NCCP 13717) showed significantly increased resistance to acids and polymyxins. Transcriptome analysis of the AA NCCP 13717 revealed upregulation of genes related to the acid fitness island and the arn operon, which reduces lipopolysaccharide binding affinity at the polymyxin site of action. Genes such as eptA, tolC, and ompCF were also upregulated to alter the structure of the cell membrane, reducing the outer membrane permeability compared to the control, which is likely to be another mechanism for polymyxin resistance. This study highlights the emergence of antimicrobial resistance in AA pathogenic E. coli strains, particularly polymyxin resistance, and the mechanisms behind the increased antimicrobial resistance, providing important insights for the development of risk management strategies to effectively control the antimicrobial resistant foodborne pathogens.

Novel 2-aminothiazole analogues both as polymyxin E synergist and antimicrobial agent against multidrug-resistant Gram-positive bacteria.

The widespread emergence of antibiotic resistance poses a substantial challenge to global health. While polymyxin E serves as a final option in treatment, its effectiveness is hindered by dose-related toxicity. A crucial strategy for addressing this issue involves incorporating an antibiotic adjuvant to enhance the antibiotic's efficacy and decrease the required dosage. Here, we reported a multifunctional antibacterial compound A33, containing a 2-aminothiazole scaffold. In vitro studies demonstrated that A33 in combination with polymyxin E inhibited the growth of various Gram-negative bacteria, meanwhile with minimum inhibitory concentrations (MICs) of 0.5-4 µg/mL against twenty-three Gram-positive bacteria, including two drug-resistant strains. In vivo studies showed significant efficacy of the combined treatment of A33 and polymyxin E in a mouse infection model. The mice treated with compound A33 (64 mg/kg) and polymyxin E (0.5 mg/kg) in combination had a 100 % survival rate. Mechanistic studies suggested that A33 might exert its synergistic effect by targeting the outer membrane of Gram-negative bacteria. The ADMET data demonstrated that A33 possessed good pharmacokinetic profiles and drug-likeness properties. Overall, the optimized compound A33 assisted polymyxin E in combating various Gram-negative bacteria and exhibited bactericidal effects against drug-resistant Gram-positive bacteria, offering a new potential therapeutic approach for managing mixed bacterial infections.

Protective potentials of polymyxin B and honey against bacterial lipopolysaccharide-induced endotoxemia in mice.

Objective: The experiment aimed to determine the effects of lipopolysaccharide (LPS), polymyxin B, and honey on survival rates, hematological parameters, liver and kidney biomarkers, blood glucose levels, serum insulin levels, and histopathology of the liver, kidney, lungs, brain, and pancreas in LPS-challenged mice. Materials and Methods: 50 male Swiss Albino mice (Mus musculus), aged 3 weeks, were randomly assigned into 5 groups (10 mice per group): Control group (A), LPS (2 mg/kg bwt/day IP in NS) treated group (B), polymyxin B (1.2 mg/kg bwt/day IM) pre-treated plus LPS (2 mg/kg bwt/day IP in NS) treated group (C), honey (10 gm/kg bwt/day PO) pre-treated plus LPS (2 mg/kg bwt/day IP in NS) treated group (D), both polymyxin B (1.2 mg/kg bwt/day IM) and honey (10 gm/kg bwt/day PO) pre-treated plus LPS (2 mg/kg bwt/day IP in NS) treated group (E). The LPS was administered intraperitoneally (IP) at 80 µg/mice/day, diluting in normal saline. After 16 weeks, the mice were sacrificed, and blood samples and organs (liver, kidney, lung, brain, and pancreas) were collected for laboratory tests. Results: The results revealed that in LPS-treated mice, the mortality rate was the highest, and hemato-biochemical parameters were altered. Histopathological examination in the group treated with LPS showed disarrangement of hepatocytes, cellular infiltrations in the glomerulus, alveolar congestion in the lungs, several nerve fiber degenerations in the brain, and degenerative changes in pancreatic islets. The mortality rate and hemato-biochemical and histopathological changes were restored by the combined treatment of polymyxin B and honey. Conclusion: LPS has detrimental effects on survival rate and hemato-biochemistry, which are lessened by taking honey and polymyxin B supplements.

Antibiotic resistance and epidemiological characteristics of polymyxin-resistant Klebsiella pneumoniae. / è€å¤šé»èŒç´ è‚ºç‚Žå ‹é›·ä¼¯èŒçš„è¯æ•ç‰¹å¾åŠæµè¡Œç— å­¦ç‰¹ç‚¹.

OBJECTIVES: The emergence of polymyxin-resistant Klebsiella pneumoniae (KPN) in clinical settings necessitates an analysis of its antibiotic resistance characteristics, epidemiological features, and risk factors for its development. This study aims to provide insights for the prevention and control of polymyxin-resistant KPN infections. METHODS: Thirty clinical isolates of polymyxin-resistant KPN were collected from the Third Xiangya Hospital of Central South University. Their antibiotic resistance profiles were analyzed. The presence of carbapenemase KPC, OXA-48, VIM, IMP, and NDM was detected using colloidal gold immunochromatography. Hypervirulent KPN was initially screened using the string test. Biofilm formation capacity was assessed using crystal violet staining. Combination drug susceptibility tests (polymyxin B with meropenem, tigecycline, cefoperazone/sulbactam) were conducted using the checkerboard method. Polymyxin-related resistance genes were detected by PCR. Multi-locus sequence typing (MLST) was performed for genotyping and phylogenetic tree construction. The study also involved collecting data from carbapenem-resistant (CR)-KPN polymyxin-resistant strains (23 strains, experimental group) and CR-KPN polymyxin-sensitive strains (57 strains, control group) to analyze potential risk factors for polymyxin-resistant KPN infection through univariate analysis and multivariate Logistic regression. The induction of resistance by continuous exposure to polymyxin B and colistin E was also tested. RESULTS: Among the 30 polymyxin-resistant KPN isolates, 28 were CR-KPN, all producing KPC enzyme. Four isolates were positive in the string test. Most isolates showed strong biofilm formation capabilities. Combination therapy showed additive or synergistic effects. All isolates carried the pmrA and phoP genes, while no mcr-1 or mcr-2 genes were detected. MLST results indicated that ST11 was the predominant type. The phylogenetic tree suggested that polymyxin-resistant KPN had not caused a hospital outbreak in the institution. The use of two or more different classes of antibiotics and the use of polymyxin were identified as independent risk factors for the development of polymyxin-resistant strains. Continuous use of polymyxin induced drug resistance. CONCLUSIONS: Polymyxin-resistant KPN is resistant to nearly all commonly used antibiotics, making polymyxin-based combination therapy a viable option. No plasmid-mediated polymyxin-resistant KPN has been isolated in the hospital. Polymyxin can induce resistance in KPN, highlighting the need for rational antibiotic use in clinical settings to delay the emergence of resistance.

Polymyxin resistance in Enterobacter cloacae complex in Brazil: phenotypic and molecular characterization.

Enterobacter cloacae complex isolates have been reported as an important nosocomial multidrug resistance pathogen. In the present study, we investigated antimicrobial susceptibility and the colistin-resistance rates, their genetic determinants and clonality among clinical E. cloacae complex isolates from different Brazilian states. For this, an initial screening was carried out on 94 clinical isolates of E. clocacae complex received between 2016 and 2018 by LAPIH-FIOCRUZ, using EMB plates containing 4 µg/mL of colistin, followed MIC determination, resulting in the selection of 26 colistin-resistant isolates from the complex. The presence of carbapenemases encoding genes (blaKPC, blaNDM and blaOXA-48), plasmidial genes for resistance to polymyxins (mcr1-9) and mutations in chromosomal genes (pmrA, pmrB, phoP and phoQ) described as associated with resistance to polymyxin were screened by PCR and DNA sequencing. Finally, the hsp60 gene was sequenced to identify species of the E. cloacae complex and genetic diversity was evaluated by PFGE and MLST. The results have shown that among 94 E. cloacae complex isolates, 19 (20.2%) were colistin-resistant. The resistant strains exhibited MIC ranging from 4 to 128 µg / mL and E. hormaechei subsp. steigerwaltii was the prevalent species in the complex (31,6%), followed by E. cloacae subsp. cloacae (26,3%). The antimicrobials with the highest susceptibility rate were gentamicin (21%) and tigecycline (26%). Carbapenemases encoding genes (blaKPC n = 5, blaNDM n = 1) were detected in 6 isolates and mcr-9 in one. Among the modifications found in PmrA, PmrB, PhoP e PhoQ (two-component regulatory system), only the S175I substitution in PmrB found in E. cloacae subsp cloacae isolates were considered deleterious (according to the prediction of PROVEAN). By PFGE, 13 profiles were found among E. cloacae complex isolates, with EcD the most frequent. Furthermore, by MLST 10 ST's, and 1 new ST, were identified in E. cloacae. In conclusion, no prevalence of clones or association among carbapenemase production and polymyxin resistance was found between the E. cloacae. Thereby, the results suggest that the increased polymyxin-resistance is related to the selective pressure exerted by the indiscriminate use in hospitals. Lastly, this study highlights the urgent need to elucidate the mechanism involved in the resistance to polymyxin in the E. cloacae complex and the development of measures to control and prevent infections caused by these multiresistant bacteria.