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.

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.

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.

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.

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.

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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.

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

BACKGROUND: 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 10000 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.

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.