Efficacy and safety of polymyxin B in carbapenem-resistant gram-negative organisms infections

Factors Associated with Successful Treatment of Carbapenem-Resistant Gram-Negative Bacilli Infections Using Intravenous Colistin Sulfate in China: A Real-World Retrospective Study

Objective

To evaluate the efficacy of intravenous colistin sulfate (CS) in the treatment of carbapenem-resistant Gram-negative bacilli (CR-GNB) infections in real-world clinical settings and to identify factors influencing its therapeutic outcomes, with the aim of promoting the rational use of CS.

Methods

A retrospective analysis was conducted on the clinical characteristics and treatment outcomes of 174 patients diagnosed with CR-GNB infection who received intravenous CS at our center between January 2021 and December 2023. The study evaluated both clinical efficacy and adverse drug reactions (ADRs).

Results

Among the 174 patients, 118 cases (67.8%) demonstrated clinical improvement, and the bacterial clearance rate was 53.9%. Multivariate logistic regression analysis identified several factors significantly associated with treatment efficacy: neurological disease (OR [95% CI]: 0.100 [0.019-0.541]; p = 0.006), admission to a surgical ward (OR [95% CI]: 0.136 [0.023-0.801]; p = 0.027), septic shock (OR [95% CI]: 5.147 [1.901-14.096]; p = 0.001), and empirical use of CS (OR [95% CI]: 4.250 [1.109-16.291]; p = 0.035). Additionally, 10 cases (5.8%) of acute kidney injury (AKI) were attributed to nephrotoxicity from CS, with 2 cases recovering after discontinuation of the drug.

Conclusion

Our findings suggest that intravenous colistin sulfate may be an effective treatment option for CR-GNB infections when used appropriately. However, further studies are required to better understand its real-world efficacy and safety profile.

Monte Carlo simulation to optimize polymyxin B dosing regimens for the treatment of Gram-negative bacteremia

Objective

This study aimed to predict and evaluate the efficacy of various polymyxin B dosing regimens for Gram-negative bacteremia using Monte Carlo simulation, with a specific focus on assessing the efficacy in patients receiving continuous renal replacement therapy (CRRT). The goal was to optimize clinical dosing regimens and guide rational polymyxin B use in practice.

Methods

A total of 1,939 Gram-negative bacterial strains were analyzed, collected between April 2019 and December 2021 through the China Bloodstream Gram-negative Pathogens Antimicrobial Resistance and Virulence Surveillance Network (CARVIS-NET). Pharmacokinetic parameters of polymyxin B from existing literature were used to conduct a Monte Carlo simulation based on pharmacokinetic/pharmacodynamic (PK/PD) theory. The probability of target attainment (PTA) and cumulative fraction of response (CFR) were evaluated across various dosing regimens.

Results

The main pathogens of Gram-negative bacteremia were Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii, all of which demonstrated high susceptibility to polymyxin B. For pathogens with a minimum inhibitory concentration (MIC) ≤1 mg/L, all regimens achieved PTA >90%. However, when the MIC increased to 2 mg/L, the PTA for the 500,000 IU q12h regimen decreased to 77.53%, and at an MIC of 4 mg/L, none of the dosing regimens achieved a PTA >90%. For P. aeruginosa and K. pneumoniae with MIC ≤0.5 mg/L, all regimens demonstrated effectiveness. However, at MIC ≥1 mg/L, significant declines in PTA were observed, with the 500,000 IU q12h and 1.25 mg/kg q12h regimens yielding suboptimal outcomes. In CRRT patients, PTA values declined further, particularly against K. pneumoniae, raising concerns about potential treatment failure.

Conclusion

Polymyxin B demonstrates high efficacy for Gram-negative bacteremia with MIC ≤1 mg/L. However, efficacy diminishes as MIC increases, particularly for P. aeruginosa and K. pneumoniae, where 500,000 IU q12h and 1.25 mg/kg q12h regimens may result in suboptimal outcomes. For CRRT patients with K. pneumoniae bacteremia, therapeutic drug monitoring and dose adjustments are crucial to mitigate treatment failure risks.

Overall mutational scanning unveils the essential active residues for the mechanistic action of MCR-1

Polymyxins, including colistin and polymyxin B, serve as crucial last-resort antibiotics for managing infections caused by carbapenem-resistant Enterobacterales (CRE). However, the rapid spread of the mobilized colistin resistance gene (mcr-1) challenged the efficacy of treatment by polymyxins. The mcr-1 gene encoded a transmembrane phosphoethanolamine (PEA) transferase enzyme, MCR-1. MCR-1 could catalyze the transfer of PEA moiety of phosphatidylethanolamine (PE) to the 1' (or 4')-phosphate group of the lipid A. Despite the determination of several structures of the soluble domain of MCR-1, the structural and biochemical mechanisms of integral MCR-1 remain less understood. In this study, we utilized an alanine scanning mutagenesis approach to systematically investigate the functional attributes of distinct regions within MCR-1. We identified fifteen critical residues that are indispensable for the enzymatic activity of MCR-1 and are pivotal for its ability to confer resistance to colistin. Furthermore, molecular docking of MCR-1 complexed with the phosphoethanolamine (PE) substrate revealed the presence of a channel-shaped cavity, a characteristic feature shared with other phosphoethanolamine transferases. Despite MCR-1 exhibiting a low sequence identity with both MCR homologues and other phosphoethanolamine (PEA) transferases, several conserved sites were identified, including Y97, M105, K333, H395, L477, and H478, suggesting a potentially shared catalytic mechanism among them for modifying LPS-lipid A. Overall, these findings provide a deep understanding of the catalytic mechanism of MCR-1 for colistin resistance. Moreover, these findings provide a robust structural and functional foundation, enabling the rational design of targeted inhibitors and restoring colistin activity against serious infections with carbapenem-resistant Enterobacterales (CRE).

Advances in the clinical treatment of multidrug-resistant pathogens using polymyxins

OBJECTIVES

Polymyxins are a vital class of antibiotics used to combat multidrug-resistant Gram-negative bacteria. However, their use is limited due to potential nephrotoxicity and the availability of alternative antibiotics. This review aims to examine the properties of polymyxins and the clinical advances in their use for treating infections caused by carbapenem-resistant Gram-negative bacteria (CR-GNB).

METHODS

This review analyses literature on polymyxin properties and various clinical approaches, including intravenous drip infusion, nebulized or dry powder inhalation, and ointment application. Treatment efficacy in terms of bacterial eradication, cure rate and mortality rate are reviewed and evaluated.

RESULTS

Polymyxins have been reintroduced to treat critical infections due to the increasing prevalence of CR-GNB. Clinical trials and studies have confirmed that polymyxins can effectively treat CR-GNB infections when the formulation and administration are appropriate, with acceptable levels of nephrotoxicity.

CONCLUSIONS

In the future, the development of polymyxin formulations will aim to improve their clinical effectiveness while reducing toxicity and side effects and preventing the emergence of polymyxin-resistant strains. Enhanced efficacy and minimized potential side effects can be achieved by developing new polymyxin-delivery systems that provide a smart and controlled release or customized patient administration.

Spray dried polymyxin B liposome for inhalation against gram-negative bacteria

This study aimed to provide an alternative and effective delivery system to combat polymyxin B (PMB) toxicity and bacterial resistance through inhalation therapy. PMB was formulated as liposomal dry powder for inhalation using thin-film hydration and spray-dried methods. PMB formulations were characterized physically. The aerodynamic properties were determined using next-generation impactor (NGI). In vitro drug release was done in a phosphate buffer pH 7.4 for 2 h. Cytotoxicity was evaluated by the MTT cell viability assay. Antimicrobiological activities were done using bioassay and flow cytometry. Particle sizes of the spay-dried formulations were between 259.83 ± 9.91 and 518.73 ± 27.08 nm while the zeta potentials ranged between 3.07 ± 0.27 and 4.323 ± 0.36 mV. The Fourier-transform infrared spectroscopy shows no interaction between PMB and other excipients. Differential scanning calorimetry thermograms revealed amorphousness of the formulated powders and SEM revealed spherical PMB formulations. Similarly, mass media aerodynamic diameter results were 1.72-2.75 nm, and FPF was 25%-26%. The cumulative release of the PMB formulations was 90.3 ± 0.6% within 2 h. The killing kinetics revealed total cell death at 12 and 24 h for Pseudomonas aeruginosa and Escherichia coli, respectively. The PMB inhalation liposome showed better activity and was safe for lung-associated cell lines.

Factors affecting the effectiveness and safety of polymyxin B in the treatment of Gram-negative bacterial infections: A meta-analysis of 96 articles

PURPOSE

Polymyxin B, with its unique structure and mechanism of action, has emerged as a key therapeutic agent against Gram-negative bacteria. The study aims to explore potential factors to influence its effectiveness and safety.

METHODS

A model-based meta-analysis of 96 articles was conducted, focusing on factors like dosage, bacterial species, and combined antibiotic therapy. The analysis evaluated mortality rates and incidence rate of renal dysfunction, also employing parametric survival models to assess 30-d survival rates.

RESULTS

In the study involving 96 articles and 9716 patients, polymyxin B's daily dose showed minimal effect on overall mortality, with high-dose group mortality at 33.57% (95% confidence intervals [CI]: 29.15-38.00) compared to the low-dose group at 35.44% (95% CI: 28.99-41.88), P = 0.64. Mortality significantly varied by bacterial species, with Pseudomonas aeruginosa infections at 58.50% (95% CI: 55.42-63.58). Monotherapy exhibited the highest mortality at 40.25% (95% CI: 34.75-45.76), P < 0.01. Renal dysfunction was more common in high-dose patients at 29.75% (95% CI: 28.52-30.98), with no significant difference across antibiotic regimens, P = 0.54. The 30-d overall survival rate for monotherapy therapy was 63.6% (95% CI: 59.3-67.5) and 70.2% (95% CI: 64.4-76.2) for association therapy with β-lactam drugs.

CONCLUSIONS

The dosage of polymyxin B does not significantly change death rates, but its effectiveness varies based on the bacterial infection. Certain bacteria like P. aeruginosa are associated with higher mortality. Combining polymyxin B with other antibiotics, especially β-lactam drugs, improves survival rates. Side effects depend on the dose, with lower doses being safer. These findings emphasize the importance of customizing treatment to balance effectiveness and safety.

Carbapenem-resistant Enterobacterales sepsis following endoscopic retrograde cholangiopancreatography: risk factors for 30-day all-cause mortality and the development of a nomogram based on a retrospective cohort

BACKGROUND

Endoscopic retrograde cholangiopancreatography (ERCP) has become a routine endoscopic procedure that is essential for diagnosing and managing various conditions, including gallstone extraction and the treatment of bile duct and pancreatic tumors. Despite its efficacy, post-ERCP infections - particularly those caused by carbapenem-resistant Enterobacterales (CRE) - present significant risks. These risks highlight the need for accurate predictive models to enhance postprocedural care, reduce the mortality risk associated with post-ERCP CRE sepsis, and improve patient outcomes in the context of increasing antibiotic resistance.

OBJECTIVE

This study aimed to examine the risk factors for 30-day mortality in patients with CRE sepsis following ERCP and to develop a nomogram for accurately predicting 30-day mortality risk.

METHODS

Data from 195 patients who experienced post-ERCP CRE sepsis between January 2010 and December 2022 were analyzed. Variable selection was optimized via the least absolute shrinkage and selection operator (LASSO) regression model. Multivariate logistic regression analysis was then employed to develop a predictive model, which was evaluated in terms of discrimination, calibration, and clinical utility. Internal validation was achieved through bootstrapping.

RESULTS

The nomogram included the following predictors: age > 80 years (hazard ratio [HR] 2.61), intensive care unit (ICU) admission within 90 days prior to ERCP (HR 2.64), hypoproteinemia (HR 4.55), quick Pitt bacteremia score ≥ 2 (HR 2.61), post-ERCP pancreatitis (HR 2.52), inappropriate empirical therapy (HR 3.48), delayed definitive therapy (HR 2.64), and short treatment duration (< 10 days) (HR 5.03). The model demonstrated strong discrimination and calibration.

CONCLUSIONS

This study identified significant risk factors associated with 30-day mortality in patients with post-ERCP CRE sepsis and developed a nomogram to accurately predict this risk. This tool enables healthcare practitioners to provide personalized risk assessments and promptly administer appropriate therapies against CRE, thereby reducing mortality rates.

Efficacy and Safety Factors Related to Plasma Concentration-Optimized Polymyxin B Therapy in Treating Carbapenem-Resistant Gram-Negative Bacterial Infections in China

Background

Polymyxin B (PMB)-based combination therapies are used to treat severe carbapenem-resistant gram-negative bacterial (CR-GNB) infections. This observational study investigated the relationship between clinical factors, including PMB concentration, and clinical efficacy and safety.

Patients and Methods

Polymyxin B regimens were optimized through therapeutic drug monitoring (TDM) and area under the concentration-time curve (AUC). In all, 382 samples were tested from 130 patients. Logistic regression was used to analyze the relationships between variables with clinical efficacy and 30-day mortality factors were analyzed by Cox regression. The sensitivity and specificity of Cmin and AUC for the occurrence of acute kidney injury (AKI) were determined by ROC curve analysis.

Results

The clinical effectiveness of PMB was 65.4%. Multivariate logistic regression analysis revealed that lung infection, continuous renal replacement therapy, and C-reactive protein were independent factors significantly associated with efficacy. AKI occurred in 14.6% of the patients during treatment; age > 73 years (OR: 3.63; 95% CI: 1.035-12.727; P = 0.044), Cmin greater than 2.3 µg/mL (OR: 7.37; 95% CI: 1.571-34.580; P = 0.011), combined vancomycin (OR: 9.47; 95% CI: 1.732-51.731; P = 0.009), and combined piperacillin-tazobactam (OR: 21.87; 95% CI: 3.139-152.324; P = 0.002) were independent risk factors. The identified PMB cut-offs for predicting AKI were Cmin = 2.3 µg/mL and AUC = 82.0 mg h/L.

Conclusion

Polymyxin B-based combination regimens are effective in treating CR-GNB infections, particularly bloodstream infections, but have shown unsatisfactory for lung infections. Cmin ≥ 2.3 µg /mL and AUC ≥ 82.0 mg h/L may increase PMB-associated AKI incidence. PMB dose should be adjusted based on TDM to ensure efficacy.

Characteristics of Klebsiella pneumoniae pyogenic liver abscess from 2010-2021 in a tertiary teaching hospital of South China

OBJECTIVES

Pyogenic liver abscess (PLA) is a severe and potentially fatal infectious disease. Klebsiella pneumoniae (K. pneumoniae) is the predominant pathogen responsible for PLA. This study aims to investigate the clinical characteristics and prognostic factors of K. pneumoniae-induced pyogenic liver abscess (KP-PLA), particularly those caused by carbapenem-resistant K. pneumoniae (CRKP).

METHODS

Analyses were performed on PLA patients from January 2010 to December 2021, to investigate the differences of K. pneumoniae from other etiologically infected PLA patients. Univariate and multivariate logistic regression analyses were used to compare prognostic factors between patients with carbapenem-resistant K. pneumoniae PLA (CRKP-PLA) and patients with carbapenem-sensitive K. pneumoniae PLA.

RESULTS

Univariate analysis demonstrated a significant association between KP-PLA and factors including diabetes mellitus (P < 0.001), cholecystitis and cholelithiasis (P = 0.032), single abscess (P = 0.016), and abscesses with a diameter over 50 mm (P = 0.004). The CRKP group exhibited a higher prevalence of therapeutic interventions before K. pneumoniae infection, including abdominal surgery, mechanical ventilation, sputum suction, tracheal cannula, routine drainage of the abdominal cavity, and peripherally inserted central venous catheters (P < 0.05). Multivariate logistic regression analysis revealed that admission to the intensive care unit was an independent risk factor associated with CRKP-PLA (odds ratio 36; 95% confidence interval 1.77-731.56; P = 0.020).

CONCLUSION

The KP-PLA patients were significantly associated with diabetes and were more likely to have single abscesses larger than 50 mm. PLA patients with a history of admission to intensive care unit or invasive therapeutic procedures should be given special consideration if combined with CRKP infection.

Clinical Efficacy and Safety of Colistin Sulfate in the Treatment of Carbapenem-Resistant Organism Infections in Patients with Hematological Diseases

INTRODUCTION

Carbapenem-resistant organisms (CRO) have emerged as a significant worldwide issue. However, the availability of efficacious antibiotics for treating CRO infections remains limited. Polymyxins, including colistin sulfate, represent the last-line therapeutic option against CRO infections. This study aims to retrospectively evaluate the clinical effectiveness and safety of colistin sulfate in managing CRO infections among patients with hematological diseases.

METHODS

Between April 2022 and January 2023, a total of 118 hematological patients diagnosed with CRO infection were treated with colistin sulfate at Suzhou Hongci Hospital of Hematology. The assessment encompassed the clinical efficacy, bacterial clearance rate, adverse reactions, and 30-day all-cause mortality.

RESULTS

The study found that the total effective rate of colistin sulfate in the treatment of CRO infection was 74.6%, with a bacterial clearance rate of 72.6%. Throughout the treatment, nephrotoxicity occurred in 7.6% of cases, neurotoxicity in 2.5% of cases, and the 30-day all-cause mortality rate was 22.9%. Multivariate logistic analysis revealed that the treatment course and combination medication with other antimicrobials were independent factors affecting the clinical efficacy of colistin sulfate.

CONCLUSION

Our study demonstrates that the treatment of colistin sulfate can achieve high clinical efficacy and microbial responses, with a low risk of nephrotoxicity. This study provides evidence of the positive clinical efficacy and safety of colistin sulfate treatment in these patients. High-quality randomized controlled trials are still needed to further confirm the beneficial role of colistin sulfate.

Population Pharmacokinetic Modeling Using Polymyxin B Free Plasma Concentrations From Published Reports and Evaluation of Dosage Regimens Based on Monte Carlo Simulation in Critically Ill Patients

A population pharmacokinetic (pop PK) model of polymyxin B was developed using nonlinear mixed-effects (NONMEM) modeling based on free plasma concentrations to determine whether dose adjustment is required in critically ill patients. One thousand pharmacokinetic profiles for virtual patients with a body weight of 70 kg were simulated using Monte Carlo simulation at different dose scenarios, and area under the concentration-time curve of free drug (fAUC) was computed. The probability of target attainment (PTA) at each minimum inhibitory concentration (MIC) was calculated using fAUC/MIC as a pharmacokinetic/pharmacodynamic (PK/PD) index. The final population PK model was a 2-compartment model. PTA showed that 3.5 mg/kg/day regimens of polymyxin B effectively achieved the fAUC/MIC target of 10 (one log10 kill) against Pseudomonas aeruginosa strains with MIC of 1 mg/L or less (PTA,  90.7% or greater), while the dose regimen were ineffective against strains with an MIC of 2 mg/L or greater (PTA, 56.9% or less). For Klebsiella pneumoniae, the fAUC/MIC target of 17.4 (one log10 kill) was achieved in more than 90.4% of cases for MIC of 0.5 mg/L or less with 3 mg/kg/day regimens. However, the PTA decreased dramatically as MICs increased above 1 mg/L (PTA, 56.1% or less). The polymyxin B dosage regimen of 3.5 mg/kg/day and 3 mg/kg/day are sufficient to treat P. aeruginosa infections with an MIC of 1 mg/L or less and K. pneumoniae infections with an MIC of 0.5 mg/L or less, respectively. The current recommended dose (1.5-3 mg/kg/day) of polymyxin B appears inadequate to attain the PK/PD target for therapeutic efficacy against infections caused by P. aeruginosa and K. pneumoniae isolates when MIC is above the values.

The Efficacy and Influencing Factors of Polymyxin B in High-Level Carbapenem-Resistant Klebsiella pneumoniae Infections

Background

Polymyxin B (PMB) is a remedial treatment for carbapenem-resistant Klebsiella pneumoniae (CRKP) infection; however, there is a paucity of reports on the treatment of high-level CRKP infections with polymyxin B. Studies are needed to explore its treatment efficacy and associated influencing factors.

Methods

Patients with high-level CRKP infections treated with PMB during hospitalization from June 2019 to June 2021 in a hospital were retrospectively studied, and risk factors affecting the efficacy were explored by subgroup analysis.

Results

A total of 92 patients were enrolled, and the results showed that the PMB-based regimen had a bacterial clearance rate of 45.7%, an all-cause discharge mortality rate of 22.8%, and an incidence of acute kidney injury (AKI) of 27.2% for high-level CRKP treatment. The combination of β-lactams other than carbapenems facilitated bacterial clearance, and the combination of electrolyte disturbances and higher APACHE II scores was detrimental to microbial clearance. Risk factors for all-cause discharge mortality were advanced age, concomitant antifungal drugs, concomitant tigecycline and incidence of AKI.

Conclusion

PMB-based regimens are an effective option for the treatment of high-level CRKP infections. However, the optimal dose of treatment and the choice of combination regimens need to be explored in further studies.

Efficacy and safety of polymyxin E sulfate in the treatment of critically ill patients with carbapenem-resistant organism infections

Objective

Polymyxins are currently the last line of defense in the treatment of carbapenem-resistant organisms (CRO). As a kind of polymyxin available for clinical use in China, we aim to explore the efficacy and safety of colistin sulfate (Polymyxin E sulfate, PES) in this study.

Methods

This real-world retrospective study included 119 patients diagnosed with CRO infection and treated with PES for more than 72 h, from May 2020 to July 2022 at West China Hospital. The primary outcome was clinical efficacy at the end of treatment, and secondary outcomes included microbial response, in-hospital mortality and incidence of nephrotoxicity.

Results

The effective clinical and microbiological responses were 53.8% and 49.1%, respectively. And the in-hospital mortality was 27.7%. Only 9.2% of patients occurred with PES-related nephrotoxicity. Multivariate analysis revealed that duration of PES was an independent predictor of effective therapy, while age-adjusted Charlson comorbidity index (aCCI) and post-treatment PCT(p-PCT) were independent risk factors for poor outcome.

Conclusions

PES can be a salvage treatment for CRO-induced infections with favorable efficacy and low nephrotoxicity. The treatment duration of PES, aCCI and p-PCT were factors related to the clinical effectiveness of PES.