Clinical translation of polymyxin-based combination therapy: Facts, challenges and future opportunities

Antimicrobial activity of ceftibuten/polymyxin B combination against polymyxin/carbapenem-resistant Klebsiella pneumoniae

OBJECTIVES

To evaluate the synergistic effect of a ceftibuten and polymyxin B combination and to determine its capacity to overcome polymyxin B resistance in polymyxin/carbapenem-resistant (PC-R) Klebsiella pneumoniae.

METHODS

To investigate the combination's antibacterial efficacy, antimicrobial susceptibility tests using broth microdilution methods, chequerboard assays and time-kill testing were performed. Antibiofilm activity was also assessed. The treatment's effect on the bacterial cell membrane was examined by quantifying intracellular protein leakage and conducting scanning electron microscopy. Haemocompatibility tests were conducted to evaluate toxicity. Additionally, an infection model was established using Swiss mice to assess in vivo antimicrobial activity.

RESULTS

The ceftibuten/polymyxin B combination demonstrated synergistic effects against several PC-R strains of K. pneumoniae, as determined by the FIC index (FICI) values, which ranged from 0.15 to 0.37. This combination was efficacious, exhibiting bactericidal activity at twice the MIC. Ceftibuten/polymyxin B also demonstrated antibiofilm activity. Additionally, ceftibuten/polymyxin B neither damaged the bacterial membrane nor exhibited haemolytic activity. Based on these findings, the in vivo therapeutic potential was investigated and it was found that ceftibuten/polymyxin B significantly decreased the bacterial load in the peritoneal lavage fluid of mice, revealing its effectiveness in treating infections caused by PC-R K. pneumoniae.

CONCLUSIONS

The ceftibuten/polymyxin B combination exhibited synergistic effects in vitro and in vivo, and thus might be a promising therapeutic alternative for treating PC-R K. pneumoniae infections. As the combination was efficacious in preclinical models, researchers may further investigate its potential in clinical studies.

Fatty acid chain modification enhances the serum stability of antimicrobial peptide B1 and activities against Staphylococcus aureus and Klebsiella pneumoniae

Antimicrobial peptides (AMPs) possess broad-spectrum antibacterial properties and low resistance development, making them promising candidates for new antibacterial drugs. Incorporating fatty acid chains into AMPs can increase their hydrophobicity, strengthen membrane affinity, and improve their antibacterial effectiveness and stability. This study introduces fatty acid chains of varying lengths into the naturally derived antimicrobial peptide B1. These modified peptides were evaluated for their antibacterial activity, stability, and biocompatibility to identify the optimal chain length for analogues. The analogues B1-C6 and B1-C8 exhibited significantly enhanced antimicrobial activities against Staphylococcus aureus (S. aureus) and Klebsiella pneumoniae (K. pneumonia), demonstrating better stability and biocompatibility. Following acute toxicity and skin irritation tests on mice, further in vivo tests using a mouse skin inflammation model showed that these peptides significantly restrain bacterial growth and promote wound healing. The skin healing rate in the high-concentration group reached 95.92%, 97.35% 98.42% and 98.17%, respectively. These findings indicated that optimizing the hydrophobic-hydrophilic balance in AMPs is crucial for maximizing their therapeutic potential. This research offers a promising approach for designing effective AMPs to treat infections caused by S. aureus and K. pneumoniae.

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.

Artificial Intelligence-Clinical Decision Support System in Infectious Disease Control: Combatting Multidrug-Resistant Klebsiella pneumoniae with Machine Learning

Purpose

The World Health Organization has identified Klebsiella pneumoniae (KP) as a significant threat to global public health. The rising threat of carbapenem-resistant Klebsiella pneumoniae (CRKP) leads to prolonged hospital stays and higher medical costs, necessitating faster diagnostic methods. Traditional antibiotic susceptibility testing (AST) methods demand at least 4 days, requiring 3 days on average for culturing and isolating the bacteria and identifying the species using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), plus an extra day for interpreting AST results. This lengthy process makes traditional methods too slow for urgent clinical situations requiring rapid decision-making, potentially hindering prompt treatment decisions, especially for fast-spreading infections such as those caused by CRKP. This research leverages a cutting-edge diagnostic method that utilizes an artificial intelligence-clinical decision support system (AI-CDSS). It incorporates machine learning algorithms for the swift and precise detection of carbapenem-resistant and colistin-resistant strains.

Patients and Methods

We selected 4307 KP samples out of a total of 52,827 bacterial samples due to concerns about multi-drug resistance using MALDI-TOF MS and Vitek-2 systems for AST. It involved thorough data preprocessing, feature extraction, and machine learning model training fine-tuned with GridSearchCV and 5-fold cross-validation, resulting in high predictive accuracy, as demonstrated by the receiver operating characteristic and area under the curve (AUC) scores, laying the groundwork for our AI-CDSS.

Results

MALDI-TOF MS analysis revealed distinct intensity profiles differentiating CRKP and susceptible strains, as well as colistin-resistant Klebsiella pneumoniae (CoRKP) and susceptible strains. The Random Forest Classifier demonstrated superior discriminatory power, with an AUC of 0.96 for detecting CRKP and 0.98 for detecting CoRKP.

Conclusion

Integrating MALDI-TOF MS with machine learning in an AI-CDSS has greatly expedited the detection of KP resistance by approximately 1 day. This system offers timely guidance, potentially enhancing clinical decision-making and improving treatment outcomes for KP infections.

Gallium Nitrate Enhances Antimicrobial Activity of Colistin against Klebsiella pneumoniae by Inducing Reactive Oxygen Species Accumulation

Klebsiella pneumoniae, a pathogen of critical clinical concern, urgently demands effective therapeutic options owing to its drug resistance. Polymyxins are increasingly regarded as a last-line therapeutic option for the treatment of multidrug-resistant (MDR) Gram-negative bacterial infections. However, polymyxin resistance in K. pneumoniae is an emerging issue. Here, we report that gallium nitrate (GaNt), an antimicrobial candidate, exhibits a potentiating effect on colistin against MDR K. pneumoniae clinical isolates. To further confirm this, we investigated the efficacy of combined GaNt and colistin in vitro using spot dilution and rapid time-kill assays and growth curve inhibition tests and in vivo using a murine lung infection model. The results showed that GaNt significantly increased the antimicrobial activity of colistin, especially in the iron-limiting media. Mechanistic studies demonstrated that bacterial antioxidant activity was repressed by GaNt, as revealed by RNA sequencing (RNA-seq), leading to intracellular accumulation of reactive oxygen species (ROS) in K. pneumoniae, which was enhanced in the presence of colistin. Therefore, oxidative stress induced by GaNt and colistin augments the colistin-mediated killing of wild-type cells, which can be abolished by dimethyl sulfoxide (DMSO), an effective ROS scavenger. Collectively, our study indicates that GaNt has a notable impact on the antimicrobial activity of colistin against K. pneumoniae, revealing the potential of GaNt as a novel colistin adjuvant to improve the treatment outcomes of bacterial infections. IMPORTANCE This study aimed to determine the antimicrobial activity of GaNt combined with colistin against Klebsiella pneumoniae in vitro and in vivo. Our results suggest that by combining GaNt with colistin, antioxidant activity was suppressed and reactive oxygen species accumulation was induced in bacterial cells, enhancing antimicrobial activity against K. pneumoniae. We found that GaNt functioned as an antibiotic adjuvant when combined with colistin by inhibiting the growth of multidrug-resistant K. pneumoniae. Our study provides insight into the use of an adjuvant to boost the antibiotic potential of colistin for treating infections caused by multidrug-resistant K. pneumoniae.

Pharmacokinetics/pharmacodynamics of polymyxin B in patients with bloodstream infection caused by carbapenem-resistant Klebsiella pneumoniae

Introduction: Polymyxin B is a last-line therapy for carbapenem-resistant microorganisms. However, a lack of clinical pharmacokinetic/pharmacodynamic (PK/PD) data has substantially hindered dose optimization and breakpoint setting. Methods: A prospective, multi-center clinical trial was undertaken with polymyxin B [2.5 mg/kg loading dose (3-h infusion), 1.25 mg/kg/12 h maintenance dose (2-h infusion)] for treatment of carbapenem-resistant K. pneumoniae (CRKP) bloodstream infections (BSI). Safety, clinical and microbiological efficacy were evaluated. A validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was applied to determine the concentrations of polymyxin B in blood samples. Population pharmacokinetic (PK) modeling and Monte Carlo simulations were conducted to examine the susceptibility breakpoint for polymyxin B against BSI caused by CRKP. Results: Nine patients were enrolled and evaluated for safety. Neurotoxicity (5/9), nephrotoxicity (5/9), and hyperpigmentation (1/9) were recorded. Blood cultures were negative within 3 days of commencing therapy in all 8 patients evaluated for microbiological efficacy, and clinical cure or improvement occurred in 6 of 8 patients. C_max and C_min following the loading dose were 5.53 ± 1.80 and 1.62 ± 0.41 mg/L, respectively. With maintenance dosing, AUC_ss,24 h was 79.6 ± 25.0 mg h/L and C_ss,avg 3.35 ± 1.06 mg/L. Monte Carlo simulations indicated that a 1 mg/kg/12-hourly maintenance dose could achieve >90% probability of target attainment (PTA) for isolates with minimum inhibitory concentration (MIC) ≤1 mg/L. PTA dropped substantially for MICs ≥2 mg/L, even with a maximally recommended daily dose of 1.5 mg/kg/12-hourly. Conclusion: This is the first clinical PK/PD study evaluating polymyxin B for BSI. These results will assist to optimize polymyxin B therapy and establish its breakpoints for CRKP BSI.

Polymyxin Delivery Systems: Recent Advances and Challenges

Polymyxins are vital antibiotics for the treatment of multiresistant Gram-negative ESKAPE pathogen infections. However, their clinical value is limited by their high nephrotoxicity and neurotoxicity, as well as their poor permeability and absorption in the gastrointestinal tract. This review focuses on various polymyxin delivery systems that improve polymyxin bioavailability and reduce drug toxicity through targeted and controlled release. Currently, the most suitable systems for improving oral, inhalation, and parenteral polymyxin delivery are polymer particles, liposomes, and conjugates, while gels, polymer fibers, and membranes are attractive materials for topical administration of polymyxin for the treatment of infected wounds and burns. In general, the application of these systems protects polymyxin molecules from the negative effects of both physiological and pathological factors while achieving higher concentrations at the target site and reducing dosage and toxicity. Improving the properties of polymyxin will be of great interest to researchers who are focused on developing antimicrobial drugs that show increased efficacy and safety.

NDM Metallo-β-Lactamases and Their Bacterial Producers in Health Care Settings

New Delhi metallo-β-lactamase (NDM) is a metallo-β-lactamase able to hydrolyze almost all β-lactams. Twenty-four NDM variants have been identified in >60 species of 11 bacterial families, and several variants have enhanced carbapenemase activity. Klebsiella pneumoniae and Escherichia coli are the predominant carriers of bla _NDM, with certain sequence types (STs) (for K. pneumoniae, ST11, ST14, ST15, or ST147; for E. coli, ST167, ST410, or ST617) being the most prevalent. NDM-positive strains have been identified worldwide, with the highest prevalence in the Indian subcontinent, the Middle East, and the Balkans. Most bla _NDM-carrying plasmids belong to limited replicon types (IncX3, IncFII, or IncC). Commonly used phenotypic tests cannot specifically identify NDM. Lateral flow immunoassays specifically detect NDM, and molecular approaches remain the reference methods for detecting bla _NDM Polymyxins combined with other agents remain the mainstream options of antimicrobial treatment. Compounds able to inhibit NDM have been found, but none have been approved for clinical use. Outbreaks caused by NDM-positive strains have been reported worldwide, attributable to sources such as contaminated devices. Evidence-based guidelines on prevention and control of carbapenem-resistant Gram-negative bacteria are available, although none are specific for NDM-positive strains. NDM will remain a severe challenge in health care settings, and more studies on appropriate countermeasures are required.

Recent advances and perspectives in the design and development of polymyxins

Covering: 1947-early 2017, particularly from 2005-early 2017The rise of bacterial pathogens with acquired resistance to almost all available antibiotics is becoming a serious public health issue. Polymyxins, antibiotics that were mostly abandoned a few decades ago because of toxicity concerns, are ultimately considered as a last-line therapy to treat infections caused by multi-drug resistant Gram-negative bacteria. This review surveys the progress in understanding polymyxin structure, and their chemistry, mechanisms of antibacterial activity and nephrotoxicity, biomarkers, synergy and combination with other antimicrobial agents and antibiofilm properties. An update of recent efforts in the design and development of a new generation of polymyxin drugs is also discussed. A novel approach considering the modification of the scaffold of polymyxins to integrate metabolism and detoxification issues into the drug design process is a promising new line to potentially prevent accumulation in the kidneys and reduce nephrotoxicity.