Rescuing the Last-Line Polymyxins: Achievements and Challenges

Characteristics of microplastics in typical poultry farms and the association of environment microplastics colonized-microbiota, waterfowl gut microbiota, and antibiotic resistance genes

Microplastics (MPs) pollution is a growing global environmental concern. MPs serve as ecological niches for microbial communities, which may accelerate the spread of antibiotic resistance genes (ARGs), posing risks to the breeding industry. While studies on MPs in aquatic organisms are common, research on farmed poultry is limited. This study investigates MPs in poultry farm environments and waterfowl intestines for the first time. MPs were isolated via density separation and analyzed for characterization in soil, pond water, and waterfowl intestines. Metagenomics was used to investigate the association between environment MPs colonized-microbiota and waterfowl gut microbiota. Our findings reveal that MPs are abundant in soil (6.75 ± 2.78 items/g d.w.), pond water (0.94 ± 0.28 items/g w.w.), and poultry intestines (45.35 ± 19.52 items/g w.w.), primarily appearing as fragmented particles sized 20-50 μm. MPs abundance in intestines correlates with environmental levels. Colonized-microbiota on MPs are linked to poultry intestinal microbiota, with greater diversity and microbial functions. Network analysis reveals that Corynebacterium plays a key role in MPs and poultry intestinal. Polymyxin resistance exhibits high clustering. Procrustes analysis reveals correlations between MPs, bacteria, and ARGs in the farming environment. Overall, MPs in poultry farms may facilitate pathogen and ARGs transmission, posing risks to animal gut health.

Liquid crystalline coatings loaded with colistin for preventing development of biofilms on orthopedic implants

The current antibacterial strategies focus on antibiotic therapy and extensive hygienic measures during orthopedic surgery. However, potential development of implant-associated infections remains a persistent clinical challenge. There is, therefore, a growing interest in introducing innovative safe antibacterial strategies for preventing and combating biofilm development on implants. Antibacterial coatings, particularly, are attractive for local delivery of antibacterial agents. We aim in this proof-of-concept study at introducing a novel and translatable implant coating approach, focusing on directed assembly of inverse non-lamellar lyotropic liquid crystalline (LLC) nanostructures on implants for prevention of initial bacterial attachment and biofilm formation through local delivery of the widely used cationic antibiotic colistin (COL). On exposure of dry lipid films deposited on model implants to aqueous solutions of COL prepared at different COL concentrations, a set of LLC coatings based on a commercial distilled monoglyceride product (or glycerol monooleate) were produced. In addition to small-angle X-ray scattering (SAXS) characterization investigations, in vitro studies were conducted for evaluating the antibacterial and antibiofilm properties of the LLC coatings against the Gram-negative bacteria Pseudomonas aeruginosa. The SAXS analysis indicated that all samples are inverse bicontinuous cubic Pn3m phases. Significant COL's antibacterial activity and efficient protection against bacterial adhesion were demonstrated on coating model implants with LLC surface films produced by using aqueous solutions containing COL at concentrations of 50 and 500 µg/mL. On exposure to serum, the detected structural alterations and changes in COL's antibacterial activity are also discussed. This study also highlights the implications of LLC self-assemblies for designing nanostructural coatings on orthopedic implants, which can prevent implant-associated biofilm infections through local delivery of antibacterial agents.

Research progress of LpxC inhibitor on Gram-negative bacteria

UDP-3-O-acyl-N-acetylglucosamine deacetylase (LpxC) is a metalloprotein that utilizes zinc as a cofactor. LpxC plays a crucial role in catalyzing the synthesis of Lipid A, a major component of the outer membrane lipopolysaccharide in Gram-negative (G-) bacteria, and LpxC shares no common amino acid sequence with various mammalian enzyme proteins. LpxC is essential for the survival of Gram-negative bacteria, making it a promising target for the antibacterial drug development. In recent years, numerous LpxC inhibitors have been reported, which can be broadly categorized into hydroxamic acid and non-hydroxamic acid based on their structural characteristics. Although no LpxC inhibitors are currently available on the market, several candidate small molecules are anticipated to enter clinical trials. The current manuscript offers a comprehensive review of the structures, enzyme catalytic mechanisms, and research progress of novel LpxC inhibitors, with the objective of providing insights and directions for future research in the development of LpxC inhibitors as new antibacterial agents.

Important Role of Triphenylamine in Modulating the Antibacterial Performance Relationships of Antimicrobial Peptide Mimics by Alkyl Chain Engineering

Multidrug resistance (MDR) bacteria pose a serious threat to human health, and the development of effective antimicrobial drugs is urgent. Herein, we used alkyl chain engineering to design and synthesize two series of antimicrobial peptide mimics with distinct cores: triphenylamine quaternary ammonium derivatives (TPQs) and diphenylethene quaternary ammonium derivatives (BPQs), and we investigated the effect of varying the alkyl chain lengths on antibacterial activity. We found that the introduction of a triphenylamine group significantly enhances the antibacterial activity of short-chain dimethyl quaternary ammonium derivatives while maintaining their excellent biocompatibility. Most notably, TPQ-1 exhibited negligible invasiveness toward living cells and possesses good antimicrobial activities, with good efficacy against biofilms and persisters. Moreover, TPQ-1 exhibited good antimicrobial effects in vivo and significantly accelerated the healing process of methicillin-resistant Staphylococcus aureus-infected wounds. This work promotes the practical application of antimicrobial peptide mimics and triphenylamine derivatives.

"Synergistic activity of menadione in combination with colistin against colistin-susceptible and colistin-resistant Gram-negative bacteria

Antibiotic resistance poses a formidable challenge, especially with the emergence of multidrug-resistant (MDR) Gram-negative bacteria. Colistin serves as a last-resort antibiotic to combat MDR, but it is limited by its nephrotoxicity and rising resistance. This study introduces menadione, a synthetic form of vitamin K, as a potential adjuvant to enhance colistin's efficacy against both susceptible and resistant strains of Gram-negative bacteria. Through checkerboard dilution assays, we demonstrate that menadione significantly lowers the minimum inhibitory concentrations (MICs) of colistin, with FICI ranging from 0.031 to 0.375. Furthermore, synergistic effects were confirmed via time-kill kinetics, indicating effective bacterial growth inhibition. The study also explores the mechanism underlying this synergy, revealing that menadione in combination with colistin disrupts the bacterial outer membrane, reduces the proton motive force (PMF) and ATP content, and amplify the production of reactive oxygen species (ROS), contributing to bacterial cell death. Additionally, menadione was shown to prevent the evolution of colistin resistance. This research highlights the potential of using menadione as a colistin adjuvant to combat antibiotic-resistant Gram-negative bacteria, providing a promising approach to extend the utility of existing antibiotics in clinical settings.

Population pharmacokinetics study on nebulized and intravenous administration of polymyxin B in patients with pneumonia caused by multidrug-resistant gram-negative bacteria

Polymyxin B (PMB) remains a last-line therapeutic agent for multidrug-resistant gram-negative bacteria (MDR-GNB) infections. However, reliable pharmacokinetic (PK) data to guide nebulized PMB dosing regimens in critically ill patients are limited. This study aimed to establish a population pharmacokinetic (PopPK) model for PMB in both epithelial lining fluid (ELF) and plasma of critically ill patients with MDR-GNB pneumonia and to optimize dosing regimens. A prospective PK study was conducted in 76 adult patients receiving nebulized PMB either as monotherapy or in combination with intravenous administration. PK data were analyzed using non-linear mixed-effect modeling, with PMB concentration-time profiles described by a coupled model integrating separate two-compartment models for plasma and ELF. The final model identified albumin levels and age as significant covariates influencing PK variability. Monte Carlo simulations demonstrated that nebulization therapy either alone or combined with intravenous administration significantly enhances ELF concentration and the probability of target attainment. Additionally, Pseudomonas aeruginosa requires higher nebulized doses than Klebsiella pneumoniae and Acinetobacter baumannii. This study develops a PopPK model of PMB in ELF and plasma, providing critical insights to optimize PMB treatment strategies for patients with MDR-GNB pneumonia.

Omp34-Mediated Acinetobacter baumannii Invasion of Human Cervical Carcinoma Epithelial, HeLa Cells, and the Influence of Anti-Omp34 Antibodies

Acinetobacter baumannii is known for its ability to invade and persist within eukaryotic cells, impacting infection outcomes and disease progression. This study investigates the role of Omp34, a key outer membrane protein (Omp), in A. baumannii interaction with epithelial cells and the protective effects of anti-Omp34 antibodies (Abs). Omp34 is a key regulator of A. baumannii epithelial cell invasion, influencing bacterial adherence, internalization, and intracellular proliferation. The presence of anti-Omp34 Abs mitigates A. baumannii-induced cellular damage and enhances bacterial clearance. The process involved the expression and purification of Omp34, which in turn induced Abs in BALB/c mice against Omp34. The acute toxicity of Omp34 was studied through a histological analysis conducted on six distinct organs in mice. HeLa cells were infected by A. baumannii ATCC 19606 and a clinical strain. Various aspects of A. baumannii behavior with HeLa cells, including HeLa cell viability, adherence, serum resistance, cell internalization, and intracellular proliferation with and without anti-Omp34 sera. Cytoskeleton inhibitors were used to study the potential roles played in the process of A. baumannii invasion by microfilaments and microtubules. Omp34 effectively triggered Ab production in mice without resulting in any toxicity. The assay for serum resistance revealed potent bactericidal and antibiofilm effects on both A. baumannii strains. Bacterial internalization was constrained when actin polymerization was inhibited. Examination under the microscope revealed instances of adherence, alterations in the cell membrane, apoptosis, vacuolization, and cell damage. HeLa cells exposed to anti-Omp34 serum showed decreased cell damage. The results provide substantial evidence of the adherence capacity of A. baumannii to proliferate in the epithelial cells. In conclusion, Omp34 plays a substantial role in regulating interactions between epithelial cells and A. baumannii, the multifaceted nature of which intricately modifies the trajectory of infection within host cells by A. baumannii.

Synchronous Sterilization and Immunoreaction Termination for Corneal Transparency Protection in Treating Pseudomonas aeruginosa Induced Bacterial Keratitis

In the treatment of infectious keratitis, therapeutic strategies often prioritize enhancing bactericidal efficacy. However, endotoxins released from Gram-negative bacteria cause inflammatory reaction, leading to corneal structural damage and scar formation. Given that polymyxin B (PMB) can bind and neutralize lipopolysaccharide (LPS), this study employs large-pore mesoporous silica nanoparticles (lMSNs) grafted with PMB as carriers for cationic antibacterial carbon quantum dots (CQDs) to prepare CQD@lMSN-PMB, which enables synchronous sterilization and endotoxin neutralization. In the acidic infectious microenvironment, the accelerated release of CQDs eliminates 99.88% bacteria within 2 h, effectively substituting immune mediated sterilization. Notably, CQD@lMSN-PMB exhibits exceptional LPS neutralization performance (2.22 µg LPS/mg CQD@lMSN-PMB) due to its high specific surface area. In an infectious keratitis model, inflammation subsides significantly within the first day of CQD@lMSN-PMB intervention and is completely resolved by day 3. By day 2, interleukin-1β, interleukin-6 and tumor necrosis factor-α in CQD@lMSN-PMB group decrease by 86.99%, 91.15%, and 77.56%, respectively, compared to the CQDs-only sterilization group. Ultimately, corneal integrity and transparency are preserved, with suppressed expressions of fibrosis-related factors including matrix metalloproteinase 9, transforming growth factor-β and α-smooth muscle actin. Therefore, this synchronous sterilization and endotoxin neutralization strategy outperforms monotherapy strategies focused solely on sterilization or endotoxin neutralization.

Inhaled pH-Responsive polymyxin B-loaded albumin nanoparticles against pneumonia caused by carbapenem resistant Klebsiella pneumoniae

The pneumonia induced by carbapenem resistant Klebsiella pneumoniae (CRKP) has high morbidity and mortality. Among the antibiotics currently available, polymyxin B (PMB) is considered to be the last line of defense. Routine intravenous administration of PMB has many problems, such as severe neurotoxicity and nephrotoxicity. In this study, a novel inhaled PMB-loaded albumin nanoparticles (PEG-pHSA@PMB) capable of penetrating airway mucus and responding to the infection microenvironment is constructed. An acid-responsive functional molecule (PEBA) and NH2-PEG-SH are linked to the surface of human serum albumin (HSA) via the conjugation reaction. Subsequently, PMB is loaded through electrostatic interactions to yield PEG-pHSA@PMB. The sulfhydryl groups of PEG-pHSA@PMB interact with mucins to help penetrate mucus after inhaled. In an acidic environment, the protonation of the tertiary amino groups within PEG-pHSA@PMB causes the charge alteration, which leads to the release of PMB. It demonstrated excellent mucus permeability, potent bactericidal activity, and superior bacteriostatic effects compared to sole PMB. Inhalation of PEG-pHSA@PMB significantly reduced the bacterial load in the lungs of mice with CRKP pneumonia, alleviating inflammatory response. Moreover, PEG-pHSA@PMB exhibited good cytocompatibility and biosafety. The novel strategy of the inhalation drug delivery system is promising for the treatment of pneumonia caused by drug-resistant bacteria.

Revisiting therapeutic options against resistant klebsiella pneumoniae infection: Phage therapy is key

Multi-drug resistant and carbapenem-resistant hypervirulent Klebsiella pneumoniae strains are spreading globally at an alarming rate, emerging as one of the most serious threats to global public health. The formidable challenges posed by the current arsenal of antimicrobials highlight the urgent need for novel strategies to combat K. pneumoniae infections. This review begins with a comprehensive analysis of the global dissemination of virulence factors and critical resistance profiles in K. pneumoniae, followed by an evaluation of the accessibility of novel therapeutic approaches for treating K. pneumoniae in clinical settings. Among these, phage therapy stands out for its considerable potential in addressing life-threatening K. pneumoniae infections. We critically examine the existing preclinical and clinical evidence supporting phage therapy, identifying key limitations that impede its broader clinical adoption. Additionally, we rigorously explore the role of genetic engineering in expanding the host range of K. pneumoniae phages, and discuss the future trajectory of this technology. In light of the 'Bad Bugs, No Drugs' era, we advocate leveraging artificial intelligence and deep learning to optimize and expand the application of phage therapy, representing a crucial advancement in the fight against the escalating threat of K. pneumoniae infections.

Unraveling Neurotoxicity Discrepancies: Comparative In vitro and In vivo Analysis of Colistin and Polymyxin B and the Underlying Mechanisms

Polymyxins, including colistin and polymyxin B, are the final resort against Gram-negative bacterial infections. However, its clinical application is restricted due to concerns related to neurotoxicity. Despite the similar antibacterial spectrum and mode of action shared between colistin and polymyxin B, there is still a lack of definitive evidence to support the idea that their neurotoxicity profiles are identical. To comprehensively compare the neurotoxicity between colistin and polymyxin B both in vivo and in vitro and establish a theoretical foundation to guide the rational use of polymyxins within clinical settings. in vitro experiments simulated nerve damage by exposing N2a and RSC96 cells to colistin and polymyxin B. The evaluation of nerve injury included assessments of cell viability and apoptosis. To discern the variance in the mechanisms of nerve injury between colistin and polymyxin B, oxidative stress levels were examined, such as SOD, CAT, GSH, and malondialdehyde (MDA). In in vivo experiments, a rat nerve injury model was created by intraventricular injections of colistin and polymyxin B, respectively. The impact of these drugs on brain injury in rats, particularly within the hippocampus and medulla oblongata, was measured using HE and Nissl staining. The potential influence of polymyxins on the ferroptosis pathway was evaluated by assessing LPO and Fe2+ levels and the degree of mitochondrial impairment. At equivalent doses, colistin demonstrated a reduced level of neurotoxicity compared to polymyxin B, both in vitro and in vivo. in vitro experiments revealed greater cell viability and a lower apoptosis rate after colistin treatment than after polymyxin B treatment. This variance in outcomes could be attributed to the comparatively lower levels of oxidative stress associated with colistin administration. In a rat model, nerve injury resulted in observable damage to both the hippocampus and the medulla oblongata. A comprehensive assessment of the extent of damage in the CA1 to CA4 regions of the hippocampus, and the solitary tract nucleus of the medulla oblongata underscored that the neurotoxic effects of colistin remained milder compared to those elicited by polymyxin B. Even when evaluated at equivalent multiples of clinically recommended doses, colistin exhibited lower neurotoxicity in vivo than polymyxin B. For the first time, this study demonstrated the role of ferroptosis in polymyxin B-induced nerve damage. The activation levels observed within the ferroptosis pathway due to polymyxin B exceeded those triggered by colistin. Colistin exhibited a marked reduction in neurotoxicity compared to polymyxin B, evident in both the equivalent and clinically recommended doses. These findings suggest that, from the perspective of neurotoxicity, colistin presents a more favorable option for clinical use.

Analysis and comparison of adverse events of colistin administered by different routes based on the FAERS database

OBJECTIVE

To analyze and compare the incidence of adverse events (AEs) associated with different administration routes of colistin, with the aim of providing a reference for its safe and effective clinical use.

METHODS

Adverse event (AE) reports related to colistin were retrieved from the FDA Adverse Event Reporting System (FAERS) database. The reporting trends were analyzed, and the Reporting Odds Ratio (ROR) and Proportional Reporting Ratio (PRR) for colistin-associated AEs were calculated. A comparative analysis was conducted to examine the occurrence of AEs under different administration routes of colistin.

RESULTS

A total of 13,043 AE reports were extracted from the FAERS database. Further analysis of 176 key AEs associated with colistin indicated a significant increase in the number of reports after 2021. The year and country of the reports showed heterogeneity across different administration routes. Intravenous (IV) administration of colistin was associated with the highest proportion of AEs, and heterogeneity was also observed in the types of AEs reported for inhaled and oral (PO) administration routes.

CONCLUSION

Compared to inhaled and PO administration routes, IV administration of colistin is more likely to result in AEs such as nephrotoxicity and drug ineffectiveness. Additionally, there are significant differences in the types of AEs associated with colistin across different administration routes.

The efficacy of polymyxin B in treating stroke-associated pneumonia with carbapenem-resistant Gram-negative bacteria infections: a multicenter real-world study using propensity score matching

Objectives

Infection with Carbapenem-resistant Gram-negative bacteria (CR-GNB) poses further challenges in treating stroke-associated pneumonia (SAP) patients. This multicenter retrospective study aimed to evaluate the efficacy of polymyxin B (PMB) in CR-GNB-infected SAP patients and to identify factors that may influence its effectiveness.

Methods

From 1 September 2019, and 30 December 2022, a total of 196 CR-GNB-infected SAP patients from five hospitals in China were included in the study based on specific criteria. Demographics and clinical data were obtained from the electronic medical records. Propensity score matching (PSM) was used to minimize the effect of potential confounding variables. Univariate analysis and multivariate logistic analysis were performed to identify risk factors affecting microbial efficacy.

Results

Among the 196 SAP patients infected with CR-GNB, 24.5% received PMB combined inhalation and 75.5% received non-combined inhalation treatment. The clinical success rate was 68.9%, with 25.5% achieving microbial efficacy within 7 days and 37.8% achieving microbial cure. The 30-day all-cause mortality rate was 14.8%. The incidence of acute kidney injury was 34.7%. After adjustment by propensity score matching, the PMB combined inhalation group exhibited significantly higher microbial efficacy compared to the non-combined inhalation group (46.7% vs. 26.7%, p = 0.049). Multivariate logistic analysis identified multi-site infections and Carbapenem-resistant Pseudomonas aeruginosa infection as independent risk factors for microbial efficacy.

Conclusion

Combined inhalation of PMB demonstrated superior effectiveness in microbial clearance compared to non-combined inhalation in treating CR-GNB-infected SAP patients. We recommend aerosol combined inhalation of PMB and suggest developing personalized PMB-based regimens for individual patients to enhance treatment outcomes.

Vitamin B6 resensitizes mcr-carrying Gram-negative bacteria to colistin

Antimicrobial resistance poses a severe threat to human health, with colistin serving as a critical medication in clinical trials against multidrug-resistant Gram-negative bacteria. However, the efficacy of colistin is increasingly compromised due to the rise of MCR-positive bacteria worldwide. Here, we reveal a notable metabolic disparity between mcr-positive and -negative bacteria through transcriptome and metabolomics analysis. Specifically, pyridoxal 5'-phosphate (PLP), the active form of vitamin B6, was significantly diminished in mcr-positive bacteria. Conversely, supplementing with PLP could reverse the metabolic profile of drug-resistant bacteria and effectively restore colistin's bactericidal properties. Mechanistically, PLP was found to augment bacterial proton motive force by inhibiting the Kdp transport system, a bacterial K+ transport ATPase, thereby facilitating the binding of the positively charged colistin to the negatively charged bacterial membrane components. Furthermore, PLP supplementation triggers ferroptosis-like death by accumulating ferrous ions and inducing lipid peroxidation. These two modes of action collectively resensitize mcr-harboring Gram-negative bacteria to colistin therapy. Altogether, our study provides a novel metabolic-driven antibiotic sensitization strategy to tackle antibiotic resistance and identifies a potentially safe antibiotic synergist.

Insertion sequences in mgrB and mutations in two-component system genes confer high polymyxin resistance to carbapenem-resistant Enterobacter cloacae complex strains

Due to the complexity of identifying the Enterobacter cloacae complex (ECC) at the species level, little is known about the distribution of carbapenem-resistant ECC (CRECC). Plasmid-mediated mcr family genes are significant contributors to polymyxin resistance. The emergence of the mcr-9 gene has further complicated the landscape of polymyxin resistance in CRECC. Our study aimed to ascertain the prevalence of CRECC and the mcr-9 gene, and to elucidate the mechanisms underlying high-level resistance to polymyxin B (PB). In this study, we collected 212 non-replicating ECC strains, identifying 38 CRECC strains (17.9%, 38/212) and Enterobacter hormaechei (71.1%, 27/38) as the predominant endemic strains. Among these, 10 CRECC strains (36.3%, 10/38) were found to harbor the mcr-9 gene. Interestingly, the presence of mcr-9 did not significantly impact PB resistance or impose a fitness cost. While overexpression of mcr-9 can enhance PB resistance within a certain range and may incur fitness costs, it does not result in high-level PB resistance. The PB resistance of 17 CRECC strains was notably increased (from 16 to 128 mg/L), accompanied by mutations in the phoP/Q and mgrB genes. Notably, two novel insertion sequences, IS5D and IS1X2, were discovered within the mgrB gene. The inactivation of mgrB results in the loss of its negative regulatory effect on the two-component system. Protein structure predictions indicated that mutations in phoQ primarily affect the phosphatase (HAMP) and histidine kinase domains. This research significantly expands our comprehension of the complexities of PB resistance, highlighting the multifactorial nature of antibiotic resistance mechanisms.

Increasing polymyxin resistance in clinical carbapenem-resistant Klebsiella pneumoniae strains in China between 2000 and 2023

BACKGROUND

Development of polymyxin resistance in carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a severe challenge to public health. Here we aimed to perform a retrospective study of prevalence and molecular characteristics of polymyxin-resistant CRKP strains.

METHODS

4455 clinical CRKP strains from 18 provinces in China during 2000 to 2023 were collected. Polymyxin-resistant CRKP strains were subjected to antimicrobial susceptibility testing, whole genome sequencing and bioinformatic analysis. Molecular mechanisms underlying the polymyxin resistance in CRKP were analyzed.

RESULTS

Here we show that polymyxin-resistant CRKP emerge initially in 2014, prevalence of such strains then increase steadily over the years, reaching a rate of 9.86% in 2023. In total, 112 polymyxin-resistant CRKP isolates are identified. Antimicrobial susceptibility tests show that all polymyxin-resistant CRKP are resistant to commonly used antibiotics, yet most isolates remain susceptible only to ceftazidime-avibactam and tigecycline. Predominant polymyxin resistance mechanism in CRKP is mutations in mgrB (59/112), which commonly involves disruption of mgrB by insertion of elements such as ISKpn26 (20/59), IS903B (14/59), and ISKpn14 (9/59). Phylogenetic analysis reveals frequent clonal dissemination of polymyxin-resistant CRKP within the same hospital and even among different hospitals in neighboring provinces. pLVPK-like virulence plasmids are detected in 46 isolates, such strains are therefore categorized as polymyxin and carbapenem-resistant hypervirulent K. pneumoniae which may cause infections with high mortality.

CONCLUSIONS

Our results highlight frequent clonal transmission of polymyxin-resistant CRKP within hospitals. Continuous surveillance of polymyxin resistance among CRKP should be implemented to prevent further dissemination of such strains in clinical settings in China.

Clinical characteristics, molecular epidemiology and mechanisms of colistin heteroresistance in Enterobacter cloacae complex

Introduction

Colistin has emerged as the last resort for treating multidrug-resistant Enterobacter cloacae complex (ECC) infections. The primary purposes of this study were to demonstrate the presence of colistin heteroresistance in ECC and to further investigate their clinical characteristics, molecular epidemiology and mechanisms.

Methods

Population analysis profiles (PAP) were performed to confirm the heteroresistance phenotype. Average nucleotide identity (ANI) was determined to classify ECC species. Phylogenetic analysis based on core genome single nucleotide polymorphisms (cg-SNPs), multilocus sequence typing (MLST) and core genome MLST (cg-MLST). Risk factors and clinical outcomes of infections were analyzed through a retrospective case-control study. Potential mechanisms of colistin heteroresistance were evaluated using polymerase chain reaction (PCR), efflux pump inhibition assays and reverse transcription quantitative PCR (RT-qPCR).

Results

A high proportion (24.4%) of the non-resistant strains were colistin-heteroresistant isolates. Among the several ECC species, Enterobacter kobei had the largest percentage (29.4%) of colistin-heteroresistant isolates, followed by Enterobacter hormaechei (20.5%) and Enterobacter bugandensis (20.0%). Notably, only one strain (0.8%; 1/132) of Enterobacter hormaechei was fully resistant to colistin. Different ECC species showed varying heteroresistance levels: Enterobacter roggenkampii, Enterobacter kobei, Enterobacter asburiae and Enterobacter bugandensis displayed high heteroresistance levels  (MIC ≥ 128 mg/L). 75% of all ST116 and ST56 strains were heteroresistant to colistin. The infection of ST116 and ST56 strains as well as exposure to cephalosporin antibiotics were independent risk factors for colistin-heteroresistant ECC infections. Mechanistic analysis revealed that heteroresistance strongly correlated with the overexpression of arnA, regulated by the PhoPQ two-component system (TCS). Notably, mgrB had minimal impact. AcrAB-TolC efflux pump genes showed unsynchronized expression; High acrB expression was strongly associated with colistin heteroresistance, while acrA and tolC were not.

Discussion

Colistin heteroresistance showed species-dependent variations in levels and prevalence rates. The colistin-heteroresistant mechanisms were complex, involving coordinated regulation of multiple genes. These results highlighted the need for tailored antimicrobial stewardship. In addition, the development of direct, reliable and rapid clinical methods for detecting heteroresistance is essential for improving infection management and prevention.

Preventable serious drug-disease interactions of reserve antibiotics

INTRODUCTION

Antibiotics that are used exclusively in hospital settings and reserved for treating infections caused by multidrug-resistant or extended-resistant bacterial pathogens are referred to as 'reserved' antibiotics. The purpose of this review article is to provide a better understanding of the risks associated with serious interactions between reserved antibiotics and various diseases, as well as to present key strategies for their prevention.

AREAS COVERED

The literature search was conducted in the MEDLINE, SCOPUS, EBSCO, and GOOGLE SCHOLAR databases without any restrictions on time or language. Only clinical studies, observational human studies, case reports, and case series that reported serious drug-disease interactions were considered.

EXPERT OPINION

Knowledge of the interactions between reserve antibiotics and diseases, that have actually occurred and then been described in the medical literature, is crucial to the safe treatment of critically ill patients with infections caused by multidrug-resistant bacterial strains. Introducing into routine practice the checking of possible interactions with diseases that a patient suffers from, strict monitoring of changes in the function of the excretory organs (kidneys and liver), and measuring the concentration of drugs in the plasma will reduce the possibility of adverse drug-disease interactions.

The hidden threat: Klebsiella pneumoniae may develop co-resistance to colistin and cefiderocol under pressure of colistin

OBJECTIVES

Carbapenem-resistant Klebsiella pneumoniae (CRKP) has become a global concern owing to its difficult treatment. This study aimed to determine the impact of colistin resistance on susceptibility to cefiderocol.

METHODS

The colistin-susceptible clinical strain CRKP12-130 (colistin minimum inhibitory concentration [MIC] 0.5 mg/L) was cultured in medium containing 4× and 8× the MIC of colistin. Eight colistin-resistant derivatives were randomly selected for susceptibility testing of cefiderocol and zeta potential changes. To compare the impact of colistin resistance on bacterial uptake of iron, growth curve experiments were conducted in cation-adjusted Mueller-Hinton broth (CAMHB) and iron-depleted CAMHB (ID-CAMHB). Resistant strains and the original strain CRKP12-130 were subjected to next-generation sequencing.

RESULTS

Colistin MICs ranged from 16 to 128 mg/L for the eight colistin-resistant derivatives. The key genetic variants identified in colistin-resistant strains involved insertions and deletions in mgrB, and missense mutations in pmrB and phoQ. The colistin-resistant derivatives also exhibited reduced susceptibility to cefiderocol, with MICs increasing from 1 mg/L to 2-8 mg/L. Additionally, colistin-resistant strains demonstrated higher zeta potentials, ranging from -45.2 mV to levels between -32.8 mV and -14.2 mV. Resistant strains showed a more significant decrease in growth rate when cultivated in ID-CAMHB medium.

CONCLUSION

This study investigated the phenomenon of co-resistance to colistin and cefiderocol in CRKP under pressure of colistin. The simultaneous decrease in susceptibility poses a potential threat to the efficacy of clinical treatment of CRKP infections.

Deciphering antibiotic resistance genes and plasmids in pathogenic bacteria from 166 hospital effluents in Shanghai, China

Although previous studies using phenotypic or metagenomic approaches have revealed the patterns of antibiotic resistance genes (ARGs) in hospital effluents in local regions, limited information is available regarding the antibiotic resistome and plasmidome in human pathogenic bacteria in hospital effluents of megacity in China. To address this knowledge gap, we analyzed effluent samples from 166 hospitals across 13 geographical districts in Shanghai, China, using both cultivation-based approaches and metagenomics. A total of 357 strains were isolated from these samples, with the predominant species being Escherichia coli (n = 61), Aeromonas hydrophila (n = 57), Klebsiella pneumoniae (n = 48), and Aeromonas caviae (n = 42). Those identified indicator bacteria were classified into biosafety level 1 (BSL-1, 60 %) and BSL-2 (40 %). We identified 1237 ARG subtypes across 22 types, predominantly including beta-lactam, tetracycline, multidrug, polymyxin, and aminoglycoside resistance genes, using culture-enriched phenotypic metagenomics. Mobile genetic elements such as plasmids, transposons (tnpA), integrons (intI1), and insertion sequences (IS91) were abundant. We recovered 135 plasmids classified into mobilizable (n = 94) and non-mobilizable (n = 41) types. Additionally, 80 metagenome-assembled genomes (MAGs) were reconstructed from the hospital effluents for the assessment of ARG transmission risks, including genes for last-line antibiotics such as blaNDM, blaKPC, blaimiH, and mcr. This study is the first to comprehensively characterize and assess the risk of antimicrobial resistance levels and plasmidome in the hospital effluents of China's megacity, providing city-wide surveillance data and evidence to inform public health interventions.

Toxicokinetic profiling of VRP-034: Evaluating its potential in mitigating polymyxin-B-associated nephrotoxicity

This study assessed the nephrotoxicity and toxicokinetic profile of VRP-034 [a novel formulation of polymyxin B (PMB)] compared with marketed PMB over a 7-day repeat-dose regimen. Three objectives were pursued: evaluating PMB pharmacokinetics in both groups, alongside assessing the impact of VRP-034 on mitigating PMB-associated kidney injury; analysing the reversibility of kidney injury; and validating novel kidney injury biomarkers against traditional markers using histopathological scoring. Sixty-eight Sprague-Dawley rats were divided into three groups: 30 in each of the marketed PMB and VRP-034 groups, and eight in the control group. Rats received drugs at 6 mg/kg subcutaneously every 8 h (human equivalent dose ∼3 mg/kg/day). Toxicokinetic evaluations were conducted on selected animals on days 1, 2, 4, and 7 (after 3rd, 6th, 12th and 21st dose), while the remaining animals were observed for an additional 7 days without treatment. Samples were collected up to 12 h post-administration, followed by necropsy and histopathological examination. Plasma PMB concentrations were quantified; and kidney injury biomarkers, oxidative stress and anti-inflammatory markers were evaluated. Receiver operating characteristic curve analysis was performed to validate kidney injury biomarkers against histopathological grading. Similar plasma PMB concentrations and pharmacokinetic parameters were found in the two treatment groups. However, the VRP-034 group exhibited significantly lower nephrotoxicity, with reduced levels of kidney injury biomarkers, and diminished oxidative stress and inflammation levels compared with the marketed PMB group. Histopathological examination confirmed reduced renal damage in the VRP-034 group. Novel kidney injury biomarkers demonstrated superior sensitivity, specificity and early detection capability over traditional markers. In conclusion, VRP-034 demonstrated reduced nephrotoxicity compared with marketed PMB, suggesting its potential as a safer alternative.

Aerosolized plus intravenous polymyxin B in comparison to intravenous polymyxin B alone for the management of HAP caused by carbapenem-resistant gram-negative bacteria: A prospective multicenter cohort study

OBJECTIVES

This study aimed to evaluate the clinical effectiveness of combined aerosolized (AER) and intravenous (IV) polymyxin B in managing patients with hospital-acquired pneumonia (HAP) caused by carbapenem-resistant gram-negative organism (CRO).

METHODS

This multicenter prospective cohort study was conducted across six intensive care units in municipal and above-municipal hospitals in Shaanxi, China, from January 1, 2021 to December 31, 2022. Patients with CRO pneumonia were categorized into the intravenous group (IV polymyxin B alone) and the combination group (AER plus IV polymyxin B). Primary outcomes included ICU mortality, 28-day mortality and bacterial clearance, while secondary outcomes included the duration of mechanical ventilation and length of ICU stay.

RESULTS

A total of 64 patients were included in the study, with 29 receiving AER plus IV polymyxin B and 35 receiving IV polymyxin B alone. On the seventh day of treatment, the combination group showed a significant reduction in the APACHE II score (17.86 ± 5.03 vs. 19.17 ± 11.02, P = 0.041) and procalcitonin levels (1.27 ± 0.20 vs. 3.18 ± 0.69, P < 0.001) compared to the intravenous group. Additionally, the combination group exhibited a higher bacterial eradication rate (62.1% vs. 42.9%), lower ICU mortality (27.6% vs. 37.1%), shorter duration of mechanical ventilation (371.39 ± 68.97 h vs. 563.94 ± 100.25 h), and reduced ICU stay (34.41 ± 17.87 d vs. 35.03 ± 21.66 d), although the differences were not statistically significant.

CONCLUSIONS

In patients with CRO pneumonia, combination therapy resulted in significant reductions in APACHE II scores and procalcitonin, but did not lead to statistically significant improvements in clinical outcomes, compared to IV polymyxin B alone.

Advances and mechanisms of traditional Chinese medicine and its active ingredients against antibiotic-resistant Escherichia coli infections

In clinical practice, antibiotics have historically been utilized for the treatment of pathogenic bacteria. However, the gradual emergence of antibiotic resistance among bacterial strains has posed a significant challenge to this approach. In 2022, Escherichia coli, a Gram-negative bacterium renowned for its widespread pathogenicity and high virulence, emerged as the predominant pathogenic bacterium in China. The rapid emergence of antibiotic-resistant E. coli strains has rendered antibiotics insufficient to fight E. coli infections. Traditional Chinese medicine (TCM) has made remarkable contributions to the health of Chinese people for thousands of years, and its significant therapeutic effects have been proven in clinical practice. In this paper, we provide a comprehensive review of the advances and mechanisms of TCM and its active ingredients against antibiotic-resistant E. coli infections. First of all, this review introduces the classification, antibiotic resistance characteristics and mechanisms of E. coli. Then, the TCM formulas and extracts are listed along with their active ingredients against E. coli, including extraction solution, minimum inhibitory concentration (MIC), and the antibacterial mechanisms. In addition, there is growing evidence supporting the synergistic therapeutic strategy of combining TCM with antibiotics for the treatment of antibiotic-resistant E. coli infections, and we provide a summary of this evidence and its underlying mechanisms. In conclusion, we present a comprehensive review of TCM and highlight its potential and advantages in the prevention and treatment of E. coli infections. We hold the opinion that TCM will play an important role in global health, pharmaceutical development, and livestock farming in the future.

Poor Glycemic Control in Carbapenem-Resistant Klebsiella pneumoniae Infections: Impact on Epidemiological Features, Mortality Risks, and Polymyxin Resistance

Purpose

This study aims to investigate the relationship between glycemic control and epidemiological characteristics of patients infected with carbapenem-resistant Klebsiella pneumoniae (CRKP), to identify mortality risk factors associated with CRKP infection, and to evaluate the impact of glucose on the resistance of CRKP to polymyxin and serum killing.

Patients and Methods

Clinical cases of 218 patients infected with CRKP were collected from a large tertiary public hospital in Anhui Province. We analyzed whether the glycemic control impacts the clinical and laboratory manifestations of infected patients. Logistic regression identified mortality risk factors. Antibiotic sensitivity, capsular serotypes, and virulence genes were tested of the strains. Three clinically isolated CRKP strains were used to investigate the effect of glucose on bacterial capsule synthesis and the impact on bacterial resistance to polymyxin and serum killing.

Results

Patients with poor glycemic control experienced more severe infections and had a higher likelihood of chronic kidney disease (CKD) and acute renal insufficiency compared to those with good glycemic control. They also exhibited an increased mortality rate. Logistic regression analysis identified age, glycosylated hemoglobin (HbA1c) ≥7%, CKD, tumor, mechanical ventilation, and sepsis as independent risk factors for death associated with CRKP infection. A 0.5% (0.5 g/100mL) glucose environment can stimulate CRKP capsule synthesis, which is inhibitable by cyclic adenosine monophosphate (cAMP). Moreover, a high-glucose environment can enhance CRKP's resistance to polymyxin and serum killing.

Conclusion

A persistent hyperglycemic environment resulting from poor glycemic control may stimulate the synthesis of CRKP capsules, which could enhance the resistance of CRKP to polymyxin and serum killing, thereby further increasing the risk of patient mortality.

Whole-genome evaluation and prophages characterization associated with genome of carbapenem-resistant Acinetobacter baumannii UOL-KIMZ-24-2

Carbapenem-resistant Acinetobacter baumannii (CRAB) is an emerging threat to healthcare settings in many countries, principally in South Asia. The current study was aimed to identify, evaluate whole-genome and characterize the prophages in genome of CRAB strain, recovered from patients of Lahore General Hospital, Lahore. More than 200 samples were collected and identified by morphological and biochemical tests. These strains were also subjected to a comprehensive antimicrobial susceptibility evaluation using Kirby-Bauer method and further confirmed as CRAB strains by exploring blaOXA-51. In addition, the whole-genome evaluation of a Acinetobacter baumannii UOL-KIMZ-24-2 was carried out using various Bioinformatics tools. A total of 150 strains of A. baumannii were recovered and identified in the current study. Among them, 49% strains were found resistant to carbapenem. The blaOXA-51 was found prevalent in the genome of A. baumannii recovered from medical ICU (38%). In addition, the UOL-KIMZ-24-2 genome analysis based on multilocus sequence typing (MLST) highlighted that UOL-KIMZ-24-2 belonged to ST2 (Pasteur scheme) sequence type. A total of 29 antimicrobial resistance (AMR) genes were present, importantly, blaOXA-66, blaOXA-23 and blaOXA-25. The mobile genetic elements (MGEs) were identified as transposases and belonged to four classes e.g. IS15d1, ISAba24, ISEc29, and ISEc35. A total of 14 virulence factors encoded by 58 different genes were detected in UOL-KIMZ-24-2. In addition, the phage sequences were identified in genome of UOL-KIMZ-24-2, divided into 3 regions. In conclusion, UOL-KIMZ-24-2 contained a mixture of AMR genes, MGEs. prophages sequences and virulence genes.

LTX-315 is a novel broad-spectrum antimicrobial peptide against clinical multidrug-resistant bacteria

INTRODUCTION

Infections stemming from multidrug-resistant bacteria present a substantial threat to public health today. Discovering or synthesizing novel compounds is crucial to alleviate this pressing situation.

OBJECTIVE

The main purpose of this study is to verify the antibacterial activity of LTX-315 and explore its primary action mode.

METHODS

Through antibacterial phenotype assay screening, we obtained a potent compound named LTX-315 from diverse drug libraries, 10,926 compounds in total. Then, the bactericidal effect and its action mode were explored through biochemical and chemistry methods such as atime-killing curve, scanning electronic microscopy, isothermal titration calorimetry analysis, and nuclear magnetic resonance. Finally, the efficacy in vivo of LTX-315 against drug-resistant bacteria was proved through amice infection model.

RESULTS

In this study, LTX-315, an oncolytic peptide, was discovered to effectively eliminate gram-positive and gram-negative pathogens, even for those multidrug-resistant strains. Through strong electrostatic interactions, LTX-315 can bind to the membrane component phosphatidylglycerol (PG) with extremely high affinity (nanomolar level). Strikingly, in contrast to the typical electrostatic interactions of antibacterial peptides, the indole group of LTX-315, situated near the alkyl chain, exhibits significantly enhanced recognition and interaction with PG due to the hydrophobic effect of the alkyl chain. Furthermore, it exerts various impacts on cell membranes, including damaging integrity, increasing permeability, and decreasing membrane fluidity. Additionally, microscopy revealed significant cell disintegration. The influence, in turn, disrupts several physiological activities inside cells, such as increasing the reactive oxygen species level, ultimately leading to cell death. Finally, the efficacy of LTX-315 in vivo against multidrug-resistant and hypervirulent Klebsiella pneumoniae was demonstrated.

CONCLUSION

The unique mechanism of LTX-315 involves high-affinity binding to PG and subsequent membrane disruption, providing a novel approach against multidrug-resistant bacteria compared to conventional antibiotics. As a potential candidate, it shows promise in effectively treating bacterial infections, particularly those caused by drug-resistant bacteria, thereby addressing the escalating challenge of antibiotic resistance worldwide.

Efficacy, safety, and therapeutic drug monitoring of polymyxin B sulfate and colistin sulfate in critically ill patients: a real-world retrospective study

Background

Polymyxin B sulfate (PBS) and colistin sulfate (CS) are the last-line treatments for infections caused by multidrug-resistant Gram-negative bacteria, but their efficacy and safety have not been validated. The aims of the current study were to (1) determine their efficacy and safety among critically ill patients and the influencing factors, and (2) determine the relationships of drug exposure with efficacy and safety, to provide evidence for the precision dosing.

Method

This retrospective study included 100 critically ill patients treated with PBS and 80 treated with CS. The efficacy outcomes were clinical efficacy and 30-day mortality, while the safety indicator was acute kidney injury (AKI) incidence.

Result

There was no significant difference between the two drugs in clinical efficacy, 30-day mortality, or overall AKI incidence, but the incidence of stage 3 AKI was significantly higher in the PBS cohort than the CS cohort. Therapeutic drug monitoring (TDM) and trough concentration (Cmin) were significantly associated with clinical efficacy and AKI in both cohorts. Classification and regression tree analysis revealed that Cmin values of ≥0.91 mg/L for PBS and Cmin ≥ 0.53 mg/L for CS were associated with higher clinical efficacy.

Conclusion

There is basically no significant difference in the efficacy and safety of PBS and CS. TDM can significantly improve the clinical efficacy of both drugs and reduce the incidence of AKI. TDM is therefore recommended to improve the clinical efficacy while reducing the adverse reactions.

A pharmacovigilance study of adverse events associated with polymyxins based on the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS) database

BACKGROUND

Polymyxins have been regarded as last-line treatment for multidrug-resistant gram-negative bacterial infections. Nonetheless, concerns regarding toxicity persist. This study aimed to explore and compare potential adverse events (AEs) between colistin and polymyxin B (PMB).

METHODS

Polymyxins-related AEs were retrieved from the U.S. Food and Drug Administration Adverse Event Reporting System between 2004 and 2022. Potential signals were estimated by the reporting odds ratio (ROR), and subgroup analyses were preformed to adjust for potential factors in AEs with significant disproportionality.

RESULTS

Analysis of 3,915 records involving 718 patients revealed a higher disproportionality of renal and urinary disorders (ROR 1.62, 95% CI 1.01-2.59) and acute kidney injury (ROR 1.75, 95% CI 1.07-2.87) with colistin treatment. Conversely, colistin exhibited a lower risk for neurotoxicity (ROR 0.47, 95% CI 0.30-0.73). Seven cases of skin hyperpigmentation were reported with PMB, whereas none were reported with colistin. Over 80% of cases involving polymyxin-related AEs occurred during the first two weeks of therapies, with a median onset time of 4.5 days.

CONCLUSIONS

Patients received colistin displayed a higher potential risk of nephrotoxicity but a lower risk of neurotoxicity. Clinicians should be vigilant in monitoring the AEs of hyperpigmentation disorders induced by PMB.

Uncovering a new family of conserved virulence factors that promote the production of host-damaging outer membrane vesicles in gram-negative bacteria

CprA is a short-chain dehydrogenase/reductase (SDR) that contributes to resistance against colistin and antimicrobial peptides. The cprA gene is conserved across Pseudomonas aeruginosa clades and its expression is directly regulated by the two-component system PmrAB. We have shown that cprA expression leads to the production of outer membrane vesicles (OMVs) that block autophagic flux and have a greater capacity to activate the non-canonical inflammasome pathway. In a murine model of sepsis, a P. aeruginosa strain deleted for cprA was less virulent than the wild-type (WT) strain. These results demonstrate the important role of CprA in the pathogenicity of P. aeruginosa. It is worth noting that CprA is also a functional ortholog of hemolysin F (HlyF), which is encoded by virulence plasmids of Escherichia coli. We have shown that other cryptic SDRs encoded by mammalian and plant pathogens, such as Yersinia pestis and Ralstonia solanacearum are functional orthologs of CprA and HlyF. These SDRs also induce the production of OMVs which block autophagic flux. This study uncovers a new family of virulence determinants in Gram-negative bacteria, offering potential for innovative therapeutic interventions and deeper insights into bacterial pathogenesis.

Muco-adhesive chitosan-coated polyphenol nanoparticle for treatment of infectious acute pneumonia through sustained pulmonary delivery of polymyxin B

Infectious acute pneumonia caused by bacteria has been a great challenge to human health for long time, and the rapid clearance of aerosolized antibiotics in the lungs restricts their clinical application. The development of nanoformulations with facile preparation and mucoadhesive properties for the pulmonary delivery of antibiotics is thus significant for the treatment of infectious acute pneumonia. In this study, FDA (Food and Drug Administration)-approved tannic acid (TA) was used to construct mucoadhesive nanoformulations through the facile coating of chitosan (CS) to achieve long-lasting anti-infection effects against infectious acute pneumonia. Using an antibacterial peptide, polymyxin B (PB), as the model drug, the flash nanocomplexation technique was used to prepare CS-coated TA/poly(vinyl alcohol) (PVA)/PB nanoparticles (TPBC NPs) through non-covalent interactions of each component. Investigation on acute pneumonia mice model demonstrated that, through the strong electrostatic interaction between positively charged chitosan and negatively charged mucin in the trachea, the release of polymyxin B retained in the lung for at least 24 h-post inhalation of TPBC NPs, thereby inhibiting pulmonary infection within 3 days. Combined with their great biocompatibility, mucoadhesive TPBC NPs prepared by a facile and reproducible procedure may provide a new strategy for the pulmonary delivery of antibiotics to treat infectious acute pneumonia.

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.

Cerebrospinal fluid proteomics reveals the innate immunity and blood-brain barrier dysregulation in a patient with multidrug-resistant Acinetobacter baumannii ventriculitis treated with intrathecal and intravenous polymyxin B

Acinetobacter baumannii is a major pathogen of nosocomial meningitis and ventriculitis. Due to very limited antibiotic treatment options, polymyxins are often used as a last-line therapy. To optimise polymyxin use in the intraventricular environment, cerebrospinal fluid (CSF) proteomics was employed to investigate host-pathogen-polymyxin interactions in a 69-year-old patient with multidrug-resistant A. baumannii ventriculitis treated with a combination of intrathecal (ITH; 50,000 IU q24h/q48h), intraventricular (IVT; 50,000 IU q48h), and intravenous (500,000 IU, q12h) polymyxin B. CSF was collected before the first ITH dose in the ICU (0 h) and at 24 h, Day 7 and Day 26. The proteome was quantified at each time point and proteins with Qvalue <0.05 and fold change >1.2 were considered differentially expressed. Within 24 h of ITH/IVT polymyxin B administration, the innate immune system and neuroimmunity were highly active, evidenced by up-regulation of various pathways related to pathogen invasion, endocytosis and neutrophil degranulation. Blood-brain barrier impairment had worsened at 24 h but signs of repair were evident on Day 7 and Day 26. This is the first CSF proteomic study with polymyxins. Our findings provide critical mechanistic insights into optimizing ITH/IVT polymyxin administration.

In silico design and assessment of a multi-epitope peptide vaccine against multidrug-resistant Acinetobacter baumannii

Acinetobacter baumannii, an opportunistic and notorious nosocomial pathogen, is responsible for many infections affecting soft tissues, skin, lungs, bloodstream, and urinary tract, accounting for more than 722,000 cases annually. Despite the numerous advancements in therapeutic options, no approved vaccine is currently available for this particular bacterium. Consequently, this study focused on creating a rational vaccine design using bioinformatics tools. Three outer membrane proteins with immunogenic potential and properties of good vaccine candidates were used to select epitopes based on good antigenic properties, non-allergenicity, high binding scores, and a low IC50 value. A multi-epitope peptide (MEP) construct was created by sequentially linking the epitopes using suitable linkers. ClusPro 2.0 and C-ImmSim web servers were used for docking analysis with TLR2/TLR4 and immune response respectively. The Ramachandran plot showed an accurate model of the MEP with 100% residue in the most favored and allowed regions. The construct was highly antigenic, stable, non-allergenic, non-toxic, and soluble, and showed maximum population coverage. Additionally, molecular docking demonstrated strong binding between the designed MEP vaccine and TLR2/TLR4. In silico immunological simulations showed significant increases in T-cell and B-cell populations. Finally, codon optimization and in silico cloning were conducted using the pET-28a (+) plasmid vector to evaluate the efficiency of the expression of vaccine peptide in the host organism (Escherichia coli). This designed MEP vaccine would support and accelerate the laboratory work to develop a potent vaccine targeting MDR Acinetobacter baumannii.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40203-024-00292-3.

Evaluating the therapeutic impact of Compound Polymyxin B Ointment on postoperative wound healing in patients with perianal abscesses

Introduction

Perianal abscesses pose a considerable obstacle in the realm of postoperative wound treatment owing to their elevated susceptibility to infection and associated consequences. Polymyxin B Ointment, a compound renowned for its antibacterial qualities, has the potential to provide therapeutic advantages by promoting wound healing and mitigating postoperative problems.

Methods

Our institution conducted a thorough retrospective analysis spanning from December 2020 to December 2023 to assess the effectiveness of Compound Polymyxin B Ointment in the management of surgical wounds in patients diagnosed with perianal abscesses. The research encompassed a cohort of 100 individuals, who were classified into two groups: a control group that received conventional postoperative care, and an observation group that received supplementary treatment with Compound Polymyxin B Ointment. The evaluation of clinical outcomes involved measuring wound healing effectiveness, pain intensity using the Visual Analogue Scale (VAS), tissue swelling, exudation, necrotic tissue shedding time, duration of hospital stays, and rate of reduction in wound area.

Results

The group that received Compound Polymyxin B Ointment had significant enhancements in wound healing, as seen by a noteworthy 46% of participants completing complete healing, in contrast to the control group's 32%. The VAS was used to quantify pain levels, and the observation group reported a substantial reduction of almost 50% in ratings. Furthermore, this cohort exhibited a 45% decrease in edema and a 50% decline in exudation rates, in addition to a 50% acceleration in the shedding of necrotic tissue. The duration of the hospital stay was reduced by 40%, and the reduction in wound area was 18% higher, suggesting a more effective healing process. In addition, it is worth noting that the observation group had a lower incidence of problems, so underscoring the effectiveness of the ointment in facilitating wound healing and mitigating postoperative difficulties.

Discussion

The utilization of Compound Polymyxin B Ointment as an adjuvant measure in the surgical treatment of perianal abscesses has been found to have a substantial positive impact on wound healing, pain relief, and complication reduction. This finding provides evidence for the possibility of the ointment as a helpful inclusion in post-surgical wound care procedures among this specific group of patients.

Design, synthesis, and bioactivity investigation of novel cyclic lipopeptide antibiotics targeting top-priority multidrug-resistant gram-negative bacteria

OBJECTIVES

Polymyxins are the last-line therapy for top-priority multidrug-resistant (MDR) gram-negative bacteria. However, polymyxin nephrotoxicity impedes its clinical application. This study aimed to design, synthesize, and identify a novel and promising polymyxin derivative with high efficacy and low toxicity.

METHODS

To design polymyxin derivatives, we reduced the hydrophobicity of the two hydrophobic domains (fatty acyl chain and D-Phe6-L-Leu7) and modified the positive charged L-2,4-diaminobutyric acid (Dab) residues. Twenty-five derivatives were synthesized, and their antibacterial activities in vitro and renal cytotoxicities were determined. The nephrotoxicity and pharmacokinetic parameters of compound 12 were examined in rats. Antibacterial efficacy in vivo was evaluated using a mouse systemic infection model. Surface plasmon resonance analysis, compound 12-rifampicin combination therapy, and scanning electron microscopy were used to study the mechanism of action of compound 12.

RESULTS

This research found a new compound, identified as compound 12, which showed similar or increased antibacterial activity against all tested sensitive and carbapenem-resistant gram-negative bacteria. It exhibited reduced renal cytotoxicity and nephrotoxicity, a favorable pharmacokinetic profile, and maintained or improved antibacterial efficacy in vivo. Importantly, its anti-Pseudomonas aeruginosa activity significantly improved. Compound 12, when combined with rifampicin, enhanced the activity of rifampin against gram-negative bacteria. Compound 12 also showed a high affinity for lipopolysaccharide and disrupted cell membrane integrity.

CONCLUSION

Reducing the hydrophobicity of the two domains reduced renal cytotoxicity and nephrotoxicity. Shortening the side chain of Dab3 by one carbon maintained or increased its antibacterial activity both in vitro and in vivo. Furthermore, only the length of the side chain of Dab9 could be shortened by one carbon among the Dab1,5 and Dab8,9 residues. The bactericidal effects of compound 12 were related to the disruption of cell membrane integrity. Compound 12 may be a promising candidate for combating sensitive and carbapenem-resistant gram-negative bacterial infections, especially Pseudomonas aeruginosa.

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.

A novel small RNA PhaS contributes to polymyxin B-heteroresistance in carbapenem-resistant Klebsiella pneumoniae

In recent years, polymyxin has been used as a last-resort therapy for carbapenem-resistant bacterial infections. The emergence of heteroresistance (HR) to polymyxin hampers the efficacy of polymyxin treatment by amplifying resistant subpopulation. However, the mechanisms behind polymyxin HR remain unclear. Small noncoding RNAs (sRNAs) play an important role in regulating drug resistance. The purpose of this study was to investigate the effects and mechanisms of sRNA on polymyxin B (PB)-HR in carbapenem-resistant Klebsiella pneumoniae. In this study, a novel sRNA PhaS was identified by transcriptome sequencing. PhaS expression was elevated in the PB heteroresistant subpopulation. Overexpression and deletion of PhaS were constructed in three carbapenem-resistant K. pneumoniae strains. Population analysis profiling, growth curve, and time-killing curve analysis showed that PhaS enhanced PB-HR. In addition, we verified that PhaS directly targeted phoP through the green fluorescent protein reporter system. PhaS promoted the expression of phoP, thereby encouraging the expression of downstream genes pmrD and arnT. This upregulation of arnT promoted the 4-amino-4-deoxyL-arabinosaccharide (L-Ara4N) modification of lipid A in PhaS overexpressing strains, thus enhancing PB-HR. Further, within the promoter region of PhaS, specific PhoP recognition sites were identified. ONPG assays and RT-qPCR analysis confirmed that PhaS expression was positively modulated by PhoP and thus up-regulated by PB stimulation. To sum up, a novel sRNA enhancing PB-HR was identified and a positive feedback regulatory pathway of sRNA-PhoP/Q was demonstrated in the study. This helps to provide a more comprehensive and clear understanding of the underlying mechanisms behind polymyxin HR in carbapenem-resistant K. pneumoniae.

A systematic evaluation of population pharmacokinetic models for polymyxin B in patients with liver and/or kidney dysfunction

Polymyxin B (PMB) is considered a last-line treatment for multidrug-resistant (MDR) gram-negative bacterial infections. Model-informed precision dosing with population pharmacokinetics (PopPK) models could help to individualize PMB dosing regimens and improve therapy. However, the external prediction ability of the established PopPK models has not been fully elaborated. This study aimed to systemically evaluate eleven PMB PopPK models from ten published literature based on a new independent population, which was divided into four different populations, patients with liver dysfunction, kidney dysfunction, liver and kidney dysfunction, and normal liver and kidney function. The whole data set consisted of 146 patients with 391 PMB concentrations. The prediction- and simulation-based diagnostics and Bayesian forecasting were conducted to evaluate model predictability. In the overall evaluation process, none of the models exhibited satisfactory predictive ability in both prediction- and simulation-based diagnostic simultaneously. However, the evaluation of the models in the subgroup of patients with normal liver and kidney function revealed improved predictive performance compared to those with liver and/or kidney dysfunction. Bayesian forecasting demonstrated enhanced predictability with the incorporation of two to three prior observations. The external evaluation highlighted a lack of consistency between the prediction results of published models and the external validation dataset. Nonetheless, Bayesian forecasting holds promise in improving the predictive performance of the models, and feedback from therapeutic drug monitoring is crucial in optimizing individual dosing regimens.

Portable direct spraying porous nanofibrous membranes stent-loaded polymyxin B for treating diabetic wounds with difficult-to-heal gram-negative bacterial infections

Gram-negative bacteria infections in diabetic wounds are complicated to control, leading to amputation and even death in severe cases. There is an urgent need to develop effective therapeutic strategies. In recent years, electrospinning has attracted much attention due to its resemblance to extracellular matrix (ECM), which can regulate local cellular proliferation, migration, differentiation, etc.; however, its use is limited by its high cost and difficulty in transportation. This study proposes a portable direct-injection porous fibre scaffold containing polymyxin B (PMB) for local slow release for treating diabetic wounds infected with difficult-to-heal Gram-negative bacteria. The handheld portable electrospinner is lightweight and easy to operate and can be directly sprayed in situ to cover wounds with irregular shapes and sizes. When covering the wound in situ, the PVB/PVP nanofiber membrane can protect it from the external environment. Meanwhile, the nanofiber membrane dressing has a porosity of 20 % and a controlled drug-loading capacity. What's more, the evaluation of a whole skin defect model of type II diabetes mellitus infected with Gram-negative bacteria showed that the PMB-loaded nanofiber membrane could effectively inhibit Gram-negative bacteria infection, promote collagen deposition and re-epithelialization, and regulate the polarization of M1-type macrophages to M2-type macrophages, thereby controlling inflammation and promoting vascular regeneration, and significantly accelerating the healing of diabetic wounds. Overall, portable direct-injection porous fibre scaffold-loaded drugs are essential for healing difficult-to-heal wounds as local slow-release drug delivery.

Progress in the study of mefloquine as an antibiotic adjuvant for combination bacterial inhibition treatment

Antimicrobial resistance is among the greatest threats to public health globally, and drug repurposing strategies may be advantageous to addressing this problem. Mefloquine, a drug traditionally used to treat malaria, has emerged as a promising antibiotic adjuvant, due to its ability to enhance the effectiveness of conventional antibiotics against resistant bacterial strains. In this paper, we first outline the enhancement properties of mefloquine and its mechanisms of action as an adjuvant antibiotic against multidrug-resistant bacteria. Mefloquine exhibits synergistic bacteriostatic effects when combined with colistin, β-lactams, antituberculosis drugs, quinolones, and linezolid. Potential mechanisms underlying its synergistic effects include inhibition of antibiotic efflux, disruption of bacterial cell membrane integrity, and disturbance of biofilm formation. In addition, we explore the bacteriostatic effects of several mefloquine derivatives against Mycobacterium tuberculosis and some fungi. Further, we summarize the findings of recent studies on other aspects of mefloquine activity, including its antiviral and antitumor effects. Finally, the advantages and challenges of mefloquine use as an antibiotic adjuvant in combination with antibiotics for bacterial inhibition are discussed. Overall, mefloquine shows excellent potential as an antibiotic adjuvant therapy against multidrug-resistant bacteria and is a promising candidate for combination therapy; however, further studies are needed to fully elucidate its mechanism of action and address the challenges associated with its clinical application.

Membrane lipid homeostasis dually regulates conformational transition of phosphoethanolamine transferase EptA

The phosphoethanolamine transferase EptA utilizes phosphatidylethanolamine (PE) in the bacterial cell membrane to modify the structure of lipopolysaccharide, thereby conferring antimicrobial resistance on Gram-negative pathogens. Previous studies have indicated that excessive consumption of PE can disrupt the cell membrane, leading to cell death. This implies the presence of a regulatory mechanism for EptA catalysis to maintain a balance between antimicrobial resistance and bacterial growth. Through microsecond-scale all-atom molecular dynamics simulations, we demonstrate that membrane lipid homeostasis modulates the conformational transition and catalytic activation of EptA. The conformation of EptA oscillates between closed and open states, ensuring the precise spatiotemporal sequence of substrates binding. Interestingly, the conformation of EptA is significantly influenced by its surrounding lipid microenvironment, particularly the PE proportion in the membrane. PE-rich membrane conditions initiate and stabilize the open conformation of EptA through both orthosteric and allosteric effects. Importantly, the reaction mediated by EptA gradually depletes PE in the membrane, ultimately hindering its conformational transition and catalytic activation. These findings collectively establish a self-promoted model, illustrating the regulatory mechanism of EptA during the development of antibiotic resistance.

Antibacterial Therapy Options for Infections Caused by Carbapenem-Resistant Acinetobacter baumannii

The review presents current treatment regimens for infections associated with carbapenem-resistant Acinetobacter baumannii, which are leading nosocomial pathogens exhibiting multidrug resistance to available antibacterial drugs. To date, widely used beta-lactam antibiotics, including carbapenems, have lost their effectiveness in combating acinetobacter infections, while new antibiotics remain poorly available to patients. Therefore, the only measure to combat the antibiotic resistance of carbapenem-resistant A. baumannii is to evaluate the efficiency of combination therapy in vitro and in vivo, which is of particular interest to Russian and foreign researchers.

Antibiotic resistance in Pseudomonas aeruginosa: mechanisms and emerging treatment

Pseudomonas aeruginosa, able to survive on the surfaces of medical devices, is a life-threatening pathogen that mainly leads to nosocomial infection especially in immunodeficient and cystic fibrosis (CF) patients. The antibiotic resistance in P. aeruginosa has become a world-concerning problem, which results in reduced and ineffective therapy efficacy. Besides intrinsic properties to decrease the intracellular content and activity of antibiotics, P. aeruginosa develops acquired resistance by gene mutation and acquisition, as well as adaptive resistance under specific situations. With in-depth research on drug resistance mechanisms and the development of biotechnology, innovative strategies have emerged and yielded benefits such as screening for new antibiotics based on artificial intelligence technology, utilizing drugs synergistically, optimizing administration, and developing biological therapy. This review summarizes the recent advances in the mechanisms of antibiotic resistance and emerging treatments for combating resistance, aiming to provide a reference for the development of therapy against drug-resistant P. aeruginosa.

A Targeted Click-to-Release Activation of the Last-Resort Antibiotic Colistin Reduces its Renal Cell Toxicity

The use of highly potent but very toxic antibiotics such as colistin has become inevitable due to the rise of antimicrobial resistance. We aimed for a chemically-triggered, controlled release of colistin at the infection site to lower its systemic toxicity by harnessing the power of click-to-release reactions. Kinetic experiments with nine tetrazines and three dienophiles demonstrated a fast release via an inverse-electron-demand Diels-Alder reaction between trans-cyclooctene (TCO) and the amine-functionalised tetrazine Tz7. The antibiotic activity of colistin against Escherichia coli was masked by TCO units, but restored upon reaction with d-Ubi-Tz, a tetrazine functionalised with the bacterial binding peptide d-Ubi29-41. While standard TCO did not improve toxicity against human proximal tubular kidney HK-2 cells, the installation of an aspartic acid-modified TCO masking group reduced the overall charge of the peptide and entry to the kidney cells, thereby dramatically lowering its toxicity. The analog Col-(TCO-Asp)1 had favourable pharmacokinetic properties in mice and was successfully activated locally in the lung by d-Ubi-Tz in an in vivo infection model, whereas it remained inactive and non-harmful without the chemical trigger. This study constitutes the first example of a systemically acting two-component antibiotic with improved drug tolerability.

Development and validation of a liquid chromatography-tandem mass spectrometry method for the determination of polymixin B1, B2, ile-B1, E1, and E2 in human plasma and its clinical pharmacokinetic application

Polymyxin B (PB) and Polymyxin E (PE, also called colistin) are used as the last treatment resort for multidrug-resistant Gram-negative bacterial infections. The nephrotoxicity and neurotoxicity of polymyxins limit their clinical use, and guidelines recommend therapeutic drug monitoring (TDM) to optimize efficacy and reduce toxicity. However, there are limited analytical methods available for the determination of PB and PE. This study aimed to develop a simple and robust liquid chromatography with tandem mass spectrometry (LC-MS/MS) analytical method for determining the main compounds of PB and PE, namely PB1, PB2, ile-PB1, PE1, and PE2, in human plasma and to investigate of their pharmacokinetics in critically ill patients with the use of PB and PE, respectively. Plasma PB1, PB2, ile-PB1, PE1, and PE2 were chromatographically separated on a Welch LP-C18 column and detected using electrospray ionization mode coupled with multiple reaction monitoring. The calibration curve showed acceptable linearity over 20-10,000 ng/mL for PB1, PE1, and PE2 and 10-5000 ng/mL for PB2 and ile-PB1 in the plasma, respectively. After validation following approved guidelines, this method was successfully applied for PB and PE pharmacokinetic analysis and TDM in critically ill patients. Additionally, the composition of PB1, PB2, ile-PB1, PE1, and PE2 remains unchanged from 0 to 12 h after entering the patient's body.

Detection of drug resistance in Escherichia coli from calves with diarrhea in the Tongliao region: an analysis of multidrug-resistant strains

Introduction

Escherichia coli is a major pathogen responsible for calf diarrhea, which has been exacerbated by the irrational and unscientific use of antimicrobial drugs, leading to significant drug resistance.

Methods

This study focused on the isolation and identification of E. coli from calf diarrhea samples in the Tongliao area of China. Isolation was conducted using selective media, Gram staining, and 16S rRNA sequencing. The minimum inhibitory concentration (MIC) of E. coli was determined through the microbroth dilution method. Additionally, the presence of antibiotic-resistant genes was detected, and multidrug-resistant strains were selected for whole-genome sequencing (WGS).

Results

The results revealed that all 40 isolated strains of E. coli exhibited resistance to sulfadiazine sodium, enrofloxacin, and ciprofloxacin, with 90% of the strains being susceptible to polymyxin B. Notably, strains 11, 23, and 24 demonstrated severe resistance. The detection rates of the antibiotic resistance genes TEM-1, TEM-206, strA, strB, qacH, and blaCTX were 100%, indicating a high prevalence of these genes. Moreover, the majority of strains carried antibiotic resistance genes consistent with their resistance phenotypes. WGS of strains 11, 23, and 24 revealed genome sizes of 4,897,185 bp, 4,920,234 bp, and 4,912,320 bp, respectively. These strains carried two, one, and two plasmids, respectively. The prediction of antibiotic resistance genes showed a substantial number of these genes within the genomes, with strain 24 harboring the highest number, totaling 77 subspecies containing 88 antibiotic resistance genes.

Discussion

In conclusion, all 40 isolated strains of E. coli from calf diarrhea in this study were multidrug-resistant, exhibiting a broad distribution of antibiotic resistance genes and mobile components. This poses a significant risk of horizontal gene transfer, highlighting the critical situation of antibiotic resistance in this region.

Impact of porin deficiency on the synergistic potential of colistin in combination with β-lactam/β-lactamase inhibitors against ESBL- and carbapenemase-producing Klebsiella pneumoniae

Combinations of colistin and β-lactam/β-lactamase inhibitors (BLBLIs) have shown in vitro synergy against β-lactamase-producing strains. However, data are limited and conflicting, potentially attributed to variations among the examined strains. This study investigated whether loss of porins OmpK35 and OmpK36 impacts the synergistic potential of colistin in combination with ceftazidime-avibactam or meropenem-avibactam against β-lactamase-producing Klebsiella pneumoniae. Genetically modified strains were constructed by introducing blaCTX-M-15, blaKPC-2, and blaOXA-48 chromosomally into K. pneumoniae ATCC 35657, in which the major porin-encoding genes (ompK35, ompK36) were either intact or knocked out. The in vitro activity of colistin in combination with ceftazidime-avibactam or meropenem-avibactam was evaluated by time-lapse microscopy screening and in static time-kill experiments. The deletion of porins in the β-lactamase-producing strains resulted in 2- to 128-fold increases in MICs for the β-lactams and BLBLIs. The activity of avibactam was concentration-dependent, and 4- to 16-fold higher concentrations were required to achieve similar inhibition of the β-lactamases in strains with porin loss. In the screening, synergy was observed for colistin and ceftazidime-avibactam against the CTX-M-15-producing strains and colistin and meropenem-avibactam against the KPC-2- and OXA-48-producing strains. The combination effects were less pronounced in the time-kill experiments, where synergy was rarely detected. No apparent associations were found between the loss of OmpK35 and OmpK36 and combination effects with colistin and BLBLIs, indicating that additional factors determine the synergistic potential of such combinations.

Recent advances of photoresponsive nanomaterials for diagnosis and treatment of acute kidney injury

Non-invasive imaging in the near-infrared region (NIR) offers enhanced tissue penetration, reduced spontaneous fluorescence of biological tissues, and improved signal-to-noise ratio (SNR), rendering it more suitable for in vivo deep tissue imaging. In recent years, a plethora of NIR photoresponsive materials have been employed for disease diagnosis, particularly acute kidney injury (AKI). These encompass inorganic nonmetallic materials such as carbon (C), silicon (Si), phosphorus (P), and upconversion nanoparticles (UCNPs); precious metal nanoparticles like gold and silver; as well as small molecule and organic semiconductor polymer nanoparticles with near infrared responsiveness. These materials enable effective therapy triggered by NIR light and serve as valuable tools for monitoring AKI in living systems. The review provides a concise overview of the current state and pathological characteristics of AKI, followed by an exploration of the application of nanomaterials and photoresponsive nanomaterials in AKI. Finally, it presents the design challenges and prospects associated with NIR photoresponsive materials in AKI.

Hypervirulent and carbapenem-resistant Klebsiella pneumoniae: A global public health threat

The evolution of hypervirulent and carbapenem-resistant Klebsiella pneumoniae can be categorized into three main patterns: the evolution of KL1/KL2-hvKp strains into CR-hvKp, the evolution of carbapenem-resistant K. pneumoniae (CRKp) strains into hv-CRKp, and the acquisition of hybrid plasmids carrying carbapenem resistance and virulence genes by classical K. pneumoniae (cKp). These strains are characterized by multi-drug resistance, high virulence, and high infectivity. Currently, there are no effective methods for treating and surveillance this pathogen. In addition, the continuous horizontal transfer and clonal spread of these bacteria under the pressure of hospital antibiotics have led to the emergence of more drug-resistant strains. This review discusses the evolution and distribution characteristics of hypervirulent and carbapenem-resistant K. pneumoniae, the mechanisms of carbapenem resistance and hypervirulence, risk factors for susceptibility, infection syndromes, treatment regimens, real-time surveillance and preventive control measures. It also outlines the resistance mechanisms of antimicrobial drugs used to treat this pathogen, providing insights for developing new drugs, combination therapies, and a "One Health" approach. Narrowing the scope of surveillance but intensifying implementation efforts is a viable solution. Monitoring of strains can be focused primarily on hospitals and urban wastewater treatment plants.

Population pharmacokinetic analysis and dosing optimization of colistin sulphate in lung transplant recipients with pneumonia: A prospective study

OBJECTIVE

Currently, there is a lack of information on the clinical pharmacokinetics (PK), effectiveness, and safety of colistin sulphate (CS) in lung transplant recipients. This study aims to improve CS dosing regimens and evaluate its population PK in lung transplant recipients.

METHODS

This study evaluated the clinical efficacy, microbiological efficacy, and adverse events of CS in lung transplant recipients. The NONMEM program was employed to construct the population PK model, and Monte Carlo simulations were executed to establish dosing regimens according to the probability of target attainment (PTA).

RESULTS

The study included 146 CS concentrations, spanning from 0.05 to 4.18 mg/L from 39 lung transplant recipients with multidrug-resistant Gram-negative bacteria. 26 (66.67%) patients successfully eradicated bacteria, and 30 (76.92%) patients had clinical cure or improvement. Additionally, only 2 (5.13%) patients developed CS-related nephrotoxicity. The PK profile was effectively represented by a one-compartmental model with linear elimination. Creatinine clearance and concomitant furosemide use were recognized as covariates influencing the clearance of CS. Based on the PTA results, a daily dosage of 1.5 million IU, divided into 2-3 administrations, could attain a PTA exceeding 90% for MIC ≤ 1 µg/mL at creatinine clearance of about 110 mL/min. However, this regimen would lead to insufficient exposure for MIC ≥ 2 µg/mL.

CONCLUSIONS

The clearance of CS is significantly influenced by concomitant furosemide use and renal function. The currently recommended dosing regimens by label sheet may result in subtherapeutic exposure for MIC exceeding 1 mg/L in lung transplant recipients.