Acquisition of Tigecycline Resistance by Carbapenem-Resistant Klebsiella pneumoniae Confers Collateral Hypersensitivity to Aminoglycosides

The distribution and antibiotic-resistant characteristics and risk factors of pathogens associated with clinical biliary tract infection in humans

Introduction

Biliary Infection in patients is a common and important phenomenon resulting in severe complications and high morbidity, while the distributions and drug resistance profiles of biliary bacteria and related risk factors are dynamic. This study explored the characteristics of and risk factors for biliary infection to promote the rational use of antibiotics in clinically.

Methods

Bacterial identification and drug susceptibility testing were completed using the Vitek 2 Compact analysis system. The distribution and antibiotic-resistant characteristics of 3,490 strains of biliary bacteria in patients at Nankai Hospital from 2019 to 2021 were analyzed using Whonet 5.6 and SPSS 26.0 software. We then retrospectively analyzed the clinical data and risk factors associated with 2,340 strains of Gram-negative bacilli, which were divided into multidrug-resistant bacteria (1,508 cases) and non-multidrug-resistant bacteria (832 cases) by a multivariate Cox regression model.

Results and discussion

A total of 3,490 pathogenic bacterial strains were isolated from bile samples, including 2,340 (67.05%) Gram-negative strains, 1,029 (29.48%) Gram-positive strains, and 109 (4.56%) fungal strains. The top five pathogenic bacteria were Escherichia coli, Klebsiella pneumoniae, Enterococcus faecium, Enterococcus faecalis, and Pseudomonas aeruginosa. The rate of Escherichia coli resistance to ciprofloxacin increased (p < 0.05), while the resistance to amikacin decreased (p < 0.05). The resistance of Klebsiella pneumoniae to cephalosporins, carbapenems, β-lactamase inhibitors, cephalases, aminoglycosides, and quinolones increased (p < 0.05), and the resistance of Pseudomonas aeruginosa to piperacillin, piperacillin/tazobactam, ticacillin/clavulanic acid, and amicacin declined significantly (p < 0.05). The resistance of Enterococcus faecium to tetracycline increased by year (p < 0.05), and the resistance of Enterococcus faecalis to erythromycin and high-concentration gentamicin declined (p < 0.05). Multivariate logistic regression analysis suggested that the administration of third- or fourth-generation cephalosporins was an independent risk factor for biliary infection. In summary, Gram-negative bacilli were the most common pathogenic bacteria isolated from biliary infection patients, especially Escherichia coli, and the rates and patterns of drug resistance were high and in constant flux; therefore, rational antimicrobial drug use should be carried out considering risk factors.

Carbapenem-resistant Gram-negative bacteria (CR-GNB) in ICUs: resistance genes, therapeutics, and prevention - a comprehensive review

Intensive care units (ICUs) are specialized environments dedicated to the management of critically ill patients, who are particularly susceptible to drug-resistant bacteria. Among these, carbapenem-resistant Gram-negative bacteria (CR-GNB) pose a significant threat endangering the lives of ICU patients. Carbapenemase production is a key resistance mechanism in CR-GNB, with the transfer of resistance genes contributing to the extensive emergence of antimicrobial resistance (AMR). CR-GNB infections are widespread in ICUs, highlighting an urgent need for prevention and control measures to reduce mortality rates associated with CR-GNB transmission or infection. This review provides an overview of key aspects surrounding CR-GNB within ICUs. We examine the mechanisms of bacterial drug resistance, the resistance genes that frequently occur with CR-GNB infections in ICU, and the therapeutic options against carbapenemase genotypes. Additionally, we highlight crucial preventive measures to impede the transmission and spread of CR-GNB within ICUs, along with reviewing the advances made in the field of clinical predictive modeling research, which hold excellent potential for practical application.

Tigecycline-Rifampicin Restrains Resistance Development in Carbapenem-Resistant Klebsiella pneumoniae

The goal of this study was to clarify the synergistic antibacterial activity of the combination of tigecycline (TGC) and rifampicin (RIF). Additionally, the study sought to investigate the impact of this combination on the development of mutational resistance and to assess its efficacy in an in vivo model using Galleria mellonella. Through a checkerboard test, we found that the combination of TGC and RIF showed synergistic antibacterial activity against carbapenem-resistant Klebsiella pneumoniae (CRKP). The fractional inhibition concentration index (FICI) was found to be ≤0.5, confirming the potency of the combination. Additionally, this synergistic effect was further validated in vivo using the G. mellonella infection model. TGC-RIF treatment had a lower mutant prevention concentration (MPC) than that of monotherapy, indicating its potential to reduce the development of mutational resistance. We observed a substantial variation in the MPCs of TGC and RIF when they were measured at different proportions in the combinations. Furthermore, during the resistant mutant selection window (MSW) test, we noticed a correlation between strains with low FICI and low MSW. The expression of efflux-pump-related genes, namely rarA and acrB, is significantly decreased in the combination therapy group. This indicates that altered expression levels of certain efflux pump regulator genes are associated with a combined decrease in bacterial mutation resistance. In conclusion, the combination of TGC and RIF effectively suppresses antibiotic resistance selection in CRKP. This study establishes a paradigm for evaluating drug-resistant mutant suppression in antimicrobial combination therapy.

Large-Scale Analysis of Fitness Cost of tet(X4)-Positive Plasmids in Escherichia coli

Tigecycline is one of important antimicrobial agents for the treatment of infections caused by multidrug-resistant (MDR) Gram-negative bacteria. However, the emergence and prevalence of plasmid-mediated tigecycline resistance gene tet(X4) are threatening human and animal health. Fitness cost elicited by resistance plasmids is a key factor affecting the maintenance and transmission of antibiotic resistance genes (ARGs) in the host. A comparative analysis of the fitness cost of different types of tet(X4)-positive plasmids is helpful to understand and predict the prevalence of dominant plasmids. In this study, we performed a large-scale analysis of fitness cost of tet(X4)-positive plasmids origin from clinical isolates. These plasmids were successfully electroporated into a reference strain Escherichia coli TOP10, and a series of transformants carrying the tet(X) gene were obtained. The effects of tet(X4)-positive plasmids on the growth rate, plasmid stability, relative fitness, biofilm formation, and virulence in a Galleria mellonella model were evaluated. Consequently, we found that these plasmids resulted in varying degrees of fitness cost on TOP10, including delayed bacterial growth and attenuated virulence. Out of these plasmids, tet(X4)-harboring IncFII plasmids showed the lowest fitness cost on the host. Furthermore, by means of experimental evolution in the presence of commonly used drugs in clinic, the fitness cost of tet(X4)-positive plasmids was substantially alleviated, accompanied by increased plasmid stability. Collectively, our data reveal the differential fitness cost caused by different types of tet(X4)-positive plasmids and suggest that the wide use of tetracycline antibiotics may promote the evolution of plasmids.