TAM mediates adaptation of carbapenem-resistant Klebsiella pneumoniae to antimicrobial stress during host colonization and infection

Abstract

Gram-negative pathogens, such as Klebsiella pneumoniae, remodel their outer membrane (OM) in response to stress to maintain its integrity as an effective barrier and thus to promote their survival in the host. The emergence of carbapenem-resistant K. pneumoniae (CR-Kp) strains that are resistant to virtually all antibiotics is an increasing clinical problem and OM impermeability has limited development of antimicrobial agents because higher molecular weight antibiotics cannot access sites of activity. Here, we demonstrate that TAM (translocation and assembly module) deletion increases CR-Kp OM permeability under stress conditions and enhances sensitivity to high-molecular weight antimicrobials. SILAC-based proteomic analyses revealed mis-localization of membrane proteins in the TAM deficient strain. Stress-induced sensitization enhances clearance of TAM-deficient CR-Kp from the gut lumen following fecal microbiota transplantation and from infection sites following pulmonary or systemic infection. Our study suggests that TAM, as a regulator of OM permeability, represents a potential target for development of agents that enhance the effectiveness of existing antibiotics. Antibiotics remain remarkably effective at controlling bacterial infections, however, in part due to their extensive use in clinical and agricultural settings, many microbial pathogens have developed antibiotic resistance. Development of new antimicrobial agents to treat multidrug-resistant infections is particularly challenging for Gram-negative bacteria such as Klebsiella pneumoniae, a leading cause of nosocomial infection. Those bacteria have an additional layer in the envelope, which prevents potentially clinically useful antimicrobial compounds to access sites of activity. In this study, we demonstrate that translocation and assembly module (TAM) mediates antibiotic and antimicrobial peptide resistance during host colonization and infection with highly antibiotic-resistant K. pneumoniae (CR-Kp). Loss of TAM impaired the envelope biogenesis and increased the sensitivity of CR-Kp to large antimicrobials under stress conditions. Stress-induced sensitization enhanced clearance of CR-Kp from the gut lumen as well as from infection sites. Our finding offers a potential target for therapeutic agents to enhance permeability and thus effectiveness of existing and potential antibiotics.