High exposure, rapid turnover: strain-level dynamics of Klebsiella pneumoniae carriage in community and hospitalized populations in Bangladesh.

The gastrointestinal (GI) tract serves as a reservoir of Klebsiella pneumoniae (Kp), facilitating transmission of invasive strains and dissemination of antimicrobial resistance genes (ARG). Studies of drug-resistant strains in hospitalized patients, during care, and post-discharge, have shown that Kp may persist for months to years in the GI tract. In contrast, there are limited longitudinal data characterizing the duration of Kp GI carriage in healthy populations. In this study, we evaluated a previously described population from an urban neighborhood of Dhaka, Bangladesh, using metagenomic analyses of Kp-enriched fecal cultures to characterize strain-level and ARG carriage dynamics over a 2-month period, and we compared this with Kp carriage data from a contemporaneously enrolled hospitalized cohort from Dhaka Medical College Hospital. Our results show high rates of Kp carriage in both groups, along with frequent co-carriage of multiple drug-resistant strains. Overall, Kp strains were genetically diverse, and carriage of individual strains was typically short-lived, with extensive turnover between time points. We also observed age-associated increases in IgG antibody responses to common Kp surface antigens, which we postulate reflect the effect of repeated, frequent exposures to Kp in these populations. Together, these findings provide insights into the carriage dynamics of Kp in a highly endemic setting.IMPORTANCEKlebsiella pneumoniae is a leading cause of antibiotic-resistant healthcare-associated infections, with the World Health Organization listing carbapenem-resistant strains as a priority pathogen. Gastrointestinal (GI) carriage is recognized as a risk factor for invasive disease in hospitalized patients, with the infecting strain often originating from the patient's own gut microbiota. Less is known about non-hospitalized populations, where GI carriage is common but asymptomatic. By defining strain-level dynamics and characterizing the antimicrobial resistance genes (ARGs) circulating in a highly endemic community, this study provides a valuable counterpoint to previous research focused on hospital settings and contributes to our understanding of the diversity and dynamics of circulating strains in healthy populations where the burden of Klebsiella pneumoniae is high.