<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p><jats:italic>Klebsiella pneumoniae</jats:italic> is a leading cause of extended-spectrum beta-lactamase (ESBL) producing hospital-associated infections, for which elderly patients are at increased risk.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>We conducted a 1-year prospective cohort study, in which a third of patients admitted to two geriatric wards in a specialized hospital were recruited and screened for carriage of <jats:italic>K. pneumoniae</jats:italic> by microbiological culture. Clinical isolates were monitored via the hospital laboratory. Colonizing and clinical isolates were subjected to whole genome sequencing and antimicrobial susceptibility testing.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p><jats:italic>K. pneumoniae</jats:italic> throat carriage prevalence was 4.1%, rectal carriage 10.8% and ESBL carriage 1.7%. <jats:italic>K. pneumoniae</jats:italic> infection incidence was 1.2%. The isolates were diverse, and most patients were colonized or infected with a unique phylogenetic lineage, with no evidence of transmission in the wards. ESBL strains carried <jats:italic>bla</jats:italic><jats:sub>CTX-M-15</jats:sub><jats:sub>and</jats:sub> belonged to clones associated with hospital-acquired ESBL infections in other countries (ST29, ST323, ST340).</jats:p><jats:p>One also carried the carbapenemase <jats:italic>bla</jats:italic><jats:sub>IMP-26</jats:sub>. Genomic and epidemiological data provided evidence that ESBL strains were acquired in the referring hospital. Nanopore sequencing also identified strain-to-strain transmission of a <jats:italic>bla</jats:italic><jats:sub>CTX-M-15</jats:sub> FIB<jats:sub>K</jats:sub>/FII<jats:sub>K</jats:sub> plasmid in the referring hospital.</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>The data suggest the major source of <jats:italic>K. pneumoniae</jats:italic> was the patient’s own gut microbiome, but ESBL strains were acquired in the referring hospital. This highlights the importance of the wider hospital network to understanding <jats:italic>K. pneumoniae</jats:italic> risk and infection control. Rectal screening for ESBL organisms upon admission to geriatric wards could help inform patient management and infection control in such facilities.</jats:p></jats:sec><jats:sec><jats:title>Summary</jats:title><jats:p>Patients’ own gut microbiota were the major source of <jats:italic>K. pneumoniae</jats:italic>, but extended-spectrum beta-lactamase strains were acquired in the referring hospital. This highlights the potential for rectal screening, and the importance of the wider hospital network, for local risk management.</jats:p></jats:sec>