Abstract
BACKGROUND: Klebsiella pneumoniae is an important opportunistic pathogen causing pneumonia, sepsis and urinary tract infections. Colonisation of the gastrointestinal (GI) tract is a key step in the development of infections; yet the specific factors important for K. pneumoniae to colonize and reside in the GI tract of the host are largely unknown. To identify K. pneumoniae genes promoting GI colonisation, a novel genomic-library-based approach was employed. RESULTS: Screening of a K. pneumoniae C3091 genomic library, expressed in E. coli strain EPI100, in a mouse model of GI colonisation led to the positive selection of five clones containing genes promoting persistent colonisation of the mouse GI tract. These included genes encoding the global response regulator ArcA; GalET of the galactose operon; and a cluster of two putative membrane-associated proteins of unknown function. Both ArcA and GalET are known to be involved in metabolic pathways in Klebsiella but may have additional biological actions beneficial to the pathogen. In support of this, GalET was found to confer decreased bile salt sensitivity to EPI100. CONCLUSIONS: The present work establishes the use of genomic-library-based in vivo screening assays as a valuable tool for identification and characterization of virulence factors in K. pneumoniae and other bacterial pathogens.