Role of the Vpe Carbohydrate Permease in Escherichia coli Urovirulence and FitnessIn Vivo
ABSTRACTUropathogenicEscherichia coli(UPEC) strains are a leading cause of infections in humans, but the mechanisms governing host colonization by this bacterium remain poorly understood. Previous studies have identified numerous gene clusters encoding proteins involved in sugar transport, in pathogen-specific islands. We investigated the role in fitness and virulence of thevpeoperon encoding an EII complex of the phosphotransferase (PTS) system, which is found more frequently in human strains from infected urine and blood (45%) than inE. coliisolated from healthy humans (15%). We studied the role of this locusin vivo, using the UPECE. colistrain AL511, mutants, and complemented derivatives in two experimental mouse models of infection. Mutant strains displayed attenuated virulence in a mouse model of sepsis. A role in kidney colonization was also demonstrated by coinfection experiments in a mouse model of pyelonephritis. Electron microscopy examinations showed that thevpeBCmutant produced much smaller amounts of a capsule-like surface material than the wild type, particularly when growing in human urine. Complementation of thevpeBCmutation led to an increase in the amount of exopolysaccharide, resistance to serum killing, and virulence. It was therefore clear that the loss ofvpegenes was responsible for all the observed phenotypes. We also demonstrated the involvement of thevpelocus in gut colonization in the streptomycin-treated mouse model of intestinal colonization. These findings confirm that carbohydrate transport and metabolism underlie the ability of UPEC strains to colonize the host intestine and to infect various host sites.