Identification of Genes Important for Growth of Asymptomatic Bacteriuria Escherichia coli in Urine
ABSTRACTEscherichia coliis the most important etiological agent of urinary tract infections (UTIs). Unlike uropathogenicE. coli, which causes symptomatic infections, asymptomatic bacteriuria (ABU)E. colistrains typically lack essential virulence factors and colonize the bladder in the absence of symptoms. While ABUE. colican persist in the bladder for long periods of time, little is known about the genetic determinants required for its growth and fitness in urine. To identify such genes, we have employed a transposon mutagenesis approach using the prototypic ABUE. colistrain 83972 and the clinical ABUE. colistrain VR89. Six genes involved in the biosynthesis of various amino acids and nucleobases were identified (carB,argE,argC,purA,metE, andilvC), and site-specific mutants were subsequently constructed inE. coli83972 andE. coliVR89 for each of these genes. In all cases, these mutants exhibited reduced growth rates and final cell densities in human urine. The growth defects could be complemented intransas well as by supplementation with the appropriate amino acid or nucleobase. When assessedin vivoin a mouse model,E. coli83972carABand 83972argCshowed a significantly reduced competitive advantage in the bladder and/or kidney during coinoculation experiments with the parent strain, whereas 83972metEand 83972ilvCdid not. Taken together, our data have identified several biosynthesis pathways as new important fitness factors associated with the growth of ABUE. coliin human urine.