Viable but nonculturable uropathogenic bacteria are present in the mouse urinary tract following urinary tract infection and antibiotic therapy

Involvement of the viable but nonculturable (VBNC) condition in recurrent u rinary tract infections (UTIs) was investigated. VBNC bacteria are those wh ich are alive but do not give rise to visible growth under nonselective gro wth conditions. Urine, bladder, and kidney samples collected over a 2-month period from BALB/c mice inoculated with the uropathogenic Escherichia coli strain J96 were examined to determine the level of culturable and viable b acteria. Urine from uninoculated mice was found to contain more viable than culturable bacteria. Inoculated mice had a transient increase in the level of culturable forms of the uropathogen in their urine, followed by a decre ase to background levels; they also had multiple log higher levels of viabl e cells than culturable cells. The culturable pathogenic bacteria in mice t hat were inoculated and received antibiotic treatment dropped to undetectab le levels within 1 week. At 2 out of 12 subsequent time points spanning an additional 65 days, culturable forms of the inoculated pathogenic bacteria were recovered. Polymerase chain reaction (PCR) analysis confirmed that DNA from the inoculated bacteria was present in a sample that yielded no cultu rable bacteria. These data indicate that the inoculated uropathogenic E. co li was not eliminated by antibiotic therapy, and suggest that these bacteri a may escape detection by current standard culturability assays because the y are VBNC.