<prompt> All are impoant causes of UTI except?E coliProteusKlebsiellaStreptococcus viridans  <response>: Ans. is d i.e., Streptococcus viridans The dominant etiologic agents, accounting for more than 85 of cases of urinary tract infection, are the gram-negative bacilli that are normal inhabitants of intestinal tract. By far the most common is Escherichia coli, followed by proteus, klebsiella, and Enterobacter. In most patients with urinary tract infection, the infecting organisms are derived from the patients own fecal flora. This is thus a form of endogenous infection. 