Bacteria causing symptomatic urinary tract infection or asymptomatic bacteriuria

One thousand bacterial isolates from consecutive suprapublic aspirations of urine in two groups of patients with symptomatic urinary tract infection and two groups with asymptomatic bacteriuria were studied. Staphylococci accounted for 13 and 27% of the isolates from symptomatic patients but for only 3 and 4% of strains from asymptomatic bacteriuria. Conversely, 18 and 30% of Escherichia coli isolates from asymptomatic bacteriuria were auto-agglutinable when tested with antisera to the common urinary O-serogroups, whereas such strains accounted for only 5 and 7% of the E. coli from symptomatic patients. The high prevalence of auto-agglutinable E. coli in asymptomatic bacteriuria was accompanied by a reduction in the frequency of the common uninary O-serogroups rather than other smooth strains.