Virulence factors of Escherichia coli in urinary isolates from pregnant women.

Urinary isolates from 24 pregnant women with acute pyelonephritis and from 37 pregnant women with bacteriuria detected at screening were characterized for O:K:H serotype, electrophoretic type, adherence, hemolysin production, and serum resistance. Between the two diagnostic groups, only three clones were identical. For the remaining isolates, both the identification markers and virulence traits differed significantly. The strains from pregnant women with pyelonephritis did not significantly differ from those from non-pregnant women. Thus, pregnancy was shown not to abolish the difference in virulence between Escherichia coli causing acute pyelonephritis and asymptomatic bacteriuria.