Host-Parasite Interaction in Patients with Infections due to Escherichia coli. I. The Serogrouping of E. coli from Intestinal and Extraintestinal Sources*

Abstract

The ability to serogroup E. coli prompted this study of the host-parasite interaction in patients with extra-intestinal infections. Over 3,000 colonies were isolated from 471 specimens obtained from 254 patients with infections of the urinary tract or bacteremia, or both. Serogroups 1, 4, 6, 7, 16/62, 25, 50, and 75 accounted for approximately 80% of the groupable strains isolated from specimens of blood or urine. Serogroups 4 and 6 were identified most frequently and comprised 40% of those from urine and 52% of those from blood. The total proportion of the 8 common O groups did not vary among specimens obtained from different human populations; however, the individual serogroups showed minor variations. A study of the serogroups of E. coli in paired cultures of urine and feces revealed the same strain in both specimens of 80% of those examined. Fecal specimens obtained from infected patients were 3 to 4 times as likely to contain O groups 4, 6, or 50 as were those from healthy outpatients. The distribution of the 8 common serogroups among specimens obtained from patients with symptomatic bacteriuria, cystitis, acute pyelonephritis, and bacteremia secondary to a urinary tract portal of entry was compared. The disproportionate association of O groups 7, 16/62, and 50 with acute pyelonephritis appeared to reflect the population studied rather than enhanced virulence.