Serum resistance among Escherichia coli strains causing urinary tract infection in relation to O type and the carriage of hemolysin, colicin, and antibiotic resistance determinants

Abstract

The sensitivity to normal human serum of 91 smooth strains of E. coli isolated from urinary tract infections was determined. Production of hemolysin, which was common and associated primarily with the types 04, 06, 018 and 075, was significantly correlated with high levels of serum resistance, both within the total population and within individual O types. Serum resistance was not significantly associated with antibiotic resistance (whether transmissible or not), with colicinogeny in general or with colicin V production in particular. The carriage of R and ColV plasmids, shown previously to be capable of conferring increased levels of serum resistance on individual strains of E. coli isolated from other sources, evidently does not play an important part in determining the serum sensitivity of the E. coli population involved in urinary tract infection.