Interaction of human serum and neutrophils with Escherichia coli strains: differences between strains isolated from urine of patients with pyelonephritis or asymptomatic bacteriuria.

Strains of Escherichia coli isolated from the urine of children with pyelonephritis (n = 18) or asymptomatic bacteriuria (ABU) (n = 20) were serotyped and compared with respect to opsonic requirements, sensitivity to serum, amount of chemiluminescence produced by normal neutrophils during phagocytosis of the various strains, and amount of capsular antigen. Strains isolated from cases of ABU more often had the capacity to activate the alternative complement pathway than had strains causing pyelonephritis. The ABU strains were also better opsonized in fresh human serum and were more often serum sensitive than the pyelonephritic strains. There were individual variations in neutrophil chemiluminescence during phagocytosis of the various strains, but the two groups of strains did not differ significantly. The strains from pyelonephritis cases produced a greater amount of capsular antigens than the ABU strains. There was no correlation between presence of a particular O or K antigen and capacity to activate the alternative complement pathway. The observed differences between strains isolated from patients with ABU and those isolated from patients with pyelonephritis may be relevant for further studies on differences in bacterial virulence or host defense factors.