Association of carboxylesterase B electrophoretic pattern with presence and expression of urovirulence factor determinants and antimicrobial resistance among strains of Escherichia coli that cause urosepsis

We determined the carboxylesterase B electrophoretic profiles of 74 blood isolates of Escherichia coli from patients with urosepsis. Most strains (64%) exhibited the B₂ electrophoretic pattern. P fimbrial and hemolysin genetic determinants were present and expressed significantly more often among strains with the B₂ than with the B₁ electrophoretic pattern. In contrast, aerobactin determinants were significantly more prevalent and more commonly expressed among the B₁ strains; this difference was attributable to the presence of plasmid-encoded aerobactin in one-third of the B₁ strains (P = 0.02, B₁ versus B₂). The prevalence and extent of antimicrobial resistance was significantly greater among the B₁ strains, and the B₁ electrophoretic pattern was more often found in isolates from patients with urinary tract abnormalities. We conclude that the carboxylesterase B electrophoretic pattern differentiates two groups of E. coli isolates from patients with urosepsis: strains with the B₁ electrophoretic pattern are associated with urologically impaired hosts, characteristically lack P fimbrial and hemolysin determinants, and often carry a plasmid-encoded aerobactin system (possibly on multiple antimicrohial resistance plasmids), whereas B₂ strains more commonly invade noncompromised hosts, express P fimbriae and hemolysin, carry chromosomal aerobactin determinants, and lack antimicrobial resistance.