Do Escherichia coli strains causing acute cystitis have a distinct virulence repertoire?

Bacterial virulence factors influence the site and severity of urinary tract infections. While pyelonephritis-associated molecular traits have been defined, virulence factors specific for acute cystitis strains have not been identified. This study examined the virulence factor repertoire of 247 Escherichia coli strains, prospectively isolated from women with community-acquired acute cystitis. Fim sequences were present in 96% of the isolates, which also expressed Type 1 fimbriae. Curli were detected in 75%, 13% of which formed cellulose. Pap sequences were present in 47%, 27% were papG+, 23% were prsG+ and 42% expressed P fimbriae. TcpC was expressed by 33% of the strains, 32% in a subgroup of patients who only had symptoms of cystitis and 42% in patients with signs of upper urinary tract involvement; most frequently by the papG+/prsG+ subgroup. Strains with the full fim, pap and TcpC and curli virulence profile were more common in cystitis patients with than in patients without upper tract involvement (p<0.05). The varied virulence profile of E. coli strains causing acute cystitis suggests that diverse bacterial strains, expressing Type 1 fimbriae trigger a convergent host response, involving pathways that give rise to the characteristic symptoms of acute cystitis.