A multidrug-resistant Escherichia coli clonal group (designated CgA) has been isolated from women with cystitis and pyelonephritis in several communities. This study was designed to determine if CgA can cause community-acquired bloodstream infections.

All community-acquired bloodstream infections caused by E. coli identified at the San Francisco General Hospital between May 2001 and May 2003 were included. The diagnosis of septicemia was based on admission diagnosis. E. coli isolates were characterized by antibiotic susceptibility profile, enterobacterial repetitive intergenic consensus (ERIC2) PCR, serogrouping, and pulsed field gel electrophoresis (PFGE).

A total of 127 individuals with a community-acquired bloodstream infection were identified; 48 (39%) were trimethoprim-sulfamethoxazole (SXT)-resistant. CgA, as defined by ERIC2 PCR, was responsible for 19 (15%) of these infections. Infection with a CgA isolate was associated with an admission diagnosis of cystitis or pyelonephritis (p=0.01). By PFGE, none of the CgA isolates were indistinguishable to the prototype cystitis strain; however, nine bloodstream isolates differed by fewer than six bands.

CgA can cause community-acquired bloodstream infections, but does not appear to cause a disproportionate number of severe extraintestinal infections. This study provides evidence that UTI-causing clonal groups can cause a wide spectrum of disease and are an important clinical and public health concern.