Urinary tract infections caused by drug-resistant Escherichia coli may have an animal origin, Meena Ramchandani, M.D., of the University of California, Berkeley, and colleagues reported.
A number of cases across the United States caused by a trimethoprim-sulfamethoxazole (TMP-SMZ)-resistant E. coli strain belonging to a single clonal group sparked concerns about a possible association with contaminated food products. An investigation of 495 animal isolates showed that 128 had an electrophoretic pattern indistinguishable from that of the resistant strain in humans, and 14 of those were TMP-SMZ resistant. One, from a cow, was 94% similar to the pattern of a uropathogenic E. coli strain recovered from a human patient (Clin. Infect. Dis. 2005;40:251–7).
The possibility that contaminated food products are the source of drug-resistant UTIs has serious public health implications, the investigators concluded, noting that the introduction of the clonal group E. coli strain in this study doubled the prevalence of TMP-SMZ-resistant UTIs in one community.
However, in an editorial, Thomas Hooten, M.D., and Mansour Samadpour, M.D., of the University of Washington, Seattle, said that although they agree with the basic premise of the article, the findings do not convince them of a link between the animal- and human-associated resistant E. coli strains. The study fails to provide clear epidemiologic linkage between the strains, they noted (Clin. Infect. Dis. 2005;40:258–9).