Follow-up study of verocytotoxigenic Escherichia coli infection in dairy farm families.

It is possible that in the study by McAdam et al. [4], the likeli-HIV status. However, these data were not provided in their paper, and it is just as possible that many of the TB patients who were To the Editor —Between July 1992 and May 1993, evidence of not IDUs in that study were also HIV–infected. Hence, one can verocytotoxigenic Escherichia coli (VTEC) was found in stool speculate to make either conclusion. The study by Reichman et cultures of 24 (27.3%) of 88 healthy family members residing on al. [5] that we referenced was done before the beginning of the 16 Ontario dairy farms [1]. Four of nine serotypes of VTEC iso-HIV epidemic; hence, there should have been no influence of the lated from these dairy farm family members were also isolated HIV serostatus on the disease outcome among purified protein from cattle on their farms. Here we report on a follow-up study derivative (PPD)–positive persons in that study. We felt that it in which these 16 farms were revisited after 5–13 months to was reasonable to reference two papers from New York City that investigate the frequency and possible persistence of VTEC infec-provided data about the likelihood of active disease development tion in these families and their dairy cattle. among PPD–positive IDUs to speculate about a conclusion sup-All family members on the 16 dairy farms were asked to submit portive of our hypothesis. Hence, this is not an error but an infer-a stool specimen. A rectal swab sample was obtained from all ence based on data provided by two relevant papers. calves õ3 months of age on each farm. Similar samples were We did not present the analysis adjusting the odds ratios for obtained from all cows in the milking herd (5 farms) or a random residence in a shelter by injection drug use because the numbers sample of the milking herd consisting of 25% of the herd or a became too small to make a meaningful conclusion, and we were minimum of 10 cows (11 farms). Human and bovine fecal samples not interested in stratifying a variable that was associated only were cultured and tested for the presence of VTEC by polymerase with a cluster pattern. The point of this paper was to identify chain reaction (PCR) amplification of VT gene sequences as de-factors associated with infection with the C strain, not infection scribed previously [1–3]. Cultures …