|Rivera Betancourt, Mildred|
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 4, 2002
Publication Date: October 20, 2002
Citation: Barkocy-Gallagher, G.A., Berry, E.D., Rivera Betancourt, M., Arthur, T.M., Nou, X., Koohmaraie, M. 2002. Development of methods for the recovery of Escherichia coli O157:H7 and Salmonella from beef carcass sponge samples and bovine fecal and hide samples. Journal of Food Protection. 65(10):1527-1534 Interpretive Summary: E. coli O157:H7 and Salmonella are foodborne pathogens that can be associated with raw or undercooked beef. Therefore, it is important to measure how often these bacteria are present in cattle feces and on hides and carcasses. Methods were developed to recover both types of bacteria from the same samples, because such methods were not available. The new methods, called the MRU and MRU-TT methods, rely on steps to increase the numbers of the bacteria and specifically recover them. These methods appear to be at least as good as other methods used to recover E. coli O157:H7 and Salmonella from separate samples. Significantly, the new methods also can be used to determine how often these bacteria are present in samples at the same time.
Technical Abstract: Culture methods were developed for concurrent recovery of Escherichia coli O157:H7 and Salmonella from bovine carcass, fecal, and hide samples. Several enrichment conditions were tested based on overall growth of pure cultures; tryptic soy broth for 2 h at 25 deg C, then for 6 h at 42 deg C, was selected for use. Immunomagnetic separation (IMS) was incorporated for sensitivity and selectivity, with a post-IMS enrichment for recovery of Salmonella as recommended by the manufacturer. Selective agars for plating after IMS were identified based on ease of target colony identification. Sorbitol MacConkey agar supplemented with cefixime and potassium tellurite and Rainbow agar supplemented with novobiocin and potassium tellurite were chosen for recovery of E. coli O157:H7. Brilliant green agar with sulfadiazine and Hektoen enteric agar supplemented with novobiocin were selected for recovery of Salmonella. The resulting methods were evaluated along with standard or previously used methods for recovery of E. coli O157:H7 and Salmonella from bovine feces, hide samples, and carcass sponge samples. The "MRU" methods performed at least as well as the established methods, except that a secondary enrichment in tetrathionate (TT) broth prior to IMS was required for optimal recovery of Salmonella from feces. Thus, the MRU and MRU-TT methods are effective for recovery of both E. coli O157:H7 and Salmonella from the same bovine carcass, hide, or fecal samples.