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S. D. ALCAINE1, S. S. Sukhnanand, L. D. Warnick, W. -L. Su4, P. McDonough4, and M. Wiedmann5. (1) Food Science, Cornell Univ., 116 Stocking Hall, Ithaca, NY 14853, (2) Cornell University, Ithaca, NY 14853, (3) Dept. of Food Science, Cornell Univ., 412 Stocking Hall, Ithaca, NY 14853 Nontyphoidal Salmonella causes an estimated 1.4 million foodborne illnesses and over 500 deaths annually in the United States. This accounts for almost 10% of the illnesses and approximately a third of the deaths caused by known foodborne pathogens. The rise of antibiotic resistant Salmonella presents a particular concern, especially the appearance of certain Salmonella subtypes resistant to ceftriaxone. Not only is ceftriaxone the drug of choice for treatment of invasive cases of Salmonella in children, but it is also closely related to ceftiofur, a 3rd generation cephalosporin with widespread use in cattle. Beef and dairy products account for 10% of reported food borne Salmonella outbreaks, and transmission of antibiotic resistant Salmonella from dairy cattle to humans has been documented. In order to develop a better understanding of the evolution and transmission of ceftiofur-resistant Salmonella we characterized ceftiofur resistant and sensitive Salmonella isolates from 7 dairy farms with a history of ceftiofur use. A total of 47 isolates from these seven farms were analyzed for evolutionary relatedness by DNA sequencing of the Salmonella genes fimA, manB, and mdh , antibiotic-resistance profiling, and detection of CMY-2, a beta-lactamase gene associated with resistance to cephalosporins. Our data indicates that: (i) ceftiofur resistant Salmonella isolated from farms represent multiple distinct subtypes and evolutionary lineages as determined by serotyping, DNA sequence typing, and antibiotic-resistance profiling; (ii) ceftiofur resistant Salmonella evolved by multiple horizontal gene transfers of an identical CMY-2 allele; (iii) resistance to ceftriaxone and ceftiofur are highly correlated with the presence of CMY-2; and (iv) ceftiofur resistant Salmonella are geographically widespread as shown by their isolation from farms located throughout New York state. Continued monitoring of ceftriaxone and ceftiofur resistance in animals, food, and human associated Salmonella will be critical to detect spread and emergence of CMY-2 along the food chain.
Session 33, Food Microbiology: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |