ScienceDaily (Aug. 26, 2009) — A new study suggests that when compared to conventionally raised beef cattle, organic and natural production systems do not impact antibiotic susceptibility of Escherichia coli O157:H7. This discovery emphasizes that although popular for their suggested health benefit, little is actually known about the effects of organic and natural beef production on food-borne pathogens.

The researchers from Kansas State University detail their findings in the August 2009 issue of the journal Applied and Environmental Microbiology.

Increased outbreaks of foodborne illness, as well as the growing awareness and popularity of organic and natural foods, have forced many cattle farmers to adopt new production methods to meet consumer demand for safe and healthy beef. Organic food sources receive only certified organic feed, are raised without the use of antibiotics, hormones, and other veterinary products, and are regulated by the U.S. Department of Agriculture. Natural production guidelines completely restrict the use of antibiotics and hormones, but do allow nonorganic food sources and are only regulated by the brand name owner.

Cattle are major reservoirs of E. coli O157:H7 and their feces are the main source of food and water contamination that lead to foodborne illness in humans. In the study fecal samples were collected from organically and naturally raised cattle and tested for the presence of E. coli O157:H7. Results showed prevalence rates of 14.8 % in organically raised and 14.2 % in naturally raised cattle. These E. coli O157:H7 levels were comparable to those previously identified in conventionally raised cattle. Additionally, the minimum inhibitory concentration of a variety of antibiotics for E. coli O157:H7 isolates were analyzed to determine the effects of all three production systems and no significant difference in antibiotic susceptibility was noted.

"The prevalences of E. coli O157:H7 that we observed in organically and naturally raised beef cattle were similar to the previously reported prevalence in conventionally raised cattle," say the researchers. "No major difference in antibiotic susceptibility patterns among the isolates were observed."

Story Source:

Adapted from materials provided by American Society for Microbiology, via EurekAlert!, a service of AAAS.

Journal Reference:

1. S. Reinstein, J.T. Fox, X. Shi, M.J. Alam, D.G. Renter, T.G. Nagaraja. Prevalence of Escherichia coli O157:H7 in organically and naturally raised beef cattle. Applied and Environmental Microbiology, 2009; 75 (16): 5421-5423

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