Feedstuffs Magazine Resistance casts shadow on antibiotic regulatory decisions By SALLY SCHUFF Feedstuffs Washington Editor November 12, 2001 HERSHEY, PA. -- Current changes in the scientific and regulatory climate surrounding the use of antibiotics in livestock production were a major discussion topic during last week’s meeting of the U.S. Animal Health Assn. (USAHA) here. Dr. Paul Sundberg of the National Pork Board told USAHA's pharmaceutical committee that the American Society of Microbiology (ASM), the nation’s foremost scientific society on antibiotic issues, currently is undertaking a major investigation of antibiotic resistance issues in agriculture. ASM, he said, is in the process of laying the groundwork for a major report on the role of antimicrobials in agriculture. That report, according to Sundberg, will cover current antibiotic usage focused on animal agriculture, why those antibiotics are important, how they help and the consequences of changing the way they are currently used. The ASM report is due out in late May 2002. Sundberg said ASM is addressing the subject of antibiotics because it recognizes the need for a benchmark scientific review of the issues. "We’re in a climate where we have regulatory decisions that need to be made," Sundberg said. "And, we’re in the mode that those are having an effect, intended or unintended, on animal production and pharmaceuticals." Sundberg said the ASM meeting was also an attempt to begin the major collaborative effort that will be needed to have meaningful surveillance, diagnosis and risk management strategies. The current regulatory climate will drive the need for pooling scientific expertise, Sundberg said. He said the ASM meeting held "promise for bringing together some of the people that can show us the direction we have to go." Among the new science that is clearly driving the regulatory climate are several studies by the University of Maryland published last month in the New England Journal of Medicine. They will add impetus for ongoing and additional studies of antibiotic use in meat and egg production. The University of Maryland’s study that found salmonella in 20% of the ground meat purchased at Washington, D.C., area grocery stores was discussed at the USAHA meeting by Dr. Stephen F. Sundlof, director of the Food & Drug Administration’s Center for Veterinary Medicine (CVM). That study, he said, found 13 serotypes of salmonella in 41 of 200 samples of retail ground meats. Of the 41 salmonella isolates, which included 13 serotypes, a total of 84% were resistant to at least one antibiotic. Sundlof reported that "16% were resistant to ceftriaxone -- the drug of choice for treating children with salmonellosis -- a disturbing finding." The 17 antibiotics in the University of Maryland study were the same antibiotics routinely surveyed in the ongoing National Antibiotic Resistance Monitoring System study. The University of Maryland study also found multi-drug resistant Salmonella typhimurium DT 208 and 104 in the retail ground meat samples, Sundlof said. That is significant because the organisms can cause severe illness, he reported, noting that they are "usually resistant to ampicillin, chloramphenicol, streptomycin, sulfonamides and tetracyclines. The antibiotic-resistant microbes were recovered from the meat before it was cooked. Nonetheless, the findings have prompted concern in the scientific community, he said. The number of cases of DT 104 has increased worldwide, Sundlof said. The Center for Disease Control & Prevention has reported that the percentage of isolates resistant to the antibiotics above has increased from 0.6% in 1980 to 34% in 1996. Sundlof said the isolation of DT 208 from ground meats "also is a concern because of the extensive patterns of resistance of this organism." Another study of retail ground meat is currently underway at Iowa State University. One of the scientists attending the USAHA meeting in Hershey noted during discussion of antibiotic resistance at the pharmaceutic committee meeting. He said the study also suggested "the use of ceftiofur in livestock accelerated the development of resistance to ceftriaxone in salmonella." Together with earlier studies, Sundlof said, the findings seem to indicate that "foods from animals are potential sources of ceftriaxone-resistant salmonella that infects humans." The link, however, he said, has not yet been made. A concurrent study also published by the New England Journal of Medicine has prompted CVM to investigate the use of ceftiofur and gentamicin in embryonated eggs, Sundlof reported. CVM suspects the egg production practice "contributes to ceftiofur and gentamicin resistance if the drug are used on the chickens and turkeys later in life." CVM plans to poll producers using a questionnaire designed to gather more data. CVM epidemiologists will be reviewing the questionnaires for the next few months. In a separate presentation, Dr. Eric Bush, an epidemiologist with NAHMS located at Ft. Collins, Colo., reported on the survey of antibiotic use in swine. That survey is scheduled to be published in January and will be on the NAHMS web site. Bush said the study showed that antibiotic usage can be measured, but those measurements do not accurately reflect a measurement of selection pressure for genetic resistance. He said his survey concluded that livestock feed is the primary vehicle used for antibiotics intended to promote growth and prevent disease. In another report, the committee also reviewed data from work done by Dr. Isabelle Moreau, a veterinarian who works with antibiotic-free pork producers. Her report, presented at the meeting by pharmaceutical committee chairman Dr. Roy A. Schultz, suggested that while pigs could be raised without antibiotics, cost increases of about 20% would occur due to disease and death loss. Copyright 2001, The Miller Publishing Company, a company of Rural Press Ltd. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - For SC email list T-and-C, send: GET TERMS-AND-CONDITIONS.CURRENT to [log in to unmask]