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U.S. Department of Health and Human Services

Animal & Veterinary

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by Katherine Hollinger, D.V.M., M.P.H.
FDA Veterinarian Newsletter September/October 1999 Volume XIV, No V

Dr. Linda Tollefson and Dr. Katherine Hollinger of the FDA's Center for Veterinary Medicine (CVM), and Dr. Paula Fedorka-Cray of USDA's Agricultural Research Service (ARS), represented the National Antimicrobial Resistance Monitoring System-Enteric Bacteria (NARMS-EB) at a meeting of ResistVet collaborators in Morelia, Mexico to develop a plan to monitor for antimicrobial drug resistance in foodborne pathogens. This meeting was held in conjunction with the joint annual meetings of the Mexican Society of Infectious Diseases and the National Congress of Antimicrobials and Chemotherapy, held from June 30 to July 3, 1999, and oral presentations and poster sessions were conducted on nosocomial infections, antimicrobial resistance and many other topics.

The NARMS representatives met with ResistVet organizer Dr. Mussaret Zaidi of the Research Department in the O’Horan General Hospital, Yucatan and collaborator Dr. Alejandro Macia of the Department of Microbiology at the School of Medicine and Leon General Hospital to discuss plans to initiate the antimicrobial resistance monitoring program in 5 states in Mexico (Durango, Michoacan, Guanajuanto, Mexico City and Yucatan) and Guatamala. These five states and the site in Guatamala are located in areas with significant animal agriculture in close proximity to the monitoring centers. Much of the food consumed in these areas is locally produced, unlike food distribution in the United States that is distributed nationally and internationally. The monitoring program will target the foodborne pathogens, salmonella and campylobacter. Planning of the surveillance program focused on the numbers and potential sources of isolates, technical and laboratory methodology and resources available to implement the system. Isolates will be obtained from clinical human sources from hospital and daycare settings, from retail food, and from live, healthy animals in collaboration with producers and veterinarians. Testing will be conducted at the hospital laboratories and results will be pooled into a database.

In the joint meeting of the WHO-Resistnet and ResistVet participants the NARMS-EB representatives presented information describing the NARMS-EB program and gave a review of some of the data collected from the program in 1998. Dr. Tollefson gave an overview of NARMS-EB, the objectives, achievements and limitations of the monitoring program. The program collects isolates of foodborne pathogens: E. coli, salmonella and campylobacter isolates, from clinically affected humans, food animals at slaughter and diagnostic laboratory isolates. The resistance patterns of the salmonella isolates are determined by microbroth dilution to seventeen antimicrobial drugs and by E-test to eight antimicrobials for campylobacter isolates. The laboratory methods used to test the isolates are identical for the human and animal portions of the program. The human isolates are submitted from fifteen sites nationally and tested at the Centers for Disease Control and Prevention in Atlanta. The animal isolates are collected from slaughter plants, processing plants and the National Veterinary Services Laboratory and tested at USDA's Agricultural Research Service in Athens, Georgia. The objectives of the program are to provide timely information to veterinarians and physicians, prolong the lifespan of approved drugs, provide descriptive data on the trends in antimicrobial susceptibility of salmonella from human and animal populations and identify areas for more detailed investigation.

Dr. Hollinger presented a talk on "Multi-drug resistance in Salmonella isolates from poultry at slaughter" and Dr. Fedorka-Cray presented "An overview of antimicrobial resistance in Campylobacter and related research." Other presentations described antimicrobial drug resistance patterns in salmonella and campylobacter, water contamination and antimicrobial resistance patterns on poultry and swine farms in Yucatan.

Data was presented from the 15 hospital-based centers distributed throughout Mexico, Costa Rica and Guatamala, in the Resistnet surveillance program begun in 1996. The surveillance program has tested susceptibility of over 5,000 clinical human isolates of E. coli, Staph. aureus, Pseudomonas aeruginosa, Salmonella and Shigella to commonly used antimicrobials. E. coli was the most commonly isolated organism tested in the program and represented 22 percent of all isolates. A 1996 Mexico City study of 70 children with symptoms of enteric disease indicated 46 percent requiring antibiotic treatment. A second study conducted in 1997 of 19 children observed for 20 weeks indicated that up to 70 percent of ill children received antibiotics for treatment of severe diarrheas. Molecular microbiological techniques were described for epidemiologic surveys of the isolates to identify clusters and potential outbreaks. Bayer representative, Dr. Raul Vazquez, described the company’s strategy for the responsible use of antibacterials in Latin America and provided background information on food animal drug use in Mexico.

The meeting concluded with discussion of the protocol for the proposed monitoring program. The program will be implemented in August with the testing of 50 to 100 samples per site for isolation of Salmonella for four consecutive weeks. The first samples will be collected from daycare centers and collection of approximately 50 salmonella isolates is expected. The Epidemiology Department at the School of Veterinary Medicine in Yucatan will be participating in the program, providing animal isolates for the program. Other areas planned for inclusion in the program are testing of seafood for Salmonella, Vibrio cholera and Shigella.

Proposed next steps include plans to exchange advanced training in isolation and susceptibility testing of foodborne pathogens, training in laboratory methodology and technology transfer. Surveillance will be implemented in a stepwise manner to begin with sampling for Salmonella from children in daycare settings and will expand to include retail poultry isolates. Incorporation of other sources of human and animal samples and addition of Campylobacter are planned for next year.

This collaboration between NARMS and the Mexican ResistVet group is the initiation of the first international monitoring system for foodborne pathogen surveillance and antimicrobial drug susceptibility monitoring in the Americas. Long-term goals include development of an international database to make information available to prevent outbreaks of foodborne disease and identify emerging pathogens.