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Title: Antimicrobial Resistance in Salmonella Isolates Recovered from Slaughter Cattle

Author
item Cray, Paula
item ANANDARAMAN, N - Food Safety Inspection Service (FSIS)

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/27/2009
Publication Date: 5/27/2009
Citation: Cray, P.J., Anandaraman, N. 2009. Antimicrobial Resistance in Salmonella Isolates Recovered from Slaughter Cattle. International Conference on the Use of Antimicrobials in Cattle Production. May 27 - 29, 2009. Manhattan, KS. 86-121.

Interpretive Summary:

Technical Abstract: *Background*: Antimicrobial resistance is of global concern and first emerged in bacteria shortly after the introduction of penicillin. It is common to see resistance develop after new compounds (regardless of class) are released. However many factors influence the persistence and transmission of resistant bacteria. Initially, resistance to a few antimicrobials was not of major concern. However, because bacteria develop genetic mechanisms (including resistance mechanisms) to ensure their survival, antimicrobial resistance to 5 or more antimicrobials emerged. This becomes problematic as fewer options are available for treatment. Resistance among primarily human pathogens such as *Mycobacterium tuberculosis* has resulted in the emergence of untreatable strains. Resistance among zoonotic bacteria is a public health concern. In particular, research has focused on pathogens such as *Campylobacter* and *Salmonella*. Resistance between and among *Salmonella* serotypes is not equal as differences between animal source are observed. *Purpose*: We report on the antimicrobial resistance trends among the top *Salmonella* serotypes isolated from cattle. *Methods*: From 1997 to 2008, isolates submitted to NARMS were tested for susceptibility to 14 core antimicrobials using a custom made panel and a semi-automated broth microdilution system (Sensititre, Trek Diagnostics, Cleveland, OH). MDR is defined as resistance to *>* 2 antimicrobials. *Results*: From 1997 to 2008, 68.9% (n=5569/8084) of isolates originating from cattle are pan-susceptible as reported through the National Antimicrobial Resistance Monitoring System-Animal Arm. Resistance is most often observed to tetracycline (2,247/8084; 27.8%). The MDR pattern most often observed is to amoxicillin/clavulanic acid, ampicillin, ceftiofur, chloramphenicol, streptomycin, sulfonamides and tetracycline (5.1%, n=410/8084). The serotypes contributing to the top MDR pattern are Newport 61.9% n=254/410), Typhimurium (11.2%, n=46/410) and Reading (9.3%, n=38/410). In contrast, the serotypes contributing the most to the pan-susceptible category are Montevideo (20.1%, 1121/5569), Muenster (9.5%, 528/5569) and Anatum (9.2%, 515/5569). *Discussion*: These data indicate that resistance, including MDR, varies by serotype and source. Continued monitoring and further characterization of isolates is warranted. *References*: National Antimicrobial Resistance Monitoring System, Athens, GA. Accessed May 20, 2009. http://www.ars.usda.gov/Main/docs.htm?docid=6750*.