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United States Department of Agriculture

Agricultural Research Service

Research Project: EPIDEMIOLOGY, ECOLOGY, AND MOLECULAR GENETICS OF ANTIMICROBIAL RESISTANCE IN PATHOGENIC AND COMMENSAL BACTERIA FROM FOOD ANIMALS

Location: Bacterial Epidemiology and Antimicrobial Resistance

Title: Antimicrobial Resistance in Salmonella Isolates Recovered from Eggs

Authors
item Cray, Paula
item Cox, Nelson
item Musgrove, Michael
item Frye, Jonathan
item Richardson, Larry
item Plumblee, Jodie
item Haro, Jovita
item Anandaraman, N -

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 3, 2009
Publication Date: April 8, 2009
Citation: Cray, P.J., Cox Jr, N.A., Musgrove, M.T., Frye, J.G., Richardson, L.J., Plumblee, J., Haro, J.H., Anandaraman, N. 2009. Antimicrobial Resistance in Salmonella Isolates Recovered from Eggs. Egg Industry Center 2009 Egg Industry Issues Forum. April 8, 2009. Des Moines, IA. 9-10.

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. S. Kentucky, S. Enteritidis and S. Heidelberg are among the serotypes most often recovered from chickens. These same serotypes are also among the top three recovered from eggs, although Kentucky and Heidelberg switch places. Of these three serotypes, Enteritidis and Heidelberg appear to cause more clinical disease in humans than Kentucky. It is interesting to note that resistance, including multiple drug resistance (MDR), among Enteritidis is significantly less than that observed for the other serotypes. Purpose: We report on the antimicrobial resistance trends among the top Salmonella serotypes isolated from eggs. Methods: 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 is greater than or equal to 2 antimicrobials. Results: Greater than 98% of isolates originating from eggs are pan-susceptible as reported through the National Antimicrobial Resistance Monitoring System-Animal Arm. Resistance is most often observed to tetracycline (35/765; 4.6%). MDR is uncommon, particularly among Enteritidis isolates. The MDR pattern most often observed for Heidelberg and Kentucky is to streptomycin and tetracycline (0.6%, n=2/275 and 16.7%, n=9/54, respectively). In contrast, the top 3 MDR among isolates originating from broiler chickens was - Kentucky (49.3%, n=219), Enteritidis (0.9 %, n=115) and Heidelberg (23.4 %, n=94). Discussion: These data indicate that resistance, including MDR, varies by serotype and source. Salmonella isolates originating from eggs appear to be highly pan-susceptible indicating that virulence factors other than those attributed to antimicrobial resistance likely play a role in human disease. Continued monitoring and further characterization of isolates is warranted. References: Musgrove, M.T., D.R. Jones, J.K. Northcutt, N.A. Cox, M.A. Harrison, P.J. Fedorka-Cray, and S.R. Ladely. 2006. Antimicrobial resistance in Salmonella and Escherichia coli isolates from commercial shell eggs. Poultry Sci. 85:1665-1669 National Antimicrobial Resistance Monitoring System, Athens, GA. Accessed March 13, 2009. http://www.ars.usda.gov/Main/docs.htm?docid=6750.

Last Modified: 8/2/2014