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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Food Safety and Enteric Pathogens Research » Research » Publications at this Location » Publication #160446
Title: CULTURE METHODS DIFFER ON THE ISOLATION OF SALMONELLA ENTERICA SEROTYPES FROM NATURALLY CONTAMINATED SWINE FECAL SAMPLES

Author
item Rostagno, Marcos
item Gailey, Jared
item Hurd, Howard
item MCKEAN, J - IOWA STATE UNIVERSITY
item LEITE, R - FED UNIV MINAS GERAIS

Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2004
Publication Date: 1/20/2005
Citation: Rostagno, M.H., Gailey, J.K., Hurd, H.S., McKean, J.D., Leite, R.C. 2005. Culture methods differ on the isolation of Salmonella enterica serotypes from naturally contaminated swine fecal samples. Journal of Veterinary Diagnostic Investigation. 17(1):80-83.

Interpretive Summary: Despite advances in new diagnostic methods, conventional bacteriological culture methods remain the foundation of studies on the ecology and epidemiology of Salmonella in livestock. The diagnostic sensitivity of the culture methods applied is critical for epidemiological studies, as its improvement will allow reducing sample size requirements, and consequently costs. Interesting to note is that, although critical, this topic is not usually included in the discussion of most of the published studies on Salmonella enterica ecology and epidemiology in swine populations. In this study, four bacteriological culture methods (A, B, C, and D) were comparatively evaluated for their ability to isolate Salmonella enterica serotypes from naturally contaminated swine fecal samples. None of the methods was able to isolate Salmonella from all positive samples. Methods B and C performed significantly better than methods A and D. Although methods B and C were equivalent for the detection of Salmonella in the fecal samples tested, there was a marked divergence on the isolation of different serotypes (no match). This study demonstrates that culture methods affect investigations on ecology and epidemiology of S. enterica in swine, due to their diverging ability to detect positive samples and different serotypes. Although culture methods constitute the basis for Salmonella investigations, there is still a need for standardization of the methods applied, as well as continuous improving and comparative studies in order to establish parameters for comparison of results from different studies. Results from this study will be useful to diagnostic and surveillance laboratories and researchers.

Technical Abstract: To comparatively evaluate four culture methods for the isolation of Salmonella enterica from naturally contaminated swine fecal samples. Four culture methods (A, B, C, and D) were comparatively evaluated for their ability to isolate Salmonella enterica from pooled swine fecal samples (n = 100). None of the methods was able to isolate Salmonella from all positive samples. The relative sensitivity of the culture methods evaluated was; 82% for method A, 94% for method B, 95% for method C, and 78% for method D. The comparison of sensitivities showed that methods B and C performed significantly better (p < 0.05) than methods A and D. Although relative sensitivities of methods B and C were equal, from the 89 positive samples detected by both, 35 (39.3%) had different serotypes (no match) isolated by each method. Culture methods differ on the isolation of Salmonella enterica serotypes from naturally contaminated swine fecal samples. Depending on the objective(s) of investigations on the ecology and epidemiology of Salmonella enterica in swine populations, a method or a combination of methods should be considered for more reliable results. Ecological and epidemiological investigations of Salmonella enterica are greatly affected by the culture method applied, justifying more studies.