Title: Impact of Pre-enrichment media pH on Salmonella detection Authors
Submitted to: Western Poultry Disease Conference
Publication Type: Proceedings
Publication Acceptance Date: December 2, 2013
Publication Date: April 2, 2014
Citation: Richardson, K.E., Cox Jr, N.A., Cason, J.A., Cosby, D.E., Derome, L. 2014. Impact of Pre-enrichment media pH on Salmonella detection. Western Poultry Disease Conference. Puerto Vallarta, Mexico, April 2-5, 2014. Interpretive Summary: Commercial poultry feed has been known to be a source of Salmonella for many years. Commonly used pre-enrichment media becomes very acidic when incubated with feed and feed ingredients due to extraneous bacteria and the presence of fermentable substrates such as corn. Acidic conditions may injure or kill Salmonella. These finding suggest that the acidity of the pre-enrichment media may influence whether or not Salmonella are actually detected and also what serotypes of Salmonella are recovered.
Technical Abstract: In a recent study, the ph of commonly used Salmonella pre-enrichment medias became acidic (pH 4.0 to 5.0) when feed/ingredient were incubated for 24 hrs. Acidic conditions have been reported to injure or kill Salmonella. In this study, non-stressed and stressed cultures of S. typhimurium (ST), S. enteritidis (SE), S. infantis (SI), S. senftenberg (SS) and S. montevideo (SM) were subjected to incubation pHs ranging from 4.0 to 7.0. Cell injury was determined on xylose lysine tergitol 4 (XLT4) and cell death determined on nutrient agar (NA). In the case of non-stressed Salmonella, ST and SE was observed to be the most tolerant to acidic conditions and SS, SM and SI observed to be the most sensitive. In the case of stressed Salmonella, the opposite tolerance/sensitivities among the isolates was observed. These finding suggest that the pH of the pre-enrichment media may influence the serotype of Salmonella recovered from feed.