|Cox, Nelson - Nac|
Submitted to: International Poultry Scientific Forum
Publication Type: Abstract Only
Publication Acceptance Date: 11/10/2014
Publication Date: 2/27/2015
Citation: Hogan, K.M., Holcome, N., Weller, C., Postel, M., Gumm, A., Cox Jr, N.A., Cosby, D.E., Cason, J., Berrang, M.E., Richardson, K., Street, P. 2015. Reversion of stressed and unstressed hydrogen sulfide (H2S) producing strains of Salmonella in different media.. International Poultry Scientific Forum. January 27-29, 2015. Atlanta, Georgia. P75. Interpretive Summary:
Technical Abstract: Salmonella can be difficult to assess and isolate in poultry feed due to uneven distribution and poor growth. Previous studies have shown that several strains of Salmonella can be affected by changes in environment, resulting in the growth of H2S-negative colonies. This is concerning, as H2S production is the main way to isolate Salmonella colonies on selective media, as well as to identify the organism. The purpose of this research was to determine if incubation in selected media could revert H2S-negative colonies (yellow) to H2S-positive (black). Strains assessed were S. Enteritidis, S. Infantis, S. Montevideo and S. Schwarzengrund. Strains were grown in non-stressed (NS) and stressed (S; dry inoculum in meat and bone meal) environments. All were added to pH 7.0 citrate buffer and incubated at 35oC overnight. Samples were plated on XLT-4 media, grown overnight at 35oC and then assessed for yellow colonies. Yellow colonies were then grown in several media broths overnight, including UPB, TSB, BHI, Nutrient, TT (at 35oC and 42oC) and RV. Samples were plated onto XLT-4 media and the percentages of yellow and black colonies were recorded after 24 and 48 h incubation at 35oC. All S. Enteritidis (S and NS) and S. Schwarzengrund (NS) colonies were black and showed no H2S production loss. However, S. Schwarzengrund (S) was more varied dependent on media. S. Montevideo showed the most H2S reversion, with 100% reversion in all medias for the (NS), and an average of 92% reversion for the (S) organism. S. Infantis showed the least amount of reversion, with an average of 4% reversion for (NS) and 0% reversion overall for the (S). The results from this study suggest that while H2S production may be a useful way to confirm Salmonella in feed, pH and a temperature stressed environment can have an impact on the production of H2S, and thus, make it difficult to properly isolate or biochemically confirm the identity of the organism. This has major implications for analytical and food production laboratories, as it is possible that false negative results could be reported.