|HOGAN, KELLIE - Anitox Corp|
|HOLCOMBE, N - Anitox Corp|
|WELLER, C - Anitox Corp|
|GUMM, A - Anitox Corp|
|Cox, Nelson - Nac|
|CASON, JOHN - Retired ARS Employee|
|RICHARDSON, KURT - Retired ARS Employee|
|STREET, P - Anitox Corp|
Submitted to: Poultry Science Association Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/3/2015
Publication Date: 7/27/2015
Citation: Hogan, K.M., Holcombe, N., Weller, C., Gumm, A., Cox Jr, N.A., Cosby, D.E., Cason, J., Berrang, M.E., Richardson, K., Street, P. 2015. Potential pitfalls of relying on hydrogen sulfide (H2S) production to identify Salmonella in feed [abstract]. Poultry Science Association Meeting Abstract. July 27-30, 2015. Louiville, Kentucky.
Technical Abstract: Salmonella can be difficult to assess and isolate in poultry feed due to stress, uneven distribution and poor growth. Previous studies have shown that several strains of Salmonella can be affected by environmental changes, resulting in H2S-negative colonies. This is a major concern, as H2S production, along with the inability to ferment lactose are the primary methods to recognize Salmonella colonies on selective media. The purpose of this research was to determine if incubation in selected media could revert H2S-negative colonies (yellow) to H2S-positive (black). Salmonella serotypes assessed were Enteritidis, Infantis, Montevideo, and Schwarzengrund. Strains were grown in non-stressed (NS) and stressed (S; dry inoculum in sterile meat and bone meal) environments. All (approx. 108 cfu/g) were added to pH 7 citrate buffer and incubated at 35°C overnight. Samples were plated on Xylose-Lysine-Tergitol-4 (XLT-4) media, grown overnight at 35°C, and then assessed for yellow colonies. Yellow colonies were subsequently picked and grown in five separate broths overnight (Universal Pre-enrichment Broth, Trypticase Soy Broth, Brain Heart Infusion broth, Nutrient broth, Tetrathionate-Hajna (at 35°C and 42°C) and Rappaport-Vassialdis). 100 uL of each sample was plated on XLT-4 media and the percentages of yellow and black colonies were recorded after 24 and 48 h incubation at 35°C. All S. Enteritidis (S and NS) and S. Schwarzengrund (NS) colonies had reverted to H2S production and were black. However, S. Schwarzengrund (S) was more variable depending on media. S. Montevideo showed the most H2S reversion, with 100% reversion in all media 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 organisms and 0% reversion for stressed organisms. The results from this study suggest that while H2S production may be a useful way to recognize Salmonella in feed, pH and stress can have an impact on the production of H2S, and thus, make it difficult to properly isolate or biochemically classify Salmonella. This has major implications for analytical and food production laboratories, as it is possible that false negative results could be reported.