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ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Poultry Microbiological Safety and Processing Research Unit » Research » Publications at this Location » Publication #300302

Title: Injury and death of various Salmonella serotypes under acidic conditions during pre-enrichment

item Cox Jr, Nelson
item RICHARDSON, K - Anitox Corp
item CASON, J - Retired ARS Employee
item Rigsby, Luanne
item Cosby, Douglas

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/15/2013
Publication Date: 1/28/2014
Citation: Cox Jr, N.A., Richardson, K.E., Cason, J.A., Rigsby, L.L., Cosby, D.E. 2014. Injury and death of various Salmonella serotypes under acidic conditions during pre-enrichment [abstract]. Meeting Abstract. p. 55.

Interpretive Summary:

Technical Abstract: A previous study showed that after incubation in commonly used pre-enrichment media, mixed feeds and feed ingredients reached a pH (4.0 to 5.0) capable of injuring or killing Salmonella. The objective of this study was to subject four (4) different Salmonella serotypes to pHs of 4.0, 4.5 and 5.0 for either 6 or 24 hours to determine percent injury and death. Approximately 105 colony forming units (CFU’s) of S. Enteritidis (SE), S. Heidelberg (SH), S. Kentucky (SK) and S. Typhimurium (ST) were individually placed into 50 mL of a citrate buffer at the listed pHs for 6 or 24 hours at 37oC. After holding at 37oC, each serotype was serially diluted in sterile physiological saline and plated onto xylose lysine tergitol 4 (XLT4) for injury and nutrient agar (NA) for death. These plates were enumerated and percent injury and/or death determined. The injury and death confirmed that the pHs between 4.0 to 5.0 were detrimental to these Salmonella serotypes. At 24 hours, the % injury ranged from 89.4 to 100% and the % death ranged from 77.5 to 100% with ST being the most sensitive to injury and death and SH being the most resistant. More research is needed with additional Salmonella serotypes and strains to fully understand the difficulties of isolating Salmonella from feed. Researchers testing feed/feed ingredients for Salmonella may not be aware of the acidic nature of the pre-enrichment step and the subsequent injury or death. Current protocols may not be detecting Salmonella in samples containing fermentable substrates preventing the accurate detection of Salmonella.