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Am J Vet Res. 1999 Mar;60(3):359-62.

Effects of sample storage and delayed secondary enrichment on detection of Salmonella spp in swine feces.

Author information

1
Department of Food Animal and Equine Medicine, College of Veterinary Medicine, North Carolina State University, Raleigh 27606, USA.

Abstract

OBJECTIVE:

To determine effects of fecal sample storage and delayed secondary enrichment (DSE) on detection of Salmonella spp in swine feces. Sample Population-Fecal samples obtained from 84 pigs in a commercial herd.

PROCEDURE:

Each fecal sample underwent 3 storage treatments: no storage (ie, processed on the day of collection), storage at 4 C for 6 days, and storage at -15 C for 14 days. After assigned storage treatments, all samples were enriched in Rappaport-Vassiladias (RV) broth (single enrichment) and plated on XLT4 agar. Delayed secondary enrichment was performed, using single enrichment broths that were stored for 4 days at room temperature.

RESULTS:

Of 504 cultures, 186 (36.9%) were Salmonella positive. A difference in proportions of samples with positive results was not found between same-day processing and storage at 4 C for 6 days. Compared with use of single enrichment for 24 hours (34% positive), use of DSE resulted in a greater proportion (40%; P < 0.001) of samples with positive results. Estimated relative sensitivities for the storage methods were 0.90, 0.85, and 0.71 for same-day processing, storage at 4 C for 6 days, and storage at -15 C for 14 days, respectively.

CONCLUSIONS:

Where practical, processing of fecal samples on the day of collection is recommended, although storage at 4 C for several days does not result in marked loss of sensitivity. Improved detection associated with DSE warrants further investigation and optimization.

PMID:
10188820
[Indexed for MEDLINE]

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