Environmental testing for Salmonella Enteritidis is required for U.S. shell egg producers with > 3,000 hens on a farm. The egg producer assumes all costs for the mandatory testing. According to the FDA Egg Rule, either manure scraper or drag swabs can be collected according to published guidelines and requirements. The current study was undertaken to determine the efficacy of Salmonella detection in single, two, and four swab pools of either manure scraper or drag swabs. Resistant isolates of Salmonella Enteritidis (1000 ppm streptomycin; SE), Heidelberg (200 ppm nalidixic acid (NA); SH), Typhimurium (200 ppm NA; ST), and Kentucky (200 ppm NA; SK) were utilized. Low (approximately 8.4 CFU) and high (approximately 84 CFU) dose inocula were introduced onto a single swab within a pool. A single flock of each conventional cage (manure scraper swabs) and cage-free barn (drag swabs) were monitored throughout the study at the ages required under the FDA Egg Rule. The greatest and most consistent recovery of inoculum was found in single swab samples. For low dose inocula, it was difficult to recover isolates from single manure scraper swabs (57.9 – 29.2 %) and decreased as more swabs were added to the pool. Recovery of isolates in manure scraper swabs was greater for high dose inoculum, though SH exhibited difficulty competing with naturally occurring flora. One and two swab pools of drag swabs had similar rates of recovery at both low and high dose SE, SH, and ST. When SE and SK were combined in an inoculum, SE was recovered at a much higher rate than SK for all types of swabs and doses of inocula. Pooling of two drag swabs allowed for similar detection of low and high dose Salmonella tested in the current study, but the pooling of manure scraper swabs decreased detection of low dose Salmonella .
Pooling of laying hen environmental swabs and efficacy of Salmonella spp. detection
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Deana R Jones, Richard K Gast, Prafulla Regmi, Garrett E Ward, Kenneth E Anderson, Darrin M Karcher; Pooling of laying hen environmental swabs and efficacy of Salmonella spp. detection. J Food Prot doi: https://doi.org/10.4315/JFP-19-467
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