U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska


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Published in Journal of Rapid Methods and Automation in Microbiology 7 (1999) 7-23.


Hydroxyapatite (HA) concentration of bacteriafiom ground beef and bovine carcass sponge samples was examined as a method to enhance the PCR detection of Salmonella typhimurium in these samples. Ground beef and carcass sponge samples were inoculated with progressively lower levels of S. typhimurium. Concentrated (10% HA) and unconcentrated samples were prepared for PCR after 0, 2, 3, or 4 h of nonselective enrichment. Without HA concentration and enrichment, Salmonella in ground beef was not detected by seminested PCR, even when present at levels of 103 cells/mL in the 1:10 ground beef homogenates. However, when bacteria in these samples were extracted with HA, limits of detection in nonenriched samples were 102-103 CFU/mL and in enriched samples were 101 CFU/mL (after 2 and 3 h enrichment) and 100 CFWmL (after 4 h enrichment). Without concentration or enrichment, the limit of detection of Salmonella in carcass sponge samples was 103 cells/mL. HA concentration of these samples lowered this limit to 100- 101 CFU/mL. Nine of 14 different Salmonella serotypes adhered to HA at proportions of 98.0% or more.