INTEGRATION OF HYDROXYAPATITE CONCENTRATION OF BACTERIA AND SEMINESTED PCR TO ENHANCE DETECTION OF SALMONELLA TYPHIMURIUM FROM GROUND BEEF AND BOVINE CARCASS SPONGE SAMPLES

Abstract Hydroxyapatite (HA) concentration of bacteria from 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 10⁵ 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 CFU/mL (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.