|Thomas, Lee - USDA-FSIS-NVSL|
Submitted to: Food Safety Consortium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: October 26, 1995
Publication Date: N/A
Technical Abstract: We evaluated two culture methods for the isolation of Salmonella from fecal samples. Fecal samples (715 samples from 15 swine herds and 4,977 samples from 100 feedlots) were placed into tetrathionate (Tet) or GN Hajna broth (GN) (1 g feces/10 ml media) and incubated overnight at 37 deg C. At 24 h and 48 h for GN and Tet, respectively, approximately 100 ul was transferred dinto Rappaport R-10 medium (GN-R and T48-R). GN-R and T48-R were incubate overnight at 37 deg C, then struck onto brilliant green gar with sulfadiazine (BGS). Additionally, the 48 h Tet culture (T48) was also struck onto BGS. For the swine samples, all culture media was also struck onto xylose-lysine-Tergitol 4 and brilliant green agar with novobiocin. All plates were incubated overnight at 37 deg C. Colonies having the typical appearance of Salmonella were picked to triple sugar iron and lysine iron agar slants and incubated overnight at 37 deg C. Presumptive positive isolates were serogrouped and subsequently serotyped at the National Veterinary Services Laboratories. Salmonella spp. were most often recovered from samples cultured in T48-R (93% for swine; 77.3% for bovine feces). Culture in GN-R was least sensitive. Identification of positive herds or feedlots was best achieved by culture in T48-R when compared to either Tet alone or GN-R. T48-R was also more likely to identify all positive isolates from either herd or feedlots than either Tet alone or GN- R. No differences between plating media were observed. These data indicate that Salmonella spp. have a higher probability of being recovered following use of both tetrathionate broth and Rappaport R-10 medium than any other medium.