|Thomas, Lee - USDA-FSIS-NVSL|
Submitted to: Swine Research Report
Publication Type: Proceedings
Publication Acceptance Date: December 1, 1996
Publication Date: N/A
Technical Abstract: As part of a National Animal Health Monitoring Survey - Swine 95 pre-test, we evaluated two culture methods for the isolation of Salmonella from fecal samples. Fecal samples (715 samples from 15 swine herds) were collected and transported to the lab. One gram of feces was placed into each of 10 ml of tetrathionate broth (Tet) or GN Hajna broth (GN) and incubated overnight at 37 deg C. At 24 h and 48 h for GN and Tet, respectively, approximately 100 ul was transferred into Rappaport R-10 medium (GN-R and T48-R). GN-R and T48-R were incubated overnight at 37 deg C, then struck onto brilliant green agar with sulfadiazine (BGS). Additionally, the 48 h Tet culture (T48) was also struck onto BGS. 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%). Culture in GN-R was least sensitive. Identification of positive herds or feedlots was best achieved by culture in T48-R (83.3%) when compared to either Tet alone (50%) or GN-R (33.3%). 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 demonstrate that Salmonella spp. is more likely to be recovered following use of both tetrathionate broth and Rappaport R-10 medium than any other medium.