Submitted to: American Society for Microbiology Branch Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 10/15/1999
Publication Date: N/A
Technical Abstract: The objective of this study was to streamline the detection and identification of Listeria monocytogenes (LM) in livestock and foods. Hog tonsil scrapings, hog tissues collected at necropsy, ground pork, and turkey washes were inoculated into UVM 1 (10% w/v) and after incubation (3 days), transferred to UVM 2. After 2 days, samples were plated to Palcam agar, which is incubated for 48 hrs. Characteristic LM colonies were verified using the multiplex PCR assay, which targets the 16S rRNA gene of Listeria and the hlyA gene unique to the species monocytogenes. To determine when LM achieved detectable levels during enrichment, template DNA was extracted directly from UVM 2, Palcam agar and screened by multiplex PCR. When screened directly from UVM 2 by PCR, 34% (65 of 190) of ground pork samples and 19% (11 of 60) of turkey washes were positive for LM. In contrast, multiplex PCR screening of colonies from Palcam agar showed 39% (75 of 190) of ground pork and 29% (18 of 60) of turkey washes were positive. Future studies will focus on improved recovery from UVM 2 with immunomagnetic beads. LM positive isolates of ground pork (n=33) were serotyped and assigned to type 4 (72%) and type 1 (14%); 14% of isolates were neither serotype 1 nor 4. For live hogs, out of 150 samples each of carcasses, tonsils, and ileocecal lymph nodes tested, LM was detected once from tonsils and nodes by multiplex PCR. In contrast, LM was found in 30% of ground pork produced that same day from the packing plant. This indicates widespread contamination of pork during production.