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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Food Safety and Enteric Pathogens Research » Research » Publications at this Location » Publication #127691
Title: DETECTION OF LISTERIA MONOCYTOGENES IN PIGS AND PORK

Author
item KANUGANTI, S - ALL PETS ANIMAL HOSPITAL
item WESLEY, IRENE
item REDDY, P - TUSKEGEE UNIVERSITY
item MCKEAN, J - IOWA STATE UNIVERSITY
item HURD, HOWARD

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2002
Publication Date: 9/20/2002
Citation: KANUGANTI, S.R., WESLEY, I.V., REDDY, P.G., MCKEAN, J., HURD, H.S. DETECTION OF LISTERIA MONOCYTOGENES IN PIGS AND PORK. JOURNAL OF FOOD PROTECTION. 2002. V. 65. P. 1470-1474.

Interpretive Summary: Listeria monocytogenes is a major human bacterial foodborne pathogen, which in the U.S. causes an estimated 2,500 cases and 500 deaths at a projected cost of $233 million annually. We surveyed live hogs (n = 300) as well as pork products for L. monocytogenes. We used a multiplex PCR assay, which distinguishes L. monocytogenes from other Listeria species to screen enrichments (Method 1) and to confirm presumptive Listeria colonies from the selective agar (Method 2). Subculture to Palcam agar (Method 2) was more sensitive based on recovery of L. monocytogenes from hog tissues (2.38% positive), ground pork (45% positive), and chitterling (9%) samples. This suggests that there may be PCR inhibitors present in the enrichment broth, which are eliminated by subculture to selective agar. This information may be useful to laboratories which are developing rapid methods to detect L. monocytogenes and other Listeria species in hogs and pork.

Technical Abstract: Listeria monocytogenes is a major human bacterial foodborne pathogen, which in the U.S. causes ~ 2,500 cases and 500 deaths at a cost of $233 million annually. We surveyed live hogs (n = 300) as well as pork products for L. monocytogenes. Pig specimens collected before (tonsil swabs) and after slaughter (tonsils, lymph nodes, carcass swabs, and rectal contents) were screened for the presence of L. monocytogenes using conventional enrichment broths followed by subculture to selective agar. A multiplex PCR assay, which targets the highly conserved 16S rRNA gene of the Listeria species as well as hlyA gene unique to L. monocytogenes, was used to screen aliquots of the University of Vermont (UVM) enrichment (Method 1) as well as to confirm presumptive Listeria colonies from the selective agar (Method 2). Method 2 was the more sensitive of the two methods, based on the overall detection of Listeria species other than L. monocytogenes. To illustrate, for hog tissues, Method 1 detected L. monocytogenes (0.87% positive) and no other Listeria spp. in all samples (n=1,849); Method 2 improved detection of L. monocytogenes (2.38% positive) and other Listeria spp. (0.38% of samples positive). Ground pork (n=340) harbored L. monocytogenes (45% positive) and other Listeria spp. (1.5% of samples positive) by Method 1. Subculture to Palcam (Method 2) improved detection of L. monocytogenes (50.2% of samples positive) and other Listeria species (1.7% of samples positive). Prevalence data obtained for L. monocytogenes in market weight hogs and pork may be used in future studies to assess the public health impact of meat