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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 #211272
Title: LOW PREVALENCE OF LISTERIA MONOCYTOGENES IN CULL SOWS AND PORK

Author
item Wesley, Irene
item LARSEN, STEVEN - NATIONAL PORK BOARD,DM,IA
item HURD, HOWARD - IOWA STATE UNIVERSITY
item MCKEAN, JAMES - IOWA STATE UNIVERSITY
item GRIFFITH, RONALD - IOWA STATE UNIVERSITY
item RIVERA, FERNANDO - VET MED, VENEZUELA
item NANNAPANENI, RAMAKRISHNA - UNIVERSITY OF ARKANSAS
item COX, MANDY - UNIVERSITY OF ARKANSAS
item JOHNSON, MICHAEL - UNIVERSITY OF ARKANSAS
item WAGNER, DEAN - MN DEPT. OF AGRICULTURE
item DE MARTINO, MARY - UNIVERSITY OF IOWA

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2007
Publication Date: 3/11/2008
Citation: Wesley, I.V., Larsen, S., Hurd, H.S., Mckean, J.D., Griffith, R., Rivera, F., Nannapaneni, R., Cox, M., Johnson, M., Wagner, D., De Martino, M. 2008. Low prevalence of Listeria monocytogenes in cull sows and pork. Journal of Food Protection. 71(3):545-549.

Interpretive Summary: The goal of this study was to determine the prevalence of Listeria monocytogenes in cull sows slaughtered at a single plant on two occasions (Trial 1, n=179 cull sows and Trial 2, n= 160 cull sows). Meat from culled breeder hogs constitutes 5% of pork products and is used to make pepperoni as well as other specialty sausages. When results from both trials were combined, overall eight isolates of L. monocytogenes were recovered from five samples that represented 0.18% of the total samples (n=2,775). Seven isolates were characterized further. Isolates were of either serotype 1a, factor 1 (chopped meat samples) or 4b, factor 6 (tonsils, hog carcass swabs), which is the serotype frequently associated with human food-borne outbreaks and were highly virulent (>90%) in the hybridoma cytotoxicity assay. By PFGE, three isolates from the meat blocks were identical but clearly unrelated to those obtained from either the carcass swab or tonsils collected from the same group. These data indicate the low prevalence of L. monocytogenes in the cull sow whose pork poses minimal risk of contaminating the food chain.

Technical Abstract: The goal of this study was to determine the prevalence of Listeria monocytogenes in cull sows slaughtered at a single plant on two occasions (Trial 1, n=179 cull sows and Trial 2, n= 160 cull sows). Fecal samples collected antemortem (Trial 1) as well as animal tissues, and carcass swabs collected at the abattoir (Trial 1 and 2) were analyzed. When results from both trials were combined, overall eight isolates of L. monocytogenes were recovered from five samples that represented 0.18% of the total samples (n=2,775). In Trial 1, L. monocytogenes was detected in a tonsil sample (0.6%, 1 positive of 181 tonsils), in a carcass (0.6%, 1 positive of 179 carcasses), which was sampled prior to the organic rinse, and in two meat block samples (1.2%, 2 positive of 165 samples). In Trial 2, L. monocytogenes was only detected in a single chopped meat sample (0.15%, 1 positive of 688 total samples). Overall, for the two trials L. monocytogenes was recovered in three meat block samples (1.2%, 3 positive of 213 samples). Seven of the eight isolates, all from Trial 1, were available for serotyping, antimicrobial resistance testing, virulence analysis, and genotyping by pulsed-field gel electrophoresis (PFGE). Isolates were of either serotype 1a, factor 1 (chopped meat samples) or 4b, factor 6 (tonsils, hog carcass swabs), which is the serotype associated with human food-borne outbreaks. L. monocytogenes isolates (n=7) were highly virulent (>90%) in the hybridoma cytotoxicity assay. The seven isolates of L. monocytogenes were tested against 20 antimicrobials. All isolates were resistant to tiamulin but sensitive to apramycin, erythromycin, gentamicin, neomycin, spectinomycin, sulfachloropyridazine, sulfadimethoxine, sulphathiazole, and, trimethoprim/sulphamethoxazole. By PFGE, three isolates from the meat blocks were identical but clearly unrelated to those obtained from either the carcass swab or tonsils collected from the same group. These data indicate the low prevalence of L. monocytogenes in the cull sow.