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Fecal samples collected from 470 slaughtered reindeer 6 to 7 months of age were screened by real-time PCR (after enrichment) for Shiga toxin genes (stx) and then for Escherichia coliserogroup O157. Shiga toxin genes were found frequently (>30% of samples), and serogroup O157 was detected in 20% of the stx-positive samples. From these samples, a total of 25 E. coliO157:H−isolates (nonmotile but PCR positive for fliCH7) were obtained. Twenty-four of these E. coliO157:H−isolates did not ferment sorbitol and originated from one geographic area. These 24 isolates belonged to the multilocus sequence type 11, typical for Shiga toxin–producing E. coli(STEC) O157:H7 and O157:H−, and harbored genes stx1a, stx2c, eae,and hlyA; the stx2csubtype has been associated with high virulence. In contrast, one E. coliO157:H−isolate (multilocus sequence type 11) did ferment sorbitol, lacked Shiga toxin genes, but was positive for eae, hlyA,and sfpA. This isolate closely resembled an STEC that has lost its Shiga toxin genes. Additional examination revealed that reindeer can be colonized by various other STEC isolates; 21 non-O157 STEC isolates belonged to four multilocus sequence types, harbored stx1a(8 isolates) or stx2b(13 isolates), and in the stx2b-positive isolates the recently described new allelic variants (subAB2-2and subAB2-3) for subtilase cytotoxin were identified. Hence, slaughtered semidomesticated Finnish reindeer might constitute a little known reservoir for STEC O157:H7/H−and other serogroups, and the risk of direct or indirect transmission of these pathogens from reindeer to humans and domestic livestock must not be overlooked.

A combined culture and PCR method for detection of pathogenic Yersinia enterocoliticain food (NMKL-163A) was evaluated by testing samples of artificially and naturally contaminated pork. The performance of the pre-PCR sample treatment, buoyant density centrifugation, was first compared with two commercially available methods (DNeasy tissue kit and PrepMan). We found that similar sensitivity was reached (i.e., 25 CFU/g of food was detected by single PCR) with the buoyant density centrifugation and the DNeasy Tissue kit when tested on overnight enrichments. However, the DNeasy tissue kit was superior when tested on nonenriched homogenates; the detection limit was 25 CFU/g in minced beef by single PCR and 25 CFU/g in sausage by nested PCR. We then analyzed 100 raw minced pork samples. Thirty-five tested positive for presumptive pathogenic Y. enterocoliticawhen analyzed by the NMKL-163A method, whereas none tested positive when analyzed in parallel by a standard culture method (ISO 10273). We also analyzed 97 samples of cold-smoked pork sausage, of which approximately 11% tested positive by the NMKL-163A method. This study showed that sensitivities such as those obtained by nested PCR were required for detection of the pathogen in naturally contaminated samples, and therefore the nested PCR primers, which are included in the NMKL-163A method only as an option, need to be validated and applied routinely.

A total of 425 pig tonsils, including 210 tonsils from fattening pigs and 215 from sows, from seven different abattoirs in Finland were studied for the occurrence of Yersinia pseudotuberculosisfrom 1999 to 2000. The mean prevalence of Y. pseudotuberculosisin fattening pig tonsils was 4%, varying from 0 to 10% between slaughterhouses. Y. pseudotuberculosiswas not recovered from sow tonsils. All 30 Y. pseudotuberculosisisolates from eight pig tonsils were recovered after cold enrichment. Seventeen isolates from seven tonsils were found after cold enrichment for 14 days, followed by alkali treatment. Y. pseudotuberculosiswas not isolated after direct plating, overnight enrichment, or selective enrichment. All 30 isolates belonged to bioserotype 2/O:3 and carried the virFgene in the virulence plasmid. The isolates exhibited calcium dependence and Congo red absorption. The pyrazinamidase test gave variable results. All isolates were characterized with pulsed-field gel electrophoresis (PFGE). Using SpeI, NotI, and XbaI enzymes, seven, five, and two different PFGE patterns were obtained, respectively. A total of 11 genotypes, gI to gXI, identified by a combination of the various SpeI, NotI, and XbaI profiles, were detected. Three pigs were found to carry more than one genotype. Overall, variations between PFGE patterns were small, indicating genetic homogeneity among pig strains of bioserotype 2/O:3.