High prevalence of yadA-positive Yersinia enterocolitica in pig tongues and minced meat at the retail level in Finland

Polymerase chain reaction (PCR) was used to determine the prevalence of yadA-positive Yersinia enterocolitica in pig tongues and minced meat at the retail level in Finland and to confirm the yadA-positive Y. enterocolitica isolates recovered from the same samples using the conventional culture method. A total of 51 pig tongues purchased at 12 retail outlets and 255 minced meat samples purchased at 40 retail outlets in the Helsinki area were studied. The prevalence of Y. enterocolitica carrying the yadA gene was 92% in pig tongues and 25% in minced meat using PCR and 78% in tongues and 2% in minced meat with the culture method. The prevalence of yadA-positive tongues was higher (98%) when both PCR- and culture-positive results were included because Y. enterocolitica carrying the yadA gene could also be isolated in three PCR-negative tongue samples. In the minced meat samples, all PCR-negative samples were also culture-negative. With the culture method, 66 of 80 yadA-positive isolates in 38 tongues and all yadA positive isolates (4) in four minced meat samples were recovered after selective enrichment. A total of 92 isolates of Y. enterocolitica bioserotype 4/O:3 in tongues and 5 isolates in minced meat were found, of which 13% in tongues and 20% in minced meat did not carry the yadA gene.