A multiplex polymerase chain reaction for discriminating Erysipelothrix rhusiopathiae from Erysipelothrix tonsillarum

Erysipelothrix rhusiopathiae is the causative agent of swine erysipelas, and it causes great economic losses in Japan and worldwide. In meat inspection, it is very important to distinguish E rhusiopathiae from other bacteria showing similar clinical signs of disease or similar bacterial characteristics. To distinguish E rhusiopathiae from Erysipelothrix tonsillarum, 2 polymerase chain reaction (PCR) systems were combined. The primer sets ERY-1F and ERY-2R were designed to amplify 2,210 base pairs (bp) of nucleotide sequence specific for E. rhusiopathiae chromosomal DNA, and the primer sets MO101 and ERS-1R were designed to amplify 719 bp of nucleotide sequence including a highly conserved region of genus Erysipelothrix 16S rRNA. Two fragments were amplified when E. rhusiopathiae was used as the PCR template using the primer sets, whereas a single fragment was amplified when E. tonsillarum was used as the template. No fragments were amplified when nucleic acid from other bacteria that cause clinical signs similar to swine erysipelas were used as the template. Moreover, 5 specimens collected from postinspected swine carcasses were diagnosed as E rhusiopathiae using the PCR described in this study, in agreement with results of microbiological tests for the genus Erysipelothrix, whereas negative samples were negative both in conventional bacterial tests and by PCR. The detection limit of multiplex PCR ranged from 102 to 104 colony forming units per reaction tube for positive samples. These results suggest that this method is useful for screening of swine erysipelas in meat inspection centers.