the present study, we compared sensitivities between the PCR methods for recN and the 16S rRNA gene, and different results could be obtained using a few S. suis reference strains. S. suis generally possesses 4 copies of the 16S rRNA gene and 1 copy of the recN gene; therefore, the sensitivity of 16S rRNA gene PCR is expected to be higher than that of recN PCR. However, some of the S. suis reference strains examined in this study possessed point mutations in the primer regions of 16S rRNA gene PCR (data not shown), such that the sensitivity of this PCR was low to these strains. On the other hand, the detection limits of recN PCR were similar among the reference strains of authentic S. suis (approximately 1,000 copies/PCR reaction tube), which indicates that recN PCR always provides stable results.