Development of a real-time PCR targeting the yidC gene for the detection of Mycoplasma hominis and comparison with quantitative culture. 
Mycoplasma hominis is an opportunistic human mycoplasma species that can be either commensal or pathogenic.  Its detection by culture is considered to comprise the reference technique.  Previously reported PCR techniques target the 16S rRNA or the gap gene, although sequence variations among clinical isolates may lead to variations in clinical sensitivity.  The present study aimed to develop a specific TaqMan quantitative real-time PCR assay, targeting a gene conserved in all M. hominis isolates, and to compare it with quantitative culture.  With the knowledge of the M. hominis PG21 genome sequence, the yidC gene, encoding a membrane protein translocase, was chosen as target.  Its intraspecies heterogeneity was checked at the nucleotide level using 31 reference or clinical strains.  The limit of detection, the analytical specificity and the reproducibility of the assay were assessed.  Moreover, PCR and culture results were compared using 153 urogenital specimens.  The limit of detection was seven copies/μL. The analytical specificity was 100%, with good inter- and intra-assay reproducibility.  Among the 153 urogenital specimens, the yidC PCR and culture allowed detection of 55 and 45 M. hominis-positive samples, respectively.  Comparison of the bacterial load among the 45 specimens found to be M. hominis-positive by both techniques revealed a statistically significant association between the quantitative results obtained.  In conclusion, we developed a specific, sensitive and reproducible real-time PCR to detect all M. hominis clinical isolates.  This PCR was shown to have higher sensitivity than culture, although both methods were correlated for quantification of M. hominis loads in urogenital specimens.