The primers and probes for Up were designed according to DNA topoisomerase Ⅳ gene sequences of 4 Up serovars to detect Up in vaginal secretion samples. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene was analyzed by PCR quantitative assay to determine host cells. The Up relative quantification was calculated as Up copies in 10³ host cells. Up standard isolate and clinical isolates, Ureaplasma urealyticum standard isolate and clinical isolates and 11 common vaginal microorganisms were determined to identify the specificity of the assay. The vaginal secretion samples were collected from 532 BV patients and 276 healthy women for the analysis of Up relative quantification.

Up PCR quantitative assay had high sensitivity (100 copies/μL), without amplification to Ureaplasma urealyticum and 11 other vaginal microorganisms. The infection rates of Up in BV patients and healthy women were 49.8% (265/532) and 43.1% (119/267), respectively, without statistical significance (χ²=3.263, P=0.071). Up relative quantification in BV patients was 667 copies/10³ cells, which was significantly higher than that in healthy women (20 copies/10³ cells) (χ²=47.012,P=0.000 1). When using >50 copies/10³ cells as a reference, the positive rate of Up in BV patients was 39.3% (209/532). It was significantly higher than that in healthy women (17.0%, 47/276) (χ²=41.537,P=0.001).

The cell adhesion ability of Up is a key factor in the pathogenesis. Up PCR relative quantitative assay can overcome the influence of different vaginal sampling ways on the determination results and objectively reflect the pathogenicity of Up.