Microbial and vaginal determinants influencing Mycoplasma hominis and Ureaplasma urealyticum genital colonization in a population of female patients.

Mycoplasma hominis and Ureaplasma urealyticum are associated with chorioamnionitis, preterm delivery and pelvic inflammatory disease. The aim of this study was to evaluate the possible risk factors of co-colonization by M. hominis in patients already colonized by U. urealyticum and compare demographic parameters, vaginal pH and microbiota of women colonized by U. urealyticum or M. hominis. A total of 452 patients positive for U. urealyticum or M. hominis were analysed, 421 (93.1%) of whom were positive for U. urealyticum and 31 (6.9%) for M. hominis. Patients positive for M. hominis compared to patients positive for U. urealyticum were more frequently colonized by Gardnerella vaginalis (71% vs 18.5%; p 0.0001), less frequently by lactobacilli (16.1% vs 61.5%; p 0.0001), and more frequently had a pH value higher than 4.5 (96.8% vs 57%; p 0.0001), all conditions associated to bacterial vaginosis (BV). Logistic regression analysis showed that only G. vaginalis colonization and pH higher than 4.5 were independently related to M. hominis colonization (respectively p 0.0001 and p 0.016). Thus, in women colonized by U. urealyticum, BV is an independent risk factor for M. hominis co-colonization.