Is Mycoplasma hominis a vaginal pathogen?

OBJECTIVE To evaluate the role of Mycoplasma hominis as a vaginal pathogen. DESIGN Prospective study comprising detailed history, clinical examination, sexually transmitted infection (STI) and bacterial vaginosis screen, vaginal swabs for mycoplasmas and other organisms, follow up of bacterial vaginosis patients, and analysis of results using SPSS package. SETTING Genitourinary medicine clinic, Royal Liverpool University Hospital. PARTICIPANTS 1200 consecutive unselected new patients who had not received an antimicrobial in the preceding 3 weeks, and seen by the principal author, between June 1987 and May 1995. MAIN OUTCOME MEASURES Relation of M. hominis isolation rate and colony count to: (a) vaginal symptoms and with the number of polymorphonuclear leucocytes (PMN) per high power field in the Gram stained vaginal smear in patients with a single condition--that is, candidiasis, bacterial vaginosis, genital warts, chlamydial infection, or trichomoniasis, as well as in patients with no genital infection; (b) epidemiological characteristics of bacterial vaginosis. RESULTS 1568 diagnoses were made (the numbers with single condition are in parenthesis). These included 291 (154) cases of candidiasis, 208 (123) cases of bacterial vaginosis, 240 (93) with genital warts, 140 (42) chlamydial infections, 54 (29) cases of trichomoniasis, and 249 women with no condition requiring treatment. M. hominis was found in the vagina in 341 women, but its isolation rates and colony counts among those with symptoms were not significantly different from those without symptoms in the single condition categories. There was no association between M. hominis and the number of PMN in Gram stained vaginal smears whether M. hominis was present alone or in combination with another single condition. M. hominis had no impact on epidemiological characteristics of bacterial vaginosis. CONCLUSION This study shows no evidence that M. hominis is a vaginal pathogen in adults.