The prevalence of M. genitalium infection was significantly higher in women presenting with vaginitis caused by BV, similar results to those reported by Oakeshott and colleagues who were the first to report an association between M. genitalium and asymptomatic BV [11]. We identified an OR of M. genitalium in BV-positive vs BV-negative women of 1.97, a value of 2.73 was reported for this parameter in the Oakeshott et al. study [11]. We also demonstrated that this association is related to dysbiosis and not clinical manifestations of BV since positive Nugent Gram-stain scores alone were independently associated with M. genitalium prevalence (Table 1). Since the present study was conducted retrospectively it was not possible to determine the impact of BV on incidence of M. genitalium infection. A recently published prospective study, however, found no evidence that therapeutic intervention in women with asymptomatic BV impacted M. genitalium incidence during a 12-month follow-up period [15]. Whether this finding reflects a true lack of causality between vaginal dysbiosis and M. genitalium acquisition or is indicative of failure of therapeutic intervention to eliminate BV could not be determined [15]. It is conceivable that the presence of a vaginal microbiome consistent with BV merely serves as a non-specific marker for selecting populations at higher risk of infection with other STI including M. genitalium or, somewhat less likely, that persistence of a dysbiotic microbiome is more likely if patients are co-infected with M. genitalium. Additional studies will hopefully resolve these questions.

In the study of Sena et al. [15], black race, age < 21 years, and prior-pregnancy were identified as being significantly associated with prevalent M. genitalium infection in women with BV. Only limited demographic data was collected on subjects in the present study but we were able to assess associations between race, age and prevalence of M. genitalium infection. Similar associations between African-American race (OR = 2.33) and age (< 25 years old vs 25 years old or older; OR = 2.40) were identified in our study population as seen in that of Sena et al. [15]. The potentially confounding influence of race and age on the observed association between BV and M. genitalium prevalence was assessed using logistic regression analysis. Under multivariate analysis, however, BV remained significantly associated with prevalent M. genitalium infection as did African-American race and age < 25 years (Table 2). The lack of an association between clinical manifestations of BV, as assessed by Amsel scores, and M. genitalium prevalence (Table 1) was not unexpected since positive associations between BV and M. genitalium have previously been demonstrated in entirely asymptomatic populations [11, 15]. Limitations notwithstanding, the findings presented here and in the study of Sena et al. [15] suggest that the presence of BV represents a significant risk factor for acquisition of M. genitalium and logically, therefore, that women with untreated BV are at elevated risk of developing symptomatic M. genitalium infections and, or, transmitting this organism to their sexual partners. Given that testing for M. genitalium in asymptomatic populations is not currently recommended, improved diagnosis and management of BV may be a useful approach to mitigating these risks.

Importantly, by using a novel M. genitalium NAAT assay we were able to determine not merely the prevalence of M. genitalium in the study population but also the frequency with which MRMM were present in M. genitalium positive samples. MRMMs were identified in a significant minority (37.1%) of M. genitalium infections, a result somewhat higher than the 30.8% reported previously in a cohort of females with asymptomatic M. genitalium infection in the US [22]. Although azithromycin remains recommended first-line therapy for M. genitalium in the US [7], that recommendation pre-dates much of our understanding of the prevalence of macrolide-resistance in this organism and is likely to change in the relatively near future. For efforts at curtailing resistance to be successful, however, clearly consideration must be given to the importance of potential reservoirs of resistant organisms such as the vaginal milieu of asymptomatic women with dysbiotic microbiota.