75% topical metronidazole gel applied once daily for five days and found at 30 days posttreatment that a single species, L. iners, was predominant in all patients, except for the one patient for whom treatment failed both according to Nugent and Amsel criteria [23]. Hence, it has been suggested that following the resolution of bacterial vaginosis, L. iners is the only Lactobacillus species that succeeds to replenish the vagina in appreciable amounts, buy MCC950 which in turn may render these patients more vulnerable to a new episode of bacterial vaginosis, considering the rather moderate colonisation resistance offered by L. iners [22]. Jakobsson and Forsum corroborated the finding

by Ferris et al and further suggested that L. iners may become a dominant part of the vaginal microflora when the microflora is in a transitional stage between abnormal and normal [24]. As our study was confined to genotypic characterisation of the microflora, it remains to be determined which phenotypic attributes of the different Lactobacillus species explain the observed associations. Previous studies have pointed at an important role for hydrogen peroxide production in colonization HDAC inhibitors in clinical trials resistance [25–27]. In a 2-year follow-up study, Hawes et al documented that the acquisition of bacterial vaginosis was strongly associated

with a lack or loss of hydrogen peroxide producing lactobacilli [28]. At first sight, our findings corroborate this paradigm, as most L. crispatus strains have been found to be very consistently strong H2O2 producers [29, 30], whereas most L. iners strains have been found to be for the most part non-H2O2 producers [29, 30]. However, other factors must be involved as well. In particular, most L. jensenii strains have been found to be equally

strong H2O2 producers as L. crispatus [29, 30], although in this study L. jensenii showed a stronger association with conversion to abnormal VMF. A possible explanation is that L. jensenii is the only Lactobacillus species for which PD184352 (CI-1040) poorer colonisation resistance seemed to be correlated with poorer colonisation strength, i.e. conversion to abnormal VMF was more likely to be associated with the disappearance of L. jensenii. Compared to the other Lactobacillus species, L. jensenii is also on average present in a significantly lower concentration with grade I VMF [21]. Our results must be taken with extreme caution as our study had several important limitations. Firstly, our sample size was rather small and therefore our results need to be corroborated in larger cohorts. Secondly, we acknowledge that the PARP assay interval between subsequent sampling occasions was rather large with an average of some 3 months interval time. Thirdly, it must be acknowledged that a single sampling occasion may not properly reflect the vaginal microflora status of a woman due to swift changes in the microflora as has been documented previously [31, 32].