The Role of Lactobacilli in Vaginal Health
Hillier, Sharon L., University of Pittsburgh/Magee-Womens Hospital, Pittsburgh, PA,USA
The role of lactobacilli in the maintenance of vaginal health was first recognized by
Doderlein in the late 1800’s. One of the first strategies used to treat gonorrhea incommercial sex workers was the application of exogenous Lactobacillus obtained fromhealth women.
Thus, the concept of providing exogenous Lactobacillus formaintenance of an optimal vaginal microflora is over a century old.
Pregnant women with a Lactobacillus-predominant flora have a decreased incidence ofpreterm delivery, chorioamnionitis, and postpartum infections. In addition women
without a Lactobacillus-predominant vaginal flora appear to be at increased
susceptibility for sexually transmitted infections including gonorrhea, chlamydia, herpes
simplex virus 2 and human immunodeficiency virus. As treatment of bacterial vaginosis
does not inevitably lead to re-establishment of a Lactobacillus-predominant flora, use ofexogenous strains of lactobacilli have been suggested by several different researchgroups for enhancing the normal microbial defense of the vagina.
The attributes of an optimal strain for use in colonization of the vagina is unknown, butseveral properties have been proposed as being important in establishing a colonization
with an exogenously supplied strain of Lactobacillus. These properties include ability tobind to vaginal epithelial cells, production of lactic acid, production of H2O2, andresistance to phage lysis. Recent studies published from Italy, the United States, Japanand other countries have established that Lactobacillus crispatus and Lactobacillus
jensenii are two of the most commonly recovered vaginal species in women with a
Lactobacillus-predominant flora. These species are nearly universal in their ability toproduce peroxide and their ability to bind to vaginal epithelial cells. Unfortunately, mostof the over-the-counter products containing Lactobacillus in the United States do notcontain these types of lactobacilli.
Studies utilizing Lactobacillus-containing products such as yogurt have largely been
unsuccessful in demonstrating successful colonization with the exogenous strain andinfluencing clinical outcomes related to bacterial vaginosis. Studies funded by the US
National Institutes of Health have lead to the development of a Lactobacillus crispatus
vaginal capsule which has been evaluated for use in combination with oral
metronidazole for treatment of bacterial vaginosis and to re-establish a Lactobacilluspredominant flora. A safety study of Lactobacillus crispatus capsule was performed in
90 women aged 14-21 in Pittsburgh, Pennsylvania and showed that use of the capsules
by women without bacterial vaginosis was safe and led to colonization by theexogenous strain in approximately 65% of the women. A second study was conductedin Pittsburgh and Seattle, Washington among 424 women with both clinical signs andGram stain evidence of bacterial vaginosis. All women were provided with a single 2gram dose of oral metronidazole, and capsules containing 108 colony forming units of
Lactobacillus crispatus were instilled intravaginally twice daily for 3 days. Women werere-evaluated at one month, two months and three months following enrollment. At eachmonthly visit, women were provided with additional vaginal capsules for use andbacterial vaginosis was re-treated with oral metronidazole if women were found to bepersistently infected. In this study, most (90%) of the women had bacterial vaginosis in
the previous year. Thus, the population represented predominately women withrecurrent bacterial vaginosis. This study demonstrated that 88% of the women who
reported using the intravaginal capsules containing Lactobacillus were colonized by theexogenous strain of Lactobacillus sometime during the three month period of follow-up.
The identity of the exogenous strain of Lactobacillus crispatus was verified using a Rep
PCR fingerprinting method which could distinguish endogenous Lactobacillus fromthose present in the capsule. These data suggest that women with recurrent bacterial
vaginosis can be recolonized by exogenous strains of lactobacilli. Among women whowere successfully colonized by the Lactobacillus crispatus strain, there was a significant
improvement in clinical resolution of bacterial vaginosis compared to women given theplacebo capsules. However, women who were given exogenous capsules whichcontained Lactobacillus but who were not colonized by this strain had increased rate of
BV treatment failure compared to the placebo-treated women.
These studies
demonstrate that it is feasible to establish vaginal colonization with an exogenous strainof Lactobacillus crispatus and that women who become colonized have better clinicaloutcomes than women who are not colonized by this strain. In summary, use ofexogenous lactobacilli for normalization of the flora is a concept which is widely
accepted as being of great potential benefit. Preliminary studies using Lactobacillus
provided exogenously in capsule form are promising, and future studies will be needed
to verify whether use of exogenously provided Lactobacillus crispatus can effectively
decrease the risk of recurrent bacterial vaginosis and enhance resistance to sexuallytransmitted infections.