Many women believe that taking lactobacillus probiotics in oral and/or vaginal suppository form can prevent vaginal candidiasis after a course of antibiotics. A recently published study in the British Medical Journal suggests this may be somewhat misguided.
There is a clear rationale for the use of lactobacilli, particularly intravaginally, for prevention of post-antibiotic bacterial vaginitis: this condition is strongly associated with increased vaginal pH, which can be reversed by the hydrogen peroxide produced by lactobacilli. These probiotic organisms also play a role in preventing pathogenic bacterial adherence.
In acute vulvovaginal candidiasis, a fungal infection, vaginal pH typically remains normal, and in many women with this condition lactobacilli remain the dominant vaginal bacterial flora despite the widespread presence of candida. Therefore, it is unclear how supplemental lactobacilli would confer any benefit.
The exact mechanism by which antibiotics increase the risk of developing symptomatic candidiasis is unknown, although it is likely that the drugs do kill off friendly vaginal flora and disrupt the microbial ecosystem.
Science on the subject of probiotics and vaginal candidiasis has been limited thus far, which is why the recent Australian study was worthy of considerable attention.
The Australian investigators studied 278 women with non-gynecologic infectious conditions requiring antibiotic therapy. The women were randomized to receive one of four different probiotic regimens during six days of antibiotic use, and for four days after. One group took half a teaspoon of an oral lactobacillus powder twice daily and a lactobacillus vaginal suppository once daily; the second group took oral lactobacillus and vaginal placebo; the third took vaginal lactobacillus and oral placebo; the fourth group received a double placebo.
The oral product contained Lactobacillus rhamnosus and Bifidobacterium longum. The vaginal pessary contained L. rhamnosus, L. delbrueckii, L. acidophilus, and Streptococcus thermophilus. All of these strains are well-recognized as probiotic organisms. Surprisingly, the authors did not report the amount of lactobacillus, that is, the colony-forming units, in these products. This omission is probably the greatest limitation in terms of evaluating the outcomes of this trial.
To assess the incidence of post-antibiotic candida, the women were asked to report any symptoms in a survey and to provide vaginal swab specimens at baseline and either four days after completing their treatment or when symptoms developed. A “case” was defined as development of symptoms and positive isolation of candida from a swab specimen.
Of the 235 women who had complete data, 55 developed symptomatic candidal vulvovaginitis, including 24% of those on oral and vaginal lactobacillus, 24% of those oral lactobacillus and vaginal placebo, 29% of those on vaginal lactobacillus and oral placebo, and 17% of those on double placebo. The odds ratios for developing candida vaginitis were 1.06 for oral lactobacillus and 1.38 for vaginal lactobacillus, however, these differences were not statistically signficant. The data suggest that the probiotic treatments had little benefit, and if anything, were associated with increased likelihood of a candidal infection (Pirotta M, et al. BMJ 2004; Sep 4; 329: 548–551).
These data run counter to a widely held belief, and they raise significant questions. Personally, I’ve always found it something of a quandary to explain how lactobacilli, especially when delivered orally, could be effective for yeast vaginitis. Women who use probiotics in this way may not understand the difference between bacterial and fungal vaginitis. From a therapeutic viewpoint, this distinction is quite important.
It is important, however, to recognize the limitations of the Pirotta study. The data pertain to one formulation and dose of lactobacillus, and the investigators did not record the lactobacillus counts, a major omission in my mind, and one that leaves me questioning the results. This study is also problematic in that it may not have used the most vaginally effective species of lactobacillus. I do not think it is appropriate to generalize to other probiotics used to prevent antibiotic induced candida.
The jury is still out on this matter, and the current study reminds us of the complex role of local and systemic immunity in vaginal ecology. For now, I will continue to attempt to enhance systemic and vaginal immunity to prevent candida vulvovaginitis when using antibiotics. However, I will use products that deliver approximately 8 billion organisms per day orally.
