Does loss of vaginal flora increase risk of STD?
Risk factors include unsafe sex, douching
Several new studies looking at the association between the loss of natural vaginal flora and the risk of sexually transmitted diseases (STDs) have shown that women who lack lactobacillus are more predisposed to acquiring HIV and other STDs. Why women lose their natural microflora is not entirely clear but it has been linked to bacterial vaginosis, excessive douching, and unsafe sex.
Research on the relationship between STD risks and a woman's vaginal ecology is a new arena that only recently has received serious attention from investigators. The most recent findings on the relationship were presented at the American Society for Microbiology's 98th General Meeting in Atlanta in May.
Sharon Hillier, MD, director of reproductive infectious disease research at Magee-Women's Hospital at the University of Pittsburgh, has been a pioneer in vaginal lactobacilli research, and for a while was a lone voice in the field. But others are taking notice and more studies are emerging with similar data.
"People thought I lost my mind when I first talked about this, but I think it might actually be true," she said at the conference.
Among the natural elements for protecting against pathogens, the vaginal mucosa produce lactobacilli, organisms that help the vagina maintain a low pH, which in results in a vaginal environment that kills germs. Lactobacilli also produce hydrogen peroxide, which also kills pathogens.
Lack of flora linked to HIV in Thailand
Hillier presented an overview of both published and unpublished data showing that women who lacked peroxide-producing lactobacilli were at significantly increased risk of acquiring HIV. A study of 144 sex workers in Thailand, for example, found that after adjusting for STDs, age, and other factors, women with abnormal vaginal flora were twice as likely to be infected with HIV, she said.
A larger study of sex workers in Mombassa, which was completed last year, followed 657 women who averaged two sex partners a week. Unpublished findings show that about one-third of the women had low prevalence of lactobacilli, putting them at 78% greater risk of acquiring gonorrhea. Nearly all the women regularly douched and only about 20% regularly used condoms, Hillier noted.
Hillier also presented data correlating regular douching and the number of new sex partners with the loss of protective lactobacilli. Also, women who have bacterial vaginosis have less lactobacilli, she noted. Last year, Hillier presented data showing that women with bacterial vaginosis were at increased risk of acquiring HIV.
These findings make it clear to Hillier and other reproductive health experts that there is a need to speak out against douching. "I feel strongly that douching has no known medical benefit," she tells AIDS Alert. "But there is a $100 million industry out there selling perfumed water to women and they fall for the advertising."
Research from the University of Missouri in Kansas City, shedding more light on how bacterial vaginosis relates to lactobacillus, also was presented at the conference. Working on a theory that virus infection in vaginal lactobacilli could be associated with the initiation of bacterial vaginosis, Sylvia Pavlova, PhD, research associate at the university, led a study showing that viruses are widely spread in lactobacilli isolated from women in different geographic areas and that the viruses may be transmissible among women.1
After isolating lactobacilli from 209 women of reproductive age (107 from the United States, 102 from Turkey), the researchers found that 23% of the lactobacilli from the United States and 36% from Turkey released viruses. A total of 67 viruses were isolated, showing four different shapes or types.
"After screening isolates from different women from different countries and races, we found out that lysogeny in vaginal lactobacilli is very high - lysogeny meaning that vaginal lactobacilli carry phages [viruses]," she tells AIDS Alert.
Once these free viruses infect the lactobacilli, they integrate into the bacterial chromosome and become dormant for the most part. However, certain inducers can cause them to be spontaneously released at a high rate.
Vaginal viruses appear to be transmissible
Using DNA fingerprinting, researchers also found that vaginal lactobacilli from three unrelated women were infected by identical virus, even though they lived in different parts of Turkey. The finding suggests that the viruses can be transmitted, although the mechanism is not understood, Pavlova says.
"We cannot say how they are transmitted but possibly by the host bacteria, by lactobacilli, or as a free virus or particle," she adds.
The findings are of interest to clinicians because the presence of these viruses may promote the onset of bacterial vaginosis - a common infection whose cause is not well-understood and is often mistaken as largely harmless. Bacterial vaginosis, in turn, shifts the balance of microflora and overgrows lactobacilli, leaving the vagina less defensive against pathogens, she adds.
Like Hillier, Pavlova has found douching as a risk factor of lactobacilli loss. "I think there is the opinion out there that douching actually causes more harm than good," she says. "The solutions are so aggressive, they tend to eliminate everything, including the lactobacilli, and women need to be more educated about not using them."
One of the disturbing aspects of lactobacilli loss is that some women cannot grow it back once it is lost. Putting women on diets with dairy products, particularly yogurt, has helped in some cases. Although there are 35 different lactobacilli products on the market, none of them are the pure strains that exist in the body, Hillier warned.
Reference
1. Pavlova S, Kilic, A, Tao L. Comparative study of vaginal lactobacillus phages isolated from women in the U.S. and Turkey: Distribution, morphology, host range, and genetic homology. Presented at the American Society of Microbiology 98th General Meeting. Abstract # B-124. Atlanta; May 1998.
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