August 15, 2005
Rectal bacteria may lower vaginal infection risk
NEW YORK (Reuters Health) - The presence of a specific type
of bacteria in the rectum appears to reduce the risk of vaginal
infections, researchers report.
"The gut has been seen as a site which harbors pathogens,
which can cause vaginal infection, principal investigator Dr.
Sharon L. Hillier of the University of Pittsburgh commented.
These findings are the "first to document that the lower
gastrointestinal tract can also harbor the lactobacilli, which
are beneficial for vaginal health."
"Further," she told Reuters Health, "when women harbor
these organisms in the gut, they have a reservoir for
replenishing vaginal lactobacilli should they decrease
following sexual exposure or douching."
As they report in The Journal of Infectious Diseases,
Hillier and her colleagues studied vaginal and rectal swabs
obtained from 531 women and recovered lactobacilli from the
vagina of 74 percent and the rectum of 51 percent.
Overall, 80 percent of the women had evidence of
lactobacilli in the vagina, or in the vagina and the rectum.
Most women (67 percent) had lactobacilli that produced hydrogen
The absence of hydrogen peroxide-producing lactobacilli in
the vagina is associated with an increased risk of bacterial
vaginosis, which is associated with higher concentrations of
HIV in women with this infection and higher rates of preterm
birth in pregnant women, the investigators explain.
Conversely, the presence in the vagina of lactobacilli that
produce high levels of hydrogen peroxide is associated with
lower rates of bacterial vaginosis and certain pregnancy
Hillier and her associates speculated that the presence of
rectal lactobacilli may help maintain the healthy balance of
normal vaginal flora and that this, in turn, is associated with
a lower rate of the adverse effects of bacterial vaginosis.
The most common types of rectal hydrogen peroxide-producing
lactobacilli were Lactobacillus crispatus (16 percent), L.
jensenii (10 percent) and L. gasseri (10 percent).
Only 13 (9 percent) of the 147 women with vaginal, or
rectal and vaginal L. crispatus or L. jensenii had bacterial
vaginosis compared with 12 (44 percent) of those with other
hydrogen peroxide-producing lactobacilli.
The lowest prevalence of bacterial vaginosis (5 percent)
was seen in women with vaginal and rectal hydrogen
peroxide-producing lactobacilli. Those who had only vaginal,
only rectal, or no lactobacilli at either site, had an
increased risk of vaginosis.
The researchers add that the dairy-related lactobacilli, L.
acidophilus and L. delbrueckii bulgaricus, were not seen either
rectally or vaginally, and that it is possible that L.
crispatus and L. jensenii "may be better suited to probiotic
SOURCE: The Journal of Infectious Diseases, August 1, 2005.