The sexually transmitted bacteria, Mycoplasma genitalium, has for the first time been linked with an increased risk of HIV DNA shedding in women. But the mechanism of the link appears to be different to that seen with sexually transmitted infections (STIs) such as chlamydia. The study is published in the March 1st edition of the Journal of Infectious Diseases.
STIs are known to increase the likelihood of HIV shedding in genital secretions; this phenomenon is thought to be due to the presence of inflammation which recruits various white blood cells to the infected area. Within the past decade, M. genitalium has been linked with genital inflammation such as cervicitis. Lisa Manhart (University of Washington, Seattle, USA) and US and Kenyan colleagues conducted a study of women attending an STI clinic in Mombasa, Kenya to determine factors associated with shedding of HIV-1 DNA from the cervix.
Women had a pelvic examination, all of which were done by one investigator, and a blood test for HIV testing and CD4 cell counts. Samples of cervical secretions were examined for colour, analysed for the frequency of polymorphonuclear leukocytes (PMLs), tested with standard tests for gonorrhoea and chlamydia, and for HIV’s and M. genitalium’s genetic material.
Results from 303 HIV-1-positive women were examined for any relationship between cervical HIV shedding and both the presence or otherwise of M. genitalium and also the amount of M. genitalium DNA.
HIV shedding was detected in 154 women (51%), while M. genitalium was detected in 52 (17%). There was no significant difference in HIV shedding between women with M. genitalium infection compared with those who had negative tests (19% vs 15%.).
In multivariate analysis, women with higher than median M. genitalium organism burdens were younger, reported more sex partners but also more recent condom use, and had a shorter interval between last intercourse and testing than others.
This group was three-fold more likely to shed HIV-1 DNA than were M. genitalium–negative women (adjusted odds ratio 2.9 [95% CI 1.1–7.6]), “yet this did not appear to be mediated by traditional measures of cervical inflammation (elevated polymorphonuclear leukocyte count),” write the investigators
The authors speculate that higher genital burdens of M. genitalium could represent recently acquired infections or alternatively, longer durations of infections. Other studies have shown that the organism can persist for over two years.
Although M.genitalium burden was not linked with elevated PMLs, it was linked with an increased likelihood of abnormal cervical secretions, usually a white or cloudy discharge. This suggests a more chronic inflammatory response to the bacteria than to gonorrhoea or chlamydia.
However, the level of immunosuppression in women was not linked with M. genitalium burden.
“Prospective natural history studies monitoring organism burden over time are required to confirm a causal relationship between M. genitalium infection and HIV-1 shedding. The nature and type of inflammatory cells induced during M. genitalium infection also requires further investigation,” the authors conclude. In the future, screening for and treatment of M.genitalium may become warranted in high-risk HIV-positive women.
Manhart LE et al. High Mycoplasma gentilium organism burden is associated with shedding of HIV-1-DNA from the cervix. J Infect Dis 197: 733 – 736, 2008.