Which Comes First: Infection or Bacteria?

A recent discovery suggests that Trichomonas vaginalis may alter the vaginal microbiota in a manner that cultivates bacteria that is beneficial to its survival and transmissibility.¹ These findings were reported by researchers led by David H. Martin, MD, professor and chief of infectious diseases at Louisiana State University’s Health Sciences Center New Orleans. The researchers also reported the discovery of a previously unknown species of mycoplasma, which they have named “Mnola” (a mycoplasma discovered in New Orleans, La).^1,2
   
The parasite T vaginalis is the cause of trichomoniasis, the most common curable sexually transmitted infection. More than 3.7 million US men and women are estimated to have the infection, but only about 30% of experience symptoms.³ In women, the symptoms include itching, burning, sore genitals, discomfort upon urination, and vaginal discharge. Trichomoniasis is also associated with a higher rate of premature deliveries and a greater susceptibility to infection with HIV.
   
The researchers based their study on the hypothesis that vaginal microbiota in T vaginalis-infected women differs from that in women without T vaginalis infection.¹ Vaginal samples from 30 infected women were matched by Nugent score to those from 30 uninfected women. The results showed that the vaginal microbiota in infected women were different from that in uninfected women among those with normal or intermediate Nugent scores. In infected and uninfected women with bacterial vaginosis, however, the vaginal microbiota was similar.
   
Additional cluster analysis revealed the presence of 2 distinct groups of women with T vaginalis infection. One group had high counts of Mycoplasma hominis, and the other group had high counts of an unknown Mycoplasma species (Mnola). The women in the M hominis group had clinical evidence of enhanced vaginal inflammation, indicating that women with trichomoniasis and the presence of M hominas have worse disease than women with other trichomonas infections. The study authors hypothesized that this latter group might be at high risk for HIV infection.
   
Of interest is that T vaginalis seems to be responsible in some way for the appearance of these mycoplasma-dominated bacterial communities. “So instead of these unique communities predisposing women to infection as originally thought, we now believe that trichomonas takes on the role of a farmer in the vaginal environment by cultivating bacterial communities that are in some way beneficial to itself. Proving this hypothesis and figuring out how these bacteria interact with trichomonas will be the subject of future research,” concluded Martin.²

Pertinent Points:
- The common Trichomonas vaginalis “cultivates” bacterial communities that are beneficial to its survival and transmissibility.
- Among women with T vaginalis infection, there are 2 unique groups of mycoplasma communities-one with high abundance of Mycoplasma hominis and the other with high abundance of an unknown Mycoplasma species.
- Women with T vaginalis infection and a high abundance of M hominis seem to have more severe disease than women with other trichomonas-infected women and also seem to to more susceptible to HIV infection.
 

References:

1. Martin DH, Zozaya M, Lillis RA, et al. Unique vaginal microbiota that includes an unknown mycoplasma-like organism is associated with Trichomonas vaginalis infection. J Infect Dis. 2013 Apr 4. [Epub ahead of print]
2. LSUHSC research discoveries shed light on common STI [press release]. Available at: http://www.eurekalert.org/pub_releases/2013-04/lsuh-lrd040213.php. Accessed April 4, 2013.
3. Centers for Disease Control and Prevention. Trichomoniasis – CDC fact sheet. Available at: http://www.cdc.gov/std/trichomonas/stdfact-trichomoniasis.htm. Accessed April 14, 2013.