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RADAR: ‘Tremendous amount’ of M. genitalium detected rectally with off-label testing
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SAN FRANCISCO — Researchers detected a “tremendous amount” of Mycoplasma genitalium from rectal swab specimens through off-label transcription mediated amplification, or TMA, testing in a cohort of young transgender women and men who have sex with men, or MSM, according to findings from the RADAR study presented at ASM Microbe.
Molecular testing has expanded the ability of laboratories to identify certain pathogens associated with STIs, such as M. genitalium, said Erik Munson, PhD, an assistant professor of clinical laboratory science at Marquette University College of Health Sciences.
“In the past, we had to rely on serological methods that can be cross reactive with other species of Mycoplasma, such as Mycoplasma pneumoniae and Mycoplasma hominis. In addition, another testing modality would have been culture, and culture is rather insensitive, and it takes about 2 to 3 weeks, if not more, to identify a positive finding,” Munson told Infectious Disease News. “The advent of a molecular test really gives us a lot of power to look for organisms like Mycoplasma genitalium that can be associated with sexually transmitted infection.”
In RADAR, Munson and colleagues are attempting to assess “multilevel influences” on HIV risk and substance use among young transgender women and MSM.
The study cohort includes individuals assigned male at birth, aged 16 to 29 years, who have had a sexual encounter with a man within the past year, or identify as gay, bisexual or transgender. According to the abstract, the 1,365 study participants had to submit first void urine and rectal swabs within a 10-month period. The samples were tested for Chlamydia trachomatis and Neisseria gonorrhoeae by commercial TMA-based assays, and for T. vaginalis and M. genitalium using off-label TMA-based testing.
According to Munson and colleagues, 203 participants tested positive for C. trachomatis and N. gonorrhoeae. Specifically, C. trachomatis was detected in 104 participants, N. gonorrhoeae in 70, and 29 participants were infected with both. The detection rates of both C. trachomatis and N. gonorrhoeae in urine specimens ranged from 0.7% to 1.5%, whereas detection rates in rectal specimens raged from 7.1% to 8.8%.
The off-label TMA-based assay detected an additional 295 participants with an STI. Specifically, the researchers reported that T. vaginalis was detected in 11 participants and M. genitalium in the other 284. Of these infections, 82.4% were detected through the testing of rectal specimens. T. vaginalis was detected in 0.2% of urine samples and 1.2% of rectal samples, whereas M. genitalium was detected in 9.3% of urine specimens and 22.3% of rectal specimens.
Rectal detection of M. genitalium was higher among black participants compared with non-black participants, 29.6% vs. 17%. M. genitalium detected via rectal specimens occurred in 41.4% of HIV-positive participants, compared with 15.8% of HIV-negative participants.
The researchers suggested the need for further studies that explore the significance of rectal detection of T. vaginalis and M. genitalium and the correlation with HIV infection.
“With respect to the current study, we found a tremendous amount of Mycoplasma genitalium detection from rectal swab specimens,” Munson said. “When you’re talking about high-risk sexual practices, that may be a specimen source to entertain, as far as yielding a more comprehensive screen for those at-risk demographics.” – by Marley Ghizzone
Reference:
Munson E, et al. Outstanding abstract award: Molecular screening for Trichomonas vaginalis and Mycoplasma genitalium in the RADAR longitudinal cohort study of young transgender women and young men who have sex with men. Presented at: ASM Microbe; June 20-24, 2019; San Francisco.
Disclosures: The authors report no relevant financial disclosures.
Perspective
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Gitanjali Pai, MD, AAHIVS
With more than 2 million STIs diagnosed in the United States in 2017, and the growing national burden of STIs, comprehensive screening is the first step toward detection and cure — an important stride in halting transmission of STIs, especially among vulnerable populations such as young transgender women and MSM. New CDC analysis is suggestive of an increased risk for extragenital STIs among gay, bisexual and other MSM. MSM are disproportionately affected by STIs and HIV.
This study by Munson and colleagues highlights the importance of comprehensive STI screening, especially extra-urogenital sites. Molecular methods provide broad diagnostic coverage and can be helpful for early detection, especially in asymptomatic cases and extra-urogenital sites, which can serve as a reservoir of infection and could contribute to resistance. Identification of STIs and their associated risk behaviors is vital for targeted risk reduction, screening and treatment for STI control. With STIs continuing to surge, clinicians should be aware of and be committed to the diverse STI transmission prevention and treatment needs, and take action accordingly.
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