Literature review > Issue_5 > Review on Taylor-Robinson et al. 

The goal of this study was to detect the distribution of six different mycoplasma species in throat, rectum, and urine samples from 10 men who have sex with men and who had non-gonococcal urethritis (NGU) compared to18 men who have sex with men but were without NGU. Mycoplasma hominis and Ureaplasma urealyticum were detected by culture. Mycoplasma genitalium, Mycoplasma fermentans, Mycoplasma penetrans and Mycoplasma pirum were detected by the polymerase chain reaction (PCR) using urine samples.

M. hominis and U. urealyticum were prevalent in both the patients and the controls (20-30% positive) as might be expected. In contrast, only a few samples were positive for the four mycoplasmas (5-10% positive) detected by PCR. Because of the small sample size (10 cases and 18 controls) and the low frequency of detection of M. genitalium, M. fermentans, M. pirum and M. penetrans, one cannot determine the significance of the presence or absence of a positive result when only 1 positive is detected in either the10 test persons or 18 controls.

A general problem with PCR assays has been false positives because of contamination with trace amounts of DNA present in the laboratory. This problem has been addressed by two methods: using PCR assays with two different targets [1] or sequencing the PCR product taking advantage of sequence variation resulting from the high mutation rate of mycoplasmas [2,3]. Either of these methods gives greater confidence that the PCR result is true. Even considering this objection, the principal finding of the study was that genital mycoplasmas are found in the rectum. The finding that M. pirum can be detected in the rectum is important because it indicates that this organism could be of human origin. Further testing of rectal mucosal specimens needs to be done to determine whether these results accurately portray the actual colonization site of M. pirum, M. penetrans and possibly M. genitalium in both heterosexual and homosexual males.

References:

1. Jensen, JS, Borre, MB, and Dolin, B. Detection of Mycoplasma genitalium by PCR amplification of the 16S rRNA gene. J. Clin. Microbiol. 2003:41:262-269.

2. Jensen, JS, Bjornelius, E, Dohn, B, Lidbrink, P. Use of taqMan5' nuclease real-time PCR for quantitative detection of Mycoplasma genitalium DNA in males with and without urethritis who were attendees at a sexually transmitted disease clinic. J. Clin. Microbiol. 2004;42:683-692.

3. Ma L, Martin, DH. Single-nucleotide polymorphisms in the rRNA operon and variable numbers of tandem repeats in the liporotein gene among Mycoplasma genitalium strains from clinical specimens. J. Clin. Microbiol. 2004;424:876-4878.

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