Abstract:
Mycoplasma genitalium is the smallest existing self-replicating prokaryote, lacks
a cell wall and has a genome consisting of only 580 kilo base pairs. It has
characteristic pear/flask-like morphology with a terminal tip organelle used for
attachment. Many researchers, mainly in developed countries, have investigated
the role the organism plays in the aetiology of male urethritis and the majority of
studies show an association between M. genitalium and male urethritis. In this
study, the modified Koch’s postulates were applied to answer the question
whether M. genitalium is a true pathogen, or merely a passenger, invading
already inflamed or damaged cells.
A total of 300 urine specimens were collected from adult males with symptoms
and/or signs of urethritis and 75 from asymptomatic men. In the first study, three
molecular assays; viz, a commercial conventional PCR test, a real-time PCR (q-
PCR) test and a transcription mediated amplification (TMA) assay were
evaluated for the detection of M. genitalium. The comparison between the assays
was based on the extended gold standard concept, where a specimen was
deemed positive when any two nucleic acid amplification tests were positive. In
the second study, the specimens were tested for four common urethral
pathogens (N. gonorrhoeae, C. trachomatis, T. vaginalis and M. genitalium)
using TMA assays. Finally, the bacterial loads for M. genitalium were determined
using the q-PCR assay.
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All three assays tested were highly specific (98-99%) for the detection of M.
genitalium. However, where q-PCR and TMA demonstrated high sensitivities
(96% and 100%), the sensitivity of the conventional PCR assay was low (78%).
One or more pathogens were detected in a total of 129 (43%) men with urethritis.
M. genitalium was the most frequently detected pathogen in men with urethritis
(129; 43%), and significantly more (p= 0.04) than in asymptomatic men (7; 9.0%).
There is a strong association with M. genitalium bacterial load and clinical
urethritis. Patients with urethral discharge had significantly higher M. genitalium
concentrations than those with only burning on micturition (p<0.001), and the
bacterial concentrations in men with symptoms and/or signs of urethritis were
significantly higher than that in asymptomatic men (p=0.02). As the number of
organisms increased, the severity of the symptoms increased; an indication of
the role that the organism plays in disease progression.
In conclusion, by applying the modified Koch postulates, it was shown that
Mycoplasma genitalium is by no means a passenger, but rather an important
cause of adult male urethritis that should be taken into account when making
diagnosis and when designing treatment strategies.
