PCR detection and prevalence of Mycoplasma genitalium

Abstract: Chlamydia and gonorrhea are major causes of sexually transmitted infections (STI) in adolescents worldwide. The infections are caused by Chlamydia trachomatis or Neisseria gonorrhoeae, bacteria with clinical manifestations such as urethritis, prostatitis and epididymitis among men, and urethritis, cervicitis and upper genital tract infection (i.e. pelvic inflammatory disease) among women. However, in many cases of genital tract infection, the etiology remains uncertain. In light of this, Mycoplasma genitalium was somewhat accidentally isolated in 1980 after prolonged incubation of urogenital specimens from men with non-gonococcal urethritis. Following the initial isolation in 1980, repeated attempts have been made to recover the extremely fastidious organism from clinical samples by culture techniques, but isolates have been rare and difficult to obtain. With the development of PCR methods in the early 1990s, detection of M. genitalium infection became more feasible.The aim in paper I was to compare three different PCR assays (conventional and real-time 16S rRNA gene PCR as well as real-time Mycoplasma genitalium adhesin protein (MgPa) gene PCR) for detection of M. genitalium. The study also determined the prevalence of M. genitalium. Clinical specimens collected from STI attendees, 381 men and 298 women, were used to determine the prevalence of M. genitalium and 213 of these specimens were used in the PCR comparative study. The prevalence of M. genitalium infection in men and women was 27/381 (7.1 %) and 23/298 (7.7 %) respectively. In the PCR comparative study, M. genitalium DNA were detected in 61/76 (80.3 %) of true-positive specimen by conventional 16S rRNA gene PCR, in 52/76 (68.4 %) by real-time 16S rRNA gene PCR and in 74/76 (97.4 %) by real-time MgPa gene PCR. Hence, real-time MgPa gene PCR is well suited for clinical diagnosis of M. genitalium in urogenital specimens from men and women.The aim in paper II was to determine whether a patients’ endocervical swab specimen can be transported in first void urine (FVU) as combined specimens in detection of Mycoplasma genitalium by real-time PCR. The study also compared two different DNA extraction methods (manual Chelex DNA extraction and automated BioRobot M48 DNA extraction) for observation of possible PCR inhibition. Clinical specimens collected from 329 women attending a STI clinic were used in the study. A total of 100 endocervical swab specimens transported in FVU was used in the PCR inhibition analysis. M. genitalium was detected in 25/329 (7.6 %) women. Endocervical swab specimens transported in FVU demonstrate higher sensitivity compared to both FVU alone and specimens transported in 2-SP medium detecting 24/25 (96 %), 22/25 (88 %) and 17/25 (68 %) of M. genitalium positive women, respectively. Automated BioRobot M48 DNA extraction was shown to be superior to manual Chelex extraction leaving no PCR inhibition and slightly higher DNA yield and/or better sensitivity. The results from these two studies are important knowledge in establishing the future diagnostic level of this STI in our county and also nationally.