Evaluación de métodos moleculares para el diagnóstico de las infecciones de transmisión sexual y resistencia antibiótica de Mycoplasma genitalium

Abstract

In the first chapter, a comparison was made between tests based on real-time PCR (RT-PCR) and Transcription Mediated Amplification (TMA), for the diagnosis of STIs. A total of 622 clinical samples from different anatomical sites were analyzed using both methods. A total of 88 (14.1%) and 66 (10.6%) samples were found positive for either of the TMA assays used and for the RTPCR assay, respectively. The TMA assays showed a slightly higher rate of positive results for all pathogens, except for T. vaginalis. The most frequently detected pathogen was C. trachomatis (37 samples; 5.9% with TMA assays) and the anatomical site with the highest prevalence of microorganisms was a non-urogenital site, the pharynx (27 positive samples; 4.3%). Using the TMA assays as the reference method, the comparison showed that the mean specificity of multiplex RT-PCR was 100% for all four pathogens. However, a mean sensitivity of 74.5% was observed, showing 95.2% (CI95%; 93.6-96.9) overall agreement (κ = 0.80) of RT-PCR versus TMA techniques. The second chapter evaluated the clinical performance of a new STI diagnostic method using microarrays (STD Direct Flow Chip kit) in two different ways: (i) from purified DNA from three hundred and fifty-eight clinical specimens, with diagnostic sensitivity and specificity of 99.4% and 100%, respectively, and 99% concordance (kappa index, κ = 0.97) with the reference method, and (ii) by direct PCR from six hundred and thirty-three specimens, with sensitivity, specificity and concordance values of 98.4%, 99.9% and 98.0% (κ = 0.95), respectively. In the third chapter, we focused on the study of antimicrobial resistance in M. genitalium (MG), for which resistance rates in our environment are unknown. For this purpose, MG-positive samples collected between June 2018 and June 2019 were analyzed by 23S rRNA and parC gene sequencing. A total of 77 patients (24 men who have sex with men (MSM), 30 heterosexual men and 23 women) were included, showing mutations associated with macrolide and fluoroquinolone resistance in 36.4% (95% CI: 25.7% to 48.1%) and 9.1% (95% CI: 3.7% to 17.8%) of patients, respectively. Being MSM and having had another STI in the past year were significantly associated with macrolide-resistant MG infection, while no association was found with fluoroquinolone resistance.