Resistencia a azitromicina en Mycoplasma genitalium y Neisseria gonorrhoeae en Barcelona

Abstract

Sexually-transmitted infections (STIs) are a major public health problem. Mycoplasma genitalium is a sexually-transmitted microorganism with natural resistance to beta-lactams, its treatment is limited to a few families of antibiotics and macrolides are the first-line. Neisseria gonorrhoeae is the causative agent of gonorrhea. The World Health Organization recommends its close surveillance due to the emergence of resistance to most of the antibiotics used for treatment. Azithromycin is included in the treatment of STIs. Susceptibility to this antibiotic is decreasing both in M. genitalium and N. gonorrhoeae, a fact that limits therapeutic options. The emergence of resistance to azithromycin in these two bacteria motivated the completion of this doctoral thesis. The main objectives were 1) to determine the frequency of M. genitalium infection in a cohort of patients with and without risk factors for STIs in the influence area of CatLab (Vallés Occidental) and to determine resistance to azithromycin by molecular analysis of the associated determinants, and 2) to determine the N. gonorrhoeae clones with resistance to azithromycin that circulated in the area of influence of the Hospital de la Santa Creu i Sant Pau (Barcelona) and their associated resistance mechanisms. The frequency of M. genitalium infection was 3. 4% (95% CI 3. 2-3. 7) during the study period (2011-2017). Resistance to macrolides was 12. 6% in the prospective cohort (2014-2015). A2058G was the most prevalent of the three mutations detected, followed by A2058T and A2059G. The association of previous M. genitalium infections with infection by azithromycin-resistant strains was considered significant (p<0. 001). A total of 201 N. gonorrhoeae isolates from patients treated at the STI dispensary of the Hospital de la Santa Creu i Sant Pau in Barcelona (2019-2022) were analyzed. The frequency of resistance to azithromycin was 11% and to ciprofloxacin 66. 8%; ceftriaxone-resistant strains to were not detected. Of the azithromycin-resistant strains, the most prevalent clone belonged to MLST ST-9363 (NG-MAST ST-3935 and NG-STAR ST-193). The remaining strains belonged to MLST ST-11422 and MLST ST-9362. The molecular determinants of resistance to macrolides, quinolones, and beta-lactams were analyzed in the 15 azithromycin-resistant strains (MIC ≥2 mg/L) isolated during the study period and in two susceptible strains. The analyzed determinants were the gene encoding for 23S rRNA, MtrRCDE efflux pump and its promoter, ribosomal proteins L4 and L22 (rpID and rpIV, respectively), the MacAB efflux pump promoter, PorB porin, the genes encoding PBP1 and PBP2 (ponA and penA), and gyrA and parC genes. Acquired mef (A/B) and erm (A/B/C/F) genes were not detected. The low-level resistance to azithromycin in these strains was attributable to the substitutions detected in the L4 ribosomal protein and to overexpression of the MtrCDE efflux pump. Strains belonging to the MLST ST-9363 and ST-11422 presented the amino acid substitutions associated with macrolide resistancein the rpID determinant (V125A, A147G and R157Q), in the MtrR (D79N, S183N, M197I) and the mutations (A-C/G-A) in the mtrR promoter. These results suggest clonal spread of low-level resistance to azithromycin associated with these determinants in our geographic area.

Date of Award	27 Mar 2023
Original language	Spanish
Supervisor	Núria Prim Bosch (Director) & Fernando Sanchez Reus (Director)