Mycoplasma genitalium antibiotic resistance-associated mutations in genital and extragenital samples from men-who-have-sex-with-men attending a STI clinic in Verona, Italy

Abstract

BackgroundMycoplasma genitalium (MG) is one of the most warning emerging sexually transmitted pathogens also due to its ability in developing resistance to antibiotics. MG causes different conditions ranging from asymptomatic infections to acute mucous inflammation. Resistance-guided therapy has demonstrated the best cure rates and macrolide resistance testing is recommended in many international guidelines. However, diagnostic and resistance testing can only be based on molecular methods, and the gap between genotypic resistance and microbiological clearance has not been fully evaluated yet. This study aims at finding mutations associated with MG antibiotic resistance and investigating the relationship with microbiological clearance amongst MSM.MethodsFrom 2017 to 2021, genital (urine) and extragenital (pharyngeal and anorectal swabs) biological specimens were provided by men-who-have-sex-with-men (MSM) attending the STI clinic of the Infectious Disease Unit at the Verona University Hospital, Verona, Italy. A total of 1040 MSM were evaluated and 107 samples from 96 subjects resulted positive for MG. Among the MG-positive samples, all those available for further analysis (n=47) were considered for detection of mutations known to be associated with macrolide and quinolone resistance. 23S rRNA, gyrA and parC genes were analyzed by Sanger sequencing and Allplex™ MG and AziR Assay (Seegene).ResultsA total of 96/1040 (9.2%) subjects tested positive for MG in at least one anatomical site. MG was detected in 107 specimens: 33 urine samples, 72 rectal swabs and 2 pharyngeal swabs. Among them, 47 samples from 42 MSM were available for investigating the presence of mutations associated with macrolide and quinolone resistance: 30/47 (63.8%) showed mutations in 23S rRNA while 10/47 (21.3%) in parC or gyrA genes. All patients with positive Test of Cure (ToC) after first-line treatment with azithromycin (n=15) were infected with 23S rRNA-mutated MG strains. All patients undergoing second-line moxifloxacin treatment (n=13) resulted negative at ToC, even those carrying MG strains with mutations in parC gene (n=6).ConclusionOur observations confirm that mutations in 23S rRNA gene are associated with azithromycin treatment failure and that mutations in parC gene alone are not always associated with phenotypic resistance to moxifloxacin. This reinforces the importance of macrolide resistance testing to guide the treatment and reduce antibiotic pressure on MG strains.

Detection of resistance to macrolides and fluoroquinolones in Mycoplasma genitalium by targeted next-generation sequencing

“…As in other studies ( 22 , 23 ), the gyr A locus in M. genitalium is remarkably well conserved in our population also (e.g., only two samples have exhibited amino acid substitutions in gyr A, both with uncertain significance), and none of the 10 nonsynonymous mutations in gyr B identified in this study were previously published. Thus, in our setting, as described in other works, parC appears to be the major determinant for fluoroquinolone resistance, while the contribution of gyrase loci may be considered minor.…”

Azithromycin and moxifloxacin resistance determinants in Mycoplasma genitalium in Lleida, Spain

“…Azithromycin inhibits protein synthesis and its resistance is associated with mutations in the region V of the 23S rRNA gene, being the point mutations at positions 2058 and 2059 the most frequent ones [7]. Azithromycin-resistant MG (Azi-R-MG) has been reported worldwide in the last years [2,5,[8][9][10][11]. On the other hand, mutations in the parC and/or gyrA are responsible for moxifloxacinresistant MG (Moxi-R-MG) [12].…”

“…Novel technologies to detect these mutations which include real-time PCR are excellent options to characterize these mechanisms when sequencing is not available [11]. The evaluation of acquired moxifloxacin resistance has been conducted in several studies, but the sample size evaluated is still not sufficient [1][2][3]7].…”

“…As it was previously described, we found that 52.8% of men with an Azi-R-MG were MSM. The high bacterial STI burden and frequent exposure to macrolide treatment may account for the high prevalence of macrolide-resistant MG among MSM [ 2 ].…”

“…Mycoplasma genitalium (MG) is a microorganism related to sexually transmitted infections (STI). The main route of transmission is direct genital-genital mucosal contact [ 1 , 2 ]. MG diagnosis has been improved in recent years.…”