Abstract
The goal of this work was to study the phenotypic susceptibility and resistance determinants of N. gonorrhoeae isolates to beta-lactam antimicrobials (benzylpenicillin and ceftriaxone). A total of 522 clinical isolates collected in Russia in 2015–2017 were analysed for susceptibility using the agar dilution method. DNA loci involved in antimicrobial resistance were identified using DNA microarray analysis and sequencing. Resistance to benzylpenicillin remained high, with 7.7% of isolates resistant (MICpen > 1 mg/L) and 47.5% of isolates showing intermediate susceptibility (MICpen = 0.12–1 mg/L). The most frequent resistance determinant (72.4% isolates) was the Asp345 insertion in penA, both as a single mutation and in combination with other mutations, particularly with the substitution Leu421Pro in ponA (39.0%). Mutations affecting the influx and efflux of drugs were also found, including amino acid substitutions in PorB (26.8% isolates) and delA in the promoter region of mtrR (22.8%). The accumulation of mutations in chromosomal genes (penA, pon, porA, and mtrR) led to a stepwise increase in MICpen to values characteristic of intermediate resistance. The presence of blaTEM plasmids was found in 25 isolates (4.8%), resulting in a strong increase in resistance to penicillin (MICpen > 16 mg/L) compared with the chromosomal mutations; 23 plasmids were of the African type with TEM-1 beta-lactamase, and two plasmids were of the Toronto/Rio type with TEM-135 beta-lactamase. Only three isolates were found with reduced susceptibility to ceftriaxone, with MICcef = 0.12–0.25 mg/L. Sequencing of penA did not reveal mutations associated with resistance to third-generation cephalosporins, and the gene structure was non-mosaic. The majority of isolates (21 of 25) carrying the blaTEM plasmid also contained the conjugative plasmid with tetM (resistance to tetracyclines), consistent with previously reported data that the presence of the conjugative plasmid facilitates the transfer of other plasmids associated with antimicrobial resistance.
Highlights
Gonorrhoea is a sexually transmitted infection caused by the gram-negative bacterium Neisseria gonorrhoeae
The goal of this work was to study the susceptibility of the current population (2015–2017) of N. gonorrhoeae isolates from the Russian Federation to beta-lactam antibiotics and to identify genetic determinants of resistance to these drugs, including investigation of the types of blaTEM plasmid genes and beta-lactamase variants
N. gonorrhoeae clinical isolates were collected by the State Research Center of Dermatovenerology and Cosmetology, Russian Ministry of Health, Moscow, within the framework of the Russian Gonococcal Antimicrobial Surveillance Programme (RU-GASP) [9,10]
Summary
Gonorrhoea is a sexually transmitted infection caused by the gram-negative bacterium Neisseria gonorrhoeae. A distinctive feature of N. gonorrhoeae is its ability to rapidly accumulate different mutations to acquire resistance against the antibiotics used for its treatment [1,2]. The WHO has declared drug resistance in N. gonorrhoeae to be an emerging threat that has the potential to move gonorrhoea to the category of incurable infections [3]. Due to the development of a high resistance level in the population, it is no longer used for gonorrhoea treatment. The antibiotics recommended for the treatment of gonorrhoea in Russia are ceftriaxone, a 3rd-generation cephalosporin, and spectinomycin. Unlike in European countries, azithromycin has never been recommended for gonorrhoea treatment in Russia, and cefixime has not yet been introduced into medical practice
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