Antimicrobial susceptibility profile of Neisseria gonorrhoeae from patients attending a medical laboratory, Institut Pasteur de Madagascar between 2014 and 2020 : phenotypical and genomic characterisation in a subset of Neisseria gonorrhoeae isolates

Abstract

OBJECTIVES : Antimicrobial-resistant Neisseria gonorrhoeae (NG) is a concern. Little is known about antimicrobial susceptibility profiles and associated genetic resistance mechanisms of NG in Madagascar. We report susceptibility data of NG isolates obtained by the medical laboratory (CBC) of the Institut Pasteur de Madagascar, Antananarivo, Madagascar, during 2014-2020. We present antimicrobial resistance mechanisms data and phenotype profiles of a subset of isolates.

METHODS : We retrieved retrospective data (N=395) from patients with NG isolated during 2014-2020 by the CBC. We retested 46 viable isolates including 6 found ceftriaxone and 2 azithromycin resistant, as well as 33 isolated from 2020. We determined minimal inhibitory concentrations for ceftriaxone, ciprofloxacin, azithromycin, penicillin, tetracycline and spectinomycin using Etest. We obtained whole-genome sequences and identified the gene determinants associated with antimicrobial resistance and the sequence types (STs).

RESULTS : Over the study period, ceftriaxone-resistant isolates exceeded the threshold of 5% in 2017 (7.4% (4 of 54)) and 2020 (7.1% (3 of 42)). All retested isolates were found susceptible to ceftriaxone, azithromycin and spectinomycin, and resistant to ciprofloxacin. The majority were resistant to penicillin (83% (38 of 46)) and tetracycline (87% (40 of 46)). We detected chromosomal mutations associated with antibiotic resistance in gyrA, parC, penA, ponA, porB and mtrR genes. None of the retested isolates carried the mosaic penA gene. The high rate of resistance to penicillin and tetracycline is explained by the presence of bla TEM (94.7% (36 of 38)) and tetM (97.5% (39 of 40)). We found a high number of circulating multilocus STs. Almost half of them were new types, and one new type was among the four most predominant.

CONCLUSIONS : Our report provides a detailed dataset obtained through phenotypical and genotypical methods which will serve as a baseline for future surveillance of NG. We could not confirm the occurrence of ceftriaxone-resistant isolates. Our results highlight the importance of implementing quality-assured gonococcal antimicrobial resistance surveillance in Madagascar.