Available online 18 August 2022, 106656

All identified isolates were susceptible to ceftriaxone.

Gonococcal resistance to azithromycin increased from 2% in 2013 to 12% in 2020

Genotypic resistance demonstrated a good diagnostic performance for phenotypic resistance of cefixime azithromycin and ciprofloxacin.

International surveillance data show a constant rise in the number of Neisseria gonorrhoeae (Ng) infections and an increase in Ng drug-resistance. As recent Ng-surveillance data in Austria is scarce, we investigated phenotypic and genotypic antimicrobial resistance in Ng isolates.

We collected 440 Ng samples at the Medical University of Vienna and determined the minimal inhibitory concentrations (MIC) for a range of different antibiotics. We recorded sampling-sites and treatments and performed whole-genome sequencing of Ng-isolates, using allele libraries to determine genotypic resistance.

The median MICs for ceftriaxone, cefixime, azithromycin, ciprofloxacin, tetracycline and penicillin were <0.002µg/ml, <0.016µg/ml, 0.25µg/ml, 2.0µg/ml, 1.5µg/ml and 0.25µg/ml, respectively. Annual comparison showed mostly stable MICs for almost all antimicrobial agents; only for azithromycin, we observed an increase in median MICs since 2017 (0.25µg/ml). There was no genetic resistance to ceftriaxone; 8% of samples displayed resistance mutations against cefixime, primarily located in the penA gene. Resistance to azithromycin increased from 2% in 2013 to 12% in 2020. MtrD mosaic had the highest impact on azithromycin susceptibility: 47% of the resistant isolates showed this mutation. The majority of gonorrhoea cases were successfully treated with either ceftriaxone or a ceftriaxone/azithromycin regime. Two treatment failures occurred under monotherapy with doxycycline. Overall, genotypic resistance corresponded significantly to all respective MICs.

The rate of Ng-resistance to antibiotics remained stable in Vienna over the last decade, except for azithromycin. The strong correlation between genetic and phenotypic patterns in our study holds promise for future diagnostics of Ng resistance based on genotypes.

Gonorrhoea, Antimicrobial resistance

Azithromycin

Ceftriaxone, Whole genome sequencing

© 2022 Published by Elsevier Ltd.