Introduction The prevalence of azithromycin resistance in Neisseria gonorrhoeae (NG) including high-level resistance (HL-AziR NG) is increasing in England. It has been suggested that exposure to azithromycin at sub-optimal doses may facilitate development of azithromycin resistance in NG. We investigated whether treatment history for non-rectal chlamydia (CT) or NG (as proxies for azithromycin exposure) in GUM services was associated with susceptibility of NG to azithromycin.
Methods Descriptive and negative binomial regression analyses of azithromycin Minimum Inhibitory Concentration (MIC) data from 4608 NG isolates collected by the Gonococcal Resistance to Antimicrobials Surveillance Programme (GRASP) 2013–2015 (matched to GUMCADv2 data on CT/NG diagnoses) were performed. Descriptive analyses of previous CT/NG among 56 HL-AziR NG isolates (MIC>256 mg/L) were also performed (2013–2016).
Results Modal azithromycin MIC was 0.25mg/L (1 dilution below the resistance breakpoint) in those with and without history of CT or GC. There were no differences in MIC distribution by previous CT/NG, nor by time since most recent infection (CT: p=0.97; NG: p>0.99). Among patients with HL-AziR NG, 4 (8%) were treated for CT and 4 (8%) for NG in the previous year, compared with 9% and 13% respectively for all GRASP patients.
Discussion There was no evidence of an association between previous CT/NG treatment in GUM services and subsequent presentation with an azithromycin-resistant strain. However, 46% of CT diagnoses occur in non-GUM settings therefore further research is needed to explore whether an association with azithromycin exposure in other settings and for other conditions exists.
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