Alarming data have recent been reported (Yin & Chen) (Y&C) from the China Gonococcal Resistance Surveillance Programme (China-GRSP), covering seven (mostly coastal) provinces in the period 2013-2016. The study is relevant for Chinese national treatment policy, which currently recommends azithromycin monotherapy. However, with an estimated 45% of the world’s 78 million incident cases occurring in the Western Pacific Religion (as of 2012), these data also have an international importance, given concern about the likely future emergence and swift international spread of multi-resistant infection.
The study defines resistance to azithromycin as a minimum inhibitory concentration (MIC) of ≥1 mg/l, and ‘decreased susceptibility’ to ceftriaxone at ≥0.125 mg/l. Resistance break-points are set by the European Committee for Antimicrobial Susceptibility Testing (EUCAST) at 0.25 mg and 0.125 mg respectively (clinical breakpoints). Of the 3,849 isolates collected by the Y&C study, the proportion with resistance, or decreased susceptibility (Chinese definition), was 18.6% over the four years for azithromycin, and fluctuating between 9.7% and 12.2% for ceftriaxone. There was no clear upward or downward trend over the four-year period except in the case of resistance/reduced susceptibility to combined Azithromycin and Ceftriaxone. This followed a steady upward trend from 1.9% (2013) to 3.3% (2016). There are as yet no cases documented of treatment failure.
To set this in context, data reported for Europe (EUCAST) by Cole & Unemo (STI) estimate the proportion of azithromycin-resistant (MIC ≥0.25 mg) isolates for 2015 at 7.1%, and the proportion of isolates with ceftriaxone resistance (MIC= ≥0.125 mg) among MSM, females, and heterosexual males at 0.5%; 1% and 4.7% respectively. Artin & Mulvey (STI) reporting data for Canada bemoan levels of azithromycin resistance (MIC ≥2 mg) at 3.3% rising to 4.7% on the grounds that they approach the point at which WHO ceases to recommend the therapy. The general trend towards decreased ceftriaxone susceptibility is already evident over the long term in the UK (Town & Hughes (STI)) – though ‘stewardship’ of the last effective antibiotics may have had some impact in recent years. But the levels of resistance seen in the Y&C study are of a different order to what is reported for Europe.
It may also be that Y&C under-report. A fundamental limitation (one presumably imposed by significant cultural constraints) is that pharyngeal and anal samples were taken only from those claiming to be MSM. While 91% of the isolates came from men, apparently only 1.5% self-classified as bisexual or MSM. This presumably means that only a very small proportion of MSM participants were tested at the pharyngeal and anal sites.