High percentage of the ceftriaxone-resistantNeisseria gonorrhoeaeFC428 clone among isolates from a single hospital in Hangzhou, China

Abstract Objectives Ceftriaxone is currently the last-remaining empirical antimicrobial therapy for treatment of gonorrhoea. However, the high-level ceftriaxone-resistant gonococcal FC428 clone has shown transmission in China in recent years. Therefore, the aim of this study was to analyse ceftriaxone resistance among a collection of recent clinical isolates, with a specific focus on prevalence of the FC428 clone. Methods A total of 70 consecutive gonococcal isolates were collected between May and October 2019 from a single hospital in Hangzhou, China, and analysed for antimicrobial susceptibility by the agar dilution method. STs were determined by PCR and sequences and isolates related to the FC428 clone were further characterized by WGS and phylogenetic analysis. Results Ceftriaxone resistance (MIC >0.125 mg/L) was observed in 21 (30%) isolates, while 14 (20%) isolates displayed a ceftriaxone MIC of 0.125 mg/L. Importantly, seven (10%) isolates were related to the gonococcal FC428 clone based on the presence of mosaic penA allele 60.001, displaying identical or closely related STs, and phylogenetic analysis after WGS. These seven isolates displayed high-level ceftriaxone resistance (MIC = 1 mg/L) and all associated gonorrhoea cases resulted in treatment failure because oral cephalosporins were initially prescribed. Subsequent re-treatment with a higher dose (2 g) of IV ceftriaxone appeared to be successful because all patients returning for test-of-cure became culture-negative. Conclusions Here, we report a high percentage of the internationally spreading gonococcal FC428 clone among clinical isolates from a single hospital in Hangzhou, China. A high dose of ceftriaxone is currently the only recommended and effective therapy.