Background: Neisseria gonorrhoeae strains resistant to ceftriaxone have been described in both Asia and Europe and strains with reduced susceptibility have been reported worldwide. Neisseria gonorrhoeaemulti-antigen sequence typing (NG-MAST) genogroup 1407 (G1407), an internationally successful strain group associated with men who have sex with men, has resulted in multiple treatment failures with extended-spectrum cephalosporins. We performed phenotypic and genotypic surveillance for G1407 strains in California during 2011-2013.
Methods: Urethral N. gonorrhoeaeisolates (N=1,756) were collected from men visiting public health clinics in San Francisco, Los Angeles, Orange and San Diego counties during 2011-2013. Minimum inhibitory concentrations (MIC) were determined by Etest and NG-MAST was used to assess strain diversity.
Results: G1407 isolates were detected in all four counties sampled, were responsible for 100% of the ceftriaxone alert value MICs (MIC >= 0.125 μg/mL) seen during the study period and represented 6.2 % (109/1,756) of all isolates. After grouping isolates by quarter, we observed an increase in both mean G1407 ceftriaxone MIC and the alert value MIC rate between the first quarter of 2011 and the first quarter of 2012. Both measures then decreased between the second quarter of 2012 and the second quarter of 2013.
Conclusions: The international spread of G1407 has reached California, although it is unknown whether it has resulted in treatment failures. It is notable that during the study period, both the United Kingdom and United States instituted novel treatment recommendations that included dual therapy with ceftriaxone and azithromycin. The ceftriaxone MIC decreases seen in California were preempted by the treatment recommendation changes in the UK and began one quarter before treatment recommendations were changed in the United States.