Background Resistance of Neisseria gonorrhoeae against third generation cephalosporins is a threat to public health. A known determinant is the presence of a mosaic penA gene in N.gonorrhoeae, partially derived from commensal Neisseria spp. We report resistance figures of N.gonorrhoeae against ceftriaxone from 2010 to 2013 and looked at penA characteristics of specific strains.

Methods MICs for ceftriaxone were assesed from 2010–13 (4191 strains). A specific PCR identifying strains with a mosaic penA gene and partial sequence analysis (aa 180 – 550) of the penA gene were used for further characterisation of specific strains.

Results Strains resistant to ceftriaxone were not found during the study period. The frequency of strains with an increased MIC (>0.032) to ceftriaxone was 5.2% in 2010, this rate dropped to 2.0 and 3.1% in 2011 and 2012 respectively, but increased to 7.8% in 2013. In 2010, 46/48 (96%) strains with an increased MIC against ceftriaxone contained a mosaic penA gene; in 2013, only 15/68 (22%) of such strains contained this gene. Sequence analysis of 16 of the strains isolated in 2013 with reduced susceptibility to ceftriaxone and lacking a mosaic penA gene showed that they all had an identical penA gene which was similar to type XVIII, including a 502 A-T mutation, but lacking the 543 G-S mutation.¹

Conclusion The recent increase of the frequency of strains with reduced susceptibility to ceftriaxone in 2013 is due to strains with a penA sequence not yet found in the Netherlands in 2010 among strains with reduced susceptibility to ceftriaxone.

Disclosure of interest statement Nothing to declare

Reference

1. Whiley DM, Limnios EA, Ray S, et al. Diversity of penA alterations and subtypes in Neisseria gonorrhoeae strains from Sydney, Austrlia, that are less susceptible to ceftriaxone. Antimicrob Agents Chemother. 2007;51:3111–6