Emergence of a Neisseria gonorrhoeae clone with reduced cephalosporin susceptibility between 2014 and 2019 in Amsterdam, The Netherlands, revealed by genomic population analysis.

Background: Emerging resistance to cephalosporins in Neisseria gonorrhoeae (Ng) is a major public health threat, since these are considered antibiotics of last resort. Continuous surveillance is needed to monitor the circulation of resistant strains and those with reduced susceptibility.

Objectives: For the purpose of epidemiological surveillance, genomic population analysis was performed on Ng isolates from Amsterdam with a focus on isolates with reduced susceptibility to ceftriaxone.

Methods: WGS data were obtained from 318 isolates from Amsterdam, the Netherlands between 2014 and 2019. Isolates were typed according to MLST, Ng Multi-Antigen Sequence Typing (NG-MAST) and Ng Sequence Typing for Antimicrobial Resistance (NG-STAR) schemes and additional resistance markers were identified. Phylogenetic trees were created to identify genetic clusters and to compare Dutch and non-Dutch MLST7827 isolates.

Results: MLST7363 and MLST1901 were the predominant strains having reduced susceptibility to ceftriaxone during 2014-16; MLST7827 emerged and dominated during 2017-19. NG-STAR38 and NG-MAST2318/10386 were predominant among MLST7827 isolates. MLST7827 reduced susceptibility isolates carried a non-mosaic 13.001 penA allele with an A501V mutation and porB1b G120K/A121D mutations, which were lacking in susceptible MLST7827 isolates. Phylogenetic analysis of all publicly available MLST7827 isolates showed strong genetic clustering of Dutch and other European MLST7827 isolates.

Conclusions: MLST7827 isolates with reduced ceftriaxone susceptibility have emerged during recent years in Amsterdam. Co-occurrence of penA A501V and porB1b G120K/A121D mutations was strongly associated with reduced susceptibility to ceftriaxone. Genetic clustering of Dutch and other European MLST7827 isolates indicates extensive circulation of this strain in Europe. Close monitoring of the spread of this strain having an alarming susceptibility profile is needed.