Clonal Expansion of New Penicillin-Resistant Clade of Neisseria meningitidis Serogroup W Clonal Complex 11, Australia

Abstract

In Western Australia, Neisseria meningitidis serogroup W clonal complex 11 became the predominant cause of invasive meningococcal disease in 2016. We used core-genome analysis to show emergence of a penicillin-resistant clade that had the penA_253 allele. This new penicillin-resistant clade might affect treatment regimens for this disease.

Keywords: Australia; Neisseria meningitidis; Western Australia; antimicrobial resistance; bacteria; clonal complex 11; clonal expansion; core-genome analysis; meningitis/encephalitis; meningococcal disease; penicillin resistance; serogroup W.

Figure 1

Neighbor-joining dendrogram (500 bootstrap values) for core genome sequences of clonal complex 11 Neisseria meningitidis strains with serogroup W capsules, Western Australia, Australia, January 2013–December 2016. The resistance phenotype for the penicillin G (PenG) gene for each isolate is provided using the following breakpoints: sensitive (MIC <0–0.06 mg/L), intermediate (0.12–0.25 mg/L) and resistant (>0.5 mg/L). Two clusters (A and B) were observed, which contain isolates that differ in penicillin resistance profile. Of 1,605 core-genome loci, a minimum of 244 are different between clusters A and B. The more recent cluster B appeared in early 2016 and contains penicillin-resistant isolates. Strain ExNm672 does not belong to either cluster. The dendrogram is drawn to scale, and sum of branch lengths between 2 strains indicates the proportion of nucleotide differences between those core genomes (≈1.5 Mb) within the pairwise alignment. Gray shaded box indicates isolates in cluster B. Scale bar indicates nucleotide substitutions per site. ID, identification; ST, sequence type.

Figure 2

Phylogenetic reconstruction by using an unrooted neighbor-net algorithm of core genomes of clonal complex 11 Neisseria meningitidis strains with serogroup W capsules (MenW:cc11), Western Australia, Australia, January 2013–December 2016. Blue circles indicate isolates in cluster A from Western Australia; red circles indicate isolates in cluster B from Western Australia; gray circle indicates ExNm672, a strain isolated from a traveler; open squares indicate the 5 MenW:cc11 isolates in the PubMLST database (http://pubmlst.org/neisseria) that contains the penA_253 allele; and black squares indicate reference MenW:cc11 strains, isolated after 2010, as described by Lucidarme et al. (8). M7124 is the Hajj clone isolated in Saudi Arabia in 2000. Numbers in parentheses indicate PubMLST numbers of reference isolates. Scale bar indicates nucleotide substitutions per site.