Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2018

Alarming Expansion of Penicillin-resistant Serogroup W Neisseria meningitidis and Identification of a borderline-ceftriaxone-susceptible Strain in Western Australia (#72)

Shakeel Mowlaboccus 1 2 , Keith A Jolley 3 , James E Bray 3 , Geoffrey W Coombs 4 , Jane D Bew 5 , David J Speers 5 6 , Anthony D Keil 7 , Charlene M Kahler 1 2 8
  1. School of Biomedical Sciences, The University of Western Australia, Perth, Western Australia, Australia
  2. Marshall Center for Infectious Diseases Research and Training, The University of Western Australia, Perth
  3. Department of Zoology, University of Oxford, Oxford, UK
  4. School of Veterinary and Life Sciences, Murdoch University, Murdoch, Western Australia, Australia
  5. Department of Microbiology, PathWest Laboratory Medicine, Perth
  6. School of Medicine and Pharmacology, The University of Western Australia, Perth, Western Australia, Australia
  7. Department of Microbiology, PathWest Laboratory Medicine WA Princess Margaret Hospital for Children, Perth, Western Australia, Australia
  8. Telethon Kids Institute, Perth, Western Australia, Australia

Introduction

Neisseria meningitidis (meningococcus) causes invasive meningococcal disease (IMD) which has a mortality rate of 6%. Disease is predominantly caused by serogroups A, B, C, W, X or Y. Multi-locus sequence typing (MLST) classifies meningococci into sequence types (ST) and clonal complexes (cc). Recent global outbreaks have been caused by meningococcal serogroup W (MenW) belonging to the cc11 lineage. MenW has become the predominant cause of IMD in Australia since 2016.

 

Objective

The aim of this study was to analyse the whole-genome sequences of invasive MenW:cc11 from Western Australia (WA) and investigate changes in antibiotic susceptibility.

 

Methods

Genomic DNA of 33 MenW:cc11 strains isolated from patients in WA were sequenced using Illumina paired-ends. Raw reads were assembled and curated using the BIGSdb genomics platform from the PubMLST database.

 

Results

In WA, the first MenW:cc11 case appeared in 2013. This was followed by two cases in 2014, three cases in 2015, 13 cases in 2016 and 14 cases in 2017. In this collection, six different STs were identified – ST-11 (n=17), ST-1287 (n=3), ST-3298 (n=1) and ST-12351 (n=10), ST-13125 (n=1) and ST-13135 (n=1). Resistance to ciprofloxacin or rifampicin was not identified. However, variation in penicillin susceptibility was observed: 10 isolates showed high susceptibility (MIC=0.064 mg/L) and 23 isolates were resistant (0.25–0.5 mg/L). Core genome phylogeny identified two main clusters, A and B. All penicillin-susceptible isolates fell in Cluster A and possessed the penA_59 allele. The penicillin-resistant meningococci, all isolated in 2016 and 2017, fell in cluster B and possessed the penA_253 allele. Exchange of penA_59 for penA_253 in Cluster A isolates resulted in a significant increase in penicillin MIC. Finally, one outlier strain isolated from a traveler encoded a novel penA allele. This allele conferred reduced susceptibility to penicillin and to the extended-spectrum cephalosporin ceftriaxone.

 

Conclusions

In conclusion, core-genome analysis identified the emergence of a new cluster of penicillin-resistant MenW:cc11 in WA in 2016 which is currently expanding alarmingly and may thus impact treatment regimens internationally.