[ODP2] 1. Taxonomy / Epidemiology / Infectious diseases -b. Epidemiology and molecular epidemiology

[ODP-008] Clonal lineages and antimicrobial resistance of nonencapsulated Streptococcus pneumoniae in Hokkaido

Mitsuyo Kawaguchiya¹, Noriko Urushibara¹, Meiji Soe Aung¹, Kenji Kudo², Masahiko Ito², Nobumichi Kobayashi¹ (¹Dept. Hygiene, Sapporo Med. Univ., Sch. Med., ²Sapporo Clinical Laboratory, Inc.)

Objectives: The emergence and spread of nonencapsulated Streptococcus pneumoniae (NESp) is a public health concern in the post-pneumococcal conjugate vaccine era. We analyzed the prevalence, molecular characteristics, and antimicrobial resistance of NESp in Hokkaido.
Methods: Among 4463 S. pneumoniae isolates collected from non-invasive infection cases between 2011 and 2019, NESp isolates were identified using molecular and phenotypical methods. NESp isolates were analyzed for antimicrobial susceptibility, genotype, and virulence-associated genes.
Results: A total of 71 NESp isolates were identified (1.6% of all the isolates) and assigned to the null capsule clade (NCC)1 (pspK+) (94.4%) or NCC2 (aliC+/aliD+) (5.6%). Five dominant sequence types (STs) were ST7502 (23.9%), ST4845 (19.7%), ST16214 (11.3%), ST11379 (9.9%), and ST7786 (7.0%). These dominant STs and all seven novel STs were related to the sporadic NESp lineage ST1106 or PMEN clone Denmark14-ST230. High non-susceptibility rates of NESp were observed for trimethoprim-sulfamethoxazole, erythromycin, and tetracycline (>92.9%), and multidrug resistance was observed in 88.7% of the NESp isolates, including all the ST7502, ST4845, and ST11379 isolates.
Conclusions: The present study revealed that the dominant clonal groups of NESp were associated with a high prevalence of non-susceptibility to antimicrobials in Hokkaido.