Molecular characterization and antimicrobial resistance of Streptococcus agalactiae isolated from pregnant women in Japan, 2017-2021

Mitsuyo Kawaguchiya; Noriko Urushibara; Meiji Soe Aung; Shigeki Shimada; Mayumi Nakamura; Masahiko Ito; Satoshi Habadera; Nobumichi Kobayashi

doi:10.1016/j.ijregi.2022.07.002

Molecular characterization and antimicrobial resistance of Streptococcus agalactiae isolated from pregnant women in Japan, 2017-2021

IJID Reg. 2022 Jul 14:4:143-145. doi: 10.1016/j.ijregi.2022.07.002. eCollection 2022 Sep.

Authors

Mitsuyo Kawaguchiya¹, Noriko Urushibara¹, Meiji Soe Aung¹, Shigeki Shimada², Mayumi Nakamura³, Masahiko Ito³, Satoshi Habadera³, Nobumichi Kobayashi¹

Affiliations

¹ Department of Hygiene, Sapporo Medical University School of Medicine, Sapporo, Japan.
² Mommy's Clinic Chitose.
³ Sapporo Clinical Laboratory, Inc., Sapporo, Japan.

Abstract

Objectives: This study aimed to elucidate the molecular characteristics and antimicrobial resistance of Streptococcus agalactiae (group B streptococcus, GBS) colonizing pregnant women in Japan.

Methods: GBS isolates obtained from screening of pregnant women from 2017 to 2021 were analyzed for capsular serotype, sequence type (ST), and antimicrobial susceptibility. For levofloxacin-resistant isolates, mutations in the quinolone resistance-determining regions (QRDRs) of the gyrA, gyrB, and parC genes were analyzed.

Results: Seventy-six GBS isolates were recovered from 1090 women (isolation rate: 7.0%). Of the 76 isolates, serotype III (31.6%) was the most prevalent, followed by V (19.7%), Ia (17.1%), and Ib (10.5%). Among the 22 STs identified, capsular serotype III/ST335-clonal complex (CC) 19 lineage was dominant (13.2%), followed by Ia/ST23, III/ST17, and V/ST1. Levofloxacin resistance was detected in 15.8% (n=12) of all the isolates, with serotype Ib being the most common. Most levofloxacin resistant isolates belonged to serotype Ib/CC10 or serotype V/CC19, with double mutations in the QRDRs, Ser81Leu in GyrA and Ser79Phe in ParC.

Conclusions: The present study indicates the prevalence of the serotype III/ST335 (CC19) lineage, and the spread of serotype Ib/CC10 and serotype V/CC19 lineages, which are responsible for levofloxacin resistance in colonizing GBS in pregnant women in Japan.

Keywords: CC, clonal complex; GBS, group B streptococcus; Japan; MICs, minimum inhibitory concentrations; MLST, multilocus sequence typing; QRDRs, quinolone resistance-determining regions; Quinolone resistance; ST, sequence type; Sequence type; Serotype; Streptococcus agalactiae.