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Journal of Medical Microbiology logo Journal of Medical Microbiology

Volume 74, Issue 3

Predomination of hypervirulent ST283 and genetic diversity of levofloxacin resistance in multidrug-resistant, hypervirulent in Thailand Open Access

Abstract

. Group B (GBS) is a multi-host pathogen causing pneumonia and meningitis in humans as well as streptococcal diseases in tilapia and mastitis in cattle. Thailand has experienced a significant increase in GBS infections that greatly impact health and economics.

. The antimicrobial resistance (AMR) and genotype data of GBS in Thailand are still limited and require further study.

. This study aimed to describe AMR profiles and molecular characteristics, especially antimicrobial resistance genes (ARGs) and virulence factor (VF) genes of GBS in Thailand.

. AMR profiles of 221 GBS isolates from humans, fish and freshwater were examined. Whole-genome sequencing of 41 representative isolates was used to investigate capsular genotypes and sequence types (STs), ARGs and VF genotypes.

. All GBS isolates were susceptible to penicillin; the majority (99.1%) showed resistance to tetracycline. In addition, the rates of resistance to clindamycin, erythromycin and levofloxacin were 22.6%, 20.4% and 2.3%, respectively; multidrug-resistant (MDR) isolates (TE-E-CM and TE-E-CM-LVX) were 19.5%. Among 41 representative isolates, the dominant types were capsular genotype III (63.4%) and ST283 (43.9%). ARGs associated with resistance to tetracycline (, and ), erythromycin (, , and ) and clindamycin (, and ) were identified. Additionally, point mutations responsible for levofloxacin resistance, S81L in GyrA, S79F/Y in ParC and H221Y in ParE, were found. The MDR isolates belonged to various STs, predominantly clustering in capsular types III (60.0%) and Ib (30.0%). The MDR-hypervirulent ST17 and ST19 harboured multiple ARGs and mutations affecting quinolone resistance. Different VF gene patterns were found among hypervirulent STs (ST12, ST17, ST19 and ST283). Notably, a unique deletion [c.(1013_1020)delG] in was found only in ST283.

. This study elucidated significant antimicrobial characteristics of a substantial number of GBS in Thailand. Moreover, the distribution of the hypervirulent ST283 and the genotypes of MDR-hypervirulent GBS were first described.

  • Received:
  • Accepted:
  • Published Online:
Keyword(s): antimicrobial resistance gene , group B Streptococcus , multi-host pathogen , sequence type and virulence factor
Funding
This study was supported by the:
  • Centre for Research and Development of Medical Diagnostic Laboratories (CMDL), Faculty of Associated Medical Sciences, Khon Kaen University, Thailand
    • Principal Award Recipient: WajeeornOuancharee
  • National Research Council of Thailand (Award 29418)
    • Principal Award Recipient: NichaCharoensri
© 2025 The Authors
  • This is an open-access article distributed under the terms of the Creative Commons Attribution License.
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2025-03-18
2026-01-20

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Predomination of hypervirulent ST283 and genetic diversity of levofloxacin resistance in multidrug-resistant, hypervirulent Streptococcus agalactiae in Thailand
J. Med. Microbiol. 74, 001970 (2025); https://doi.org/10.1099/jmm.0.001970
/content/journal/jmm/10.1099/jmm.0.001970
/content/journal/jmm/10.1099/jmm.0.001970
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