Genomic epidemiology of Streptococcus agalactiae ST283 in Southeast Asia

Pakorn Aiewsakun,Yuttapong Thawornwattana,Wuthiwat Ruangchai,Bharkbhoom Jaemsai,Surakameth Mahasirimongkol,Paveesuda Suksomchit,Anchalee Homkaew,Prasit Palittapongarnpim,Padungsri Dubbs

doi:10.1038/s41598-022-08097-0

Abstract

Streptococcus agalactiae, also known as Lancefield Group B Streptococcus (GBS), is typically regarded as a neonatal pathogen; however, several studies have shown that the bacteria are capable of causing invasive diseases in non-pregnant adults as well. The majority of documented cases were from Southeast Asian countries, and the most common genotype found was ST283, which is also known to be able to infect fish. This study sequenced 12 GBS ST283 samples collected from adult patients in Thailand. Together with publicly available sequences, we performed temporo-spatial analysis and estimated population dynamics of the bacteria. Putative drug resistance genes were also identified and characterized, and the drug resistance phenotypes were validated experimentally. The results, together with historical records, draw a detailed picture of the past transmission history of GBS ST283 in Southeast Asia.

Highlights

Streptococcus agalactiae, known as Lancefield Group B Streptococcus (GBS), is typically regarded as a neonatal pathogen; several studies have shown that the bacteria are capable of causing invasive diseases in non-pregnant adults as well
Complete genomes of 12 GBS isolates were sequenced in this study, all of which were obtained from non-pregnant Thai adult patients with sepsis, septic arthritis, or meningitis, that were treated in hospitals in Bangkok or nearby provinces in Thailand (Table 1)
All isolates belonged to capsular polysaccharide (CPS) type III and were determined to be of the sequence type sequence type 283 (ST283) based on the allelic profiles of seven housekeeping genes, including alcohol dehydrogenase gbs0054, phenylalanyl tRNA synthetase, amino acid transporter gbs0538, glutamine synthetase, serine dehydratase gbs2105, glucose kinase gbs0518, and transketolase gbs2105

Summary

Introduction

Streptococcus agalactiae, known as Lancefield Group B Streptococcus (GBS), is typically regarded as a neonatal pathogen; several studies have shown that the bacteria are capable of causing invasive diseases in non-pregnant adults as well. It has been reported that the predominant and expanded clones within each of these CCs usually contain tetracycline resistance genes, such as tet(O) and tet(L), but most commonly tet(M), typically carried by an integrative and conjugative element (ICE), mostly of the families Tn916 or Tn580113 These expanded clones form monophyletic clades including isolates from many countries around the world, and each clone appeared to share an ICE with a tetracycline resistance gene at the same genomic position[13]. Epidemiological analyses suggested that the outbreak was significantly associated with consumption of raw freshwater fish, but not consumption of sashimi, sushi, or raw shellfish, or exposure to fish-related activities[16,24]

Methods

Results

Conclusion