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One hypervirulent clone, sequence type 283, accounts for a large proportion of invasive Streptococcus agalactiae isolated from humans and diseased tilapia in Southeast Asia

Barkham T 1 , Zadoks RN 2 , Azmai MNA 3 , Baker S 4 , Bich VTN 5 , Chalker V 6 Show all authors , Chau ML 7 , Dance D 8 , Deepak RN 9 , van Doorn HR 10 , Gutierrez RA 7 , Holmes MA 11 , Huong LNP 4 , Koh TH 12 , Martins E 13 , Mehershahi K 14 , Newton P 8 , Ng LC 7 , Phuoc NN 15 , Sangwichian O 16 , Sawatwong P 16 , Surin U 17 , Tan TY 18 , Tang WY 19 , Thuy NV 20 , Turner P 21 , Vongsouvath M 8 , Zhang D 22 , Whistler T 16 , Chen SL 14

Affiliations 

  • 1 Department of Laboratory Medicine, Tan Tock Seng Hospital, Singapore
  • 2 Institute of Biodiversity Animal Health and Comparative Medicine, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
  • 3 Department of Biology, Faculty of Science, and Laboratory of Marine Biotechnology, Institute of Bioscience, Universiti Putra Malaysia, Selangor, Malaysia
  • 4 Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
  • 5 Centre for Tropical Medicine, Oxford University Clinical Research Unit, Hanoi, Vietnam
  • 6 Public Health England, Colindale, London, United Kingdom
  • 7 Environmental Health Institute, National Environment Agency, Singapore
  • 8 Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit, Mahosot Hospital, Vientiane, Lao People's Democratic Republic
  • 9 Department of Laboratory Medicine, Khoo Teck Puat Hospital, Singapore
  • 10 Oxford University Clinical Research Unit, Hanoi, Vietnam
  • 11 Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
  • 12 Department of Microbiology, Singapore General Hospital, Singapore
  • 13 Instituto de Microbiologia, Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
  • 14 Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
  • 15 Faculty of Fisheries, University of Agriculture and Forestry, Hue University, Hue City, Vietnam
  • 16 Thailand Ministry of Public Health (MOPH)-US Centers for Disease Control and Prevention Collaboration (TUC), Nonthaburi, Thailand
  • 17 Nakhon Phanom General Hospital, Nakhon Phanom Provincial Health Office, Nakhon Phanom, Thailand
  • 18 Department of Laboratory Medicine, Changi General Hospital, Singapore
  • 19 Molecular Biology Laboratory, Tan Tock Seng Hospital, Singapore
  • 20 National Hospital for Obstetrics & Gynaecology, Hanoi, Vietnam
  • 21 Nuffield Department of Clinical Medicine, Centre for Tropical Medicine and Global Health, University of Oxford, United Kingdom
  • 22 Key Laboratory of Tropical & Subtropical Fishery Resource Application & Cultivation, Ministry of Agriculture and Rural Affairs, Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, People's Republic of China
PLoS Negl Trop Dis, 2019 06;13(6):e0007421.
PMID: 31246981 DOI: 10.1371/journal.pntd.0007421

Abstract

BACKGROUND: In 2015, Singapore had the first and only reported foodborne outbreak of invasive disease caused by the group B Streptococcus (GBS; Streptococcus agalactiae). Disease, predominantly septic arthritis and meningitis, was associated with sequence type (ST)283, acquired from eating raw farmed freshwater fish. Although GBS sepsis is well-described in neonates and older adults with co-morbidities, this outbreak affected non-pregnant and younger adults with fewer co-morbidities, suggesting greater virulence. Before 2015 ST283 had only been reported from twenty humans in Hong Kong and two in France, and from one fish in Thailand. We hypothesised that ST283 was causing region-wide infection in Southeast Asia.

METHODOLOGY/PRINCIPAL FINDINGS: We performed a literature review, whole genome sequencing on 145 GBS isolates collected from six Southeast Asian countries, and phylogenetic analysis on 7,468 GBS sequences including 227 variants of ST283 from humans and animals. Although almost absent outside Asia, ST283 was found in all invasive Asian collections analysed, from 1995 to 2017. It accounted for 29/38 (76%) human isolates in Lao PDR, 102/139 (73%) in Thailand, 4/13 (31%) in Vietnam, and 167/739 (23%) in Singapore. ST283 and its variants were found in 62/62 (100%) tilapia from 14 outbreak sites in Malaysia and Vietnam, in seven fish species in Singapore markets, and a diseased frog in China.

CONCLUSIONS: GBS ST283 is widespread in Southeast Asia, where it accounts for a large proportion of bacteraemic GBS, and causes disease and economic loss in aquaculture. If human ST283 is fishborne, as in the Singapore outbreak, then GBS sepsis in Thailand and Lao PDR is predominantly a foodborne disease. However, whether transmission is from aquaculture to humans, or vice versa, or involves an unidentified reservoir remains unknown. Creation of cross-border collaborations in human and animal health are needed to complete the epidemiological picture.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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