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Invasive streptococcal B infections and fish …

In Hong Kong the Center for Health Protection (CHP) of the Ministry of Health (DH) said on October 18, 2021 that it was following the epidemiological investigation into an upsurge in cases of invasive group B streptococcal infections (GBS). The CHP has received reports from the hospital administration that in September and October (as of October 10) 58 and 21 patients respectively were hospitalized with invasive GBS infections, whereas in the previous three years between 9 to 26 monthly cases. The 79 cases involve 42 men and 37 women aged between one month and 96 years old. They mainly presented with sepsis, meningitis, septic arthritis or abscesses/cellulitis.

Investigations show that some of the patients handled freshwater fish before the onset of infection. Some of them said they had injured their hands during these manipulations.

Laboratory analyzes showed that at least 32 cases involved GBS serotype III sequence 283 (ST-283), whose genetic sequence was identical to those of GBS isolated from fish and environmental samples taken from markets frequented by some of the sick. The CHP considers that handling fresh freshwater fish with hand injuries or eating undercooked freshwater fish may be the source of the infection.

Reminders on Group B Streptococcus ST-283 :

Streptococcus agalactiae (group B streptococcus, GBS) is a bacterium frequently harbored in the intestinal and genitourinary tracts in humans. It is responsible for severe neonatal infections and various invasive infections (urinary tract infections, sepsis, pneumonia, endocarditis, joint infections, etc.). In adults, the immunocompromised and the elderly are particularly affected. GBS is also a veterinary pathogen. It is responsible for invasive infections in terrestrial mammals such as cattle, dogs and cats and aquatic or semi-aquatic species, including farmed fish.

GBS serotype III and type sequence ST-283 is a particular strain considered emerging in Southeast Asia. In 2015, in Singapore, a large outbreak of severe invasive GBS ST-283 infections was reported in adults. His analysis showed that it was epidemiologically linked to the consumption of raw freshwater fish. The seriousness of the infections observed (meningitis, septic arthritis) including in young adults with no particular history led to the consideration of this strain as “hypervirulent”. No other outbreaks of SGP ST-283 have been reported to date. Prior to 2015, GBS ST-283 had been identified as responsible for serious infections in Hong Kong and France (2 cases). However, several retrospective studies conducted subsequently showed that SGB ST-283 emerged in Southeast Asia (Hong-Kong, Laos, China, Vietnam, Thailand) in the 1990s. In freshwater fish, this clone has been identified in many South East Asian countries (Singapore, Thailand, Viet Nam, China, Malaysia). It was also isolated in Brazil, the aquaculture sector of this country having been contaminated during imports of live fish from Singapore.

Group B Streptococci survive well when frozen at -20°C. Faced with the popularity of preparations based on raw fish such as ceviche or namasu in addition to traditional sushi and sashimi, an increase in the frequency of exposure of European consumers to GBS cannot be ruled out.

To prevent infection with this strain of GBS, it is necessary to observe personal, food and environmental hygiene, keep hands clean and practice good wound care at all times. In particular, it is recommended to:

  • Wear gloves when handling fresh freshwater fish or seafood and avoid wounds coming into contact with raw freshwater fish or seafood;
  • Avoid eating raw freshwater fish or seafood;
  • Avoid skin contact with dirty water when visiting a wet market and maintain good hand hygiene.

Source : Center for Health Protection, Department of Health, The government of the Hong Kong special administrative region.

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