Invasive Group B Streptococcus Infection associated with Sequence Type 283 (ST283)

Causative agent

Group B Streptococcus (GBS), Streptococcus agalactiae, is an encapsulated gram-positive non-motile coccus bacterium. It is widely distributed among diverse species including humans, mammalian animals, amphibians, reptiles and fish.

A specific strain of GBS, the sequence type 283 (ST283), was among the more virulent strains of GBS which can cause invasive diseases in otherwise healthy adults or people with relatively few underlying comorbidities.

Presence of ST283 was reported in freshwater fish (in particular farmed fish) in Southeast Asian countries. In 2015, ST283 caused a major invasive foodborne outbreak associated with consumption of raw freshwater fish affecting at least 146 people in Singapore, and this outbreak has led to a ban in ready-to-eat raw fish dish provision in Singapore since December 2015. Thereafter, invasive GBS ST283 disease has also been reported in Singapore and other Asian countries/areas including Mainland China, Hong Kong, Laos, Thailand, Vietnam and Myanmar, while very few cases have been reported beyond these areas.

Clinical presentation

Invasive GBS ST283 infection may present as sepsis, meningitis, septic arthritis, infective endocarditis and even death.

Mode of transmission

Although literature indicated an association between ST283 and consumption of raw or undercooked freshwater fish or improper handling of freshwater fish, the mode of transmission of ST283 are mostly unclear.

Risk factors

In general, the elderlies, pregnant women, infants and young children and immunocompromised people may be at higher risk of infection.

Some overseas studies suggest that the proliferation of GBS ST283 may be influenced by environmental conditions such as elevated temperature. GBS isolates from freshwater fish have been observed to exhibit optimal growth at 30°C, and ST283 cases are predominantly reported from Southeast Asia, where the climate is hot.

Management

Hospitalization is often required for patients infected with invasive GBS ST283, infection can be treated with antibiotics.

Prevention

To prevent invasive GBS ST283 infection, members of the public are reminded to maintain personal, food and environmental hygiene, keep their hands clean and practise good wound care at all times, especially:

• To minimise the infection risks, workers of aquatic products or restaurants must wear gloves when handling aquatic products and avoid direct contact with aquatic products or dirty water with bare hands;
• When buying aquatic products, the public must avoid direct contact with the aquatic products or use any towel provided by the stalls. They should wash hands with liquid soap and water as soon as possible if having contact with aquatic products which are not fully cooked. When handling aquatic products at home, the public should also wear gloves and wash hands thoroughly afterwards;
• Members of the public must not eat any freshwater fish sashimi, raw or undercooked freshwater aquatic products. When consuming hot pot food or congee items which consist of aquatic products, they should ensure that the food is thoroughly cooked in which the centre of the food should reach a temperature of at least 75 degrees Celsius so as to destroy pathogens; and
• People must not touch aquatic products directly whenever there is a wound on their hands. If a wound is sustained during handling aquatic products, the wound must be cleaned immediately and properly covered with waterproof adhesive dressings. Individuals should seek medical advice promptly when wound infection is suspected.

Other languages