Rethinking Group B Streptococcus: The Rise of Sequence Type 283 as a Foodborne Zoonotic Pathogen.

Streptococcus agalactiae, or Group B Streptococcus (GBS) sequence type 283 (ST283), has emerged as a foodborne zoonotic pathogen of increasing concern, particularly in Southeast Asia. It gained global recognition following a major outbreak in Singapore in 2015, where it caused severe invasive infections such as meningitis, septic arthritis, and bacteremia, even in previously healthy adults, and was linked to the consumption of raw freshwater fish. Since then, outbreaks and sporadic cases of ST283 have been reported in China and Southeast Asia, with incidental reports in a growing number of countries. While ingestion of contaminated raw freshwater fish remains the primary transmission pathway, recent findings have identified a strong link between infections and handling of freshwater fish, as well as the possibility of contamination due to human shedding and human-to-human transmission. Although ST283 remains largely susceptible to first-line antibiotics, delayed recognition in resource-limited settings hampers timely response. This review synthesizes current knowledge on ST283 as an emerging zoonotic and foodborne threat, summarizing its epidemiology, transmission, pathogenesis, diagnosis, and treatment, while highlighting research gaps and the need for strengthened surveillance and preventive measures.