Work

Characterization of Streptococcus agalactiae 1a isolated from farmed Nile tilapia (Oreochromis niloticus) in North America, Central America, and Southeast Asia

Year: 2024

Type: article

Abstract: Streptococcosis caused by Streptococcus agalactiae 1a in Nile tilapia ( Oreochromis niloticus ) is a severe disease challenge for the global supply of tilapia. Currently, the extensive use of antibiotics is the primary curative tool used to minimize the impact of the disease. Vaccination is a prophylactic measure that has been shown to reduce antibiotic use in the aquaculture sector substantially. However, no commercially licensed vaccine against Streptococcus agalactiae 1a is currently available. This study aimed to investigate, through molecular and immunological methods, if Streptococcus agalactiae 1a isolates collected from North America (NAM), Central America (CAM), and Southeast Asia (SEA) were similarly suitable for the development of a potentially effective vaccine to serve the global tilapia farming industry. Our comparative data showed that the Streptococcus agalactiae 1a isolates from NAM, CAM and SEA had similar biochemical profiles, and genetic multi-locus sequence typing (MLST) analysis showed that the NAM and CAM isolates belonged to sequence type 7 (ST-7) and clonal complex 1, while isolates from SEA grouped into three sequence types (ST-1650, ST-500, and ST-7) and two distinct clonal complexes (CC1 and CC12). Isolates from NAM, CAM, and SEA displayed similar antigenic profiles determined by western blotting with polyclonal rabbit antisera, which was supported by in v ivo cross-protection studies, showing that fish immunized with vaccines based on SEA and CAM isolates with different genetic MLST profiles were highly protected against cross-challenge using the same bacterial strains for challenge. Overall, the data obtained from our investigations provide strong indications that Streptococcus agalactiae 1a distributed in NAM, CAM, and SEA are serologically uniform pathogens, and vaccines based on isolates of Streptococcus agalactiae 1a from these regions may be suited for vaccination of tilapia worldwide. • Streptococcus agalactiae 1a is a major pathogen in global tilapia farming. • The study compared isolates from North, Central America, and Southeast Asia. • Biochemical and MLST analysis showed genetic similarity among regional isolates. • Antisera cross-reacted with regional isolates, indicating serological uniformity. • Vaccines based on genetically different isolates provided cross-protection in tilapia.

Source: Fish & Shellfish Immunology

DOI: 10.1016/j.fsi.2024.109919

Authors: Kjetil Fyrand, Cheng Xu, Øystein Evensen

Institution: Norwegian University of Life Sciences

Language: English

Topic: Aquaculture disease management and microbiota

Subfield: Immunology

Field: Immunology and Microbiology

Domain: Life Sciences

SDGs: Zero hunger, Good health and well-being

Open Access status: hybrid

Estimated APC paid: $4,420