Unveiling complete genome of streptococcus agalactiae from Malaysian aquaculture: a closer look at molecular characteristics and phylogenomic

Zainal Fithri, Helmi Husaini and Samsulrizal, Nurul Hidayah and Mansor, Nur Nazifah and Hamzah, Nurasyikin and Abu Halim, Noor Hanis and Mohammad Ridzuan, Mohd Syafiq and Abdullah, Azila and Abdul Rahim, Nur Amalin Sofea and Abdul Hamid, Azzmer Azzar (2026) Unveiling complete genome of streptococcus agalactiae from Malaysian aquaculture: a closer look at molecular characteristics and phylogenomic. Marine Biotechnology, 28 (97). pp. 1-11. ISSN 1436-2228 E-ISSN 1436-2236

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Abstract

Streptococcus agalactiae (Group B Streptococcus, GBS) is a significant pathogen in aquaculture worldwide and is responsible for high mortality in farmed fish. Despite its regional impact, complete genome data from Malaysian isolates remain scarce. In this study, we report the first complete genome of a Malaysian S. agalactiae isolate, SA2BKE, derived from infected tilapia. Using Oxford Nanopore long-read sequencing, we assembled a 2.03 Mb circular complete genome of S. agalactiae. The functional annotation revealed 1,970 protein-coding genes and 108 RNA genes. Several antimicrobial resistance genes, including tet(M), mreA, and mprF, are associated with resistance to tetracyclines, macrolides, and peptides, respectively. Notably, there are 15 virulence-associated proteins involved in cell wall/membrane/envelope biogenesis. Multilocus sequence typing (MLST) identified SA2BKE as sequence type ST283, which has the potential to infect both fish and humans. Comparative phylogenomic analysis revealed 215 global strains positioned SA2BKE within a clade of other ST283 isolates from Asia and South America, suggesting potential transregional transmission. Pan-genome analysis identified 555 core genes shared among the analysed genomes, highlighting substantial genomic diversity within the species. Additionally, 14 mobile genetic element-associated regions were detected in SA2BKE, indicating potential genome plasticity and horizontal gene transfer events. These findings expand the genomic reference data for S. agalactiae isolates from Malaysia, contributing to regional surveillance efforts across Southeast Asia and supporting integrated disease management strategies in aquaculture.

Item Type:	Article (Journal)
Uncontrolled Keywords:	Streptococcus agalactiae · Whole-genome sequencing (WGS) · Multilocus sequence typing (MLST), Phylogenomics
Subjects:	Q Science > QR Microbiology
Kulliyyahs/Centres/Divisions/Institutes (Can select more than one option. Press CONTROL button):	Kulliyyah of Science > Department of Plant Science
Depositing User:	Dr Nurul Hidayah Samsulrizal
Date Deposited:	22 Jul 2026 17:45
Last Update:	22 Jul 2026 17:45
Queue Number:	2026-07-Q4149
URI:	http://irep.iium.edu.my/id/eprint/130044

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