Title : TRUNCATED PGHs AS ALTERNATIVE ANTIMICROBIALS FOR STREPTOCOCCUS INIAE INFECTIONS IN FISH FISH
Abstract:
Streptococcus iniae is a gram-positive bacterial pathogen that causes streptococcosis in fish, leading to high mortality and economic losses in aquaculture. With antibiotic resistance becoming a critical concern, alternative strategies are urgently needed. Peptidoglycan hydrolases (PGHs) have emerged as promising antibacterial agents due to their ability to degrade bacterial cell walls. Previous studies from our lab has shown that the truncated form of a PGH LambdaSa2 showed higher antibacterial activity in-vitro than the full length. However, truncated-PGH alone can only target extracellular bacteria and is ineffective against intracellular pathogens during systemic infection. To address intracellular limitations, truncated PGH will be fused with 11 different protein transduction domains (PGH-PTDs) separately. PTDs are short peptide sequences that facilitate transport across host cell membranes, enabling intracellular delivery and activity. OmB cells isolated from tilapia brain will be infected with six S. iniae strains at a multiplicity of infection of 1:100. Intracellular killing will be evaluated following treatment with 10 µg/ml of each truncated-PGH and PGH-PTD construct. Based on prior findings, truncated PGH-PTDs are expected to significantly reduce intracellular bacterial loads compared with truncated PGHs alone in a strain-dependent manner.
