Antibacterial activity and mechanism of a crab-derived i-type lysozyme against multidrug-resistant Vibrio alginolyticus.

The emergence and rapid spread of multidrug-resistant bacteria in aquaculture environments threatens the healthy development of the aquaculture industry and public health, driving demand for novel antimicrobial agents as alternatives to antibiotics. Marine animals harbor a diverse array of antimicrobial peptides, which exhibit great promise in addressing antibiotic resistance. In this work, the antimicrobial activity and mechanism of a crab-derived i-type lysozyme against multidrug-resistant Vibrio alginolyticus were investigated. The recombinant protein His-Ptlys-i (His-Ptlys-i) could bind to diverse bacteria and pathogen-associated molecular patterns (PAMPs), and displayed antibacterial and agglutinative activities against V. alginolyticus, V. parahaemolyticus, and Staphylococcus aureus. His-Ptlys-i exhibited synergistic/additive inhibitory effects against the multidrug-resistant V. alginolyticus DS016 when combined with tetracycline and fluoroquinolone antibiotics.‌ Transcriptome analysis indicated that His-Ptlys-i suppressed antibiotic resistance genes expression and inhibited multiple pathways, particularly branched-chain amino acid degradation, in V. alginolyticus DS016. Simultaneously, V. alginolyticus DS016 activates the expression of multiple ABC transporters involved in nutrient acquisition to counteract His-Ptlys-i-induced stress. His-Ptlys-i displayed promising antimicrobial activity against multidrug-resistant V. alginolyticus, indicating its potential as a candidate for novel agents combating multidrug-resistant bacteria and addressing the global challenge of antibiotic resistance.