Cytotoxicity and antimicrobial activity of synthetic peptides alone or in combination with conventional antimicrobials against fish pathogenic bacteria.
Assane. I M IM; Santos-Filho. N A NA; de Sousa. E L EL; de Arruda Brasil. M C O MCO; Cilli. E M EM; Pilarski. F F
Key Findings
- LL-37 showed no cytotoxicity to Nile tilapia red blood cells up to the tested concentrations
- LL-37 displayed antimicrobial activity against multiple fish pathogens (e.g., Aeromonas jandaei, Citrobacter freundii, Streptococcus agalactiae) with MIC ≤31.25 µg/ml
- LL-37 combined with florfenicol showed synergistic inhibition of C. freundii (fractional inhibitory concentration index = 0.50)
Practical Outcomes
- LL-37 and similar synthetic peptides appear safe for fish cells and effective against several fish bacterial infections, especially when paired with certain antibiotics, suggesting they could help reduce antibiotic use in aquaculture. For the biohacker community, the findings are interesting for understanding peptide safety but have limited direct relevance to human health protocols.
Summary
Scientists tested synthetic versions of the human peptide LL-37 (and other similar peptides) on fish blood cells and a range of bacteria that cause disease in fish. They found LL-37 isn’t toxic to the fish cells at the doses tested and can kill several fish pathogens, and it works even better when combined with certain antibiotics. This points to a way to treat fish infections with fewer traditional antibiotics, but it doesn’t give direct tips for personal health or longevity hacks.
Abstract
This study aimed to evaluate the in vitro cytotoxicity and efficacy of synthetic host defence peptides (HDPs), alone or in combination with florfenicol (FFC), oxytetracycline (OTC) or thiamphenicol (TAP), against different pathogenic bacteria isolated from diseased fish. Solid-phase synthesis, purification and characterization of several HDPs were performed manually, using the fluorenylmethyloxycarbonyl protecting group in different resins and via high-performance liquid chromatography-mass spectrometry, respectively. The in vitro cytotoxicity and antimicrobial activity of HDPs, FFC, OTC and TAP against Nile tilapia red blood cells (RBCs) and relevant fish pathogenic bacteria (Aeromonas, Citrobacter, Edwardsiella, Streptococcus, Lactococcus and Vibrio) was determined using the haemolysis assay and broth microdilution method, respectively. The checkerboard assay was used to evaluate the synergy between the most active HDPs and other antimicrobials against the tested strains. MUC 7 12-mer, FFC, OTC and TAP were not cytotoxic to Nile tilapia RBCs, in all tested concentrations. LL-37, (p-BthTX-I)<sub>2</sub> and Hylin-a1 were not cytotoxic at concentrations up to 78·13, 19·53 and 9·77 μg ml<sup>-1</sup> , respectively. HDPs demonstrated potent antimicrobial activity (minimum inhibitory concentration ≤31·25 µg ml<sup>-1</sup> ) against Aeromonas jandaei (KR-12-a5), Citrobacter freundii (Kr-12-a5; (p-BthTX-I)<sub>2</sub> ; LL-37; and Hylin a1), Streptococcus agalactiae (Hylin a1; (p-BthTX-I)<sub>2</sub> and LL-37), Lactococcus garviae (Hylin a1), and Vibrio fluvialis (KR-12-a5). The combinations of (p-BthTX-I)<sub>2</sub> with TAP and LL-37 with FFC showed synergistic activity against C. freundii (fractional inhibitory concentration index of 0·25 and 0·50, respectively). Synthetic HDPs have the potential as a good treatment option for bacterial diseases in aquaculture. The in vivo effectiveness of synthetic HDPs such as KR-12-a5; LL-37; (p-BthTX-I)<sub>2</sub> and Hylin a1 can be tested alone or in combination with conventional antimicrobials as a treatment option to reduce the use of antimicrobials in aquaculture.
Study Information
pubmed
2021
2021-03-29T00:00:00.000Z
10.1111/jam.15080
14
91