Submitted to: Peptides
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/18/2022
Publication Date: 9/21/2022
Citation: Line, J.E., Seal, B., Garrish, J.K. 2022. Selected antimicrobial peptides inhibit in vitro growth of Campylobacter spp.. Peptides. 688-700. https://doi.org/10.3390/applmicrobiol2040053.
Interpretive Summary: Antimicrobial peptides (AMP) are small proteins which have been found in most every class of living organism where they have evolved as a host defense mechanism against invading microorganisms. A growing number of AMP are being discovered and synthetic new ones are being designed thanks to tremendous research efforts in response to the dramatic and continued evolution of antibacterial-resistant strains of bacteria and the resulting international crisis in health care. While it is reasonable to expect that some of the AMP that have been discovered or designed to kill other bacteria might also inhibit Campylobacter spp., there have been very few reports in the literature describing effects of AMP on these specific pathogens, perhaps due to the relative difficulty of culturing campylobacters under microaerobic conditions necessary for its growth. Campylobacter is one of the most important human pathogens worldwide, being a major cause of acute human diarrheal illness in the developed world. Commercial broiler chickens serve as a major reservoir for Campylobacter. We selected and evaluated a set of 11 unique chemically synthesized and commercially available AMP for ability to inhibit growth of C. jejuni and other pathogenic bacteria. Six of the tested AMP were able to kill campylobacters and three (C12K-2ß12, RL-37 and Cec-Mag) show promise for future development and testing in broiler chickens. By providing novel alternatives to antibiotic usage in poultry, the overall impact of our long-term research goals will be a reduction in bacterial pathogens associated with chickens and safer products for human consumption. Scientists in industry, government and academia will find this information useful.
Technical Abstract: A set of 11 unique chemically synthesized and commercially available antimicrobial peptides (AMP) were evaluated for ability to inhibit growth of two strains of Campylobacter jejuni. Six of the AMP we tested produced zones of inhibition on lawns of C. jejuni. These AMP included: NRC-13, a variant of Pleurocidin isolated from the American plaice-flounder; RL-37, a 37-residue AMP of the cathelicidin family which is expressed in bone marrow of the rhesus monkey; Temporin L, from the frog, Rana temporaria; a potent hybrid AMP (Cec-Mag) composed of residues 1-8 of Cecropin A (from the Cecropia moth) fused to residues 1-12 of Magainin 2 (from the African clawed frog, Xenopus Laevis); Dermaseptin from the skin of frogs of the genus Phyllomedusa; and the synthetic C12K-2ß12. Three AMP were chosen for further investigation on the basis of initial anti-Campylobacter activity, water solubility and reported reduced cytotoxicity to mammalian cells: Cec-Mag, RL-37 and C12K-2ß12 were tested for ability to produce zones of inhibition in spot on lawn assays against 24 different bacteria including C. jejuni, C. coli and C. lari as well as two strains of Salmonella, Clostridium perfringens, Listeria monocytogenes, Lactobacillus, and E. coli O157:H7. In addition, a modification of the NCCLS M26A and Hancock assays were utilized to determine minimum inhibitory concentrations (MIC) for these AMP against 15 isolates of Campylobacter representing the three most common pathogenic strains. The selected AMP produced obvious zones of inhibition against growth of C. jejuni, C. coli and C. lari isolates in the classic spot-on-lawn plating assay. The selected AMP also inhibited growth of pathogenic Salmonella, C. perfringens, Listeria and E. coli O157:H7 isolates. MIC for Campylobacters were approximately 3.1 µg/ml for the AMP RL-37 and C12K-2ß12. MIC were slightly higher for the Cec-Mag AMP in the range of 12.5 to 100 µg/ml.