Potential of antimicrobial peptides against bacterial pathogens causing bovine mastitis

Abstract

Bovine mastitis is a common disease in dairy cows. The majority causes of bovine mastitis disease is an intramammary bacterial infection via the teat orifice. In general, antibiotics are used for bovine mastitis treatment, its inappropriate usage leads to antibiotic-resistance problem and residue in meat and dairy products. One of the alternative ways against pathogen to reduce antibiotic usage is antimicrobial peptides which are innate immune of life. Three cationic peptides as Pm11, Pep64, and L10 peptides were evaluated for an antimicrobial activity to gram-positive and gram-negative bacteria. Pm11 has shown the best potent antimicrobial activity with minimum bactericidal concentration (MBC) range from 2.5-10.0 µM and IC50 0.32-2.07 µM. Time kill kinetics of Pm11 peptide against bovine mastitis pathogens were ascertained, Pm11 is exhibited strong activity to completely killing Streptococcus agalactiae (SCM1084), Streptococcus uberis (SCM1310) within 1 hour and completely killing Staphylococcus aureus (CM967), Escherichia coli (SCM1249) within 4 hour. However, Pm11 peptide at 10.0 µM could not be completely killing Klebsiella spp. (SCM1282), even though 3 log10 CFU/ml of Klebsiella spp. (SCM1282) was decreased within 2 h, but it was returning to grow up within 12 h. Visual observation under the scanning electron microscope of Pm11 peptide attacked to the pathogens shown the distinct morphological changes. The cytotoxicity assay confirmed that Pm11 peptide at the concentration 0 to 160 µM had low hemolytic activity to sheep red blood cells. Nonetheless, the antimicrobial activity of Pm11 peptide was reduced in UHT milk.