Efficacy of purified antimicrobial peptides from lactic acid bacteria against bovine mastitis pathogens

A study was carried out to assess the efficacy of purified antimicrobial peptides of lactic acid bacteria (LAB), isolated from partially decayed samples of food items, against selected clinical isolates of mastitis bacterial pathogens, viz., Escherichia coli (E.coli), Staphylococcus aureus (S.aureus) and Streptococcus agalactiae (S.agalactiae). The crude culture extracts (CCE) from LAB isolates were concentrated and purified by salting out method followed by dialysis. Partially purified peptides (Tp-5 CRp-2 CRp-3) from three LAB isolated from tomato and carrot showed a significantly higher inhibitory spectrum, with zone of inhibition ranging from 11.66±0.33 to 12.66±0.33 mm diameter against different test pathogens. The inhibitory efficiency of all the three peptides was found to be significantly superior to the peptides from reference strain Lactococcus lactis NCIM-2114. Minimum inhibitory concentration (MIC) of the purified peptide samples ranged between 0.79±0.09 to 1.11±0.09 µg/ml against different test pathogens. The activity of peptides was completely lost after treatment with protease, thereby confining their protein character.