Synthetic Antimicrobial Peptide Polybia MP-1 (Mastoparan) Inhibits Growth of Antibiotic Resistant Pseudomonas aeruginosa Isolates From Mastitic Cow Milk

Antimicrobial peptides (AMPs) offer a potent and effective alternative for treatment of antibiotic resistant microbes. Mastoparans or mastoparan like peptides are the most abundant peptides reported in vespid/social wasp venoms with potent antimicrobial activity. Polybia MP-1 is an amphipathic tetradecapeptide isolated from the venom of the vespid wasp Polybia paulista with potent antimicrobial activity and high selectivity for bacterial membranes. In the present study, the antimicrobial activity of Polybia MP-1 was evaluated against antibiotic resistant Pseudomonas aeruginosa isolated from mastitic cow milk samples. The isolates (n = 20) were obtained from mastitic milk samples and screened for sensitivity to antibiotics (Amikacin, Ciprofloxacin, Gentamycin, Imipenem, Ceftazidime, Colistin, Ceftriaxone and Aztreonam) by disc diffusion assay. The isolates were also characterized for the presence of different genes (n = 27) by polymerase chain reaction (PCR). These genes encoded for virulence factors, biofilm formation and antibiotic resistance. A correlation study was carried out to establish the significance of presence of antibiotic resistant genes i.e. blaTEM, blaCTX−M, blaSHV and blaOXA and resistance against different antibiotics for the bacterial isolates. Out of twenty, 7 isolates were found to be multiple drug resistant (MDR). We determined the minimum inhibitory concentration (MIC) of synthetic peptide, Polybia MP-1 against P. aeruginosa (ATCC 27853) and it was found to be 75 µM (124 µg/mL) whereas its minimum bactericidal concentration (MBC) was found to be 150 µM (2 X MIC). The Polybia MP-1 was able to effectively inhibit the growth of 5 out of 7 (71 %) MDR isolates at 6 X MIC (450 µM). The Polybia MP-1 was highly membrane selective and hence showed very low to moderate haemolytic activity against cattle, buffalo and goat red blood cells (RBCs). It further showed potent anti-biofilm activity against P. aeruginosa ATCC 27853 at 8 X MIC (600 µM). Thus, synthetic Polybia MP-1 has potent antimicrobial activity against antibiotic resistant P. aeruginosa and can be explored as an alternative to antibiotics for the management of disease conditions like mastitis in cattle.