Effect of antimicrobial proteins from porcine leukocytes on Staphylococcus aureus and Escherichia coli in comminuted meats

Study is aimed to elucidate the effect of porcine leukocyte antimicrobial protein on the proliferation of Staphylococcus aureus and Escherichia coli inoculated in ground meats. The antimicrobial proteins were isolated from porcine blood using 0.2 M sodium acetate extraction and cation-exchange column chromatography. Antimicrobial protein preparation consisted predominantly of 7.5 and 6 kDa molecules. Immunoblotting demonstrated that the 7.5 kDa molecule displayed defensin immuno-reactivity, a unique blood granulocyte antimicrobial protein. Both 7.5 and 6 kDa molecules could decrease apparent proliferation of test cultures. Sterilization (121 °C, 30 min) and proteolytic enzymes (pepsin, trypsin, and chymotrypsin) could significantly decrease bacteriocidal activities of antimicrobial protein preparation. Furthermore, antimicrobial protein preparation enhanced exposure of intercellular nucleotide of test cultures. Antimicrobial protein preparation inhibition of S. aureus and E. coli growth was concentration and time dependence. Adding 160 μg/g antimicrobial protein preparation to ground ham meat and sausage mince could significantly (P<0.05) hurdle viable colony formation of test cultures at 6 and 12 h, respectively. Taken together, porcine leukocyte antimicrobial protein preparation has potential to inhibit proliferation of S. aureus and E. coli inoculated in ground meat via induction of bacterolysis, suggesting this antimicrobial protein preparation be an alternative natural bio-preservation source for ground meat products.