Antibacterial activity of eicosapentaenoic acid (EPA) against foodborne and food spoilage microorganisms

Eicosapentaenoic acid (EPA), a long-chain polyunsaturated fatty acid of ω-3 type was evaluated for its antimicrobial action against the range of foodborne and food spoilage pathogens, using agar disc diffusion assay in Luria broth (LB) media. The EPA exhibited antimicrobial activity against Bacillus subtilis ATCC 6633, Listeria monocytogenes ATCC 19166, Staphylococcus aureus ATCC 6538, S. aureus KCTC 1916 and Pseudomonas aeruginosa KCTC 2004. The minimum inhibitory concentrations (MICs) of the EPA against the tested bacterial strains were found in the range of 500-1350 μg/ml using broth dilution method. EPA reduced the viability of S. aureus at 250, 125 and 62.5 μg/ml after 15 min exposure and a steep decline in colony forming units (CFUs) was observed at 125 μg/ml after 30 min exposure, while similar reduction in CFU rate was exhibited by EPA when treated with 62.5 μg/ml after 180 min. EPA also reduced the CFU numbers of P. aeruginosa at all the concentrations used in this study after 15 min exposure. On the other hand, scanning electron microscopy (SEM) study of bacterial cells clearly exhibited the antibacterial effect of EPA as evidenced by the damages found in the outer membrane of the cells when treated with EPA. The results demonstrated that EPA exerted significant bactericidal and bacteriostatic effects against both P. aeruginosa and S. aureus.