Inhibitory Effect of Nisin against Staphylococcus aureus and Escherichia coli O157:H7

Abstract

Nisin was shown to inhibit the growth of Staphylococcus aureus and Escherichia coli O157:H7. Nisin was incorporated into the plates of S. aureus at 0, 1.3, 2.5, 5.0, 7.5, and 10 IU/ml and incorporated into the plates of E. coli O157:H7 at 0, 100, 200, 300, and 400 IU/ml. Gradients of pH (6.7 and 4.7) were used for the plates, which were incubated at 37 C. Organisms were inoculated into the plates with the concentration of 6 and 4 log10 CFU/ml. The plates were incubated for 48 hrs and the colonies were enumerated at 0, 3, 6, 9, 12, 24, and 48 hr, respectively. The growth of S. aureus was effectively inhibited at the concentration of 5.0 IU/ml nisin in all cases, while the concentration of 2.5 IU/ml nisin effectively inhibited the growth of S. aureus inoculated 4 log10 CFU/ml at pH 6.7. The concentration of 300 IU/ml nisin effectively inhibited the growth of E. coli O157:H7 inoculated 6 and 4 log10 CFU/ml at pH 4.7.