C.A. Murdock, J. Cleveland, K.R. Matthews and M.L. Chikindas
Rutgers, The State University of New Jersey, New Jersey, USAVolume 44 Issue 3 Page 255 - March 2007
Aims: The goal of this study was to determine whether nisin and lactoferrin would act synergistically to inhibit the growth of Listeria monocytogenes and Escherichia coli O157:H7.
Methods and Results: Lactoferrin and nisin separately or in combination were suspended in peptone yeast glucose broth and following inoculation with L. monocytogenes or E. coli O157:H7 growth inhibition of each pathogen was determined. At 1000 μg ml-1 lactoferrin L. monocytogenes was effectively inhibited. However, E. coli O157:H7 initially was inhibited and then grew to cell density similar to the control. A combination of 500 μg ml-1 of lactoferrin and 250 IU ml-1 of nisin effectively inhibited the growth of E. coli O157:H7, whereas, 250 μg ml-1 of lactoferrin and 10 IU ml-1 of nisin were inhibitory to L. monocytogenes.
Conclusions: The results suggest that lactoferrin and nisin act synergistically to inhibit the growth of L. monocytogenes and E. coli O157:H7.
Significance and Impact of the Study: Natural preservatives that are active against gram-positive and gram-negative pathogens are desirable to the food industry and consumers. This study demonstrates that lactoferrin and nisin work synergistically reducing the levels required independently inhibiting growth of two major foodborne pathogens. Previous reported results indicated a low level of antimicrobial activity; however, this work was not performed in low divalent cation concentration media. It has been suggested that nondivalent cation-limiting medium such as trypticase soy broth (TSB), can reduce or completely eliminate the inhibitory activity. Further knowledge of these interactions can increase the understanding of the antimicrobial activity of lactoferrin. This should make the use of these compounds by industry more attractive.