Journal: Applied and Environmental Microbiology, vol. 69, p. 4431–4437, 2003
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Open Access: none
Two hundred strains of Listeria monocytogenes collected from food and the food industry were analyzed for susceptibility to the class IIa bacteriocins sakacin P, sakacin A, and pediocin PA-1 and the class I bacteriocin nisin. The individual 50% inhibitory concentrations (IC50) were determined in a microtiter assay and expressed in nanograms per milliliter. The IC50 of sakacin P ranged from 0.01 to 0.61 ng ml(-1). The corresponding values for pediocin PA-1, sakacin A, and nisin were 0.10 to 7.34, 0.16 to 44.2, and 2.2 to 781 ng ml(-1), respectively. The use of a large number of strains and the accuracy of the IC50 determination revealed patterns not previously described, and for the first time it was shown that the IC50 of sakacin P divided the L. monocytogenes strains into two distinct groups. Ten strains from each group were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of whole-cell proteins and amplified fragment length pollymorphism. The results from these studies essentially confirmed the grouping based on the IC50 of sakacin P. A high correlation was found between the IC50 of sakacin P and that of pediocin PA-1 for the 200 strains. Surprisingly, the correlation between the IC50 of the two class IIa bacteriocins sakacin A and sakacin P was lower than the correlation between the IC50 of sakacin A and the class I bacteriocin nisin.