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Appl. Environ. Microbiol., Mar 1995, 992-997, Vol 61, No. 3
CK Bower, J McGuire and MA Daeschel
Nisin is an antimicrobial peptide proven to be an effective inhibitor of
gram-positive bacteria. It is known that nisin can adsorb to various
surfaces and still retain much of its original activity (M. A. Daeschel, J.
McGuire, and H. Al-Makhlafi, J. Food Prot. 55:731-735, 1992). In this
study, nisin films were allowed to form on silanized silica surfaces and
then exposed to medium containing Listeria monocytogenes. Representative
areas were selected from each surface, and images of resident listeriae
were obtained at 4-h intervals for 12 h. During this time, cells on
surfaces that had been in contact with a high concentration of nisin (1.0
mg/ml) exhibited no signs of growth and many displayed evidence of cellular
deterioration. Surfaces treated with a lower concentration of nisin (0.1
mg/ml) had a smaller degree of inhibition. In contrast, both protein-free
surfaces and those with films of heat-inactivated nisin allowed attached L.
monocytogenes cells to grow and reproduce. These studies, when repeated
with a nisin- resistant strain of L. monocytogenes, resulted in no
inhibition of growth on surfaces with adsorbed nisin. The bactericidal
effect of adsorbed nisin was also studied with iodonitrotetrazolium violet,
a tetrazolium salt, which is reduced to a red formazan crystal by viable
bacteria. Crystals were visible in 95% of the cells adhered to control
surfaces but were present in less than 20% of the cells on surfaces with
adsorbed nisin. These data indicate that adsorbed nisin may have potential
for use as a food grade antimicrobial agent on food contact surfaces.
Copyright © 1995, American Society for Microbiology
Suppression of Listeria monocytogenes colonization following adsorption of nisin onto silica surfaces
Department of Food Science and Technology, Oregon State University, Corvallis 97331.
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