Affiliation:
1. Department of Animal Science
2. The Oklahoma Food and Agricultural Products Research and Technology Center, Oklahoma State University, Stillwater, Oklahoma 74078-6055
Abstract
ABSTRACT
Listeria monocytogenes
is a significant food-borne pathogen that is capable of adhering to and producing biofilms on processing equipment, making it difficult to eliminate from meat-processing environments and allowing potential contamination of ready-to-eat (RTE) products. We devised a fluorescence-based microplate method for screening isolates of
L. monocytogenes
for the ability to adhere to abiotic surfaces. Strains of
L. monocytogenes
were incubated for 2 days at 30°C in 96-well microplates, and the plates were washed in a plate washer. The retained cells were incubated for 15 min at 25°C with 5,6-carboxyfluorescein diacetate and washed again, and then the fluorescence was read with a plate reader. Several enzymatic treatments (protease, lipase, and cellulase) were effective in releasing adherent cells from the microplates, and this process was used for quantitation on microbiological media. Strongly adherent strains of
L. monocytogenes
were identified that had 15,000-fold-higher levels of fluorescence and 100,000-fold-higher plate counts in attachment assays than weakly adherent strains. Strongly adherent strains of
L. monocytogenes
adhered equally well to four different substrates (glass, plastic, rubber, and stainless steel); showed high-level attachment on microplates at 10, 20, 30, and 40°C; and showed significant differences from weakly adherent strains when examined by scanning electron microscopy. A greater incidence of strong adherence was observed for strains isolated from RTE meats than for those isolated from environmental surfaces. Analysis of surface adherence among
Listeria
isolates from processing environments may provide a better understanding of the molecular mechanisms involved in attachment and suggest solutions to eliminate them from food-processing environments.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
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