The U.S. Department of Agriculture has awarded a $605,000 grant to microbiologists in Penn State’s College of Agricultural Sciences to study how microbial biofilms protect Listeria monocytogenes.

“Microorganisms enclosed in a biofilm produce slimy substances that protect them from the antimicrobial activity of sanitizing chemicals by slowing down their penetration into the core of a biofilm,” Jasna Kovac, Lester Earl and Veronica Casida Career Development Professor of Food Safety and Assistant Professor of Food Science said.

“Biofilm formation can therefore result in reduced efficacy of antimicrobial sanitizers used to inactivate Listeria. This project will investigate the interactions between microorganisms found in fruit-packing environments and Listeria monocytogenes.”

Along with Kovac, Luke LaBorde, professor of Food Science, will use the funding from USDA’s National Institute of Food and Agriculture to conduct research on the interactions between microorganisms found in fruit-packing environments and Listeria monocytogenes.

According to LaBorde, because the role of the food-processing environment microbiota on Listeria monocytogenes survival within a biofilm under sanitizer pressure is poorly understood, the researchers will evaluate the ability of the most relevant environmental microbiota found in produce-packing environments to form single- and multi-species biofilms with Listeria monocytogenes.

As part of this study, Penn State graduate student Laura Rolon is working on four project objectives funded by this grant: isolate environmental microbiota and determine their resistance to sanitizers; characterize genomes of environmental isolates using whole-genome sequencing; characterize biofilm formation ability of bacterial families and Listeria monocytogenes in single- and in multi-family assemblages; and characterize the effect of microbial assemblages on the tolerance of Listeria monocytogenes to sanitizer treatment.

According to Rolan, Listeria monocytogenes is especially dangerous because the pathogen can survive, grow and persist at low temperatures in produce-processing facilities.

“Biofilms represent a physical barrier that reduces the effective diffusion and antimicrobial action of sanitizers and is hypothesized to increase L. monocytogenes’ tolerance to sanitizers used in food processing facilities,” she said.

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