Listeria monocytogenes is a microscopic organism that causes foodborne illnesses that are often fatal. Recently published research shows that it can multiply up to seven times on food contact surfaces in manufacturing plants when it forms biofilms.
Biofilms grow from various substances such as bacteria, fungi and algae. They attach to surfaces in moist environments and form a protective layer of mucous, sweet substances.
In an experiment with biofilms and Listeria monocytogenes, the researchers found that after cycles of colonizing a plastic surface, forming biofilms, spreading, and attaching to new surfaces, evolved variant (EV) strains were isolated that produced seven times more biofilm than their corresponding ancestral (AN) strains. The study was published in the journal Science Direct.
Biofilms are very difficult to remove, and standard cleaning and disinfection processes have proven inadequate. This, combined with the fact that Listeria itself is very difficult to eradicate, makes Listeria biofilms especially dangerous. Bacteria and biofilms can attach to a variety of food contact surfaces, including plastic, stainless steel, other metals, and glass.
“This structure can then develop into a complex surface-attached architecture, and individual cells or cell aggregates can subsequently disperse from the resulting biofilm and colonize other surfaces,” the researchers said.
“It is widely recognized that bacteria in natural and industrial environments are primarily present in surface-associated communities, which represents a key strategy for colonization and survival in various environments.”
The researchers reported that biofilms promote microbial persistence in hostile and stressful environments such as the food industry because they protect embedded bacteria from drying out, antimicrobials, and disinfectants. Additionally, Listeria monocytogenes is known to form multispecies biofilms in food production environments, which may also affect its survival during surface disinfection.
According to the researchers, the difference in biofilm formation between the ancestral (AN) strains and the evolved variants (EV) occurs very quickly—within two hours of incubation.
