Biofilms help Shiga-toxin producing E. coli survive and persist

Forming biofilms may be a survival strategy of Shiga toxin-producing Escherichia coli to enable it to persist in the environment and the food industry.


Here, we evaluate and characterize the biofilm-forming ability of 39 isolates of Shiga toxin-producing Escherichia coli isolates recovered from human infection and belonging to seropathotypes A, B, or C.

The presence and/or production of biofilm factors such as curli, cellulose, autotransporter, and fimbriae were investigated. The polymeric matrix of these biofilms was analyzed by confocal microscopy and by enzymatic digestion. Cell viability and matrix integrity were examined after sanitizer treatments. Isolates of the seropathotype A (O157:H7 and O157:NM), which have the highest relative incidence of human infection, had a greater ability to form biofilms than isolates of seropathotype B or C. Seropathotype A isolates were unique in their ability to produce cellulose and poly-N-acetylglucosamine.

The integrity of the biofilms was dependent on proteins. Two autotransporter genes, ehaB and espP, and two fimbrial genes, z1538 and lpf2, were identified as potential genetic determinants for biofilm formation. Interestingly, the ability of several isolates from seropathotype A to form biofilms was associated with their ability to agglutinate yeast in a mannose-independent manner. We consider this an unidentified biofilm-associated factor produced by those isolates.

Treatment with sanitizers reduced the viability of Shiga toxin-producing Escherichia coli but did not completely remove the biofilm matrix. Overall, our data indicate that biofilm formation could contribute to the persistence of Shiga toxin-producing Escherichia coli and specifically seropathotype A isolates in the environment.

Biofilm-forming abilities of Shiga toxin-producing Escherichia coli isolates associated with human infections

Applied and Environmental Microbiology Vol. 82. No. 5.

Slimer in the Kitchen: Salmonella biofilm means more work when using disinfectants

Who you gonna call? GHOSTBUSTERS! Or – a professional cleaning company.

My favorite character from the Ghostbusters series is Slimer, mainly because he always seems to get away with causing chaos around him. As a kid, I didn’t think too much about his puke-green color or possible germs that he might be carrying. However, after reading an article from the Norwegian School of Veterinary Medicine about Salmonella biofilms, I’ve come to the conclusion that Slimer was probably a giant lump of Salmonella coated in a protective biofilm.  Bacteria have multiple forms of defense, and some bacteria are able to produce a biofilm, or a slimy outer covering, in order to protect itself from disinfectants and to ensure its survival in the environment.  Too bad the Ghostbusters guns didn’t have alcohol and Virkon in them, otherwise Slimer would be toast.
In her doctoral thesis, Lene Karine Vestby studied why it is so difficult to get rid of once they have managed to establish themselves in Norwegian feed and fish meal factories. She discovered that bacteria efficient at forming biofilm (bacteria coating) survived for longer in the factories than those that had a reduced ability to form this coating. The ability to survive in factories therefore appears to be connected with the ability to form a biofilm and it would seem that removing biofilm is a necessary step towards eradicating from the factories.
Vestby studied the effect of nine most frequently used disinfectants and found that their efficiency is substantially reduced of the Salmonella has managed to form a biofilm. The effect of the majority of the disinfectants was then no longer satisfactory, but a product containing 70% ethanol was the most efficient, followed by one called Virkon S. These results could improve the efficiency of the cleaning procedures used by processing plants in the animal feed industry, and also in the human food industry.
Of course it’s not just about finding the right tools, the tools must be properly used. Proper production methods should be in place to prevent the contamination of the feed. Processing and packaging facilities should follow a regular cleaning schedule with the appropriate disinfectants. These things all contribute to the culture of food safety. They should also keep Slimer out of the kitchen.