Cobiotex Biofilms

The prevention of toxic infections of dietary origin requises that foods to be free of certain microbes, particulier Salmonella typhimurium and S. enteritidis.
Animals destined for the food industrie are housed in conditions designed to ensure an excellent level of sanitation.
However, no matter how much care is taken, these farm buildings cannot completely exclude pests such as rodents, birds and insects, all of which are major sources of infection.
Animal feed is another possible source of infection, but the risk of contamination from this source is gradually decreasing, due to the precautions taken regarding the quality of the raw materals used.
Today, the contamination of feed is responsible for at least 30 % of all animal infections.
Most of the Salmonella bacteria present in animals originate from the reactivation of cells transmitted in an inactive and therefore indetectable form.
This stade is known as " bacterial stress " and enables the cell to survive in difficult conditions, which would otherwise lead to cell death.

BACTERIAL STRESS AND BIOFILM

Bacterial stress represents a major change in the physiological state of a cell in unfavourable conditions.
It involves a non-specific adaptation aimed at keeping the cell in a resting state for the duration of the unfavorable conditions.
This adaptation involves three key functions of the cell :

A stressed cell secretes " stress glycoproteins " which remain associated with the cell and act as a form of protection.
The cell is thus protected against external attack including the effects of disinfectants and antibiotics.
A stressed cell loses its ability to divide, making it undetectable by traditional detection methods.
Special techniques such as molecular biology and epifluorescence microscopy are required to detect these cells which are described as viable, non-culturable (VNC) cells.
The virulence of the cell increases during this period of inactivity in which the metabolic rate is low.
This enables the cell to develop rapidly when the stress is released, despite the small number of cells present, and to release highly active toxins that promote its growth at the expense of the organisms susceptible to these toxins.

Various conditions may place bacteria in a state of stress.
Contact with and attachment to smooth surfaces results in such a state of stress, leading to the formation of a bacterial covering all over such surfaces.
Once in contact with the surface, the bacteria organise themselves into a highly resistant bacterial coating called a " biofilm ", involving electrostatic adhesion and protection by secreted glycoproteins.
Recent studies have shown that biofilms are organised structures that enable the stressed cells to survive and to reactivate when favourable conditions return.
The structure of the biofilm, involving adhesion and a glycoprotein layer, protects the bacteria in a stressed state within the biofilm against detergents and disinfectants.

Thus, all the surfaces develop biofilms.
The concentration of animals in the building affects the development of biofilms : large numbers of animals result in a high concentration of bacteria in the building which in turn results in heavily loaded biofilms.

REACTIVATION OF CELLULAR ACTIVITY IN STRESSED CELLS

It is possible to experimentally recreate the conditions that induce a state of stress, but we cannot do the reverse because the factors promoting a release from stress and reactivation of activity have not been elucidated.
However, it appears that conditions combining humidity, warmth, the presence of nutrients and the production of dust tend to result in release from bacterial stress.
The outermost cells of the biofilm may find themselves in a favourable environment, with oxygen, water and nutrients.
The may then resume normal metabolic activity, the outward sign of which is the resumption of cell division.
Growth can only occur in the plane perpendicular to the surface covered by the biofilm.
After a few cycles of cell division, the new bacterial cells form a fragile structure that detaches from the parent cells.
The free cells attach to the animals or their bedding where, despite their limited numbers, they mustily thanks to their greater virulence, and form colonies that are detectable because the cells are multiplying.
These mechanisms linked to bacterial stress, the formation of biofilms and bacterial multiplication, explain why farmers often find that although the animals and their bedding are uncontaminated, positive test results are obtained and the serotypes identified are identical to those found previously.

HOW TO TREAT BIOFILMS

Biofilms are very thin (less than 10 micrometres) and have a glycoprotein layer.
The bacteria within them are very well protected against external agents.
Scrubbing scours the surface of the biofilm, eliminating organic particles, and is very effective against the cells that are not contained within the biofilm.
Thus it is not surprising that tests performed after disinfection/washing procedures are negative.
However, the risks associated with the presence of the biofilm are not eliminated.
These risks can be reduced by applying a new "positive" biofilm over the existing biofilm (the "negative" biofilm).
The bacterial composition of the positive biofilm should be such that it prevents the growth of bacteria at the outermost edge of the negative biofilm.

Work carried out by the Cobiotex research group has shown that an association of Lactobacillus and Bacillus gives rise to properties unlike those of the bacteria of either of these families used separately.
One of these properties has proved to be particularly important : the association of specific strains of Lactobacillus and Bacillus leads to a bacteriostasis, and in some cases bacteriologic activity against several pathogenic bacteria, including all serotypes of Salmonella.
Application of a positive biofilm composed of Lactobacillus and Bacillus, makes it possible to prevent the development of the cells in the negative biofilm, by bacteriostasis activity.
Application of the positive biofilm is used as an adjunct to washing and disinfection of the farm buildings and is desired to prevent recontamination by cells from reactivated pathogenic elements in the negative biofilm.

CONCLUSION

Farm buildings are subject to the interacting influences of the animals, the farmer, the feed, the bedding and the wails on which biofilms develop.
In addition to strict checking of the animals and the food they consume, il is essential to ensure that the bedding and biofilms do not constitute a potential source of contamination for the animals.
The specific bacteriostatic/bacteriolytic properties of Cobiotex bacterial complexes, used in some cases to treat animal bedding and in others to produce a positive biofilm, make it possible to keep bedding free of bacteria such as Salmonella and to prevent the growth of virulent bacteria derived from biofilms present on the surfaces of buildings.
The treatment of bedding and negative biofilms is an excellent way to control the risks of bacterial contamination of farm animals, and to prevent Salmonella contamination.