ILLUSTRATION: LALLEMAND
In farm buildings all surfaces — floors, walls, ceilings and equipment — are colonized by biofilms.
described to explain the modes of action of positive biofilms on farm building surfaces (Figure 2). 1. Anti-adhesive effect: the presence of the positive biofilm itself, or some molecules it produces, can limit the initial adhesion of pathogens on the surface. 2 & 3. Spatial and nutritional competition: by occupying the space and consuming the available nutritional resources, the positive biofilm can limit the proliferation of undesirable bacteria. 4. Microbial interference: through the secretion of specific effectors, such as organic acids or antagonistic molecules, positive biofilms can create an unfavourable environment to help mitigate the presence of undesirable micro-organisms on the surface.
Selecting the best candidate Advanced screening and metagenomic techniques are used to select the best bacterial strains able to form positive bio- films on farm building surfaces and help keep pathogens at bay. Even where the selection starts in the laboratory, scien- tists ensure that the bacteria selected are adapted to farm ec- obiological and physico-chemical conditions. Most products available on the market are mixtures of lactic acid bacteria (LAB) and Bacillus species. Synergy has been shown between these species. For example, it has been observed that biofilm formed by Bacillus subtilis protects LAB from desiccation. The application method (spraying) has to be carefully adapt- ed to the selected strains, too. This is all part of the formula- tion which should be designed to allow optimum adhesion to various surfaces, horizontal and vertical, and ensure early growth of the bacteria (presence of specific nutrients, such as sugar). Finally, the authors indicated that the use of a positive biofilm in farm buildings can have a prolonged beneficial effect beyond building surfaces by reducing the spread of
pathogenic organisms and by seeding beneficial bacteria in farm effluents, the environment and the food chain. A valuable tool within a farm-to-fork approach to biosecurity.
On-farm results Several studies have already demonstrated the benefits of positive biofilms applied to farm buildings. For example, Rodiles and others (2021) reported how an early microbial intervention on building surfaces can influence the microbial communities in a biofilm in a commercial chicken production system. The team used 16S rRNA analysis to identify the biofilm microbial populations. They detected a significant in- crease and persistence of two genera likely resulting from the contribution of the microbial strains contained in the product (Lalfilm Pro) that was applied. Meanwhile, important families such as Enterococcaceae and Enterobacteriaceae were limited during the first week of rearing. Further data from this study have been submitted to peer-reviewed publications.
References available on request.
Figure 2. Diagram illustrating the four possible mechanisms triggering the ex- clusion of undesirable micro-organisms further to settling and colonization by positive biofilms.
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