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Research on salmonella biofilm

Feed contaminated with salmonella is a well-known problem world wide and constitutes a considerable risk of disease among animals and also of salmonellosis in consumers of animal products.

 

 

Norway is in a favourable situation with regards to salmonella in feed and this has been the case for several years, much because Norway has a fairly strict control system in order to maintain this situation. Factories are required to have an internal control system that includes sampling procedures, and salmonella is found in the factories from time to time.

The National Veterinary Institute has performed research on salmonella in factory environments since 2000 together with the research scientists Møretrø, Langsud and Heir at Nofima Mat, and together with professors Aamdal Scheie and Benneche at the University of Oslo since 2005.

We found that some salmonella clones persist in feed and fishmeal factories for years. Furthermore, we have shown that persistence in the factory environment is associated with the ability to form biofilm at room temperature in laboratory assays. Salmonella cells in biofilm were tolerant to many of the disinfectants used in the factories, even though all disinfectants were effective against the same strains in the planctonic stage. Pre-treatment with a synthetic brominated furanone significantly potentiated the effect of disinfectants.

Expression of two of the salmonella matrix components, curli fimbriae and cellulose, can be studied an agar added Congo red and Commassie blue dyes. The most common morphotype, rdar (red dry and rough) indicates expression of both components. However, more than 50% of the strains of the serovar Agona studied displayed the morphotype bdar (brown dry and rough), indicating expression of curli fimbria, but not cellulose. S. Agona strains have been shown to persist in some factories for years. Chemical studies showed that the bdar strain biofilms did not have one or more polysaccarides lacking in the rdar strains. Furthermore, rdar and bdar strains displayed the same tolerance against disinfectants when they are in biofilm.

We are currently studying the effect of quorum sensing and furanones on salmonella biofilm.

 

Contact person National Veterinary Institute:
Live Nesse, Senior scientist, Section of Bacteriology
E-mail: live.nesse@vetinst.no
Tlf.: + 47 23 21 63 15/924 41 267

Lene Karine Vestby, scientist, Section of Bacteriology
E-mail: lene.vestby@vetinst.no
Tlf.: + 47 23 21 63 89