June 1, 2009
Norwegian study finds clue to salmonella persistence in feed
Researchers at Norway''s National Veterinary Institute have found that biofilm-forming capabilities of salmonella are related to their persistence in fishmeal and feed plants.
Salmonella are occasionally isolated from the feed factory environment and some clones of salmonella persist in the factory environment for several years.
One hypothesis is that biofilm formation facilitates persistence by protecting bacteria against environmental stress, for example, disinfection.
The study aims to investigate the biofilm-forming potential of salmonella strains from feed and fishmeal factories, including 111 strains isolated from Norwegian feed and fishmeal factories in the period 1991-2006 of serovars Agona, Montevideo, Senftenberg and Typhimurium.
Significant differences were found between serovars regarding the abilities to form biofilm on polystyrene and in the liquid air interface of nutrient broth.
Strains of the salmonella ser. Agona and Montevideo were good biofilm producers, and clones of these strains have been observed to persist in factories for several years.
Most salmonella ser. Senftenberg clones persisted for a shorter period, and they were medium biofilm producers.
Strains of ser. Typhimurium were relatively poor biofilm producers and clones have not been observed to persist.
The results indicate that persistent strains produced more biofilm than non-persisting strains, and that the biofilm-producing ability may be an important factor for persistence of salmonella in the factory environment.