The biofilm-forming ability of Salmonella enterica subsp. enterica isolated from swine-feed mills

Abstract

ABSTRACT: Animal feed has been considered an important vehicle for introducing Salmonella enterica subsp. enterica in pig farms. Salmonella survival and persistence in feed mill environments have been associated with biofilm-forming ability. This study evaluated 54 Salmonella isolates from swine-feed mills for: i. phenotypic expression of curli fimbriae and cellulose; ii. pellicle formation at the air-liquid interface; iii. adhesion on polystyrene microtiter plates; and iv. the presence of the main genes associated with biofilm formation. Regarding phenotypic cell morphology assays, all Salmonella isolates presented morphotype RDAR at 28 °C and SAW at 37 °C. Rigid pellicle formation at the air-liquid interface was observed in 51.85% (28/54), while fragile pellicle was seen in 18.52% (10/54), and 29.62% (16/54) were not able to produce pellicle. Biofilm quantification on polystyrene microtiter plates showed that 98.15% (53/54) of Salmonella isolates were able to form biofilms at 28 °C, while 83.33% (45/54) of the isolates were classified as non-adherent at 37 °C. The genes csgD, fimA, adrA, and bapA were found in all isolates evaluated. These results indicated that Salmonella serovars from swine-feed mills have the biofilm-forming ability.