Optimization of microtitre plate assay for the testing of biofilm formation ability in different Salmonella serotypes

Salmonella has the ability to form biofilms on food-processing surfaces including plastic, potentially leading to food product contamination. The objective of this study was to determine the biofilm ability of different Salmonella serotypes for which microtiter plate assay was optimized. The assay was optimized with growth of Salmonella cells in Luria-Bertani broth for 48 h incubation, fixing of cells by heat (80°C, 30 min) and staining with 0.5% crystal violet stain and measuring crystal violet absorbance, using solubilizing (ethanol/acetone, 80: 20%) solution. A total of 151 strains of Salmonella consisting reference and field isolates from diverse sources belonging to 69 serotypes were screened for biofilm production. Majority of strains (87, 57.61%) were found to be moderate biofilm producers, while 34 (22.52%) and 29 (19.21%) strains were weak and strong biofilm producers, respectively. One strain belonging to S. Munster serotype did not produce any biofilm. The optimized microtitre plate assay can be effectively used for the assessment of biofilm ability of Salmonella strains. The highlight of the study was the testing of large number of Salmonella strains belonging to several serotypes. Majority of Salmonella strains are shown to form biofilms on plastic surface which has significance for food industry