Studies on the formation, composition and detection of biofilms of food-borne pathogens

Abstract

Biofilms enable food-borne pathogens to resist removal from surfaces and survive disinfection. Biofilms of pathogens [e.g., S. enterica Serovar Typhimurium DT104 (STDT104)] formed on various surface types were probed with Calcofluor (b-D-glucan-specific ) and lectins. All biofilms were detected after exposure to Calcofluor. Lectins bound to specific carbohydrates in bacterial exopolymeric substances (EPS). Results supported the in vitro use of Calcofluor and lectins as non-specific and genera-specific probes of biofilms. Next, the capsular polysaccharide (CP) of STDT104 was extracted and shown to contain glucose, mannose and trace amounts of galactose. Polyclonal antibodies against this extract were specific for a CP as demonstrated by western blots and immunoelectron microscopy. Confocal microscopy images revealed the following: thicker biofilms formed at 25?C, CP synthesis was not temperature-dependent and not produced by all cells. Synthesis of CP by STDT104 may represent an aggregative and protective substance in addition to curli and cellulose