Genotypic and phenotypic characteristics associated with biofilm formation in Escherichia coli and Salmonella spp. isolated from ulam in Terengganu

Nowadays, the foodborne outbreaks associated with fresh produces, including ulam, areincreasing worldwide. The biofilm formation or bacterial attachment to plant surface is theinitial step towards the contamination in fresh produce. The biofilm phenotype of bacteriagrown on congo red agar is termed as red, dry and rough (rdar) morphotype. The bindingof congo red dye with both biological proteins and inert surfaces is due to the presence ofcurli fimbriae and cellulose as the main extracellular components. The objective of thisstudy was to determine the rdar morphotypes, biofilm ability and the role of csgA gene ofEscherichia coli and Salmonella spp. isolated from ulam or Malaysian herbs. A total of29 isolates, including 23 E. coli and 6 Salmonella spp. were analyzed for their ability toproduce biofilm by colony morphology test, microtiter plate biofilm assay and qualitativebiofilm test (pellicle formation). The presence of the csgA gene of E. coli was identifiedby PCR, which demonstrated the potential gene that able to produce curli fimbriae.Results revealed that 16 (69.6%) E. coli isolates were categorized as strong biofilmproducers, 2 (8.7%) as moderate biofilm producers, 3 (13%) as weak biofilm producers,whereas 2 (8.7%) as negative biofilm producers (did not produce biofilm). While 4(66.7%) Salmonella spp. isolates were identified as strong biofilm producers, 1 (16.7%) asmoderate biofilm producers and 1 (16.7%) as negative biofilm producers. Majority of theE. coli strains (69.6%) were identified as strong biofilm producers and able to express rdarmorphotypes. The ability of the of E. coli and Salmonella spp. isolates to form biofilmreveals the ability of these isolates to persist on the fresh vegetables and become hosts forthe disease transmission to humans or/and animals.