Resumen de Attachment and Biofilm Formation by Selected Strains of Salmonella entericaand Entrohemorrhagic Escherichia coliof Fresh Produce Origin

Ran Han, Yaa Asantewaa Kafui Klu, Jinru Chen

• This study compared the abilities of selected Salmonella entericaand enterohemorrhagic Escherichia coli(EHEC) strains of fresh produce origin to form biofilms on polystyrene surface and to attach to alfalfa and bean sprouts. Each of the 7 S. entericaand 4 EHEC inocula (2 mL; 107CFU/mL) was placed in 6 different broths in 24‐well polystyrene tissue culture plates at 28 °C for 1 to 7 d. Developed biofilms were quantified using the crystal violet binding assay. In a separate experiment, alfalfa and mung bean sprouts (5 g) were exposed to 25 mL inocula (107CFU/mL) of S. entericaor EHEC at 22 °C for 2 h with shaking at 40 rpm. Contaminated sprouts were thoroughly rinsed and homogenized in 0.1% peptone water, and bacteria attached to sprouts were enumerated. Biofilm mass accumulated on polystyrene surface increased with incubation time (P< 0.05). Among the microbiological media used, LB no salt (NaCl) broth better supported biofilm development (P< 0.05). Two EHEC strains formed more biofilms than the Salmonellaand other two EHEC strains (P< 0.05). However, more Salmonellacells (5.66 log CFU/g) attached to sprouts than EHEC cells (3.46 log CFU/g). Both Salmonellaand EHEC attached in higher numbers to mung bean, than alfalfa, sprouts (P< 0.05). This study determined the ability of some strains of S. entericaand enterohemorrhagic E. coli(EHEC) strains of fresh produce origin to form biofilm on polystyrene surface and their ability to attach to alfalfa and bean sprouts. Information obtained from the research deepens our knowledge on the interaction of selected bacterial pathogens with their contact surfaces and fills the knowledge gap in the current body of literature.