Purpose: This study investigates biofilm formation by Escherichia coli O157:H7 and Salmonella at different temperatures and media concentrations on glass and cement coupons and tested commercially available sanitizers and hot water for biofilm removal.
Methods: Biofilms of E. coli O157:H7 (ECH7C and ECH7P), Salmonella Enteritidis (SEP) and Salmonella spp. (SSP) were developed on glass and cement coupons in Tryptone soy broth (TSB), TSB + 0.5% glucose, TSB + 1% glucose, TSB + 2% sheep blood and TSB + 5% sheep blood for 5 days at 11°C and 28 ± 2°C. Biofilm quantification was done using crystal violet binding assay. Biofilms removal was tested by exposing biofilms to 20 ml of sanitizers, Diskol/Morigad and Hot water (85°C) for 5 mins. The experiment was done in triplicates.
Results: Significantly (P < 0.05) more biofilms (OD=optical density) were formed at 28 ± 2°C than 11°C on cement (0.451-0.565) than on glass (0.277-0.358) for all strains. Addition of 1% glucose or 2% sheep blood significantly enhanced biofilm formation. For biofilms developed at 11°C, hot water removed more E. coli O157:H7 biofilms on cement (0.007-0.118) than glass (0.004-0.030). Salmonella biofilms removal on cement (0.001-0.148) was higher than glass (0.001-0.058). Diskol was most active for E. coli O157:H7 biofilm reduction especially those formed (28 ± 2°C) in TSB broth (0.010–0.076) and TSB broths with supplements (0.007–0.145) on glass. On cement, Morigad was most effective (0.009-0.216). Salmonella biofilms were more resistant than E. coli O157:H7 biofilms at 28 ± 2°C. SEP biofilms grown in TSB+0.5%glucose was resistant to Diskol/Morigad and hot water but susceptible when grown in TSB+5% sheep blood (0.044-0.046).
Significance: Understanding of the influence of temperature, anti-biofilm agent type and contact surface on E. coli O157:H7 and Salmonella biofilms may provide effective strategies for biofilm control.