Purpose: The objective was to enumerate attachment and biomass formation to stainless steel (SS) or polyurethane (CB) coupons by strains of each STEC serogroup.
Methods: Three strains from each serogroup with differences in strain origin and presence of stx1 and stx2 were examined. Coupons of SS or CB were incubated in minimal or full nutrient broth (TSB) inoculated with a single STEC strain at 25°C for up to 48h. At 4h, loosely attached cells were rinsed from coupons and fresh media was added. At the time interval (4, 24 or 48h), coupons were removed, rinsed, placed in buffered peptone water (BPW) with beads and vortexed. Serial dilutions were plated onto tryptic soy agar and incubated for 24h at 37°C. Data were converted to CFU/cm2 prior to analysis.
Results: For coupons incubated in minimal media, there were no significant differences (P > 0.05) for attachment and biomass development for the coupon material. However, a significant interaction (P < 0.05) was observed for strains over time. Coupons inoculated with strains in TSB had significant interactions for strains over time and coupons over time. For both SS and CB coupons, significant increases in biomass formation were observed between 4 and 24h.
Significance: These results show STEC biomass formation are strain dependent. STECs have also been shown to attach and grow on different processing surfaces. Further research to understand efficacy of cleaners and sanitizers against these strains that form biomass is needed.