Purpose: The objective of this study was to measure the attachment and biomass formation of STEC O26, O45, O103, O111, O121, O145 and O157:H7 strains on stainless steel coupons over time when incubated at 7°C and 25°C.
Methods: Seven strains previously determined to have a strong affinity for attachment and one strain determined to have a low affinity for attachment were used in this study. Strains were used to inoculate stainless steel coupons in M9 minimal salt media and incubated at either 7°C or 25°C for up to 96h. At 4h, media was removed, all coupons were rinsed with water, and fresh media was added. At the time interval (4, 48 or 96h), the coupons were removed, rinsed, and stained with crystal violet. Crystal violet was removed from the coupon and solution absorbance at 590 nm was measured.
Results: Significant (P < 0.0001) interactions for strain*temperature and temperature*hour were noted. Strains of O45, O103, O111, and O157:H7 had differences in absorbance between temperatures. Differences among strains were noted for each temperature. Differences in attachment between temperatures were observed at 48 and 96 hours. At 25°C, attachment increased after 48 hours, while at 7°C, an increase was observed at 48 hours, then absorbance declined at 96 hours.
Significance: These data indicate that the strains tested can attach and form biomasses at both ambient and refrigerated temperatures. However, attachment and biomass formation appears to be strain dependent. Further research is needed to understand if other strains within these serogroups have the ability to attach under similar conditions.