FIG 4.

Total bacterial numbers in biofilms on conveyor belt coupons prior to C&D. Biofilms were allowed to develop undisturbed until day 4 before being rinsed in H₂O or cleaned with Alkalifoam and disinfected with either a QAC- or a PAA-based disinfection agent on three consecutive days. The microbiota on coupons harvested on day 7 had been allowed to regrow for 24 h after the last disinfection step. The L. monocytogenes counts in multigenus biofilms were determined by plating on selective agar. Mean values from five replicates are shown, except for the sample labeled H₂O, where the mean from two replicates is shown. Error bars show standard errors of the means. Asterisks represent differences in L. monocytogenes CFU per coupon relative to that in multigenus biofilms harvested on day 4 (two-tailed paired Student t tests). *, P = 0.08; **, P < 0.05.