Abstract
Forming biofilm is a strategy utilized by Shiga toxin-producing Escherichia coli (STEC) to survive and persist in food processing environments. We investigated the biofilm-forming potential of STEC strains from 10 clinically important serogroups on stainless steel at 22 °C or 13 °C after 24, 48, and 72 h of incubation. Results from crystal violet staining, plate counts, and scanning electron microscopy (SEM) identified a single isolate from each of the O113, O145, O91, O157, and O121 serogroups that was capable of forming strong or moderate biofilms on stainless steel at 22 °C. However, the biofilm-forming strength of these five strains was reduced when incubation time progressed. Moreover, we found that these strains formed a dense pellicle at the air-liquid interface on stainless steel, which suggests that oxygen was conducive to biofilm formation. At 13 °C, biofilm formation by these strains decreased (P < 0.05), but gradually increased over time. Overall, STEC biofilm formation was most prominent at 22 °C up to 24 h. The findings in this study identify the environmental conditions that may promote STEC biofilm formation in food processing facilities and suggest that the ability of specific strains to form biofilms contributes to their persistence within these environments.
Highlights
Biofilm formation has gained considerable attention in food processing environments
We found that the attached biomass of strains O113, O145, O91, O157, and O121 decreased (P < 0.05) with incubation time at 22 ◦C (Figure 1B)
We found that the attached biomass of strains O113, O145, O91, O157, and O121 decreased (P < 0.05) with incubation time at 22 °C (Figure 1B)
Summary
Biofilm formation has gained considerable attention in food processing environments. The attachment of microorganisms and subsequent development of biofilms in these environments may be a leading cause of the adulteration of food, which results from the biofouling of pipelines and processing equipment [1]. Biofilms of spoilage and pathogenic microflora that form on contact surfaces are often responsible for the contamination of food during post-processing production [2,3]. Bacteria can readily bind to stainless steel and polymer surfaces in food production systems and form biofilms where cells are embedded within a matrix made up of proteins, carbohydrates, and extracellular DNA [5,6]. Biofilm formation in food processing environments increases the resistance of cells to a number of stressors including starvation, heat, cold, and sanitizers [8,9]
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