Shiga Toxigenic Escherichia coli (STEC) multispecies biofilm formation and its persistence mechanisms in beef processing facilities

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Nan, Yuchen
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Shiga-toxigenic Escherichia coli (STEC) are critical enteric pathogens linked to severe foodborne illnesses outbreaks. A potential mechanism for STEC survival and persistence is the formation of biofilms and association with other bacteria in the beef fabrication environment. This research involved two STEC serogroups studies with different biofilm-forming abilities, including strong biofilm producer STEC O103:H2 (99-2076) and a moderate biofilm former STEC O157:H7 (1934). One LAB: T1 (Carnobacterium piscicola + Lactobacillus bulgaricus), and two SP: T2 (Comamonas koreensis + Raoultella terrigena); T3 (Pseudomonas aeruginosa + C. koreensis) were tested for their ability to form multispecies biofilms with STEC. STEC single-species biofilms were included as controls (T4). In both studies, the selected STEC serogroups interactions with LAB or SP multispecies biofilms on TPU and SS coupons were evaluated at 10 °C and 25 °C under wet and dry conditions after 6, 30 & 60 d of storage. The capacity of STEC transfer to beef was assessed, and STEC survival within single and multispecies biofilm was assessed by enrichment. At 25 °C, multispecies biofilm mixture P. aeruginosa + C. koreensis (T3) showed antagonistic interactions against STEC, decreasing O103:H2 and O157:H7 cell transfer to beef by 2.54 log10 CFU/g (P < 0.001) and 1.76 log10 CFU/g (P < 0.001), respectively. At 25 º C, no interactions (P > 0.05) against O103:H2 or/ O157:H7 were found on biofilms combining, C. piscicola + L. bulgaricus (T1) and C. koreensis + R. terrigena (T2). At 10 °C, none of the multispecies biofilms altered the cell transfer of O103:H2 or/ O157:H7 to beef (P > 0.05) compared to the control positive. A greater extent of STEC viable cell transfer to beef from fresher (6 d), moist biofilm, on the TPU surface was observed. No beef contamination with STEC was detected from 60 d old dry biofilms. After enriching the 60 d dry biofilm, the highest overall STEC survival rate was observed from 10 °C multispecies biofilm R. terrigena + C. koreensis (dry-T2). The present study demonstrated that the risk of STEC contaminating beef can be influenced by bacterial species composition, adherent surface, humidity, and the age of biofilms.
STEC, Multispecies biofilm, Persist, Beef contamination