Location: Meat Safety & Quality ResearchTitle: Escherichia coli O157:H7 strains isolated from High-Event Period beef contamination have strong biofilm-forming ability and low sanitizer susceptibility, which are associated with high pO157 plasmid copy number
|Bosilevac, Joseph - Mick|
|Kalchayanand, Norasak - Nor|
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2016
Publication Date: 11/1/2016
Publication URL: http://handle.nal.usda.gov/10113/5587629
Citation: Wang, R., Luedtke, B.E., Bosilevac, J.M., Schmidt, J.W., Kalchayanand, N., Arthur, T.M. 2016. Escherichia coli O157:H7 strains isolated from High Event Period beef contamination have strong biofilm-forming ability and low sanitizer susceptibility, which are associated with high pO157 plasmid copy number. Journal of Food Protection. 79(11):1875-1883. doi:10.4315/0362-028X.JFP-16-113.
Interpretive Summary: A biofilm is a group of bacteria that attach to each other and to solid surfaces to improve their ability to survive stressful conditions. These bacteria in the 3-dimensional biofilm structure are more resistant to sanitization. High Event Period (HEP) contamination of beef is the frequent occurrence of pathogen contamination in a short time frame. To investigate the potential contribution of biofilm formation and sanitizer resistance to HEP beef contamination by E. coli O157:H7, we characterized 45 E. coli O157:H7 strains isolated from 14 HEP contamination events and compared the results to 47 control strains isolated from cattle hide swabs. Our results showed that compared to the control strains, the HEP strains had significantly higher biofilm forming ability on surfaces of PVC plastic and stainless steel commonly used in the meat processing industry. The HEP strains showed very low resistance to medical antibiotics, but exhibited high tolerance and resistance to common sanitizers. The HEP strains contained a larger number of genes important for biofilm formation which was related to the strains’ stronger biofilm forming ability and higher sanitizer resistance; therefore, it might be the genetic basis for the HEP strains’ enhanced ability to survive in the meat plants and cause contamination. Further studies with in-plant sampling of contact and non-contact surfaces during and after HEP occurrences is needed to further explore the potential role of biofilms in HEP contamination.
Technical Abstract: In the meat industry, a “High Event Period” (HEP) is defined as a time period when beef processing establishments experience an increased occurrence of product contamination by E. coli O157:H7. Our previous studies suggested that bacterial biofilm formation and sanitizer resistance might contribute to HEPs. The present study was conducted to further characterize E. coli O157:H7 strains isolated during HEPs for their potential of causing contamination, and to investigate the genetic basis for strong biofilm forming ability and high sanitizer resistance. Our results showed that compared to the E. coli O157:H7 diversity control panel strains, the HEP strains had significantly higher biofilm forming ability on contact surfaces and lower susceptibility to common sanitizers. No difference in the presence of disinfectant resistant genes or the prevalence of antibiotic resistance was observed between the HEP and control strains. However, the HEP strains retained significantly higher copy numbers of the pO157 plasmid. Importantly, a positive correlation was observed among high plasmid copy number, strong biofilm forming ability, low sanitizer susceptibility and high survival/ recovery capability after sanitization, suggesting that these specific phenotypes could be either directly correlated to gene expression on the pO157 plasmid, or indirectly regulated via chromosomal gene expression influenced by the presence of the plasmid. Our data highlights the potential risk of biofilm formation and sanitizer resistance in HEP contamination by E. coli O157:H7, and calls for increased attention to proper and effective sanitization practice in meat processing facilities.