Biofilm Formation Potential of Heat-Resistant Escherichia coli Dairy Isolates and the Complete Genome of Multidrug-Resistant, Heat-Resistant Strain FAM21845

Abstract

We tested the biofilm formation potential of 30 heat-resistant and 6 heat-sensitive Escherichia coli dairy isolates. Production of curli and cellulose, static biofilm formation on polystyrene (PS) and stainless steel surfaces, biofilm formation under dynamic conditions (Bioflux), and initial adhesion rates (IAR) were evaluated. Biofilm formation varied greatly between strains, media, and assays. Our results highlight the importance of the experimental setup in determining biofilm formation under conditions of interest, as correlation between different assays was often not a given. The heat-resistant, multidrug-resistant (MDR) strain FAM21845 showed the strongest biofilm formation on PS and the highest IAR and was the only strain that formed significant biofilms on stainless steel under conditions relevant to the dairy industry, and it was therefore fully sequenced. Its chromosome is 4.9 Mb long, and it harbors a total of five plasmids (147.2, 54.2, 5.8, 2.5, and 1.9 kb). The strain carries a broad range of genes relevant to antimicrobial resistance and biofilm formation, including some on its two large conjugative plasmids, as demonstrated in plate mating assays.IMPORTANCE In biofilms, cells are embedded in an extracellular matrix that protects them from stresses, such as UV radiation, osmotic shock, desiccation, antibiotics, and predation. Biofilm formation is a major bacterial persistence factor of great concern in the clinic and the food industry. Many tested strains formed strong biofilms, and especially strains such as the heat-resistant, MDR strain FAM21845 may pose a serious issue for food production. Strong biofilm formation combined with diverse resistances (some encoded on conjugative plasmids) may allow for increased persistence, coselection, and possible transfer of these resistance factors. Horizontal gene transfer may conceivably occur in the food production setting or the gastrointestinal tract after consumption.

Biofilm formation of Staphylococcus aureus dairy isolates representing different genotypes

“…Factors including incubation time, growth surface, and nutrients are thought to influence biofilm formation in staphylococci measured by static or dynamic model assays (Stepanović et al, 2001;Vanhommerig et al, 2014;Van Kerckhoven et al, 2016). Furthermore, we have recently shown similar results on biofilm formation of E. coli dairy isolates, noting a lack of correlation between static and dynamic conditions (Marti et al, 2017). From our results, we cannot conclude that differences observed in terms of biofilm formation are due only to the growth under flow conditions because the growth surface was not the same (polystyrene for the static model; glass in the dynamic model), which can influence the adhesion process.…”

Phenotypic and Genetic Determination of Biofilm Formation in Heat Resistant Escherichia coli Possessing the Locus of Heat Resistance

“…Poor plant sanitation can allow for biofilm formation on these surfaces and become a source of contamination [ 9 ]. Many processing plants incorporate high temperatures into their cleaning procedures but limited research has been conducted thus far on whether heat resistance contributes to increased survival of E. coli in biofilms [ 43 ]. Furthermore, previous studies on the effect of environmental stressors on EHEC found it unlikely that strains could possess virulence genes for human infection and phenotypes for evading pathogen intervention measures in the food processing industry [ 44 ].…”

Biopelículas y persistencia microbiana en la industria alimentaria

“…Finalmente, también se ha identificado una interconexión entre las respuestas de adaptación al estrés y la formación de biopelículas, que podría ser la responsable de la mayor robustez de las células que conforman las biopelículas. Así, por ejemplo, el regulador de la respuesta general al estrés en bacterias Gram negativas, el factor alternativo RpoS, ha sido identificado como un factor clave para el establecimiento de biopelículas maduras en E. coli (Álvarez-Ordóñez et al, 2013;Chen et al, 2013) y también se ha observado un vínculo entre el potencial de formación de biopelículas de E. coli y su termorresistencia (Marti et al, 2017).…”