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Formation and resistance to cleaning of biofilms at air-liquid-wall interface. Influence of bacterial strain and material

Piyush Kumar Jha 1 Heni Dallagi 1 Elodie Richard 2 Thierry Benezech 1 Christine Faille 1
2 UMS2014 - Plateformes Lilloises en Biologie et Santé
INSERM - Institut National de la Santé et de la Recherche Médicale, Université de Lille, Institut Pasteur de Lille, CHU de Lille, CNRS - Centre National de la Recherche Scientifique
Abstract : Interfaces between air, liquid and walls (ALW interfaces) are known to be conducive to the formation of biofilms, at least in some bacteria, yet little information is available on the influence of material properties on the amount of biofilms formed and their resistance to a cleaning procedure. In this study, we investigated the ability of four bacterial strains (Pseudomonas fluorescens [Pf1], Escherichia coli [Ec-SS2], Bacillus cereus [Bc-98/4] and B. subtilis [Bs-PY79]) to form biofilms in static conditions at the ALW interface on four materials with very different topographic and hydrophilic/hydrophobic properties (stainless steels with 2R or 2B finishes, polypropylene and glass). Biofilms were observed after staining with orange acridine visually, by epifluorescence microscopy and by confocal scanner laser microscopy. The number of culturable cells within biofilms was also estimated after growth on agar. After one-day of incubation in a bacterial suspension, three strains (except Bc-PY79) were found to form large amounts of biofilm, easily observable to the naked eye. However, great differences were observed between strains in the number of CFU (between 4.7 and 7.4 log CFU cm−2 ), as well in the biofilm structure. Furthermore, the material also affected the amount and/or structure of biofilms, and a 3D-biofilm organisation was only observed for two of the four tested strains (Bc-98/4 and Pf1) on PP, a hydrophobic material. After a standard cleaning-in-place treatment involving NaOH 0.5% at 60 °C, cultivable cells were only detected from Bc98/4 biofilms (growth on agar), while biofilms were also still visible on coupons contaminated with Pf1. Furthermore, most residual biofilms after cleaning appeared orange by epifluorescence microscopy after staining with orange acridine suggesting the presence of many viable but non-culturable cells within the residual biofilms. In Bc-98/4 biofilms, spores were also clearly observed by epifluorescence microscopy. Knowing their ability to survive the conditions encountered during cleaning procedures, this could account for the high level of CFU enumerated after cleaning. Lastly, Bc-98/4 biofilms formed on stainless steel 2R were more resistant to cleaning than on PP and glass. All of these results highlighted the importance of biofilms at the ALW interfaces in the control of surface hygiene, particularly in the food industry. We then investigated whether the shape of the menisci at the interfaces (convex vs concave, kinetics over time) could at least partly explain the shape or even the resistance to detachment of the ALW biofilms.
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Déposant : Christine Faille <>
Soumis le : lundi 15 juin 2020 - 10:09:31
Dernière modification le : samedi 27 juin 2020 - 03:01:57




Piyush Kumar Jha, Heni Dallagi, Elodie Richard, Thierry Benezech, Christine Faille. Formation and resistance to cleaning of biofilms at air-liquid-wall interface. Influence of bacterial strain and material. Food Control, Elsevier, 2020, pp.107384. ⟨10.1016/j.foodcont.2020.107384⟩. ⟨hal-02867860⟩



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