title: Effect of sub-inhibitory concentrations of biocides on the architecture and viability of MRSA biofilms.
abstract: The effect of sub-minimum inhibitory concentrations (sub-MICs) of three biocides (benzalkonium chloride [BZK], trisodium phosphate [TSP] and sodium hypochlorite [SHY]) upon the architecture and viability of the biofilms formed by a methicillin-resistant Staphylococcus aureus strain of food origin (MRSA 48a) was investigated. Images were examined through confocal laser scanning microscopy (CLSM) after staining with SYTO9 and propidium iodide. Sub-MICs of BZK or TSP reduced the ability of MRSA to produce biofilm. In contrast, the presence of sub-MICs of SHY enhanced the biofilm-forming ability of MRSA when cells had undergone previous adaptation to this compound (biovolume in the observation field was 137,785.31 ± 47,682.79 μm3for biofilms formed in the presence of SHY, and 70,204.13 ± 31,603.98 μm3in the absence of biocides; P < 0.05). The largest amount of live (green stained) cells (P < 0.05) was observed in biofilms grown in the presence of SHY relative to the other conditions tested (58,999.75 ± 55,312.37 μm3vs 31,976.29 ± 38,594.98 μm3). Findings from the present work constitute the first report of biofilm production by MRSA being induced by sub-inhibitory concentrations of SHY. The data suggest that repeated use of SHY at low concentrations could represent a public health risk.
authors.affiliation: Department of Food Hygiene and Technology, University of León, E-24071 León, Spain; Institute of Food Science and Technology, University of León, E-24071 León, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Buzón-Durán
authors.affiliation: Department of Food Hygiene and Technology, University of León, E-24071 León, Spain; Institute of Food Science and Technology, University of León, E-24071 León, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Alonso-Calleja
authors.affiliation: Department of Electrical Engineering and Systems Engineering and Automatic Control, University of León, E-24071 León, Spain.
authors.forename: Félix
authors.initials: F
authors.lastname: Riesco-Peláez
authors.affiliation: Department of Food Hygiene and Technology, University of León, E-24071 León, Spain; Institute of Food Science and Technology, University of León, E-24071 León, Spain. Electronic address: rosa.capita@unileon.es.
authors.forename: Rosa
authors.initials: R
authors.lastname: Capita
mesh_terms: D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D004202:Disinfectants / Q000009:adverse effects / Q000737:chemistry / Q000494:pharmacology*; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects*; D018613:Microscopy, Confocal; D012973:Sodium Hypochlorite / Q000009:adverse effects / Q000494:pharmacology
chemical_list: D004202:Disinfectants; D012973:Sodium Hypochlorite
keywords: Biocides; Biofilm architecture; Biofilm viability; CLSM; MRSA