Changes in the composition and architecture of staphylococcal biofilm by nisin

Abstract

Bacterial biofilms are involved in various medical infections and food contamination episodes and, for this reason, it is of great importance to developing new strategies of its prevention and control. The subinhibitory concentration of nisin was determined, and its effect against Staphylococcus aureus and Staphylococcus epidermidis biofilms was evaluated. Results obtained by confocal laser microscopy demonstrated morphological changes in the architecture of the structure of biofilms. The main components (polysaccharides, proteins, and extracellular DNA (eDNA)) of the biofilm matrix were determined by spectrophotometry and showed that the formation of staphylococcal biofilms in the presence of nisin results in a less dense matrix structure with modification in its constituents. These results contribute to increase the knowledge of the composition and architecture of the extracellular matrix of biofilms of S. aureus, as well as evidence that the investigation of alternative products to assist in the control and combat of biofilms is a promising strategy.

Keywords: Bacteriocin; Biofilm composition; Nisin subinhibitory concentrations; Staphylococcus aureus.

Fig. 1

Images of confocal laser microscopy. Biofilm produced during 46 h by the mixed culture of S. aureus COL, S. aureus FRI 722, and S. aureus Embrapa 4018 a without nisin and b in the presence of nisin (2.01 mg l⁻¹). The green fluorescence represents live cells stained with FITC while red and yellow show dead cells stained with propidium iodide. Scale bar = 20 μm

Fig. 2

Images of confocal laser microscopy. Biofilm produced during 46 h by the mixed culture of S. aureus COL, S. aureus FRI 722, and S. aureus Embrapa 4018 on polystyrene surface in the absence of nisin. The green fluorescence represents live cells stained with FITC while red and yellow show dead cells stained with propidium iodide. Image generating biofilm slices with standardized cuts of 1.0 μm

Fig. 3

Images of confocal laser microscopy. Biofilm produced during 46 h by the mixed culture of S. aureus COL, S. aureus FRI 722, and S. aureus Embrapa 4018, on polystyrene surface in the presence of nisin (2.01 mg l⁻¹). The green fluorescence represents live cells stained with FITC while red and yellow show dead cells stained with propidium iodide. Image generating biofilm slices with standardized cuts of 1.0 μm

Fig. 4

Composition of the biofilm by the mixed culture of S. aureus and by S. epidermidis ATCC 35984. Optical density (590 nm) corresponding to the detached portion of each biofilm component in the absence (white bars) and presence (gray bars) of nisin (2.01 mg l⁻¹) with respect to total biofilm, polysaccharides, proteins, and nucleic acid (eDNA) components. * indicates statistical significance by the Tukey test at 5% probability error