Methicillin-Resistant Staphylococcus aureus Biofilms and Their Influence on Bacterial Adhesion and Cohesion

Figure 3

Colony morphologies as distinguishing features of methicillin-resistant Staphylococcus aureus biofilms. (a) Morphology of colonies produced on TSA supplemented with 1% glucose. Most colonies had the same structure in the middle, with a wide, circular, and smooth appearance (t127/14, t127/17, t790/19, t223/20, and t127/22), whereas other isolates (t127/1, t127/2, t127/3, t127/5, t127/6, t127/7, t123/8, t127/10, t127/11, t127/12, t127/13, t127/15, t127/16, t127/16, t127/18, t127/21, t127/23, t127/24, and t127/25) showed net-like structures with small, raised nodules in transparent layers with irregular margins. Clones t127/2, t2246/9, and t223/20 showed unique structures with large cavities in the middle surrounded by highly autoaggregated transparent cell layers. Isolate t124/4 formed colonies that appeared like transparent flowers, with circular and vertical lines radiating from the centres of the colonies. (b) Morphology of colonies produced on Congo red agar (CRA) medium; differences based on biofilm components can be seen. The interaction of proteins with Congo red dye produced a red colour, whereas a black colour resulted from the interaction of the dye with exopolysaccharides. Images were captured by a digital camera (Canon IXUS265 HS).

(a)

(b)