Matrix polymers of Candida biofilms and their possible role in biofilm resistance to antifungal agents

Extracellular polymeric material (EP), comprising the matrix of Candida alb icans biofilms, was isolated and its composition was compared with that of EP obtained from culture supernatants of planktonically grown (suspended) o rganisms. Both preparations consisted of carbohydrate, protein, phosphorus and hexosamine, but biofilm EP contained significantly less total carbohydr ate (41%) and protein (5%) than planktonic EP. It also had a higher proport ion of glucose (16%) and contained galactose, suggesting that it might poss ess components unique to biofilms. To investigate whether the EP matrix pla ys a role in the resistance of biofilms to antifungal agents, susceptibilit y profiles of biofilms incubated statically (which have relatively little m atrix) were compared with those for biofilms incubated with gentle shaking (which produce much more matrix material). Biofilms grown with or without s haking did not exhibit significant differences in susceptibility to any of the drugs tested, indicating that drug resistance is unrelated to the exten t of matrix formation. However, biofilms formed on two different types of p olyvinyl chloride catheter, obtained from different manufacturers, showed d ifferences in susceptibility to amphotericin B, suggesting that drug resist ance may arise as a result of highly specific, surface-induced gene express ion.