Importance of experimental design in the evaluation of the influence of proteins in bacterial adherence to polymers.

The use of intravascular catheters is frequently associated with coagulase-negative staphylococcal infections. Colonization of catheters depends on the ability of bacteria to attach to artificial surfaces, this process is affected by macromolecules present in the body fluids. We determined the adherence of five coagulase-negative strains onto polyethylene, nylon and polyvinyl-chloride catheters, after treatment of bacteria, catheters or both with citrated human plasma, human serum albumin or fibrinogen. Plasma and serum albumin produced a marked inhibition of bacterial adherence (P less than 0.05) by means of adsorption on biomaterial surface. Fibrinogen enhanced (P less than 0.05) the number of bound bacteria, specially through its interaction with the staphylococcal surface. These observations suggest the possible role of plasma proteins in these infections.