Laboratory methods for studies of bacterial adhesion

Prosthetic infection following total joint replacement can have catastrophic results both physically and psychologically for the patients, leading to complete failure of the arthroplasty, possible amputation, prolonged hospitalization, and even death. Bacterial adherence to biomaterial surfaces is an important step in the pathogenesis of prosthetic infection. The exact mechanism of prosthetic infection remains unclear. It is thought that certain bacteria, particularly coagulase-negative staphylococci, after adhering to biomaterial surfaces, secrete a layer polysaccharide, an extracellular substance (slime) and then form a biofilm (a biomass of bacteria and slime). The biofilm makes the embedded bacteria less accessible to the human defense system and significantly decreases antibiotic susceptibility. Before effective preventive or therapeutic measures can be achieved, the process, characteristics, or mechanism of bacterial adhesion to biomaterials have to be studied. In this review, the in-vitro experimental methods for bacterial adhesion will be discussed, which concentrates on (1) how to design a new in-vitro model of bacterial adhesion or biofilm formation, including the selection of bacteria, sample surface preparation, conducting bacterial adhesion or biofilm formation experiments, and the sample preparation for evaluation; and (2) methods for examining adhered bacteria and biofilm, which include microscopy for counting and morphological observation of adhered bacteria, viable bacterial counting methods, other direct or indirect bacterial counting methods, and the methods for evaluating biofilm. (C) 1997 Elsevier Science B.V.