Biofilm formation by clinical bacterial isolates. Biofilm formation by individual clinical isolates of E. coli (n=39), P. aeruginosa (n=36), S. aureus (n=23), K. pneumoniae (n=54), and A. baumannii (n=53) using the 96-well microtiter plate assay. Biofilm formation was assessed by staining the attached bacteria with 0.1% CV and measuring the OD values at 570nm (CV570) after 48 h growth at 37°C. Bars are representative of the average biofilm biomass from three independent experiments for each clinical isolate tested. Error bars indicate the standard error. Dashed line (−−-) indicates average biofilm biomass value (OD570 = 0.122) for S. epidermidis ATCC 12228, the positive control for biofilm formation. Bars representing individuals strains are color coded to indicate site of isolation. Clinical isolates were ordered randomly with the exception of S. aureus which was separated by methicillin resistant (MRSA) and sensitive (MSSA) strains.