THE DEVELOPMENT OF A SMALL-SCALE BIOFILM MODEL SUITABLE FOR STUDYING THE EFFECTS OF ANTIBIOTICS ON BIOFILMS OF GRAM-NEGATIVE BACTERIA

A method for the study of membrane-associated biofilm populations of E scherichia coil ATCC 8739 using modified Swinnex filter units was deve loped. Biofilms were established under carbon limitation in a chemical ly defined simple salts medium. Cells, pressure filtered on to cellulo se nitrate membranes in situ, were perfused from the sterile side. Ste ady-state conditions were attained at which the growth rate of the ses sile cells could be demonstrated to be proportional to the flow rate o f medium. The antibiotic susceptibility of these biofilms was examined by including ciprofloxacin within the perfusing medium. Susceptibilit y of the biofilms to ciprofloxacin was found to be affected not only b y its concentration, but also by the growth rate of the bacteria.