Biofilm culture of Pseudomonas aeruginosa expressing lux genes as a model to study susceptibility to antimicrobials

A simple in vitro model for culture of biofilm populations of self-biolumin escent Pseudomonas aeruginosa was used for real-time monitoring of the effe cts of ciprofloxacin. Biofilms of these organisms were established within S orbarod filters, perfused with a chemically defined simple salts medium. Th e biofilm population was shown to achieve a pseudo-steady state which was r eproducible and stable over several days. The viability of membrane-associa ted and eluted cells was assessed by spread plate viable counts and by moni toring bioluminescence as a measure of metabolic activity. Pseudo-steady st ate biofilms were exposed to 5 x MIC ciprofloxacin (0.3 mg 1(-1)) in the pe rfusing medium for 1 h. Whilst both methods for viability assessment indica ted an immediate reduction in viable cell numbers, the decline recorded wit h bioluminescence was greater. The use of bioluminescent bacteria proved to be a rapid and sensitive method for the measurement of real-time antibacte rial effects on a bacterial biofilm. (C) 2001 Federation of European Microb iological Societies. Published by Elsevier Science B.V. All rights reserved .