INFLUENCE ON PSEUDOMONAS-AERUGINOSA ELASTASE, PROTEINASE AND ALGINATEBY SUPRA-INHIBITORY AND SUPRA-SUBINHIBITORY CONCENTRATIONS OF QUINOLONES

Suppression of elastase, proteinase and alginate of Pseudomonas aerugi nosa after the exposure of a bacterial suspension (30 min) to supra-in hibitory concentrations (2x or 4x MIC) of norfloxacin was found. The n orfloxacin at 4x MIC was more effective, and this concentration depres sed elastase to 13.0%, proteinase to 14.6% and alginate to 0% of the c ontrol values. Enoxacin at 2x MIC did not affect the virulence factors studied, and at a concentration of 4x MIC only elastase was effective ly reduced to 61% of the control value. Supra-subinhibitory concentrat ions of the quinolones tested (2x or 4x MIC + sub-MICs) severely dimin ished all of the activities tested compared with supra-inhibitory conc entrations alone. Combinations of 4x MIC + sub-MICs were more effectiv e in the majority of cases.