[Postantibiotic effects and postantibiotic effects of subinhibitory levels of quinolines on Pseudomonas aeruginosa].

The postantibiotic effect (PAE) (PA phase induced by 2x or 4x MIC) and postantibiotic effect of subinhibitory concentrations (PA SME) of three quinolones-enoxacin, norfloxacin and pefloxacin against Pseudomonas aeruginosa were determined. It was observed that the tested antibiotics at suprainhibitory concentrations 2x MIC induced PAEs of 2.1-6.7 h. Longer PAEs were observed after treatment with antibiotics at concentration 4x MIC (4.1-9.0 h). Subinhibitory concentrations of quinolones added to bacterial suspensions in the postantibiotic phase (2x or 4x MIC) displayed longer delay of bacterial regrowth (PA SMEs) compared to PAEs. No regrowth of bacterial culture was observed even at 48 h in the case of pefloxacin (2x MIC + 0.3x MIC, 4x MIC +0.2x MIC, 4x MIC + 0.3x MIC) as well as norfloxacin (4x MIC + 0.2x MIC, 4x MIC + 0.3x MIC).