The aim of this study is 1. to describe levofloxacin pharmacokinetics in ICU patients suffering from pneumonia with taking into account physio-pathological parameters. 2. to verify clinical and bacteriological efficiency and to know if the peak/Minimum Inhibitory Concentration (MIC) ratio > 5 and Area Under Curve (AUC) /Minimum Inhibitory Concentration(MIC) ratio > 125. No therapeutic drug monitoring will be performed in this study.