Comparison of the minimal inhibitory concentration (MIC) of cefazolin regarding the bacteria isolated preoperatively from the saliva and postoperatively from the sputum. Cefazolin resistant pathogenic, Gram negative bacteria isolated from the saliva pre-operatively, were also grown from the sputum of the postoperative pneumonia patients. The vertical axis of the graphs crosses the x axis at 0.5 mg/L. The antibiotic level of all the sputum samples fell below 0.5 mg/ml. The bars indicate the MIC value of bacteria obtained pre-operative from the saliva. Black bars denote the bacteria that were cultured from both the sputum and the saliva of the same patient.