different concentrations) This experiment was performed by two groups using antibiotics Amoxicillin and Vancomycin by each group. Vancomycin data were collected by our group. After the incubation period of the diluted tubes containing antibiotic Vancomycin against S. epidermidis, the results were obtained as below, Tubes: 1 2 3 4 5 6 7 8 9 10 (Image 1 indicates the visual growth of S. epidermidis for Vancomycin concentrations 100 mg/ml (tube 1), 50 mg/ml(tube 2), 25 mg/ml(tube 3), 12.5 mg/ml(tube 4), 6.25 mg/ml(tube 5), 3.12 mg/ml(tube 6), 1.56 mg/ml(tube 7), 0.78 mg/ml(tube 8), and 0.39 mg/ml(tube 9) respectively. Tube 10 is a control) …show more content…
Tubes 7 – 9 and control tubes showed growth. Minimum Inhibitory concentration (MIC) for Vancomycin was determined 3.12 ug/ml. Amoxicillin tubes showed growth in all 9 tubes and the control tube. Thus, MIC could not be determined for Amoxicillin. After the incubation period of the six plates prepared from using the clear tubes (Vancomycin), the results were obtained as below, Plate 1 Plate 2 Plate 3 (100 ug/ml) (50 ug/ml) (25 …show more content…
epidermidis showed growth only in tubes 7, 8, and 9 after incubation period. Whereas tubes 1 through 6 for concentration between 100 ug/ml to 3.12 ug/ml were observed with no bacterial growth (clear). The minimum concentration at which the growth is inhibited in visual observation was recorded as MIC. This MIC for Vancomycin was 3.12 ug/ml in this experiment. To further examine whether or not the Vancomycin is bactericidal for S. epidermidis and at what concentration, the media plates prepared from the clear tubes in MIC determining step were examined. Among the six concentration plates, only the plates with concentration 50 ug/ml and 100 ug/ml were free of colonies. However, in the image above, 100 ug/ml and 50 ug/ml plates have colony like appearance because water droplets after the incubation period were not wiped out. Upon the observation with open lid, both these plates were seen free of bacterial colonies. Thus, concentration 50 ug/ml at which the bacterial growth is completely killed was the Minimum Bactericidal Concentration (MBC) for Vancomycin against S. epidermidis. Plated with concentrations 25 ug/ml, 12.5 ug/ml, 6.25 ug/ml, 3.12 ug/ml showed colonies and the colony forming units (CFU) were calculated as shown in Table