Testing Antibotics On Bacteria Essay Research Paper

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Testing Antibotics On Bacteria Essay, Research Paper Introduction Problem To determine the effect of ten different antibiotics on two different types of bacteria. I will test six antibiotics on Escherichia coli, and six antibiotics on Bacillus subtilis. On Escherichia coli I will test tetracycline, chloramphenicol, furadantin, nalidixic acid, triple sulfa, and kanamycin. On Bacillus subtilis I will test streptomycin, erythromycin, novobiocin, tetracycline, chloramphenicol, and penicillin. As a side observation, I would also like to see if Bacillus subtillis shows resistance to penicillin. The use of penicillin is being reduced because of the resistance many types of bacteria are developing against it. Hypothesis My hypothesis is that penicillin will inhibit the most growth

against Bacillus subtilis, and that tetracycline will stop Escherichia coli more effectively than the others. Rationale I feel that this experiment is valid because it shows how different antibiotics react to different types of bacteria. It also points out the fact that not all antibiotics work the same or that they work at all on all types of bacteria. Materials 1 bottle of tryptic soy agar 1 culture of Escherichia coli 1 culture of Bacillus subtilis 4 sterile petri dishes 1 pack of test discs 2 sterile pipettes 2 tubes of physiological saline 1 forceps 1 wax pencil 2 sterile swabs Method 1. Loosen the cap of the tryptic soy agar to allow it to vent. Place the bottle in a water bath at 100 degrees Centigrade so that the water level reached the level of the medium. The agar will

melt in about 20 minutes. 2. Gradually cool the medium to about 45 degrees Centigrade by letting the water bath cool. Then let the medium sit for 10 minutes. 3. Pour two plates for each species of bacteria. The agar should be approximately 5 mm deep. Cover each petri dish immediately after poring to prevent contamination. 4. After pouring the plates, allow the agar a few minutes to solidify. You can check this by tilting the plate. If the agar flows to one side, more cooling time is needed. 5. Add a tube of physiological saline to each of the bacteria culture tubes. Replace the top on the saline tube. Swirl the culture tube to disperse the bacteria in the saline. 6. Using a sterile pipette, transfer 0.25 ml of saline from one bacterial tube onto each of the two plates. With a

sterile swab, spread the saline in a thin layer over the entire agar surface. Repeat with the other bacterial tube and plates, using a pipette and swab. Allow 5 to 10 minutes for the liquid to be absorbed into the agar. 7. Use the wax pencil to label each dish so that you will know what species it contains. 8. When the agar has solidified, the antibiotic test discs can be added. Using a forceps flamed between each operation place one of each type of test disc on the surface of each agar plate. The discs should be placed about 3 cm apart. The antibiotic on each disc should be identified by the following abbreviations: S=Streptomycin, E=Erythromycin, N=Novobiocin, T=Tetracycline, C=Chloramphenicol, P=Penicillin, F=Furadantin, Na=Nalidixic acid, Ts=Triple sulfa, K=Kanamycin 9. After

the cultures have been in the incubator for 48 hours. Remove them and check around each disc for an area where the bacterium could not grow. Measure each grow area in millimeters and record them on a table ( see table 1). Literature Search Escherichia is a genus of rod-shaped bacteria, in the family Enterobacteriaceae. Named for Theodor Escherich (1857-1911), a German bacteriologist, the only species, Escherichia coli, is found in large numbers as a normal inhabitant of the large intestine of warm-blooded animals. Whenever they leave their usual habitat, these organisms can cause urinary-tract infections, peritonitis, endocarditis, and other diseases. Some strains cause severe gastroenteritis. E. coli has been widely used as a model in molecular biology studies. Certain rare