antimicrobial sensitivity Testing Introduction Antimicrobial sensitivity testing is important clinically because the proper selection of an antimicrobial drug in the treatment of a bacterial infection is ideally based on the knowledge of the sensitivities of the infecting organism. In this laboratory exercise you will be working within a group performing a commonly used test that is designed to determine whether or not an isolated organism is able to be treated using a specific antimicrobial drug. The procedure is called sensitivity testing. This testing method allows clinicians to obtain information needed in order to make an informed and concise decision in reference to the antimicrobial drug usage. Methods and Materials Materials being used in this test include: o 6 Mueller-Hinton agar plates o 14 cartridges of antimicrobial drugs o three automatic dispenser so two 1 mL pipettes and pipette pump o broth culture of Staphylococcus aureus and Escherichia coli o spreading rod soaking in ethanol o two forceps soaking in ethanol o marking pe no ruler o antimicrobial sensitivity chart To start off this lab you will 1. Label the plates with the name of the organisms (three plates per organism) 2.
Create a bacterial lawn by a. Inoculate each dish with 0. 2 mL of the appropriate bacteria. Deposit the inoculum in the center of the plate. b.
The Term Paper on Antimicrobial Sensitivity Infection Control
ANTIMICROBIAL RESISTANCE AND JUDICIOUS USE OF ANTIBIOTICS Antibiotics Antibiotics are chemical substances, many of them derived from microorganisms that suppress the growth of other organisms and sometimes kill them. In clinical practice, the antibiotics are used to treat bacteriologically proven infections and also in the prophylaxis of certain diseases. They are sometimes used in the blind or ...
Remove the spreading rod from the ethanol and ignite the ethanol (Do not leave the rod in the Bunsen burner flame longer than is needed to ignite the ethanol. ) Allow the ethanol to burn off. Spread the culture over the entire surface of the plate using the sterilized spreading rod. Before continuing wait five minutes to allow the culture to be absorbed by the nutrient agar. 3. Apply antimicrobial disks to the plate using the dispensers as demonstrated by your instructor.
Gently press the disks to the surface of the agar with a sterile set of forceps. 4. Incubate the Petri dishes for at least 24 hours at 37 degrees Celsius. 5.
Measure the diameter (in mm’s) of region around the disks where growth was inhibited. This region will appear as a clear hallo around the disk and is known as the zone of inhibition. If no clear region is evident record the diameter of the disk itself. Record the zone of inhibition on the provided data sheet. 6. Using the sensitivity chart, determine if the organisms are sensitive, resistant, or fall into the intermediate zone.
If an organism is sensitive to an antimicrobial drug that drug could be used to treat that organism. If it is resistant the drug will not work against that organism. If an organism falls in the intermediate zone the drug should only be used if no other option is available. 7. For each drug determine if it has a broad or narrow spectrum. If it is effective against both E.
coli and s. aureus, the drug would be considered to be broad spectrum. If either or both organisms show resistance to the drug it is considered to have a narrow spectrum. Results In the results of our experiment we found that most of the antimicrobial’s showed a narrow spectrum of activity to the microbes of E. coli and S. aureus.
Ceftizoxime, streptomycin and had a broad spectrum of activity to the microbes. The penicillin derivatives showed a narrow range of activity but also had the only resistance shown. The E. coli was resistant to both the Oxacillin and the Penicillin G.
the S. aureus was totally eradicated by the penicillin derivatives and the. Discussion Finding a narrow spectrum of activity drug for the bacterial infection has a greater effect than that of a broad spectrum drug. Using a drug with an intermediate zone of inhibition may be used but it most likely would not be as successful. If the proper drug is not found and used a microbe is more apt to become resistant to more drugs thus making it more difficult to treat the infection.
The Essay on Drug-resistant Organisms
By the 1960’s, the discovery of antibiotic drugs and subsequent advances in their synthesis led to the conquest of most bacterial diseases, at least in developed countries. In the 1969, the Surgeon General of the United States proclaimed that it was time to “close the book on infectious diseases” (Krasner 29) It indeed seemed so. But today, we confront not only new infectious ...
