Answer these questions with a few short sentences, or in dot points. Sometimes d

Question

Answer these questions with a few short sentences, or in dot points. Sometimes diagrams are a good way to answer the question, if so be sure to use labels and explain the diagram. (Generally ,1 mark per fact.)

1. Explain why it can be difficult to interpret the culture findings from a swab taken from a bedsore? (1 marks)

2. What is an extended spectrum b-lactamase? (4 marks )

3. What is the difference between the minimal inhibitory concentration (MIC) and the minimal bactericidal concentration (MBC) of an antimicrobial agent? (3 mark)

4. In disc susceptibility testing, what would happen to the zone diameter if the agar was poured too thinly? Explain your answer.

5. What is meant by surrogate testing of an antimicrobial agent? 2 marks

Explanation / Answer

The bedsore is an open infection. When culture is taken from bedshore in swab, and diagnosed, the result could be confusing as the microbes can be from infection as well as from the surrounding area of wound like the bed etc. There are possibilities of spreading of the infection while taking swab. They are the enzymes produces by some bacteria. These are the enzymes that can break down the antibiotics main active ingredient and makes the microbes to survive against that antibiotic conferring resistance. Till now they are only reported in gram negative bacteria. MIC: It is the minimum concentration of a drug which can actively inhibit the growth of the microorganismto an extent. While the MBC is the lowest concentration where there is no live bacteria visible. Means at bactericidal concentration there is 100% killing while at MIC the growth inhibition is defined like MIC50 or MIC90. If the agar is poured thin, then the drug will diffuse and effect more rapidly against the pathogen, it will lead to the formation of a bigger zone. This could be misinterpretation of actual potency of antibiotic so the result should be rechecked with standard well diffusion assay or microdilution assay. 5. Surrogate testing of an antimicrobial agent is the testing of reliability of MIC of particular drug by checking another same type of srug against a pathogen. Sometimes false result are there especially in case of drugs against S.au. So the surrogate agents used to confirm the MIC. They are class representatives of a group of drug. ex oxacillin MIC or cefoxitin DD are surrogate agents for ?-lactams drugs.

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