Microbiology Lab Report – Antibiogram

LAB REPORT 8- Selected
questions from Exercise 7-2 ( antibiogram, etc.)
Note: Results for this
exercise would include explanations of the Kirby-Bauer and E test i.e. what is
the purpose, how are they set up. What
kinds of results did you observe for each type of assay?
Drawings can be of
help. Minimally you should see the
Kirby-Bauer assay demonstrated.

A
table is provided below to make it possible for you to interpret the data you
obtain from the observed Kirby-Bauer plates.
You should be able to say who is resistant, sensitive or has
intermediate resistance.

NOTE: Arrows on chart on next
page do not apply this semester (i.e. have to substitute Streptomycin for
ampicillin.)
S.
aureus (diameter in mm) E. coli
(diameter in mm)
S
10 mcg/ml
E
15 mcg/ml
P
10 mcg/ml
Te
30 mcg/ml
C
30 mcg/ml

(Note:
mcg = micrograms)

Q1.
Generally speaking, are antibiotics are good to use to treat virus infections?
Explain why or why not.
Q2.
What is the benefit of using Mueller-Hinton medium in a Kirby-Bauer assay
instead of media such as nutrient agar or tryptic soy agar?
Q3.
What is a beta lactam antibiotic? What
is the function of the enzyme beta lactamase?
Where are beta lactamases found in a bacterial cell are they typically
intracellular or extracellular (secreted) enzymes?
Q4.a)What
does the abbreviation MIC stand for?
Provide a brief explanation of its relevance to bacterial drug
resistance.
b)Explain
what an E-test is and how it can be used to determine a MIC for a bacterial
organism.
c)Using
the text, are there other tests that can be used to determine a MIC for a
bacterial organism?

Note:
For exam, it may be of use to know: i) what is a monobactam & why/when is
it used?
ii)
what is clavulanic acid & how/ why is clavulanic acid used iii) how can one
relatively easily test for the ability of a bacterial cell to produce a beta lactamase? (In this case, you may have to look up this
answer by Googling, etc. sometimes we
get to do a demonstration so be on the lookout.) iv)Typically, what kind of genetic element
carries the gene for beta lactamases is it on the chromosome, on a plasmid,
etc.? Can it be associated with
transposons? v)think about how this relates to R factors and superbugs. Vi)
Excluding the situation with respect to allergies, is penicillin usually
considered to be nontoxic to humans? Explain your answer. Vii) The antibiotics referred to above as S,
E, Te and C all have the same cell target. What part of the cell do these antibiotics
bind to? What process do they inhibit?

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