BIO2071 WEEK 10 REVISION SHEET 1

Week 10 Review Sheet I

Exercise 1 – Disinfectants

1. What does
bactericidal mean? Bacteriostatic? Virucidal? Fungistatic?

2. Why are control
cultures necessary in evaluating disinfectants?

3. What factors can
influence the activity of a disinfectant?

4. Why do
microorganisms differ in their response to disinfectants?

5. What
microorganisms are most susceptible to disinfectants?

EXERCISE 2 – Antimicrobial Agent Susceptibility Testing and
Resistance

1. What is meant by
antimicrobial resistance? Susceptibility?

2. Why are pure
cultures used for antimicrobial susceptibility testing?

3. Would it be
acceptable to use a mixed culture for this test? Why?

4. List three
factors that can influence the accuracy of the test.

5. When performing a
broth dilution test, why is it necessary to include a growth control tube?
A sterility control tube?

EXERCISE 3 – The Entero bacteriaceae (Enteric Bacilli)

1. What does the
term IMViC mean?

2. Why is the IMViC
useful in identifying Enterobacteriaceae? Are further biochemical tests
necessary for complete identification?

3. What diagnostic
test differentiates Proteus and Providencia species from other
Entero bacteriaceae?

4. How is E. coli
distinguished from P. vulgaris on Mac Conkey agar? On a TSI slant?

5. Why is it
important to differentiate glucose nonfermenters from Enterobacteriaceae?

EXERCISE 4 – Streptococci, Pneumococci, and Enterococci

1. Differentiate the
microscopic morphology of streptococci and pneumococci as seen by
Gram stain.

2. What type of
hemolysis is produced by S. pneumoniae?

3. How is S.
pneumoniae distinguished from other streptococci with the same hemolytic
properties?

4. Describe the
hemolysis produced by alpha-hemolytic, beta-hemolytic, and nonhemolytic
streptococci.

5. What type of
hemolysis is displayed by the groupable streptococci that are most pathogenic
for human beings?

EXERCISE 5 – Urine Culture Techniques

1. What is
bacteriuria? When is it significant?

2. How do
microorganisms enter the urinary tract?

3. Why is aseptic
urine collection important when cultures are ordered?

4. List five
bacteria that can cause urinary tract infection.

5. If you counted 20
colonies from a 0.01-ml inoculum of a 1:10 dilution of urine, how many
organisms per milliliter of specimen would you report? Is this number
significant?