11-12 - Antibiotics & Diagnostic Microbiology

Question 1

Who performs diagnostic microbiology?

Answer 1

Clinical microbiologists

(This may be in hospital labs, reference labs or public health labs- such as Public Health England (PHE))

Question 2

Name 3 types of assay which may be used for diagnostic purposes…

Answer 2

1. Antibody assays
2. Antigen assays
3. Molecular assays

Question 3

Antibiotics are:

a) natural compounds which prevent the growth of microorganisms
b) synthetic compounds which prevent the growth of microorganisms
c) natural or synthetic compounds which prevent the growth of microorganisms
d) natural compounds which prevent the replication of microorganisms

Answer 3

Antibiotics are:

a) natural compounds which prevent the growth of microorganisms
b) synthetic compounds which prevent the growth of microorganisms

c) natural or synthetic compounds which prevent the growth of microorganisms

d) natural compounds which prevent the replication of microorganisms

Question 4

Antibiotic action can be divided into 3 categories. These are…

Answer 4

1. Bacteriostatic
2. Bacteriocidal
3. Bacteriolytic

Question 5

Bacteriostatic antibiotics:

a) Decrease viable cell count
b) Stop further increases in total cell count
c) Decrease total cell count
d) Increase total cell count

Answer 5

Bacteriostatic antibiotics:

a) Decrease viable cell count

b) Stop further increases in total cell count

c) Decrease total cell count
d) Increase total cell count

(static -> stasis/ stop)

Question 6

What is the MIC?

Answer 6

Minimum Inhibitory Concentration

(the minimum concentration required to inhibit bacterial growth)

Question 7

The MIC of an antibiotic can fall under four levels…

Answer 7

1. Sensitive
2. Intermediate
3. Breakpoint
4. Resistant

Question 8

The antibiotic penicillin targets which aspect of bacteria?

Answer 8

Cell wall synthesis

(B-Lactam ring of penicillin binds to active site of transpeptidase enzyme. This enzyme usually forms the cross links needed for the peptidoglycan cell wall. Without it the bacteria can’t synthesise new cell wall.)

Question 9

List potential targets for antibiotics in a bacterial cell (5)…

Answer 9

• Cell wall synthesis
• Protein synthesis (ribosomes)
• Membrane integrity
• Replication and transcription
• Synthesis of essential metabolites

Question 10

Why are the ribosomes a good target for antibiotics?

Answer 10

Prokaryotic ribosomes have 30S and 50S subunits, which are different from the eukaryotic ribosomes in the host cells (60S and 40S subunits)

Question 11

Give an example of an antibiotic that disrupts the integrity of the bacterial membrane…

Answer 11

Daptomycin

Polymixin

Question 12

What can be used to target the synthesis of essential metabolites in bacteria?

Answer 12

Anti-metabolites

Question 13

Sulfonamide is an anti-metabolite which works by mimicking…

Answer 13

PABA

Question 14

How does the antibiotic isoniazid work?

Answer 14

Interefes with the synthesis of the sticky outer protective layer of bacteria (Mycolic acid)