Infection - drug classes and mechanisms GN

Question 1

Prokaryotic?

Answer 1

bacteria

Question 2

eukaryotic

Answer 2

fungi and parasites (protozoa)

Question 3

acellular

Answer 3

viruses and prions

Question 4

Difference with human cells?

Answer 4

without a nucleus
without membrane bound organelles

Question 5

Gram staining process?

Answer 5

1 - primary staining (crystal violet)
2 - mordan application (iodine treatment)
3- decolorisation
4 - counterstaining - safranin

Question 6

Bacterial requirements for growth?

Answer 6

Physical (temp, pH, water)
Chemical nutrients
Oxygen

Question 7

Oxygen bacteria

Answer 7

Obligate aerobes (require 02)
Obligate anaerobes (harmed by 02)
Facultative anaerobes (can grow with or without)

Question 8

Mutualism?

Answer 8

Both bacteria and host benefit

Question 9

Commensalism?

Answer 9

Bacteria benefit without harming the host

Question 10

Parasitism

Answer 10

Bacteria benefits at the hosts expense - leading to infection

Question 11

Antimicrobial?

Answer 11

treats infectious diseases

Question 12

selective toxicity

Answer 12

designed to target specific microorganism with no/minimal damage to host

Question 13

Therapeutic index?

Answer 13

larger the safer
TI = toxic dose/therapeutic dose

Question 14

Toxic dose

Answer 14

Drug level that is toxic for the host

Question 15

Therapeutic dose

Answer 15

drug level to treat/resolve an infection

Question 16

Broad spectrum?

Answer 16

effective against wide range
Used in serious infection - when bacteria unknown
Used for mixed infections
May increase risk of resistance and disrupt normal microbiota

Question 17

Narrow spectrum antibiotics

Answer 17

Target specific types of bacteria
Preffered when causative pathogen identified
Minimise impact on normal micrbiota
Minimise resistance happening

Question 18

Bacteriostatic ?

Answer 18

Inhibit bacterial growth (without killing)
reversible effect
Relies on the immune system to eliminate the pathogen
MBC/MIC ratio is >4

Question 19

Bactericidal?

Answer 19

Actively kill the target bacteria
Irreversible effect
Appropriate in poor immunity
Preffered for severe infections
MBC/MIC ratio is <4

Question 20

antibiotic effectiveness measured 2 ways:

Answer 20

1. Minimal inhibitory concentration
   Lowest drug conc that prevents visible bacterial growth - determine spectrum activity
2. Minimum bactericidal concentration.
   lowest drug concentration that kills the pathogen
   Both expressed as concentrations (mg/ml) or (ug/ml)

Question 21

Which tests measure antimicrobial activity?

Answer 21

Dilution susceptibility tests
Disk diffusion test
The etest

Question 22

Dilution susceptibility tests?

Answer 22

used to determine MIC and MBC values
liquid media inoculated with fixed number of bacteria and increasing drug dose
cultured on agar plates
MIC - lowest drug conc no growth
MBC - lowest drug conc no bacterial colonies

Question 23

Disk diffusion tests?

Answer 23

Assess bacterial susceptibility to antibiotics or resistance.
1. bacterial lawn prepared on an agar plate
Antibiotic impregnated disks placed on agar plate
plate incubated to allow bacterial growth
Antibiotic diffuses from the disk forming a concentration gradient
After incubation. clear zone diameters around antibiotic disks are measured
Diameters compared to reference values corresponding to susceptibility, resistance or intermediate results
Diameter correlates with MIC

Question 24

Wider clear zone?

Answer 24

Bacteria are susceptible to the antibiotic

Question 25

Narrower clear zone?

Answer 25

Bacteria show resistance to the antibiotic

Question 26

The Etest?

Answer 26

Bacteria inoculated on agar plates
E test strips with a gradient of antibiotic concentration are placed on
- After incubation, elliptical zone of inhibition forms around the strip
The MIC is determined where the edge of the inhibition zone intersects with the strip’s gradient

Question 27

Function of cell wall?

Answer 27

Confer protection, give the cell shape, prevents the entry of toxic molecules (antibiotics), protects against osmotic pressure, preventing cell lysis in hypotonic environments