14. Bacteriology & Antimicrobial Resistance

Question 1

Good specimen collection: ALWAYS take sample from _________ _______.

Answer 1

Infected material
- aka sample the pus, not the cells beside the pus

Question 2

What are the different types of solid media?

Answer 2

1. Non-selective
2. Selective
3. Differential

• what is the diff between 2 & 3

Question 3

Sample is collected on..

Answer 3

Rayon-tipped swab

• cotton swab is not good, can be toxic to bacteria, organism doesnt survive well on it

Question 4

Sample is stored in what transport media usually?

Answer 4

Amies gel, liquid based
- ensures bacteria viability

Question 5

MacConkey agar inhibits growth of _________ & pink colonies ferment ________

Answer 5

• inhibits growth of gram +ve bacteria
• ferments lactose

Question 6

Lowestein-Jensen medium for

Answer 6

Mycobacterium TB

Question 7

How does resistance in antimicrobials occur?

Answer 7

Mutation
1. Intrinsic
2. Acquired
- plasmids: may carry multiple resistance determinants
- transposons: small units of DNA, dont need conjugation to transmit
- integrons: bigger DNA pieces, can contain transposons n other genes

Under selection pressure
- resistant survivors persist

Question 8

What are the 6 mechanisms of which antibiotics resistance occurs?

Answer 8

1. Target site modification
2. Cell wall permeability (loss of porin channels in gram -ve)
3. Efflux pumps
4. Enzymatic inactivation
5. Target bypass
6. Overproduction of target

Question 9

What does MIC stand for:

Answer 9

Minimal inhibitory concentration
- minimum concentration required to suppress bacteria
- if MIC is higher than max conc body can take, then bacteria is restant

Question 10

What are the 3 methods of testing MIC?

Answer 10

1. Disk diffusion
2. Broth microdilution
3. Etest