microbiols 2

Question 1

Usually antibiotics are given for 5 to seven days, but this is not empirical. Name two examples where a different length of time is prescribed.

Answer 1

Group A strep for scarlet fever - 10 days

UTI - 3 day s

Question 2

Five percentage of hospitalised patients have an adverse reaction. Give examples.

Answer 2

GI upset
Fever
Rash (for example Stevens Johnson Syndrome)
Renal dysfunciton
Acute anaphylaxis
Hepatitis

Question 3

What do you need to remember when prescribing antibiotics?

Answer 3

Always write down TWO rationales as to why you thought you needed to prescribe antibiotics.

Question 4

What influences what antibiotics do you give the patient? (what’s the mnemonic)

Answer 4

Host characteristics:
Age
Renal function
Pregnancy

CHAOS

Choice of the correct antimicrobial depends upon:
Host characteristics
Antimicrobial susceptibilities
Organism itself 
Site of infection

Question 5

When would you use IV antibiotics?

Answer 5

For serious infection
If patient is not PO
If you need to access the CNS

Question 6

Are narrow spec antibiotics worse than broad spec?

Answer 6

No - they’re not inferior.

Question 7

What is MIC?

Answer 7

The minimum concentration of an antibiotic needed to kill the antibiotic

Question 8

What does the lab compare MIC to?

Answer 8

SLCI method

EUCAST

A number at which the antibiotics work

If the MIC is beyond breakpoint = resistant

Question 9

Treatment timeline

Answer 9

Initially - broad spectrum antibiotics - collect specimens for culture prior to starting antibiotics

Phenotypic testing (48 hours)

Question 10

How does the lab report on bacterial cultures?

Answer 10

Susceptible, or susceptible to optimised dosing, or resistant (but remember resistance is a spectrum)

Question 11

Treatment timeline

Answer 11

Initially - empirical broad spectrum antibiotics based on policy - collect specimens for culture prior to starting antibiotics

Wait for lab to do phenotypic testing (48 hours)

Review and then change to narrow

Question 12

What affects the concentration of antimicrobial at that site of infection?

Answer 12

pH at the site of infection
Lipid solubility of the drug
Ability to penetrate the blood-brain barrier

Question 13

When should you avoid long term IM antibiotics?

Answer 13

If there is a tendency for bleeding

Local irritation

Question 14

When do you give IV antibiotics?

Answer 14

Serious or deep seated infections?

Question 15

When would you avoid PO antimicrobials?

Answer 15

If there is poor GI function or vomiting

Question 16

If the patient has stablised after 48 hours of IV antibiotics, what do you do?

Answer 16

Switch to PO

Question 17

What matters in terms of efficacy of the antibiotic?

Answer 17

It varies

Sometimes, the time of effect is what matters - the time above the MIC concentration

Sometimes it’s the dose

For example Aminoglycosides - you give a peak, and then wait for a trough so you don’t cause toxicity.

beta lactams - maximum time (duration of exposure)

Vancomycin maximum the amount of the drug

Question 18

What matters in terms of efficacy of the antibiotic?

Answer 18

It varies

Sometimes, the time of effect is what matters - the time above the MIC concentration

Sometimes it’s the dose

For example Aminoglycosides - you give a peak, and then wait for a trough so you don’t cause toxicity. Remember if you don’t give high enough a dose, you will still cause

beta lactams - maximum time (duration of exposure)

Vancomycin maximum the amount of the drug

Question 19

N meningitis duration of abx

Answer 19

7 days

Question 20

Acute osteomyelitis

Answer 20

6 weeks

Question 21

Bacterial endocarditis

Answer 21

10 days

Question 22

Narrowest spectrum antibiotic for UTI with e-coli

Answer 22

Amoxicillin