Principles of microbial use

Question 1

To avoid in children:

Answer 1

• Tetracyclines (calcification)

- Fluroquinolones (arthropathy)

Question 2

Avoid in G6PD:

Answer 2

• Sulfonamides
• Cotrimoxazole
• Nitrofurantoin

Question 3

Avoid in penicillin allergy

Answer 3

Have cross reactivity with carbapenems + cephalosporins

Question 4

Avoid in pregnancy/BF:

Answer 4

• Cotrimoxazole
• Fluroquinolones
• Tetracyclines

Question 5

Avoid in renal impairment:

Answer 5

• Aminoglycosides

- High dose vancomycin

Question 6

Avoid in hepatic impairment

Answer 6

• Pyrazinamide

- Amoxicillin/clavulanate

Question 7

Immunocompromised:

Answer 7

Use bacteriostatic drugs

• B-lactam
• Fluroquinolones
• Aminoglycosides
• Vancomycin

Question 8

MSSA

Answer 8

• Penicillinase resistant penicillins (Flucloxacillin, cloxacillin)

Question 9

MRSA

Answer 9

• Vancomycin
• Ceftaroline
• Ceftobiprole
• Tetracyclines
• Glycylcycline
• Clindamycin
• Co-trimoxazole
• Linezolid

Question 10

P.aeruginosa

Answer 10

• Piperacillin
• Ceftazidime
• Ceftobiprole
• Carbapenem (x erta)
• Aztreonam
• FQ
• Aminoglycosides

Question 11

ESBL

Answer 11

• Carbapenem
• Aminoglycosides
• 4th gen cephalosporin

Question 12

Amp-C-producing enterobacterales:

Answer 12

4th gen cephalosporin

Question 13

Anaerobic:

Answer 13

• Carbapenem
• Piperacillin+tazobactam
• Clindamycin
• Metronidazole
• Amoxicillin-clavulanic

Question 14

Enterococcus

Answer 14

Ampicillin + Gentamicin/ Ceftriaxone

Cotrimoxazole

Question 15

Does not achieve adequate CSF conc (AMC)

Answer 15

• 1st & 2nd gen cephalosporin
• Aminoglycosides
• Macrolides
• Clindamycin

Question 16

For CNS infections (all cell wall inhibitor)

Answer 16

• Penicillins
• Ceftriaxone
• Ceftazidime
• Cefepime
• Meropenem
• Vancomycin

Question 17

Prostatitis

Answer 17

• Ciprofloxacin

* Co-trimoxazole

Question 18

To avoid in pneumonia

Answer 18

Daptomycin as it is inactivated by lung surfactant

Question 19

To avoid in abscesses

Answer 19

aminoglycoside as it does not distribute well

Question 20

Good oral F drugs? (FMLC)

Answer 20

• FQ
• Metronidazole
• Linezolid
• Cotrimoxazole

Question 21

General steps to antimicrobial use?

Answer 21

1. Confirm presence of infection
2. Identification of pathogen
3. Selection of microbial regime
4. Monitor response

Question 22

How to confirm presence of infection?

Answer 22

Look at: 
Risk factors for infection
Subjective evidence (symptoms)
Objective evidence 
- Vital signs 
- Lab test 
- Radiological imaging

Question 23

What vital signs to look out for to confirm presence of infection?

Answer 23

Fever >38'C
Tachypnea RR >22bpm 
Hypotension SBP <100mmHg
tachycardia HR >90bpm
Mental status

Question 24

What lab test to look out for to confirm presence of infection?

Answer 24

Non-specific 
E/D total white (4-10 x 10^9/L) 
CRP (>40mg/L)
Increase neutrophils (>90%)
Erythrocyte sedimentation rate (bone & joint) 
Increase procalcitonin

Question 25

Example of colonisers

Answer 25

Yeast in urine

Question 26

What to look out for in radiological imaging

Answer 26

Tissue changes, collections, abscess, obstructions

Question 27

Examples of contaminants?

Answer 27

Staphylococcus epidermis, bacillus spp

Question 28

Advnatge of combination therapy?

Answer 28

1. Extend spectrum of activity o Empirical or definitive therapy of polymicrobial infections  Piperacillin-tazobactam for gram-  Vancomycin for hospital-acquired pneumonia o Empirical tx to cover all resistant strains of the same organism  Piperacillin-tazobactam + ciprofloxacin to cover Pseudomonas aeruginosa in ventilator associated pneumonia 2. Achieve synergistic bactericidal effect o Ampicillin + gentamicin/ampicillin + ceftriaxone for Enterococcus o Trimethoprim + sulfamethoxazole against various organisms 3. Prevent development of resistance o Antimicrobial combinations against M. tuberculosis, HIV

Question 29

Disadvantages of combination therapy

Answer 29

1. Increased risk of toxicity & allergic reactions 2. Increased risk of drug interactions 3. Increased cost 4. Selection of multi-drug resistant bacteria 5. Increased risk of superinfections o E.g. fungal infections CDAD (2nd infection superimposed on earlier on) 6. Concern for antagonistic effect

Question 30

Drug factors?

Answer 30

``` Spectrum of activity Ability to reach the site PK-PD char ROA Side effects DDI Cost ```

Question 31

PK-PD char of drugs?

Answer 31

Conc-dep bacterial killing (AG/FQ) - dep on antibx conc Time-dependent bacterial killing w/ no persistent effect (Penicillins, cephalosporins, carbapenems) - dep on dosing interval 40-70% > MIC Time-dependent bacterial killing w/ persistent effect (Vancomycin) - AUC:MIC ratio