Principles of microbial use Flashcards
To avoid in children:
- Tetracyclines (calcification)
- Fluroquinolones (arthropathy)
Avoid in G6PD:
- Sulfonamides
- Cotrimoxazole
- Nitrofurantoin
Avoid in penicillin allergy
Have cross reactivity with carbapenems + cephalosporins
Avoid in pregnancy/BF:
- Cotrimoxazole
- Fluroquinolones
- Tetracyclines
Avoid in renal impairment:
- Aminoglycosides
- High dose vancomycin
Avoid in hepatic impairment
- Pyrazinamide
- Amoxicillin/clavulanate
Immunocompromised:
Use bacteriostatic drugs
- B-lactam
- Fluroquinolones
- Aminoglycosides
- Vancomycin
MSSA
• Penicillinase resistant penicillins (Flucloxacillin, cloxacillin)
MRSA
- Vancomycin
- Ceftaroline
- Ceftobiprole
- Tetracyclines
- Glycylcycline
- Clindamycin
- Co-trimoxazole
- Linezolid
P.aeruginosa
- Piperacillin
- Ceftazidime
- Ceftobiprole
- Carbapenem (x erta)
- Aztreonam
- FQ
- Aminoglycosides
ESBL
- Carbapenem
- Aminoglycosides
- 4th gen cephalosporin
Amp-C-producing enterobacterales:
4th gen cephalosporin
Anaerobic:
- Carbapenem
- Piperacillin+tazobactam
- Clindamycin
- Metronidazole
- Amoxicillin-clavulanic
Enterococcus
Ampicillin + Gentamicin/ Ceftriaxone
Cotrimoxazole
Does not achieve adequate CSF conc (AMC)
- 1st & 2nd gen cephalosporin
- Aminoglycosides
- Macrolides
- Clindamycin
For CNS infections (all cell wall inhibitor)
- Penicillins
- Ceftriaxone
- Ceftazidime
- Cefepime
- Meropenem
- Vancomycin
Prostatitis
- Ciprofloxacin
* Co-trimoxazole
To avoid in pneumonia
Daptomycin as it is inactivated by lung surfactant
To avoid in abscesses
aminoglycoside as it does not distribute well
Good oral F drugs? (FMLC)
- FQ
- Metronidazole
- Linezolid
- Cotrimoxazole
General steps to antimicrobial use?
- Confirm presence of infection
- Identification of pathogen
- Selection of microbial regime
- Monitor response
How to confirm presence of infection?
Look at: Risk factors for infection Subjective evidence (symptoms) Objective evidence - Vital signs - Lab test - Radiological imaging
What vital signs to look out for to confirm presence of infection?
Fever >38'C Tachypnea RR >22bpm Hypotension SBP <100mmHg tachycardia HR >90bpm Mental status
What lab test to look out for to confirm presence of infection?
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
Example of colonisers
Yeast in urine
What to look out for in radiological imaging
Tissue changes, collections, abscess, obstructions
Examples of contaminants?
Staphylococcus epidermis, bacillus spp
Advnatge of combination therapy?
- 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 - Achieve synergistic bactericidal effect
o Ampicillin + gentamicin/ampicillin + ceftriaxone for Enterococcus
o Trimethoprim + sulfamethoxazole against various organisms - Prevent development of resistance
o Antimicrobial combinations against M. tuberculosis, HIV
Disadvantages of combination therapy
- Increased risk of toxicity & allergic reactions
- Increased risk of drug interactions
- Increased cost
- Selection of multi-drug resistant bacteria
- Increased risk of superinfections
o E.g. fungal infections CDAD (2nd infection superimposed on earlier on) - Concern for antagonistic effect
Drug factors?
Spectrum of activity Ability to reach the site PK-PD char ROA Side effects DDI Cost
PK-PD char of drugs?
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
