11. Antimicrobials Flashcards
How do beta-lactam antibiotics work?
Interfere with the synthesis of the bacterial cell wall peptidoglycan
- Antibiotic binds to penicillin-binding protein on bacteria
- Inhibit the transpeptidation enzyme
- Disruption of bacterial cell wall structure
What are the 3 main sub groups of beta-lactams?
Penicillins
Cephalosporins
Carbapenems
Give examples of penicillins
Phenoxymethylpenicillin
Flucloxacillin
Amoxicillin
Co-amoxiclav
What is co-amoxiclav?
Amoxicillin and clavulanic acid
Give examples of cephalosporins
Cefalexin
Ceftriaxone
Cefuroxime
Cefotaxime
Name some antibacterials that affect bacterial protein synthesis
Tetracyclines
Macrolides
Nitrofurans
How do tetracyclines work?
Following uptake into susceptible organisms by active transport, they act by inhibiting protein synthesis
Give examples of tetracyclines
Doxycycline
Tetracycline
What are the clinical applications of tetracyclines?
Resp tract infections
Acne
Chlamydia
Lyme disease
Who is tetracyclines not suitable for?
Children <12 years
Pregnant and breastfeeding women
Cause staining of developing teeth
How do macrolides work?
Inhibit bacterial protein synthesis by an effect of ribosomal translocation
Give examples of macrolides
Clarithromycin
Erythromycin
Azithromycin
What are the clinical applications of macrolides?
Very similar to penicillin
Also active against atypical respiratory pathogens
What is the most commonly prescribed nitrofuran?
Nitrofurantoin
What is the mechanism of action of nitrofurans?
Works by being reduced to multiple reactive intermediates by nitrofuran reductase inside the bacterial cell
These then attack ribosomal and DNA proteins within the bacteria, as well as inhibit the citric acid cycle
What is nitrofurantoin commonly used for?
UTI
How do quinolones work?
Inhibit topoisomerase II, the enzyme that produces a negative supercoil in DNA and thus permits transcription or replication
Give examples of quinolones
Ciprofloxacin
Levofloxacin
What are quinolones used for?
Very good cover of gram negative organisms, as well as atypical organisms and gram positives
Complicated UTIs
Pseudomonas aeruginosa cover
Gonorrhoea
What are the side effects of quinolones?
Tendinitis +/- rupture
Aortic dissection
CNS effects (convulsions)
What are the example of antibacterial agents that interfere with folate synthesis or action?
Sulfonamides
Trimethoprim
How does trimethoprim work?
Folate antagonist
What are the clinical applications of trimethoprim,?
UTIs - careful when prescribing to reproductive age females
What are the most commonly used antivirals?
Aciclovir (DNA polymerase inhibitors)
Oseltamivir
What are the clinical applications of aciclovir?
Herpes simplex infections
Varicella zoster
