Session 4-Antimicrobials Flashcards
What are the different types of antimicrobials? (4)
1) antibacterial
2) antifungal
3) antiviral
4) antiprotozoal
How can antibacterial agents be classified? (4)
1) bactericidal or bacteriostatic
2) spectrum - ‘broad’ vs ‘narrow’
3) target site
4) chemical structure
What is the difference between bactericidal and bacteriostatic?
Bacteriostatic - inhibits growth of bacteria
Bactericidal - kills bacteria
What are the ideal features of antimicrobial agents? (6)
1) selectively toxic
2) few adverse effect
3) reach site of infection
4) oral/IV formulation
5) long half-life
6) no interference with other drugs
What are the four classes of antibacterial and their mechanism of action?
1) cell-wall synthesis
2) cell membrane function
3) protein synthesis
4) nucleic acid synthesis
Which antibacterials affect cell wall synthesis?
Beta-lactams eg penicillins
Glycopeptides
How do penicillins target bacterial cell walls?
Cell wall has penicillin binding protein which forms cross-linked chains. Antibacterial penicillin blocks the binding protein so no cross-linked side chains can form
How does vancomycin act on bacterial cell walls?
It is a glycopeptide antibiotic, prevents chains from cross-linking by blocking the cross-linking enzyme
How do quinolones affect bacterial nucleic acid synthesis?
Inhibits the supercoiling of DNA within the bacteria by inhibiting DNA replication
What are the three types of antibiotic resistance?
1) intrinsic - no target or access for the drug
2) acquired - new genetic material or mutates
3) adaptive - organism responds to stress
True or false: intrinsic and acquired antibiotic resistance are usually reversible
FALSE - permanent, adaptive is reversible
What are the three mechanisms of antibiotic resistance?
1) drug inactivating enzymes
2) altered target - target enzyme has lowered affinity for antibacterial agent
3) altered uptake - decreased permeability or increased efflux
Give examples of drug inactivating enzymes
B-lactamases
Aminoglycoside enzymes
What are the three different types of horizontal gene transfer?
1) conjugation-from one organism to another
2) transduction-bacteriophage
3) transformation-through hole called porin
Which bacteria does penicillin work best against?
Streptococci (most gram positives)
Which bacteria does amoxicillin work best against?
Gram negatives
Which penicillin is active against both staphylococci and streptococci?
Flucloxacillin
Which carbapenem is active against most gram negatives?
Meropenem
Which gram stain bacteria is vancomycin active against?
Most gram positives
Which antibiotic is given if a patient has a penicillin allergy?
Doxycycline (tetracyclines), usually for gram positives
True or false: tetracyclines are active against atypical pathogens in pneumonia and chlamydia
TRUE
Why shouldn’t tetracyclines be given to children under the age of 12?
Stains teeth and bone yellow
What is the most common aminoglycoside and what is its activity against?
Gentamicin
Gram negatives
True or false: aminoglcyosides are potentially nephrotoxic/ototoxic
TRUE
What are aminoglycosides generally reserved for?
Severe gram negative sepsis
What is an example of macrolides?
Erythromycin
True or false: macrolides are used as an alternative to penicillin for mild gram positive infections
TRUE
What is the commonest example of quinolones, what does it inhibit and what is it active against?
Ciprofloxacin
Inhibits DNA gyrase
Active against gram negatives
True or false: quinolones decrease resistance and risk of C. Difficile
FALSE - increase
Which drug is an inhibitor of folic acid synthesis?
Trimethoprim
What is trimethoprim commonly used to treat?
Urinary tract infections
Which antifungal is used to treat Candida?
Fluconazole
Which antiviral, when phosphorylated, inhibits viral DNA polymerase?
Aciclovir
Which drug is an antibacterial and antiprotozoal agent?
Metronidazole
