Antibiotics Flashcards
Name the Fluoroquinolones
- Ciprofloxacin
- Norfloxacin
- Levofloxacin
- Ofloxacin
- Moxifloxacin
- Gemfloxacin
- Enoxacin
What is the mechanism of action for fluoroquinolones?
Inhibits prokaryotic enzymes topoisomerase II (DNA gyrase) and topoisomerase IV which prevents DNA synthesis
Are fluoroquinolones bacteristatic or bactericidal?
Bactericidal
Which antibiotics act on bacterial cell wall synthesis?
- Penicillins
- Cephalosporins
- Carbapenems
- Monobactams
- Glycopeptides
Of the antibiotics which act on cell wall synthesis, which affect on peptidoglycan synthesis?
Glycopeptides
Of the antibiotics which act on cell wall synthesis, which affect peptidoglycan cross-linking?
- Penicillins
- Cephalosporins
- Carbapenems
- Monobactams
What are the beta-lactam antibiotic groups?
- Penicillins
- Cephalosporins
- Monobactam
- Carbapenem
What is the risk of cephalosporin allergy in patients with penicilin allergy?
3 - 7%
What is the risk of monobactam allergy in patients with penicillin or cephalosporin allergy?
0 %
Safe to use in patients with these allergies.
Name the monobactam antibiotic
Aztreonam
In which infections are bactericidal antibiotics preferred and why?
Infections-
* Endocarditis
* Meningitis
* Osteomyelitis
Why-
Immune system has limited access to these infection sites
In which cohorts are bactericidal antibiotcs preferred and why?
Cohorts-
* Severely immunocompromised e.g. patients having high dose chemotherapy
Why-
Immune system unable to manage the infection
Which are the bacteriostatic antibiotics?
- Tetracyclines
- Macrolides
- Chloramphenicol
- Linezolid except against SPPN (bactericidal)
- Rifampicin against Enterococci
- Lincosamides - varies depending on drug conc, bacteria, and bacterial inoculum
How does antimicrobial resistance arise in a microorganism?
- Mutation of cellular genes
- Acquiring exogenous resistance genes
- Mutation of acquired genes
Name the aminoglycosides
- Amikacin
- Gentamicin
- Tobramycin
- Streptomycin
- Neomycin
What makes up an aminoglycoside structure?
- Aminocyclitol ring
plus - 2 or more amino sugars linked by glycosidic bonds
List the key qualities of aminoglycosides
- Hydrophilic
- Positively charged
- Activity is concentration dependent
- Rapidly bactericidal
- Have postantibiotic effect
- Predictable pharmacodynamics
What is the principle target of aminoglycosides
30S ribosome subunit
How do aminoglycosides enter a bacterial cell?
- Positively charged aminoglycoside binds to negatively charged bacterial cell
- Part of aminoglycoside enters cells through energy dependent process
What does aminoglycoside binding to 30S ribosome subunit cause?
Interference with protein synthesis –> cell death
What are the four mechanisms of aminoglycoside resistance?
- Loss of cell permeability –> decreased uptake into cell
- Alterations in the 30S ribosome subunit –> prevents binding
- Expulsion by efflux pumps
- Inactivation by Aminoglycoside Modifying Enzymes (AMEs)
Name the ways bacteria achieve PBP-mediated beta-lactam resistance
- Overproduction of PBPs
- Acquiring foreign PBP with low affinity for beta-lactams
- Recombination of susceptible PBP with more resistant varieties
- Point mutations within PBPs lowering affinity for beta-lactams
What are the two mechanisms of beta-lactam resistance in Neisseria gonorrhoeae
- Beta-lactamase-mediated resistance
- PBP-mediated resistance through recombination between native susceptible PBP and acquired resistant PBP (AKA mosaic PBP genes)
What are mosaic pbp genes?
pbp genes which have undergone recombination i.e. segments of foreign pbp gene have integrated into native pbp gene
