Antibiotics Flashcards
What are the 3 different ways of using antibioticss?
Guided therapy
Empirical therapy
Prophylactic therapy
What is guided therapy? When is it used?
Giving antibiotics after identifying cause of infection and selecting agent based on sensitivity testing.
Used for mild infections that can wait for testing (48-72 hours)
What is empirical therapy? When is it used?
Best guess therapy based on clinical/ epidemiological acumen. Needs to cover all likely causes.
Used with more severe infection (sepsis, meningitis) when delay in therapy for culture would result in worsening of condition.
What is prophylactic therapy? When is it used?
Preventing infection before it begins
Used in healthy people exposed to high risk of infection or in immunocomprimised individuals
What are ideal charachteristics for antibiotic?
Highly toxic to bacteria causing infection but has limited colateral damage
What problems are associated with antibiotic use?
Resistance, decreasing rate of antibiotic discovery, clostridium difficile
What are the 2 types of antibiotics?
Bactericidal: sterilises infected site by killing bacteria, lysis of bacteria could lead to release of toxins and inflammatory material
Bacteriostatic: suppress growth but don’t sterilise, requires additional factors such as immune system to clear bacteria
Different targets for antibiotics:
Cell wall peptidoglycans, metabolism, DNA, Ribosomes
Different classes of antibiotics (5):
Penicillins (type of Beta-lactams): rapidly kill bacteria, low toxisity, act on peptidoglycans in cell wall so bacteria explode, wide variety
Vancomycin: only work on gram +ve as can’t penetrate gram -ve cell wall, work on cell wall, useful against penicilin resistant bacteria
Doxycycline and clarithromycin: highly concentrated within cells making them useful for intra-cellular pathogens, target ribosomes, useful for both gram -ve and +ve
Ciprofloxacin: target and damage DNA, rapid death, broad spectrum, widespread resistance
Trimethoprim: common reistance, used for non-severe UTI
What are 3 principle mechanisms of antibiotic resistance?
Mutation/ modification of target site
Inactivating enzymes
Limiting access: reduced permeability, increased efflux
What are beta-lactamases?
Bacterial enzymes which attack active penicilin and inactivate it -> cause antibiotic resistance
What part of cell does vancomycin?
Cell wall
(only effective against gram +ve)
What does doxycycline target?
Ribosomes
(gram +ve and -ve)
What does ciprofoxacin target?
Damages DNA
(broad spectrum)
What does trimethoprim work?
Prevents bacteria making essential folic acid
