Exam 2 Flashcards
(83 cards)
What is the difference between bactericidal and bacteriostatic agents?
Bactericidal agents kill microorganisms rapidly, while bacteriostatic agents only inhibit their growth
Name three factors that limit the efficacy of antibiotics
The speed of action, the sensitivity of the target, and side effects of the antibiotics
Why are antibiotics selective?
Targets are usually metabolites, and they are either impacted in bacteria at doses that do not impact humans, or the target does not exist in the host human cells
What are five ways that bacteria can become resistant to antibiotics?
- synthesis of drug breakdown enzymes
- chemical modification of the drug
- modification of target site
-prevention of access to target site by increasing export of the drug out of the cell
-prevention of access to target site through uptake inhibition
What does the B-lactam ring in B-lactam antibiotics do?
It penetrates the outer membrane of gram-negative bacteria
What is the mechanism of action of penicillins? Name three aspects
It inhibits synthesis of the bacterial cell wall, it binds to penicillin binding proteins, and it is bactericidal
Which four steps are required for bacteridical action of B-lactam antibiotics?
- association with the bacteria
- penetration thorugh the outer membrane and periplasmic space in gram-negative bacteria
- interaction with penicillin-binding proteins
- activation of autolysin
What does autolysin do?
It degrades the murein in bacterial cell walls
How does bacterial antibiotic synthesis lead to resistance?
In certain bacteria with drug addition, there is more synthesis of degrading enzymes, so the more drug is added, the more breakdown enzyme there is
What are the mechanisms of resistance against penicillins (and other B-lactams antibiotics)? Name three
- Alteration of penicillin binding proteins (PBPs) -production of B-lactamases by the bacteria (lyse the antibiotic)
-decreases penetration or increased efflux of antibiotic
What is antibiotic tolerance?
When there is inhibition of a bacterium but not killing
What is the difference between broad and narrow spectrum antibiotics? And what are limited spectrum antibiotics?
Broad spectrum antibiotics are against a wide range of bacteria, while narrow spectrum are only against certain types of bacteria, like gram-positive or gram-negative. Limited spectrum antibiotics only work against a single organism/disease
What would you give with a B-lactam antibiotic to decrease resistance risk?
You would also give beta-lactamase inhibitors, to prevent the bacterium from killing the antibiotic
What are some adverse effects of penicillins?
Includes allergy, diarrhea, rashes, sodium overload, or seizure and renal dysfunction with high dose antibiotics
What are four mechansims of action of antibiotics against bacteria?
Inhibit the synthesis of the bacterial cell wall, lysis of the cell membrane, inhibition of bacterial protein synthesis, affect bacterial metabolism and growth
Why is vancomycin an important antibiotic?
It is often used against gram-positive bacteria that are resistant, also for MRSA, And C. diff, and is often a last-resort antibiotic.
Name several side effects of vancomycin
-rash, renal toxicity, ototoxicity, leukopenia, red man’s syndrome
What are the three outcomes of co-therapy with different antibiotics?
- synergism, there is increased drug effectiveness
- antagonism, the action of one is reduced by the other
- indifference, there is no change in effectiveness of either drug
Why is there a lack of new antibiotic discovery?
Because the time-frame of discovery is too long compared to the time-frame of antibiotic resistance
What are four elements considered in choosing antibiotics?
Microbiological activity
concentration of bacteria at site of infection
how long bacteria remains at the site of infection
the Minimum Inhibitory Concentration (MIC)
How do tetracyclines work?
They inhibit the bacterial protein synthesis and are bacteriostatic
How do sulfonamides work?
They inhibit folic acid synthesis and are bacteriostatic
What are adverse effects of sulfonamides?
Hypersensitivity, hematologic and renal toxicity, photosensitivtiy, drug interactions, and hematopoeitic effects
What are adverse effects of tetracycline?
food drug interactions, GI irritiation, hepatic and renal toxicity, photosensitivity, discoloration of the teeth, and vertigo