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11 Cards in this Set

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What are the three categories of resistence?
1. Natural or Inherient Resistence
2. Mutational and Secondary resistence
3. Transferable resistance
Natural resistence
Is chromosomally mediated and predictable
What are three reasons for natural resistence?
1. The organism lacks the structure the antibiotic inhibits ie Mycoplasms lack PG and are therefore resistant to penicillin
2. The organism is naturally impermeable to the antibiotic ie G- cannot take up penicillin G
3. The organism is able to alter the antibiotic rendering it inactive
Mutational resistance vs. Secondary resistance
Both result from mutations but secondary resistance occurs after therapy w/ the antimicrobial in question has begun.
Transferable Resistance
Drug resistance can in many cases be transferred from one organism to another. THis occurs by transfer of genetic info frim in organism to another by conjugation, transduction, or transformation. MOST MEDICALLY RELEVANT
What are three mechanisms of resistance?
1. Inactivation of Drug
2. Efflux pumps
3. Modify the target
What are three examples of inactivation of drugs?
1. The enzymatic hydrolysis of the beta-lactam ring of the penicillins and cephalosporins
2. Acetylation of chloramphenicol
3. The addition of various substituents to certian sites on the aminoglycoside antibiotics.
What does Beta- Lactamase do?
Cleves the B-lactam ring
What does CAT do?
Puts an OH group on or acetylates chloramphenicol.
What are three ways aminoglycoside are inactivated?
1. Acetylation
2. Phosphorylation
3. Adenylation
Where do resistant mechanisms originate?
From the organisms that produce the antibiotics.