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18 Cards in this Set
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- 3rd side (hint)
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Lipid soluble drugs like chloramphenicol and metronidazole |
Can penetrate into the CNS |
Lipid solubility of a drug is the major determinant of its ability to penetrate into the brain |
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Whereas Beta lactam antibiotics like penicillin |
Have limited penetration through the intact blood brain barrier under normal circumstances |
In infections such as menigitis in which the brain is inflamed, d barrier does not function as effectively and local permeability is increased, hence some beta lactam antibiotics enter the csf |
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Vancomycin has high molecular weight |
It penetrates poorly into the csf even in the presence of infection |
Compound with a low molecular weight has an enhanced ability to cross the BBB |
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Antibiotics that are concentrated or eliminated by the liver |
Such as erythromycin and doxycycline |
Must be given with caution to patients with liver dysfunction |
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When you increase the concentration of certain antimicrobial agents |
Such as aminiglycoside and daptomycin |
Their rate of bacterial killing increases from 4 to 64 fold |
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Beta lactam antibiotics , macrolides, glycopeptides, clindamycin do not function as effectively when their concentrations are increased |
Rather their efficacy is best when their time in the blood concentration is extended. |
Good girl 😂 |
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Postantibiotic effect is a persistent suppression of microbial growth that occurs after the levels of antibiotic have fallen |
Examples of antimicrobial agents exhibiting a long PAE is aminiglycoside and fluoroquinolones |
They require one dose per day |
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Narrow spectrum chemotherapeutic agents act only on a single or limited group of microorganisms |
Example of narrow spectrum antibiotic is Isoniazid |
It is active against Mycobacterium tuberculosis only |
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Extended spectrum antibiotics is effective against gram positive organisms and also against gram -negative bacteria |
Example of extended spectrum antibiotics is Ampicillin |
It acts against gram positive and some gram negative bacteria |
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Broad spectrum antibiotics example tetracycline, fluoroquinolones and carbapenems |
They affect a wide variety of microbial species |
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It is better to treat patients with a single agent that is most specific to the infecting organism. |
This is to reduce possibility of super infection and minimize toxicity |
However some situations will eventually require combo of antimicrobial drugs |
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Things that can make an organism become resistant to antibiotics |
1. They can change or alter the target site of the antibiotics 2. They can lower the penetrability of the drug by making themselves less permeable 3.they can increase the efflux of the drug 4. They can possess an enzyme which inactivates the antibiotic |
Yay Yay Yay |
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Example of a bacteria changing it's target site is the Streptococcus pneumonia |
S. pneumoniae resist the antibiotic called beta lactam (eg penicillin) by altering the penicillin binding proteins.... This will decrease binding of the antibiotic to its target site |
Penicillin binding proteins is where penicillin bind when they come to function |
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In terms of decreased permeability, gram negative organisms can limit the penetration of some agents like beta lactam antibiotics |
They do this by changing the number and structure of porins(channels) in their membrane |
This will make it hard for the antibiotic to enter and accumulate |
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In the terms of decreased accumulation, some organisms can resist an antibiotic |
This is by promoting the efflux of the drug |
Example is in tetracycline |
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Some organisms can also destroy or inactivate the antimicrobial agent used against them |
This is by 1) beta lactamases is an enzyme that an organism uses to inactivate beta lactam ring of penicillin and cephalosporins 2) some can even transfer an Acetyl group to the antibiotic (using an enzyme called acetyltransferase) this will inactivate organisms like chloramphenicol 3)another mode of resistance is the release of an enzyme called esterase which will hydrolyze the lactone ring of macrolides |
B lactamases, acetyltransferase and esterase |
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Tobramycin an aminoglycoside is contraindicated in pregnancy (teratogenic) |
Erythromycin is metabolized by the liver and should be used with caution in patients with liver impairment |
Gentamicin an aminoglycoside has a long post antibiotic effect especially when given as a high dose every 24 hours |
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Thank |
You |
For reading |
