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26 Cards in this Set
- Front
- Back
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Name some tetracyclines
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Tetracycline, doxycycline, lymecycline, oxytetracycline
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Mechanism of action of tetracyclines?
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They bind to 30S ribosomal subunit in bacteria and prevent elongation of the peptide chain. This gives them a bacteriostatic effect
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What are the three mechanisms of resistance against tetracyclines?
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1) Expression of efflux pump2) Enzymatic inactivation3) Expression of a protection protein
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What is tigecycline and how is the resistance compared to tetracyclines?
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Tigecycline is not a tetracycline, but similar to them.
Efflux pump and protection protein dont work against tigecycline, so it can be used when there is tetracycline-resistant infections |
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Which tetracyclines can give more GI symptoms?
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Tetracyclines and oxytetracycline
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Why shouldnt tetracycline and oxytetracycline be taken with milk, antacids and iron preparations?
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They form chelates with metal ions and this will decrease their absorption.
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How is the pharmacokinetics of tetracyclines?
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They accumulate intracellularly and extracellularly, can penetrate the placenta and are excreted in breast milk.
They are mostly excreted into the urine or bile in unchanged. |
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What are the adverse effects of tetracyclines?
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1) They may directly irritate GI mucosa and cause ulcers.
2) Photosensitivity 3) Dermatitis from sun exposure 4) Deformities in growing bones and discoloration of teeth in children under 8 years and during pregnacy. Tetracycline forms complexes with calcium. 5) Hepatotoxicity in high doses |
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When are tetracyclines indicated?
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Mostly used for atypical bacteria and intracellular bacteria. Also used against acne.
Borrelia, Mycoplasma, Rickettsia, Chlamydia, Vibrio cholerae. |
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When is Tigecycline indicated?
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Complicated soft tissue and abdominal infections and when there is resistance to first choice antibiotics.
It is effective against MRSA, VRE and penicillin-resistant strep. pneumoniae. |
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What is the mechanism of action of chloramphenicol?
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It binds to 50S ribosomal subunit and inhibits elongation of the peptide chain. It is bacteriostatic against most bacteria, but bacteriocidal against:
H. influenzae and Neisseria |
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How is resistance against chloramphenicol mediated?
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1) Enzymatic inactivation2) Decreased cell envelope penetration
Common among gram+ and gram- |
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How is chloramphenicol metabolized and why can it be a problem?
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It is metabolized in the liver by conjugation with glucuronic acid by the UGT enzyme.
It can lead to grey baby syndrome if a pregnant lady receives chloramphenicol during the last trimester. Neonates have decreased or no UGT activity and chloramphenicol accumulates, causing cyanosis, hypothermia, circulatory shock. |
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Adverse effects of chloramphenicol?
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1) Inhibits mitochrondrial protein synthesis in bone marrow, causing bone-marrow suppression.
2) Irreversible, not dose-dependent aplastic anemia. 3) Grey baby syndrome 4) Oral and vaginal candidiasis. 5) GI-symptoms |
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What is chloramphenicol used for?
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Used as eyedrops in conjunctivitis. No adverse effects when topical.
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Mechanism of action of Clindamycin?
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Binds to 50S ribosomal subunit, inhibiting peptide translocation. Bacteriostatic effect.
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What are the adverse effects of Clindamycin?
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- Diarrhea and Clostridium difficile are much more common with clindamycin.
- Metallic taste - Rashes |
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Clinical use of clindamycin?
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- Against Gram + cocci (not enterococci)
- Against anaerobes - Topically to treat acne. - Systemically to tret soft tissue infections, bone infections, joint infections and abcsesses. |
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Name oxazolidinones
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Linezolid, tedizolid
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Mechanism of action of Oxazolidinones?
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They bind to the 50S subunit of the bacterial ribosome and inhibit protein synthesis at an earlier stage than other antibiotics.
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Adverse effects of Oxazolidinones?
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- Peripheral neuropathy- Bone marrow suppression
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Which side effects can Linezolid cause which is unusual for antibiotics?
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It is a weak monoamine oxidase inhibitor and can cause serotonin syndrome if taken with MAO inhibitors or SSRIs. Can also cause cheese reaction
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What is the clinical use of oxazolidinones?
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Effective against gram+ and mycobacteria. They are effective against multi-resistant bacteria like VRE, MRSA, VRSA and resistant tuberculosis as well.
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Name streptogramins
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Quinupristin, dalfopristin
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Mechanism of streptogramins and why are streptogramins given together?
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Bind to 50S subunit and inhibit elongation of peptide chain.
Given together to yield a synergic reaction, making them bactericidal. |
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What are quinupristin and dalfopristin used for?
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Used for multiresistant infections, like VRE, MRSA and VRSA.
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