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What are the five Protein Synthesis Inhibitors?
Buy AT 30, CEL (sell) at 50
→ Aminoglycosides, Tetracyclines work at the 30s subunits
→ Clindamycin, Erythromycin (macrolide), and Linezolid work at the 50s subunits
What are Aminoglycoside mechanism of action?
Aminoglycosides exhibit concentration dependent-bactericidal effects due to its irreversible binding
→ Irreversibly inhibit the 30s ribosomal subunit by either blocking initiation of protein synthesis, blocking further translation, or incorporating incorrect amino acids into a sequence
What are the pertinent pharmacokinetics associated with Aminoglycosides
Aminoglycosides are only given via Intravenous or Intramuscular injections
→ Aminoglycosides concentrate highest in the renal cortex and inner ear, contributing to toxicities in these parts (Nephrotoxicity and Ototoxicity)
Describe the concentration-dependent effects of Aminoglycosides
Aminoglycosides exhibit concentration dependent killing - or when their concentration is above the minimum inhibitory concentration
→ as the concentration of the drug rises so does the rate of bacterial killing increase
Aminoglycosides will also exhibit a significant post-antibiotic effect where there is persistent suppression of bacterial growth even when levels drop below the MIC
What is the spectrum of treatment for Aminoglycosides
Aminoglycosides primarily treats Aerobic gram negative bacilli
→ typically pseudomonas
Limited spectrum against gram positive organisms
Aminoglycosides cannot kill anaerobes because it can only penetrate the cytoplasmic membrane in an aerobic energy dependent process
What is the mechanism of action for Tetracyclines?
Tetracyclines
→ inhibit bacterial protein synthesis by reversibly binding to the 30s ribosomal subunit at the site of attachment for tRNA
What are the six kinds of organisms that Tetracycline can treat
Covers both gram positives and gram negatives very well
→ MRSA and other gram positives
→ resistant gram negatives
→ Anaerobes
→ “Atypical” Pneumonia (Mycoplasma, Legionella, and C. pneumoniae)
→ Rickettsiae, Borrelia
→ Some Protozoa
What are the most important side effects associated with tetracyclines? (3)
There are a few pertinent side effects associated with tetracyclines:
→ Skin: Phototoxic reaction - cause you to have a really bad sunburn
→ Can cross the placenta and accumulate in fetal bones, limiting growth (contraindicated in pregnancy)
→ Tooth discoloration in kids
What is Linezolid and what is its mechanism of action
Gram Positive only antibiotic
→ Methicillin Resistant Staph Aureus, streptococci, enterococci, and some mycobacteria
→ distributes well into tissues
Blocks initiation of protein synthesis by interfering with the formation of the initiation complex via binding to the 50s ribosomal subunit
What are the harmful side effects of Linezolid
Leukopenia and serotonin syndrome
→ serotonin syndrome
What is the mechanism of action of Macrolides?
Macrolide
→ reversibly binds to bacterial 23S ribosomal RNA of the 50s ribosomal subunit - inhibits protein synthesis
What are the primary indications for using Macrolides?
Best antibiotic in usage for “atypical” or fastidious pneumonia
→ Mycoplasma, Legionella, C. pneumoniae
→ used quite often in upper and lower respiratory infections, so there is resistance against this very commonly
→ Also used in Bordetella pertussis
What is Clindamycin mechanism of acition?
Inhibits protein synthesis by binding at the 50s ribosomal subunit
When is Clindamycin used
Primarily used to treat gram positive organisms such as MRSA
→ has no activity against aerobic gram negative bacteria
What are the adverse reactions for Clindamycin?
Clindamycin can cause strong Gastrointestinal issues and overgrowth of Clostridium difficile leading to further GI issues
What is the Eagle Effect?
Eagle Effect describes the lack of efficacy of beta-lactam antibiotics on infections with large numbers of bacteria
→ this is because penicillin and related drugs only work when bacteria are actively growing and dividing
→ when an infection is so great, they might all be in stationary phase so no bacteria are really being killed
→ so you would add an antibiotic like clindamycin, which acts on ribosomes, before adding beta-lactams
What is the Fluoroquinolone mechanism of action
Fluoroquinolone
→ binds to DNA gyrase and topoisomerase IV inhibiting DNA synthesis
What is the spectrum of Fluoroquinolones
Antibiotics that are used to treat Gram negative: aerobic gram negative bacilli
→ the only oral antibiotic that can treat pseudomonas aeruginosa
Gram positive
Mycobacteria
Atypical Pneumonia
What are the most important adverse effects associated with Fluoroquinolones?
Tedinopathy and Cartilage Injuries
What is Rifampin?
Antibiotic that inhibits mRNA synthesis of bacteria by blocking DNA dependent RNA polymerase
→ a strong inducer of cytochrome p450 enzymes, causes an increase in elimination of other drugs
→ used in tuberculosis therapy
→ typically always used in combination with other drugs in order to prevent resistant mutants
What are the most important side effects of Rifampin?
Orange urine, tears, and sweat
→ at toxic levels, similar to all cytochrome p450 inducers, it can cause hepatitis and jaundice
What is Metronidazole?
Antibiotic that works by using bacterial nitroreductase which will reduce Metronidazole
→ causes the creation of a free radical that produces damage within the bacteria
→ used to treat anaerobic bacteria
What is the most common side effects of Metronidazole
Causes a metallic taste in their mouth as well as a Disulfiram-like reaction with alcohol
What are Antimetabolites?
Antibiotics that compete with p-aminobenzoic acid, preventing the synthesis of folic acid required by bacteria
→ includes Trimethoprim and sulfamethoxazole
What is Trimethoprim
A Inhibitor of folic acid synthesis by competitively inhibiting dihydrofolate reductase
→ blocks conversion of folic acid to folinic acid which is needed for purine synthesis and ultimately DNA synthesis
What is the spectrum of activity for Trimethoprim and sulfamethoxazole?
Effective against gram positive and gram negative organisms
→ good at fighting Listeria
What are the adverse effects of Trimethoprim-sulfamethoxazole?
Hypersensitivity
→ Stevens-Johnson Syndrome a Type IV hypersensitivity - looks like severe burns across the body and extends onto mucosal membranes
Nephrotoxicity
Displaces unconjugated fetal bilirubin
→ contraindicated in 3rd trimester pregnancy and newborns
What is Pyrazinamide? What is the adverse effect?
Converted to active form pyrazinoic acid by myobacterial enzymes
→ active drug will be taken up to macrophages and acts against mycobacteria that are hiding within the lysosome
→ has hepatotoxicity (worst one)