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Antimicrobials
Microbiology ppt 1 - Antibiotics
| Question | Answer |
|---|---|
| What are antimicrobials? | Agents used to inhibit or kill microbes/organisms. |
| Pharmacodynamics | What the drug does to the body |
| Pharmacokinetics | How your body processes the drug |
| Bacteriostatic | Antimicrobial's that inhibit the growth rate of an organism but generally do not kill the organism. |
| Bactericidal | Antimicrobial's that usually kill target organisms. (Effective for individuals with compromised immune systems) |
| Spectrum of activity | Types of bacteria that agent does (and does not) have activity against |
| Classes of drugs that inhibit cell wall synthesis | Beta Lactams, Glycoproteins, Lipoglycopeptides & Bacitracin |
| Specific antibiotic groups belonging to Beta Lactam | 1- Penicillin's (ex - amoxicillin & ampicillin, Gram +) 2 - Cephalosporins (ex - cefazolin & ceftriaxone, Gram +/-) 3 - Carbapenems (ex - imipenem, gram +/-) 4- Monobactams (ex - aztreonam) |
| Are Beta Lactam drugs toxic to humans? | Not toxic to humans and good bacterial coverage |
| Beta Lactams: Mechanism of action | Beta Lactam ring of the antibiotic binds to the PBP of the organism. PBP is required for cell wall synthesis - lack of available PBP results in cell wall destruction. |
| Organism resistance mechanisms to Beta Lactams | 1 - Organism production of beta lactamase enzyme - binds to beta lactam drug and hydrolyzes. 2 - Gene Mutation - Altered microbial target. Making Beta Lactamase unable to bind to PBP. |
| Class of Drugs that inhibit cell membrane function | Polymyxins & Daptomycin |
| Specific antibiotics of Glycopeptides/Lipoglycopeptides drug class | Vancomycin & teicoplanin |
| Glycopeptides function | Binds to precursors of cell wall -> interfere with ability to PBP's to incorporate precursors of growing cell wall (transpeptidation) -> cell growth stops. -Because glycopeptides are large, they cannot penetrate outer membrane of most gram negatives. |
| What is a good alternative to Beta Lactams? | Glycopeptides, ex- Vancoymycin They are not affected by Beta-lactamases of gram positives. Must be monitored for potential toxicity. |
| Which organism has a high level resistance to Vancomycin? | High level resistance in Enterococcus spp. is common. |
| Bacitracin function | Inhibits recycling of some metabolites required for peptidoglycan synthesis. TOPICAL AGENT ONLY. -Micrococcus spp. and Streptococcus pyogenes are susceptible |
| Specific antibiotics that fall under Polymixins | -Polymixin B and Colistin |
| Function of Polymixins | Increase cell permeability by interacting with phospholipids in bacterial cell membrane -> leakage of macromolecules and ions essential for cell survival -> death -Good against gram negatives |
| Polymixins toxicity | -Toxicity risk because humans have cell membranes as well as bacteria, they're attracted to the phospholipids. -Neurotoxic, nephrotoxic. -Agent of last resort for P. aeruginosa & Acinetobacter spp. that are resistant to all other available microbials. |
| Classes of drugs that inhibit protein sythesis | -Aminoglycocides -MLS (Macrolide - Lincosamide - Streptogramin Group) -Tetracyclines -Ketolides etc |
| Specific antibiotics that fall under the Aminoglycosides drug class | -Gentamicin -Tobramycin -Streptomycin -Kanamycin -Amikacin |
| Aminoglycosides' function | -Bactericidal -Effective on a wide variety of aerobic gram neg and some gram pos (S. aureus) -Not effective against anaerobes. -Not effective alone against Enterococcus spp. -Often used in combination with cell-wall active agent. |
| Microbial resistance to Aminoglycosides | Enzymatic -Gram +/- - Produce several different enzymes which catalyze alteration of aminoglycosides. Decreased update: Porin alterations (Gram -) |
| Which antibiotic is used for penicillin allergic patients? | Erythromycin |
| MLS (Macrolides - L-S) antibiotics | Erythromycin, clarithromycin & azithromycin -Good for gram positives, mycoplasmas, rickettsiae & treponemes -Low toxicity |
| MLS (M -Lincosamides - S) antibiotics | Clindamycin & lincomycin -For gram positive cocci -Anaerobic infections (bacteriostatic), deep tissues (ex - bone, bone marrow) |
| Clindamycin use is associated with ... | C. difficile pseudomembranous colitis |
| Tetracyclines uses | -Broad spectrum (works against gram neg & pos) -Usually effective against Neisseria gonorrhoeae |
| Disadvantages of Tetracycline | -oral/vaginal thrush -Damage to bones and teeth of kids <3 years -Liver damage after large doses -Nausea, vomiting, esophageal ulcers etc. |
| Classes of drugs that inhibit DNA/RNA synthesis | Fluoroquinolones, Metronidazole & Rifamycins |
| Antibiotics that fall under Fluoroquinolones/quinolones | Ciprofloxacin, ofloxacin & norfloxacin -Bactericidal -Tendonitis toxicity -Broad spectrum but varies with each agent |
| Ciprofloxacin is commonly used to treat? | UTI's |
| Antibiotics that fall under Rifamycins | Rifampin (Binds to RNA Polymerase) -Better against gram positives than negatives. - Resistance (altered target) can develop quickly due to spontaneous mutations -> only use in conjunction with other antimicrobials, eg. TB Treatment |
| Classes of drugs that inhibit other metabolic processes | Sulfonamides, Trimethoprim & Nitrofurantoin |
| Nitrofurantoin uses | UTI only |
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