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Antimicrobials
Micro MLS
| Term | Definition |
|---|---|
| Bacteriostatic | do not kill but inhibit growth |
| bactericidal | kill target organism |
| mode of action | how it attacks the target |
| spectrum of activity | broad vs narrow, types of organism activity against |
| Common targets | Cell wall synthesis, cell membrane function, protein synthesis, dna and rna synthesis, folic acid pathway |
| beta-lactams affect: | cell wall synthesis, broad spectrum as a class |
| beta-lactam interferes with production of | peptidoglycan |
| penicillin | beta-lactam, natural or semisynthetic, most gram + and many gram - and anaerobic |
| natural penicillins | penicillin G and V |
| Penicillin G | Given by injection, unstable in stomach |
| Penicillin V | taken orally |
| penicillinase resistant, Semisynthetic penicillin (two) | methicillin, oxacillin |
| extended spectrum, semisynthetic penicillin (four) | ampicillin, amoxicillin, ticarcillin, piperacillin |
| Cephalosporins | beta-lactam cell wall synthesis |
| 1st Gen Cephalosporins example and effective against | Cephalothin (Keflin), penicillinase producing and methicillin susceptible staphs and stretococci Gram +, NOT for MRSA or enterococci, and effective against a few gram - (proteus mirablis and klebsiella pneumoniae |
| 2nd Gen Cephalosporins example and effective against | Cefuroxime, Cefotetan, Cefoxitin, Less active against gram + than 1st gen, more active against gram - than 1 st gen |
| 3rd Gen Cephalosporins example and effective against | Ceftriaxone (Rocefin), Cefotaxime, some decreased vs. gram + broader spectrum and further increased activity against gram negatives. Used for hospital acquired infections, meningitis and gonorrhea |
| 4th Gen Cephalosporins example and effective against | Cefepime (Maxipime), gram + similar activty to 1st gen (penicillinase producing and methicillin susceptible staphs and stretococci Gram +) Gram - Better penetration of outer membrane and greater resistance to beta-lactamases than third generation. |
| 5th Gen Cephalosporins example and effective against | Ceftaroline (Fosamil) Anti-MRSA, effective against many other gram positive organisms Not indicated for gram negative organisms |
| Anatomic Distribution for Norfloxacin and Nitrofurantoin | Does not reach serum-blood or CSF. Only effective against urinary tract infections. |
| Monobactams use and ex | Cell Wall Synthesis: Beta-Lactam, Binds to PBP3 of gram negative organisms. Aztreonam is the only one currently approved for use |
| Carbapenems mode of action | Cell Wall Synthesis: Beta-Lactams. Bind to PBP1 & PBP2 Widest spectrum of activity of currently available antibiotics. |
| Carbapenems ex. (2) | Imipenem, meropenem |
| Beta-lactamase Inhibitors | Not active as antimicrobials themselves. Can be used to inhibit beta-lactamase enzymes which cleave the β-lactam ring. paired w/ antibiotic |
| Beta-lactamase Inhibitors ex. and antibiotic pair (3) | Sulbactam (ampicillin) Clavulanate (amoxicillin) Tazobactam (piperacillin) |
| Glycopeptides | Cell Wall Synthesis: Prevents cell wall precursors from being incorporated. Too large to work on gram +. Used to treat MRSA and for serious staph infections in patients who are allergic to penicillin |
| Glycopeptides ex | Vancomycin |
| Bacitracin | Disrupts cell wall synthesis by interfering with a phosphorylation reaction involved in peptidoglycan synthesis. Only applied topically. Effective against staph & group A strep |
| Lipopeptides | Plasma Membrane Function. disrupts cell membrane of gram positive organisms. Use VRE, MRSA, VRSA |
| Lipopeptides ex. | Daptomycin |
| Polymyxins | Plasma Membrane Function. increase permeability and disrupt osmotic integrity of both outer andplasma membranes – Active only against gram-negative rods Last resort against Pseudomonas and Acinetobacter. |
| Polymyxins ex (2) | Polymyxin B, Colistin |
| Aminoglycosides ex (5) | Gentamicin, tobramycin, amikacin, streptomycin, neomycin |
| Aminoglycosides use | Inhibit protein synthesis by binding to the 30S ribosomal subunit. Broad spectrum Used most frequently against aerobic gram negative rods and S. aureus. used with B-lactams or vancomycin which facilitate uptake. Not effective against anaerobes. |
| Macrolide-lincosamide-streptogramin (MLS) group. | Protein synthesis. bind to 50s ribosomal subunit. Most gram positives, some gram negative. |
| Macrolide-lincosamide-streptogramin (MLS) exs. | Erythromycin, azithromycin (M) Clindamycin (L) Quinupristin, dalfopristin (S) |
| Ketolides ex (1) | Telithromycin. Only approved for use in moderate to severe cases of community acquired pneumonia by erythromycin resistant Streptococcus pneumoniae |
| Oxazolidinones EX and use | Linezolid. Protein Synthesis - Prevention of mRNA translation. Used for gram positive bacteria and mycobacteria Inactive against most gram negative organism |
| Chloramphenicol | Protein Synthesis. Binds to the 50S ribosomal subunit, Bacteriostatic – Broad spectrum but bone marrow toxicity is problematic – Used for seriously ill patients - meningitis |
| Tetracyclines ex and use | Doxycycline. Block tRNA/amino acid complexes from binding to ribosome at the 30S ribosomal subunit. Broad spectrum |
| Glycylcyclines ex and use | Tigecycline. Similar action to tetracycline but with less incidence of resistance |
| Fluoroquinolones (quinolones) | Bind to and interfere with DNA gyrase and other topoisomerases. Regulate DNA supercoiling. broad spectrum as a group. |
| Fluoroquinolones (quinolones) ex (4) | Ciprofloxacin, ofloxacin, nalidixic acid, levofloxacin |
| Metronidazole | DNA & RNA Synthesis. Uncertain activity, appears to break DNA strands. Anaerobes, protozoan parasites. |
| Rifampin | DNA & RNA Synthesis. Binds to RNA polymerase preventing RNA synthesis – Used in combination therapy against gram positives (clindamycin, doxycycline) – Enteric pathogens (Salmonella) – Mycobacteria, Legionella |
| Sulfonamides | Folic Acid Pathway. Dihydropteroate synthase is inhibited - Broad spectrum except Psudomonas |
| Trimethoprim | Folic Acid Pathway. Dihydrofolate reductase is inhibited |
| Bactrim (SXT) | Folic Acid Pathway. Frequently used in combination |
| Folic Acid Pathway antimicrobials function | Inhibition of enzymes in the pathway which produces precursors for DNA synthesis |
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