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test 4 notes 6 - Antibacterial/Antimycobacterial Therapy...

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Antibacterial/Antimycobacterial Therapy Antibacterial and Antimycobacterial Therapy A wide variety of antimicrobial agents are available to treat bacterial and mycobacterial infections. While these drugs are responsible for a significant decrease in morbidity and mortality from infections, overuse has contributed to the development of resistant microorganisms. These drugs should be used wisely. The following agents will be discussed in this section. Penicillins Cephalosporins Flouroquinolones Lincosamides Macrolides and Azalides Oxazolidinones Sulfonamides Streptogramins Tetracyclines Vancomycin Aminoglycosides Metronidazole Antimycobacterials Types of Penicillin The penicillin family includes narrow-spectrum, broad-spectrum (called aminopenicillins in this section) and extended-spectrum penicillins (called antipseudomonals in this section). There are two classes of narrow-spectrum penicillins. The first is called the penicillinase- sensitive penicillins. The second narrow-spectrum class is called the penicillinase-resistant penicillins (or the anti-staphylococcal penicillins). PENICILLINASE-SENSITIVE PENICILLINS - penicillin G o benzathine penicillin (Bicillin) (Permapen) o potassium penicillin G (Pfizerpen) o procaine penicillin (Crystacillin) (Wycillin) - penicillin V (Veetids) (Pen V-K) (V-cillin-K) (Ledercillin VK) 1
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Antibacterial/Antimycobacterial Therapy PENICILLINASE-RESISTANT PENICILLINS - cloxacillin (Cloxapen) (Tegopen) - dicloxacillin (Dynapen) (Pathocil) (Dycill) - oxacillin (Prostaphylin) (Bactocil) - methicillin (Staphcillin) - nafcillin (Nafcil) (Unipen) Pharmacodynamics of the Narrow-Spectrum Penicillins (penicillinase-sensitive and -resistant) All penicillins interfere with the synthesis and formation of bacterial cell walls that are essential components of all bacteria. By preventing the successful formation of cell walls in dividing bacteria, the internal components of the bacterial cell are damaged by the osmotic infusion of water and the cell lyses and dies. In order for the penicillin molecules to block the formation of bacterial cell walls, it must interact with a specific structural component (i.e., antibiotic-binding site) of an existing bacterium. That is to say it must be able to approach near enough to the bacterium to interact with it. Some bacteria have been able to resist this action of penicillins by mutating to form an enzyme called penicillinase, which is synthesized and released into the nearby environment of the bacteria. Out away from the bacterial cell, the enzyme encounters the penicillin molecule and destroys it before it can come close enough to the bacterium to bind to the penicillin-binding site and damage its developing cell wall. Those bacteria that have not developed the ability to produce penicillinase can still be killed by penicillin G and penicillin V (i.e., the "penicillinase- sensitive penicillins"). Those bacteria that have developed the ability to produce the penicillinase enzyme are resistant to penicillin G and penicillin V and can only be killed by
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