21.3 Mechanisms of Action of Antibacterial Drugs S13
Table 21.2 Characteristics of Antibacterial Drugs
Cell Wall Synthesis
Natural penicillins: penicillin G, penicillin V
Penicillinase-resistant: methicillin, dicloxicillin
Broad-spectrum: ampicillin, amoxicillin
Extended-spectrum: ticarcillin, piperacillin
Cephalexin, cephradine, cefaclor, cefprozil, cefixime, cefibuten, cefepime
Streptomycin, gentamicin, tobramycin, amikacin, neomycin
Erythromycin, clarithromycin, azithromycin
Lincosamides Lincomycin, clindamycin
Linezolid Streptogramins Quinupristin, dalfopristin
Bactericidal against a variety of bacteria; inhibits penicillin-binding proteins. Resistance is due to synthesis of ß-lactamases, decreased affinity of penicillin-binding proteins, or decreased uptake.
A family of antimicrobial medications; different groups vary in their spectrum of activity and their susceptibility to ß-lactamases. Some must be injected, but others can be taken orally.
Active against Gram-positive organisms and some Gram-negative cocci. Penicillin G is destroyed by stomach acid, and so it usually must be administered by injection. Penicillin V can be taken orally.
Similar to natural penicillins, but resistant to inactivation by the penicillinase of staphylococci. Similar to the natural penicillins, but more active against Gram-negative organisms. Increased activity against Gram-negative rods, including Pseudomonas species.
Some cephalosporins can be taken orally; others must be injected because of their instability in stomach acid.The later generations are generally more effective against Gram-negative bacteria and less susceptible to destruction by ß-lactamases.
Resistant to inactivation by b-lactamases. Imipenem must be given in combination with a drug that inhibits certain kidney enzymes in order to avoid its inactivation.
Resistant to b-lactamases; can be given to patients who are allergic to penicillin. Primarily active against members of the family
Bactericidal against Gram-positive bacteria; binds to the peptide side chain of W-acetylmuramic acid. Used to treat serious systemic infections and antibiotic-associated colitis. In enterococci, resistance is due to a plasmid-encoded altered target.
Bactericidal against Gram-positive bacteria; interferes with the transport of peptidoglycan precursors. Common ingredient in non-prescription antibiotic ointments.
Bactericidal against aerobic and facultative bacteria; binds to the 30S ribosomal subunit, blocking the initiation of translation and causing the misreading of mRNA.Toxicity limits the use. Resistance is due to a plasmid-encoded inactivating enzyme, alteration of the target molecule, or decreased uptake by a cell. Neomycin is commonly used in non-prescription topical antibiotic ointments
Bacteriostatic against some Gram-positive and Gram-negative bacteria; binds to the 30S ribosomal subunit, blocking the attachment of tRNA. Resistance is generally due to decreased accumulation, either through decreased uptake or increased efflux.
Bacteriostatic against many Gram-positive organisms as well as the most common causes of atypical pneumonia; binds to the 50S ribosomal subunit, preventing the continuation of protein synthesis. Used for treating patients who are allergic to b-lactam drugs. Resistance is due to an inactivating enzyme, alteration of the target molecule, or decreased uptake by a cell.
Bacteriostatic and broad-spectrum; binds to the 50S ribosomal subunit, preventing peptide bonds from being formed. Generally used only as a last resort for life-threatening infections. Resistance is often due to a plasmid-encoded inactivating enzyme.
Bacteriostatic against a variety of Gram-positive and Gram-negative bacteria, including the anaerobe Bacteroides fragilis; binds to the 50S ribosomal subunit, preventing the continuation of protein synthesis. Associated with an even greater risk of developing antibiotic-associated colitis.
A new class of bacteriostatic broad-spectrum drugs; binds to the 50S ribosomal subunit, interfering with the initiation of protein synthesis. Effective against a variety of Gram-positive bacteria.
A synergistic combination was recently introduced; the two drugs bind to two different sites on the 50S ribosomal subunit, inhibiting distinct steps of protein synthesis. Effective against a variety of Gram-positive bacteria.
Chapter 21 Antimicrobial Medications
Table 21.2 (continued)
Nucleic Acid Synthesis
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