RESISTANCE MECHANISMS - following table. Altered Receptors...

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RESISTANCE MECHANISMS The problem of antibiotic resistance is becoming increasingly apparent as more and more strains of pathogenic microorganisms are untreatable with commonly used antimicrobials. This problem can be attributed to a variety of factors including overuse of antibiotics in agriculture and medicine and misuse of antibiotics by consumers. In addition, antibiotic resistance is often plasmid-borne, which means that resistance can be readily transferred from one organism to another. There are several mechanisms for antibiotic resistance and these relate to the sites of antimicrobial activity. These mechanisms include: 1. Altered receptors for the drug 2. Decreased entry into the cell 3. Destruction or inactivation of the drug These mechanisms and some examples are outlined in the
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Unformatted text preview: following table. Altered Receptors 1. Beta-lactams Altered Penicillin Binding Proteins 2. Macrolides Methylation of 2 adenine residues in 23S RNA of the 50S subunit 3. Rifampin Single amino acid change in RNA polymerase -subunit 4. Sulfonamide/trimethoprim Altered synthetase binds pABA preferentially/altered reductase for TMP 5. Nalidixic acid Altered gyrase 6. Streptomycin Altered S12 protein in 30S subunit Decreased Entry 1. Normally biphasic, active transport reduced 2. Fosfomysin (chromosomal) Glucose-6-phosphate transport reduced Destruction/Inactivation 1. acetyltransferase Acetylates 2. Beta-lactamase Cleaves -lactam ring 3. Aminoglycosides Acetylation or phosphorylation as drug passes membrane...
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