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DRUGS USED TO TREAT INFECTIONCHAPTER 83 ANTI-MICROBIALS•Antibiotics (antibacterial)•Antifungals (treatment of mycoses, fungi, tinea, candida and yeast)•Antiprotozoal (Flagyl only)•Parasitic agents (worms, scabies, lice)•Antivirals (work against viruses, such as HIV, herpes, influenza) NOTE: we will not cover antivirals•The goal: toxic to microbes, harmless to host!!Drugs work on:•Cell wall synthesis and membrane permeability•Protein synthesis (lethal)•Nonlethal inhibitors of protein synthesis•Interfere w/synthesis of nucleic acids (DNA & RNA)•Antimetabolites•Drugs that suppress viral replication (enzyme inhibitors)Various themes used to classify by susceptible organism•Gram + or –•Narrow spectrum = only a few types of bacteria are sensitive•Broad spectrum = a variety of bacteria gram + or - can be sensitive•Extended spectrum = greater activity against gram - rods•Bacterial, fungal, or viralBacteriostatic- drug or solution that slows growth and inhibits the reproduction of bacteria•(does not kill)•Most can be bactericidal at high dosesoBactericidal- drug or solution that directly kills bacteriaAcquired Resistance to Antimicrobial Drugs•Over time, organisms develop resistance; May have been highly responsive and then became less susceptible to one or more drugs•Resistance is of great concern in that it can render currently effective drugs useless, thereby creating a clinical crisis and a constant need for new antimicrobial agents•It is the microbethat becomes resistant, not the patient!•Table 83-3 Highly Resistant Bacteria & Drug Treatment•Four basic actions for resisting drugs:oReduction of drug concentration at site of drug actionMicrobes can cease active uptake of drug into cellMicrobes can increase active export of drugoAlter the structure of drug target moleculesoProduce a drug antagonistoDrug inactivation
•Mechanisms for Acquired ResistanceoSpontaneous mutationSingle drugresistanceoConjugationDNA of microorganism gets transferred from one bacteria to anotherProduces multi-drugresistance Thus need to continuously create NEW antimicrobials!oSpontaneous mutation and conjugation are random events whose incidence is independent of drug use. Drugs simply make conditions favorable for overgrowth of microbes that have acquired mechanisms for resistance.Relationship B/W Antibiotic Use and Drug-Resistant Microbe Emergence•Whichantibiotics promote the most resistance? Broad spectrum•Does the amountof antibiotic use impact resistance? YES, thus avoid use when NOT needed!•Hospital-associated infections (HAI) Are the most difficult to treat•Antibiotic use in Agriculture ---> Drug resistant bacteria infect humans•Suprainfection (superinfection): resistance that results when an antibiotic kills normal flora, thus favoring the emergence of a new infection that is often difficult to eliminateSELECTION OF ANTIBIOTICS: “MATCH THE DRUG WITH THE BUG!”