Exam I - Anti-Infectives.docx - DRUGS USED TO TREAT INFECTION CHAPTER 83 ANTI-MICROBIALS \u2022 Antibiotics(antibacterial \u2022 Antifungals(treatment of

Exam I - Anti-Infectives.docx - DRUGS USED TO TREAT...

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DRUGS USED TO TREAT INFECTION CHAPTER 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 viral Bacteriostatic - drug or solution that slows growth and inhibits the reproduction of bacteria (does not kill) Most can be bactericidal at high doses o Bactericidal - drug or solution that directly kills bacteria Acquired 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 microbe that becomes resistant, not the patient ! Table 83-3 Highly Resistant Bacteria & Drug Treatment Four basic actions for resisting drugs: o Reduction of drug concentration at site of drug action Microbes can cease active uptake of drug into cell Microbes can increase active export of drug o Alter the structure of drug target molecules o Produce a drug antagonist o Drug inactivation
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Mechanisms for Acquired Resistance o Spontaneous mutation Single drug resistance o Conjugation DNA of microorganism gets transferred from one bacteria to another Produces multi-drug resistance Thus need to continuously create NEW antimicrobials! o Spontaneous 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 Which antibiotics promote the most resistance? Broad spectrum Does the amount of 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 eliminate SELECTION OF ANTIBIOTICS: “MATCH THE DRUG WITH THE BUG!”
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