Chapter 20 Notes.docx - Chapter 20 Antimicrobial Medication...

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Chapter 20: Antimicrobial Medication Importance of Antimicrobial Medications o Imagine a world without antimicrobial medications Prognosis for people with common diseases (for example bacterial pneumonia, severe staphylococcal infections) was grim before availability of penicillin in 1940s Physicians could identify cause, but only treatment was usually bedrest History and Development of Antimicrobial Medications o Discovery of Antimicrobial Medications Salvarsan (1910) first documented case Red dye Prontosil (1932) used to treat streptococcal infections in animals Both are chemotherapeutic agents 1. Chemicals used to treat disease 2. Antimicrobial medications, or antimicrobials o Discovery of Antibiotics Alexander Fleming identified mold Penicillium excreting compound toxic to Staphylococcus 1. Named compound penicillin 2. Showed effective in killing many bacterial species Ernst Chain and Howard Florey purified penicillin, and tested compounds in 1941 on police officer with life-threatening Staphylococcus aureus infection Characteristics of Antimicrobial Medications o Selective Toxicity: cause greater harm to microbes Interfere with essential structures or properties common in microbes but not human cells Therapeutic index 1. Lowest dose toxic to patient / dose used for therapy Antimicrobial Action (how they work) 1. Bacteriostatic chemicals inhibit bacterial growth o Patient’s defenses must still eliminate 2. Bactericidal chemicals kill bacteria o Spectrum of Activity Broad-spectrum antimicrobials affect a wide range 1. Important for treating acute life-threatening diseases 2. Disrupt normal microbiota that help in keeping out pathogens Narrow-spectrum antimicrobials affect limited range 1. Requires identification of pathogen, testing for sensitivity 2. Less disruptive to normal microbiota than the broad spectrum o Tissue Distribution, Metabolism, and Excretion Antimicrobials differ in behavior in body 1. Only some medications cross the brain-blood barrier important in treating meningitis
2. Some unstable at low pH, must be injected 3. Rate of elimination or half-life dictates frequency o Adverse (bad) Effects of Antimicrobials Include allergic reactions and toxic effects Suppression of normal microbiota may allow dysbiosis Important to remember that antimicrobials save countless lives when properly prescribed and used o Resistance to Antimicrobials Certain bacteria have innate or intrinsic resistance 1. Type of resistance they are “born” with o For example, Mycoplasma lack cell wall, resist penicillin etc.

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