Example bacterial pneumonia severe staphylococcal

This preview shows page 32 - 38 out of 75 pages.

example bacterial pneumonia, severe staphylococcal infections) was grim before availability of penicillin in 1940s Physicians could identify cause, but only treatment was usually bedrest Misuse coupled with evolution of microbial resistance threatens these medications
20.1. History and Development of Antimicrobial Medications Discovery of Antibiotics In 1928, Alexander Fleming identified mold Penicillium excreting compound toxic to Staphylococcus Named compound penicillin Showed effective in killing many bacterial species Unable to purify, he later abandoned research ~10 years later, Ernst Chain and Howard Florey purified, tested compounds in 1941 on police officer with life- threatening Staphylococcus aureus infection Patient improved dramatically within 24 hours Supply of purified penicillin ran out and he later died WWII spurred research and development; penicillin G was first antibiotic (naturally produced antimicrobial)
20.1. History and Development of Antimicrobial Medications Discovery of Antibiotics (continued…) Soon thereafter, Selman Waksman purified streptomycin from soil bacterium Streptomyces griseus Researchers screened hundreds of thousands of microbes for antibiotics Pharmaceutical companies examine soil samples from around world Discovered in 1960s that altering structure of penicillin yields new medications
20.2. Characteristics of Antimicrobial Medications Selective Toxicity: cause greater harm to microbes Interfere with essential structures or properties common in microbes but not human cells Toxicity is relative and expressed as therapeutic index Lowest dose toxic to patient / dose used for therapy Penicillin G useful, has high index; interferes with cell wall synthesis, a process not present in humans Medicationss too toxic for systemic use may be used topically Antimicrobial Action Bacteriostatic chemicals inhibit bacterial growth Patient’s defenses must still eliminate Bactericidal chemicals kill bacteria Sometimes only inhibitory
20.2. Characteristics of Antimicrobial Medications Spectrum of Activity Broad-spectrum antimicrobials affect a wide range Important for treating acute life-threatening diseases Especially when no time to culture for identification Disrupt normal microbiota that help in keeping out pathogens Narrow-spectrum antimicrobials affect limited range Requires identification of pathogen, testing for sensitivity Less disruptive to normal microbiota Effects of Combinations Some medications interfere with each other, are antagonistic Combinations where one medication enhances are synergistic Combinations that are neither are additive
20.2. Characteristics of Antimicrobial Medications Tissue Distribution, Metabolism, and Excretion Antimicrobials differ in behavior in body Only some medications cross the brain-blood barrier important in treating meningitis Some unstable at low pH, must be injected

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture