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TYPES OF DRUG RESISTANCE.pptx
- 1. TYPES OF DRUG RESISTANCE K.C. LETSATSI
- 2. Types of drug resistance Natural Acquired Mutation Recombination Transferred with plasmids and transposons
- 5. Biochemical mechanisms of bacterial resistance • Altered protein binding sites. Penicillin • Altered RNA polymerase. Rifampin Erythromycin Clindamycin • Or Altered DNA gyrase. • Nalidixic acid
- 6. … • Decrease entry or accumulation, by bacteria changing permeability to the drug Tetracyclines Aminoglycosides • Inactivation of drug by enzymes eg: β- lactamase Penicillin Cephalosporins Chloramphenicol aminoglycosides.
- 7. … • Synthesis of resistant metabolic pathway Trimethoprim Sulphonamides. • Acquired Resistance: these is plasmid mediated resistance that can be passed from organism to organism Sulphonamides • Active efflux: This a situation where the organism develops mechanisms where they can eliminate the drug very fast before it causes harm. Tetracyclines
Hinweis der Redaktion
- Natural resistance depends on absence of target for antibiotic. For ins. Mycoplasma is not sensitive to penicillin because do not have cell wall with murein. Mutation, recombination and plasmid- and transponos-mediated resistance are based on changes in genetic material and can be transferred from one bacterium to another. Chromosomal resistance is due to a mutation is the gene that codes for either the target of the drug or the transport system in the membrane that controls the uptake of the drug. The frequency of spontaneous mutations usually is one mutational cell among to billion of intact cells. It is much lower than the frequency of plasmid-mediated resistance. Therefore, chromosomal resistance is less of a clinical problem than is plasmid-mediated resistance.
- Any large population of microbes is likely to contain a few individual cells that are already drug-resistant because of prior mutations or transfer of plasmids (a). As long as the drug is not present in the habitat, the numbers of these resistant forms will remain low because they have no particular growth advantage. But if the population is subsequently exposed to this drug (b), sensitive individuals are inhibited or destroyed, and resistant forms survive and proliferate. During subsequent population growth, all offspring of these resistant microbes will inherit this drug resistance. In time, the population will become completely resistant (figure c). In ecological terms, the environmental factor (in this case, the drug) has put selection pressure on the population, allowing the more "fit" microbe (the drug-resistant one) to survive, and the population has evolved to a condition of drug resistance. Natural selection for drug-resistant forms is apparently a common phenomenon. It takes place most frequently in various natural habitats, laboratories, and medical environments, but it occasionally occurs within the bodies of humans and animals during drug therapy
- Most normal, healthy body surfaces, such as the skin, large intestine, oral cavity provide numerous habitats for a virtual "garden" of microorganisms. These normal colonists or residents, called the flora* or microflora, consist mostly of harmless or beneficial bacteria, but some can be potential pathogens. If a broad-spectrum antimicrobic is introduced into the host to treat infection, it will destroy microbes regardless of their roles in the ecological balance, affecting not only the targeted infectious agent but also many others in sites far removed from the original infection. In some cases, the result of this therapy is the destruction of beneficial resident species and the subsequent survival and overgrowth of opportunistic residents or contaminants that can be agent of disease.