1- Spectrum of Activity Range microorganism affected by the drug - that kill or inhibit
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Broad Spectrum: affects wide range, disrupt normal flora of body, used in cases of rapid onset threatening infections, when there is no time to culture the causative agents
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Narrow Spectrum: Limited range, requires the identification of the pathogen
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Different antibiotics target different kinds of bacteria i.e., different spectrum of activity
Example –Penicillin-G (= original pen.) mainly streptococci (narrow spectrum) –Vancomycin only Gram-positive bacteria (intermediate spectrum) –Carbapenemsmany different bacteria (very broad spectrum)
2-Selective toxicity: the antimicrobial agent blocks or inhibits a metabolic pathway in a micro-organism which is either absent or is different in the mammalian cells of the human host.
=The drug must be more toxic to a pathogen than a pathogen’s host.
Types of antimicrobial
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Cidal drug: removal of all bacteriodes due to drug (primarily for immunocompromised) -as penicillin
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Stop growth - static drug: primary action by immune system - Choloramphenicol
3-According to mechanism of action
Each micro-organism has special structure which can be a target for the antimicrobials • Example for bacteria : difference between + & - is thickness of cell wall
