Antimicrobial therapy aims at treating infection with a drug to which The casual microorganism is sensitive and which has a selective toxicity only for the infecting organism without harming the Host cells.
Some antimicrobials are bacteriostatic, i.e., the arrest multiplications of bacterias, e.g., chloramphenicol, erythromycin and sulphonamides.
If the drug is withheld, the organism May start reproducing again. Some other antimicrobial are bactericidal i.e., they bring about the death of the organism, e.g., streptomycin penicillin drugs such as erythromycin a tetracycline are bacteriostatic at usual therapeutic blood level but are bactericidal at higher concentrations. However, the demarcation between bacteriostatic and bactericidal action is not very clear Cut, and depend on the types of organism, the number of organisms present and the constitutions of the drug in the blood.
Antimicrobial drug differ in the range of bacteria they inhibit. Broad-spectrum drug such as ampicillin and tetracycline are effective against both gram-positive and gram-negative bacterias, whereas flucloxacillin has a narrow spectrum and is active against gram-positive bacteria such as staphylococcus aureus but ineffective against most gram-negative bacteria.
It is preferable to use a narrow spectrum drugs for known pathogen because it does not affect the composition of the normal flora at various sites. A broad-spectrum drug may have an adverse effect on the normal Flora.
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