The following are how antibiotic act against microorganism either In-vivo or In-vitro
Antibacterial action attacks the 30s portion of the ribosomic which causes a misreading of coding of RNA and as a result causes the manufacture of wrong protein.
Gentamycin can completely stop protein synthesis by producing bactericidal actions against the microorganism (Killing the invading microorganism) that is; they can exert a lethal action of neutralizing protein synthesis like the Aminoglycosides
Bacteriostatic antibiotics in the other hand disrupt or inhibit protein synthesis incompletely in such a way that the invading microorganism is only halted and not destroy. These antibiotics exert a partial action on protein synthesis that prevents active multiplication of the microorganisms and examples of these classes are Erythromycin, chloramphenicol, tetracyclines and linocomycin
Bacterial cell wall
The penicillins, cephalosporins and cephamycins block the cross linking of glycopeptides by transpeptidization rather like the removal of cement from a brick wall.It should be noted that the bacterial cell wall contains three vital structural units which are Muramic acid, diaminipimelic acid and D-amino.The normal function of microorganism’s mucopeptidases is to lyse the inner part of wall to allow the division of the growing bacteria but these antibiotics disrupt this mechanism causing complete weakening of the cell wall.
They can attack the cell wall of microorganism with destruction of the Osmotic defense of the bacterium and cause it to explode like a balloon
Folic Acid Inhibition
An example of a Folic Acid inhibitor antibiotics are the Sulphonamides.This inhibition occurs by competition with the Para-Amino benzoic acid (PABA) for the binding site on enzymes. Trimethroprim inhibits folic acid at a different point to that if the Sulphonamides.These two drugs are often combined and their action is then Bacteriocidal.
They can also attack the cell membrane and cause the loss of vital growth requirements like the class of Polymyxins. They bind to the Lipopolysaccharide(LPS) in the outer cell membrane of Gram-negative bacteria and disrupt both the outer and inner membrane by altering its structure, making it more permeable resulting to water uptake which leads to cell death(Bactericidal)