Colistin is an antibiotic that has a bactericidal action when given in. Normal doses. Colistin attaches itself to the bacterial cell wall, so disturbing the permeability of the cell wall and causing the plasma contents as purine and pyrimidines to escape from the cell. This results usually in lysis.
Doxycycline is mainly bacteriostatic with a broad spectrum of antimicrobial activity including chlamydia, mycoplasmas, rickettsia, and spirochetes and aerobic and anaerobic Gram – positive and Gram-negative pathogenic bacteria and some protozoa. Doxycycline is taken up into sensitive bacterial cells by an active transport process. Once within the cell they bind reversibly to the 30S subunit of the ribosome, preventing the binding of amino acyl transfer RNA and inhibiting protein synthesis and hence cell growth.
