Doxycycline belongs to the group of tetracyclines and acts bacteriostatic
against many Gram-positive and Gram-negative. The action of doxycycline
is based on inhibition of bacterial protein synthesis. Colistin is an antibiotic
from the group of polymyxins with bactericidal action against mainly
Gram-negative bacteria. Polymyxins interact strongly with phospholipids and
penetrate into and disrupt the structure of cell membranes. Administered
orally, colistin is poorly resorbed and, therefore, performs its
action predominantly gastrointestinally.