[Genetic and biochemical basis of microbial resistance to antibiotics].

Antibiotics affect different structures or metabolic processes in a bacterial cell inhibiting its growth and reproduction what results in the destruction of microorganisms. Microorganisms have developed some resistance mechanisms in order to survive in the presence of antibiotics. Recent advances in molecular biology of microorganisms Recent advances in molecular biology of microorganisms and technique of recombinant DNA have helped us to understand more clearly the molecular aspects of resistance of microorganisms against antibiotics. Some of the mechanisms of drug resistance include: change of the binding site of the antibiotic due to the mutation of genes being responsible for the synthesis of the target sites of the antibiotic (aminoglycosides, chloramphenicol, beta-lactams); change of the binding site of the antibiotic by the activity of methylase (macrolides); diminished patency of the cell membrane for the antibiotic (tetracyclines, chloramphenicol, macrolides, aminoglycosides); active transport of the antibiotic outside the cell (tetracyclines); synthesis of specific enzymes modifying and thus inactivating the molecule of the antibiotic (aminoglycosides, chloramphenicol); tolerance of microorganisms to the activity of the antibiotic (beta-lactams); inactivation of the antibiotic molecule by the enzymes such as beta-lactamase for the beta-lactam antibiotic and by esterase for the antibiotic with a lactone ring (macrolides).