N. О. Vrynchanu Role of efflux systems in microbial resistance to antibiotics
The review summarizes current data about classification, structure, and functions of efflux pumps, their
role in microorganism survival and resistance. Genetic determinants of transporters are located on chromosomes,
plasmids or transposons, contributing in fast gene transfer, and, therefore – in the appearance
of new resistant pathogens. It is important to remark, that efflux-mediated resistance had been already
identified for all known classes of antibiotics.
Prokaryotic and eukaryotic efflux pumps are divided into two types: primary (ATP-depending) and secondary
transporters (using an electrochemical gradient energy). The molecular structure of efflux systems
was the basis for their classification into 5 families (superfamilies) – ABC (ATP binding cassette), MFS
(major facilitator superfamily), MATE (multidrug and toxic compound extrusion), SMR (small multidrug
resistance) and RND (resistance-nodulation-division). It is currently established, that clinically relevant
antibiotic resistance in Gram-negative and Gram-positive pathogens is mostly caused by RND- and MFSpumps,
respectively.
In addition to the role in resistance, efflux pumps are involved in extrusion of virulence factors, adhesins,
toxins, signals of intercellular interactions, ensuring the microorganism survival in certain ecological
niches, particularly – in human, animal or plant organism.
The presented data underline a complexity of efflux systems in prokaryotes and its significant role in
antibiotic resistance and colonization of macroorganism. Hyperactivation of efflux pumps is one of the key
resistance mechanisms, resulting in a serious challenge in the treatment of patients with inflammatory
diseases, caused by resistant strains of pathogens.
Key words: microorganisms, antimicrobial agents, resistance, efflux pumps