Antibiotics and the Mechanisms of Resistance to Antibiotics

Resistance is the ability of a bacteria against the antogonizing effect of an antibacterial agent upon reproduction prevention or bactericidal. The development of resistance to antibiotics in bacteria often develop as a result of unnecessary and inappropriate use of antibiotics. Through the intense use of antibiotics, resistant microorganisms have emerged over the years, and problems were started to be experienced for the treatrment of these infections emerged with these resistant microorganisms. Today, on the one hand trying to develop new drugs, on the other hand, there are difficulties in treatment as a result of development of resistance to these drugs rapidly. The development of resistance to antibiotics is a major public health problem in all over the world (1-3). The main four types of resistance to antibiotics develops; 1. Natural (Intrensic) resistance 2. Acquired resistance 3. Cross-resistance 4. Multi-drug resistance and pan-resistance 1. Natural (Intrensic, Structural) resistance: This kind of resistance is caused by the structural characteristics of bacteria and it is not associated with the use of antibiotics. It has no hereditary property. It develops as result of the natural resistance, or the microorganisms not including the structure of the target antibiotic, or antibiotics not reaching to its target due to its characteristics. For example, Gramnegative bacteria vancomycin does not pass in the outer membrane so Gram-negative bacteria is naturally resistant to vancomycin. Similarly, L-form shape of bacteria which are wall-less forms of the bacteria, and the bacteria such as cell wall-less cell Mycoplasma and Ureaplasma are naturally resistant to beta-lactam antibiotics that inhibit the cell wall synthesis (1,4-6). 2. Acquired resistance: As result of the changes in the genetic characteristics of bacteria, an acquired resistance occurs due to its not being affected from the antibiotics it has been responsive before. This kind of resistance occurs due to mainly structures of chromosome or extrachromosomal (plasmid, transposon, etc.). a. Chromosomal resistance arise from mutations in developing in spontaneous bacterial chromosome (spontaneous). Such mutations may occur according to some physical (ultraviolet, etc.) and chemical factors. This can be a result of structural changes in bacterial cells. The result may be reduced permeability of bacterial drug or changes of the target of the drug may be in the cell. Streptomycin, aminoglycosides, erythromycin, lincomycin can develop resistance against these types. *From Department of Infectious Diseases and Clinical Microbiology, Ankara Training and Research Hospital, Ankara, Turkey. ANTIBIOTICS AND THE MECHANISMS OF RESISTANCE TO ANTIBIOTICS