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Mechanisms of Antibiotic Resistance and Their Dissemination of Resistance Genes in the Hospital Environment
Published online by Cambridge University Press: 02 January 2015
Abstract
The dissemination of resistance determinants among bacterial populations depends on ecological and epidemiological properties as well as additional factors: 1) the mechanism of resistance or its specificity toward a certain drug, and 2) the genetic basis in relation to the mobility of the genetic material and its survival in bacteria. From two resistance mechanisms directed toward old-fashioned drugs, namely sulfonamides (Su) and streptomycin (Sin), we can deduce that a resistance mechanism is encoded by a special sort of genetic material. Thus the linked SmSu resistance mediated by a sulfonamide-resistant dihydropteroatsynthetase II and the aminoglycoside phosphotransferase APH-(3") is always located on very small pBPl-like plasmids. Such plasmids survive without selective pressure of drugs in Enterobacteriaceae in the bowel flora of humans and animals. Both resistance determinants can be mediated by a transposon which codes for the production of a dihydropteroatsynthetase I in connection with an aminoglycoside adenylyltransferase AAD-(3"). These two mechanisms are genetically linked as well. The basic structure is a transposon designated Tn2411, which belongs to a whole family of transposons, all including the basic structure; however, their genetic exchange and substitution leads to structures coding for many different enzymatic characters: ANT-(2") (Gentamicin resistance), CAT (Chlo-ramphenicol resistance), AAC-(6') (resistance to all modern aminoglycosides), TEM-1, OXA-1, OXA-2, or PSE (β-lactam resistance). Resistance to the modern (β-lactamase-stable antibiotics is mediated by mutation in the regulatory genes of chromosomally-determined (β-lactamases. A spread of these resistance mechanisms can be avoided as long as the responsible genes are not located on sufficient structures like small plasmids or efficient transposons.
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- Copyright © The Society for Healthcare Epidemiology of America 1983
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