title: Mechanisms of antibiotic resistance and their dissemination of resistance genes in the hospital environment.
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 (Sm), 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 pBP1-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 (Chloramphenicol resistance), AAC-(6') (resistance to all modern aminoglycosides), TEM-1, OXA-1, OXA-2, or PSE (beta-lactam resistance). Resistance to the modern beta-lactamase-stable antibiotics is mediated by mutation in the regulatory genes of chromosomally-determined beta-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.
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects / Q000235:genetics*; D003428:Cross Infection / Q000382:microbiology*; D004352:Drug Resistance, Microbial; D005798:Genes, Bacterial / Q000187:drug effects*; D006801:Humans; D010957:Plasmids / Q000187:drug effects*; D013307:Streptomycin / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D013449:Sulfonamides; D013307:Streptomycin