title: Beta-lactam antibiotics and selection of resistance: speculation on the evolution of R-plasmids.
abstract: In this paper we describe two genetic mechanisms which are responsible for the development of resistance to third-generation cephalosporins. One is a plasmid-mediated mechanism involving a mutation in the SHV-1-gene towards the production of the beta-lactamase SHV-2 which has increased affinity for these antibiotics. The other is chromosomally mediated and occurs at high frequency by mutation of inducible beta-lactamase-genes, leading to derepressed production of the enzyme. Together with other examples of resistance genes these two mechanisms lead us to a hypothesis about the evolution of beta-lactamase producing bacteria.
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D005075:Biological Evolution; D002876:Chromosomes, Bacterial; D004755:Enterobacteriaceae / Q000187:drug effects / Q000235:genetics; D011815:R Factors; D047090:beta-Lactams
chemical_list: D000900:Anti-Bacterial Agents; D047090:beta-Lactams