title: [Mechanisms behind the development of antibiotic resistant bacteria].
abstract: BACKGROUND
  Bacterial resistance to antibiotics is an increasing threat to the successful treatment of hospital and community-acquired infections.
  
  
  METHODS
  Based on relevant literature, this article focuses on some of the essential resistance problems caused by pathogens such as pneumococci, staphylocci, enterococci and gram-negative rods, and provides a review of the genetic and molecular basis of bacterial resistance, as well as of the global trends in bacterial resistance.
  
  
  RESULTS
  Mechanisms of resistance continue to evolve and disseminate among gram-negative as well as gram-positive pathogens. New problems are developing, such as glycopeptide resistance in Staphylococcus aureus. Bacteria have become resistant to antibiotics as a result of chromosomal changes or the exchange of genetic material via plasmids and transposons. The emergence of multiresistant bacteria e.g. S. aureus, enterococci and Mycobacterium tuberculosis, has made many currently available antibiotics ineffective.
  
  
  CONCLUSIONS
  The introduction of new antibiotics has always been followed by development of resistance.
authors.affiliation: Mikrobiologisk institutt, Rikshospitalet, 0027 Oslo. peter.gaustad@labmed.uio.no
authors.forename: P
authors.initials: P
authors.lastname: Gaustad
mesh_terms: D024881:Drug Resistance, Bacterial / Q000235:genetics / Q000276:immunology; D016983:Enterococcus / Q000187:drug effects / Q000276:immunology; D016946:Gram-Negative Aerobic Rods and Cocci / Q000187:drug effects / Q000276:immunology; D006801:Humans; D016106:Methicillin Resistance / Q000235:genetics / Q000276:immunology; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000276:immunology; D011425:Propionibacterium acnes / Q000187:drug effects / Q000276:immunology; D013211:Staphylococcus aureus / Q000187:drug effects / Q000276:immunology; D013296:Streptococcus pneumoniae / Q000187:drug effects / Q000276:immunology