title: Colistin, mechanisms and prevalence of resistance.
abstract: BACKGROUND
  Infections caused by multi-drug-resistant Gram-negative bacteria, particularly Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae, that cause nosocomial infections, represent a growing problem worldwide. The rapid increase in the prevalence of Gram-negative pathogens that are resistant to fluoroquinolones and aminoglycosides as well as all β-lactams, including carbapenems, monobactam, cephalosporins and broad-spectrum penicillins, has prompted the reconsideration of colistin as a valid therapeutic option. Colistin is an old class of cationic, which act by disrupting the bacterial membranes resulting in cellular death. Although there has been a significant recent increase in the data gathered on colistin, focusing on its chemistry, antibacterial activity, mechanism of action and resistance, pharmacokinetics, pharmacodynamics and new clinical application, the prevalence of colistin resistance has been very little reported in the literature. This review concentrates on recent literature aimed at optimizing the clinical use of this important antibiotic.
  
  
  METHODS
  The available evidence from various studies (microbiological and clinical studies, retrieved from the PubMed, and Scopus databases) regarding the mechanisms and prevalence of resistance was evaluated.
  
  
  RESULTS
  Increasing use of colistin for treatment of infections caused by these bacteria has led to the emergence of colistin resistance in several countries worldwide. Although resistance to polymyxins is generally less than 10%, it is higher in the Mediterranean and South-East Asia (Korea and Singapore), where colistin resistance rates are continually increasing.
  
  
  CONCLUSIONS
  There is a critical need for effective infection prevention and control measures and strict use of antibiotics in the world to control the rise and spread of colistin resistance.
authors.affiliation: Infectious Disease and Tropical Medicine Research Center, Tabriz University of Medical Sciences , Tabriz , Iran.
authors.forename: Abed Zahedi
authors.initials: AZ
authors.lastname: Bialvaei
authors.forename: Hossein
authors.initials: H
authors.lastname: Samadi Kafil
mesh_terms: D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics / Q000494:pharmacology* / Q000627:therapeutic use; D003091:Colistin / Q000493:pharmacokinetics / Q000494:pharmacology* / Q000627:therapeutic use; D003428:Cross Infection / Q000188:drug therapy / Q000382:microbiology; D024901:Drug Resistance, Multiple, Bacterial; D006090:Gram-Negative Bacteria / Q000187:drug effects; D016905:Gram-Negative Bacterial Infections / Q000188:drug therapy* / Q000382:microbiology; D006801:Humans; D011113:Polymyxins / Q000494:pharmacology; D015995:Prevalence
chemical_list: D000900:Anti-Bacterial Agents; D011113:Polymyxins; D003091:Colistin
keywords: Colistimethate sodium; Colistin; Colistin resistance; MDR Gram-negative bacteria; Polymyxin; Prevalence