title: Risk factors associated with the isolation of colistin-resistant gram-negative bacteria: a matched case-control study.
abstract: OBJECTIVE
  The emergence of multidrug-resistant gram-negative bacteria has led to the re-use of colistin, but resistance to this agent has already been reported. We aimed to investigate the potential risk factors for the isolation of colistin-resistant Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa from hospitalized patients.
  
  
  METHODS
  Matched case-control study.
  
  
  METHODS
  Tertiary care hospital in Athens, Greece.
  
  
  METHODS
  Case patients were those who had provided a clinical specimen from which a colistin-resistant K. pneumoniae, A. baumannii, or P. aeruginosa was isolated. Controls were selected from a pool of patients who had susceptible to colistin isolates and were matched (1:1) to cases for species of microorganism and site of isolation. Susceptibility to colistin was determined with the Etest.
  
  
  METHODS
  None.
  
  
  RESULTS
  Data regarding patient demographics, comorbidities, admission to the intensive care unit, prior antibiotic use, and invasive procedures performed were analyzed as risk factors in a matched bivariable model. Variables significantly associated with colistin-resistant isolates (p < .05) were entered in a backward multivariable logistic regression model. Forty-one colistin-resistant unique patient isolates were identified from January 1, 2006, until March 31, 2007. These isolates represented infection in 35 of 41 patients. Risk factors significantly associated with the isolation of colistin-resistant isolates were age, duration of intensive care unit stay, [corrected] surgical procedures, use of colistin, use of monobactams, duration of use of colistin and duration of use of antifungal agents [corrected] In the multivariable model, use of colistin was identified as the only independent risk factor (adjusted odds ratio = 7.78, p = .002).
  
  
  CONCLUSIONS
  Colistin-resistant K. pneumoniae, A. baumannii, and P. aeruginosa pathogens may be encountered in clinical practice, in association with inappropriate colistin use. To prevent this phenomenon, colistin should be used judiciously, given that treatment options for colistin-resistant gram-negative bacteria are limited.
authors.affiliation: Alfa Institute of Biomedical Sciences, Athens, Greece.
authors.forename: Dimitrios K
authors.initials: DK
authors.lastname: Matthaiou
authors.forename: Argyris
authors.initials: A
authors.lastname: Michalopoulos
authors.forename: Petros I
authors.initials: PI
authors.lastname: Rafailidis
authors.forename: Drosos E
authors.initials: DE
authors.lastname: Karageorgopoulos
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Papaioannou
authors.forename: Georgia
authors.initials: G
authors.lastname: Ntani
authors.forename: George
authors.initials: G
authors.lastname: Samonis
authors.forename: Matthew E
authors.initials: ME
authors.lastname: Falagas
mesh_terms: D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000302:isolation & purification; D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016022:Case-Control Studies; D003091:Colistin / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D005260:Female; D006801:Humans; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000302:isolation & purification; D008297:Male; D008875:Middle Aged; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000302:isolation & purification; D012189:Retrospective Studies; D012307:Risk Factors
chemical_list: D000900:Anti-Bacterial Agents; D003091:Colistin