title: Gastrointestinal tract colonization with fluoroquinolone-resistant Escherichia coli in hospitalized patients: changes over time in risk factors for resistance.
abstract: OBJECTIVE
  The prevalence of fluoroquinolone (FQ) resistance in Escherichia coli has increased markedly in recent years. Despite the important role of gastrointestinal tract colonization with FQ-resistant E. coli (FQREC), the prevalence of and risk factors for FQREC colonization among the general hospitalized patient population have not been described, to our knowledge. The objective of this study was to identify the prevalence of and risk factors for FQREC colonization among hospitalized patients.
  
  
  METHODS
  Three-year case-control study. Case patients (ie, all subjects with FQREC colonization) were compared with control patients (ie, all subjects without FQREC colonization).
  
  
  METHODS
  Two large medical centers within an academic health system.
  
  
  METHODS
  All patients hospitalized at the 2 study hospitals.
  
  
  METHODS
  Three annual fecal surveillance surveys were conducted. All patients colonized with FQREC (levofloxacin minimum inhibitory concentration, >or=8 microg/mL) were identified.
  
  
  RESULTS
  Of the 774 subjects, 89 (11.5%) were colonized with FQREC. Although there was a significant association between prior FQ use and FQREC colonization on bivariable analysis (odds ratio [OR], 2.02 [95% confidence interval {CI}, 1.14-3.46]; P=.01), there was statistically significant effect modification by year of study (P=.005). In multivariable analyses, after controlling for the hospital and for the duration of hospitalization prior to sampling, the association between FQ use and FQREC colonization was as follows: adjusted OR (aOR), 0.97 (95% CI, 0.29-3.23) in 2002; aOR, 1.41 (95% CI, 0.57-3.50) in 2003; and aOR, 9.87 (95% CI, 3.67-26.55) in 2004.
  
  
  CONCLUSIONS
  The association between prior FQ use and FQREC colonization varied significantly by study year, suggesting that the clinical epidemiology of resistant organisms may change over time. Furthermore, in the context of recent work showing significant changes in FQREC prevalence as well as changes in FQ resistance mechanisms (specifically, efflux overexpression) over the same time period, these results suggest a previously unrecognized complexity in the relationship between the clinical and molecular epidemiology of FQ resistance.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, the Center for Clinical Epidemiology and Biostatistics, the University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6021, USA. ebbing@mail.med.upenn.edu
authors.forename: Ebbing
authors.initials: E
authors.lastname: Lautenbach
authors.forename: Joshua P
authors.initials: JP
authors.lastname: Metlay
authors.forename: Mark G
authors.initials: MG
authors.lastname: Weiner
authors.forename: Warren B
authors.initials: WB
authors.lastname: Bilker
authors.forename: Pam
authors.initials: P
authors.lastname: Tolomeo
authors.forename: Xiangqun
authors.initials: X
authors.lastname: Mao
authors.forename: Irving
authors.initials: I
authors.lastname: Nachamkin
authors.forename: Neil O
authors.initials: NO
authors.lastname: Fishman
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000187:drug effects*; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology*; D005260:Female; D024841:Fluoroquinolones / Q000494:pharmacology* / Q000627:therapeutic use; D005767:Gastrointestinal Diseases / Q000453:epidemiology* / Q000382:microbiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012307:Risk Factors
chemical_list: D024841:Fluoroquinolones