title: Hospital ward antibiotic prescribing and the risks of Clostridium difficile infection.
abstract: OBJECTIVE
  Only a portion of hospital-acquired Clostridium difficile infections can be traced back to source patients identified as having symptomatic disease. Antibiotic exposure is the main risk factor for C difficile infection for individual patients and is also associated with increased asymptomatic shedding. Contact with patients taking antibiotics within the same hospital ward may be a transmission risk factor for C difficile infection, but this hypothesis has never been tested.
  
  
  OBJECTIVE
  To obtain a complete portrait of inpatient risk that incorporates innate patient risk factors and transmission risk factors measured at the hospital ward level and to investigate ward-level rates of antibiotic use and C difficile infection risk.
  
  
  METHODS
  A 46-month (June 1, 2010, through March 31, 2014) retrospective cohort study of inpatients 18 years or older in a large, acute care teaching hospital composed of 16 wards, including 5 intensive care units and 11 non-intensive care unit wards.
  
  
  METHODS
  Patient-level risk factors (eg, age, comorbidities, hospitalization history, antibiotic exposure) and ward-level risk factors (eg, antibiotic therapy per 100 patient-days, hand hygiene adherence, mean patient age) were identified from hospital databases.
  
  
  METHODS
  Incidence of hospital-acquired C difficile infection as identified prospectively by hospital infection prevention and control staff.
  
  
  RESULTS
  A total of 255 of 34 298 patients developed C difficile (incidence rate, 5.95 per 10,000 patient-days; 95% CI, 5.26-6.73). Ward-level antibiotic exposure varied from 21.7 to 56.4 days of therapy per 100 patient-days. Each 10% increase in ward-level antibiotic exposure was associated with a 2.1 per 10,000 (P < .001) increase in C difficile incidence. The association between C difficile incidence and ward antibiotic exposure was the same among patients with and without recent antibiotic exposure, and C difficile risk persisted after multilevel, multivariate adjustment for differences in patient-risk factors among wards (relative risk, 1.34 per 10% increase in days of therapy; 95% CI, 1.16-1.57).
  
  
  CONCLUSIONS
  Among hospital inpatients, ward-level antibiotic prescribing is associated with a statistically significant and clinically relevant increase in C difficile risk that persists after adjustment for differences in patient-level antibiotic use and other patient- and ward-level risk factors. These data strongly support the use of antibiotic stewardship as a means of preventing C difficile infection.
authors.affiliation: Division of Epidemiology, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Kevin
authors.initials: K
authors.lastname: Brown
authors.affiliation: Department of Anthropology and School of the Environment, McGill University, Montreal, Quebec, Canada.
authors.forename: Kim
authors.initials: K
authors.lastname: Valenta
authors.affiliation: Division of Epidemiology, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Fisman
authors.affiliation: Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Simor
authors.affiliation: Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Nick
authors.initials: N
authors.lastname: Daneman
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000009:adverse effects*; D016360:Clostridioides difficile; D003015:Clostridium Infections / Q000453:epidemiology*; D015897:Comorbidity; D003428:Cross Infection / Q000453:epidemiology*; D003967:Diarrhea / Q000453:epidemiology; D004334:Drug Administration Schedule; D011307:Drug Prescriptions / Q000706:statistics & numerical data*; D005260:Female; D006760:Hospitalization; D006784:Hospitals, Teaching; D006801:Humans; D015994:Incidence; D007297:Inpatients / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D009864:Ontario / Q000453:epidemiology; D010818:Practice Patterns, Physicians' / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors
chemical_list: D000900:Anti-Bacterial Agents