title: Does doxycycline protect against development of Clostridium difficile infection?
abstract: BACKGROUND
  Receipt of antibiotics is a major risk factor for Clostridium difficile infection (CDI). Doxycycline has been associated with a lower risk for CDI than other antibiotics. We investigated whether doxycycline protected against development of CDI in hospitalized patients receiving ceftriaxone, a high-risk antibiotic for CDI.
  
  
  METHODS
  We studied adults admitted to an academic county hospital between 1 June 2005 and 31 December 2010 who received ceftriaxone to determine whether the additional receipt of doxycycline decreased the risk of CDI. Patients were followed from first administration of ceftriaxone to occurrence of CDI or administrative closure 30 days later.
  
  
  RESULTS
  Two thousand three hundred five unique patients comprising 2734 hospitalizations were studied. Overall, 43 patients developed CDI within 30 days of ceftriaxone receipt, an incidence of 5.60 cases per 10 000 patient-days. The incidence of CDI was 1.67 cases per 10 000 patient-days in those receiving doxycycline, compared to 8.11 per 10 000 patient-days in those who did not receive doxycycline. In a multivariable model adjusted for age, gender, race, comorbidities, hospital duration, pneumonia diagnosis, surgical admission, and duration of ceftriaxone and other antibiotics, for each day of doxycycline receipt the rate of CDI was 27% lower than a patient who did not receive doxycycline (hazard ratio, 0.73; 95% confidence interval, .56-.96).
  
  
  CONCLUSIONS
  In this cohort of patients receiving ceftriaxone, doxycycline was associated with lower risk of CDI. Guidelines recommend this combination as a second-line regimen for some patients with community-acquired pneumonia (CAP). Further clinical studies would help define whether doxycycline-containing regimens should be a preferred therapy for CAP.
authors.affiliation: Department of Internal Medicine, Division of Infectious Diseases, University of California, San Francisco, CA 94110, USA. sarah.doernberg@ucsf.edu
authors.forename: Sarah B
authors.initials: SB
authors.lastname: Doernberg
authors.forename: Lisa G
authors.initials: LG
authors.lastname: Winston
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Deck
authors.forename: Henry F
authors.initials: HF
authors.lastname: Chambers
mesh_terms: D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D019072:Antibiotic Prophylaxis; D002443:Ceftriaxone / Q000627:therapeutic use; D016360:Clostridioides difficile / Q000302:isolation & purification*; D015331:Cohort Studies; D004318:Doxycycline / Q000627:therapeutic use*; D004761:Enterocolitis, Pseudomembranous / Q000188:drug therapy / Q000382:microbiology / Q000517:prevention & control*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models
chemical_list: D000900:Anti-Bacterial Agents; D002443:Ceftriaxone; D004318:Doxycycline