title: Incidence of and risk factors for community-associated Clostridium difficile infection: a nested case-control study.
abstract: BACKGROUND
  Clostridium difficile is the most common cause of nosocomial infectious diarrhea in the United States. However, recent reports have documented that C. difficile infections (CDIs) are occurring among patients without traditional risk factors. The purpose of this study was to examine the epidemiology of CA-CDI, by estimating the incidence of CA-CDI and HA-CDI, identifying patient-related risk factors for CA-CDI, and describing adverse health outcomes of CA-CDI.
  
  
  METHODS
  We conducted a population-based, retrospective, nested, case-control study within the University of Iowa Wellmark Data Repository from January 2004 to December 2007. We identified persons with CDI, determined whether infection was community-associated (CA) or hospital-acquired (HA), and calculated incidence rates. We collected demographic, clinical, and pharmacologic information for CA-CDI cases and controls (i.e., persons without CDI). We used conditional logistic regression to estimate the odds ratios (ORs) for potential risk factors for CA-CDI.
  
  
  RESULTS
  The incidence rates for CA-CDI and HA-CDI were 11.16 and 12.1 cases per 100,000 person-years, respectively. CA-CDI cases were more likely than controls to receive antimicrobials (adjusted OR, 6.09 [95% CI 4.59-8.08]) and gastric acid suppressants (adjusted OR, 2.30 [95% CI 1.56-3.39]) in the 180 days before diagnosis. Controlling for other covariates, increased risk for CA-CDI was associated with use of beta-lactam/beta-lactamase inhibitors, cephalosporins, clindamycin, fluoroquinolones, macrolides, and penicillins. However, 27% of CA-CDI cases did not receive antimicrobials in the 180 days before their diagnoses, and 17% did not have any traditional risk factors for CDI.
  
  
  CONCLUSIONS
  Our study documented that the epidemiology of CDI is changing, with CA-CDI occurring in populations not traditionally considered "high-risk" for the disease. Clinicians should consider this diagnosis and obtain appropriate diagnostic testing for outpatients with persistent or severe diarrhea who have even remote antimicrobial exposure.
authors.affiliation: Center for Health Research, Kaiser Permanente Northwest, Portland, OR, USA. jennifer.l.kuntz@kpchr.org
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Kuntz
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Chrischilles
authors.forename: Jane F
authors.initials: JF
authors.lastname: Pendergast
authors.forename: Loreen A
authors.initials: LA
authors.lastname: Herwaldt
authors.forename: Philip M
authors.initials: PM
authors.lastname: Polgreen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000890:Anti-Infective Agents / Q000627:therapeutic use; D016360:Clostridioides difficile / Q000302:isolation & purification*; D017714:Community-Acquired Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology*; D003428:Cross Infection / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology*; D004761:Enterocolitis, Pseudomembranous / Q000188:drug therapy / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D012189:Retrospective Studies; D012307:Risk Factors
chemical_list: D000890:Anti-Infective Agents