title: Use of multilocus variable number of tandem repeats analysis genotyping to determine the role of asymptomatic carriers in Clostridium difficile transmission.
abstract: BACKGROUND
  Previous studies have suggested that asymptomatic carriers of toxigenic Clostridium difficile are a source of hospital-associated (HA) infections. Multilocus variable number of tandem repeats analysis (MLVA) is a highly discriminatory molecular subtyping tool that helps to determine possible transmission sources.
  
  
  METHODS
  Clostridium difficile isolates were recovered from perirectal swabs collected for vancomycin-resistant Enterococcus (VRE) surveillance as well as from clinical C. difficile toxin-positive stool samples from July to November 2009 at the University of Pittsburgh Medical Center Presbyterian (UPMC). MLVA was performed to determine the genetic relationships between isolates from asymptomatic carriers and patients with HA C. difficile infection (HA-CDI). Asymptomatic carriage and HA-CDI isolates were considered to be associated if the carriage isolate was collected before the HA-CDI isolate and if the MLVA genotypes had a summed tandem-repeat difference of ≤ 2.
  
  
  RESULTS
  Of 3006 patients screened, 314 (10.4%) were positive for toxigenic C. difficile, of whom 226 (7.5%) were detected only by VRE surveillance cultures. Of 56 incident cases of CDI classified as HA at UPMC during the study with available isolates, 17 (30%) cases were associated with CDI patients, whereas 16 (29%) cases were associated with carriers. Transmission events from prior bed occupants with CDI (n = 2) or carriers (n = 2) were identified in 4 of 56 cases.
  
  
  CONCLUSIONS
  In our hospital with an established infection control program designed to contain transmission from symptomatic CDI patients, asymptomatic carriers appear to have played an important role in transmission. Identification and isolation of carriers may be necessary to further reduce transmission of C. difficile in such settings.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, University of Pittsburgh School of Medicine.
authors.forename: Scott R
authors.initials: SR
authors.lastname: Curry
authors.forename: Carlene A
authors.initials: CA
authors.lastname: Muto
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Schlackman
authors.forename: A William
authors.initials: AW
authors.lastname: Pasculle
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Shutt
authors.forename: Jane W
authors.initials: JW
authors.lastname: Marsh
authors.forename: Lee H
authors.initials: LH
authors.lastname: Harrison
mesh_terms: D002353:Carrier State / Q000453:epidemiology / Q000382:microbiology* / Q000635:transmission; D016360:Clostridioides difficile / Q000235:genetics* / Q000302:isolation & purification; D003015:Clostridium Infections / Q000453:epidemiology / Q000382:microbiology* / Q000635:transmission*; D003428:Cross Infection / Q000382:microbiology* / Q000635:transmission*; D004269:DNA, Bacterial / Q000235:genetics; D005838:Genotype; D006801:Humans; D008403:Mass Screening; D018598:Minisatellite Repeats; D017720:Molecular Epidemiology; D010414:Pennsylvania / Q000453:epidemiology; D062486:Public Health Surveillance
chemical_list: D004269:DNA, Bacterial
keywords: Clostridium difficile; MLVA; genotyping; screening; transmission