title: Pertussis Pseudo-outbreak linked to specimens contaminated by Bordetella pertussis DNA From clinic surfaces.
abstract: OBJECTIVE
  We investigated a pertussis outbreak characterized by atypical cases, confirmed by polymerase chain reaction (PCR) alone at a single laboratory, which persisted despite high vaccine coverage and routine control measures. We aimed to determine whether Bordetella pertussis was the causative agent and advise on control interventions.
  
  
  METHODS
  We conducted case ascertainment, confirmatory testing for pertussis and other pathogens, and an assessment for possible sources of specimen contamination, including a survey of clinic practices, sampling clinics for B pertussis DNA, and review of laboratory quality indicators.
  
  
  RESULTS
  Between November 28, 2008, and September 4, 2009, 125 cases were reported, of which 92 (74%) were PCR positive. Cases occurring after April 2009 (n = 79; 63%) had fewer classic pertussis symptoms (63% vs 98%; P < .01), smaller amounts of B pertussis DNA (mean PCR cycle threshold value: 40.9 vs 33.1; P < .01), and a greater proportion of PCR-positive results (34% vs 6%; P < .01). Cultures and serology for B pertussis were negative. Other common respiratory pathogens were detected. We identified factors that likely resulted in specimen contamination at the point of collection: environmentally present B pertussis DNA in clinics from vaccine, clinic standard specimen collection practices, use of liquid transport medium, and lack of clinically relevant PCR cutoffs.
  
  
  CONCLUSIONS
  A summer pertussis pseudo-outbreak, multifactorial in cause, likely occurred. Recommendations beyond standard practice were made to providers on specimen collection and environmental cleaning, and to laboratories on standardizing PCR protocols and reporting results, to minimize false-positive results from contaminated clinical specimens.
authors.affiliation: Epidemic Intelligence Service, Meningitis and Vaccine Preventable Diseases Branch, Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases, US Centers for Disease Control and Prevention, Atlanta, GA 30329, USA. smandal1@cdc.gov
authors.forename: Sema
authors.initials: S
authors.lastname: Mandal
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Tatti
authors.forename: Denise
authors.initials: D
authors.lastname: Woods-Stout
authors.forename: Pamela K
authors.initials: PK
authors.lastname: Cassiday
authors.forename: Amanda E
authors.initials: AE
authors.lastname: Faulkner
authors.forename: Matthew M
authors.initials: MM
authors.lastname: Griffith
authors.forename: Michael L
authors.initials: ML
authors.lastname: Jackson
authors.forename: Lucia C
authors.initials: LC
authors.lastname: Pawloski
authors.forename: Bari
authors.initials: B
authors.lastname: Wagner
authors.forename: Meghan
authors.initials: M
authors.lastname: Barnes
authors.forename: Amanda C
authors.initials: AC
authors.lastname: Cohn
authors.forename: Ken A
authors.initials: KA
authors.lastname: Gershman
authors.forename: Nancy E
authors.initials: NE
authors.lastname: Messonnier
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Clark
authors.forename: Maria-Lucia C
authors.initials: ML
authors.lastname: Tondella
authors.forename: Stacey W
authors.initials: SW
authors.lastname: Martin
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001886:Bordetella pertussis / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D016000:Cluster Analysis; D003120:Colorado; D003430:Cross-Sectional Studies; D059018:DNA Contamination; D004269:DNA, Bacterial / Q000235:genetics; D003951:Diagnostic Errors; D018563:Disease Notification; D004196:Disease Outbreaks; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007223:Infant; D007753:Laboratories / Q000592:standards; D008297:Male; D008875:Middle Aged; D009305:Nasopharynx / Q000382:microbiology; D010567:Pertussis Vaccine / Q000008:administration & dosage; D016133:Polymerase Chain Reaction / Q000592:standards; D011159:Population Surveillance; D012424:Rural Population; D013048:Specimen Handling / Q000592:standards; D014917:Whooping Cough / Q000175:diagnosis* / Q000453:epidemiology* / Q000382:microbiology / Q000517:prevention & control; D055815:Young Adult
chemical_list: D004269:DNA, Bacterial; D010567:Pertussis Vaccine