Bordetella pertussis - Whooping Cough

Key Points

Pertussis (Bordetella pertussis) Diagnosis

  • CDC 2010 case definition and classification (see table below)

CDC 2010 Case Definition

Clinical Criteria

  • Cough lasting >2 weeks
  • One or more symptoms
    • Paroxysms of cough
    • Inspiratory whoop
    • Posttussive vomiting
  • In epidemic setting, acute coughing illness lasting >2 weeks

Laboratory Criteria  (one or both)

  • Isolation of B. pertussis in culture
  • Positive PCR test for B. pertussis

Case Classification

Probable

  • Meets clinical criteria definition
  • Not laboratory confirmed
  • Not epidemiologically linked to a laboratory-confirmed case

Confirmed  (one of the following)

  • Acute cough illness of any duration with a positive culture for B. pertussis
  • Meets clinical criteria and confirmed by PCR
  • Meets clinical criteria and epidemiologically linked directly to  a case confirmed by either culture or PCR
  • Laboratory testing for pertussis diagnosis (see table below)

Laboratory Testing

PCR
  • Optimal timing is <4 weeks post cough onset 
  • Highly sensitive
  • Best sensitivity with nasopharyngeal (NP) swab or aspirate (do not use calcium alginate swabs – shown to interfere with PCR)
Culture
  • Optimal timing is <2 weeks post cough onset
  • NP aspirates may allow better recovery than NP swabs (cotton swabs may inhibit B. pertussis)
  • Decreased sensitivity in persons with cough >2 weeks, receiving antibiotics, of older age, immunosuppressed, or previously vaccinated
Serology (IgA, IgG, IgM)
  • Sensitivity is highly dependent on collection of acute and convalescent sera (single unpaired specimens are typically not useful)
  • Not confirmatory for CDC case definition
DFA
  • Low sensitivity
  • Not confirmatory for CDC case definition

Diagnosis

Indications for Testing

  • Patients with predominant complaint of persistent cough, especially in the absence of fever, sore throat, hoarseness, tachypnea or wheeze

Criteria for Diagnosis

Laboratory Testing

  • Refer to Key Points tab

Differential Diagnosis

Clinical Background

Pertussis is a highly infectious and contagious disease commonly referred to as whooping cough. It is caused by the bacterium Bordetella pertussis.

Epidemiology

  • Incidence – 1-5/100,000
    • Recent resurgence of disease in industrialized countries
  • Age – peak incidence <6 months or >14 years of age
    • Primarily seen in those with waning immunity from childhood vaccination (immunity begins to wane during early adolescence)
    • Significant incidence in unimmunized infants <1 year
  • Occurrence – infection occurs most frequently in late spring and summer
  • Transmission
    • Adult and teenage children with common cold symptoms are significant reservoirs of the organism and the source of outbreaks in highly susceptible populations
    • Transmitted by respiratory droplets (B. pertussis causes disease only in humans)
      • Infection rates >90% in susceptible populations

Organism

  • B. pertussis is a gram-negative pleomorphic coccobacillus
  • Multiple virulence factors are produced that aid in organism attachment and production of disease
    • Pertussis toxin is responsible for many disease effects
  • B. parapertussis is a related species that may cause a milder form of pertussis syndrome

Clinical Presentation

  • Nonspecific viral upper respiratory tract infection-like symptoms
    • Disease spread often not recognized due to mild symptoms in immunized persons
    • Secondary spread common in families and schools
  • After 7-10 day incubation, a prolonged course ensues consisting of 3 overlapping stages
    • Catarrhal (1-2 weeks post infection [PI])
    • Paroxysmal coughing (1-4 weeks PI)
    • Convalescent (4-6 weeks PI)
  • Partially immune persons and infants >6 months may not manifest all of the typical symptoms
    • Paroxysmal coughing may be absent
  • Classic pertussis is generally diagnosed clinically
    • Inspiratory whoop
    • Lymphocytosis
    • Paroxysmal cough
    • Posttussive vomiting
  • Atypical pertussis may occur with mild or absent symptoms in adults and previously vaccinated children
    • Atypical pertussis is common, endemic and usually unrecognized in adults
  • Secondary complications
    • Respiratory 
    • Nonrespiratory
    • Death – fulminant course more common in very young infants

Prevention

  • Vaccination
  • Pediatric age groups – combined Hib and DTaP
  • Adult revaccination
    • ACP recommendation – during teen years, in patients 11-64 years, and conditionally >65 years (Tdap)

Indications for Laboratory Testing

  • Tests generally appear in the order most useful for common clinical situations
  • Click on number for test-specific information in the ARUP Laboratory Test Directory
Test Name and Number Recommended Use Limitations Follow Up
Bordetella pertussis/parapertussis by PCR 0065080
Method: Qualitative Polymerase Chain Reaction

Method of choice for direct detection of B. pertussis or B. parapertussis for patients with cough and no previous antibiotic therapy

  • Adult patients with persistent cough in whom pertussis is suspected
  • Children with epidemiological and clinical features of disease

Additionally, CDC recommends B. pertussis culture

Patients with pertussis may remain PCR-positive for variable periods following treatment

Negative result does not rule out the presence of B. pertussis DNA in concentrations below detection level of assay

False positives for B. pertussis may occur in samples containing B. holmesii DNA; false positives for B. parapertussis may occur in samples containing B. bronchiseptica DNA

 
Bordetella pertussis Culture 0060117
Method: Culture/Identification

Gold standard test for diagnosing pertussis

May test for B. pertussis in adults who have consistent epidemiological and clinical features of disease

In addition, consider B. pertussis by PCR

Highly specific only in acute disease phase

Negative culture does not exclude the possibility of B. pertussis infection

Successful culture requires special media and incubation up to 7 days; also highly dependent on specimen collection, transportation and laboratory techniques

Diagnostic sensitivity <60% when specimen obtained after early catarrhal stage or after treatment with certain antibiotics; reduced sensitivity in adults and vaccinated patients

 
Bordetella pertussis Antibodies, IgA and IgG by ELISA with Reflex to Immunoblot 2001774
Method: Semi-Quantitative Enzyme-Linked Immunosorbent Assay/Qualitative Immunoblot

May aid in diagnosis of pertussis in adults with prolonged cough in later stages of the disease; however, in most cases serologic testing is not recommended for diagnosis of active pertussis infection

Positive or equivocal ELISA results are confirmed by immunoblot; if IgA ≥1.2 U/mL, IgA immunoblot will be added; if IgG ≥2.5 U/mL, IgG immunoblot will be added

Only use when paired (acute and convalescent) samples show significant change in antibody titer

Test does not satisfy CDC criteria for diagnosing pertussis

 
Additional Tests Available
 
Click the plus sign to expand the table of additional tests.
Test Name and NumberComments
Bordetella pertussis Antibodies, IgA, IgG, and IgM by Immunoblot 2004328
Method: Qualitative Immunoblot

May aid in diagnosis of pertussis in adults with prolonged cough in later stages of the disease; cannot be used to confirm infection

Bordetella pertussis Antibodies, IgA, IgG, and IgM by ELISA with Reflex to Immunoblot 2001775
Method: Semi-Quantitative Enzyme-Linked Immunosorbent Assay/Qualitative Immunoblot

Cannot be used to confirm infection

Bordetella pertussis Antibody, IgG by ELISA 2005268
Method: Semi-Quantitative Enzyme-Linked Immunosorbent Assay

Cannot be used to confirm infection

Bordetella pertussis Antibody, IgG by ELISA with Reflex to Immunoblot 2001768
Method: Semi-Quantitative Enzyme-Linked Immunosorbent Assay/Qualitative Immunoblot

Cannot be used to confirm infection

Bordetella pertussis Antibody, IgM by ELISA with Reflex to Immunoblot 2001769
Method: Semi-Quantitative Enzyme-Linked Immunosorbent Assay/Qualitative Immunoblot

Cannot be used to confirm infection

Gram Stain 0060101
Method: Stain/Microscopy
Bordetella pertussis DFA 2004667
Method: Direct Fluorescent Antibody Stain

DFA is not recommended; refer instead to culture or PCR

Bordetella pertussis Antibodies, IgG and IgM by ELISA with Reflex to Immunoblot 2001784
Method: Semi-Quantitative Enzyme-Linked Immunosorbent Assay/Qualitative Immunoblot

Cannot be used to confirm infection

Bordetella pertussis Antibody, IgA by Immunoblot 2004316
Method: Qualitative Immunoblot

Cannot be used to confirm infection

Bordetella pertussis Antibody, IgG by Immunoblot 2004327
Method: Qualitative Immunoblot

Cannot be used to confirm infection

Bordetella pertussis Antibody, IgM by Immunoblot 2004326
Method: Qualitative Immunoblot

Cannot be used to confirm infection