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Microbiology · Other Gram-negative rods

Bordetella pertussis !

  • Bacterium
  • Gram-negative
  • Droplet
  • Exam priority: medium

The whooping cough bacterium: coughing fits that last weeks. In babies under one year it can cause apnea and death.

Updated 2026-11-01

Also called: whooping cough bacillus

At a glance

Gram
Gram-negative
Shape
Small coccobacillus
Oxygen
Strict aerobe
Family
Alcaligenaceae
Stain
Gram: small red coccobacilli

Morphology

  • Small encapsulated Gram-negative coccobacillus
  • Fastidious: Bordet-Gengou or Regan-Lowe media
  • Attaches to ciliated respiratory cells

Transmission

  • Respiratory droplets from coughing or sneezing; very contagious, especially in the catarrhal stage
  • Babies usually catch it from siblings, parents or caregivers with mild symptoms
  • Droplet (on top of standard) until 5 days of effective antibiotics are completed

Reservoir: Humans only

Isolation precautions

What the care team adds to standard precautions.

Droplet
Surgical mask within about a metre; single room.

Virulence factors

  • Pertussis toxin: ADP-ribosylates Gi, raises cAMP and causes lymphocytosis, hyperinsulinemia and impaired defenses
  • Adenylate cyclase toxin: raises cAMP inside phagocytes
  • Tracheal cytotoxin: kills ciliated cells
  • Filamentous hemagglutinin and pertactin: attachment to ciliated epithelium

Diseases it causes

Clinical picture

  • Catarrhal stage of 1 to 2 weeks: a common cold, the most contagious stage
  • Paroxysmal stage: coughing fits followed by an inspiratory whoop and vomiting
  • Convalescent stage: the cough fades over weeks or months
  • Infants: apnea, cyanosis, pneumonia and death; often no whoop

Diagnosis

  • PCR of a nasopharyngeal swab or aspirate: fast and sensitive
  • Culture on Regan-Lowe or Bordet-Gengou: specific but difficult
  • Marked lymphocytosis on the infant's blood count
  • Serology useful late in the illness

Treatment

Macrolides (azithromycin; clarithromycin or erythromycin as alternatives), and trimethoprim-sulfamethoxazole when macrolides are not tolerated. Early antibiotics can soften the illness and always reduce spread; close contacts get prophylaxis.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

Prevention

  • DTP or DTaP vaccination in childhood with boosters
  • Tdap in every pregnancy to protect the newborn
  • Antibiotic prophylaxis for close contacts
  • Droplet precautions

Vaccine: Pertussis vaccine is in Colombia's PAI: within the pentavalent or hexavalent vaccine in the first months, DTP boosters, and acellular Tdap for pregnant women.

Test yourself

Think of the answer, then tap the question to see it.

Which stage of whooping cough is the most contagious?

The catarrhal stage, when it looks like a common cold.

How does pertussis toxin work?

It ADP-ribosylates and inactivates Gi, raises cAMP and, among other effects, causes lymphocytosis.

Which test is preferred to confirm pertussis in the first weeks?

PCR of a nasopharyngeal sample.

Why are pregnant women given Tdap?

To pass antibodies to the baby and protect it in the first months, when pertussis is most dangerous.

Which isolation precaution does a patient with pertussis need?

Droplet precautions, on top of standard, until 5 days of effective antibiotics are completed.

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Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: Chapter 16: Pertussis (CDC, 2024); About Whooping Cough (CDC, 2026).

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Representative model, for educational purposes only.