Pertussis, Bordetella

Key Features

Essentials of Diagnosis

• Predominantly occurs in infants under age 2 years

• Adolescents and adults are reservoir of infection

• Two-week prodromal catarrhal stage of malaise, cough, coryza, and anorexia

• Paroxysmal cough ending in a high-pitched inspiratory "whoop"

• Absolute lymphocytosis, often striking; nasopharyngeal culture confirms diagnosis

General Considerations

• An acute infection of the respiratory tract caused by Bordetella pertussis, a gram-negative coccobacillus

• Infection is transmitted by respiratory droplets

• The incubation period is 7–17 days

• Neither immunization nor disease confers lasting immunity to pertussis

• The diagnosis often is not considered in adults, who may not have a typical presentation; cough persisting more than 2 weeks is suggestive of pertussis

Clinical Findings

Symptoms and Signs

• Symptoms of classic pertussis last about 6 weeks and are divided into three consecutive stages

• The catarrhal stage

  • Characterized by its insidious onset

  • Lacrimation, sneezing, coryza, anorexia, and malaise

  • Hacking night cough that tends to become diurnal

• The paroxysmal stage

  • Characterized by bursts of rapid, consecutive coughs followed by a deep, high-pitched inspiration (whoop)

• The convalescent stage

  • Usually begins 4 weeks after onset of the illness with a decrease in the frequency and severity of paroxysms of cough

Differential Diagnosis

• Viral or bacterial pneumonia

• Asthma

• Other causes of chronic cough in adults

  • Postnasal drip

  • Gastroesophageal reflux disease

  • Tuberculosis

  • Mycobacterium avium complex

• Bronchiolitis, eg, respiratory syncytial virus (children)

• Croup (children)

Diagnosis

• The white blood cell count is usually 15,000–20,000/mcL (15–20 × 10⁹/L) (rarely, as high as 50,000/mcL (50 × 10⁹/L) or more), 60–80% of which are lymphocytes

• The organism can be cultured from the nasopharynx using a special medium (eg, Bordet-Gengou agar)

Treatment

Medications

• Erythromycin, 500 mg orally four times daily for 7 days

• Azithromycin, 500 mg orally on day 1, then 250 mg orally once daily for 4 days

• Clarithromycin, 500 mg orally twice daily for 7 days

• Trimethoprim-sulfamethoxazole, 160–800 mg orally twice a day for 7 days

• Treatment shortens the duration of carriage and may diminish the severity of coughing paroxysms

• Same regimens are indicated for prophylaxis of contacts to an active case of pertussis who are exposed within 3 weeks of the onset of cough in the index case

Outcome

Prevention

• Immunizations (Table 30–7)

• Acellular pertussis vaccine is recommended for all infants, combined with diphtheria and tetanus toxoids (DTaP)

• Infants and susceptible adults with significant exposure should receive prophylaxis with an oral macrolide

• Adults of all ages (including those > 64 years) should receive a single dose of ...