Infectious Disease · Respiratory Infections
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Pertussis is caused by the gram-negative coccobacillus Bordetella pertussis, which produces pertussis toxin to disable G-protein signaling.
The clinical course follows three stages: the catarrhal stage (most contagious), the paroxysmal stage (classic cough), and the convalescent stage.
Patients in the paroxysmal stage exhibit post-tussive emesis and a high-pitched inspiratory whoop following severe coughing fits.
The gold standard for diagnosis is a nasopharyngeal culture or PCR testing, which is most sensitive during the first two weeks of illness.
Macrolides (e.g., azithromycin) are the first-line treatment to reduce transmission, though they do not significantly alter the clinical course if started after the catarrhal stage.
Post-exposure prophylaxis with a macrolide is indicated for all close contacts regardless of their vaccination status.
Prevention is achieved through the DTaP vaccine series in children and the Tdap booster in adolescents, adults, and pregnant women during every pregnancy.
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A 6-year-old boy is brought to the clinic by his mother due to a 3-week history of a severe, persistent cough. The mother reports that the child has coughing fits so intense that he occasionally vomits afterward. He is up to date on all childhood immunizations. On physical exam, the child appears well between coughing episodes, but he exhibits a high-pitched inspiratory sound after a paroxysm of coughing. A nasopharyngeal swab is obtained for diagnostic testing.
What is the most appropriate management for the patient's household contacts?
Post-exposure prophylaxis with a macrolide
This question tests the requirement for post-exposure prophylaxis for all close contacts of a confirmed pertussis case, regardless of their prior vaccination status, to limit community spread.
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Etiology / Epidemiology
Highly contagious Bordetella pertussis infection; primarily affects unvaccinated or waning immunity adolescents/adults.
Clinical Manifestations
Three stages: catarrhal, paroxysmal, and convalescent. Whooping cough and post-tussive emesis are classic.
Diagnosis
PCR of nasopharyngeal swab is the gold standard within the first 3 weeks of symptom onset.
Treatment
Azithromycin is the first-line treatment; macrolide allergy requires TMP-SMX.
Prognosis
Complications include pneumonia and rib fractures; post-exposure prophylaxis is mandatory for close contacts.
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Epidemiology & Etiology
Caused by the gram-negative coccobacillus Bordetella pertussis. Transmission occurs via respiratory droplets. Despite vaccination, immunity wanes over 5-10 years, leading to outbreaks in adolescents and adults who serve as reservoirs for infants.
Pertinent Anatomy
The pathogen colonizes the ciliated respiratory epithelium. It produces toxins that paralyze cilia, preventing the clearance of mucus and debris from the tracheobronchial tree.
Pathophysiology
The pertussis toxin increases cyclic AMP, leading to lymphocytosis and impaired phagocyte function. The clinical course follows the catarrhal stage (mild URI symptoms), the paroxysmal stage (severe coughing fits), and the convalescent stage (gradual recovery).
Clinical Manifestations
Patients present with the whoop—a high-pitched inspiratory sound following a paroxysm of coughing. Post-tussive emesis is a highly specific finding. Apnea is a critical red flag in infants, requiring immediate hospitalization.
Diagnosis
The PCR of nasopharyngeal swab is the preferred diagnostic test. Culture is highly specific but has low sensitivity and is rarely used. Lymphocytosis (often >15,000/mm³) is a common CBC finding in children.
Treatment
Azithromycin is the drug of choice to reduce transmission and symptom duration. TMP-SMX is the alternative for patients with macrolide intolerance. Treatment is most effective if initiated during the catarrhal stage.
Prognosis
Most adults recover fully, but infants are at high risk for pneumonia, seizures, and encephalopathy. Rib fractures are a common complication of intense coughing paroxysms.
Differential Diagnosis
Viral URI: lacks the severe paroxysmal cough
Mycoplasma pneumonia: usually presents with lower-grade systemic symptoms
Asthma: wheezing is expiratory, not inspiratory
GERD: lacks the infectious prodrome
Foreign body aspiration: sudden onset without URI symptoms