Bordetella pertussis: Difference between revisions
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Bordetella pertussis
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*Case-fatality rate of 1% in children under 6 months |
*Case-fatality rate of 1% in children under 6 months |
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+ | *Pneumonia is the most common complication, either caused by the disease itself for by coinfection (especially RSV) |
*Encephalopathy is a rare complication, usually in unimmunized children |
*Encephalopathy is a rare complication, usually in unimmunized children |
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**Begins weeks 2 to 4 after cough, with seizures and focal neurologic deficits |
**Begins weeks 2 to 4 after cough, with seizures and focal neurologic deficits |
Latest revision as of 15:35, 23 September 2024
Background
Microbiology
- Small, Gram-negative coccobacillus
- Fastidious, slow-growing, and strictly aerobic
- Catalase positive non-fermentative
- Pertussis toxin helps it to evade the host defenses
Pathophysiology
- Four steps to infection: attachment, evasion of host defenses, local damage, and systemic manifestations
- Virulence determined by filamentous hemagglutinin (FHA) and fimbriae (FIM) adhesins
- Required for tracheal colonization
- Pertussis toxin (PT) also plays a role
- Adenylate cyclase toxin (ACT) and PT allow it to evade host defenses
- ACT inhibits macrophages by catalysing ATP to cAMP
- PT delays neutrophil recruitment by suppressing G protein signaling pathways
- Tracheal cytotoxin (TCT) produces NO and damages the tracheal epitheleal cells
- Few systemic manifestations because it doesn't enter circulation
Clinical Manifestations
- Presents with cough lasting 14 days or more, with paroxysms of coughing, an inspiratory whoop, and post-tussive vomiting
- Incubation period of 7 to 10 days on average (range 5 to 21 days)
Young Children
- Three stages:
- Catarrhal stage, with rhinorrhea, nonpurulent conjuctivitis, occasional cough, and a low-grade fever; lasts 1 to 2 weeks.
- Paroxysmal stage, with fits of coughing and an inspiratory whoop; lasts 1 to 6 weeks. May have post-tussive emesis. Occasionally associated with hyperinsulinemia and hypoglycemia in infants.
- Convalescent stage, with the cough slowly resolving over 1 to 6 weeks, occasionally up to 8 weeks.
Adults
- Can present atypically, with less whooping and less post-tussive vomiting
- Coughing is seen in most patients, lasting longer than 21 days
- Mean duration 36 to 48 days
- Post-tussive vomiting is suggestive of pertussis
Carrier State
- Transient nasopharyngeal carriage in immunized children
Complications
- Case-fatality rate of 1% in children under 6 months
- Pneumonia is the most common complication, either caused by the disease itself for by coinfection (especially RSV)
- Encephalopathy is a rare complication, usually in unimmunized children
- Begins weeks 2 to 4 after cough, with seizures and focal neurologic deficits
- Pulmonary hypertension
- Pneumonia and urinary incontinence are common in older patients
- The paroxysms of coughing can also cause subconjunctival hemorrhages, syncope, and rib fractures
Diagnosis
- Nasopharyngeal swab/aspirate culture
- Sensitivity 15 to 80%
- PCR
- Serology
- Antibodies (IgG and IgA) against GHA, agglutinogen, or PT
- IgG rises 2 to 3 weeks after infection or immunization (1 week after booster)
- Look for a two-fold increase in IgG to diagnose acute infection
- Antigens including PT
- Antibodies (IgG and IgA) against GHA, agglutinogen, or PT
Management
- Treat within 21 days of symptom onset (except if <1 mo. old, treat regardless of duration)
- In children
- Azithromycin 10 mg/kg on day 1 followed by 5 mg/kg/d for 4 days
- Erythomycin 40-50 mg/kg/d divided qid for 7-14 days
- Clarithromycin 15 mg/kg/d divided bid for 7 days
- Azithromycin for children <1 year
- In infants <1 mo, azithromycin 10 mg/kg/d for 5 days
- In adults
- Azithromycin 500mg followed by 250 mg daily for 4 more days
- Erythomycin 500 mg qid for 7-14 days
- Clarithromycin 500 mg bid for 7 days
Prevention
Infection Control
- Droplet precautions
- Duration
- Treated: after 5 days of effective treatment
- Untreated: after 3 weeks from onset of paroxysms
- Communicable from onset of catarrhal stage to 3 weeks after onset of coughing or paroxysms
Post-Exposure Prophylaxis
- Consider prophylaxis of close contacts (face-to-face within 3 feet), third-trimester pregnancy, infants, and healthcare workers
- Should be considered up to 21 days following last contact
- Options include:
- Azithromycin 500 mg for one day followed by 250 mg for 4 more days
- Erythromycin 500 mg qid for 7 to 14 days
- Clarithromycin 500 mg bid for 7 days
Immunization
- Options include whole-cell (DTP) and acellular (DTaP or Tdap)
- Acellular removed lipopolysaccharide so is less reactive, but is as or more effective than whole cell
- There was a fear of encephalopathy and SIDS with DTP
- Acellular has PT, the two hemagluttinins, and protectin
- DTaP (diphtheria toxoid, tetanus toxoid, and acellular pertussis, pediatric formula)
- Given at 2, 4, 6, and 18 months, with booster at 4-6 years
- Tdap booster once in adulthood, and with every pregnancy for women (third trimester)
- Acellular removed lipopolysaccharide so is less reactive, but is as or more effective than whole cell
- None of the vaccines carry life-long immunity; even the immunity from the acellular pertussis vaccine wanes after 4-5 years