View source for Bordetella pertussis

==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 [[Usual incubation period::7 to 10 days]] on average (range [[Incubation period 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

==Management==

*Treat within 21 days of symptom onset (except if &lt;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 &lt;1 year
*In infants &lt;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)
*None of the vaccines carry life-long immunity; even the immunity from the acellular pertussis vaccine wanes after 4-5 years

{{DISPLAYTITLE:''Bordetella pertussis''}}
[[Category:Gram-negative coccobacilli]]
[[Category:Respiratory infections]]
[[Category:Pediatrics]]