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Micro - Bordetella Pertussis (Intro (accounts for approx 7% of coughs in…
Micro - Bordetella Pertussis
Intro
aka whooping cough
v small gram -ve coccobacillus
human only
strict aerobe
capsulated
highly infectious
transmitted by inhalation (droplet spread)
attaches to ciliated cells via fimbriae + filamentous haemaglutinin pertactin (P69) protein (resists innate mucociliary clearance)
milder in adults (often the source of infection for children)
accounts for approx 7% of coughs in adults
under-dxed
if lasts > 2 wks 10-20% probability of pertussis
Stages of Whooping cough
total duration = 3 months
Catarrhal stage
1-2 wks
most infectious
non specific symptoms (malaise, rhinorrhoea, mild cough)
Paroxysmal stage
2-4 wks
paroxysmal cough
vigorous
severe
occurs on single expiration, followed by vigorous inspiration
post-tussis vomiting
convalescent stage
gradual reduction in cough frequency + severity
3-4 wks
Dx
clinical features
lab tests
culture
no blood culture- organism doesn't enter bloodstream
aspirate nasopharyngeal secretions in young children
nasopharyngeal swab in adults
must be on selective + enriched agar
e.g. charcoal-blood agar
must have antibiotics to inhibit growth of normal flora
can take up to 10 days
not v sensitive
needs special transport medium, rapid transport + notify lab in advance
NAAT
of perinasal swab / nasopharyngeal aspirate
more sensitive + faster than culture
Serology
more useful for epidemiology
anti-pertussis IgG detected 2 wks after symptom onset
WCC - absolute lymphocytosis
Tx
primarily supportive (e.g. fluids)
possibly hospitalisation + ICU in v young
erythromycin or clarithromycin (macrolides) may eliminate disease + prevent transmission if given in catarrhal stage
Prevention
universal infant vaccine recommended everywhere
previously whole cells vaccine (killed organism)
Now acellular vaccine containing antigen used
less SEs
in Ire given in conjunction with diphtheria + tetanus (DPT)
@ 2,4,6 months, with booster @ 4-5 yrs
Reasons for resurgence
reduced herd immunity
improved Dx methods
reinfection can occur
acellular vaccine less long-term (another booster recommended @ 11-14 y/o, when pregnant + for healthcare workers)
Complications
hospitalisation in 20%
pneumonia
seizures
encephalopathy
death
endotoxin
cytotoxic - disrupts host cell
paralyses cilia
causing paroxysms of coughing
bronchioles become blocked with inflamm cells, lymphocytes + mucus (bronchiolar obstruction)
alveolar collapse - diminished oxygenation of blood
LPS