Personal Medical Notes

1. Usually of young children, mild fever and an irritating cough, with characteristic 'whoop',
with cyanosis and vomiting. '100 day Cough'
Agent
B. pertussis 95% vs B. Parapertussis 5%.
Clinical disease is associated with encapsulated, phase 1 strains.
Infects only man. Source of infection is a case. Chronic carrier state doesn't exist.
Infective Material
Nasopharyngeal and Bronchial secretions
Infective Period
most infectious during catarrhal stage.
A week after exposure to about 3 weeks after the onset of paroxysmal stage although
communicability diminshes rapidly after the catarrhal stage.
There is no cross immunity with B. Parapertussis.
Environment
winter and spring season.
Mode of Transmission
droplet infection and direct contact.
Incubation Period
7-14 days, but not more than 3 weeks
Clinical Course
produces a local infection; the organism is not invasive. Multiplies on surface epithelium of
the respiratory tract and causes inflammation and necrosis of the mucosa leading to
secondary bacterial invasion.
Catarrhal stage, lasting for about 10 days. Lacrimation, sneezing, and coryza, anorexia
and malaise.
Paroxysmal stage, lasting for 2-4 weeks. Bursts of rapid , consecutive coughs followed by
'whoop', usually follwed by vomiting.
Convalescent stage, lasting for 1-2 weeks. Illnes genarally lasts for 6-8 weeks.
Complications are bronchitis, bronchopneumonia, and bronchiectasis.
Control
Early diagnosis is possible by only bacteriological examination of nasopharyngeal swabs.
Patient should be isolated until considered to be non-infectious.
Erythromycin, ampicillin, septran or tetracycline.
3 doses, each of 0.5 mL of DPT vaccine given IM, at 1 month interval, starting at 6 weeks
of age. Booster dose given at 18-24 months.
Morphology
gram-negative coccobacilli. Nonmotile, nonsporing.
Culture
aerobic, temperature is 35 to 6°C. Bordet-Gengou (Glycerol-potato-blood agar) medium.
Incubation for 48 to 72 hours, colonies are small, smooth, opaque, greyish white, refractile.
Hazy zone of hemolysis surrounds the colonies.

2. Biochemical reactions
Biochemically inactive. Does not ferment sugars, form indole, reduce nitrate, split urea or
utilise citrate. Oxidase positive, produces catalase.
Resistance
Killed by heating at 55°C for 30 minutes, drying, disinfectants.
Antigenic structure
1. Agglutinogen – All strains carry factor I and one or more of the other factors. Factor I to
6 present only in B. pertussis, 7 is found in all strains of the three species. Factor 12 is
specific for B. Bronchoseptica. Factor 14 for B. parapertussis.
2. Lipopolysaccharide – heat stable, endotoxin of the cell wall. Not protective.
3. Heat labile toxin (HLT)
4. Tracheal cytotoxin (TCT) – causes damage to the respiratory epithelium, makes more
prone to secondary infection.
5. Pertussis toxin (PT) – heat labile exotoxin, causes profound lymphocytosis.
7. Filamentous haemagglutinin (FHA) – mediates attachment of the bacteria to ciliated
epithelial cells of the respiratory tract. Also adheres to erythrocytes.
Pathogenesis
Incubation period 1 to 2 weeks. Transmitted by droplets. Last for 6 to 8 weeks. Three
stages, catarrhal, paroxysmal and convalescent. Each for two weeks.
Cases are maximally infective during catarrhal stage. During convalescent stage violent
spasm, continuous coughing, followed by ‘whoop’. During Convalescent stage, frequency
and severity of coughing gradually decreases.
Complications
Disease is self-limiting –
a) sub conjunctival haemorrhage due to the pressure effects of violent coughing.
2) bronco pneumonia and lung collapse.
3) convulsions and coma
Lab diagnosis
1. Microscopy – demonstration of bacilli in the respiratory secretions by fluorescent
antibody technique.
2. Culture –
a) prenasal swab – A swab is passed along the floor of the nasal cavity.
b) Cough plate method – Culture is held 10 to 15 cm in front of mouth during coughing.
Treatment
tetracycline, chloramphenicol, erythromycin, and ampicillin.
Prophylaxis
3 IM injections at intervals of 4 to 6 weeks. Given before the age of six months, booster at
the end of the first year. Vaccination is started at the age of six weeks.