Lecture 48 - Bordetella - Nov 2006

Bordetella

Objectives At end of this lecture the students are expected to be able to: Assimilate the characteristics of Bordetella Recall their infections Recall the pathogenesis Recall the treatment and prevention

Characteristics/classification Small Gram-negative coccobacilli Cause infection of the respiratory tract Species: – Bordetella pertussis – Bordetella parapertussis – Bordetella bronchoseptica

Pertussis syndrome Per-tussis means severe cough Affects most infants and young children Bouts of paroxysmal cough each day No pause for air intake Tongue is fully protruded Fluid stream from the eye, nose and mouth The face becomes red or cyanotic

Pertussis syndrome When death seems imminent, a final cough clears the secretions Massive inspiration effort sucks air through the narrowed glottis High-pitched whoop is produced – “Whooping cough” Terminates with vomiting Illness can persist for many months

Epidemiology Degree of contact is important: – 80-90% of household non-immune siblings become infected – < 50% of non-immune child contact at school

Most severe and morbidity rate highest in the first 2 years of life Most fatal cases in 1st year of life One attack confers long-lasting immunity

Bordetella pertussis Fastidious, small Gram-negative rods; takes about 3 days to grow Strict aerobe Growth on charcoal-blood agar or BordetGengou medium Does not grow on Nutrient medium Produces 3 major agglutinogens, 1, 2 & 3

Pathogenesis Whooping cough (WC) is non-invasive infection of the respiratory mucosa Human is the only natural host Incubation period is 1-3 weeks, followed by a ‘catarrhal’ phase Followed 1 week later by a ‘paroxysmal’ phase – Increasing severity and paroxysmal cough – May last many weeks

Followed by equally prolonged ‘convalescent’ phase

Pathogenesis Colonization of ciliated epithelium of bronchi and trachea – Massive number – Agglutinogens play a vital and type-specific role in attachment

B. pertussis produces cytotoxin  paralyses the cilia  paroxysms of coughing Pertussis toxin (PT)  lymphocytosis

Laboratory diagnosis Pernasal swab Culture on charcoal-blood agar + low concentration of penicillin or cephalexin Detection of antigen in urine or serum Fluorescent-conjugated antiserum – nasopharyngeal specimen Detection of antibody CBC

Treatment Drug of choice is erythromycin Azihromycin Clarithromycin Cough suppressants and corticosteroids

Vaccination Suspension of whole bacterial cells killed by heat or chemicals – Conjugated - DTP

Safe and > 90% effective Administered by deep i.m injection Acellular vaccine