Catarrhal
Summary
Catarrhal refers to inflammation of a mucous membrane with profuse mucus production. It names the first stage of pertussis, which resembles a common cold, is the most contagious period, and is the only stage in which antibiotics shorten the illness.
Detail
During the catarrhal stage Bordetella pertussis attaches to ciliated respiratory epithelium by filamentous haemagglutinin and pertactin and releases tracheal cytotoxin, which destroys ciliated cells and impairs clearance, and pertussis toxin, which ADP-ribosylates the inhibitory Gi protein, disinhibiting adenylate cyclase and raising cAMP. Symptoms are indistinguishable from a viral upper respiratory infection — rhinorrhoea, sneezing, mild cough, minimal fever — which is precisely why the diagnosis is missed and transmission occurs; it lasts one to two weeks. Macrolides given now abort progression, whereas in the paroxysmal stage they only limit spread. Nasopharyngeal PCR is the diagnostic test of choice. Prophylaxis of household contacts with azithromycin is indicated regardless of vaccination status. The name also appears in Moraxella catarrhalis, a gram-negative diplococcus causing otitis media, sinusitis, and COPD exacerbations, and which is characteristically beta-lactamase positive.
Sources
- Levinson Medical Microbiology and Immunology
- Nelson Textbook of Pediatrics
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