Immunology and Cell Biology (\994) 72. 143-151 An alteration in the host-parasite relationship in subjects with chronic bronchitis prone to recurrent episodes of acute bronchitis DIANA C. TAYLOR,' ROBERT L. CLANCY,' ALLAN W. CRlPPS,>-2 HENRY BUTT,3 LAWRENCE BARTLETT^ and KEITH MURREE-ALLEN** ^Faculty ofMedicine, The University of Newcastle, ^Australian Institute for Mucosal Immunology, Newcastle and Departments of ^Pathology and ^Thoracic Medicine. John Hunter Hospital. New Lambton. New South Wales. Australia Summary Acute episodes of bronchitis have been shown to be unequally distributed within a popula- tion of subjects with chronic bronchitis. Two groups were identified based on incidence of acute bronchitis — subjects who were 'infection-prone' (2-5 infections per year) and those who were 'non- infection-prone' (0-1 infections per year). Minor differences in clinical parameters existed, except for smoking experience. The non-infection-prone group included more current smokers, and the total smoking experience (in 'pack years') was significantly greater in this group. Between-year analysis demonstrated a stability of classification, established after a minimum of two years' prospective observation. Parameters of the host-parasite relationship were assessed in both groups. A significantly greater polybacterial colonization of the oropharynx was observed for chronic bronchitics, both infection-prone (/*< 0.0001) and non-infection-prone (-P< 0.001), compared with control subjects. Infection-prone chronic bronchitics had significantly greater total bacteria cultured from the oropharynx compared to the non-in feet ion-prone group {P < 0.05); adherence of indigenous microflora to buccal epithelial cells, in particular Gram-positive cocci {P < 0.01) and in vitro adherence of non-serotypable Haemophilus influenzae to buccal cells {P < 0.05) compared with the control and non-infection-prone groups. These studies suggest that an important variation in subjects with chronic bronchitis is the binding capacity of epithelial cells for bacteria, which when increased enhances susceptibility to coloni- zation and clinical infection. Key words: bacterial colonization patterns, COLD, host-parasite relationship, infection rate, non- serotypable Haemophilus influenzae. Introduction Acute bronchitis in subjects with chronic lung disease is a significant complication, often precipitating respi- ratory and cardiac failure. It is characterized by the production of purulent sputum, occurring as an in- traluminal exudate in response to bacterial coloniza- tion of the mucosa. Little is known about the pathogen- esis of acute bronchitis. A polybacterial colonization of the airways frustrates the fulfilment of Koch's postu- lates in supporting a role in pathogenesis by any spe- cific microbe.' A factor not previously analysed is the Correspondence: Professor R. L. Clancy. Faculty of Medicine, David Maddison Clinical Sciences Building, Royal Newcastle Hospital, Newcastle. NSW 2300, Australia. Received 15 April 1993; accepted 15 July 1993. clinical observation that subjects with apparently sim- ilar degrees of lung damage do not appear to be equally prone to recurrent episodes of acute bronchitis. The demonstration that a sub-group of subjects was rela- tively infection-prone would facilitate study of patho- genesis by providing an opportunity to identify differ- ences that may exist between these groups. Descending bacterial colonization of the airways has been consid- ered central to the pathogenesis of acute bronchitis^, with prior attachment of bacteria to the epithelium a prerequisite to colonization.^ This study addresses a new approach to understanding variations in the host- parasite relationship that determines acute bronchitis, by first validating the existence of 'infection-prone' and 'non-infection-prone' subjects with chronic bron- chitis, and second, by using data obtained from these