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Infect. Immun., 03 1995, 899-902, Vol 63, No. 3
M Kubiet and R Ramphal
Nontypeable Haemophilus influenzae strains are the most common pathogens
encountered in patients with chronic bronchitis. These organisms
chronically colonize the airways of patients and occasionally cause
bacteremia. Nontypeable H. influenzae strains have been demonstrated
microscopically to bind to mucus, but quantitative studies of adhesion have
not been published to date. We have therefore developed a reproducible
microtiter plate assay to study mucin binding and have examined the
adhesion of sputum and blood strains of nontypeable H. influenzae. The
assay is similar to that described for Pseudomonas aeruginosa (S.
Vishwanath and R. Ramphal, Infect. Immun. 45:197-202, 1984), but notably 2%
Tween 20 is used to desorb bacteria from the wells to quantitate bacterial
binding. Using a standard strain, we have established that 1 h of
incubation is optimum with an inoculum of < or = 5 x 10(8) CFU/ml. The
standard strain binds to bronchitic and cystic fibrosis mucins equally well
but binds less to bronchiectasis mucins. It does not bind to bovine serum
albumin or fetuin. We have also examined the levels of adhesion of freshly
isolated sputum and bacteremia strains and find very significant
differences in adhesion. Blood strains bound six to seven times less than
sputum strains ([13.8 +/- 7] x 10(2) per well versus [102 +/- 43] x 10(2);
P < 0.001). Studies with adhesion to lactoferrin, another glycosylated
protein, revealed variable binding of respiratory strains but marked
binding of blood strains compared with mucin. An isogenic pair of
respiratory and blood isolates was examined by electron microscopy but did
not show surface differences. We speculate that bacteremic strains studied
may have masked, lost, or downregulated adhesin production to allow them to
escape from mucins or upregulated adhesins for lactoferrin to invade the
bloodstream.
Copyright © 1995, American Society for Microbiology
Adhesion of nontypeable Haemophilus influenzae from blood and sputum to human tracheobronchial mucins and lactoferrin
Department of Medicine, University of Florida College of Medicine, Gainesville 32610.
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