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Open Access Highly Accessed Research article

Moraxella catarrhalis acquisition, airway inflammation and protease-antiprotease balance in chronic obstructive pulmonary disease

Ganapathi I Parameswaran15*, Catherine T Wrona3, Timothy F Murphy124 and Sanjay Sethi34

Author Affiliations

1 Division of Infectious Diseases, University at Buffalo, State University of New York, 701 Ellicott Street, Buffalo, NY 14203, USA

2 Department of Microbiology, University at Buffalo, State University of New York, 701 Ellicott Street, Buffalo, NY 14203, USA

3 Division of Pulmonary and Critical Care, University at Buffalo, State University of New York, 3495 Bailey Ave, Buffalo, NY 14215, USA

4 VA Western New York Healthcare System, 3495 Bailey Ave, Buffalo, NY 14215, USA

5 Kaleida Health System, 100 High Street, Buffalo, NY 14203, USA

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BMC Infectious Diseases 2009, 9:178  doi:10.1186/1471-2334-9-178

Published: 15 November 2009

Abstract

Background

Moraxella catarrhalis causes approximately 10% of exacerbations in chronic obstructive pulmonary disease (COPD) and also colonizes the lower airway in stable patients. Little is known about the effects of colonization by M. catarrhalis on airway inflammation and protease-antiprotease balance, and how these changes compare to those seen during exacerbations. Since COPD is a progressive inflammatory disease, elucidating the effects of bacterial colonization and exacerbation on airway inflammation is relevant to understanding disease progression in COPD. Our aims were (1) Analyze changes in airway inflammation in colonization and exacerbation of COPD due to M. catarrhalis; (2) Explore protease-antiprotease balance in colonization and exacerbation due to M. catarrhalis. Our hypothesis were (1) Acquisition of a new strain of M. catarrhalis in COPD increases airway inflammation from baseline and alters the protease-antiprotease balance towards a more proteolytic environment; (2) These changes are greater during exacerbations associated with M. catarrhalis as compared to colonization.

Methods

Thirty-nine consecutive COPD patients with 76 acquisitions of a new strain of M. catarrhalis over a 6-year period were identified in a prospective study. Seventy-six pre-acquisition sputum supernatant samples, obtained just before acquisition of M catarrhalis, and 76 acquisition samples (34 were associated with exacerbation, 42 with colonization) were analyzed for IL-8, TNF-α, Neutrophil Elastase (NE) and Secretory leukocyte protease inhibitor (SLPI). Changes were compared in paired samples from each patient.

Results

IL-8, TNF-α and NE were significantly elevated after acquisition of M. catarrhalis, compared to pre-acquisition samples (p =< 0.001 for all three). These changes were present in colonization (p = 0.015 for IL-8; p =< 0.001 for TNF-α and NE) as well as in exacerbation (p =< 0.001 for all three), compared to pre-acquisition levels. SLPI was significantly lower after acquisition (p =< 0.001), in colonization (p =< 0.001) as well as in exacerbation (p = 0.004), compared to pre-acquisition levels. SLPI levels correlated negatively with NE levels (R2 = 0.07; p = 0.001).

Conclusion

Acquisition of M. catarrhalis in COPD causes increased airway inflammation and worsening protease-antiprotease imbalance during exacerbations and also in colonization, even in the absence of increased symptoms. These effects could contribute to progression of airway disease in COPD.