Keywords: chronic bronchitis; mucosal immunity; respiratory tract infectionBacterial infection of the respiratory tract has long been recognized as playing a role in the course and pathogenesis of chronic obstructive pulmonary disease (COPD) (1-3). However, the precise role of bacteria is poorly understood and controversial. Bacteria cause many of the exacerbations that characterize the disease and, through chronic colonization, contribute to airway inflammation that is a hallmark of the disease (4, 5). COPD is the fourth most common cause of death in the world and is associated with enormous morbidity and health care costs (6, 7). Elucidating the dynamics of bacterial infection and characteriz- Studies performed decades ago emphasized the role of Haemophilus influenzae and Streptococcus pneumoniae in COPD (8-12). Interestingly, in classic studies by May (8) and Howell (9), Moraxella catarrhalis (then known as Neisseria catarrhalis) was isolated more often than H. influenzae and S. pneumoniae from sputum of adults with COPD. However, the bacterium was described as an "organism whose pathogenic propensities are known to be slight or non-existent" (8) and was thus ignored for decades. Point prevalence studies indicate that M. catarrhalis colonizes the respiratory tract of 5 to 32% of adults with COPD at any one time (8,9,(13)(14)(15)(16). Little is known about the duration of carriage, the relative frequency of M. catarrhalis as a cause of exacerbations or the human immune response, and its relationship to the clinical expression of carriage and disease. Studies of the human immune response to M. catarrhalis have been limited by the use of heterologous laboratory strains in immunoassays. The use of immunoassays that detect antibodies that bind to epitopes on the bacterial surface of the homologous infecting strain is important to detect potentially protective immune responses.We are conducting a prospective study in which we obtain clinical information, sputum, and serum samples monthly and during exacerbations in a cohort of patients with COPD. In previous work, on the basis of 57 months of follow-up, we have demonstrated that acquisition of a new strain of H. influenzae, M. catarrhalis, or S. pneumoniae is associated with the occurrence of an exacerbation (17). Furthermore, in previous work, we studied serum and sputum supernatants from 21 patients with exacerbations associated with M. catarrhalis to develop immunoassays to measure serum IgG and sputum IgA to antigens on the bacterial surface (18). The present study has elucidated the dynamics of carriage of M. catarrhalis in COPD on the basis of 81 months of follow-up, measured the systemic and mucosal antibody responses in 106 sets of serum and sputum samples to homologous infecting strains of M. catarrhalis, and related these immune responses to clinical aspects of carriage. Results of clinical data, colonization patterns, and immunoassays were analyzed to elucidate the dynamics of carriage and the role of M. catarrhalis in the clinical course of COPD. METHOD...

Standard methods do not reliably distinguish H. haemolyticus from H. influenzae. H. haemolyticus is a respiratory tract commensal. The recognition that some strains of apparent H. influenzae are H. haemolyticus substantially strengthens the association of true H. influenzae with clinical infection.

Nontypeable Haemophilus influenzae colonizes the respiratory tract of adults with chronic obstructive pulmonary disease (COPD) and causes intermittent exacerbations. Isolates of H. influenzae collected monthly in a prospective study were subjected to molecular typing. During a 7-year study spanning 345 patient-months of observation, 122 episodes of negative cultures lasting 1 month or more, and that were preceded and followed by isolation of an apparently identical strain of H. influenzae, were found. Seventeen such episodes of negative cultures, lasting 6 months or more and spanning 203 patient-months, were studied in detail to test the hypothesis that these periods of negative cultures represented continuous colonization by the same strain of H. influenzae. Molecular typing by three independent methods established that the strains preceding and following the episodes of negative cultures were indeed identical. Strain-specific H. influenzae DNA was detected in some of the sputum samples that had yielded negative cultures. These results indicate that some patients with COPD are persistently colonized with H. influenzae and that sputum cultures underestimate the frequency of colonization of the respiratory tract by H. influenzae in COPD. This observation has a significant impact on understanding bacterial colonization in COPD.

Two distinct patterns of carriage by P. aeruginosa were observed: (1) short-term colonization followed by clearance and (2) long-term persistence. Mucoid strains showed persistence. Acquisition of P. aeruginosa is associated with the occurrence of an exacerbation. Serum antibody responses do not mediate clearance of P. aeruginosa.

Intraclonal microevolution and the frequent turnover or loss of clones are typical for infections with P. aeruginosa in COPD. This epidemiological signature differs from that of the chronic carriage of the same P. aeruginosa clone in patients with cystic fibrosis.

BackgroundNontypeable Haemophilus influenzae colonizes and infects the airways of adults with chronic obstructive pulmonary disease, the fourth most common cause of death worldwide.Thus, H. influenzae, an exclusively human pathogen, has adapted to survive in the hostile environment of the human airways.To characterize proteins expressed by H. influenzae in the airways, a prototype strain was grown in pooled human sputum to simulate conditions in the human respiratory tract.The proteins from whole bacterial cell lysates were solubilized with a strong buffer and then quantitatively cleaned with an optimized precipitation/on-pellet enzymatic digestion procedure.Proteomic profiling was accomplished by Nano-flow liquid chromatography/mass spectroscopy with low void volume and high separation efficiency with a shallow, long gradient.ResultsA total of 1402 proteins were identified with high confidence, including 170 proteins that were encoded by genes that are annotated as conserved hypothetical proteins.Thirty-one proteins were present in greater abundance in sputum-grown conditions at a ratio of > 1.5 compared to chemically defined media.These included 8 anti-oxidant and 5 stress-related proteins, suggesting that expression of antioxidant activity and stress responses is important for survival in the airways.Four proteins involved in uptake of divalent anions and 9 proteins that function in uptake of various molecules were present in greater abundance in sputum-grown conditions.ConclusionsProteomic expression profiling of H. influenzae grown in pooled human sputum revealed increased expression of antioxidant, stress-response proteins and cofactor and nutrient uptake systems compared to media grown cells.These observations suggest that H. influenzae adapts to the oxidative and nutritionally limited conditions of the airways in adults with chronic obstructive pulmonary disease by increasing expression of molecules necessary for survival in these conditions.

To characterize the immune response to Moraxella catarrhalis after exacerbations of chronic obstructive pulmonary disease (COPD), pre- and postexacerbation serum and sputum supernatant samples obtained during 21 exacerbations in 18 patients were studied, using the homologous infecting isolates. New serum immunoglobulin G (IgG) detected by whole-cell enzyme-linked immunosorbent assay developed after 12 (57.1%) of 21 exacerbations. Analysis of serum samples with flow cytometry, which detects antibodies that are exclusive to epitopes on the bacterial surface, revealed that 5 (23.8%) of the 21 exacerbations were associated with the development of new serum IgG to surface epitopes. Three of these serum samples and 2 other serum samples contained new IgG directed at lipooligosaccharide. Flow cytometry revealed that new mucosal IgA to surface-exposed epitopes of the infecting isolate developed in sputum supernatants after 42% of exacerbations. Therefore, adults with COPD develop variable humoral immune responses to M. catarrhalis after exacerbations, including new serum IgG and new mucosal IgA to epitopes on the bacterial surface.

Indwelling urinary catheters are common in health care settings and can lead to catheter-associated urinary tract infection (CAUTI). Long-term catheterization causes polymicrobial colonization of the catheter and urine, for which the clinical significance is poorly understood. Through prospective assessment of catheter urine colonization, we identified Enterococcus faecalis and Proteus mirabilis as the most prevalent and persistent co-colonizers. Clinical isolates of both species successfully co-colonized in a murine model of CAUTI, and they were observed to co-localize on catheter biofilms during infection. We further demonstrate that P. mirabilis preferentially adheres to E. faecalis during biofilm formation, and that contact-dependent interactions between E. faecalis and P. mirabilis facilitate establishment of a robust biofilm architecture that enhances antimicrobial resistance for both species. E. faecalis may therefore act as a pioneer species on urinary catheters, establishing an ideal surface for persistent colonization by more traditional pathogens such as P. mirabilis.