Association between airway bacterial load and markers of airway inflammation in patients with stable chronic bronchitis

Infection as a comorbidity of COPD

“…However, Enterobacteriaceae, P. aeruginosa and Staphylococcus aureus have been implicated in COPD exacerbations and were not systematically examined in this study; therefore, bacterial load changes could be a mechanism of exacerbations for these pathogens. Bacterial load is also an important determinant of airway inflammation, with increasing concentrations associated with greater intensity of neutrophilic airway inflammation [19,20].…”

The Importance of Chronic Bronchitis in Chronic Obstructive Pulmonary Disease

“…Modified from (29) and (30). Although standard definitions of chronic bronchitis only include chronic sputum expectoration, early descriptive series of patients found that 70% of patients had bronchospasm, 88% had either sporadic or constant breathlessness and "spells of sickness for several weeks or a few months" with infection thought to be causal in all cases (31).…”

“…Cigarette smoke exposure is known to effect lower airway mucociliary clearance by reducing ciliary beat frequency (131) and the neutrophilic inflammation present in chronic bronchitis has been shown to be conducive to bacterial colonisation (132). Colonisation is associated with increased sputum concentrations of inflammatory mediators including IL-8, LTB4 as well as neutrophil elastase (30). Lower airway bacterial colonisation in the stable state appears to increase the frequency and alter the character of COPD exacerbations (with patients with Chronic Bronchitis experiencing more exacerbations) (133).…”

“…The numbers of bacteria present may also alter immune cellular responses which could impact on subsequent inflammation, as patients with sputum bacterial loads of > 10 6 cfu/ml have been shown to have a more robust inflammatory response than those with bacterial loads that are lower (30). In animal models, bacterial loads of less than 10 5 organisms can be eradicated by macrophages and other components of the innate host defence without inducing much inflammation.…”

“…However, these trials have often been limited in their design, as they have not differentiated between bacterial exacerbations (where one would expect an improvement in clinical outcomes following appropriate treatment) and non-bacterial exacerbations (where antibiotics should not effect outcomes). Antibiotics are an appropriate therapy for suspected bacterial exacerbations, and should be reserved for patients with symptoms and signs consistent with infection, in the presence of purulent sputum (30,147). Given the bacteria isolated from sputum during exacerbations (see earlier), an appropriate choice of antibiotic includes broad spectrum penicillins such as amoxicillin (155), tetracyclines such as doxycyline (156) and quinolones and macrolides where allergies and bacterial resistance are important determinants of anti-bacterial choice .…”