Do bacteria cause exacerbations of COPD?

Exacerbations of COPD, which include combinations of dyspnea, cough, wheezi ng, increased sputmn production (and a change in its color to green or yell ow), are common. The role of bacterial infection in causing these episodes and the value of antibiotic therapy for them are debated. An assessment of the microbiological studies indicates that conventional bacterial respirato ry pathogens, such as Streptococcus pneumoniae and Haemophilus influenzae, are absent in about 50% of attacks. The frequency of isolating these organi sms, which often colonize the bronchi of patients in stable condition, does not seem to increase during exacerbations, and their density typically rem ains unchanged. Serologic studies generally fail to show rises in antibody titers to H influenzae; the only report available demonstrates none to Haem ophilus parainfluenzae; and the sole investigation of S pneumoniae is incon clusive. Trial with vaccines against S pneumoniae and H influenzae show no dear benefit in reducing exacerbations. The histologic findings of bronchia l biopsies and cytologic studies of sputum show predominantly increased cos inophils, rather than neutrophils, contrary to what is expected with bacter ial infections, The randomized, placebo-controlled trials generally show no benefit for antibiotics, but most have studied few patients, A meta-analys is of these demonstrated no clinically significant advantage to antimicrobi al therapy. The largest trials suggest that antibiotics confer no advantage for mild episodes; with more severe attacks, in which patients should rece ive systemic corticosteroids, the addition of antimicrobial therapy is prob ably not helpful.