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.