Atypical bacteria (primarily Chlamydia and Mycoplasma) have been implicated in less than 10% of COPD exacerbations, although 1 study conducted in Turkey found that it was the sole causal agent in 16% of exacerbations and 1 of several causal agents in 6% of cases. In the most severe cases, Gram-positive or Gram-negative bacteria were also present. The presence of Gram-negative bacteria should be suspected in patients:

  • with stage III disease
  • who experience at least 3 or 4 infections per year
  • with concurrent bronchiectasis (swollen, thickened, dilated bronchial tubes that are diagnosed with a CT scan)

Many exacerbations of COPD may not be precipitated by infection alone, and in those infectious exacerbations, frequently more than 1 organism may be the cause. As a result, treatment for infectious exacerbations is usually broad-spectrum.