The American Thoracic Society (ATS) and the Infectious Disease Society of America (IDSA) agree that the empiric therapy of mild community acquired pneumonia (CAP) should include coverage for the atypical pathogens.These are Mycoplasma,Chlamydia and Legionella.
In Europe, although ID physicians agree that about 40% of CAP is due to the atypicals,that beta-lactam antibiotics alone should be used anyway even though they have no activity against the atypicals. They argue that these pathogens (except for Legionella)usually cause mild, self-limiting illnesses and that adding broader coverage medications will exacerbate the public health problem of increasing antibiotics resistance.In the U.S, typically, a macrolide would be included in the treatment of CAP.
ID docs in the U.S. argue that the illnesses are shortened by broader coverage and there is also data showing a decreased mortality in hospitalized patients with CAP.One could argue that if hospitalization is needed that the CAP is more than mild.
The European approach seems to place a theoretical concern above individual patient concerns.Further a chest x ray is apparently not required to diagnose pneumonia so it can be argued they over treat viral bronchitis and add to the growing resistance problem. It is hard to argue against the view that more antibiotic use may lead to more pathogen resistance but you have to wonder how much effect under treating CAP would have to mitigate that trend.