How to know what is atypical pneumonia and what are the requested tests?

Mycoplasma & others. Atypical pneumonia generally refers to infection by organisms such as mycoplasma pneumoniae, chlamydophila or legionella. The reason why it is considered "atypical" is due to lack of typical symptoms of bacterial pneumonias (fever with chills, cough with sputum production etc.). Testing may involve chest x-rays, cultures and blood tests to figure out the causative organism for the pneumonia.