Bacterial pneumonia is commonly caused by bacteria strains such as Streptococcus pneumoniae, Chlamydophila pneumonia or Legionella pneumophila. It affects people of all ages, leading to a weakened ability of the body to exchange oxygen and carbon dioxide, breathlessness and pain when breathing. Bacterial pneumonia cases can be mild or severe, depending on the strength of the bacteria strain and how long until the disease is diagnosed and treated.