<prompt> The majority of cases of community acquired pneumomia are due to infection with-Legionella pneumophilaStreptococcus pneumoniaeHaemophilus influenzaeStaphylococcus aureus  <response>: The most common infective agent of community acquired pneumonia is Streptococcus pneumoniae.Most cases are spread by droplet infection.Viral infections are impoant causes of CAP in children. Reference:Davidsons Medicine-22nd edition,page no:682 