H. influenza and S. pneumonia are organisms which are usually responsible for community-acquired pneumoniA. S. aureus and Pseudomonas spp. are usually found in patients with hospital-acquired pneumoniA. L. pneumophilia, along with Chlamydia spp. and Mycoplasma pneumonia, are the atypical pneumonia-causing organisms. A urinary antigen test is routinely used for the detection of Legionella spp. Serological tests can be used for the detection of Mycoplasma and Chlamydia spp. and also Legionella spp.