Community-acquired pneumonia pneumonia not seen on x-rays. However, congestive heart failure or other types of lung damage can mimic CAP on x-rays. Several tests can identify the cause of CAP. Blood cultures can isolate bacteria or fungi in the bloodstream. Sputum Gram staining and culture can also reveal the causative microorganism. In severe cases, bronchoscopy can collect fluid for culture. Special tests can be performed if an uncommon microorganism is suspected, such as urinalysis for Legionella antigen in Legionnaires' disease. CAP is treated with an antibiotic that kills the offending microorganism and by managing complications. If the causative microorganism is unidentified (often
Pneumocystis pneumonia rare cause of pneumonia in neonates. It is commonly believed to be a commensal organism (dependent upon its human host for survival). The possibility of person-to-person transmission has recently gained credence, with supporting evidence coming from many different genotyping studies of "P. jirovecii" isolates from human lung tissue. For example, in one outbreak of 12 cases among transplant patients in Leiden, it was suggested as likely, but not proven, that human-to-human spread may have occurred. Since the start of the AIDS epidemic, PCP has been closely associated with AIDS. Because it only occurs in an immunocompromised host, it may be