Pneumonia, MycoplasmaMycoplasma pneumoniaePneumoniaPneumonia, BacterialLegionellosisPsittacosisQ FeverSARS VirusSevere Acute Respiratory SyndromeCommunity-Acquired InfectionsPneumonia, ViralPneumonia, PneumococcalCryptogenic Organizing PneumoniaPneumonia, PneumocystisPneumonia, StaphylococcalPneumonia, Ventilator-AssociatedPneumonia, AspirationPneumonia, LipidLung Diseases, InterstitialLungIdiopathic Interstitial PneumoniasStreptococcus pneumoniaeAnti-Bacterial AgentsMurine pneumonia virusPneumocystis jiroveciiPneumocystisLegionnaires' DiseaseBronchoalveolar Lavage FluidRadiography, ThoracicCross InfectionPulmonary EosinophiliaTrimethoprim-Sulfamethoxazole CombinationBronchopneumoniaHospitalizationPneumonia, Progressive Interstitial, of SheepVentilators, MechanicalBronchoalveolar LavageRespiration, ArtificialIntensive Care UnitsRetrospective StudiesProspective Studies