Bugs Causing Pneumonia BugNeon.<4 wksKids<18 yrsAdults18-40Adults40-65ElderlyNosoc.ICEtOH/IVDACFPost-viralAtypicalS. aureusXXXXS. pneumoniaeXXXXX XGroup B strepXE. coliXK. pneumoniaeXSerratiaXP. aeruginosaXH. influenzaeXXXL. pneumophilaXChlamydophilaXXXM. pneumoniaeXXXXCMVXRSVXParainfluenzaXXH. capsulatumC. immitisP. brasiliensisC. neoformansP. jiroveciX Most common causes typical S. pneumoniae causes 50-75% of community-acquired pneumonia! atypical Mycoplasma pneumoniae Chlamydia pneumoniae Legionella pneumophila Additonal rules of thumb older adults and elderly anaerobic bacteria viruses Gram-negative rods nosocomial enteric Gram-negative rods immunocompromised enteric Gram-negative rods fungi viruses aspiration pneumonia normal mixed oral flora anaerobes Standard treatment cephalosporin cover Gram-positives macrolide cover atypical causes Bronchitis acute bronchitis is almost always due to a virus Abbreviations Neon. = neonates Nosoc. = nosocomial infections EtOH/IVDA = alcoholics/intravenous drug abusers CF = cystic fibroris IC = immunocompromised