title: Why do sputum cultures fail to yield pathogens?
mesh_terms: D001431:Bacteriological Techniques; D002245:Carbon Dioxide; D006193:Haemophilus influenzae / Q000302:isolation & purification*; D006801:Humans; D008722:Methods; D013183:Sputum / Q000382:microbiology*; D013296:Streptococcus pneumoniae / Q000302:isolation & purification*
chemical_list: D002245:Carbon Dioxide