<prompt> Most common causative organism for lobar pneumonia is:Staphylococcus aureusStreptococcus pyogenesStreptococcus pneumoniaeHaemophilus influenzae  <response>: Ans. is c i.e., Streptococcus pneumoniae Most common cause of lobar pneumonia: Pneumococcus. Most common cause of acute sinusitis: Pneumococcus. Most common cause of adult meningitis: Pneumococcus. Most common cause of atypical pneumonia: Mycoplasma pneumoniae. Most common infection of pneumococcus: Otitis media. 