<prompt> The most common causative organism for lobar pneumonia is :Staphylococcus aureusStreptococcus pyogenesStreptococcus pheumoniaeHaemophilus influenzae  <response>: Answer is C Stretptococcus pneumonia: Streptococcus pneumonia or pneumococcus is the most common cause of community acquired acute pneumonia -Robbins 7th748 Lobar pneumonia refers to an acute bacterial infection that results in consolidation of a large poion of a lobe or an entire lobe. Streptococcus pneumonia produces a picture of lobar pneumonia. 