system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Most common causative organism for lobar pneumonia is -
assistant
The correct answer is  Streptococcus pneumoniae is the Most common causative organism for lobar pneumonia
Adult: MC serotype associated: Type 1-8
Children: Type 6, 14, 19, 23 are frequently associated serotypes
Most Virulent: Type 3.

Ref: Apurba Sastry’s Essentials of Medical Microbiology 1/e p233 , Ananthanarayan 9/e p222