In a patient of orbital cellulitis, micro organism on culture show greenish colonies and optochin sensitivity. The most likely organism is :
“Pneumococci is optochin sensitive and forms green colonies on blood agar due to Α hemolysis.”
Characteristic features of Pneumococci :

Bile soluble, optochin sensitive
Inulin fermenter
Capsulated, shows quellung reaction
Colonies show central umbonation, appear as draughtsmann or carrom coin
MC causative agent of lobar Pneumonia, Adult meningitis, otitis media, sinusitis (orbital cellulitis is complication of sinusitis).
Strep. viridans
Staphylococcus
Pseudomonas
Pneumococcus