<prompt> In a patient of orbital cellulitis, microorganism on culture show greenish colonies and optochin sensitivity. The most likely organism is:Strep, viridansStaphylococcusPseudomonasPneumococcus  <response>: Ans. is d i.e., PneumococcusGram-positive cocci which form a-hemolytic colonies Greenish colonies and is optochin sensitive is pneumococcus.The characteristic features of pneumococcus are: BIO Memory Aida Bile solubility.b Optochin sensitivity.c Inulin fermentation.d Shows quellung reaction capsular delineation.e Forms draughtsman or carrom coin colonies Colonies with central umbonation. 