<prompt> Most common organism to cause OPSIStreptococcal pneumoniaH. influenzaMycobacterium TBBabesia  <response>: Ans a Streptococcal pneumoniaRef Sabiston page 156820th edition 50-90 cases of OPSI is due to streptococcal pneumonia. PPV23 vaccine is given nowadays 2 weeks prior to elective surgery 