Optochin resistance in Streptococcus pneumoniae strains isolated from blood and middle ear fluid.

Optochin resistant Streptococcus pneumoniae having typical pneumococcal morphology in culture and Gram stain and giving clear agglutination with anti-pneumococcal polysaccharide antisera were isolated from primary cultures of blood and middle ear fluid. The isolated pneumococci were either fully sensitive to penicillin and other antimicrobial agents commonly used or relatively resistant to penicillin and resistant to cloxacillin, tetracycline, erythromycin, sulphatrimethoprim and clindamycin.