1989 Volume 14 Issue 2 Pages 107-116
We evaluated optochin sensitivity test as a method for identification of Streptococcus pneumoniae. Four hundred thirty-three strains isolated from various clinical specimens were α-hemolytic, gram-positive streptococci and were sensitive to optochin disk The screening of optochin (5μg/ml) was performed on bile soluble strains which were identified as S. pneumoniae. Then, minimum inhibitory concentration (MIC) to optochin determind for optochin-resistant S. pneumoniae. The susceptibility test on isolated S. pneumoniae was performed 31 antimicrobial agents. Out of 433 optochin disk (5μg) sensitive strains, 398 strains were bile soluble and 35 strains were nonsoluble. These 35 strains were identified as 2 of S. sanguis Ⅰ , 1 of S. mutans, 2 of S. salivarius, 28 of S. mitis and 2 of S. anginosus by the Minitek system. While bile soluble 398 strains consisted of 311 optochin-sensitive strains and 67 optochin-resistant strains. MIC of optochin for the 67 strains ranged from 6.25 to 200 over μg/ml, and was MIC≧50μg/ml for 38 of these 67 strains. In identification of S. pneumoniae, bile solubility test shoud be used with optochin test. In the colonies of optochin-resistant S. pneumoniae, smooth and rough type colonies occupied the major portion but mucoid type colony was rare. All strains were highly susceptible to penicillins and cephems, but MIC of macrolides, lincomycins and tetracy-clines ranged widely (0.0063-200μg/ml) and a large number of strains were resistant to these antimicrobial agents. In addtion, optochin-resistant S. pneumoniae showed higher MIC than optochin-sensitive S. pneumoniae in susceptibility test of S. pneumoniae to 31 antimicrobial agents.
