J Clin Pathol Qual Control.  1999 Dec;21(2):275-280.

Evaluation of Optochin Disk Test for the Presumptive Identification of Streptococcus pneumoniae

• Lee HG
• Hwang GY
• Jang IH
• Uh Y
• Yoon KJ

Abstract

BACKGROUND: To determine the optimal media and procedures of optochin test for presumptive identification of Streptococcus pneumoniae, we measured inhibition zones in various conditions.
METHODS
Each swab suspended with 0.5% MacFarland turbidity of 58 S. penumoniae and 11 alpha-hemolytic streptococci was inoculated into six kinds of media with difference in blood type (5% sheep blood vs. 5% human blood), media composition (Trypticase soy agar [TSA] vs. Mueller Hinton agar [MHA]), and media depth (3 mm vs. 4 mm). Additionally, a few colonies of tested organisms were streaked into TSA with 3 mm depth of media. After overnight incubation at 35degrees C in both of 5% CO2 and aerobic condition, inhibition zones were measured and a zone of > or =14 mm was interpreted as susceptible. Latex agglutination test was done by Slidex pneumo-kit to confirm S. pneumoniae.
RESULTS
Susceptibility rates of optochin test for S. pneumoniae were as follows. Human blood containing media : 100% with the exception of MHA; sheep blood containing media : MHA; 100%, others; ranged from 98.3% to 94.8%. Among the 11 alpha-hemolytic streptococci, no isolate was susceptible to optochin in sheep blood TSA (3 mm depth) with streaking method, while the susceptibility rate by the other methods ranged from 9.1% to 36.4%.
CONCLUSIONS
Sheep blood containing TSA with streaking method is the most efficient method for the primary presumptive identification of S. pneumoniae because of its low false positivity and high sensitivity.

MeSH Terms

Agar
Humans
Latex Fixation Tests
Pneumonia
Sheep
Streptococcus pneumoniae*
Streptococcus*
Agar