Which antibiotic is used in the Optochin disk test to differentiate S. pneumoniae?

Which antibiotic is used in the Optochin disk test to differentiate S. pneumoniae?

• A. 2 μg/mL
• B. 5 μg/mL
• C. 10 μg/mL
• D. 20 μg/mL

Answer: (B)

The Optochin disk test is a specific laboratory test used to identify Streptococcus pneumoniae, a significant pathogen responsible for various infections, including pneumonia and meningitis. In this test, a disk containing optochin is placed on an agar plate that has been inoculated with the bacteria in question. The reason why a 5 μg/mL concentration of optochin is used is that this particular dosage has been established as effective for differentiating S. pneumoniae from other alpha-hemolytic streptococci. S. pneumoniae is uniquely sensitive to optochin, which means that when exposed to the antibiotic, it will show a zone of inhibition (clear area around the disk) indicating susceptibility. Other streptococci, such as Streptococcus mitis and Streptococcus sanguinis, typically do not exhibit this sensitivity at the same concentration. Using a higher or lower concentration could yield ambiguous results; thus, the 5 μg/mL concentration has been standardized in clinical microbiology as a reliable method for differentiation. This specificity for S. pneumoniae is crucial for accurate diagnosis and treatment of infections caused by this organism.

The Optochin disk test is a specific laboratory test used to identify Streptococcus pneumoniae, a significant pathogen responsible for various infections, including pneumonia and meningitis. In this test, a disk containing optochin is placed on an agar plate that has been inoculated with the bacteria in question.

The reason why a 5 μg/mL concentration of optochin is used is that this particular dosage has been established as effective for differentiating S. pneumoniae from other alpha-hemolytic streptococci. S. pneumoniae is uniquely sensitive to optochin, which means that when exposed to the antibiotic, it will show a zone of inhibition (clear area around the disk) indicating susceptibility. Other streptococci, such as Streptococcus mitis and Streptococcus sanguinis, typically do not exhibit this sensitivity at the same concentration.

Using a higher or lower concentration could yield ambiguous results; thus, the 5 μg/mL concentration has been standardized in clinical microbiology as a reliable method for differentiation. This specificity for S. pneumoniae is crucial for accurate diagnosis and treatment of infections caused by this organism.