Penicillin-resistant pneumococci.

Area of Science:

• Clinical microbiology
• Antimicrobial resistance

Background:

• Increasing reports of penicillin-resistant Streptococcus pneumoniae necessitate reliable detection methods.
• Accurate identification of resistant strains is crucial for effective patient treatment and infection control.

Purpose of the Study:

• To evaluate the accuracy of different Kirby-Bauer disk diffusion methods for identifying pneumococci clinically resistant to penicillin.
• To determine which disk provides acceptable predictive accuracy for penicillin resistance in pneumococci.

Main Methods:

• The Microbiology Resource Committee of the College of American Pathologists assessed various Kirby-Bauer disks.
• The study focused on identifying pneumococcal isolates known to be clinically resistant to penicillin.

Main Results:

• Only the 1-microgram oxacillin disk demonstrated acceptable performance.
• An inhibition zone diameter of 19 mm or less on the oxacillin disk was the criterion for predicting clinical penicillin resistance.
• Penicillin disks showed unacceptable predictive accuracy.

Conclusions:

• The 1-microgram oxacillin disk is a reliable method for predicting clinical penicillin resistance in pneumococci.
• Current penicillin disk diffusion tests are not recommended for accurately identifying penicillin-resistant pneumococci.