Evaluation of commercial methods for determining antimicrobial susceptibility of Streptococcus pneumoniae.
Seven commercial systems for antimicrobial susceptibility testing of Streptococcus pneumoniae were evaluated by using a challenge set of 55 pneumococcal isolates with a variety of resistance phenotypes and genotypes. Overall, the results produced by the Pasco and Etest methods were found to be acceptable for all drugs tested except for trimethoprim-sulfamethoxazole testing by the Etest. The Just One system for penicillin MIC testing was also judged to be acceptable (minor error rate, 5.5%). Although the Sensititre and MicroTech methods both produced 12.7% minor errors with penicillin, the Sensititre method classified penicillin-intermediate strains as resistant or vice versa, while four of MicroTech's errors were among intermediate strains that were classified as susceptible. The MicroMedia (minor error rate, 16.4%) and MicroScan Rapid (minor error rate, 63.6%) methods produced unacceptably high levels of errors when testing penicillin. Minor error rates for cefotaxime and ceftriaxone ranged from a low of 12.7% (Etest and Sensititre) to a high of 28% (MicroMedia). Error rates were low for erythromycin, tetracycline, and chloramphenicol by most methods with the exception of the MicroScan method, which had a high very major error rate for erythromycin (34.6%). For testing of beta-lactam drugs, the Pasco, Etest, and Just One tests for penicillin are the most accurate methods; the Sensititre method also provided acceptable results.
Tenover
F C
FC
Hospital Infections Program, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.
Baker
C N
CN
Swenson
J M
JM
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002439:Cefotaxime / Q000494:pharmacology; D002443:Ceftriaxone / Q000494:pharmacology; D002511:Cephalosporins / Q000494:pharmacology; D002702:Chloramphenicol Resistance; D004352:Drug Resistance, Microbial; D004917:Erythromycin / Q000494:pharmacology; D005069:Evaluation Studies as Topic; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods* / Q000706:statistics & numerical data; D010403:Penicillin Resistance; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000302:isolation & purification; D013753:Tetracycline Resistance; D014296:Trimethoprim Resistance; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D004917:Erythromycin; D002443:Ceftriaxone; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D002439:Cefotaxime