Collaborative Evaluation of an Erythromycin-Clindamycin Combination Well for Detection of Inducible Clindamycin Resistance in Beta-Hemolytic Streptococci by Use of the CLSI Broth Microdilution Method

摘要: Constitutive or inducible clindamycin resistance can occur in beta-hemolytic streptococci due to the presence of an erm gene. The Clinical and Laboratory Standards Institute (CLSI) has recommended a disk approximation test (D-zone test) with erythromycin disks single-well broth combining for detection staphylococci, but only streptococci. This collaborative study assessed two different concentration combinations single wells (1 μg/ml + 0.25 [erythromycin plus clindamycin] 1 0.5 μg/ml) three brands Mueller-Hinton supplemented 3% lysed horse blood testing frozen panels prepared this study. All labs performed D-zone as described by CLSI. A total 155 nonduplicate streptococcal isolates (50 group A, 48 B, 28 C, 29 G isolates) were tested; 99 showed test. There some differences noted based upon medium. sensitivity combination was 91 100%, while 95 100%. Specificity overall 98%. slightly higher is recommended. demonstrated that microdilution incorporating sensitive specific indicator could be included routine panels.