title: Detection of penicillin-resistant Streptococcus pneumoniae with commercially available broth microdilution panels.
abstract: We compared penicillin MICs obtained with three different commercially available broth microdilution panels (MicroScan, Sensititre, and Pasco) with MICs obtained with reference microdilution panels for 20 well-characterized pneumococci with decreased susceptibilities to penicillin (7 resistant and 13 intermediate). All panels were supplemented with 2 to 5% lysed horse blood (LHB) prepared in-house. Additional supplements included fastidious inoculum broth (FIB) for MicroScan panels and commercially prepared LHB (Difco) for Pasco panels. The percentages of penicillin-resistant strains (MIC 2 micrograms/ml) detected by the different methods follow: MicroScan-FIB, 0; MicroScan-LHB 0; Pasco in-house LHB, 71; and Sensititre-LHB, 100. The percentages of intermediate strains (MIC = 0.1 to 1.0 micrograms/ml) detected by the different methods follow: MicroScan-FIB, 31; MicroScan-LHB 23; Pasco in-house LHB, 46; and Sensititre-LHB, 85. Difco LHB supplement failed to support the growth of 86% of the strains in the Pasco panels. Of the commercially available panels evaluated, only Sensititre, supplemented with LHB prepared in-house could reliably detect penicillin-resistant pneumococci.
authors.affiliation: Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: F S
authors.initials: FS
authors.lastname: Nolte
authors.forename: B
authors.initials: B
authors.lastname: Metchock
authors.forename: T
authors.initials: T
authors.lastname: Williams
authors.forename: L
authors.initials: L
authors.lastname: Diem
authors.forename: A
authors.initials: A
authors.lastname: Bressler
authors.forename: F C
authors.initials: FC
authors.lastname: Tenover
mesh_terms: D003470:Culture Media; D005069:Evaluation Studies as Topic; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods* / Q000592:standards; D010403:Penicillin Resistance; D011786:Quality Control; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000302:isolation & purification*
chemical_list: D003470:Culture Media