Detection of vancomycin-intermediate Staphylococcus aureus with the updated Trek-Sensititre System and the MicroScan System. Comparison with results from the conventional Etest and CLSI standardized MIC methods.

Vancomycin-intermediate Staphylococcus aureus (VISA) organisms have minimum inhibitory concentrations (MICs) of 4 to 8 microg/mL and are often associated with vancomycin treatment failure. Detection of VISA has remained problematic. A comparison of 4 methods to detect VISA was done. Of the 20 VISA isolates, the Clinical and Laboratory Standards Institute (CLSI) broth microdilution method yielded susceptible end points of 2 microg/mL for 7, MicroScan (Siemens Healthcare Diagnostics, West Sacramento, CA) for 2, Trek Sensititre (Trek Diagnostic Systems, Cleveland, OH) for 1, and Etest (AB Biodisk North America, Piscataway, NJ) for none. Comparison with the CLSI method showed essential agreement for 95% or more for the Etest, MicroScan, and Trek methods; categorical agreement was as follows: Etest, 60%; MicroScan, 65%; and Trek, 60%. Reliance on a single automated method for determining vancomycin MICs could lead to misclassification of some VISA isolates as vancomycin susceptible. At least 2 methods, including the Etest, should be used when confirming VISA because of slight differences in results from different methods around the end points of 2 and 4 microg/mL .

Evaluation of a new-generation line-probe assay that detects 5' untranslated and core regions to genotype and subtype hepatitis C virus.

The VERSANT HCV Genotype 2.0 Assay (LiPA 2.0; Innogenetics, Ghent, Belgium; distributed by Siemens Medical Solutions Diagnostics, Tarrytown, NY) is a new-generation line-probe assay that simultaneously detects sequences in the 5' untranslated (5'UTR) and core regions to genotype and subtype hepatitis C virus (HCV). We tested 60 specimens of known genotype and subtype and 2 specimens with mixed infections with the LiPA 2.0 assay. After arbitration based on genotype and subtype determined by sequencing, there was concordance in 58 of 60 specimens (specificity, 96.7%). Computer-assisted typing yielded comparable results, but much more rapidly. Of 67 clinical specimens, 64 readily yielded genotype and subtype; 3 indeterminate specimens were typed by sequencing and were uncommon types not in the database. The newgeneration line-probe assay that detects the 5'UTR and core regions to genotype and subtype HCV is applicable to more than 95% of specimens. Interpretation is facilitated by computer-assisted analysis.