TABLE 5.

Laboratory detection of hVISA and accuracy of methods compared to those of modified population analysis/area under the curvea

MethodSensitivitySpecificityReference(s)
Vancomycin broth MICb11%100%372
BHIA + vancomycin at 6 μg per ml, 10 μl of a 0.5-McFarland-standard suspension (BHIA6V)c48 h, 4.5-12%48 h, 68-100%370, 389, 393
MHA + teicoplanin at 5 μg per ml, 10 μl of a 2-McFarland-standard suspension (MHA5T)d48 h, 65-79%48 h, 35-95%82, 252, 370, 389, 393
MHA + teicoplanin at 5 μg per ml, 10 μl of a 2-McFarland-standard suspensione48 h, 98%48 h, 53%82
MHA + vancomycin at 5 μg per ml, 10 μl of a 0.5-McFarland-standard suspension48 h, 1-20%48 h, 59-99%370, 372
Simplified PAPf48 h, 71%48 h, 88%372
Macromethod Etest (MET)48 h, 69-98.5%48 h, 89-94%174, 289, 370, 372, 389
Etest GRD24 h, 70-77%24 h, 98-100%174, 393
48 h, 93-94%48 h, 82-95%
  • a In all studies, vancomycin population analysis/area under the curve (PAP/AUC) was considered the “gold standard” for calculating sensitivity and specificity.

  • b Evaluation of vancomycin broth MICs included detection of VISA and hVISA. By definition, hVISA will not be detected by determinations of broth MIC.

  • c BHIA6V is the screening plate recommended by the CDC and the Clinical and Laboratory Standards Institute for the detection of VRSA and VISA strains with vancomycin MICs of ≥8 μg per ml (http://www.cdc.gov) (53), which is spot inoculated with 10 μl from a 0.5-McFarland-standard suspension and read at 24 and 48 h. The culture is considered positive if there is growth of 2 or more colonies.

  • d MHA5T is the screening plate recommended by the Comité de l'Antibiogramme de la Société Française de Microbiologie (http://www.sfm.asso.fr),which is spot inoculated with 10 μl from a 2-McFarland-standard suspension and read at 24 and 48 h. The culture is considered positive if there is growth of 1 or more colonies.

  • e This analysis included some isolates with a hetero-teicoplanin-resistant but vancomycin-susceptible phenotype by population analysis.

  • f Simplified PAP consists of inoculating BHIA with 4 μg per ml of vancomycin with 10 μl from a 0.5-McFarland-standard suspension and reading at 24 and 48 h for any growth.