TABLE 2.

Sensitivities and limits of detection for the two assays tested on pure strains and their defined mixtures at various concentrations

Sample group (no. of samples)AssayLoD range (CFU/ml)Avg LoD (95% CI)Sensitivity (%) at indicated MRSA concn (no. of positive samples)
CFU/mlCFU/swaba102 CFU/ml103 CFU/ml104 CFU/ml
MRSA strains (27)GeneOhm1.4 × 102-4.1 × 1044.3 × 103 (1.7 × 102-3.2 × 104)4.3 × 102 (1.7 × 101-3.2 × 103)33.30 (9)92.30 (25)100 (27)
Xpert1.4 × 102-2.0 × 1043.3 × 103 (1.6 × 102-1.1 × 104)2.5 × 102 (1.2 × 101-8.4 × 102)14.80 (4)96.30 (26)100 (27)
MRSA/non-MRSA mixtures (21)GeneOhm5.4 × 100-5.1 × 1032.0 × 103 (4.5 × 101-4.9 × 103)2.0 × 102 (4.5 × 100-4.9 × 102)42.90 (9)100 (21)NDb
Xpert2.7 × 101-5.1 × 1032.4 × 103 (3.7 × 101-5.0 × 103)1.8 × 102 (2.7 × 100-3.7 × 102)38.10 (8)100 (21)ND
  • a Calculated for 100-μl and 75-μl sample inputs for GeneOhm and Xpert, respectively.

  • b ND, not determined, as all MRSA-positive mixtures were detectable at the preceding lower concentration.