Table 1.
Isolate sources and MICs.
Fig 1.
Assay performance with ciprofloxacin.
Relative growth values for 35 S. aureus strains derived from the MBT-ASTRA assay performed with ciprofloxacin are shown. A relative growth cutoff of 0.5 was utilized to classify resistance, indicated by the horizontal line. Strains are arranged from left to right in order of increasing MIC, with exact values given in Table 1. Data points colored red indicate major or very major errors. For each strain, 4–6 independent replicates were obtained on different days.
Fig 2.
Assay performance with oxacillin.
Relative growth values from the MBT-ASTRA assay performed with oxacillin are shown. A relative growth cutoff of 0.5 was utilized to classify resistance, indicated by the horizontal line. Strains are arranged from left to right in order of increasing MIC, with exact values given in Table 1. Data points colored red indicate major or very major errors. For each strain, 4–6 independent replicates were obtained on different days.
Fig 3.
Assay performance with cefepime.
Relative growth values from the MBT-ASTRA assay performed with cefepime are shown. A relative growth cutoff of 0.5 was utilized to classify resistance, indicated by the horizontal line. Intermediate resistance is abbreviated as Int. Strains are arranged from left to right in order of increasing MIC, with exact values given in Table 1. Data points colored red indicate major or very major errors. For each strain, 4–5 independent replicates were obtained on different days.
Fig 4.
Assay performance with vancomycin.
Relative growth values from the MBT-ASTRA assay performed with vancomycin for the 35 S. aureus strains in the original panel (a) and an additional 14 VISA isolates (b) are shown. A relative growth cutoff of 0.5 was utilized to classify resistance, indicated by the horizontal line. Intermediate resistance is abbreviated as Int and full resistance as Res. Strains are arranged from left to right in order of increasing MIC in panel (a), with exact values given in Table 1. Data points colored red indicate major errors. For each strain, 4 independent replicates were obtained on different days.
Fig 5.
Assay reproducibility from 40 replicates with strains susceptible and resistant to each antibiotic. Relative growth values from each replicate are shown, with data points representing major and very major errors colored red. A relative growth cutoff of 0.5 was utilized to classify resistance, indicated by the horizontal line. Intermediate resistance is abbreviated as Int. For each strain, 40 replicates were obtained over at least 4 days with up to 12 replicates from a single starter culture.
Table 2.
Summary of MBT-ASTRA assay performance across 35 strains.
Fig 6.
Assay performance on blood culture.
MBT-ASTRA assay performed from spiked blood culture. Relative growth values from each replicate are shown, with data points representing major errors colored red. Strain FDAARGOS_159 represented by (●), strain ATCC 25923 represented by (■), strain BAA-44 represented by (▲), strain BR-VRSA represented by (♦). Filled symbols indicate the strain is susceptible to the antibiotic by reference standard while open symbols indicate resistance. A relative growth cutoff of 0.5 was utilized to classify resistance, indicated by the horizontal line. For each strain, 3 independent replicates were obtained on different days, with the mean and standard deviation shown for each set.