Table 2.
Discrepancies Between Rapid Multiplex Polymerase Chain Reaction Assay and Standard Culture/Phenotypic Antimicrobial Susceptibility Testing
| Rapid Multiplex PCR Panel Result | Standard Culture and Phenotypic Susceptibility Testing | No. |
|---|---|---|
| Single/few organisms detected | Multiple organisms detected | 6 |
| 1. Klebsiella pneumoniae | 1. K. pneumoniae, Staphylococcus epidermidis | |
| 2. Enterococcus species | 2. Enterococcus faecium, Staphylococcus hemolyticus, Micrococcus luteus | |
| 3. Enterobacter cloacae, Enterococcus species (vanA/B positive) | 3. Enterococcus faecalis (vancomycin susceptible), E. faecium (vancomycin resistant), E. cloacae, Streptococcus mitis, S. epidermidis, Acinetobacter species | |
| 4. (bottle a) Streptococcus agalactiae (bottle b) Escherichia colia |
4. (bottle a) S. agalactiae, E. coli (bottle b) E. coli, Proteus species |
|
| 5. Streptococcus species, Haemophilus influenzae | 5. Haemophilus sputorum, Neisseria subflava, Streptococcus salivarius, Streptococcus viridans group, Streptococcus mitis | |
| 6. Enterococcus species (vanA/B negative) | 6. E. faecium (vancomycin susceptible), S. anginosus | |
| Discrepancy in susceptibility result | 4 | |
| 1. Enterococcus species (vanA/B negative) | 1. Enterococcus casseliflavus (vancomycin MIC, 8 µg/mL) | |
| 2. Enterococcus species (vanA/B positive) | 2. E. faecium, vancomycin MIC 2 µg/mL, isolate vanA positive by PCR | |
| 3. Staphylococcus species (mecA positive) | 3. Staphylococcus capitis, oxacillin MIC 0.25 µg/mL, isolate mecA negative by PCR | |
| 4. Staphylococcus species (mecA negative) | 4. Coagulase-negative Staphylococcus species, oxacillin 1 µg/mL, isolate mecA negative by PCR | |
| Discrepancy in organism identification | 3 | |
| 1. Enterococcus species and Staphylococcus species (mecA positive)b | 1. S. epidermidis | |
| 2. Negative | 2. Enterobacter species | |
| 3. K. pneumoniae | 3. Enterobacter aerogenes | |
Abbreviations: MIC, minimum inhibitory concentration; PCR, polymerase chain reaction.
a Gram stain results differed between 2 blood culture bottles collected on the same day for this subject. Both bottles were evaluated according to the study arm assignment of bottle a, which signaled positive first.
b Heavy growth of coagulase-negative staphylococci may lead to cross-reactivity with Enterococcus species; thus, the rapid multiplex PCR result was not reported.