TABLE 2.
Validation of target specificity
| Target of molecular beacon | Bacterial straina
|
Total (252 strains) | |||||
|---|---|---|---|---|---|---|---|
| MRSA | MSSA | MR-CNS | MS-CNS | VRE | Otherb | ||
| BAC16S | 17/17 | 3/3 | 3/3 | 3/3 | 3/3 | 5/5 | 34 |
| SG16S | 109/109 | 36/36 | 10/10 | 20/20 | 0/5 | 0/29 | 209 |
| mecA | 109/109 | 0/36 | 10/10 | 0/20 | 0/5 | 0/29 | 209 |
| spa | 109/109 | 36/36 | 0/10 | 0/20 | 0/5 | 0/29 | 209 |
| vanA | 0/93 | 0/29 | 0/8 | 0/20 | 20/29c | 0/48 | 228 |
| lukF | 32/61d | 4/31d | 0/2 | 0/2 | 0/2 | 0/2 | 100 |
Number of strains positive for target/number of strains tested. Common nosocomially acquired pathogens were tested to validate the specificity of each probe for its corresponding gene. In total, 252 strains were used for validation of the assay, of which 175 were staphylococci. Strains are genetically and geographically diverse, representing isolates from New York, New Jersey, California, Montana, and Texas as well as Canada and Nigeria. All strains were classified correctly.
Group Other consists of vancomycin-susceptible enterococci (VSE), Klebsiella spp., group A Streptococcus pyogenes, Enterococcus gallinarum, Lactobacillus spp., Listeria monocytogenes, and Micrococcus spp.
The 9 out of 29 VRE strains negative for vanA were shown to be positive for vanB using a different molecular beacon probe.
Strains positive and negative for lukF were confirmed using conventional PCR with gel electrophoresis.