TABLE 2.
Detection of slow-VISA cells among clinical MRSA isolates by use of mupirocin
| Strain | Phenotypeb |
Vancomycin MIC (μg/ml) by Etest after various periods of incubation |
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| CLSI classification (48 h) | New classification | Without antibiotics |
With mupirocin at 0.032 μg/ml |
|||||||||
| 48 h | 72 h | 96 h | 120 h | 144 h | 48 h | 72 h | 96 h | 120 h | 144 h | |||
| 209P | VSSA (MSSA) | VSSA (MSSA) | 1.5 | 1.5 | 1.5 | 1.5 | 1.5 | 1.5 | 1.5 | 1.5 | 1.5 | 1.5 |
| N315ΔIP | VSSA (MRSA) | VSSA (MRSA) | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 |
| Mu3 | hVISA | hVISA | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 |
| Mu50 | VISA | VISA | 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 |
| MI (HIP5827) | VISA | VISA | 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 |
| Mu3-6R | VISA | Slow VISA | 8 | 8 | 12 | 12 | 16 | 16 | 16 | 16 | 16 | 16 |
| Clinical blood culture isolates from 9 hospitals | ||||||||||||
| MRSA212 | VSSA | VSSA | 1.5 | 2 | 2 | 2 | 2 | 3 | 3 | 3 | 3 | 3 |
| MRSA84 | VSSA | hVISA | 2 | 2 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 |
| MRSA220 | VSSA | hVISA | 1.5 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 |
| MRSA192 | VSSA | hVISA | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 |
| MRSA190 | VISA | Slow VISA | 4 | 8 | 8 | 8 | 8 | 12 | 12 | 12 | 12 | 12 |
| MRSA194 | VISA | Slow VISA | 4 | 6 | 8 | 12 | 12 | 8 | 12 | 12 | 12 | 12 |
| T series clinical blood culture isolatesa | ||||||||||||
| T12 | VISA | Slow VISA | 4 | 4 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 |
| T15 | VISA | Slow VISA | 4 | 6 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 |
| T61 | VISA | Slow VISA | 4 | 6 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 |
| T89 | VISA | Slow VISA | 4 | 8 | 16 | 16 | 16 | 16 | 16 | 16 | 16 | 16 |
| T122 | VISA | Slow VISA | 4 | 8 | 8 | 8 | 8 | 6 | 6 | 8 | 8 | 8 |
| T123 | VISA | Slow VISA | 4 | 6 | 8 | 8 | 8 | 6 | 8 | 8 | 8 | 8 |
| T12-L | hVISA | hVISA | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 |
| T15-L | hVISA | hVISA | 3 | 3 | 3 | 3 | 4 | 4 | 4 | 4 | 4 | 4 |
| T61-L | hVISA | hVISA | 3 | 3 | 3 | 3 | 4 | 6 | 6 | 6 | 6 | 6 |
| T89-L | hVISA | hVISA | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 |
| T122-L | VSSA | VSSA | 2 | 2 | 2 | 2 | 2 | 3 | 3 | 3 | 3 | 3 |
| T123-L | VSSA | VSSA | 2 | 2 | 2 | 2 | 2 | 3 | 3 | 3 | 3 | 3 |
a
T-L strains are revertants obtained from the original clinical strains by subculture for 5 days in the absence of antibiotics.
b
Slow-VISA strains showed increasing resistance to vancomycin after 72 h of incubation (vancomycin MICs of >4 μg/ml), although they had vancomycin MICs of >4 μg/ml after 48 h of incubation. The Mu3 and Mu50 isolates with the hVISA and VISA phenotypes had stable vancomycin MICs of 3 and 12 μg/ml, respectively, over time.