TABLE 5.
Identification of Gram-positive cocci in chains by MALDI-TOF MS and routine biochemical phenotypic methodsa
| Organism group and identification parameter (no. of isolates) | MALDI-TOF MS identification (no. of isolates [%]) | Routine biochemical phenotypic identification (no. of isolates [%])b | P valuec |
|---|---|---|---|
| Enterococci (64) | |||
| Genus correct | 64 (100) | 64 (100) | NS |
| Species correct | 63 (98.4) | 61 (95.3) | NS |
| Major error | (0) | (0) | |
| Minor error | (0) | 3 (4.7) | NS |
| No identification | (0) | (0) | |
| No uniform result | (0) | NA | |
| Hemolytic streptococci (49) | |||
| Genus correct | 49 (100) | 49 (100) | NS |
| Species correct | 49 (100) | 49 (100) | NS |
| Major error | (0) | (0) | |
| Minor error | (0) | (0) | |
| No identification | (0) | (0) | |
| No uniform result | (0) | NA | |
| Streptococcus milleri group (9) | |||
| Genus correct | 9 (100) | 9 (100) | NS |
| Species correct | 7 (77.8) | 9 (100) | NS |
| Major error | (0) | (0) | |
| Minor error | (0) | (0) | |
| No identification | (0) | (0) | |
| No uniform result | (0) | NA | |
| Pneumococci (22) | |||
| Genus correct | 22 (100) | 22 (100) | NS |
| Species correct | 19 (86.4) | 22 (100) | NS |
| Major error | (0) | (0) | |
| Minor error | (0) | (0) | |
| No identification | (0) | (0) | |
| No uniform result | (0) | NA | |
| Viridans streptococci (21) | |||
| Genus correct | 19 (90.5) | 21 (100) | NS |
| Species correct | 2 (9.5) | 4 (19.0) | NS |
| Major error | (0) | (0) | |
| Minor error | 12 (57.1) | (0) | <0.01 |
| No identification | 2 (9.5) | (0) | |
| No uniform result | (0) | NA |
a
Isolates were tested by MALDI-TOF MS (duplicate) and conventional biochemical methods. Definite identification was set when phenotypic biochemical methods exactly matched MALDI-TOF MS identification or by 16S sequencing. See Table 3 footnote and the text for an explanation of MALDI-TOF MS scoring.
b
NA, not applicable.
c
P values were calculated by comparison of MALDI-TOF MS identification with conventional identification (chi-square test). NS, not significant.