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 [%])bP valuec
Enterococci (64)
    Genus correct64 (100)64 (100)NS
    Species correct63 (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 correct49 (100)49 (100)NS
    Species correct49 (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 correct9 (100)9 (100)NS
    Species correct7 (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 correct22 (100)22 (100)NS
    Species correct19 (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 correct19 (90.5)21 (100)NS
    Species correct2 (9.5)4 (19.0)NS
    Major error(0)(0)
    Minor error12 (57.1)(0)<0.01
    No identification2 (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.