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Table 4 Identification by MALDI-TOF (direct and SepsiTyper (ST) methods) of Gram-positive cocci from positive blood cultures appearing monomicrobial at the Gram-stain, that resulted to be polymicrobial after subculture*

From: Rapid and reliable identification of Gram-negative bacteria and Gram-positive cocci by deposition of bacteria harvested from blood cultures onto the MALDI-TOF plate

 

No. of isolates

Species

Identification by use of MALDI-TOF MS with score (S) of:

No. of unidentified isolates

Unidentified second species

Total samples

S < 1.7

1.7 ≤ S < 2

2.0 ≥ S <2.3

S ≥ 2.3

 

Direct

ST

Direct

ST

Direct

ST

Direct

ST

Direct

ST

S. aureus

  

1

    

1

  

S. capitis

 

S. epidermidis

1

  

1

      

E. faecalis

 

S. capitis

    

1

1a

    

E. faecium

 

S. capitis

  

1

1a

      

S. epidermidis

 

S. hominis

    

1

    

1

S. haemolyticus

 

S. hominis

    

1

  

1

  

S. epidermidis

 

E. faecium

   

1

  

1

   

S. epidermidis

 

Total (%)

1 (14 %)

 

2 (29 %)

3 (43 %)

3 (43 %)

1 (14 %)

1 (14 %)

2 (29 %)

 

1 (14 %)

 

7

  1. *Using the results obtained with the routine methods by MALDI-TOF and Vitek 2 as comparators
  2. aST correctly identified only the second species