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Table 2 Identification by MALDI-TOF (direct method) of Gram-negative bacilli 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

Species

Identification by use of direct method MALDI- TOF MS

Total samples

Correct, with score (S) of:

Unidentified species

1.7 ≤ S < 2

2.0 ≥ S < .3

S ≥ 2.3

Klebsiella pneumoniae

  

1

Escherichia coli

1

Klebsiella pneumoniae

 

1

 

Proteus mirabilis

1

Klebsiella pneumoniae

  

2

Acinetobacter baumannii

2

Klebsiella pneumoniae

 

1

 

Acinetobacter calcoaceticus

1

Klebsiella pneumoniae

1

  

Serratia marcescens

1

Escherichia coli

 

1

 

Pseudomonas aeruginosa

1

Enterobacter aerogenes

 

1

 

Candida guillermondii

1

Pseudomonas aeruginosa

 

1

 

Klebsiella pneumoniae

1

Pseudomonas aeruginosa

 

1

 

Candida tropicalis

1

Acinetobacter baumannii

 

1

 

Klebsiella pneumoniae

1

Acinetobacter baumannii

1

  

Staphylococcus epidermidis

1

Stenotrophomonas maltophilia

 

1

 

Candida glabrata

1

No identification

   

Lactobacillus paracasei and Candida krusei

1

No identification

   

Serratia marcescens and Klebsiella oxytoca

1

Total (%)

2 (13.3)

8 (53.3)

3 (20 %)

 

15

  1. *Using the results obtained with the routine methods by MALDI-TOF and Vitek 2 as comparators. No isolates were misidentified. No isolates were identified with scores ≤ 1.7