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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