TABLE 1.

High-confidence identifications by MALDI-TOF system and taxonomy

Conventional identification (na)MS results
BrukerbShimadzuc
No. of high-confidence identifications% of isolates identifiedNo. (%) incorrectNo. of high-confidence identifications% of isolates identifiedNo. (%) incorrect
Escherichia coli (216)216100216100
Klebsiella pneumoniae (38)381003387
Enterobacter cloacae (35)351002777
Proteus mirabilis (32)3210032100
Serratia marcescens (24)241002396
Klebsiella oxytoca (19)189519100
Citrobacter koseri (12)1210012100
Morganella morganii (12)1210012100
Other members of the Enterobacteraciae (28)281002589
Pseudomonas aeruginosa (30)3010030100
Haemophilus influenzae (12)1210012100
Other aerobic Gram-negatives (38)36951 (2.8)3592
Staphylococcus aureus (55)5510055100
Staphylococcus epidermidis (43)41951 (2.4)41951 (2.4)
Other Staphylococcus isolates (13)131001185
Enterococcus faecalis (50)40803468
Enterococcus faecium (11)982655
Streptococci (17)7413 (42.9)7412 (28.6)
Other Gram-positive aerobes (9)889111
Gram-negative anaerobes (6)1170
Gram-positive anaerobes (7)4571 (25.0)343
No result (13)d 969538
Total (720)680946 (0.9)639893 (0.5)
  • a n, no. of isolates.

  • b The six incorrect Bruker results were as follows: one isolate identified as Achromobacter xylosoxidans by 16S analysis, not identified by biochemical methods, and identified as Achromobacter denitrificans by MS; one isolate not identified by 16S analysis, identified as Staphylococcus epidermidis by biochemical methods, and identified as Staphylococcus capitis by MS; one isolate identified to the genus level only by 16S analysis, identified as Streptococcus mitis by biochemical methods, and identified as Streptococcus pneumoniae by MS; two isolates identified to the genus level only by 16S analysis, identified as Streptococcus bovis by biochemical methods, and identified as Streptococcus lutiensis by MS; and one isolate identified as Clostridium boltei by 16S analysis, not identified by biochemical methods, and identified as Clostridium casei by MS.

  • c The three incorrect Shimadzu results were as follows: one isolate identified to the genus level only by 16S, identified as Staphylococcus epidermidis by biochemical methods, and identified ambiguously as Staphylococcus capitis or Staphylococcus caprae by MS; two isolates identified to the genus level only by 16S analysis, as Streptococcus mitis by biochemical methods, and as Streptococcus oralis and Streptococcus pneumoniae by MS.

  • d See footnote b of Table 3.