Table 1.
Performance of MALDI Biotyper in comparison to conventional testing for identification of commonly encountered bacteria in a microbiology laboratory
| Bacterium | No. of isolates tested | No. of tests performeda | No. of MALDI Biotyper tests withb: |
Proportion of tests correct to indicated level |
||||
|---|---|---|---|---|---|---|---|---|
| Incorrect identificationc | Unreliable identification | Correct identification with score of: |
||||||
| 1.7–1.9 | ≥2 | Genus | Species | |||||
| Anaerobes | 12 | 36 | 1 | 12 | 23 | 0.97 | 0.64 | |
| Bacteroides fragilis | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Bacteroides nordii | 1 | 3 | 3 | 1.00 | 0.00 | |||
| Bacteroides vulgatus | 2 | 6 | 6 | 1.00 | 1.00 | |||
| Bacteroides uniformis | 1 | 3 | 2 | 1 | 1.00 | 0.33 | ||
| Clostridium difficile | 2 | 6 | 1 | 5 | 1.00 | 0.83 | ||
| Clostridium perfringens | 2 | 6 | 6 | 1.00 | 1.00 | |||
| Finegoldia magna | 1 | 3 | 1 | 1 | 1 | 0.67 | 0.33 | |
| Peptostreptococcus anaerobius | 1 | 3 | 3 | 1.00 | 0.00 | |||
| Prevotella bivia | 1 | 3 | 2 | 1 | 1.00 | 0.33 | ||
| Enterobacteriaceae | 298 | 894 | 28 | 7 | 81 | 778 | 0.96 | 0.87 |
| Citrobacter freundii | 2 | 6 | 6 | 1.00 | 1.00 | |||
| Citrobacter koseri | 8 | 24 | 1 | 23 | 1.00 | 0.96 | ||
| Enterobacter aerogenes | 11 | 33 | 1 | 32 | 0.97 | 0.97 | ||
| Enterobacter asburiae | 3 | 9 | 9 | 1.00 | 1.00 | |||
| Enterobacter cloacae | 21 | 63 | 3 | 4 | 56 | 0.95 | 0.88 | |
| Escherichia coli | 116 | 348 | 1 | 6 | 341 | 1.00 | 0.98 | |
| Klebsiella oxytoca | 17 | 51 | 1 | 50 | 0.98 | 0.98 | ||
| Klebsiella pneumoniae | 44 | 132 | 2 | 4 | 126 | 0.98 | 0.95 | |
| Morganella morganii | 4 | 12 | 12 | 1.00 | 1.00 | |||
| Plesiomonas shigelloides | 2 | 6 | 1 | 5 | 1.00 | 0.83 | ||
| Proteus mirabilis | 30 | 90 | 2 | 5 | 83 | 0.98 | 0.92 | |
| Providencia stuartii | 2 | 6 | 6 | 1.00 | 1.00 | |||
| Salmonella Typhimurium | 20 | 60 | 60 | 1.00 | 0.00 | |||
| Serratia marcescens | 8 | 24 | 1 | 0 | 23 | 0.96 | 0.96 | |
| Shigella boydii | 1 | 3 | 3 | 0.00 | 0.00 | |||
| Shigella dysenteriae | 1 | 3 | 3 | 0.00 | 0.00 | |||
| Shigella flexneri | 2 | 6 | 6 | 0.00 | 0.00 | |||
| Shigella sonnei | 4 | 12 | 12 | 0.00 | 0.00 | |||
| Yersinia enterocolitica | 2 | 6 | 6 | 1.00 | 1.00 | |||
| Gram-positive rods | 33 | 99 | 8 | 34 | 57 | 0.91 | 0.57 | |
| Arcanobacterium bernardiae | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Arcanobacterium haemolyticum | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Bacillus cereus | 3 | 9 | 3 | 6 | 1.00 | 0.67 | ||
| Clostridium innocuum | 1 | 3 | 1 | 1 | 1 | 0.67 | 0.33 | |
| Corynebacterium amycolatum | 2 | 6 | 1 | 5 | 1.00 | 0.83 | ||
| Corynebacterium aurimucosum | 1 | 3 | 1 | 2 | 0.67 | 0.00 | ||
| Corynebacterium jeikeium | 1 | 3 | 1 | 2 | 0.67 | 0.67 | ||
| Dermabacter hominis | 2 | 6 | 6 | 1.00 | 0.00 | |||
| Dermatophilus congolensis | 1 | 3 | 3 | 1.00 | 0.00 | |||
| Erysipelothrix rhusiopathiae | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Janibacter species | 1 | 3 | 1 | 2 | 0.67 | 0.00 | ||
| Lactobacillus sakei | 1 | 3 | 1 | 1 | 1 | 0.67 | 0.33 | |
| Lactobacillus fermentum | 1 | 3 | 2 | 1 | 1.00 | 0.33 | ||
| Lactobacillus rhamnosus | 3 | 9 | 9 | 1.00 | 0.00 | |||
| Leuconostoc garlicum | 1 | 3 | 3 | 1.00 | 0.00 | |||
| Listeria monocytogenes | 9 | 27 | 1 | 26 | 1.00 | 0.96 | ||
| Raoultella planticola | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Rhodococcus species | 1 | 3 | 3 | 0.00 | 0.00 | |||
| Rothia dentocariosa | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Gram-positive cocci | 429 | 1,287 | 24 | 31 | 160 | 1,072 | 0.95 | 0.83 |
| Aerococcus urinae | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Aerococcus viridans | 1 | 3 | 1 | 2 | 1.00 | 0.67 | ||
| Enterococcus casseliflavus | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Enterococcus faecalis | 37 | 111 | 2 | 11 | 98 | 0.98 | 0.88 | |
| Enterococcus faecium | 25 | 75 | 75 | 1.00 | 1.00 | |||
| Enterococcus gallinarum | 2 | 6 | 6 | 1.00 | 1.00 | |||
| Enterococcus raffinosus | 1 | 3 | 2 | 1 | 1.00 | 0.33 | ||
| Granulicatella adiacens | 1 | 3 | 2 | 1 | 0.33 | 0.00 | ||
| Micrococcus luteus | 8 | 24 | 3 | 3 | 18 | 0.88 | 0.75 | |
| Staphylococcus aureus | 146 | 438 | 5 | 22 | 411 | 0.99 | 0.94 | |
| Staphylococcus capitis | 20 | 60 | 1 | 9 | 50 | 0.98 | 0.83 | |
| Staphylococcus cohnii | 1 | 3 | 3 | 1.00 | 0.00 | |||
| Staphylococcus epidermidis | 36 | 108 | 3 | 25 | 80 | 0.95 | 0.72 | |
| Staphylococcus haemolyticus | 2 | 6 | 1 | 5 | 1.00 | 0.83 | ||
| Staphylococcus hominis | 17 | 51 | 3 | 48 | 1.00 | 0.94 | ||
| Staphylococcus lugdunensis | 3 | 9 | 1 | 2 | 6 | 0.89 | 0.67 | |
| Streptrococcus lutetiensis | 1 | 3 | 1 | 2 | 0.67 | 0.00 | ||
| Staphylococcus pettenkoferi | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Staphylococcus saprophyticus | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Staphylococcus warneri | 5 | 15 | 10 | 5 | 1.00 | 0.33 | ||
| Streptococcus agalactiae | 22 | 66 | 3 | 2 | 5 | 56 | 0.93 | 0.85 |
| Streptococcus anginosus | 9 | 27 | 4 | 11 | 12 | 0.85 | 0.44 | |
| Streptococcus canis | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Streptococcus constellatus | 8 | 24 | 3 | 5 | 16 | 0.88 | 0.67 | |
| Streptococcus cristatus | 2 | 6 | 6 | 1.00 | 1.00 | |||
| Streptococcus dysgalactiae | 15 | 45 | 2 | 20 | 23 | 0.96 | 0.51 | |
| Streptococcus gordonii | 2 | 6 | 1 | 4 | 1 | 0.83 | 0.17 | |
| Streptococcus gallolyticus | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Streptococcus mitis group | 6 | 18 | 18 | 0 | 0 | 0.00 | 0.00 | |
| Streptococcus mutans | 2 | 6 | 6 | 1.00 | 1.00 | |||
| Streptococcus pneumoniae | 25 | 75 | 2 | 12 | 61 | 0.97 | 0.81 | |
| Streptococcus pyogenes | 19 | 57 | 1 | 2 | 54 | 0.98 | 0.95 | |
| Streptococcus salivarius | 3 | 9 | 1 | 3 | 5 | 0.89 | 0.56 | |
| Streptococcus sanguinis | 2 | 6 | 6 | 1.00 | 1.00 | |||
| Streptococcus sinensis | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Streptococcus vestibularis | 1 | 3 | 3 | 1.00 | 0.00 | |||
| Miscellaneous gram-negatives | 78 | 234 | 18 | 216 | 1.00 | 0.92 | ||
| Aeromonas hydrophila | 2 | 6 | 6 | 1.00 | 1.00 | |||
| Aeromonas veronii | 2 | 6 | 6 | 1.00 | 1.00 | |||
| Aggregatibacter aphrophilus | 2 | 6 | 3 | 3 | 1.00 | 0.50 | ||
| Campylobacter coli | 1 | 3 | 1 | 2 | 1.00 | 0.67 | ||
| Capnocytophaga ochracea | 1 | 3 | 2 | 1 | 1.00 | 0.33 | ||
| Eikenella corrodens | 3 | 9 | 3 | 6 | 1.00 | 0.67 | ||
| Haemophilus influenzae | 32 | 96 | 2 | 94 | 1.00 | 0.98 | ||
| Haemophilus parainfluenzae | 1 | 3 | 1 | 2 | 1.00 | 0.67 | ||
| Helcococcus kunzii | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Kingella kingae | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Moraxella catarrhalis | 3 | 9 | 3 | 6 | 1.00 | 0.67 | ||
| Neisseria elongata | 1 | 3 | 3 | 1.00 | 0.00 | |||
| Neisseria gonorrhoeae | 14 | 42 | 42 | 1.00 | 1.00 | |||
| Neisseria meningitidis | 13 | 39 | 39 | 1.00 | 1.00 | |||
| Pasteurella multocida | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Non-fermentative gram-negative rods | 77 | 231 | 1 | 25 | 205 | 1.00 | 0.89 | |
| Acinetobacter baumannii | 2 | 6 | 6 | 1.00 | 1.00 | |||
| Acinetobacter lwoffii | 5 | 15 | 2 | 13 | 1.00 | 0.87 | ||
| Achromobacter xylosoxidans | 3 | 9 | 9 | 1.00 | 0.00 | |||
| Agrobacterium tumefaciens | 1 | 3 | 3 | 1.00 | 0.00 | |||
| Burkholderia cepacia | 7 | 21 | 21 | 1.00 | 1.00 | |||
| Myroides odoratimimus | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Ochrobactrum anthropi | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Photorhabdus asymbiotica | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Pseudomonas aeruginosa | 44 | 132 | 1 | 131 | 0.99 | 0.99 | ||
| Pseudomonas geniculata | 2 | 6 | 4 | 2 | 1.00 | 0.33 | ||
| Pseudomonas hibiscicola | 2 | 6 | 1 | 5 | 1.00 | 0.83 | ||
| Pseudomonas koreensis | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Pseudomonas putida | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Roseomonas gilardii | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Roseomonas mucosa | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Shewanella putrefaciens | 1 | 3 | 3 | 1.00 | 1.00 | |||
| Stenotrophomonas maltophilia | 3 | 9 | 6 | 3 | 1.00 | 0.33 | ||
| Total | 927 | 2781 | 52 | 48 | 330 | 2351 | 0.96 | 0.84 |
a
All isolates were tested in triplicate.
b
Results were compared to those of conventional testing, with concordant results accepted as the correct identification. Isolates with discordant results were retested following crude extraction with formic acid, and if unresolved, 16S rRNA sequencing was used to confirm the identification. An unreliable identification was defined by a score of ≤1.7. In accordance with the manufacturer's specifications, identification scores of ≥2 and between 1.7 and 1.9 were required for a reliable identification to the species or genus level, respectively.
c
Incorrect identifications include major (incorrect genus) and minor (correct genus, incorrect species) errors.