Table 5.
Discrepant results with MALDI-TOF MS compared to phenotypic identificationa
| Phenotypic IDb | MALDI-TOF ID | MALDI-TOF scorec | Methods for resolution/final IDd |
|---|---|---|---|
| Streptococcus mitis group | Streptococcus pneumoniae | 1.915 | Phenotypic: BS, P disk, Vitek |
| Streptococcus mitis group | Streptococcus pneumoniae | 2.001 | Phenotypic: BS, P disk, Vitek |
| Staphylococcus aureus | Staphylococcus intermedius | 2.2 | Phenotypic: PYR |
| Micrococcus sp. (Vitek) | Rhodococcus equi | 2.269 | 16S rRNA gene sequencing: Rhodococcus equi |
| Sphingomonas paucimobilis (GS, Vitek) | Cellulosimicrobium cellulans | 2.221 | 16S rRNA gene sequencing: Cellulosimicrobium cellulans/funkei |
| No ID (GS, motility, catalase, and colony morphology) | Paenibacillus amylolyticus | 1.754 | 16S rRNA gene sequencing: Paenibacillus sp. |
| No ID (GS, catalase, and colony morphology) | Rothia aeria | 2.063 | 16S rRNA gene sequencing: Rothia sp. |
| Sphingomonas paucimobilis (GS, Vitek) | Arthrobacter oxydans | 2.16 | 16S rRNA gene sequencing: Arthrobacter sp. |
| No ID (Vitek, Phoenix NaCl, ESC, VP) | Streptococcus equinus | 2.095 | 16S rRNA gene sequencing: Streptococcus bovis group |
| Streptococcus bovis group (Vitek, Phoenix, growth in 6.5% sodium chloride broth, ESC, VP) | Streptococcus equinus | 2.056 | 16S rRNA gene sequencing: Streptococcus bovis group |
| Corynebacterium sp. (GS, catalase) | Actinomyces neuii | 2.06 | 16S rRNA gene sequencing: Actinomyces sp. |
| VGS (Vitek, Phoenix) | Streptococcus parasanguinis | 2.263 | 16S rRNA gene sequencing: Streptococcus parasanguinis/mitis/oralis |
| VGS (Phoenix) | Streptococcus parasanguinis | 1.841 | 16S rRNA gene sequencing: Streptococcus parasanguinis/mitis/oralis |
| Coryneform bacteria (GS) | Cellulosimicrobium cellulans | 2.042 | 16S rRNA gene sequencing: Cellulosimicrobium cellulans |
| Sphingomonas paucimobilis (GS, Vitek) | Cellulosimicrobium cellulans | 2.164 | 16S rRNA gene sequencing: Cellulosimicrobium cellulurum/funkei |
| Group B beta-hemolytic Streptococcus spp. (GS, catalase, colony morphology, latex) | Streptococcus dysgalactiae | 2.02 | Repeat latex agglutination was positive for group G |
| Corynebacterium spp. (GS, CAT, Vitek, ESC, urea) | Rothia dentocariosa | 2.242 | 16S rRNA gene sequencing: Rothia dentocariosa |
| Leuconostoc sp./Aerococcus viridans (Vitek/Phoenix) | Leuconostoc lactis | 1.899 | 16S rRNA gene sequencing: Leuconostoc lactis |
| Coryneform bacteria (GS, catalase) | Actinomyces radingae | 1.976 | 16S rRNA gene sequencing: Actinomyces sp. |
a
The correct identifications are in bold type.
b
ID, identification.
c
All isolates were identified by MALDI-TOF MS using the DS+FA method of bacterial preparation.
d
BS, bile solubility; P disk, optochin disk; GS, Gram stain; ESC, esculin; PYR, pyrolidonyl arylamidase.