MALDI-TOF MS for identification of Tsukamurella species: Tsukamurella tyrosinosolvens as the predominant species associated with ocular infections

Figures & data

Fig. 1 Phylogenetic trees showing the relationship of Tsukamurella strains included in this study, including 15 type and reference strains and 60 Tsukamurella isolates.

The tree was inferred from partial groEL sequence data (677 nucleotide positions of the trimmed sequence alignments respectively) by the maximum-likelihood method using the model GTR + I + G and Mycobacterium smegmatis MC² 155 (CP009494.1) as the outgroup. The scale bar indicates the estimated number of substitutions per base. Numbers at nodes indicate levels of bootstrap support calculated from 1000 trees and expressed as percentage. All names and accession numbers are given as cited in the GenBank database

Summary of Tsukamurella species isolated from different clinical specimens

Type of specimen	T. tyrosinosolvens (n = 31)	T. pulmonis (n = 9)	T. hongkongensis (n = 3)	T. sinensis (n = 2)	T. strandjordii (n = 1)
Eye (n = 18)	11	4	1	2	0
Sputum (n = 6)	4	0	1	0	1
Blood (n = 6)	4	1	1	0	0
Others (n = 9)
Axillary lymph node biopsy^a	1	0	0	0	0
Plantar granulation tissue^a	2	0	0	0	0
Lung tissue^a	1	0	0	0	0
Peritoneal tissue^a	1	0	0	0	0
Peritoneal dialysis fluid	1	0	0	0	0
Pus swab from submandibular skin	0	1	0	0	0
Superficial wound swab from hand	1	1	0	0	0
Unknown specimens (n = 7)	5	2	0	0	0

^a The recovery of these isolates was due to laboratory contamination during processing of the tissue specimens [previously reported in ref. 29]

MALDI-TOF MS results of 75 Tsukamurella species and 14 species of closely related genera using Bruker database and extended in-house database

Bacterial species	Total no. of isolates (n = 89)	No. of isolates resulting in the indicated score attained using:
		Bruker Reference Library V.6.0.0.0				Extended in-house database
		≥2.0	1.7–1.9	<1.7	Incorrect species identification	≥2.0	1.7–1.9	<1.7	Incorrect species identification
Type and reference (n = 15)^a
T. paurometabola	1	1	0	0	0	1	0	0	0
T. inchonensis	1	1	0	0	0	1	0	0	0
T. strandjordii	1	0	0	1	1	1	0	0	0
T. pulmonis	2	0	1	1	2	2	0	0	0
T. tyrosinosolvens	2	2	0	0	2	2	0	0	0
T. pseudospumae	2	0	0	2	2	2	0	0	0
T. spumae	1	0	1	0	1	1	0	0	0
T. soli	1	0	0	1	1	1	0	0	0
T. serpentis	1	0	0	1	1	1	0	0	0
T. hongkongensis	1	0	0	1	1	1	0	0	0
T. serpentis	2	0	0	2	2	2	0	0	0
Clinical or veterinary (n = 74)
T. tyrosinosolvens	31	20	10	1	31	31	0	0	0
T. pulmonis	25	0	9	16	25	25	0	0	0
T. hongkongensis	2	0	0	2	2	1	1	0	1
T. sinensis	1	0	0	1	1	1	0	0	0
T. strandjordii	1	0	0	1	1	1	0	0	0
N. nova	3	3	0	0	0	3	0	0	0
N. cyriacigeorgica	2	1	1	0	0	1	1	0	0
N. brasiliensis	1	0	1	0	0	0	1	0	0
N. farcinica	2	1	1	0	0	1	1	0	0
R. equi	2	2	0	0	0	2	0	0	0
R. erythropolis	1	1	0	0	0	1	0	0	0
G. sputi	2	2	0	0	0	2	0	0	0
G. bronchialis	1	1	0	0	0	1	0	0	0

^a Among the 15 type and reference strains, only 6 (40.0%) showed the correct genus with score ≥1.7 by MALDI-TOF MS using the Bruker Reference Library V.6.0.0.0

Fig. 2 MALDI-TOF MS spectra of T. tyrosinosolvens, T. pulmonis, T. hongkongensis, T. strandjordii, and T. sinensis.

The intensity in arbitrary units [a.u.] are shown on the y axis, and the masses (m/z) of the ions are shown on the x axis. The m/z values represent the mass-to-charge ratios

Fig. 3 Dendrogram generated from hierarchical cluster analysis of MALDI-TOF MS spectra of 15 type and reference strains and 60 Tsukamurella isolates included in this study.

Distances are displayed in relative units

ToKKWCharacterization of a Tsukamurella pseudo-outbreak by phenotypic tests, 16S rRNA sequencing, pulsed-field gel electrophoresis, and metabolic footprintingJ. Clin. Microbiol.20135133433810.1128/JCM.02845-123536211

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