Author:
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Marí Almirall, Marta; Cosgaya, Clara; Higgins, Paul G.; Assche, Ado Van; Telli, Murat; Huys, Geert; Lievens, Bart; Seifert, Harald; Dijkshoorn, Lenie; Roca, Ignasi; Vila Estapé, Jordi
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Abstract:
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OBJECTIVES: Rapid identification of Acinetobacter species is
critical since members of the A. baumannii (Ab) group differ in
antibiotic susceptibility and clinical outcomes. A. baumannii,
A. pittii and A. nosocomialis can be identified by MALDI-TOF/MS,
while the novel species A. seifertii and A. dijkshoorniae
cannot. Low identification rates for A. nosocomialis have also
been reported. We evaluated the use of MALDI-TOF/MS to identify
isolates of A. seifertii and A. dijkshoorniae and revisited the
identification of A. nosocomialis to update the Bruker taxonomy
database. METHODS: Species characterisation was performed by
rpoB-clustering and MLSA. MALDI-TOF/MS spectra were recovered
from formic acid/acetonitrile bacterial extracts overlaid with
alpha-cyano-4-hydroxy-cinnamic acid matrix on a MicroflexLT in
linear positive mode and 2,000-20,000 m/z range mass. Spectra
were examined with the ClinProTools v2.2 software. Mean spectra
(MSP) were created with the BioTyper software. RESULTS:
Seventy-eight Acinetobacter isolates representative of the Ab
group were used to calculate the average spectra/species and
generate pattern recognition models. Species-specific peaks were
identified for all species, and MSPs derived from 3 A.
seifertii, 2 A. dijkshoorniae and 2 A. nosocomialis strains were
added to the Bruker taxonomy database, allowing successful
identification of all isolates using spectra from either
bacterial extracts or direct colonies, resulting in a positive
predictive value (PPV) of 99.6% (777/780) and 96.8% (302/312),
respectively. CONCLUSIONS: The use of post-processing data
software identified statistically significant species-specific
peaks to generate reference signatures for rapid accurate
identification of species within the Ab group, providing
relevant information for the clinical management of
Acinetobacter infections. |