Improvement of MALDI-TOF MS profiling for the differentiation of species within the Acinetobacter calcoaceticus-Acinetobacter baumannii complex.
MALDI-TOF MS is currently becoming the method of choice for rapid identification of bacterial species in routine diagnostics. Yet, this method suffers from the inability to differentiate reliably between some closely related bacterial species including those of the Acinetobacter calcoaceticus-Acinetobacter baumannii (ACB) complex, namely A. baumannii and Acinetobacter nosocomialis. In the present study, we evaluated a protocol which was different from that used in the Bruker Daltonics identification system (MALDI BioTyper) to improve species identification using a taxonomically precisely defined set of 105 strains representing the four validly named species of the ACB complex. The novel protocol is based on the change in matrix composition from alpha-cyano-4-hydroxycinnamic acid (saturated solution in water:acetonitrile:trifluoroacetic acid, 47.5:50:2.5, v/v) to ferulic acid (12.5mgml(-1) solution in water:acetonitrile:formic acid 50:33:17, v/v), while the other steps of sample processing remain unchanged. Compared to the standard protocol, the novel one extended the range of detected compounds towards higher molecular weight, produced signals with better mass resolution, and allowed the detection of species-specific signals. As a result, differentiation of A. nosocomialis and A. baumannii strains by cluster analysis was improved and 13 A. nosocomialis strains, assigned erroneously or ambiguously by using the standard protocol, were correctly identified.
Research Group Proteomics, CEITEC - Central European Institute of Technology, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic; National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic.
Ondrej
O
Šedo
Alexandr
A
Nemec
Lenka
L
Křížová
Magdaléna
M
Kačalová
Zbyněk
Z
Zdráhal
D000150:Acinetobacter / Q000737:chemistry* / Q000145:classification* / Q000302:isolation & purification; D001431:Bacteriological Techniques / Q000379:methods*; D016000:Cluster Analysis; D013048:Specimen Handling / Q000379:methods; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
ACB complex; Acinetobacter calcoaceticus–Acinetobacter baumannii complex; Bacteria profiling; BioTyper; CHCA; FA; FerA; MALDI-TOF MS; Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry; TFA; UPGMA; alpha-cyano-4-hydroxycinnamic acid; ferulic acid; formic acid; trifluoroacetic acid; unweighted pair group average linked method