Species identification of Acinetobacter calcoaceticus-Acinetobacter baumannii complex by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Abstract

Objective To evaluate the ability of matrix-assisted laser desorption/ionization timeof-flight mass spectrometry (MALDI-TOF MS) in identifying species of Acinetobacter calcoaceticus-Acinetobacter baumannii complex,and investigate the species distribution of Acinetobacter calcoaceticus-Acinetobacter baumannii complex isolated in our hospital. Methods A total of 502 nonduplicate clinical isolates of Acinetobacter calcoaceticus-Acinetobacter baumannii complex were retrospectively collected from the second affiliated hospital of Zhejiang University between January 2012 and July 2012.All strains were re-identified by MALDI-TOF MS and were also verified by sequence analysis of 16S-23S rRNA gene spacer region. Results Among all the 502 strains of Acinetobacter calcoaceticus-Acinetobacter baumannii complex,identificaion results provided by MALDI-TOF MS were A.baumannii (431,85.9%),A.pittii (68,13.5%),A.calcoaceticus (3,0.6%).Sequence analysis of 16S-23S rRNA gene spacer region was used to identify all the 502 strains:403 (80.3%) were identified as A.baumannii,68 (13.5%) as A.pittii,28 (5.6%) as A.nosocomialis and 3 (0.6%) as A.calcoaceticus.MALDI-TOF MS correctly identified all the strains but erroneously identified all 28 strains of A.nosocomialis as A.baumannii,compared with sequence analysis of 16S-23S rRNA gene spacer region. Conclusions MALDI-TOF MS can be used as a fast,simple,reliable and excellently reproducible method to identify members of Acinetobacter calcoaceticus-Acinetobacter baumannii complex at low costs.MALDI-TOF MS is expected to be an ideal technique for routine clinical microbiology testing in the future.(Chin J Lab Med,2013,36:1115-1119) Key words: Acinetobacter calcoaceticus; Acinetobacter baumannii; Spectrometry; mass; matrix-assisted laser desorption-ionization