Comparison of Acinetobacter calcoaceticus-baumannii Complex Identification by MALDI-TOF Mass Spectrometry and Biochemical Method, Using Whole‑genome Sequencing as the Reference Standard

Atitiya Prakika,1,2 Pattaraporn Srisai,1,2 Nut Nithimongkolchai,1,2 Aranya Khongmee,3 Varis Manbenmad,1,3 Chanchai Hongsa,1,3 Waewta Kuwatjanakul,4 Lumyai Wonglakorn,4 Chidchamai Kewcharoenwong,3,5 Ganjana Lertmemongkolchai,3,5 Kiatichai Faksri,1,2 Arnone Nithichanon1,2 1Department of Microbiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand; 2Research and Diagnostic Center for Emerging Infectious Diseases (RCEID), Khon Kaen University, Khon Kaen, Thailand; 3Centre for Research and Development of Medical Diagnostic Laboratories, Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen, Thailand; 4Clinical Microbiology Unit, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand; 5Department of Medical Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai, ThailandCorrespondence: Arnone Nithichanon, Email [email protected]: Given the limited treatment options for Acinetobacter infections due to drug resistance, timely and accurate diagnosis is crucial for effective management. This study evaluated the performances of matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) in identifying Acinetobacter bacteria.Methods: Retrospective forty bacterial isolates from Thailand previously identified as A. baumannii using biochemical method were recruited. The retrospective diagnostic performances of biochemical method and MALDI-TOF MS were compared, considering whole-genome sequencing (WGS) as the reference standard.Results: For identification performance, accuracy was 70% for the biochemical method, 82.5% for MALDI-TOF MS using direct colony samples, and 80% for MALDI-TOF MS using protein extract samples. In comparison to WGS, the direct colony method achieved the highest typing concordance. Regarding processing speed, MALDI-TOF MS effectively reduces the turnaround time compared to the biochemical method (p < 0.0001).Conclusion: MALDI-TOF MS significantly outperforms biochemical method in the species-level identification of Acinetobacter. The superior efficacies in terms of accuracy, resolution, and speed emphasize the technical robustness of MALDI-TOF MS and position the method as an excellent identification technique for Acinetobacter isolates.Keywords: Acinetobacter, MALDI-TOF MS, whole-genome sequencing, microbiology, bacterial identification