title: Rapid and sensitive detection of carbapenemase activity in Acinetobacter baumannii using superficially porous liquid chromatography-tandem mass spectrometry.
abstract: BACKGROUND
  The emergence and spread of carbapenem-resistant Acinetobacter baumannii poses a challenge for optimizing antibiotic therapies and preventing outbreaks. Traditional phenotypic assays such as the modified Hodge test (MHT) or polymerase chain reaction (PCR)-based detection of the carbapenemase genes are time-consuming and complicated. Therefore, new approaches for the efficient detection of carbapenemase-producing A. baumannii are urgently required.
  
  
  METHODS
  In this study, we used the superficially porous liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay to measure carbapenem hydrolysis in a solution spiked with test strains of A. baumannii. The rate of carbapenem hydrolysis during incubation was expressed as the ratio of the carbapenem peak area of the test A. baumannii strains to the noncarbapenemase-producing A. baumannii ATCC 17978. This method can accurately measure the carbapenem hydrolysis rate and, therefore, can effectively identify carbapenemase-producing strains within 75 minutes.
  
  
  RESULTS
  A total of 112 A. baumannii strains were used in this study, including 103 clinical isolates with 68 carbapenem-resistant strains and 35 carbapenem-susceptible strains, seven ATCC strains and two selected mutants. The results of the superficially porous LC-MS/MS assay showed higher detection sensitivity compared to the results of the MHT.
  
  
  CONCLUSIONS
  Our results demonstrate the ability of the former method to routinely detect carbapenemase-producing A. baumannii.
authors.affiliation: Department of Laboratory Medicine and Biotechnology, Tzu Chi University, Hualien, Taiwan.
authors.forename: Huei-Ru
authors.initials: HR
authors.lastname: Lin
authors.affiliation: Department of Laboratory Medicine and Biotechnology, Tzu Chi University, Hualien, Taiwan.
authors.forename: Anren
authors.initials: A
authors.lastname: Hu
authors.affiliation: Department of Laboratory Medicine and Biotechnology, Tzu Chi University, Hualien, Taiwan.
authors.forename: Meng-Jiun
authors.initials: MJ
authors.lastname: Lai
authors.affiliation: Department of Laboratory Medicine and Biotechnology, Tzu Chi University, Hualien, Taiwan.
authors.forename: Chih-Wei
authors.initials: CW
authors.lastname: Chiang
authors.affiliation: Department of Laboratory Medicine and Biotechnology, Tzu Chi University, Hualien, Taiwan.
authors.forename: Chao-Chuan
authors.initials: CC
authors.lastname: Liao
authors.affiliation: Department of Laboratory Medicine and Biotechnology, Tzu Chi University, Hualien, Taiwan; Department of Laboratory Medicine, Buddhist Tzu Chi General Hospital, Hualien, Taiwan. Electronic address: kaichih@mail.tcu.edu.tw.
authors.forename: Kai-Chih
authors.initials: KC
authors.lastname: Chang
mesh_terms: D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000302:isolation & purification / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D002853:Chromatography, Liquid / Q000379:methods*; D024901:Drug Resistance, Multiple, Bacterial; D006801:Humans; D015378:Imipenem / Q000378:metabolism*; D000077731:Meropenem; D053719:Tandem Mass Spectrometry / Q000379:methods*; D013845:Thienamycins / Q000378:metabolism*; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D013845:Thienamycins; D015378:Imipenem; D001618:beta-Lactamases; C063912:carbapenemase; D000077731:Meropenem
keywords: Acinetobacter baumannii; carbapenemase; superficially porous liquid chromatography; tandem mass spectrometry