title: MALDI-TOF MS based carbapenemase detection from culture isolates and from positive blood culture vials.
abstract: BACKGROUND
  Antibiotic resistance in bacteria leads to massive health problems. Incidence of carbapenem and multidrug resistance in Gram-negative bacteria are increasing globally and turn out to be a very urgent challenge in health care. Resistant bacteria play an important clinical role during hospital outbreaks as well as in sepsis. Rapid diagnostic tests are necessary to provide immediate information for antimicrobial treatment and infection control measures.
  
  
  METHODS
  Our mass spectrometry-based assay was validated with 63 carbapenemase-producing Gram-negative bacterial isolates, and 35 carbapenem-resistant Gram-negative species with no carbapenemase production. These were analyzed from solid culture media and positive blood culture vials. After 4 h of incubation the carbapenemase products were analyzed with the MALDI-TOF MS. All the isolates were genotyped for carbapenemase genes by PCR and sequencing.
  
  
  RESULTS
  For culture isolates the concordance of hydrolysis assay to genetic results was 98 % for OXA variants, KPC, VIM, IMP, GIM, and NDM. In contrast, only 14 of 29 Acinetobacter baumannii isolates carrying the OXA and NDM genes could be identified from blood culture. However, from blood culture vials our method allowed the detection of carbapenemases in 98 % of Pseudomonas and Enterobacteriaceae isolates harboring different genes.
  
  
  CONCLUSIONS
  This MALDI-TOF MS-based assay permitted the detection of carbapenemases either from solid culture media (98-100 %) or blood culture vials (96 %) for all non-A. baumannii isolates within 4 h. In case of A. baumannii isolates the assay was highly sensitive for the detection of carbapenemases directly from solid culture media.
authors.affiliation: Institute for Medical Laboratory Diagnostics, Center for Clinical and Translational Research, Witten/Herdecke University, Heusnerstr. 40, 42283, Wuppertal, Germany. bg.id@msn.com.
authors.forename: B
authors.initials: B
authors.lastname: Ghebremedhin
authors.affiliation: Institute for Medical Laboratory Diagnostics, Center for Clinical and Translational Research, Witten/Herdecke University, Heusnerstr. 40, 42283, Wuppertal, Germany. alexander.halstenbach@uni-duesseldorf.de.
authors.forename: A
authors.initials: A
authors.lastname: Halstenbach
authors.affiliation: Institute for Medical Laboratory Diagnostics, Center for Clinical and Translational Research, Witten/Herdecke University, Heusnerstr. 40, 42283, Wuppertal, Germany. manuela.smiljanic@uni-duesseldorf.de.
authors.forename: M
authors.initials: M
authors.lastname: Smiljanic
authors.affiliation: Department of Medical Microbiology, Ruhr-University Bochum, Bochum, Germany. martin.kaase@rub.de.
authors.forename: M
authors.initials: M
authors.lastname: Kaase
authors.affiliation: Institute for Medical Laboratory Diagnostics, Center for Clinical and Translational Research, Witten/Herdecke University, Heusnerstr. 40, 42283, Wuppertal, Germany. parviz.ahmad-nejad@helioskliniken.de.
authors.forename: P
authors.initials: P
authors.lastname: Ahmad-Nejad
mesh_terms: D001419:Bacteria / Q000737:chemistry / Q000145:classification / Q000201:enzymology* / Q000302:isolation & purification*; D001424:Bacterial Infections / Q000097:blood / Q000382:microbiology*; D001426:Bacterial Proteins / Q000032:analysis* / Q000378:metabolism; D001769:Blood / Q000382:microbiology*; D006801:Humans; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D001618:beta-Lactamases / Q000032:analysis* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D001618:beta-Lactamases; C063912:carbapenemase
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