259. Is It Time to Identify Acinetobacter spp. by Molecular Methods Only?
Session: Poster Abstract Session: Diagnostics: Typing and Sequencing
Thursday, October 8, 2015
Room: Poster Hall
Background: Identifying Acinetobacter isolates to the species level has proven challenging in clinical diagnostics. Proper species identification is clinically important as relevant differences exist between the species with regards to treatment decisions, epidemiology, and resistance profiles (e.g., carbapenem resistant [CR] or susceptible [CS]).

Methods: The species identity of 56 clinical Acinetobacter spp. isolates were determined using the Siemens MicroScan System, bioMérieux Vitek MS Plus MALDI-TOF, Bruker MALDI Biotyper, the BAC-BSI assay in development on the PCR/ESI-MS platform (Ibis Biosciences), and targeted PCR assays: gyrB multiplex PCR (species specific amplicons) and presence of Acinetobacter species-specific oxacillinases. Rep-PCR (DiversiLab Acinetobacter Fingerprinting kit) was used to determine if the isolates grouped by species.

Results: Both MicroScan and MALDI-TOF platforms identified all 56 isolates as A. baumannii (Ab). When tested using the BAC-BSI assay on the PCR/ESI-MS platform, 16 were identified as Ab and the remaining 40 as A. calcoaceticus (Ac). This discrepency prompted further investigation with targeted PCRs. The gyrB multiplex PCR confirmed the previous species identification of Ab in the 16 isolates (75% CR, 12/16); however, among the 40 designated as Ac, gyrB multiplex PCR identified 35 as A. pittii (Ap, 100% CS), 3 as A. nosocomialis (An, 100% CS), and 2 as Ab (100% CS). The blaOXA-51-like PCR confirmed the gyrB Ab species identification in all 18 Ab isolates. All 35 Ap identified by gyrB multiplex PCR were positive for the Ap intrinsic blaOXA-270-like gene; all others were negative. The intrinsic OXA multiplex PCR also revealed that 1 Ap isolate harbored both the intrinsic Ac and Ap specific blaOXA genes. As expected, all An were negative for intrinsic blaOXAs (this species has none). Rep-PCR was consistent with gyrB multiplex PCR groupings.

Conclusion: In the analysis of 56 Acinetobacter isolates, current standard post culture ID systems identified all isolates as Ab. Only the BAC-BSI assay alerted us to the presence of multiple species, upon which further targeted PCR revealed An or Ap. High-quality research and clinical studies require platforms to correctly identify Acinetobacter to the species level.

T. Nicholas Domitrovic, BA1, Andrea Hujer, BS2, Paul Higgins, PhD3, Harald Seifert, PhD4, Kristine M. Hujer, BS1, Michael R. Jacobs, MD, PhD5, Thomas Hall, PhD6, Christine Marzan, PhD6, Barry N. Kreiswirth, PhD7 and Robert A. Bonomo, MD8, (1)Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, OH, (2)Case Western Reserve University, Cleveland, OH, (3)University of Cologne, Cologne, Germany, (4)Institute for Med. Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany, (5)Case Western Reserve University/University Hospitals of Cleveland, Cleveland, OH, (6)Ibis Biosciences, Carlsbad, CA, (7)Phri TB Center, Rutgers University, Newark, NJ, (8)Pharmacology, Molecular Biology, and Microbiology, Case Western Reserve University, Cleveland, OH


T. N. Domitrovic, None

A. Hujer, None

P. Higgins, None

H. Seifert, None

K. M. Hujer, None

M. R. Jacobs, None

T. Hall, Ibis Biosciences, an Abbott Company: Employee , Salary

C. Marzan, Ibis Biosciences, an Abbott Company: Employee , Salary

B. N. Kreiswirth, None

R. A. Bonomo, AstraZeneca: Grant Investigator , Research grant
Merck: Grant Investigator , Research grant
Melinta: Grant Investigator , Research grant
VA Merit Review Board: Grant Investigator , Research grant
NIH: Grant Investigator , Research grant

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