title: Comparative evaluation of minocycline susceptibility testing methods in carbapenem-resistant Acinetobacter baumannii.
abstract: In this study, the performance of two commonly used routine antimicrobial susceptibility testing methods, the automated VITEK(®)2 system and Etest (bioMérieux, Marcy-l'Étoile, France), was compared with the standard broth microdilution (BMD) method on 87 multidrug- and carbapenem-resistant Acinetobacter baumannii clinical isolates. Clinical and Laboratory Standards Institute (CLSI) 2015 breakpoints (susceptible, ≤4 mg/L; intermediate, 8 mg/L; and resistant, ≥16 mg/L) were used. Minocycline showed excellent activity, with 94.3% of isolates susceptible by BMD (VITEK(®)2, 73.6%; Etest, 63.2%). The MIC50/90 values (minimum inhibitory concentrations required to inhibit 50% and 90% of the isolates, respectively) were as follows: BMD, 1/4 mg/L; VITEK(®)2, ≤1/8 mg/L; and Etest, 4/16 mg/L. Etest produced 14.9% major/20.7% minor errors and VITEK(®)2 produced 3.4% major/17.2% minor errors. These data indicate that VITEK(®)2 may be more reliable than Etest for routine susceptibility testing of minocycline for A. baumannii isolates. As both VITEK(®)2 and Etest produced higher minocycline MICs compared with the reference method, BMD may be needed to validate the categorisation of carbapenem-resistant A. baumannii by these assays as minocycline non-susceptible.
authors.affiliation: Department of Microbiology, AHEPA University Hospital, Aristotle University of Thessaloniki, S. Kiriakidi 1, 546 36 Thessaloniki, Greece.
authors.forename: Pavlos
authors.initials: P
authors.lastname: Dimitriadis
authors.affiliation: Department of Microbiology, AHEPA University Hospital, Aristotle University of Thessaloniki, S. Kiriakidi 1, 546 36 Thessaloniki, Greece. Electronic address: protonotariou@gmail.com.
authors.forename: Efthymia
authors.initials: E
authors.lastname: Protonotariou
authors.affiliation: Department of Microbiology, AHEPA University Hospital, Aristotle University of Thessaloniki, S. Kiriakidi 1, 546 36 Thessaloniki, Greece.
authors.forename: Sotiris
authors.initials: S
authors.lastname: Varlamis
authors.affiliation: Department of Microbiology, AHEPA University Hospital, Aristotle University of Thessaloniki, S. Kiriakidi 1, 546 36 Thessaloniki, Greece.
authors.forename: Aggeliki
authors.initials: A
authors.lastname: Poulou
authors.affiliation: Department of Microbiology, AHEPA University Hospital, Aristotle University of Thessaloniki, S. Kiriakidi 1, 546 36 Thessaloniki, Greece.
authors.forename: Olga
authors.initials: O
authors.lastname: Vasilaki
authors.affiliation: First Internal Medicine Department, Infectious Diseases Unit, AHEPA University Hospital, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Simeon
authors.initials: S
authors.lastname: Metallidis
authors.affiliation: Department of Microbiology, Medical School, University of Athens, Athens, Greece.
authors.forename: Athanasios
authors.initials: A
authors.lastname: Tsakris
authors.affiliation: Department of Microbiology, Medical School, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Nikos
authors.initials: N
authors.lastname: Malisiovas
authors.affiliation: Department of Microbiology, AHEPA University Hospital, Aristotle University of Thessaloniki, S. Kiriakidi 1, 546 36 Thessaloniki, Greece.
authors.forename: Lemonia
authors.initials: L
authors.lastname: Skoura
authors.affiliation: Department of Microbiology, Medical School, University of Athens, Athens, Greece.
authors.forename: Spyros
authors.initials: S
authors.lastname: Pournaras
mesh_terms: D040981:Acinetobacter baumannii / Q000187:drug effects*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015780:Carbapenems / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods*; D008911:Minocycline / Q000494:pharmacology*; D018440:beta-Lactam Resistance
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems; D008911:Minocycline
keywords: Antibiotic susceptibility testing; Broth microdilution; Etest; Multidrug-resistant; VITEK(®)2