False non-susceptible results of tigecycline susceptibility testing against Enterobacteriaceae by an automated system: a multicentre study.

False non-susceptible results of tigecycline susceptibility testing against Enterobacteriaceae by an automated system: a multicentre study. J Med Microbiol. 2016 May 17; Authors: Idelevich EA, Büsing M, Mischnik A, Kaase M, Bekeredjian-Ding I, Becker K Abstract Tigecycline antimicrobial susceptibility testing (AST) is challenging and an overestimation of tigecycline minimum inhibitory concentrations (MICs) by the Vitek 2 system has previously been reported. We therefore aimed to determine the rate of Vitek 2 false non-susceptible tigecycline results for Enterobacteriaceae and to find a practical AST method, which provides accurate finding. Enterobacterial isolates tested non-susceptible to tigecycline by Vitek 2 at four university hospitals in Germany (n=296) were sent to a coordinating centre. Isolates confirmed as non-susceptible by triplicate Vitek 2 testing were subjected to a comparative AST by automated AST systems Vitek 2, BD Phoenix, MicroScan WalkAway, as well as Etest and disk diffusion, with broth microdilution (BMD) used as reference method. A subset of 61 isolates was used to investigate the differences between different gradient diffusion tests (Etest, M.I.C.Evaluator Strips, MIC Test Strips), Mueller-Hinton agar from different manufacturers (BD, bioMérieux, Bio-Rad, Oxoid, Merck), and different Vitek 2 AST cards (N214, N232, N223). Of 241 isolates confirmed as non-susceptible by Vitek 2, 40.2% and 53.3% were suscepti...
Source: Journal of Medical Microbiology - Category: Microbiology Authors: Tags: J Med Microbiol Source Type: research