Comparison of Conventional Methods, Automated Systems, and DNA Sequence Analysis Methods in the Identification of and Bacteria Isolated from Blood and Catheter Culture Samples.

The aim of this study is to compare different methods due to the difficulties in identifying coryneform bacteria to species level and to determine antibiotic resistance profiles. Isolates identified as (:45) by VITEK 2 Compact and (:1) by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), isolated from blood and catheter cultures between 2015 and 2017 were included in the study. For identification of the isolates, conventional tests and 16S rDNA sequence analysis were performed. Antibiotic susceptibilities of the isolates were determined by Etest. The isolates identified as with VITEK 2 Compact could not be identified by MALDI-TOF MS and described as / spp. by 16S rDNA sequence analysis. One isolate identified as by MALDI-TOF MS could not be identified with VITEK 2 Compact and described as by 16S rDNA sequence analysis and conventional methods. All isolates (:45) described as / spp. by 16S rDNA sequence analysis were identified as subsp. with conventional methods. All 45 isolates identified as subsp. were resistant to penicillin, erythromycin, and clindamycin and were susceptible to vancomycin and daptomycin, whereas 31 (69%) were resistant to trimethoprim-sulfamethoxazole (TMP-SXT). The isolate identified as was susceptible to penicillin, vancomycin, daptomycin, and TMP-SXT; it was resistant to erythromycin and clindamycin. In this study, we reported 45 isolates misidentified as in routine laboratory processes. To our knowledge, this is the first study to include the highest number of blood isolates.