Development of Tigecycline Resistance in Carbapenemase-Producing Klebsiella pneumoniae Sequence Type 147 via AcrAB Overproduction Mediated by Replacement of the ramA Promoter

BACKGROUND: 2297, isolated from a patient treated with tigecycline for pneumonia, developed tigecycline resistance, in contrast to carbapenem-resistant isolate 1215, which was collected four months prior to the 2297 isolate. Mechanisms underlying tigecycline resistance were elucidated for the clinical isolates. METHODS: were determined by reverse-transcription quantitative PCR. RESULTS: gene promoter replacement resulting in stronger activation of the gene. CONCLUSIONS: isolate developed tigecycline resistance during tigecycline treatment. It was related to the overexpression of the AcrAB resistance-nodulation-cell division efflux system due to promoter replacement.