Rapid Detection of High-Level Tigecycline Resistance in Tet(X)-Producing Escherichia coli and Acinetobacter spp. Based on MALDI-TOF MS

Abstract

The emergence and spread of the novel mobile Tet(X) tetracycline destructases confer high-level tigecycline and eravacycline resistance in E. coli and Acinetobacter spp. and pose serious threats to human and animal health. Therefore, a rapid and robust Tet(X) detection assay was urgently needed to monitor the dissemination of plasmid-mediated tigecycline-resistance. We developed a rapid and simple assay to detect Tet(X) producers in Gram-negative bacteria based on MALDI TOF MS. This MALDITet(X) test was based on the inactivation of tigecycline by a Tet(X)-producing strain after a 3 h incubation of bacterial cultures with tigecycline. Culture supernatants were analyzed using MALDI-TOF MS to identify peaks corresponding to tigecycline (586±0.2 m/z) and a tigecycline metabolite (602±0.2 m/z). The results were calculated using the MS ratio [metabolite/(metabolite + tigecycline) ]. The sensitivity of the MALDITet(X) test with all 216 test strains was 99.19% and specificity was 100%. The test can be completed within 3 h. Overall, the MALDITet(X) test is an accurate, rapid, cost-effective method for the detection of Tet(X) producing E. coli and Acinetobacter spp. by determining the unique peak of an oxygen-modified derivative of tigecycline.