Prediction of mcr-1-mediated colistin resistance in Escherichia coli by a biomarker detection using MALDI-TOF MS

FIGUEROA ESPINOSA ROQUE A; COSTA, AGUSTINA; GONZALES EDGAR; VAY CARLOS; GUTKIND GABRIEL; DI CONZA JOSÉ

Chicago

Congreso; ASM Microbe 2020; 2020

Rapid typing methods for colistin resistance detection are needed to guide proper treatment and prevent potential dissemination events; therefore possible biomarkers have been sought for early detection of mcr-1 mediated colistin resistance, using MALDI-TOF MS through visual analysis of the mass spectra obtained during identification (ID) procedure.Protein spectra of 95 E. coli clinical human isolates previously characterized: 25 mcr-1-producing isolates and 70 colistin-susceptible isolates (blaKPC-2 positive (3), different ESBL producers (50) and miscellaneous (with other resistance markers) (17) were analized. Two transconjugant mcr-1-producing E. coli strains (and recipients) were used as controls. Every isolate was processed simultaneously directly from colony and after proteins extraction with organic solvents by MALDI Biotyper system (Bruker, Germany) at 2.000-20.000 Da with HCCA matrix. Peak detection was made by visual analysis of ID spectra with flexAnalysis and ClinProTools softwares to identify potential resistance biomarkers. Sequence analysis of 10 local plasmids carrying mcr-1 was performed using on-line bioinformatic tools.After visual comparison of mass spectra obtained from control strains after protein extraction, a ~6.650±5 Da peak was identified only in the transconjugants. When wild-type isolates were challenged, this peak was strongly detected in MCR-1-producing E. coli (the area under the ROC curve was 0.99). Using the protein extraction method, sensitivity (Se) was 100% (CI95: [86%; 100%]) and specificity (Sp) 100% (CI95: [95%; 100%]); when colonies were analyzed directly, Se was only 86% (CI95: [64%; 95%]) and Sp 100% (CI95: [95%; 100%]). After plasmid bioinformatic comparison, we found a conserved gene (HicA) that codifies the toxin of a HicAB toxin-antitoxin system (theoretical M.W. 6.648 Da) that could correspond to the detected peak. Presence of HicA was verified by PCR, with a 100% concordance in all MCR-1-producing isolates where the ~6,650 Da peak was observed.Visualization of this ~6,650 Da peak in the ID spectrum generated by MALDI Biotyper software could be a fast method to predict mcr-1-mediated colisitin resistance in endemic E. coli isolates, without employing additional reagents or procedures than those used for ID. Detection of 6,650 Da-biomarker peak could be easily incorporated into daily practice as a predictor of colistin resistance, as far as plasmid platforms are conserved in different regions