Direct detection of CTX-M-2 and KPC-2 in Serratia marcescens using MALDI-TOF

FIGUEROA-ESPINOSA, ROQUE; GHIGLIONE BÁRBARA; CEJAS DANIELA; BARBERIS CLAUDIA; VAY CARLOS; GUTKIND, GABRIEL; DI CONZA JOSÉ

Madrid

Congreso; 28 th ECCMID; 2018

Background: Serratia marcescens is an opportunistic and nosocomial pathogen, which can cause a wide range of infections. S. marcescens has been associated with the acquisition of CTX-M and KPC, the most prevalent extended spectrum ß-lactamase (ESBL) and class A carbapenemase in Enterobacteriaceae, worldwide. Rapid typing methods for ESBL and carbapenemases are desirable in order to avoid treatment failure and prevent dissemination events. At this time, MALDI-TOF mass spectrometry is used in microbiological laboratories for species identification. Detection of ß-lactamases using the analysis of ß-lactam hydrolysis products by MALDI-TOF is reliable but uncomfortable. In this study, an easy, fast and direct MALDI-TOF MS protocol was applied to find distinctive protein profiles in CTX-M-2 and KPC-2 producing S. marcescens.Materials/methods: 20 clinical isolates of S. marcences were included in this study. Susceptibility tests were performed according to CLSI. Isolates were analyzed by PCR and grouped according to the presence of ß-lactamase genes. The detection of CTX-M-2 and KPC-2 ß-lactamases was carried out by MALDI-TOF (Bruker) after extraction of proteins with organic solvents. MALDI-TOF spectra were recorded by MALDI Biotyper system and analyzed using ClinProTool software (Bruker). E. coli transconjugants producing CTX-M-2 and KPC-2 were used as controls.Results: Three isolates were categorized as KPC-2 producers and four as CTX-M-2 producers. The MALDI-TOF test was able to differentiate the presence of both ß-lactamases in these isolates. A distinctive peak at m/z ~28,477 Da and other peak at m/z of ~28,287 Da were correlated with the mature protein of KPC-2 and CTX-M-2, respectively. To highlight, two strains that possessed both enzymes simultaneously, were successfully discriminated and detected by MALDI-TOF. Both characteristic peaks were absent in the 15 S. marcescens isolates lacking CTX-M-2 and/or KPC-2.Conclusions: Although our results are preliminary, MALDI-TOF spectra contain information that allows distinguishing CTX-M-2 or KPC-2 producing S. marcescens on a rapid and reliable way. The time required for this test is substantially less than that needed for hydrolysis products. Overall, if the method can be extended to other species, or even other resistance markers, may prove a significant improvement in lab abilities for their detection with extensive clinical implications.