Detection of CTX-M- Producing Enterobacteriaceae using MALDI-TOF.

FIGUEROA ESPINOSA ROQUE A; GHIGLIONE BÁRBARA; RUMI, VALERIA; BARBERIS CLAUDIA; VAY CARLOS; DI CONZA JOSÉ; GUTKIND GABRIEL

Atlanta

Congreso; ASM MICROBE 2018; 2018

ASM

Background: The CTX-M enzymes are the most prevalent extended-spectrum β-lactamases (ESBL), both in nosocomial and in community settings. Fast, easy to perform sensitive and specific methods for ESBLs detection are needed to avoid treatment failure and prevent dissemination. MALDI-TOF mass spectrometry is frequently used as a routine bacterial identification tool to categorize bacterial species. Direct detection of ß-lactamases production in Enterobacteriaceae by MALDI-TOF is another important diagnostic challenge for clinical microbiology lab. In this study, an easy, fast and direct MALDI-TOF MS protocol was designed to detect CTX-M-producing Enterobacteriaceae. Materials/methods: 49 clinical isolates of Escherichia coli (15), Salmonella enterica (15), Klebsiella pneumoniae (8), Serratia marcescens (8) and Proteus mirabilis (3) were included in this study. Susceptibility tests were performed according to CLSI. Isolates were analyzed by PCR and sequencing, and grouped according to the CTX-M variant. Subsequently, CTX-M- detection was carried out by MALDI-TOF (Bruker) after proteins extraction with organic solvents. MALDI-TOF spectra were recorded by MALDI Biotyper system and analyzed using ClinProTool software (Bruker). E. coli transformants producing CTX-M-2, CTX-M-15 and CTX-M-9 enzymes were used as positive controls and isolates lacking any blaCTX-M- as negative controls. Results: Operating at a mass range of 17,000 to 50,000 Da, three peaks at approximately m/z 28,287, 28,093 and 27,950 Da were detected by MALDI-TOF and they were correlated with the mature protein of CTX-M-2, CTX-M-15 and CTX-M-14, respectively. After statistical analysis of peaks, two groups of isolates could be distinguished: the CTX-M-producing enterobacteria (28) (clinical isolates and transformants) and non-CTX-M-producing enterobacteria (24) (including susceptible strains and CMY-2, KPC-2 and TEM producers). Furthermore, the 25 CTX-M-producing isolates were correctly classified into CTX-M-1 (6), CTX-M-2 (15) and CTX-M-9 (7) groups.Conclusions: Our MALDI-TOF assay was able to identify the most frequent CTX-M ß-lactamase groups reported in Argentina in different enterobacterial species. Considering that our results could be obtained as early as bacterial identification time, and together with our previous findings on other prevalent beta-lactamases, implementing a database for their detection at that time, it may have deep impact on resistance detection and effective treatment implementation.