Detection index application for β-lactamases determination in Enterobacteriaceae with MALDI-TOF MS.

FIGUEROA ESPINOSA ROQUE A; COSTA, AGUSTINA; BARBERIS CLAUDIA; VAY CARLOS; GUTKIND GABRIEL; DI CONZA JOSÉ

San Francisco

Congreso; ASM MICROBE 2019; 2019

ASM

MALDI-TOF MS technology is an innovative alternative for resistance detection, including direct detection of resistance conferring enzymes. CTX-M-, KPC- and CMY- β-lactamases are representatives of prevalent resistance mechanisms in Gram negative bacilli worldwide. In order to discriminate between β-lactamases producing and non-producing isolates, we propose to make a relative lecture to a reference strain at the corresponding spectral positions. We analyzed 60 β-lactamase producing isolates (20 CTX-M, 20 KPC-2, 20 CMY-2) including different Enterobacteriaceae species (25 K. pneumoniae, 23 E. coli, 4 E. cloacae, 3 S. marcescens, 3 S. Heindelberg, 1 C. braakii, 1 P. mirabilis). Negative controls included 25 non-KPC-2 producing isolates, 25 non-CMY-2 producing isolates, 30 non-CTX-M producing isolates. After a protein extraction protocol from colonies, and mature protein peak detection for each β-lactamase (KPC-2, CMY-2, CTX-M-group1 [G1], CTX-M-group2 [G2], CTX-M-group9 [G9]) with MALDI-TOF MS, we analyzed raw spectra to calculate the detection index (DI), considering the peak intensity (PI) as follows: DI = [PIβ-lactamase mean for each clinical isolate/PI mean of 31 spectra of E. coli ATCC 25922]. Data were analyzed with Mann-Whitney test (GraphPad Prism Vs 5). Statistical analysis showed a p-value