Evaluation of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for identifying VIM- and SPM-type metallo-β-lactamase-producing Pseudomonas aeruginosa clinical isolates

BACKGROUND: Metallo-β-lactamase-producing Pseudomonas aeruginosa (MBL-PA) are important causative agents of nosocomial infections and are associated with significant mortality rates, especially in intensive care units. The timely detection and typing of these strains is essential for surveillance, outbreak prevention and antibiotic therapy optimization. In this study, fifteen VIM-type and fifteen SPM-type MBL-PA strains were selected as strains to establish MALDI-TOF MS SuperSpectra. METHODS: This study was undertaken to evaluate the utility of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) with the VITEK MS plus system in the detection of VIM- and SPM-type MBL-PA isolates. For each species, we increased the reference spectra, and then, a SuperSpectrum was created based on the selection of 39 specific masses. In a second step, we validated the SuperSpectra with the remaining 50 isolates (25 isolates of VIM-type and 25 isolates of SPM-type). RESULTS: Fifty MBL-PA strains were used as the validation strains, including twenty-five VIM-type and twenty-five SPM-type MBL-PA strains. Complete antimicrobial susceptibility testing and genotypic characterizations were performed for all isolates, which were subsequently identified using the newly created SuperSpectra databases following a previously reported method. The results showed that there was 92% agreement between the MBL profile generated by MALDI-TOF MS and that obtained using gene sequencing analysis methods. CONCLUSION: MALDI-TOF MS is a promising, rapid and economical method for detecting VIM- or SPM-type MBL-PA that could be successfully introduced into the routine diagnostic workflow of clinical microbiology laboratories.