Abstract:

Objective To screen and verify the specific peak of KPC-2 producing Klebsiella pneumoniae ST11 by matrix-assisted laser desorption ionization time-of-flight mass spectrometry（MALDI-TOF MS）,and to establish a rapid method for the detection of Klebsiella pneumoniae. Methods A total of 118 isolates of Klebsiella pneumoniae which had been confirmed by carbapenemase gene detection and classified by multilocus sequence typing（MLST） were collected as specific peak screening group,67 isolates of them were KPC-2 producing Klebsiella pneumoniae ST11,and 51 isolates of them were non-KPC-2 producing Klebsiella pneumoniae ST11. Clinpro Tools 3.0 software and Flex analysis 3.0 profile analysis software were used to screen the specific peak. Other 89 isolates of Klebsiella pneumoniae which had detected by carbapenemase gene detection and classified by MLST were selected as specific peak verifying group. Mass spectra were acquired strictly according to experimental conditions,and the specificity and repeatability of specific peak were detected. Finally,95 isolates of Klebsiella pneumoniae and their mass spectra were collected. These isolates were distinguished directly by the specific peak. Meanwhile,carbapenemase gene detection and MLST were performed for these isolates in order to evaluate the efficiency of specific peak. Results The specific peak of KPC-2 producing Klebsiella pneumoniae ST11 was m/z 4 521. In the experimental conditions,the specificity and sensitivity were 98.1% and 97.3%,and the repeatability of specific peak was 97.4%. In the clinical conditions,using mass spectra,the specificity and sensitivity were 95.2% and 96.9%,respectively. Conclusions The specific peak m/z 4 521 on MALDI-TOF MS is the specific peak of KPC-2 producing Klebsiella pneumoniae ST11. KPC-2 producing Klebsiella pneumoniae ST11 can be detected directly according to the specific peak with high specificity and sensitivity,which can provide a reference for clinical treatment and nosocomial infection control rapidly and accurately.

Key words: Matrix-assisted laser desorption ionization time-of-flight mass spectrometry, Specific peak, Klebsiella pneumoniae, Carbapenemase, Multilocus sequence typing