关键词: 基质辅助激光解析/电离飞行时间质谱, 单增李斯特菌, 血清型

Abstract: Listeria monocytogenes is an important zoonotic pathogenic bacteria. The traditional serological identification method is time consuming and cumbersome to operate, and current multiplex polymerase chain reaction (PCR) methods cannot accurately determine its specific serotype. Based on the quick, accurate and high-flux, etc. characteristics of matrix-assisted laser desorption/ionization-tandem time of flight mass spectrometry (MALDI-TOF/TOF), this paper established an identification method for 4 serotypes of L. monocytogenes, so as to distinguish the L. monocytogenes in food sample in a large quantity with high speed. The isolated and standard strains of 4 serotypes of L. monocytogenes were detected under the optimized MALDI-TOF/TOF condition, and the characterisic peaks of mass spectrum of 4 L. monocytogenes serotypes were discovered. This paper selected the optimal support vector machine (SVM) algorithm and established discriminant model of serotype difference based on 1/2a, 1/2b, 1/2c and 4b, and identified 4 L. monocytogenes serotypes by this model. Thus, a fast MALDI-TOF/TOF identification method for 4 L. monocytogenes serotypes was preliminarily established. Taking these 4 standard strains as positive control and 144 strains isolated from food for detect objects, this paper identified 4 L. monocytogenes serotypes by this method, and the accuracy rates of 1/2a, 1/2b, 1/2c and 4b reached 92.7%, 90.3%, 100% and 100%, respectively. The accuracy rate of multiplex PCR were 71.4%, 87.0%, 96.2% and 95.0%, respectively. Visibly, the established MALDI-TOF/TOF typing method could be used for rapid identification of 4 L. monocytogenes serotypes. Compared with multiplex PCR method, this method had the characteristics of quick, high-flux, good reproducibility, etc., so it could be used for fast serotype identification of L. monocytogenes in food.

Key words: matrix-assisted laser desorption/ionization time of flight mass spectrometry, Listeria monocytogenes, serotype