Rapid Identification Of Different Serotypes Vibrio Parahaemolyticus By Matrix-Assisted Laser Desorption Ionization-Time Of Flight Mass Spectrometry

Objective:A method using matrix assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF-MS) to identify 29 different serotypes (O antigen) Vibrio parahaemolyticuse and 7 reference strains were evaluated. The accuracy, reproducibility and specificity of method were researched. Further more the correlation of serotype, tdh gene and clustering by MALDI-TOF-MS of 29 strains were investigated. Methods:The optimal conditions for MALDI-TOF-MS including pretreatment methods, culture media, incubated time, bacterial amounts, and ratio of matrix to sample were established at first according to the results of test accuracy and scores. The validation tests for accuracy, reproducibility and specific were performed then. The dendrogram of 29 strains by MALDI-TOF-MS identification results was also researched combined with the serotypes and detection of tdh gene by Real-time PCR. Results:After establishing the optimal conditions, the identification results by MALDI-TOF-MS were above 2.3 socre for 29 stains with very high accuracy, which were also consitent with biochemical results. Reproducibility of method was also ideal. Of 7 reference strains belonged to 5 genuses were identified correctly.29 strains contained 6 kinds of 0 antigens including 01,02,03,04,08 and O11. From the dendrogram,2 kinds of MALDI-TOF-MS types (M-type-Ⅰ, M-type-Ⅱ) were appeared at distance level of 1.1. The Real-time PCR results demonstrated 14 strains with tdh gene which were all M-type-Ⅱ, while the other without tdh gene were all M-type-Ⅰ.The 15 M-type-Ⅰ strains included 5 O2,5 O4,2 01,1 O3,1 O8, andl O11; the 14 M-type-Ⅱ strains included 7 O3,3 O4,2 O1,2 O2. Conclusion:MALDI-TOF-MS has ability to identify Vibrio parahaemolyticuse and 7 reference strains correctly and specifically in the study. Strains of 03 associates to TDH coded by tdh gene have tested. The strains with tdh gene are correalted with MALDI-TOF-MS types, which demonstrates initiatively that MALDI-TOF-MS could make efforts in tdh gene examination of Vibrio parahaemolyticuse. And the 03 serotype is related with M-type-Ⅱ, but the correlation of other serotypes with MALDI-TOF-MS types needs further study.