Research On Differentiation And Identification Systems Of Pathogens By FT-IR Combined With Chemometrics Methods

To establish effective, fast methods for classification, identification and detection of pathogenic bacteria is an important technical means to guarantee the hygiene and safety of food and human health. With the advancement of technology and interdisciplinary development, methods for classification, identification and detection of pathogenic bacteria are not limited to the methods of traditional morphological observation and biochemical reaction, many rapid and efficient methods have been developed, such as molecular biological methods, immunological methods, protein chip methods and biosensor methods, and so on.In this study, foodborne pathogenic bacteria were studyed by Fourier transform infrared spectroscopy (FT-IR) combined with chemomtrics methods. First, the factors affecting the differentiation and identification of bacteria by FT-IR were dicussed. Second, FT-IR fingerprint absorption spectra of many pathogenic bacteria was collected, and creating a standard spectral or derivatives library of bacteria. Finally, combined with chemometrics methods of hierarchical cluster analysis (HCA) and principal component analysis (PCA), FT-IR technology system for differentiation, identification and detection of pathogenic bacteria was established. Several important research results were abtained:1. The factors affecting the differentiation and identification of bacteria by FT-IR were demonstrated, and the conditions of sample preparation were determined. Taking Escherichia coli ATCC10536for example, the effects of concentration, culture time and inactivation on differentiation and identification of microorganisms by FT-IR spectroscopy were discussed, based on this above, the conditions of bacteria culture and sample preparation for FT-IR analysis were determined.2. Several standard FT-IR spectral and spectral derivatives libraries of bacteria at species level in genus were established by FT-IR combined with chemometrics methods (PCA and IICA) for the first time in domestic, including five species of bacteria in the Salmonella genus, three species of bacteria in the Listeria genus, two species of bacteira in the Staphylococcus genus and two species of bacteria in the Klebsiella genus. Further more, a systemic method for differentiating and identifying the bacteria above at species level was firstly established.3. A standard FT-IR spectral derivatives library of Salmonella parayphi at subspecies level was established by FT-IR combined with chemometrics methods (PCA and HCA) for the first time in domestic. Further more, a systemic method for differentiating and identifying the bacteria above at subspecies level was firstly established.4. Taking two strains of Escherichia coli for example, a systemic method for differentiating and identifying the bacteria at stain level by FT-IR combined with chemometrics methods (PCA and HCA).5. A standard FT-IR spectral derivatives library of13foodborne pathogenic bacteria was firstly established by FT-IR combined with chemometrics methods (PCA and HCA) for the first time in domestic. Further more, a systemic method for differentiating and identifying the bacteria above was firstly established.In this study, a technological system for differentiation, identification and detection of pathogenic bacteria by FT-IR combined with chemomtrics methods was established, not only provides important method basis to the wide application of FT-IR spectroscopy in differentiation, identification and detection of microorganisms, but provides a spectral database for the differentiation and identification of bacteria by FT-IR, which have stong popularization using value.. Further more, this study will have important significance to detect pathogens in food rapidly and effectively, improve safety and quality, and to promote the development of international trade.