Discrimination Of Several Foodborne Bacteria Using Fourier Transform-Infrared Spectroscopy

Foodborne pathogens can cause bacterial food poisoning by meat, vegetables, aquatic products, dairy products and other. It is harmful to human health and an important threat to public security. Therefore, detection of pathogen contamination in food is very important. Now, the detection and identification of foodborne pathogens in food has become an indispensable key to the industry.There are many ways for the detection of foodborne pathogens. The traditional methods are based on physiological and biochemical identification.but this method is time-consuming, more complicated experiment and it is difficult to accurate identification of similar pathongens.Some methods can identification of pathogens with with high specificity, sensitivity and accuracy, such as molecular biology, immunology and genetics method. But these methods require high cost and complex operation,it is difficult to widely used in routine laboratories.In this study,we collected infrared spectroscopy of cells and near infrared spectroscopy metabolites from different foodborne pathogens. We used statistical and chemometric methods for analyzed the data . We want to establish a rapid method for detection of foodborne pathogens.The main findings of this study are as follows:1.Fourier transform infrared(FT-IR) spectra(4000-400cm^-1) were obtained form Escherichia coli O157:H7, Salmonella enteritidis, Staphylococcus aureus and Listeria monocytogenes.The FT-IR absorbance of four bacterial strains for some different functional groups may be correlated to major bacterial cell constituents, including protein, fat , sugar, nucleic acid etc. The absorption peaks are mainly due to -OH,-CH3, CH2, C = O, NH, CN, C = O, P-O deformation-,bending- and ring-vibrations.2.Strain-specific absorbance peaks were absorbance between 1500 and 800cm^-1.The range can be considered as the"fingerprint region"of Escherichia coli O157:H7, Salmonella enteritidis, Staphylococcus aureus and Listeria monocytogenes. 3.The spectra of Escherichia coli O157:H7, Salmonella enteritidis, Staphylococcus aureus and Listeria monocytogenes are analysed through first derivative transformation between 800cm^-1 and 1500cm^-1 in order to compare the similarities and differences between spectra of the four chosen bacteria. Results show that pearson correlation coefficient analysis ,principal component analysis (PCA) and cluster analysis(CA) revealed clear segregations between four different bacterial strains.4.Escherichia coli O157:H7, Salmonella enteritidis, Staphylococcus aureus and Listeria monocytogenes was cultured in different temperature(30℃, 37℃)and different medium(Brain Heart Infusion,Luria-Bertani,Nutrient Broth,Tryptic Soy Broth). Results show that fingerprint region of parallel spectral have a good reproducibility. Moreover, the four strains have stable cellulat constituents in different culture conditions, the absorption peaks of fingerprint region is very similar.5. Distinguishing of four pathogens is different in different culture conditions.The infrared spectra of Gram-negative bacteria and Gram-positive bacteria have some different. The ability of distinguishing Gram-negative bacteria (Escherichia coli O157:H7, Salmonella enteritidis,) is weaker than distinguishing Gram-positive bacteria (Staphylococcus aureus ,Listeria monocytogenes).6.A study based on FT-IR spectroscopy combined with D-values and cluster analysis was designed to differentiate 10 Listeria monocytogenes strains. Results show that using infrared spectroscopy in some extent could show serotypes characteristic of strain , the serotypethe of Listeria monocytogenes strains is more similar, its refers to the infrared spectrum similar degree is higher.7.The Ultraviolet Absorption Spectrum and Near Infrared Spectroscopy(NIR) of different bacteria metabolites has been collected in this study.The result show that Ultraviolet Absorption Spectrum of bacteria metabolites does not have fingerprint characteristics. Principal component analysis (PCA) with NIR spectroscopy method revealed clear segregations between Escherichia coli O157:H7, Salmonella Enteritidis, Staphylococcus aureus of different Generic bacteria and Pseudomonas fragi, Pseudomonas fluorescens, Pseudomonas putida of same generic, different Species bacteria. However,seven different Strains of Vibrio parahaemolyticus were unable to be distinguished.