Exploratory Study Of The Pathogen Detection By Terahertz And Raman Spectra

BackgroundIn the recent years,human infectious diseases caused by kinds of pathogens has been increasing.Meanwhile,as the abuse of antibiotics,drug resistant strains also gradually increased.The identification of the pathogen and disease diagnosis brings new challenges.Therefore,the early,rapid and accurate identification of pathogens can correctly guide the rational use of drugs and effectively reduce the harm of infectious diseases to human health.At present,the pathogen detection mainly depends on the bacterial culture and traditional identification methods.However,due to the complicated operation and long test cycle,these traditional methods cannot satisfy the actual needs of clinical rapid diagnosis.With the development of physical techniques,terahertz spectrum and Raman spectra that have emerged in recent years are being gradually applied to the detection of pathogens.Terahertz spectrum and Raman spectra are the same molecular vibration spectra,and the identification of microorganisms by spectral "fingerprint characteristics" has advantages such as fast,unmarked and low cost.This study focuses on three kinds of bacillus and three kinds of candida as the model organism,using terahertz spectroscopy and Raman spectroscopy to detect the potential of unmarked spectroscopy for pathogen detection.AimThis topic in three kinds of bacillus,three kinds of candida as a model organism,which use THz-TDS(THz time-domain spectroscopy)instrument and micro Raman spectrometer to detect,two spectrum characteristics analysis,from theory and experiment on terahertz technology and Raman technology may be used for rapid detection of pathogens.Methods1.Collected three kinds of bacillus,made of freeze-dried powder,and mixed with PE powder in different quality proportions,and then pressed into a round film,which was tested in transmission mode using the terahertz time threshold spectrometer,to investigate the ability of THz technology to detect bacillus in powder samples2.The test pool was made with a polyethylene gasket and 3M adhesive paper.After the cultivation,three bacillus strains were found on the test pool,which was tested in transmission mode using the terahertz time threshold spectrometer,to explore the difference of THz spectrum of different pathogens in the state of colony.3.Collected three kinds of candida colony,made of freeze-dried powder,and pressed into the disc with the infrared press,and tested in the transmission mode using the terahertz time threshold spectrometer.4.After the solid cultivation of three candida bacteria,the scraping colony was taken on the self-controlled test pool,which was detected in transmission mode using the terahertz time threshold spectrometer.5.The water content of the samples was calculated and compared with THz spectrum.6.After the solid culture of three kinds of bacillus,it was selected to take the colony on the fluorinated magnesium wafers,and the microscopic Raman spectrometer was used for the detection,and the measurement results were analyzed by the principal component analysis(PCA),to study the Raman spectra was used to distinguish the feasibility of different bacillus.7.After the solid culture of three kinds of candida,they were selected to take the colony on the fluorinated magnesium wafers,and the microscopic Raman spectrometer was used for the detection,and the measurement results were analyzed by the principal component analysis(PCA).Results1.By the difference of absorption coefficient,terahertz wave can distinguish the different content of bacteria.Three bacillus pure bacteria producing absorption coefficient of the compressor from large to small followed by: bacillus subtilis > bacillus cereus > bacillus thuringiensis,THz wave can effectively identify three bacillus producing.2.Three kinds of bacillus colony in the terahertz band absorption increased with the increase of frequency,absorption coefficient from large to small,in order: bacillus subtilis > bacillus thuringiensis > bacillus cereus,by differences in absorption coefficient,THz wave can identify three kinds of bacillus.Moreover,the absorption of bacteria in the colony state is far greater than that in the frozen dry state,and the terahertz wave is an effective means to identify the state of bacteria.3 Three candida in the terahertz band of absorption increased with the increase of frequency,producing,in absorption coefficient from large to small,in order : candida albicans > candida glabrata > candida tropical;colony,in absorption coefficient from large to small,in order : candida albicans > candida tropical > candida glabrata,THz wave can identify three kinds of candida.4.Bacteria water content test result is: bacillus subtilis > bacillus thuringiensis > bacillus cereus,fungus water content test result is: candida albicans > candida tropical > candida glabrata,and regardless of bacteria,fungi,its water content is consistent with the size of the absorption coefficient of the colony.5.Three kinds of micro Raman spectrum line difference between bacillus,abundant spectral information,characteristic peak clear and sharp,combined with principal component analysis of spectral data after smoothing can effectively identify three types of bacillus.6.Three kinds of candida Raman spectral line profile approximation degree is high,it is difficult to distinguish with the naked eye,to smooth the spectral data processing after principal component analysis showed that the three kinds of candida 3 d scatter plot is part of the intersection,it is difficult to completely will identify three.Conclusion1.Terahertz waves can effectively identify the different states of pathogens,the order of the pathogen's water content is in the same order as that of the terahertz absorption coefficient of the colony.And whether it is freeze-dried or colony,terahertz waves can identify different pathogens.Terahertz waves can distinguish the different levels of bacterial freeze powder and show the potential for quantitative detection.2.Since water is absorbed strongly in the terahertz band,we speculate that terahertz waves can be identified by the differences in the endogenous water of the components and structures that are similar to each other.3.The Raman spectrum detecting pathogens,complex and abundant spectral information,characteristic peak clear,sharp,for related pathogens,can be directly identified according to the characteristic peak location difference;for the same species of bacteria and fungi,it is necessary to analyze the chemical metering method.4.Although no obvious characteristics of terahertz spectrum peak,but the test results can be directly,without the stoichiometric method,especially in the fungus on the detection of Raman spectroscopy with strong fluorescence interference not effectively identify.