Infrared absorptions as indicators for Pseudomonas aeruginosa and Acinetobacter baumannii

There is clinical demand for simple and contact-free diagnosis techniques in medical practice. This study shows that the infrared absorptions of volatile metabolites can be used to distinguish between the air around Pseudomonas aeruginosa, Acinetobacter baumannii, other bacteria, and normal room air. Gas samples were collected from the air surrounding single and mixed laboratory cultures, and preliminary data on human breath samples are also presented. The infrared spectra of a variety of gasses are measured with a high resolution of 0.5 cm-1 to obtain information about the wavenumber position of the key bands. Hence, it is not necessary to specify the molecular species of biomarkers. This work also shows that discrimination rates can be improved by observing additional infrared absorptions caused by different characteristic volatile molecules. The significance of this work is that the specific wavenumber positions of the key bands that allow the application of infrared lasers are provided. As a result, it is considered that Pseudomonas aeruginosa and Acinetobacter baumannii can be monitored more sensitively and easily. With further research and development, this simple approach could be used in future applications to identify infections in healthcare settings.


Introduction 34
Biomarkers are characteristic molecules produced by biological processes. The biomarkers found 35 in various gas samples have been examined by using gas chromatography-mass spectrometry (GCMS), and they are of interest for non-invasive diagnosis and healthcare applications [1][2][3][4][5]. In addition,

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To apply an infrared laser, it is necessary to adjust the oscillation wavenumber (the reciprocal of 41 the wavelength) to a specific value. A molecule produces many peaks, but the wavenumber indicates 42 the position of one strong peak on the horizontal axis of the infrared spectrum. Infrared lasers can be 43 used to detect changes in the concentration (partial pressure) of some target volatile biomarkers. In 44 particular, it has been shown that changes in the concentration of ethane [13] and ethanol [14] can be 45 detected with ultra-high sensitivity, in addition to the molecules CO, CO 2 , NO, and NO 2 . the infrared absorption peaks it is possible to identify the key band, the infrared absorption peak that absorption peaks in the region of 2000-2300 cm -1 . However, specifying the molecular structure of the 74 key VOC does not automatically mean it can be found because the key band must appear in the 75 "window" region so that the intensity can be read. The condition is confirmed only by comparison 76 with many infrared spectra of other gas samples.

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The next condition is whether the accuracy of the key-band position is in a range that facilitates the

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The gas in each bag was introduced into a gas cell (light path length 10 m) installed in an FTIR 133 spectrometer (Bruker VERTEX 70). Overall, 365 infrared (IR) spectra for the various gas samples in 134 Table 1 were measured in the range of 550-7500 cm -1 at atmospheric pressure with a resolution of 0.5 135 cm -1 .

Data analysis
137 Microsoft EXCEL was used for data processing and analysis. The details of the infrared absorption 138 peaks that appeared in the IR spectra were obtained and the peak intensities were measured and 139 compared. The peak intensity was calculated by subtracting the absorbance at the base point from that 172 Fig 2 shows Table 1.

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The values on the x and y axes reflect the infrared absorption peaks of the VMs specific to Pa.

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According to Lambert-Beer's law, the infrared absorption intensity indicated by absorbance is Application and data processing 251 Infrared lasers can be applied to detect the key VMs of Pa and Ab using three steps:

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(1) fine adjustments of the oscillation wavenumbers at the absorption peak (P) and base point (B);

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(2) conversions of the outputs from the light receiving parts in the infrared laser system to values

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(3) a discrimination program with consideration of the optical path length.

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It is worth noting that the gas samples in this experiment were under atmospheric pressure. This 257 work assumes that the atmospheric pressure during any application is the same as at the experiment 258 site.

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To replace the absorbance (A) obtained by FTIR spectroscopy with the intensity (I) obtained from  299 baumannii with high sensitivity.

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The next step involves fine-tuning of the oscillating wavenumber of the infrared laser around the 301 values reported in this study. The fine adjustment will be performed by finding a wavenumber position 302 with the best discrimination rate in consideration of the line width of the infrared laser. As the result, 303 comparisons with traditional methods will be possible.

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Applications for human health care will require the accumulation of more detailed information in 305 the infrared spectrum for gas samples under more diverse conditions. We believe that information 306 related to human health, which is statistically significant and has a high discrimination rate, can be 307 extracted by enhancement of the database. At present, we are working with hospitals to accumulate