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Analystrsc. li/ analyst ISSN 0003- 2654 Volume 149 Number 5 7 March 2024 Pages 1339- 1668 PAPER Xue Zou, Qiang Zhou, Chengyin Shen et al. Qualitative and quantitative rapid detection of VOCs diff erentially released by VAP- associated bacteria using PTR- MS and FGC- PTR- MS [Extracted from the article]

Laser-induced breakdown spectroscopy was used to investigate the elemental structure and discrimination of bacteria growth phases. Two bacterial specimens including Gram-negative E. coli and Gram-positive S. aureus, are selected at four different times during the growth phases with recorded optical densities of 0.4, 0.8, 1.2 (exponential growth phase), and 2.2 (stationary growth phase). By comparing the intensities of C, Ca, Na, Mg, K, O, H, and CN bonds in the LIBS fingerprint spectrum in the growth phases, different patterns of elemental composition for both bacteria of interest, including their structure. Multivariate linear discriminant analysis is applied to the "principal lines" and the "mixture of principal lines and their ratios". Analysis results depict different growth phases of bacteria are discriminated against each other during various classification accuracies ranging from 90% to 100%. Based on the results of the combination of LIBS and LDA, it is concluded that these bacteria can be classified during the growth process with high accuracy and precision. [ABSTRACT FROM AUTHOR]

Ventilator-associated pneumonia (VAP) is a prevalent disease caused by microbial infection, resulting in significant morbidity and mortality within the intensive care unit (ICU). The rapid and accurate identification of pathogenic bacteria causing VAP can assist clinicians in formulating timely treatment plans. In this study, we attempted to differentiate bacterial species in VAP by utilizing the volatile organic compounds (VOCs) released by pathogens. We cultured 6 common bacteria in VAP in vitro, including Acinetobacter baumannii, Enterobacter cloacae, Escherichia coli, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and Staphylococcus aureus, which covered most cases of VAP infection in clinic. After the VOCs released by bacteria were collected in sampling bags, they were quantitatively detected by a proton transfer reaction-mass spectrometry (PTR-MS), and the characteristic ions were qualitatively analyzed through a fast gas chromatography-proton transfer reaction-mass spectrometry (FGC-PTR-MS). After conducting principal component analysis (PCA) and analysis of similarities (ANOSIM), we discovered that the VOCs released by 6 bacteria exhibited differentiation following 3 h of quantitative cultivation in vitro. Additionally, we further investigated the variations in the types and concentrations of bacterial VOCs. The results showed that by utilizing the differences in types of VOCs, 6 bacteria could be classified into 5 sets, except for A. baumannii and E. cloacae which were indistinguishable. Furthermore, we observed significant variations in the concentration ratio of acetaldehyde and methyl mercaptan released by A. baumannii and E. cloacae. In conclusion, the VOCs released by bacteria could effectively differentiate the 6 pathogens commonly associated with VAP, which was expected to assist doctors in formulating treatment plans in time and improve the survival rate of patients. [ABSTRACT FROM AUTHOR]