Gram negative rods blood culture12/3/2023 ![]() ![]() The present study aims to apply IMR-MS analysis of headspace gas VC composition to microorganism differentiation by using blood culture broth samples originating from an unselected patient population. Consequently, the next step is to analyse clinical specimens to test for the presence of microorganisms. Although these results are extremely promising it must be noted that they were obtained under tightly controlled conditions with regard to broth medium, incubation time and number of inoculated microorganisms. Applying these systems to in vitro analysis of bacterial samples headspace volatile compound composition makes microorganism differentiation possible even down to the species level. The advent of sophisticated methods such as chemical noses, direct mass spectrometry systems like ion–molecule reaction mass spectrometry (IMR-MS) or selected ion flow tube MS (SIFT-MS) nowadays allow for direct analyses of gaseous samples. However, the need for sample preparation prior to analysis still represents a drawback of this method. applied liquid chromatography and headspace solid phase micro extraction GC mass spectrometry for the detection of volatile fatty acids originating from anaerobes in clinical samples of blood cultures and bronchoalveolar lavage fluid. In contrast to the analysis of volatile fatty acids by liquid chromatography, where the solvent peak usually covers high volatility compounds, direct headspace gas chromatography (GC) allows for a more detailed investigation. The analysis of blood culture broth volatile fatty acid composition by gas–liquid chromatography for the detection of anaerobic bacteraemia has gained momentum back in the early 1980s. ![]() An ideal method for this purpose should be able to facilitate microorganism growth detection as well as Gram and species identification in a fully automated manner. Thus, there is an ongoing urgent search for rapid and reliable diagnostic methods allowing for the identification of the causative microorganisms. This limits microorganism identification and result communication to the clinician to standard working hours. However, subsequent procedures necessary for microorganism identification as Gram-staining, species identification by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) or biochemical methods and antibiotic susceptibility testing require staff presence. The first step in this process, namely the detection of microorganism growth in blood culture broth bottles, has achieved high reliability and works on a semi-automatic basis. Thus, fast identification of the causative organism is of highest priority as this allows for early adoption of antibiotic treatment. Although empiric antibiotic therapy is usually initiated prior to species identification in septic patients, inappropriate antibiotic therapy is present in up to 20 % of patients suffering from Gram-positive bacteraemia. In septic patients, about 50 % of microbial proven infections are bloodstream infections with Gram-positive bacteria. This already high mortality rate is further increased up to 55.2 % when infectious complications progress to the development of sepsis or severe sepsis, a condition found with a prevalence of 76–300 cases per 100,000 population per year in the United States, France, and Germany. The occurrence of infectious complications in critically ill patients significantly impacts patient outcome by increasing the mortality rate from 11 % in non-infected patients to 25 % in patients with infection. ![]()
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