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We developed a novel pretreatment procedure that destroys the plasma membrane of platelets but not the bacterial cell wall, allowing viable bacterial ATP in septic blood samples to be measured with minimal human-derived ATP background. After the pretreatment procedure with this approach, the plasma membranes of platelets are completely destroyed, and human-derived ATP background is dramatically decreased. To test the recovery rates of viable bacteria after pretreatment, we evaluated 19 bacterial genera. As a result, the mean recovery rates of viable bacteria were 93.6% using ATP bioluminescence and 71.9% using the colony-counting method. Finally, using the pretreatment procedure and ATP bioluminescence, rapid antimicrobial susceptibility testing of pathogenic bacteria in septic blood samples was performed, and LVFX resistance was determined within 6.5 h of whole blood collection. This novel pretreatment procedure will open up new possibilities concerning the utility of ATP bioluminescence in medicine.

Antimicrobial activity is tested when developing disinfectants, pharmaceutical products, cosmetics, and many other consumer products. However, the plate count method, the conventional way to count the number of microorganisms, needs several days of culture. Consequently, a means of rapid microbial detection is strongly desired to replace this method. We have already developed a rapid and sensitive microbial adenosine triphosphate (ATP) detection system utilizing ATP bioluminescence, which can quantify microbial ATP within 1 h. To apply this technique to antibacterial activity tests, the ATP method should be proved equal or superior to the conventional method. In this study, we conducted disinfectant activity tests comparing the ATP method and the plate count method, using polyhexamethylene biguanide (PHMB) in different concentrations (0-10 ppm) as a model disinfectant against Staphylococcus aureus and Aspergillus brasiliensis. We found that the log reduction of intracellular ATP had a positive correlation with the log reduction of the plate count. Moreover, the ATP method was able to distinguish different conditions of injured microbial cells that were observed using scanning electron microscopy, whereas colony counting detects only culturable cells. The ATP method is thus a rapid and useful alternative to the conventional method in the field of antimicrobial activity testing.

A detection technique for ion suppression in liquid chromatography/mass spectrometry (LC/MS) was developed by adding a probe to an LC mobile phase at a certain concentration. The probe is so hydrophilic that it is not adsorbed in a reversed-phase nanoflow LC column, and, furthermore, has an isoelectric point of about 3, which is lower than that for most peptides and is close to the pH of the mobile phase. The intensity of the protonated probe molecule decreases much more than that of other peptides when ion suppression occurs. Thus, the occurrence of the ion suppression is detected by a decrease in the mass chromatogram for the protonated probe molecule, and the decrease ratio is higher than that for other ions.

It is found that helical structures can be formed by a simple achiral fatty acid, oleic acid, in the pH range of 8.0–8.1 at room temperature. Moreover, we succeeded in the first observation of spon...

A giant vesicle composed of an amphiphile with a reactive site exhibited a morphological change when the vesicular amphiphile reacts with an added amphiphilic reaction-partner within its membrane.

An analytical system using gas chromatography/atmospheric pressure chemical ionization-mass spectrometry (GC/APCI-MS) was suitably set up for the analysis of volatile metabolites from cultured bacteria. The developed system was proved to have high sensitivity: the detection limit for a standard sample of indole was 17 pg (33 ppt (parts per trillion) for 100 mL gas sample). The system was extensively applied to rapid analysis of volatile metabolites from different bacteria: Escherichia coli, Streptococcus pneumoniae, and two strains of Staphylococcus aureus. A total of 156 metabolite peaks were peculiar to one of the species among 163 metabolite peaks found for all of the bacteria. The experimental results suggest that the GC/APCI-MS has the potential to distinguish bacterial pathogens rapidly by detecting bacterial volatile metabolites.