Direct Molecular Characterization of Bacteria From Tracheal and Urine Samples in Patients Hospitalized at the Intensive Care Units at the University Hospital of Basel and at the REHAB Basel

Investigators goal is to determine major bacterial activities and properties in the infected patient as a basis for more targeted, efficient antimicrobial discovery. Investigators will determine the abundance of dozens to hundreds of pathogen proteins in the samples and in in vitro cultures of the same pathogen strains using cutting-edge ultra-sensitive proteomics approaches (Parallel reaction Monitoring (PRM), Sequential Windowed Acquisition of All Theoretical Fragment Ion Mass Spectra (SWATH-MS). Data will be analyzed using dedicated mass spectrometry and proteomics packages using parametric and non-parametric statistics (false discovery rate determination based on decoy databases; t-tests of log-transformed abundance data with Benjamin-Hochberg corrections for multiple testing, normal distribution of the data will be evaluated by Kolmogorov-Smirnov test).

Based on experience from in vitro and animal infection experiments, a sample size of 10 can reveal 2fold differences in protein abundance among 500 top proteins at a significance of α = 0.05 and a power of β = 0.8 (after correction for multiple testing). However, it is possible that human patient samples have higher variance compared to animal infection models. Investigators will thus use a sequential statistics approach in which they continuously adjust sample size estimates based on the variance of the accumulating data. It may be possible that no sufficient sample sizes for all bacterial pathogens of interest will be reached within two years.