A major unsolved problem of modern medicine is the often insufficient way to isolate pathogens in a vital form from the site of infection. Isolation of vital pathogens is essential for pheno-typic(culture-based) testing of bacterial antimicrobial resistances which is still considered as the gold standard of antimicrobial susceptibility testing. Therefore, culture-based methods are currently indispensable in routine clinical microbiology. Major drawbacks of culture-based methods are the long cultivation time and the high-rate of false-negative results.
Therefore more rapid and sensitive detection of vital microorganisms is of crucial importance to guarantee effective antimicrobial treatment: If antimicrobial treatment is ineffective, the av-erage chance of survival of patients with sepsis decreases by 7.6% per hour. Reasons for the low sensitivity of culture-based methods are the low concentration of bacteria (paucibacillary) in often large infected body fluids (i.e. pleura effusion, ascites). Here, current diagnostics have the disadvantage to use only a small fraction of the harvested body fluid (25 – 100 μl/ solid culture, 10 mL / bottle culture) so that most of the patient sample (ascites 1 - 10 liters, pleura effusion 1 - 2 liters) is discarded. We, therefore, aim to exploit our recent promising advances in trace analysis of pathogens in water chemistry. By combining rapid concentration methods with molecular and culture detection methods it is our aim to identify pathogens (i) in greater sensitivity by using larger amounts of body fluid (e.g. 1 CFU in 1 L) and (ii) more rapidly.

To this end, the project will develop in a first step a selective concentration method for three diagnostically highly challenging key pathogens (E.coli, E. faecalis and Candida spp.) in large-volume body fluids with a particular focus on effective elution of the adsorbed bacteria and fungi. To facilitate targeted research of affinity ligands, a screening platform (DANI) will be refined for examining adsorption and desorption processes of microorganisms. A variety of solid phases with universe binding affinity, as well as specific antibodies against target structure on bacterial or fungal cell membrane will be tested on this lab-on-chip system and best affinity ligands will be then used on a microorganism-extraction system based on monolithic affinity filtration that has already been established for water analysis.
Our vision is to establish in this highly interdisciplinary consortium between medicine, microbiology and water chemistry (1) a detailed library of optimal affinity binders for clinically relevant pathogens, also for future far reaching potentials for environment, food and water analysis and to develop (2) an analyzing platform for automated microorganism extraction from high-voluminous, paucibacillary body fluids to a small-voluminous, pathogen-enriched elution. Subsequent detection will be based on both, molecular and culture-based methods.