SUPER safe

DFG Projekt (423210466)

Run-time: 01.11.2020 — 31.10.2022

Survival and pathogenicity of Clostridioides difficile in sewage, sewage sludge, surface water, animal manure, fodder, crops and silage -Treatment requirements to minimize health risks" (SUPER safe)

The Gram-positive, anaerobic endospore forming Clostridioides difficile is the major cause of nosocomial infectious diarrhoea in humans and livestock. C. difficile infection (CDI) is a toxin- mediated intestinal disease and occurs when the natural flora in the guts is disrupted by antibiotics. The hypervirulent nosocomial pathogen C. difficile is a burden for health care systems worldwide and, as an emerging pathogen C. difficile is a major matter of discussion in infection prevention and control. Treatment of CDI is hampered by C. difficile endospores which can persist antibiotic treatment in the guts, rapidly repopulate guts with vegetative cells and lead to recur of an infection. As a colonizer of the intestine C. difficile cells and spores could be excreted and found in feces of humans and animals. For this reason C. difficile can be clearly associated with feces. It is expected that C. difficile can be found in sewage, sewage sludge and animal manures as well and in other sources which could be contaminated with feces like surface water or fodder. Since there is a rising importance of anaerobic digestion AD for sewage sludge and animal manure treatment, attention should focus on survival and multiplication of C. difficile during AD and increasing release into the environment by anaerobic manure and wastewater treatment systems and utilization of residues as fertilizers.

The aim of the proposed research project is thus to identify environmental sources with a high prevalence of C. difficile. Enumeration and isolation of environmental C. difficile and further characterization of the toxigenic potential by analyzing e.g. genes for production of Toxin A or B and the binary toxin CDT is intended. Beside ribotyping, antibiotic susceptibility testing for determination of MIC and determination of respective antibiotic resistance genes and conjugative transposons present in isolated environmental strains should give information about epidemiological behavior. By establishing qPCR for enumeration of C. difficile cells and the conjugative transposon Tn5397 cell counts and pathogenicity of C. difficile in fecal- associated samples will be quantified. Since a large number of anaerobic digestors were installed in past years for treatment of sludge and manure, AD of sewage sludge and cattle manure will be simulated in lab-reactors to investigate survival or even growth or the reduction/elimination of C. difficile in terms of cell numbers and the conjugative plasmid outside of the cells. Such tests will include long term manure storage and ozonation and UV disinfection procedures, final treatment steps for sewage. By strengthening research in the field of microbiology and environmental engineering the anticipated work program should deliver results and extend knowledge on survival and the pathogenic potential of C. difficile in “fecal-associated” samples and allow to draw conclusions on transmission ways and to assess the health risk for human and animals.