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The presence of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli was investigated in input (manure from livestock husbandry) and output samples of six German biogas plants in 2012 (one sampling per biogas plant) and two German biogas plants investigated in an annual cycle four times in 2013/2014. ESBL-producing Escherichia coli were cultured by direct plating on CHROMagar ESBL from input samples in the range of 10 0 to 10 4 colony forming units (CFU) per g dry weight but not from output sample. This initially indicated a complete elimination of ESBL-producing E. coli by the biogas plant process. Detected non target bacteria were assigned to the genera Acinetobacter, Pseudomonas, Bordetella, Achromobacter, Castellaniella, and Ochrobactrum. A selective pre-enrichment procedure increased the detection efficiency of ESBL-producing E. coli in input samples and enabled the detection in five of eight analyzed output samples. In total 119 ESBL-producing E. coli were isolated from input and 46 from output samples. Most of the E. coli isolates carried CTX-M-type and/or TEM-type beta lactamases (94%), few SHV-type beta lactamase (6%). Sixty-four blaCTX-M genes were characterized more detailed and assigned mainly to CTX-M-groups 1 (85%) and 9 (13%), and one to group 2. Phylogenetic grouping of 80 E. coli isolates showed that most were assigned to group A (71%) and B1 (27%), only one to group D (2%). Genomic fingerprinting and multilocus sequence typing (MLST) showed a high clonal diversity with 41 BOX-types and 19 ST-types. The two most common ST-types were ST410 and ST1210. Antimicrobial susceptibility testing of 46 selected ESBL-producing E. coli revealed that several isolates were additionally resistant to other veterinary relevant antibiotics and some grew on CHROMagar STEC but shiga-like toxine (SLT) genes were not detected. Resistance to carbapenems was not detected. In summary the study showed for the first time the presence of ESBL-producing E. coli in output samples of German biogas plants.

Diese Arbeit zeigt pflanzliche Alternativen zum Silomais auf, die als Biogassubstrat Verwendung finden sollen. In diesem Fall werden Gräser (Lolium perenne als Hochzuckergrasvariante und Lolium perenne als normale Vergleichssorte) und Leguminosen (Trifolium pratense, Medicago sativa und Lotus corniculatus) in Rein- und Mischbeständen auf ihre Eignung untersucht. Mit Hilfe zweier Kolbenfermentationsversuche wird das Gärverhalten und die damit verbundene Gesamtgasausbeute der Substrate quantitativ ermittelt. Die Gasausbeuten werden mit den Ergebnissen aus Futterqualitätsuntersuchungen verknüpft und auf Zusammenhänge geprüft. Die höchste Gasproduktion erreicht das Hochzuckergras in Reinsaat, gefolgt von den Hochzuckergrasmischungen mit Medicago sativa und Trifolium pratense. Es zeigen sich starke Beziehungen zwischen den Gasausbeuten und dem Gehalt an wasserlöslichen Kohlenhydraten und der Verdaulichkeit. Weniger stark stellt sich der Zusammenhang zum Stickstoffgehalt dar, das Bestehen einer Konzentrationsschwelle ist wahrscheinlich. Auch der erhöhte Gehalt an Tanninen in Lotus corniculatus zeigt sich in der Gasausbeute., In this work new crop biogas substrates are investigated as an alternative to silo corn. Here, grass (Lolium perenne as Sweetgrass and normal Lolium perenne as comparison) and legumes (Trifolium pratense, Medicago sativa and Lotus corniculatus) in pure stand and mixed stand are tested. The fermentation characteristics as well as the total gas formation are quantified using two piston-fermentation tests. The total gas formation is further correlated to the results of a feed-analyzing test to check for any interconnection. The highest gas production is accomplished by the Sweetgrass in pure stand, followed by the Sweetgrass mixtures with Medicago sativa and Trifolium pratense. Strong correlations between the quantity of gas production and the content of water soluble carbohydrates and digestibility are demonstrated. The link between gas production and nitrogen content is less pronounced, likely due to a concentration threshold. The higher content of tannins in Lotus corniculatus is shown in the gas yield as well.