Publication Database

Manure management measures to reduce the risk of spreading ESBL-/AmpC-producing Escherichia coli from chicken manure into the food chain (2023)

Art

Hochschulschrift

Autor

Thomas, Corinna (WE 10)

Quelle

Berlin: Mensch und Buch Verlag, 2023 — VI, 117 Seiten

Sprache

Englisch

Verweise

URL (Volltext): https://refubium.fu-berlin.de/handle/fub188/44185

Kontakt

Institut für Tier- und Umwelthygiene

Robert-von-Ostertag-Str. 7-13
14169 Berlin
+49 30 838 51845
tierhygiene@vetmed.fu-berlin.de

Abstract / Zusammenfassung

The prevalence of extended-spectrum beta-lactamase (ESBL)- and AmpC beta-lactamaseproducing Escherichia (E.) coli in the broiler production chain is high. The finding of these resistant bacteria in high numbers in barns and in the environment of broiler farms raises concerns about the use of potentially contaminated chicken manure as fertilizer on fields. As it is assumed that ESBL-/AmpC-producing E. coli can enter the human food chain by contaminated water, vegetables, and fruit after land application of chicken manure, better insights into the survival and the reduction kinetics of these bacteria during storage and chicken manure treatments are needed. Thus, the present work aimed to determine the reduction kinetics of ESBL-/AmpC-producing E. coli during composting and anaerobic digestion with a special focus on potential inactivation factors, above all temperature, carbon/nitrogen (C/N) ratio, and moisture content (MC). To that aim, three studies were carried out. In the first study, laboratory-scale anaerobic digestion tests were conducted at 37, 42 and 55 °C to investigate the influence of temperature on the reduction kinetics of ESBL-/AmpC-producing E. coli during anaerobic digestion of chicken manure. One ESBL- (CTX-M15) and one plasmid-mediated AmpC- (CMY-2) producing E. coli strain were added to the substrate to achieve an initial bacterial count of 7 log10 colony forming units (cfu) per mL. Both E. coli strains were below the detection limit of <100 cfu/mL after 35 days, with decimal reduction times (Dvalues) of 3-6 days at 37 °C, 1.5 days at 42 °C and 48 min at 55 °C. However, at 37 and 42 °C, ESBL-/AmpC-producing E. coli remained partially detectable by enrichment until the end of the trials after 35 days. Hence, the results showed a strong temperature dependency, whereas no direct correlation could be observed between pH, volatile fatty acids (VFAs) or ammonia (NH3) and E. coli reduction. The second study aimed to determine the effects of the C/N ratio and MC on the survival of ESBL-producing E. coli during laboratory-scale chicken manure composting in bioreactors. To that aim, a ESBL- (CTX-M15) producing E. coli strain was added to nine compost mixtures with different combinations of MC (20, 40, 60%) and C/N ratios (10:1, 20:1, 40:1) to obtain an initial bacterial count of 7 log10 cfu/g. The fastest decrease in E. coli was observed in all mixtures with a C/N ratio of 10:1 with D-values of 0.27 days to 0.60 days. Additionally, in dry mixtures with an MC of 20% and a C/N ratio of either 10:1 or 40:1, ESBL-producing E. coli were reduced faster than in the moist mixtures despite lower maximum temperatures within the bioreactors. The highest D-value of 4.82 days was determined for a mixture with a C/N ratio of 40:1 and 40% MC. While temperature was the main inactivation factor, in dry mixtures, desiccation also played a significant role. Significant effects of the C/N ratio and MC on the number of ESBL-producing E. coli as well as on temperature development were shown. In addition, it was demonstrated that even suboptimal composting mixtures – typical for chicken manure – led to a rapid reduction in ESBL-producing E. coli. To validate the results of the laboratory composting trials in a more practical environment, in a third study, pilot-scale composting of chicken manure was performed at the test grounds in Potsdam. Here, the influences of three different management treatments for chicken manure, composting in (i) static piles, (ii) static piles covered with a compost fleece, and (iii) periodically turned piles, were determined with respect to the survival of an artificially added, nonresistant E. coli strain (DSM 1116) during different environmental conditions (summer and winter). The results showed an even faster reduction in E. coli and higher temperatures within the compost mass than in the laboratory-scale composting trials. Within 24 hours, E. coli were no longer detectable by direct count in any piles in either center or subsurface locations. By day 28, E. coli were also no longer qualitatively detectable in any samples. Within these 24 hours, temperatures exceeded 50 °C in all piles, which was most likely responsible for the fast inactivation of E. coli. The statistical analysis revealed the significant influences of sample location (center, subsurface) and the total hours at temperatures ≥ 50 °C and ≥ 55 °C in the piles on the survival of E. coli in the chicken manure compost. Although no influences of season or manure treatment method were shown, periodical turning is recommended, especially in winter, to increase the likelihood of exposure of all parts of the compost, including possible ESBL-/AmpC-producing E. coli, to high temperatures. Taken together, the results of the three studies showed the effectiveness of both composting and anaerobic digestion in terms of ESBL-/AmpC-producing E. coli reduction. The reasons for the reduction in ESBL-/AmpC-producing-E. coli were multifactorial, with temperature being the main inactivation factor. Most likely due to the chicken manure characteristics of a low MC and a low C/N ratio, even in stored, nonmanaged or only minimally managed chicken manure, ESBL-producing-E. coli levels were reduced below the detection limit after one day. Therefore, concluding the results of this work, the risk of spreading ESBL-/AmpC-producing E. coli to land by using chicken manure, chicken manure compost, or digestate from biogas plants running on chicken manure is considered low. Composting of chicken manure with periodic turning or anaerobic digestion at thermophilic temperatures are the safest methods in terms of ESBL-/AmpC-producing E. coli reduction to treat chicken manure before application to land and are therefore highly recommended.