Publikationsdatenbank

Molecular Epidemiology and Vertical Transmission of ESBL-/AmpC-producing Enterobacteriaceae along the Broiler Production Chain (2018)

Art

Hochschulschrift

Autor

Projahn, Michaela (WE 10)

Quelle

Berlin: Mensch und Buch Verlag, 2018 — 126 Seiten

Sprache

Englisch

Verweise

URL (Volltext): https://refubium.fu-berlin.de/handle/fub188/22449

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

Enterobacteriaceae which demonstrate resistance against beta-lactam antibiotics are of major concern in public health. The occurrence of extended-spectrum beta-lactamase (ESBL)-/AmpC betalactamase-producing E. coli in humans and animals is a challenging problem in antibiotic treatment in human and veterinary medicine. Especially in broiler chickens these resistant bacteria were frequently detected and a certain relevance of the exposure of contaminated chicken meat to humans is controversially discussed during the last decades. However, is was found, that ESBL-/pAmpC-producing Enterobacteriaceae were detectable on all stages of the broiler production and that already one-day old (grand-/parent)chicks can be affected. During the RESETII-project we therefore investigated seven ESBL-/pAmpC-positive parent broiler flocks, their respective hatching eggs as well as the subsequent broiler fattening flocks at the fattening farms as well as on slaughterhouse level concerning the occurrence of the resistant bacteria (chain investigations A-G). This project was performed by the Institute for Animal Hygiene and Environmental Health as well as the Institute of Food Safety and Food Hygiene from the Freie Universität Berlin. The task of the presented PhD thesis was to investigate the collected samples and resistant strains with regard to possible vertical transmission events in the whole broiler production chain. Therefore, high resolution molecular methods like pulsed-field gel-electrophoresis (PFGE) as well as whole genome sequencing (WGS) was applied to the respective isolates to determine their phylogenetic relationship. Using these methods, it could be shown that the introduction of the ESBL-/pAmpCproducing Enterobacteriaceae from the parent flocks into the hatchery occurred via contaminated egg shells (pseudo-vertical transmission) and that these bacteria can also survive the disinfection procedure. The hatchery acts as a reservoir for the resistant bacteria and certain strains are stepwise transmitted to the recently hatched chicks via the hatchery environment. However, the colonization of the chicks can also occur later on at the fattening farms. This indicates that the transmission routes of the ESBL-/pAmpC-producing Enterobacteriaceae in the broiler production are highly complex. Once the broiler chickens are infected with the resistant bacteria they directly introduce them into the slaughterhouse and the processing steps of the chicken meat. Especially the scalding and the defeathering steps are critical for cross-contamination events as shown in this study. Furthermore, selected isolates from all stages of the broiler production where investigated concerning the occurrence of virulence associated genes (VAGs) and the ability to produce curli fibers and cellulose. These factors support the colonization of a respective host as well as the survival in unfavorable environmental conditions. Using a macrocolony assay it could be shown that most of the tested E. coli isolates were able to produce curli fibers and cellulose which are the major components of biofilms. Therefore, it is very likely that these ESBL-/pAmpC-producing E. coli strains are also highly resistant against environmental stress and for example might also better survive certain cleaning and disinfection procedures. In addition, the investigated E. coli strains also showed up to harbor high numbers of VAGs. However, the numbers and the distribution of certain genes and virulence gene classes varied among the strains. Therefore, no specific VAG could be identified for the enhanced survival in broiler chickens. Furthermore, only isolates of one chain transmission investigation could be assigned as extra-intestinal pathogenic E. coli strains (ExPEC). This indicates that further investigations on the impact of certain bacterial factors on the survival, spread and transmission of ESBL-/pAmpC-producing E. coli in the broiler production chain are needed. For the successful development and application of intervention strategies against these resistant bacteria in the whole broiler production chain the complex network of transmission routes as well as supporting bacterial factors should be considered. Therefore, further detailed studies using an appropriate high number of samples and isolates as well as respective high resolution molecular methods need to be carried out.