Publikationsdatenbank

The impact of feed additives on prevalence and conjugation of extended-spectrum beta-lactamase-producing Enterobacteriaceae in poultry (2020)

Art

Hochschulschrift

Autor

Saliu, Eva-Maria (WE 4)

Quelle

Berlin, 2020 — VII, 87 Seiten

Sprache

Englisch

Verweise

URL (Volltext): https://refubium.fu-berlin.de/handle/fub188/28796

Kontakt

Institut für Tierernährung

Königin-Luise-Str. 49
14195 Berlin
+49 30 838 52256
tierernaehrung@vetmed.fu-berlin.de

Abstract / Zusammenfassung

Due to their multi-drug resistance, ESBL-producing Enterobacteriaceae pose a major hazard on public health and global economy. A transmission from animals to humans is possible and thus, animals may serve as a reservoir for difficult to treat infections in humans. In livestock, the highest prevalence of ESBL-producing Enterobacteriaceae is commonly found in poultry. Measures to reduce the prevalence of ESBL-producing Enterobacteriaceae are of great importance. Promising results were observed in broilers challenged with ESBL-producing E. coli and fed probiotic products. An important aspect concerning the reduction of ESBL-producing Enterobacteriaceae is their ability to spread their resistance genes within and across species. As ESBL encoding genes are commonly located on plasmids, conjugation enables horizontal gene transfer and should be considered when developing reduction measures. The objective of this study was to investigate the impact of different feed additives and nutrition related stress factors on conjugation of ESBL-producing Enterobacteriaceae in broilers. A suitable mating pair evolved from a screening experiment with five different ESBL-producing E. coli donor strains and various potential recipients, commonly detected in the gastrointestinal tract of broilers. The chosen mating pair comprised the donor E. coli ESBL10682, producing the extended-spectrum beta-lactamase CTX-M-1, and the potentially pathogenic Salmonella Typhimurium L1219-R32 strain. Conjugation events occurred at a relative high frequency of 10-5 within a period of four hours, resembling the transit time through the gastrointestinal tract of broilers. The initial donor and recipient concentration was 108 cfu/mL and the donor/recipient ratio was 1:1. Other mating pairs showed no or lower conjugation frequencies and a kinetic conjugation experiment revealed differences between different incubation durations (0, 2, 4, 6, 8 and 22 hours). The mating pair was challenged with different nutrition related stress factors in an in vitro experiment. To circumvent the bias bacterial growth exerts on conjugation frequency, a stress impact factor was introduced to correct the results. The expected increase in conjugation frequency failed to appear, even when challenged with subtherapeutic levels of antibiotics. Instead, the feed additives copper, zinc and propionate decreased the conjugation frequency significantly with approximately 3, 0.8, and 2 log units respectively. No significant impact on conjugation events was observed for acetate, n-butyrate or lactate. The antibiotics nitrofurantoin, sulfamethoxazole/trimethoprim and cefotaxime also showed conjugation frequencies declining with up to 1.5, 2 and 0.7 log units respectively. Regarding experimental conditions, pH had no significant impact on the results while increasing osmolality reduced conjugation frequencies with up to 0.7 log units. These results were complemented by an animal trial paired with an ex vivo experiment. Newly hatched male Cobb 500 broiler chicks were randomly allocated to nine different feeding groups with seven replicates each. The experimental feed comprised a control, two diets supplemented with one of two Lactobacillus strains (L. agilis, L. salivarius), two diets supplemented with different phytobiotic feed additives containing the essential oils carvacrol, cinnamaldehyde and eugenol (Formulation C, Formulation L) and four diets comprising the combination of one Lactobacillus strain and one phytobiotic product. The Lactobacillus strains and the phytogenic products were chosen due to their ability to inhibit an ESBL-producing E. coli strain in a previous in vitro experiment. Cecal content was obtained at two weeks of age and the mating pair E. coli ESBL10682/Salmonella Typhimurium L1219-R32 was added at defined concentrations and incubated for four hours. Most surprisingly, the intended Salmonella recipient was not detected to form transconjugants, but instead, indigenous SXT-resistant Enterobacteriaceae accepted the plasmid. An increase of 0.5 – 0.6 log units was observed in the conjugation frequencies of the combination groups L. salivarius + Formulation C, L. salivarius + Formulation L and L. agilis + Formulation C. Also, the group fed Formulation C showed an enhanced (0.2 log units) conjugation frequency. Even though statistically significant, from a microbiological view, these differences are rather small and not conclusive. At five weeks of age, the prevalence of ESBL-producing Enterobacteriaceae was determined in the cecal content. The control group revealed a significantly higher prevalence than the groups supplemented with the Lactobacillus strains and/or phytobiotic feed additives. Additionally, it was observed that there were quantitative differences between samples, a fact that is commonly neglected in surveys screening for the prevalence of ESBL-producing Enterobacteriaceae. In conclusion, feed additives were able to reduce the transfer of ESBL-carrying plasmids from an E. coli donor to a Salmonella Typhimurium recipient. The most promising results were observed for copper and propionate.