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In drei verschiedenen Teilanalysen wurden Erkenntnisse über die Wirksamkeit von Interventionsmaßnahmen gegen das Vorkommen und die Verbreitung von ESBL/AmpC-bildenden E. coli in der Hühnermast gewonnen. Literaturdaten und praktische Laborergebnisse, die teilweise selbst erhoben wurden, flossen in ein mathematisches Modell ein, um die Auswirkungen von Haltungsparametern und konkreten Interventionsmaßnahmen prädiktiv berechnen zu können. Die zusammengefassten Ergebnisse zeigen einen Einfluss der Maßnahmen „Competitive Exclusion“, „Reinigung und Desinfektion“ sowie den Haltungsparametern „Rasse“, „geringe Besatzdichte“ und „erhöhte Einstreumenge“ auf das Vorkommen von bestimmten ESBL/AmpC-bildenden E. coli. Zusätzlich zu den Einzelmaßnahmen wurden im Modell mehrere Kombinationen getestet, wobei zwei unterschiedlichen Szenarien verwendet wurden, entweder der Stall oder die Eintagsküken waren zu Beginn der Mastperiode positiv. Diese Kombinationen ergaben eine deutliche Reduktion der resistenten E. coli in den infizierten Tieren, in deren Ausscheidungen und in der Einstreu. In diesem Zusammenhang wären Daten aus tierexperimentellen Studien zu kombinierten Maßnahmen interessant. Weitere wissenschaftliche Ergebnisse könnten zu einem optimierten Modell beitragen, damit es die realen Bedingungen besser widerspiegelt. Zu einer weiteren Präzisierung könnte zum Beispiel die dezidierte mathematische Berechnung des Wachstums von resistenten E. coli in den unterschiedlichen Teilen des Gastrointestinaltrakts des Huhns und in der Einstreu führen, unter Berücksichtigung von pH-Wert und Temperatur. Ungeachtet dessen bietet die vorliegende Version des Modells eine nützliche Unterstützung bei der Vorhersage der Auswirkung unterschiedlicher Maßnahmen auf das Auftreten und die Verbreitung von ESBL/AmpC-bildenden E. coli in Masthuhnbetrieben. Diese Ergebnisse können zu einer umfassenden Quantitativen mikrobiologischen Risikobewertung (QMRA) beitragen, mittels derer die Effizienz von Risikominderungsmaßnahmen in der gesamten Broilerproduktionskette, von der Brüterei und Aufzucht über die Mast, Schlachtung, Verarbeitung und den Einzelhandel bis hin zum Verzehr - from farm to fork, bestimmt werden kann.
Livestock animals, especially poultry, are a known reservoir for extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli (E. coli). They may enter the pen either via positive day-old chicks or via the environment. We developed a mathematical model to illustrate the entry and dissemination of resistant bacteria in a broiler pen during one fattening period in order to investigate the effectiveness of intervention measures on this infection process. Different management measures, such as varying amounts of litter, a slow-growing breed or lower stocking densities, were tested for their effects on broiler colonization. We also calculated the impact of products that may influence the microbiota in the chicks’ digestive tract, such as pre- or probiotics, feed supplements or competitive exclusion products. Our model outcomes show that a contaminated pen or positive chicks at the beginning of the fattening period can infect the entire flock. Increasing the amount of litter and decreasing the stocking density were shown to be effective in our model. Differences in the route of entry were found: if the chicks are already positive, the litter quantity must be increased to at least six times the standard of 1000 g/m2, whereas, if the pen is contaminated on the first day, three times the litter quantity is sufficient. A reduced stocking density of 20 kg/m2 had a significant effect on the incidence of infection only in a previously contaminated pen. Combinations of two or three measures were effective in both scenarios; similarly, feed additives may be beneficial in reducing the growth rate of ESBL-producing E. coli. This model is a valuable tool for evaluating interventions to reduce the transmission and spread of resistant bacteria in broiler houses. However, data are still needed to optimize the model, such as growth rates or survival data of ESBL-producing E. coli in different environments.
Previous research identified veterinary clinics as hotspots with respect to accumulation and spread of multidrug resistant extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (EC). Therefore, promoting the prudent use of antibiotics to decrease selective pressure in that particular clinical environment is preferable to enhance biosecurity for animal patients and hospital staff. Accordingly, this study comparatively investigated the impact of two distinct perioperative antibiotic prophylaxis (PAP) regimens (short-term versus prolonged) on ESBL-EC carriage of horses subjected to colic surgery. While all horses received a combination of penicillin/gentamicin (P/G) as PAP, they were assigned to either the “single-shot group” (SSG) or the conventional “5-day group” (5DG). Fecal samples collected on arrival (t0), on the 3rd (t1) and on the 10th day after surgery (t2) were screened for ESBL-EC. All isolates were further investigated using whole genome sequences. In total, 81 of 98 horses met the inclusion criteria for this study. ESBL-EC identified in samples available at t0, t1 and t2 were 4.8% (SSG) and 9.7% (5DG), 37% (SSG) and 47.2% (5DG) as well as 55.6% (SSG) and 56.8% (5DG), respectively. Regardless of the P/G PAP regimen, horses were 9.12 times (95% CI 2.79–29.7) more likely to carry ESBL-EC at t1 compared to t0 (p < 0.001) and 15.64 times (95% CI 4.57–53.55) more likely to carry ESBL-EC at t2 compared to t0 (p < 0.001). ESBL-EC belonging to sequence type (ST) 10, ST86, ST641, and ST410 were the most prevalent lineages, with blaCTX–M–1 (60%) being the dominant ESBL gene. A close spatio-temporal relationship between isolates sharing a particular ST was revealed by genome analysis, strongly indicating local spread. Consequently, hospitalization itself has a strong impact on ESBL-EC isolation rates in horses, possibly masking differences between distinct PAP regimens. The results of this study reveal accumulation and spread of multi-drug resistant ESBL-EC among horses subjected to colic surgery with different P/G PAP regimens, challenging the local hygiene management system and work-place safety of veterinary staff. Moreover, the predominance of particular ESBL-EC lineages in clinics providing health care for horses needs further investigation.