Poster presented in One Health EJP Annual Scientific Meeting

June 9^th, 2021

Leng J., Ritchie J., Fivian- Hughes A., Van der Puten B., Trung NV., Oldenkamp R., Bootsma M., Kumartt S., Hoa Ngo T., Berens C., Alvarez J., Ferrandis- Vila M., Fruth A., Schwarz S., Bethe A., Menge C., Schultsz C., Semmler T. and La Ragione R.

Aim: To assess the impact of the simultaneous inoculation multiple Escherichia coli strains harbouring different ESBL plasmids in an in vitro model of the chicken caeca.
Methods: A continuous flow in vitro model of the chicken caeca was inoculated with a cocktail of 17 ESBL harbouring E. coli strains. These were associated with four different hosts and from four different countries. Samples from the vessels were plated
onto culture media to enumerate the number of total bacteria, total E. coli, ceftiofur-resistant E. coli and the original cocktail strains (ceftiofur- and rifampicin-resistant). The fate of individual strains within the model was monitored using ORFan gene
multiplex PCR assays. Finally, replica plating was used to identify any commensal E. coli that had acquired ESBL resistance genes.
Results: The cocktail strains were able to persist during the 72-hour experiment, although the total CFU/ml and number of individual strains decreased over time. The multiplex PCR assays showed that different strains were present in the vessels for
varying lengths of time. No trans-conjugants were detected when 108 CFU/ml of the E. coli isolate cocktail was added to the model. When vessels were inoculated with a 1010 CFU/ml cocktail and potential trans-conjugants were isolated in samples taken at 48 and 72 hours post inoculation.
Conclusions: Here, we have shown that multiple ESBL-producing E. coli strains can persist within an in vitro model of the chicken caeca for 72 hours and some of these appear able to transfer their ESBL plasmid to the pre-existing commensal E. coli

	School of Veterinary Medicine. Faculty of Health and Medical Sciences. University of Surrey.
	Amsterdam Umc.
	Department of Medical Microbiology. Academic Medical Center. University of Amsterdam.
	Julius Centre for Health Sciences and Primary Care. Universitair Medisch Centrum Utrecht (UMC Utrecht).
	Robert Koch Institute (RKI).
	Clinical Research Unit. University of Oxford.
	Institute of Molecular Pathogenesis. Friedrich Loeffler Institut-Bundesforschungsinstitut fuer Tiergesundheit (FLI).
	Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM).
	Departamento de Sanidad Animal. Facultad de Veterinaria. Universidad Complutense (UCM).
	University of Minnesota (UMM).
	Institute of Microbiology and Epizootics. Freie Universität Berlin.