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Background and objectives: Colonisation of broiler with ESBL- and AmpC- producing Enterobacteriaceae is well known, resulting in the possibility of transfer to humans either by a close contact to broiler flocks or through contaminated retail meat. To examine potential intervention strategies regarding hygiene- and management measures a broiler colonisation model was established.
Materials and methods: Broiler were conventionally housed in to identify the oral colonisation dose and to establish a seeder- bird- colonisation model close to real farming conditions. ESBL-/ AmpC- negative day- old broiler were orally co-infected on the third day of life with one ESBL- and one AmpC- producing E. coli strain. Colonisation success was proven by cloacal swabs over a period of 14 to 35 days and a final section. By using different selective media it was possible to verify in vivo plasmid transfer between the two strains.
Results: An oral infection dose of 102 cfu per animal is sufficient to colonise broiler 24 h post infection up to the end of the trial. A relation of 1:5 infected (seeder) to susceptible animals is adequate to colonise the complete flock. In addition transformants carrying both resistant plasmids were detectable after 72 h p.i.
Conclusion: Given the low infection dose and seeder numbers the spread of ESBL-/ AmpC- producers in conventional farms is not surprising. We will test hygiene- and management interventions using this model as a possible approach for reduction.