Detection of Enterococcus cecorum in the drinking system of broiler chickens and examination of its potential to form biofilms

Nearly two decades ago, Enterococcus (E.) cecorum (EC) emerged as a new avian pathogen, which causes enterococcal spondylitis (ES) in broiler chickens, with serious consequences for productivity and animal welfare. Despite recent advances concerning knowledge about EC associated disease, epidemiology such as the source of infection still remains unclear. In the present study, we wanted to elucidate whether EC or other Enterococcus spp. can be found in a broiler drinking system, whether there are differences regarding different sampling time points and locations and if EC can generate biofilms in vitro. During two consecutive broiler cycles, we sampled inner and outer areas of drinking lines at three time points with two kinds of swabs. The samples were analyzed for EC and other Enterococcus spp. with cultural methods as well as partial 16S rRNA sequencing and only for EC with qPCR. E. faecium, E. faecalis, E. durans, E. hirae, E. casseliflavus, E. gallinarum, and E. villorum, but no EC were detected via isolation. A total of 120 of 192 samples were positive for EC by qPCR with Ct values below 40, seven samples having values below 30. There was an increase in EC DNA concentration up until the removal of the birds during the broiler cycles and differences were found between both cycles. The highest EC load was found on drinking cups. An assay was established to compare the ability of different EC strains and E. faecium and E. faecalis strains to generate biofilms. The different EC strains showed the ability to generate biofilms, but EC biofilm production varied between the experiments and replicates. Biofilm production of E. faecium and E. faecalis was more constant. Our study shows the importance of hygiene measures to reduce the risk of EC infection through drinking water lines, especially towards the end of the production cycle.