Transfer and Microevolution of Avian Native IncA/C-Carrying Plasmid pRH-1238 during a Broiler Chicken Infection Study.

The emergence and spread of carbapenemase-producing (CPE) in wildlife and livestock animals pose an important safety concern for public health. With our broiler chicken infection study, we investigated the transfer and experimental microevolution of the -carrying IncA/C plasmid (pRH-1238) introduced by avian native subsp. serovar Corvallis without inducing antibiotic selection pressure. We evaluated the dependency of the time point of inoculation on donor ( Corvallis [12-SA01738]) and plasmid-free recipient [d-tartrate-fermenting (d-Ta) Paratyphi B (13-SA01617), referred to here as Paratyphi B (d-Ta)] excretion by quantifying their excretion dynamics. Using plasmid profiling by S1 nuclease-restricted pulsed-field gel electrophoresis, we gained insight into the variability of the native plasmid content among Corvallis reisolates as well as plasmid acquisition in Paratyphi B (d-Ta) and the enterobacterial gut microflora. Whole-genome sequencing enabled us to gain an in-depth insight into the microevolution of plasmid pRH-1238 in Corvallis and enterobacterial recipient isolates. Our study revealed that the fecal excretion of avian native carbapenemase-producing Corvallis is significantly higher than that of Paratyphi (d-Ta) and is not hampered by Paratyphi (d-Ta). Acquisition of pRH-1238 in other and several events of plasmid pRH-1238 transfer to different sequence types and demonstrated an interspecies broad host range. Regardless of the microevolutionary structural deletions in pRH-1238, the single carbapenem resistance marker was maintained on pRH-1238 throughout the trial. Furthermore, we showed the importance of the gut population as a vector of pRH-1238. In a potential scenario of the introduction of NDM-1-producing Corvallis into a broiler flock, the pRH-1238 plasmid could persist and spread to a broad host range even in the absence of antibiotic pressure.