The Occurrence of Antimicrobial-Resistant in Hatcheries and Dissemination in an Integrated Broiler Chicken Operation in Korea.

Positive identification rates of in hatcheries and upstream breeder farms were 16.4% (36/220) and 3.0% (6/200), respectively. Among the serovars identified in the hatcheries, . ser. Albany (17/36, 47.2%) was the most prevalent, followed by the serovars . ser. Montevideo (11/36, 30.6%) and . ser. Senftenberg (5/36, 13.9%), which were also predominant. Thirty-six isolates showed resistance to at least one antimicrobial tested, of which 52.8% ( = 19) were multidrug resistant (MDR). Thirty-three isolates (enrofloxacin, MIC ≥ 0.25) showed point mutations in the A and C genes. One isolate, . ser. Virchow, carrying the gene from the breeder farm was ceftiofur resistant. Pulsed-field gel electrophoresis (PFGE) showed that 52.0% . ser. Montevideo and 29.6% . ser. Albany isolates sourced from the downstream of hatcheries along the broiler chicken supply chain carried the same PFGE types as those of the hatcheries. Thus, the hatcheries showed a high prevalence of isolates with high antimicrobial resistance and no susceptible isolate. The AMR isolates from hatcheries originating from breeder farms could disseminate to the final retail market along the broiler chicken supply chain. The emergence of AMR in hatcheries may be due to the horizontal spread of resistant isolates. Therefore, control in hatcheries, particularly its horizontal transmission, is important.