LAUSR

Simple Summary Rothia nasimurium is an opportunistic pathogen. It can infect animals such as dogs, pigs, ducks, rabbits, and geese, and antibiotic susceptibility tests have confirmed that this bacterium has a multidrug-resistant phenotype. In January 2022, chickens at a poultry farm in China’s Xinjiang Uygur Autonomous Region became ill and died. In order to determine the cause of the disease in these poultry farm chickens, the isolation and identification of the pathogens in the livers and other internal organs of the sick chickens were performed. A bacterial strain was isolated from the livers of the diseased chickens. The isolated strain was identified to be Rothia nasimurium. The isolate was resistant to 17 antibiotics, including ciprofloxacin, norfloxacin, and erythromycin, and was only sensitive to penicillin, amikacin, and tigecycline, to varying degrees. The animal pathogenicity tests showed that the isolate caused feather loss and death in chicks. In summary, Rothia nasimurium was isolated from chickens for the first time, and the biological characteristics of the bacterium were investigated in order to provide a reference for the clinical treatment, prevention, and control of Rothia nasimurium infection. Abstract Rothia nasimurium is a facultative anaerobic Gram-positive coccus belonging to the Rothia genus of the Micrococcaceae family. While Rothia nasimurium is considered an opportunistic pathogen, to date few studies have investigated its pathogenicity and drug resistance. In January 2022, chickens at a poultry farm in China’s Xinjiang Uygur Autonomous Region became ill and died. Treatment with commonly used Chinese medicines and antibiotics was ineffective, causing economic losses to the poultry farm. In order to determine the cause of the disease in these poultry farm chickens, the isolation and identification of the pathogens in the livers and other internal organs of the sick and dead chickens were performed. Further, animal pathogenicity tests, antibiotic susceptibility tests, and the detection of antibiotic resistance genes were carried out to analyze the pathogenicity and drug resistance of the identified pathogens. A Gram-positive coccus was isolated from the livers of the diseased chickens. The isolate was resistant to 17 antibiotics, including ciprofloxacin, chloramphenicol, and florfenicol, and was only sensitive to penicillin, amikacin, and tigecycline, to varying degrees. The results of the drug resistance gene testing indicated that the isolated bacterium carried 13 kinds of resistance genes. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, morphological observations, biochemical tests, and 16S rRNA gene sequence analysis were performed on the isolated bacterium, and it was determined that the isolated bacterial strain was Rothia nasimurium. The animal pathogenicity tests showed that the isolate caused feather loss and death in chicks; the clinical symptoms and necropsy lesions of the test chicks were consistent with those observed in the farmed chickens. A review of the literature revealed that, to date, there are no reports of infection with Rothia nasimurium in chickens. Thus, in this study, Rothia nasimurium was isolated from chickens for the first time and an investigation of the biological characteristics of the bacterium was carried out in order to provide a reference for the clinical treatment, prevention, and control of Rothia nasimurium infection.