Salmonella enterica is considered a significant threat to the global poultry industry and public health. In recent decades, antimicrobial resistance in Salmonella enterica has attracted increasing concern throughout the world. However, limited information is available on Salmonella enterica among different breeds of breeder chickens. Thus, this study aimed to compare the prevalence, serotype distribution, emergence of extended-spectrum beta-lactamases (ESBLs), antimicrobial resistance, and genetic resistance mechanisms in Salmonella enterica among different breeds of breeder chickens. A total of 693 samples (dead embryos, cloacal swabs, water, feed, environmental swabs, and meconium of newly hatched chicks) were selected and cultured for Salmonella from four breeder chicken farms in Shandong province, China, representing one imported and three native breeds, and the isolates were further serotyped. Of the Salmonella isolates, susceptibility to 11 antimicrobials of 5 classes, ESBL screening, and the presence of 21 antimicrobial resistance genes were determined in the present study. Overall, 94 (13.6%) isolates were recovered, which were divided into 3 serotypes (Salmonella Pullorum (n = 36), Salmonella Thompson (n = 32), and Salmonella Enteritidis (n = 26)). The results showed that the prevalence of Salmonella enterica isolates from the imported breeds was higher compared with the three domestic breeds. Eight of the ninety-four isolates were ESBL-positive strains, which were recovered from a domestic breed chicken farm. These eight ESBL-producing isolates were serotyped to Pullorum. Surprisingly, Salmonella Enteritidis (S. enteritidis) and S. pullorum were simultaneously isolated from a single dead embryo observed among one native breed. Meanwhile, among the Salmonella isolates, 53.2% (50/94) were multidrug-resistant strains, and 44.7% (42/94) of the isolates presented resistance to at least five antibiotics. Nearly all of the isolates (97.9%, 92/94) were resistant to at least one antimicrobial; one isolate of S. Thompson was resistant to seven antimicrobial agents belonging to four different classes. The carriage rate of three resistance genes (tetA, tetB, and sul1) among isolates from the imported breeds (87%, 70%, and 65.2%) was higher than that in those from domestic breeds (35.2%, 36.6, and 14.1%). To our knowledge, this is the first report of ESBLs-producing Salmonella isolated from a Chinese native breed of breeder chickens. Our results also highlight that a high prevalence of multidrug-resistant Salmonella enterica contamination is widespread among different breeds of breeder chickens, which is a major risk of food-borne diseases and public health.
We present a complete genome sequence of an aviadenovirus Otus scops adenovirus (OsAdV) discovered from the cloaca of an Otus scops (a small raptor widely distributed in the world), which was collected from an island off the northeast coast of China. Thirty protein coding genes were predicted in this 40239-bp-long genome, which contains the largest ber protein among all reported aviadenoviruses. This owl genome is highly divergent and has only 55% average protein identity compared with other adenovirus genomes and all reported proteins. Phylogenetic analyses placed OsAdV deep within the genus Aviadenovirus and formed a single clade with a previous reported owl adenovirus in Japan. This is the second complete genome sequence of aviadenovirus discovered in owls, which has 62% average protein identity compared with the rst reported owl adenovirus. Combining this result with comparative genomic analysis of all aviadenoviruses, we propose that this owl virus and previous reported owl virus in Japan can be assigned as two new species in the genus Aviadenovirus. This research contributes to an improved understanding of infectious disease among raptors and owls. Full TextAdenoviruses are DNA viruses with icosahedral capsid and non-segmented, double-stranded linear DNA genome [1]. There are six genera in the family Adenoviridae, including Atadenovirus, Aviadenovirus, Ichtadenovirus, Mastadenovirus, Siadenovirus, and Testadenovirus (https://talk.ictvonline.org/taxonomy/; [2]). Members of the genera Aviadenovirus mainly infect birds and can cause infectious diseases in many cases. At early stage of Aviadenovirus research, discoveries of new Aviadenovirus species were mainly reported in poultry, such as Fowl aviadenovirus A. Symptoms of Aviadenovirus infection in domestic fowls may include body hepatitis, egg drop syndrome, hemorrhagic enteritis, gizzard erosion, and hydropericardium syndrome [3][4][5][6][7][8]. With the development of virus research methods, especially the advent of high-throughput sequencing, more Aviadenovirus were discovered outside the poultry industry [9]. Until now, NCBI has recorded 194 genomic assemblies of more than 15 Aviadenovirus species, many of these genomes were sequenced from wild birds. As the main reservoirs for zoonotic viruses, wild animals were showing high potential and importance for discovery of unknown viruses [10]. In recent years, researches of adenovirus in wild birds have shown that the diversity of adenoviruses in wildlife may far exceeds that which is currently known [11][12][13]. Researches of Aviadenovirus in a wide range of avian species, especially wild birds, are important for the comprehensive understanding of adenovirus classi cation and evolution.
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