Salmonella is an important food-borne pathogen associated with public health and high economic losses. To investigate the prevalence and the characteristics of Salmonella in a pig slaughterhouse in Yangzhou, a total of 80 Salmonella isolates were isolated from 459 (17.43%) samples in 2016-2017. S. Derby (35/80, 43.75%) was the most prevalent, followed by S. Rissen (16/80, 20.00%) and S. Newlands (11/80, 13.75%). The highest rates of susceptibility were observed to cefoxitin (80/80, 100.0%) and amikacin (80/80, 100.0%), followed by aztreonam (79/80, 98.75%) and nitrofurantoin (79/80, 98.75%). The highest resistance rate was detected for tetracycline (65/80, 81.25%), followed by ampicillin (60/80, 75.00%), bactrim (55/80, 68.75%), and sulfisoxazole (54/80, 67.50%). Overall, 91.25% (73/80) of the isolates were resistant to at least one antibiotic, while 71.25% (57/80) of the isolate strains were multidrug resistant in the antimicrobial susceptibility tested. In addition, 86.36% (19/22) of the 22 antimicrobial resistance genes in the isolates were identified. Our data indicated that the resistance to certain antimicrobials was significantly associated, in part, with antimicrobial resistance genes. Furthermore, 81.25% (65/80) isolates harbored the virulence gene of mogA, of which 2 Salmonella Typhimurium isolates carried the mogA, spvB and spvC virulence genes at the same time. The results showed that swine products in the slaughterhouse were contaminated with multidrug resistant Salmonella commonly, especially some isolates carry the spv virulence genes. The virulence genes might facilitate the dissemination of the resistance genes to consumers along the production chain, suggesting the importance of controlling Salmonella during slaughter for public health.

Mycoplasma synoviae (M. synoviae) is a serious avian pathogen that causes significant economic losses to chicken and turkey producers worldwide. The currently available live attenuated and inactivated vaccines provide limited protection. The objective of this study was to identify potential subunit vaccine candidates using immunoproteomics and reverse vaccinology analyses and to evaluate their preliminary protection. Twenty-four candidate antigens were identified, and five of them, namely RS01790 (a putative sugar ABC transporter lipoprotein), BMP (a substrate-binding protein of the BMP family ABC transporter), GrpE (a nucleotide exchange factor), RS00900 (a putative nuclease), and RS00275 (an uncharacterized protein), were selected to evaluate their immunogenicity and preliminary protection. The results showed that all five antigens had good immunogenicity, and they were localized on the M. synoviae cell membrane. The antigens induced specific humoral and cellular immune responses, and the vaccinated chickens exhibited significantly greater body weight gain and lower air sac lesion scores and tracheal mucosal thicknesses. Additionally, the vaccinated chickens had lower M. synoviae loads in throat swabs than non-vaccinated chickens. The protective effect of the RS01790, BMP, GrpE, and RS00900 vaccines was better than that of the RS00275 vaccine. In conclusion, our study demonstrates the potential of subunit vaccines as a new approach to developing M. synoviae vaccines, providing new ideas for controlling the spread of M. synoviae worldwide.

Mycoplasma synoviae (M. synoviae) is a serious avian pathogen causing severe economic losses to chicken and turkey producers worldwide. The currently available live attenuated vaccine and inactivated vaccine on the market elicit only limited protection. The aim of this study was to identify antigenic proteins of M. synoviae as potential subunit vaccine candidates. In immunoproteomics and reverse vaccinology analyses, a total 24 candidate antigens were picked out. Five candidate antigens were selected to evaluate immunogenicity and preliminary protection in a chicken model, including RS01790 (lipoprotein, putative sugar ABC transporter), BMP (BMP family ABC transporter substrate-binding protein), GrpE (nucleotide exchange factor), RS00900 (putative nuclease) and RS00275 (Uncharacterized protein). The results showed that the five antigens had good immunogenicity. They could be localized on the M. synoviae cell membrane and adhere to DF-1 cells using indirect immunofluorescence assay. They induced specific humoral and cellular immune responses. Vaccine efficacy was evaluated by observing weight gain, pathogen load, pathological changes. As a result, the vaccinated chickens revealed significantly higher body weight gain, with lower air sac lesion scores and tracheal mucosal thicknesses. The vaccinated chickens also showed lower M. synoviae loads in throat swabs than nonvaccinated chickens. The protective effect of BMP, GrpE and RS00900 vaccines is better than that of RS01790 and RS00275. In conclusion, our study demonstrates the potential of using subunit vaccine, providing new ideas for the development of M. synoviae vaccines. The vaccine candidates may contribute to the future development of therapeutic strategies to control the spread of M. synoviae worldwide.