An Epidemiological Study on Salmonella in Tibetan Yaks from the Qinghai–Tibet Plateau Area in China.

Simple Summary: As a major economic pillar in Tibet, the yak breeding industry is an important source of income and livelihood for local farmers and herdsmen. Salmonella, one of the most important foodborne pathogens globally, has seriously threatened the healthy development of this industry for many years, causing huge economic losses for local herdsmen and related industries. Furthermore, there are many serotypes of Salmonella that can infect different hosts, causing varying degrees of damage. The aim of this study was to investigate the prevalence of Salmonella in yak farms in the Qinghai–Tibet Plateau area. A total of 223 strains of Salmonella were isolated from 1222 fecal samples from yaks from Tibet and Qinghai, with an overall isolation rate of 18.25% (223/1222). These 223 Salmonella isolates were serotyped, and their antimicrobial susceptibility, resistance genes, and virulence genes were investigated. Furthermore, MLST (Multi-Locus Sequence Typing) was applied to the isolates. The results showed that the carriage of Salmonella in Tibetan yaks is quite serious in the Qinghai–Tibet Plateau area, with Enteritidis Salmonella (17.94%) and Typhimurium Salmonella (13.90%) representing the predominant serotypes. Given that the Salmonella isolates also showed resistance to antimicrobial drugs, continuous monitoring of Salmonella infections and resistance in the Qinghai–Tibet Plateau area is needed to avoid the potential risk of foodborne disease transmission. Salmonella is an important foodborne pathogen that can cause a range of illnesses in humans; it has also been a key focus for monitoring in the field of public health, including gastroenteritis, sepsis, and arthritis, and can also cause a decline in egg production in poultry and diarrhea and abortion in livestock, leading to death in severe cases, resulting in huge economic losses. This study aimed to investigate the isolation rate, antimicrobial resistance, serotypes, and genetic diversity of Salmonella isolated from yak feces in various regions on the Qinghai–Tibet Plateau. A total of 1222 samples of yak dung were collected from major cities in the Qinghai–Tibet Plateau area, and the sensitivity of the isolated bacteria to 10 major classes of antibiotics was determined using the K-B paper disk diffusion method for drug susceptibility. Meanwhile, the serotypes of the isolated bacteria were analyzed using the plate agglutination test for serum antigens, and their carriage of drug resistance and virulence genes was determined using PCR and gel electrophoresis experiments. The isolated bacteria were also classified using MLST (Multi-Locus Sequence Typing). The overall isolation rate for Salmonella was 18.25% (223/1222), and the results of the antibiotic susceptibility tests showed that 98.65% (220/223) of the isolated bacteria were resistant to multiple antibiotics. In the 223 isolates of Salmonella, eight classes of 20 different resistance genes, 30 serotypes, and 15 different types of virulence genes were detected. The MLST analysis identified 45 distinct sequence types (STs), including five clonal complexes, of which ST34, ST11, and ST19 were the most common. These findings contribute valuable information about strain resources, genetic profiles, and typing data for Salmonella in the Qinghai–Tibet Plateau area, facilitating improved bacterial surveillance, identification, and control in yak populations. They also provide certain data supplements for animal Salmonella infections globally, filling research gaps. [ABSTRACT FROM AUTHOR]