Prevalence and characterization of Salmonella from meat in slaughterhouses in Hangzhou, China

Salmonella is an essential food-borne pathogenic microorganism. Humans could get infected by consuming of Salmonella-contaminated foods, especially contaminated meat. In this study, a total of 580 retail meat samples (280 pork, 240 chicken, and 60 goose) were collected from slaughterhouses in Hangzhou to determine the prevalence and antimicrobial susceptibility patterns of Salmonella. Isolates were characterized by serotyping, PFGE (Pulsed-field gel electrophoresis), Polymerase chain reaction (PCR), and antibiotic susceptibility testing. The rates of Salmonella-positive pork, chicken, and goose samples were 21.1% (n = 59), 10.4% (n = 25) and 10.0% (n = 6), respectively. The prevalence of Salmonella was 15.5% in slaughterhouses. Thirteen different Salmonella serovars were identified, and 6 isolates could not be identified. The most commonly prevalent serovars are Salmonella Rissen (S. Rissen) (n = 20, 22.2%), S. Derby (n = 16, 17.8%) and S. Typhimurium (n = 12, 13.3%). The detection rate of the remaining serovars ranged from 1.1%-11.11%. All Derby, Corvallis, and Kentucky strains were from pork. Seventy-two isolates (80.0%) showed drug resistance (DR) to at least one antibiotics, 19 (21.1%) were multi-drug resistant strains, 2 (2.2%) showed seven or more. The detection rate of Trimethoprim/Sulfamethoxazole-resistance (70.0%) was highest, followed by Ampicillin (55.6%). Salmonella resistance was found related to serovar and origin. The positive rates of DR gene sul1, sul2, sul3, class I integrons and blaTEM were 92.2%, 95.6%, 86.7%, 83.3% and 62.2%, respectively. Fifty-seven different PFGE patterns and 7 main clusters were obtained. This study revealed the high positive rates of Salmonella resistance and related DR genes, especially for Sulfamethoxazole-resistance and its related gene.