Abstract
Pickled ready-to-eat meat (PRTEM) is a meat product that is treated with various seasonings and then cooked. PRTEM is a popular food consumed mostly in China and some Asian countries. Since this food is considered ‘ready to eat’, once it is contaminated by foodborne pathogens such as Salmonella, the prospect for significant morbidity, mortality, and immeasurable economic losses can occur. Here we investigated the prevalence and concentration of Salmonella in 107 PRTEM samples collected from Shaanxi, China during 2015–2016. Furthermore, we analyzed the serotype, antibiotic susceptibility, and presence of antibiotic resistance genes and amino acid mutations in 219 Salmonella isolates, followed by subtyping of 115 representative isolates. The average detection rate of Salmonella-positive PRTEM was 58.9%, and the average most probable number (MPN) of Salmonella in positive samples was 2.27 logMPN per gram of sample (range: 2.10–2.43). Ten serotypes were identified from the 219 Salmonella isolates, with S. Thompson (37.9%) and S. Indiana (20.5%) being predominant. The remaining serotypes were S. Typhi (7.8%), S. Typhimurium (7.3%), S. Mbandaka (6.9%), S. Albany (6.4%), S. Blockley (5.5%), S. Infantis (4.1%), S. Escanaba (3.2%), and S. Dusseldorf (0.5%). All isolates were resistant to ceftiofur (100%), while most of them were resistant to ciprofloxacin (99.1%), amoxicillin-clavulanic acid (97.7%), trimethoprim-sulfamethoxazole (96.4%), ampicillin (92.3%), sulfisoxazole (92.2%), tetracyclines (90.4%), and nalidixic acid (90.4%), respectively. A single mutation of Ser83Phe (27.1%) and double mutations of Ser83Phe-Asp87Gly (25.9%) in GyrA were detected in 85 isolates, whereas mutations of Thr57Ser (63.9%) and Ser80Arg (36.1%) in ParC were detected in 122 isolates. qnrB, oqxAB, aac(6′)-Ib, and qnrA were present in 50 (22.8%), 48 (21.9%), 26 (11.9%), and 1 (0.5%) isolate(s), respectively. Pulse field gel electrophoresis results revealed that those isolates recovered from the same type of PRTEM or the same sampling place shared identical or similar DNA profiles, antibiotic resistance phenotypes, and even plasmid-mediated quinolone resistance encoding genes. The findings indicate that Salmonella is commonly prevalent in PRTEMs at high concentrations in Shaanxi, China. More attention should be paid to the processing and storage of this ready-to-eat food to prevent bacterial contamination and foodborne outbreaks.
Highlights
Salmonella is a genus of Gram-negative bacteria that causes human gastroenteritis, enteric fever, and other fatal diseases
The maximum value of Salmonella was detected in chicken wing (2.43 logMPN per gram Pickled ready-to-eat meat (PRTEM)), while the minimum value was detected in duck wing (2.10 logMPN per gram PRTEM)
No significant (P > 0.05) difference was found in MPN values among the eight types of PRTEM samples that were positive for Salmonella (Table 1)
Summary
Salmonella is a genus of Gram-negative bacteria that causes human gastroenteritis, enteric fever, and other fatal diseases. It is recognized as one of the major pathogens for public health and food safety (Liu et al, 2018). Salmonella is still an important pathogen associated with foodborne outbreaks and human diseases in the United States and most European countries (Centers for Disease Control [CDC], 2014; European Food Safety Authority (EFSA), 2017). Enteritidis are the most common serotypes involved in an increasing number of foodborne outbreaks in some countries (Gong et al, 2017; Li et al, 2017). Poultry and poultry products are considered the primary hosts of Salmonella (Yang et al, 2011), members of this genus have been recovered from various foods including pork (Sanchez-Maldonado et al, 2016), nuts (Zhang et al, 2017), vegetables (Han et al, 2008), and other retail products (Ed-Dra et al, 2017; Yang et al, 2016; Yang et al, 2010)
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