Abstract
This study aimed to investigate the prevalence, serotype distribution, and antibiotic resistance, and to characterize the extended spectrum β-lactamases (ESBLs) producing Salmonella isolates from chicken and pork meats from retail markets in Guangdong province, China. A total of 903 retail meat samples (475 chicken and 428 pork meats) were obtained from six cities (Guangzhou, Shenzhen, Heyuan, Shaoguan, Foshan, and Yunfu) of Guangdong province between May 2016 and April 2017. High levels of Salmonella contamination were detected in chicken (302/475, 63.6%) and pork (313/428, 73.1%). Thirty-eight serotypes were identified in 615 detected Salmonella, and the serotypes varied greatly between chicken and pork samples. Agona (55/302, 18.2%), Corvallis (45/302, 14.9%), Kentucky (38/302, 12.6%), Mbandaka (32/302, 10.6%) was the dominant serotypes in chicken samples. However, Typhimurium (78/313, 24.9%), Rissen (67/313, 24.1%), Derby (66/313, 21.1%), and London (48, 15.3%) were the most common in pork samples. High rates of antibiotic resistance were found to sulfisoxazole (468/615, 76.1%), tetracycline (463/615, 75.3%), ampicillin (295/615, 48.0%), and ofloxacin (275/615, 44.7%). Notably, antimicrobial susceptibility tests identified resistance to polymyxin B (12/615, 2.0%) and imipenem (3/615, 0.5%). Multidrug-resistance (MDR) was detected in Salmonella isolated from chicken (245/302, 81.1%) and pork (229/313, 73.2%). The resistance rate of different Salmonella serotypes varied widely. Especially, isolates such as Typhimurium, Agona, Corvallis and Kentucky exhibited highly resistance to antibiotics. The MDR rate of Salmonella isolates from chicken was significantly higher than that from pork isolates (P < 0.05). Twenty-one Salmonella isolates were identified as ESBLs-producing, covering six Salmonella serotypes and displaying different pulse field gel electrophoresis (PFGE) genotypes. BlaOXA-1 was the dominant ESBLs gene (9/21, 42.9%), followed by blaCTX-M-55 (5/21, 23.8%). This study indicated that Salmonella was widespread in chicken and pork from retail markets in Guangdong province and the isolates showed high multidrug-resistance, especially the known multidrug-resistant Salmonella serotypes. Therefore, it is important to focus on Salmonella serotypes and strengthen the long-term monitoring of MDR Salmonella serotypes in animal-derived foods.
Highlights
Salmonella is a foodborne pathogen that causes morbidity and mortality worldwide (Scallan et al, 2011)
The main aim of this study was to determine the prevalence, serotype distribution, antibiotic resistance of Salmonella, and the phenotype and genotype of ESBLs-producing Salmonella isolated from chicken and pork meat from retail markets in Guangdong
We found the high levels of Salmonella contamination rate in chicken (63.6%) and pork (73.1%) collected from retail markets in Guangdong Province, China
Summary
Salmonella is a foodborne pathogen that causes morbidity and mortality worldwide (Scallan et al, 2011). In China, about 70– 80% of foodborne disease outbreaks are caused by Salmonella, and the majority of diseases are associated with the ingestion of contaminated livestock and poultry products (Wang et al, 2007). Antibiotic resistance of Salmonella is one of the most important public health problems worldwide. Multidrug-resistant (MDR) Salmonella could pose a serious threat to humans through the food chain (Barza, 2002; Lai et al, 2014). Extendedspectrum β-lactamases (ESBLs)-producing Salmonella have been frequently isolated from food animals in many countries, including China (Dahms et al, 2015; Ben Said et al, 2016; Ibrahim et al, 2016; Zhao et al, 2017)
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