Abstract
The present study was aimed to determine the prevalence and characteristics of Salmonella isolated from meat samples of commercial broilers (CB) and spent hens (SH). Between March and June 2016, 200 retail raw chicken carcasses (100 from CB and 100 from SH) were obtained from local supermarkets in Tai’an city of China, and Salmonella isolates were then analyzed for antibiotic resistance, serotype, β-lactamase genes, and the presence of class 1 integron. Forty Salmonella strains were obtained in this study (CB: 21/100, 21%; SH: 19/100, 19%). Three serotypes were identified in 40 Salmonella, and S. Enteritidis (CB: 15/21, 71.4%; SH: 10/19, 52.6%) was the dominant serotype, followed by S. Typhimurium (CB: 4/21, 19%; SH: 6/19, 31.6%) and S. Derby (CB: 2/21, 9.5%; SH: 3/19, 15.8%). Among 21 Salmonella isolated from CB, high antibiotic resistance rates were found for ampicillin (20/21, 95.2%), nalidixic acid (18/21, 85.7%), cefotaxime (17/21, 81%), and tetracycline (13/21, 61.9%); class 1 integron was observed in seven isolates (7/21, 33.3%), and gene cassettes included an empty integron (0.15 kb, n = 1), aadA2 (1.2 kb, n = 3), drfA1-aadA1 (1.4 kb, n = 1), and drfA17-aadA5 (1.7 kb, n = 2); blaTEM-1 was the dominant β-lactamase gene (21/21, 100%), followed by blaCTX-M-55 (7/21, 33.3%). Among 19 Salmonella isolated from SH, high antibiotic resistance rates were found for nalidixic acid (19/19, 100%), tetracycline (19/19, 100%), ampicillin (18/19, 94.7%), and ciprofloxacin (13/19, 68.4%); class 1 integron was observed in two isolates (2/19, 10.5%), and gene cassettes included drfA17-aadA5 (1.7 kb, n = 1) and drfA1-aadA1 (1.4 kb, n = 1); blaTEM-1 was the dominant β-lactamase gene (19/19, 100%), followed by blaCTX-M-55 (2/19, 10.5%) and blaCMY-2 (1/19, 5.3%). Collectively, antibiotic-resistant Salmonella can be widely detected in retail raw chicken carcasses of CB and SH, and therefore can pose a serious risk to public health.
Highlights
Salmonella is a notorious human pathogen and can lead to acute intestinal disease outbreaks in humans through consumption of contaminated foods (Pegues et al, 2006)
The class 1 integrons are frequently observed among antibioticresistant Salmonella, which contributes to the spread of antibiotic resistance genes among bacteria (Wannaprasat et al, 2011)
No significant difference was found in Salmonella prevalence between commercial broilers (CB) and spent hens (SH) samples (P > 0.05)
Summary
Salmonella is a notorious human pathogen and can lead to acute intestinal disease outbreaks in humans through consumption of contaminated foods (Pegues et al, 2006). It is pivotal to use antibiotics to prevent and control Salmonella infections. The widespread use and even abuse of antibiotics in animal husbandry have facilitated the emergence and dissemination of antibiotic resistance in Salmonella, which has posed a serious challenge for the health of animals and humans (Marshall and Levy, 2011; Mukerji et al, 2017). ESBL-producing Salmonella is able to inactivate and hydrolyze the β-lactam ring in β-lactam antibiotics and third- and fourth-generation cephalosporins, leading to the increase of treatment cost and even to therapy failure, which has triggered a serious public concern (Bonnet, 2004; Pitout and Laupland, 2008). The class 1 integrons are frequently observed among antibioticresistant Salmonella, which contributes to the spread of antibiotic resistance genes among bacteria (Wannaprasat et al, 2011)
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