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Abstract
Purpose
Human infections caused by invasive non-typhoidal Salmonella (iNTS) are highly prevalent worldwide. However, data for such infections in China are scarce. This study reports the epidemiology of iNTS in China.
Methods
INTS isolates were recovered from blood and other clinical specimens collected during 2007–2016 across five provinces (Shanghai, Xinjiang, Fujian, Guangxi, and Chongqing) in China. Antimicrobial susceptibility was performed using the agar dilution method and molecular epidemiology was performed using standard microbiological techniques.
Results
A total of 178 iNTS isolates were recovered from approximately 9700 patient specimens during 2007–2016. The predominant serovars were Salmonella Enteritidis (57/178, 32%), Salmonella Choleraesuis (47/178, 26.4%), and Salmonella Typhimurium (24/178, 13.5%). Up to 50 isolates (28.1%) were from patients who were ≤1 year of age, while 28 (15.7%) were from patients who were ≥60 years. Among these isolates, high rates of resistance to nalidixic acid (114/178, 64%), sulfisoxazole (59%), ciprofloxacin (15.2%), and cefotaxime (8.4%) were found. Moreover, 53.4% (95/178) exhibited multidrug resistance, and 3.9% (7/178) showed co-resistance to third-generation cephalosporins and ciprofloxacin. Steadily increasing numbers of nalidixic acid, cefotaxime, and ciprofloxacin-resistant isolates, but decreasing numbers of multidrug resistance isolates were detected during the study period. Detection of quinolone genes in 114 nalidixic acid-resistant isolates showed that 58.3% (67/114) harbored plasmid-mediated quinolone resistance (PMQR) genes [aac(6´)-Ib-cr, qnrA, qnrB, oqxAB, qepA, qnrS, and qnrD] and 98.2% (112/114) exhibited mutations in quinolone resistance determining regions [gyrA, parC, and parE]. Furthermore, we detected beta-lactamases genes in the ceftriaxone-resistant isolates. The most common were blaTEM-1 (93.3%), followed by blaCTX-M-55 (40%), blaCMY-2 (33.3%), and blaOXA-1 (33.3%). Finally, a range of pulsed-field gel electrophoresis patterns were detected among the Salmonella Enteritidis and Salmonella Typhimurium isolates.
Conclusion
High rates of multidrug resistance and steadily increasing cefotaxime and ciprofloxacin-resistant iNTS could pose a significant challenge for the effective treatment of salmonellosis in China.
Acknowledgment
This work was supported by the National Key R&D Program of China (2017YFC1600101, 2017YFC1600104, 2018YFD0500500), a project supported by National Natural Science Foundation of China (31972762), a project supported by Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme (2018), the Pearl River S&T Nova Program of Guangzhou (201806010183), the Province Science and Technology of Guangdong Research Project (2017A020208055), Walmart Foundation (SA1703162), and National Broiler Industry Technology System Project (cARS-41-G16).
Author contributions
Zhen Gu, Xiayidan Wufuer, Mingliu Wang, Meilian Huang, Jianhui Chen, Chunmei Jing and Xuebin Xu collected the clinical samples. Ming Liao, Jianmin Zhang and Mei Zeng designed the study. Zeqiang Zhan., Zhiying Xiong, Jianmin Zhang and Xuebin Xu carried out the experiment. Jianghong Meng, Zeqiang Zhan, Ming Liao, Jianmin Zhang and Mei Zeng analyzed the data. Zeqiang Zhan, Ming Liao, Jianmin Zhang and Mei Zeng and Xuebin Xu prepared the manuscript. All authors contributed to data analysis, drafting and revising the article, gave final approval of the version to be published, and agree to be accountable for all aspects of the work.
Disclosure
The authors report no conflicts of interest in this work.