Fu Ying, Xu Xuebin, Zhang Lina, Xiong Zhiying, Ma Yeben, Wei Yihuan, Chen Zhengquan, Bai Jie, Liao Ming, Zhang Jianmin
National and Regional Joint Engineering Laboratory for Medicament of Zoonoses Prevention and Control, Guangdong Laboratory for Lingnan Modern Agriculture, Laboratory of Veterinary Vaccine Innovation of the Ministry of Agriculture, Key Laboratory of Zoonosis Prevention and Control of Guangdong Province, College of Veterinary Medicine, South China Agricultural University, Guangzhou, China.
Shanghai Municipal Center for Disease Control and Prevention, Shanghai, China.
Front Microbiol. 2020 May 15;11:910. doi: 10.3389/fmicb.2020.00910. eCollection 2020.
In this study, we investigated the pattern of antimicrobial resistance in enterica serotype Enteritidis isolates in Shanghai, China from 2005 to 2014. We found the first isolates with resistance to the fourth-generation cephalosporin cefepime starting in 2010. Furthermore, we analyzed the epidemic characteristics and mechanisms of underlying cefepime resistance in Enteritidis isolates found from 2010. In total, 38 of 2,914 (1.30%) isolates were identified as cefepime-resistant Enteritidis (CRSE) isolates by Kirby-Bauer disk diffusion. Two isolates were from animal derived food sources; 36 isolates were from fecal samples of human patients with salmonellosis. Antimicrobial susceptibility testing using the agar dilution method revealed that all CRSE isolates showed additional resistances at least to ceftazidime, cefotaxime, and ampicillin. Additionally, pulsed-field gel electrophoresis (PFGE) profiles indicated that 89.47% of CRSE isolates also displayed similar PFGE patterns. Five types of β-lactamase genes, (100.00%, 38/38), (65.79%, 25/38), (52.63%, 20/38), (18.42%, 7/38), and (5.26%, 2/38) were detected by PCR and sequencing. Among genes, was the dominant type (84.21%, 32/38). Conjugation and transformation experiments along with plasmid replicon typing revealed that was located on plasmids of various replicon types with sizes ranging from 76.8 to 138.9 kb. Plasmid sequence analysis also showed that the gene was mobilized mainly by the IS- -ORF477 transposition unit and had its own IS-based promoter, which accelerated the expression and transmission of . Analysis of whole genome sequences (Illumina) of one selected transformant SH12G706-C showed high similarity of the carrying plasmid with the IncI1 plasmid backbone p628-CTX-M of detected in 2010 in China. The present study demonstrated that the gene mobilized by IS- -ORF477 was the main feature shared by CRSE isolates and seems to play an important role for transmission of cefepime resistance. The number of CRSE isolates is rising annually, and the strong dissemination ability of IS- -ORF477-harboring plasmids among different species represents an important threat to the therapeutic effectiveness of cefepime.
在本研究中，我们调查了2005年至2014年中国上海肠炎沙门氏菌肠炎血清型分离株的抗菌药物耐药模式。我们发现从2010年开始出现了对第四代头孢菌素头孢吡肟耐药的首批分离株。此外，我们分析了2010年分离出的肠炎沙门氏菌分离株中头孢吡肟耐药的流行特征及潜在机制。通过Kirby-Bauer纸片扩散法，在2914株分离株中，共有38株（1.30%）被鉴定为对头孢吡肟耐药的肠炎沙门氏菌（CRSE）分离株。2株分离株来自动物源性食物；36株分离株来自沙门氏菌病患者的粪便样本。采用琼脂稀释法进行的药敏试验显示，所有CRSE分离株至少对头孢他啶、头孢噻肟和氨苄西林也表现出额外耐药。此外，脉冲场凝胶电泳（PFGE）图谱表明，89.47%的CRSE分离株也显示出相似的PFGE模式。通过PCR和测序检测到5种β-内酰胺酶基因，分别为blaCTX-M（100.00%，38/38）、blaSHV（65.79%，25/38）、blaTEM（52.63%，20/38）、blaCMY（18.42%，7/38）和blaOXA（5.26%，2/38）。在blaCTX-M基因中，blaCTX-M-15是主要类型（84.21%，32/38）。接合和转化实验以及质粒复制子分型显示，blaCTX-M-15位于各种复制子类型的质粒上，大小范围为76.8至138.9 kb。质粒序列分析还表明，blaCTX-M基因主要由IS26-ORF477转座单元转移，并有其自身基于IS的启动子，这加速了blaCTX-M的表达和传播。对一株选定的转化子SH12G706-C的全基因组序列（Illumina）分析显示，携带blaCTX-M的质粒与2010年在中国检测到的IncI1质粒骨架p628-CTX-M具有高度相似性。本研究表明，由IS26-ORF477转移的blaCTX-M基因是CRSE分离株共有的主要特征，似乎在头孢吡肟耐药性传播中起重要作用。CRSE分离株的数量逐年上升，携带IS26-ORF477的质粒在不同物种间的强大传播能力对头孢吡肟的治疗效果构成了重要威胁。
