Carriage of the mcr-9 and mcr-10 genes in clinical strains of the Enterobacter cloacae complex in China: a prevalence and molecular epidemiology study

作者：Zhou, Hongwei; Wang, Siheng; Wu, Yuchen; Dong, Ning; Ju, Xiaoyang; Cai, Chang; Li, Ruichao; Li, Yan; Liu, Congcong; Lu, Jiayue; Chan, Edward Wai-Chi; Chen, Sheng^*; Zhang, Rong; Shen, Zhangqi^*

来源：International Journal of Antimicrobial Agents, 2022, 60(4): 106645.

DOI：10.1016/j.ijantimicag.2022.106645

• mcr-9
• mcr-10
• Enterobacter cloacae complex
• Colistin
• Carbapenem-resistant Enterobacteriaceae
• Epidemiology

Objectives: Enterobacter cloacae complex (ECC) is among the most common carbapenem-resistant Enter-obacteriaceae (CRE) in China. The emergence of mcr has rendered CRE strains resistant to the last-line antibiotic colistin. This study investigated the prevalence of mcr-9 and mcr-10 in carbapenem-resistant ECC (CRECC) and carbapenem-susceptible ECC (CSECC) in China.Methods: The CRECC and CSECC strains were collected from different regions of China. Antimicrobial sus-ceptibility tests, conjugation experiments, whole genome sequencing, bioinformatic analysis, and quanti-tative RT-PCR were performed to understand the mechanisms of resistance and transmission of mcr in ECC.Results: A total of 534 ECC were collected, among which 57 (10.7%) and 23 (4.3%) were positive for mcr-9 and mcr-10, respectively. The prevalence of mcr-9 in CRECC was significantly higher than that in CSECC (31.8% vs. 3.7%; P < 0.001), while the prevalence of mcr-10 in CRECC was significantly lower (0.8% vs. 5.5%; P < 0.05). Most mcr-9-positive strains ( n = 45, 78.9%) exhibited multidrug-resistant phenotype, and four (17.4%) of the mcr-10-positive strains exhibited multi-drug resistance. Coexistence of mcr and car-bapenemase genes was commonly observed, including 41 (71.9%) mcr-9-positive strains and one (4.3%) mcr-10-positive strain, and the possibility of co-transfer was confirmed by conjugation experiments. The mcr-positive ECC were highly diverse, while most mcr genes were plasmid-encoded, indicating the im-portant role of plasmids in the transmission of mcr in ECC. Furthermore, the expression of mcr-9 was increased after induction by colistin.Conclusions: The widespread mcr genes and co-transfer with carbapenemase genes among ECC strains pose an urgent threat to public health.

• 单位
  苏州大学; 浙江农林大学; 浙江大学; 中国农业大学