Guangdong Key Laboratory for Veterinary Drug Development and Safety Evaluation, College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China.
Quadram Institute Bioscience, Norwich Research Park, Norwich, Norfolk NR4 7UA, UK; Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich, Norfolk, NR4 7TJ, UK.
Vet Microbiol. 2021 Feb;253:108944. doi: 10.1016/j.vetmic.2020.108944. Epub 2020 Dec 14.
The aim of this study was to explore the characteristics of bla carriage and mobilization in Salmonella and Escherichia coli isolates from food-producing animals in China. A total of 2280 E. coli and 229 Salmonella isolates collected from food animals from June 2003 to September 2014 were screened for the presence of bla gene. The bla-positive isolates were typed and plasmid DNA sequenced to determine the genetic context of bla and plasmid types present. Bacterial fitness was evaluated by growth curve and plasmid stability in vitro. CTX-M-27-positive E. coli (18, 0.79 %) and Salmonella (34, 14.85 %) were detected. PFGE profiles of CTX-M-27-positive strains revealed a wide variety of genotypes and S. Indiana was the most prevalent serotype. Replicon typing, S1-PFGE and hybridization of CTX-M-27-carrying plasmids confirmed that bla gene was located on IncFII (12/18), IncN (4/18), and non-typeable (2/18) plasmids in E. coli and on P1-like bacteriophage (21/34), IncP (4/34), IncFIB (4/34), IncN (2/34), IncHI2 (2/34), and IncA/C (1/34) plasmids in Salmonella. Comparison and analysis of gene context of bla in P1-like bacteriophage and plasmids revealed they shared the same structure and contained an identical genetic context with the Tn1721-like structure ΔISEcp1B-bla-IS903D-iroN-Δmap-Tn1721. In addition, plasmid stability tests indicated that the bla P1-like bacteriophage were more stable than plasmids in the absence of cefotaxime selective pressure. These results demonstrate that Tn1721-like transposons harboring CTX-M-27 could be mobilized between different plasmids in E. coli and P1-like bacteriophage disseminated among Salmonella.
本研究旨在探索中国食源性动物分离的沙门氏菌和大肠杆菌中 bla 基因携带和移动的特征。从 2003 年 6 月至 2014 年 9 月期间采集的食源性动物中，共筛选了 2280 株大肠杆菌和 229 株沙门氏菌，以检测 bla 基因的存在。对 bla 阳性分离株进行了分型和质粒 DNA 测序，以确定 bla 基因和质粒类型的遗传背景。通过体外生长曲线和质粒稳定性评估细菌的适应性。检测到 CTX-M-27 阳性大肠杆菌（18 株，0.79%）和沙门氏菌（34 株，14.85%）。CTX-M-27 阳性菌株的 PFGE 图谱显示了多种基因型，其中印第安纳沙门氏菌是最常见的血清型。复制子分型、S1-PFGE 和 CTX-M-27 携带质粒的杂交证实，bla 基因位于大肠杆菌的 IncFII（12/18）、IncN（4/18）和不可分型（2/18）质粒上，以及 P1 样噬菌体（21/34）、IncP（4/34）、IncFIB（4/34）、IncN（2/34）、IncHI2（2/34）和 IncA/C（1/34）质粒上。对 P1 样噬菌体和质粒中 bla 基因的上下文进行比较和分析，发现它们具有相同的结构，并且与 Tn1721 样结构 ΔISEcp1B-bla-IS903D-iroN-Δmap-Tn1721 具有相同的遗传背景。此外，质粒稳定性试验表明，在没有头孢噻肟选择压力的情况下，bla P1 样噬菌体比质粒更稳定。这些结果表明，携带 CTX-M-27 的 Tn1721 样转座子可以在大肠杆菌中的不同质粒之间以及 P1 样噬菌体在沙门氏菌中传播。
