Mahidol International Dental School, Faculty of Dentistry, Mahidol University, Bangkok, Thailand.
Department of Microbiology, Faculty of Science, Pornchai Matangkasombut Center for Microbial Genomics, Mahidol University, Bangkok, Thailand.
Sci Rep. 2023 May 1;13(1):7080. doi: 10.1038/s41598-023-34242-4.
S. 4,[5],12:i:-, a monophasic variant of S. enterica serovar Typhimurium, is an important multidrug resistant serovar. Strains of colistin-resistant S. 4,[5],12:i:- have been reported in several countries with patients occasionally had recent histories of travels to Southeast Asia. In the study herein, we investigated the genomes of S. 4,[5],12:i:- carrying mobile colistin resistance (mcr) gene in Thailand. Three isolates of mcr-3.1 carrying S. 4,[5],12:i:- in Thailand were sequenced by both Illumina and Oxford Nanopore platforms and we analyzed the sequences together with the whole genome sequences of other mcr-3 carrying S. 4,[5],12:i:- isolates available in the NCBI Pathogen Detection database. Three hundred sixty-nine core genome SNVs were identified from 27 isolates, compared to the S. Typhimurium LT2 reference genome. A maximum-likelihood phylogenetic tree was constructed and revealed that the samples could be divided into three clades, which correlated with the profiles of fljAB-hin deletions and plasmids. A couple of isolates from Denmark had the genetic profiles similar to Thai isolates, and were from the patients who had traveled to Thailand. Complete genome assembly of the three isolates revealed the insertion of a copy of IS26 at the same site near iroB, suggesting that the insertion was an initial step for the deletions of fljAB-hin regions, the hallmark of the 4,[5],12:i:- serovar. Six types of plasmid replicons were identified with the majority being IncA/C. The coexistence of mcr-3.1 and bla was found in both hybrid-assembled IncA/C plasmids but not in IncHI2 plasmid. This study revealed possible transmission links between colistin resistant S. 4,[5],12:i:- isolates found in Thailand and Denmark and confirmed the important role of plasmids in transferring multidrug resistance.
血清型 4,[5],12:i:-，肠炎沙门氏菌的一个单相变体，是一种重要的多药耐药血清型。具有多粘菌素耐药性的 4,[5],12:i:-菌株已在多个国家报道，这些国家的患者偶尔有近期前往东南亚旅行的病史。在本研究中，我们对泰国携带移动多粘菌素耐药（mcr）基因的 4,[5],12:i:-进行了基因组研究。通过 Illumina 和 Oxford Nanopore 平台对泰国的 3 株 mcr-3.1 携带的 4,[5],12:i:-进行了测序，并与 NCBI 病原体检测数据库中可获得的其他 mcr-3 携带 4,[5],12:i:-的全基因组序列进行了分析。与肠炎沙门氏菌 LT2 参考基因组相比，从 27 株分离株中鉴定出 369 个核心基因组 SNV。构建了最大似然系统发育树，结果表明，这些样本可分为三个分支，与 fljAB-hin 缺失和质粒的图谱相关。来自丹麦的一对分离株与泰国分离株具有相似的遗传特征，且来自去过泰国的患者。对这 3 株分离株的全基因组组装表明，在iroB 附近的相同位点插入了一个 IS26 的拷贝，提示该插入是 fljAB-hin 区缺失的初始步骤，这是 4,[5],12:i:-血清型的标志。鉴定出 6 种质粒复制子，其中大多数为 IncA/C。mcr-3.1 和 bla 共存于两种杂交组装的 IncA/C 质粒中，但不存在于 IncHI2 质粒中。本研究揭示了在泰国和丹麦发现的耐多粘菌素 4,[5],12:i:-分离株之间可能存在传播联系，并证实了质粒在转移多药耐药性方面的重要作用。
