Stella A E, Luz D, Piazza R M F, Spira B
Universidade Federal de Goiás,Regional Jataí,Goiás,Brazil.
Instituto Butantan, Laboratório de Bacteriologia,Av. Vital Brasil, 1500,Butantã,São Paulo,São Paulo,Brazil.
Epidemiol Infect. 2017 Aug;145(11):2204-2211. doi: 10.1017/S0950268817001091. Epub 2017 Jun 7.
Shiga toxin-producing Escherichia coli (STEC) is a known food pathogen, which main reservoir is the intestine of ruminants. The abundance of different STEC lineages in nature reflect a heterogeneity that is characterised by the differential expression of certain genotypic characteristics, which in turn are influenced by the environmental conditions to which the microorganism is exposed. Bacterial homeostasis and stress response are under the control of the alarmone guanosine tetraphosphate (ppGpp), which intrinsic levels varies across the E. coli species. In the present study, 50 STEC isolates from healthy sheep were evaluated regarding their ppGpp content, cytotoxicity and other relevant genetic and phenotypic characteristics. We found that the level of ppGpp and cytotoxicity varied considerably among the examined strains. Isolates that harboured the stx2 gene were the least cytotoxic and presented the highest levels of ppGpp. All stx2 isolates belonged to phylogroup A, while strains that carried stx1 or both stx1 and stx2 genes pertained to phylogroup B1. All but two stx2 isolates belonged to the stx2b subtype. Strains that belonged to phylogroup B1 displayed on average low levels of ppGpp and high cytotoxicity. Overall, there was a negative correlation between cytotoxicity and ppGpp.
产志贺毒素大肠杆菌（STEC）是一种已知的食源性病原体，其主要储存宿主是反刍动物的肠道。自然界中不同STEC谱系的丰度反映了一种异质性，其特征在于某些基因型特征的差异表达，而这些特征又受到微生物所暴露环境条件的影响。细菌的稳态和应激反应受警报素四磷酸鸟苷（ppGpp）的控制，其内在水平在不同大肠杆菌种类中有所不同。在本研究中，对来自健康绵羊的50株STEC分离株的ppGpp含量、细胞毒性以及其他相关的遗传和表型特征进行了评估。我们发现，在所检测的菌株中，ppGpp水平和细胞毒性差异很大。携带stx2基因的分离株细胞毒性最低，ppGpp水平最高。所有stx2分离株均属于A系统发育群，而携带stx1或同时携带stx1和stx2基因的菌株属于B1系统发育群。除两株stx2分离株外，其余均属于stx2b亚型。属于B1系统发育群的菌株平均显示出低水平的ppGpp和高细胞毒性。总体而言，细胞毒性与ppGpp之间呈负相关。
