Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
WHO Collaborating Centre for Antimicrobial Resistance in Food-borne Pathogens and EU Reference Laboratory for Antimicrobial Resistance, National Food Institute, Technical University of Denmark, Kgs Lyngby, Denmark.
J Med Microbiol. 2014 Mar;63(Pt 3):331-342. doi: 10.1099/jmm.0.068221-0. Epub 2013 Dec 9.
Comparison of the publicly available genomes of the virulent Salmonella enterica serovar Typhimurium (S. Typhimurium) strains SL1344, 14028s and D23580 to that of the virulence-attenuated isolate LT2 revealed the absence of a full sequence of bacteriophage ST64B in the latter. Four selected ST64B regions of unknown function (sb7-sb11, sb46, sb49-sb50 and sb54) were mapped by PCR in two strain collections: (i) 310 isolates of S. Typhimurium from human blood or stool samples, and from food, animal and environmental reservoirs; and (ii) 90 isolates belonging to other serovars. The region sb49-sb50 was found to be unique to S. Typhimurium and was strongly associated with strains isolated from blood samples (100 and 28.4 % of the blood and non-blood isolates, respectively). The region was cloned into LT2 and knocked out in SL1344, and these strains were compared to wild-type isogenic strains in in vitro assays used to predict virulence association. No difference in invasion of the Int407 human cell line was observed between the wild-type and mutated strains, but the isolate carrying the whole ST64B prophage was found to have a slightly better survival in blood. The study showed a high prevalence and a strong association between the prophage ST64B and isolates of S. Typhimurium collected from blood, and may indicate that such strains constitute a selected subpopulation within this serovar. Further studies are indicated to determine whether the slight increase in blood survival observed in the strain carrying ST64B genes is of paramount importance for systemic infections.
将毒力减弱的伤寒沙门氏菌 LT2 与强毒株 SL1344、14028s 和 D23580 的基因组序列进行比较，发现 LT2 中缺失了完整的噬菌体 ST64B 序列。通过 PCR 对四个未知功能的 ST64B 区域（sb7-sb11、sb46、sb49-sb50 和 sb54）进行了定位，这些区域分别存在于 310 株来自人类血液或粪便样本、食物、动物和环境来源的鼠伤寒沙门氏菌分离株以及 90 株来自其他血清型的分离株中。sb49-sb50 区域仅存在于鼠伤寒沙门氏菌中，与从血液样本中分离出的菌株高度相关（分别为血液和非血液分离株的 100%和 28.4%）。将该区域克隆到 LT2 中并敲除 SL1344 中的该区域，然后将这些菌株与野生型等基因株在体外试验中进行比较，用于预测毒力相关性。在体外试验中，野生型和突变菌株对 Int407 人细胞系的侵袭能力没有差异，但携带完整 ST64B 噬菌体的分离株在血液中的存活率略高。研究表明，强毒株 ST64B 与从血液中分离出的鼠伤寒沙门氏菌分离株的高流行率和强相关性，可能表明这些菌株构成了该血清型的一个选择亚群。需要进一步的研究来确定携带 ST64B 基因的菌株在血液中的存活率略有增加是否对全身感染至关重要。
