Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, 4 Stigbøjlen, 1870 Frederiksberg C, Denmark.
Vet Microbiol. 2013 Oct 25;166(3-4):607-16. doi: 10.1016/j.vetmic.2013.06.035. Epub 2013 Jul 11.
Salmonella enterica serovar Typhimurium phage type DT41 has previously been identified from salmonella-positive broiler breeder flocks in Denmark and isolates obtained from different flocks have demonstrated major diversity by multiple-locus variable-number tandem-repeats analysis (MLVA) typing. To elucidate whether the high diversity observed by MLVA was related to multiple independent introductions at farm level or genetic instability of markers, we investigated the genomic stability of different clones of S. Typhimurium DT41. In the in vitro genomic stability experiment, feed pellet- and dust samples inoculated with four strains of DT41 were kept at three different temperatures. The in vitro genomic stability was also assessed by conducting a serial passage experiment. In a subsequent in vivo experiment, broiler breeders of three different age groups were challenged with a strain of poultry and human origin, respectively. The in vitro experiment demonstrated that DT41 survived more than 6 months in feed-pellets at 20 °C whereas the survival in dust was less than 4 weeks. Infection pattern and excretion varied for the poultry and human strain and birds of different age groups as revealed by the in vivo experiment. Genetic stability of cultures obtained from the in vitro and in vivo survival/passage was investigated by plasmid profiling, pulsed-field gel electrophoresis (PFGE) and MLVA. The results of plasmid profiling and PFGE demonstrated genomic stability of all but one strain kept in dust at 20 °C for 3 weeks. Minor genetic changes were observed in isolates from the in vitro experiment as revealed by MLVA. The epidemiological impact of these findings is briefly discussed.
肠炎沙门氏菌血清型 Typhimurium 噬菌体 DT41 先前已从丹麦的沙门氏菌阳性种鸡群中分离出来，从不同鸡群中获得的分离株通过多位点可变数串联重复分析 (MLVA) 分型显示出主要的多样性。为了阐明 MLVA 观察到的高度多样性是否与农场水平的多次独立传入或标记的遗传不稳定性有关，我们研究了不同肠炎沙门氏菌 DT41 克隆的基因组稳定性。在体外基因组稳定性实验中，用四种 DT41 菌株接种的饲料颗粒和灰尘样本在三种不同温度下保存。还通过进行连续传代实验来评估体外基因组稳定性。在随后的体内实验中，分别用来自禽类和人类的一株肠炎沙门氏菌 DT41 对三个不同年龄组的种鸡进行攻毒。体外实验表明，DT41 在 20°C 的饲料颗粒中存活时间超过 6 个月，而在灰尘中的存活时间不到 4 周。体内实验表明，禽源和人源菌株的感染模式和排泄情况以及不同年龄组的禽类均有所不同。通过质粒图谱分析、脉冲场凝胶电泳 (PFGE) 和 MLVA 研究了从体外和体内存活/传代获得的培养物的遗传稳定性。质粒图谱分析和 PFGE 的结果表明，除了在 20°C 下保存 3 周的尘埃中的一株外，所有菌株的基因组均保持稳定。MLVA 显示，体外实验分离株存在微小的遗传变化。简要讨论了这些发现的流行病学影响。
