外源MDR鼠伤寒沙门菌对健康小鼠肠道菌群的影响

Effect of Exogenous Drug-Resistant Salmonella Typhimurium on Intestinal Flora in Healthy Mice

旨在探究外源多重耐药(multidrug resistant,MDR)鼠伤寒沙门菌进入健康小鼠肠道后对其肠道菌群的影响。将25只小鼠随机分为质控组(C)、灌胃1 d组(G1)、灌胃3 d组(G2)、灌胃5 d组(G3)和灌胃7 d组(G4),每组5只。将携带耐药基因的猪源耐药鼠伤寒沙门菌按10^(6)CFU·mL^(-1)的浓度对除质控组外的试验组小鼠进行灌胃。分别采集灌胃前第0天和灌胃结束后1~14 d的新鲜粪便样本,采用高通量测序技术分析灌胃后小鼠粪便中肠道菌群多样性变化。结果显示:1)与C组比较,各试验组在灌胃结束后临床上均表现为轻微腹泻,从粪便样本中分离出与灌胃菌同一型的MDR鼠伤寒沙门菌,且分离率差异不大;2)试验组小鼠肠道菌群Alpha多样性中Chao1、Goods_coverage和Observed_species指数明显高于C组;3)G2组、G3组和G4组在门及属水平物种丰度上变形菌门(Epsilonbacteraeota)和螺杆菌属(Helicobacteraceae)相对丰度显著低于C组(P<0.05)。在LEfSe分析上变形菌门和螺杆菌属在C组中显著富集且丰度最高。4)各试验组和C组小鼠肠道菌群中共筛选出10条代谢通路。与C组相比,G1组小鼠肠道菌群中糖原降解Ⅱ代谢通路下调,而G2组、G3组和G4组小鼠肠道菌群在硫醇生物合成、NAD生物合成Ⅱ等代谢通路显著上调(P<0.05),从而调节肠道平衡。综上,外源MDR鼠伤寒沙门菌持续感染小鼠肠道后可增加试验小鼠肠道菌群的多样性和丰富度,持续长时间灌服外源MDR鼠伤寒沙门菌可促使肠道菌群通过机体代谢通路进行调节,但由于肠道菌群本身的复杂性,菌群的自我调节及相关机制有待进一步研究。

In this study,we aimed to explore the impact of exogenous multidrug resistant(MDR)Salmonella Typhimurium on gut microbiota of healthy mice.Twenty-five mice were randomly divided into quality control group(C),one day gavage group(G1),three days gavage group(G2),five days gavage group(G3)and seven days gavage group(G4),with 5 mice in each group.Resistant Salmonella Typhimurium from swine carrying drug resistance genes was administered to mice in experimental groups except the quality control group by gavage at a concentration of 10^(6) CFU·mL^(-1).Fresh fecal samples were collected on day 0 before gavage and day 1-14 after gavage.High-throughput sequencing technology was used to analyze the diversity of gut microbiota in feces of mice after gavage.The results showed as follows:1)Compared with group C,all experimental groups showed mild diarrhea after gavage,MDR Salmonella Typhimurium was isolated from fecal samples with the same type as gavage bacteria,and there was no significant difference in the isolation rate.2)The Chao1,Goods_coverage and Observed_species indices in Alpha diversity of gut microbiota in experimental group were significantly higher than those in group C;3)The relative abundance of Epsilonbacteraeota and Helicobacteraceae at phylum and genus level in groups G2,G3 and G4 was significantly lower than that in group C(P<0.05).According to LEfSe analysis,Epsilonbacteraeota phylum and Helicobacter genus were significantly enriched and had the highest abundance in group C.4)A total of 10 metabolic pathways were screened out from the gut microbiota of mice in each experimental group and group C.Compared with group C,the glycogen degradationⅡmetabolic pathway in G1 group was down-regulated,while the thiol biosynthesis and NAD biosynthesisⅡmetabolic pathways in G2,G3 and G4 groups were significantly up-regulated(P<0.05)to regulate gut balance.In conclusion,persistent infection with MDR Salmonella Typhimurium can increase the diversity and richness of intestinal flora in mice.Long-term oral administration of MDR Salmonella Typhimurium can promote the regulation of intestinal flora through metabolic pathways.However,due to the complexity of intestinal flora itself,the self-regulation and related mechanisms of intestinal flora need to be further studied.