腹泻儿童与非腹泻儿童肠道携带超广谱β-内酰胺酶阳性不动杆菌特征研究

Characteristics of ESBLs-positive Acinetobacter strains in children with and without diarrhea

目的分析腹泻儿童与非腹泻儿童肠道定植超广谱β-内酰胺酶(extended-spectrumβ-lactamases,ESBLs)阳性不动杆菌的耐药特征、基因组信息和遗传关系等,以探究2组ESBLs阳性不动杆菌携带情况与菌株特征差异。方法2017—2019年在上海某医院采集腹泻儿童和非腹泻儿童的新鲜粪便样品共842份,分离培养、鉴定所携带ESBLs阳性不动杆菌,对分离菌株进行药敏实验和全基因组测序,并构建系统进化树探究本研究所获得鲍曼不动杆菌与中国同期分离的鲍曼不动杆菌的遗传关系。结果共分离出13株ESBLs阳性不动杆菌,其中腹泻儿童11株、非腹泻儿童2株,腹泻组分离阳性率显著高于非腹泻组,差异有统计学意义(χ^(2)=5.206,P=0.023)。药敏结果显示,所有菌株均对一代头孢(100.0%)和二代头孢(100.0%)耐药;多重耐药率为53.8%(7/13),2组儿童对各药物的耐药率及多重耐药率差异均无统计学意义(P>0.05)。所有菌株均携带位于染色体上的blaOXA基因,该基因可编码相应的酶水解三代头孢类和碳青霉烯类等临床重要抗生素。92.3%(12/13)的菌株携带黏附类毒力基因、84.6%(11/13)的菌株携带分泌类毒力基因。92.3%(12/13)的ESBLs阳性不动杆菌携带质粒,其中,分离自非腹泻儿童的1株鲍曼不动杆菌携带7种质粒。系统进化树结果显示,本研究所分离的鲍曼不动杆菌菌株进化关系较近,并与同时期中国南方地区部分菌株形成一个克隆簇。结论腹泻儿童与非腹泻儿童分离的ESBLs阳性不动杆菌的耐药情况严重,携带多种耐药和毒力基因,且携带多种质粒,这增加了耐药基因和毒力基因的水平传播风险,提示我们需关注儿童肠道中的ESBLs阳性不动杆菌,加强对健康儿童肠道耐药菌的监测。

Objective To analyze the drug resistance,genomic information,and genetic relationships of Extended-Spectrumβ-Lactamases(ESBLs)-positive Acinetobacter strains colonized in the intestinal tract of children with and without diarrhea,and to explore the carrying status and distinguishing features of two group ESBLs-positive Acinetobacter strains.Methods A total of 842 fresh fecal samples were collected from children with and without diarrhea from a hospital in Shanghai,2017-2019.ESBLs-resistant Acinetobacter strains were isolated and identified,followed by a drug sensitivity test and whole genome sequencing.A phylogenetic tree was constructed to explore the genetic relationship between Acinetobacter baumannii strains in this study and those isolated in China during the same period.Results A total of 13 ESBLs-positive Acinetobacter strains were isolated,including 11 strains in the diarrhea group and two strains in the non-diarrhea group,the positive rate of ESBLs strains in the diarrhea group was significantly higher than that in the non-diarrhea group(χ^(2)=5.206,P=0.023).All strains showed a high resistance rate to the first-generation cephalosporins(100.0%)and the second-generation cephalosporins(100.0%),with a multidrug resistance rate of 53.8%(7/13).There was no significant difference in the rates of resistance to individual antibiotics and multidrug resistance between the two groups(P>0.05).The blaOXA resistance gene was carried by all strains on the chromosome,which encode enzymes that hydrolyze clinically important antibiotics such as thirdgeneration cephalosporins and carbapenems.Adhesion-type virulence genes were carried by 92.3%(12/13)of the strains,and secretion-type virulence genes were present in 84.6%(11/13).Furthermore,92.3%(12/13)of ESBLs-positive Acinetobacter strains carried plasmids,with one A.baumannii strain isolated from a non-diarrhea child carrying seven types of plasmids.The analysis of the phylogenetic relationship indicated that A.baumannii strains isolated in this study formed a clonal cluster,and also clustered with some strains from southern China during the same period.Conclusions ESBLs-positive Acinetobacter strains isolated from children with and without diarrhea exhibited serious drug resistance,carrying multiple resistance and virulence genes,as well as multiple plasmids.Carrying multiple plasmids may facilitate the horizontal transmission risk of drug-resistance genes and virulence genes,indicating the need to pay attention to the characteristics of intestinal colonized ESBLs-positive Acinetobacter strains in children and strengthen the monitoring of drug-resistant bacteria colonized in the intestine in healthy children.