老年病房耐亚胺培南鲍曼不动杆菌整合子及分子流行病学研究

Study on the integrons and molecular epidemiology of Acinetobacter baumannii isolates resistant to imipenem in geriatric ward

目的了解老年病房耐亚胺培南鲍曼不动杆菌携带整合子的情况,分析菌株同源性,为防治院内感染提供依据。方法收集我院老年科2014年3月至2017年3月临床分离的非重复耐亚胺培南鲍曼不动杆菌28株,采用纸片扩散法确定其耐药率,运用聚合酶链式反应(PCR)法检测整合酶基因(intl)Ⅰ、intlⅡ、intlⅢ及可变区,并用多位点序列分型(MLST)法对其进行分子分型。结果耐亚胺培南鲍曼不动杆菌intlⅠ的携带率为35.7%,未扩增出Ⅱ类和Ⅲ类intl。整合子阳性菌扩增出两类可变区,分别含有aac C1-orfx'-aadA1及aac A4-catB8-aad A1基因盒。MLST分型提示ST1415型14株(50.0%)、ST1417型5株(17.9%)、ST195型4株(14.3%)、ST540型3株(10.7%),未分型2株。MLST优势基因型为ST1415。结论耐亚胺培南鲍曼不动杆菌主要携带Ⅰ类整合子,介导对氨基糖苷类、氯霉素耐药。老年病房存在耐亚胺培南鲍曼不动杆菌,尤其是ST1415型的院内感染流行,必须加强感染隔离及控制。

Objective To study the integrons in Acinetobacter baumannii isolates resistant to imipenem from geriatric ward,and to explore the molecular epidemiology.Methods Twenty-eight strains of nonduplicate clinical strains were isolated from April 2014 to August 2017,and K-B disk diffuse method was used for insusceptibility testing.Polymerase chain reaction amplification and DNA sequencing were used to analyze intl Ⅰ,intl Ⅱ,intl Ⅲ and variable region.Moreover,multi-locus sequence typing（MLST） was used to confirm molecular type.Results The positive rate of class Ⅰintegron was 35.7%,and there were no positive results of class Ⅱ and class Ⅲ integron genes.Two different stripes variable areas were applied by the positive strains of integron,which respectively contained aacC1-orfx＇-aadA1 and aacA4-catB8-aadA1.Four kinds of STs such as ST 1415（50.0%） 、ST1417（17.9%） 、ST 195（14.3%） 、ST 540（10.7%） were detected by MLST.Two strains were not classified,and ST1415 was the predominant genotype among 28 strains.Conclusions ClassⅠintegron widely exists in the isolates of Acinetobacter baumannii resistant to imipenem in geriatric ward,which mainly mediates resistance to chloramphenicol and sulfonamide.The results of MLST suggest spread of Acinetobacter baumanni resistant to imipenem,especially ST 1415 exists in geriatric ward.We must strengthen infection isolation and control.