Ⅵ型分泌系统在鲍曼不动杆菌致病及耐药性中的作用

Role of typeⅥsecretion system in the pathogenicity and antibiotic resistance of Acinetobacter baumanii

目的研究Ⅵ型分泌系统(typeⅥsecretion system,T6SS)在鲍曼不动杆菌致病性和耐药性中的作用。方法收集2016年1月1日至12月31日温州医科大学附属第一医院分离自血流感染患者血液标本的45株鲍曼不动杆菌株,采用VITEK 2 Compact全自动微生物分析仪测定其对抗菌药物的敏感性,通过聚合酶链反应检测菌株T6SS主要效应蛋白编码基因溶血素调节蛋白的携带情况,对T6SS阳性鲍曼不动杆菌和T6SS阴性鲍曼不动杆菌分别进行生物膜形成能力检测、抗血清试验和体外竞争试验,收集并分析鲍曼不动杆菌血流感染患者的临床资料及转归情况。统计学分析采用t检验、秩和检验和χ2检验。结果45株鲍曼不动杆菌中24株T6SS阳性,阳性率为53.3%。T6SS阳性鲍曼不动杆菌对头孢他啶、环丙沙星、庆大霉素、亚胺培南、左氧氟沙星、哌拉西林/他唑巴坦、妥布霉素和头胞吡肟的耐药率分别为95.8%、95.8%、66.7%、95.8%、79.2%、95.8%、79.2%和91.7%,高于T6SS阴性鲍曼不动杆菌的28.6%、28.6%、28.6%、28.6%、9.5%、23.8%、23.8%和28.6%,差异均有统计学意义(χ^2=22.12、22.12、6.51、22.12、21.83、24.72、13.79、18.97,均P<0.05)。T6SS阳性鲍曼不动杆菌的生物膜形成能力、血清抗性和竞争能力均高于T6SS阴性鲍曼不动杆菌,差异均有统计学意义(t=4.99、Z=-2.61、Z=-2.27,均P<0.05)。重症监护病房(intensive care unit,ICU)来源鲍曼不动杆菌的T6SS阳性率为80.0%(16/20),高于非ICU来源菌株的32.0%(8/25),差异均有统计学意义(χ^2=10.29,P<0.05),但鲍曼不动杆菌是否携带T6SS对患者病死率的影响差异无统计学意义(χ^2=1.74,P=0.188)。结论T6SS阳性鲍曼不动杆菌具有较高的致病性,且其高耐药率使得治疗较困难,亟需引起临床医师尤其是ICU医师的高度重视。

Objective To investigate the role of typeⅥsecretion system(T6SS)in the pathogenicity and antibiotic resistance of Acinetobacter baumanii.Methods From January 1 to December 31,2016,a total of 45 Acinetobacter baumanii isolates were collected from patients with bloodstream infection in the First Affiliated Hospital of Wenzhou Medical University.The susceptibilities to commonly used antimicrobial agents were determined by VITEK 2 Compact automatic microbiology analyzer.Detection of T6SS characteristic gene hemolysin coregulated protein(hcp)was achieved by polymerase chain reaction.Biofilm formations,serum resistances and competition tests of T6SS-positive/negative Acinetobacter baumanii were performed in vitro.The clinical data of patients with bloodstream infection were collected and analyzed.Chi-square test,t test and Kruskal-Wallis test were conducted for statistical analysis.Results The positive rate of T6SS in 45 Acinetobacter baumanii isolates was 53.3%(24/45).The resistance rates of T6SS-positive Acinetobacter baumanii to ceftazidime,ciprofloxdcin,gentamicin,imipenem,levofloxacin,piperacillin/tazobactam,tobramycin and cefepime(95.8%,95.8%,66.7%,95.8%,79.2%,95.8%,79.2%,91.7%)were all higher than that of T6SS-negative Acinetobacter baumanii(28.6%,28.6%,28.6%,28.6%,9.5%,23.8%,23.8%,28.6%),and the differences were all statistically significant(χ^2=22.12,22.12,6.51,22.12,21.83,24.72,13.79,18.97,respectively,all P<0.05).The biofilm formation ability,serum resistance and competitive ability of T6SS-positive Acinetobacter baumanii were stronger than those of T6SS-negative Acinetobacter baumanii,and the differences were all statistically significant(t=4.99,Z=-2.61 and-2.27,respectively,all P<0.05).The positive rate of T6SS isolated from intensive care unit(ICU)ward(80.0%,16/20)was significantly higher than that from non-ICU ward(32.0%,8/25;χ^2=10.29,P<0.05).But T6SS had no effect on the prognosis of patients(χ^2=1.74,P=0.188).Conclusions T6SS of Acinetobacter baumanii is associated with high pathogenicity,and the high drug resistance rate makes treatment extremely difficult.Physicians need to pay much attention,especially to the patients from ICU wards.