Kim Jungok, Lee Ji-Young, Lee Haejeong, Choi Ji Young, Kim Dae Hun, Wi Yu Mi, Peck Kyong Ran, Ko Kwan Soo
a Division of Infectious Diseases, Department of Internal Medicine , Chungnam National University School of Medicine , Daejeon , South Korea.
b Department of Molecular Cell Biology , Sungkyunkwan University School of Medicine , Suwon , South Korea.
Virulence. 2017 Oct 3;8(7):1378-1389. doi: 10.1080/21505594.2017.1323164. Epub 2017 Apr 27.
We investigated the genetic background and microbiological features of T6SS-positive Acinetobacter baumannii isolates and clinical impact of the T6SS in patients with A. baumannii bacteremia. One hundred and 62 A. baumannii isolates from patients with bacteremia in 2 tertiary-care hospitals in Korea were included in this study. Approximately one-third (51/162, 31.5%) of the A. baumannii clinical isolates possessed the hcp gene, and the hcp-positive isolates were found in several genotypes in multilocus sequence typing. The expression and secretion of Hcp protein varied among the clinical isolates. A. baumannii isolates with detectable Hcp secretion (T6SS+) could better outcompete Escherichia coli compared with T6SS- isolates, including hcp-negative and inactivated hcp-positive isolates. In addition, T6SS+ isolates showed higher biofilm-forming activity and better survival in the presence of normal human serum than the T6SS- isolates. T6SS+ isolates were more frequently detected in patients with catheter-related bloodstream infection, haematopoietic stem cell transplant recipients, and patients receiving immunosuppressive agents. However, T6SS was not a prognostic factor for mortality. Our results suggest that the T6SS of A. baumannii is associated with virulence and contributes to infections in immunocompromised patients and those with implanted medical devices.
我们调查了携带VI型分泌系统（T6SS）的鲍曼不动杆菌分离株的遗传背景和微生物学特征，以及T6SS对鲍曼不动杆菌血症患者的临床影响。本研究纳入了韩国2家三级医院中162例菌血症患者的鲍曼不动杆菌分离株。大约三分之一（51/162，31.5%）的鲍曼不动杆菌临床分离株携带hcp基因，并且在多位点序列分型中，hcp阳性分离株存在于几种基因型中。临床分离株中Hcp蛋白的表达和分泌各不相同。与T6SS阴性分离株（包括hcp阴性和hcp阳性但已失活的分离株）相比，可检测到Hcp分泌的鲍曼不动杆菌分离株（T6SS阳性）在与大肠杆菌的竞争中表现更佳。此外，T6SS阳性分离株在形成生物膜活性方面更高，且在正常人血清存在的情况下比T6SS阴性分离株具有更好的生存能力。在导管相关血流感染患者、造血干细胞移植受者以及接受免疫抑制剂治疗的患者中，T6SS阳性分离株的检出频率更高。然而，T6SS并非死亡率的预后因素。我们的结果表明，鲍曼不动杆菌的T6SS与毒力相关，并导致免疫功能低下患者以及植入医疗设备患者发生感染。
