Discovery, structure and function of plasmid mediated shufflon / 生物工程学报

Antimicrobial resistance has become a major public health issue of global concern. Conjugation is an important way for fast spreading drug-resistant plasmids, during which the type Ⅳ pili plays an important role. Type Ⅳ pili can adhere on the surfaces of host cell and other medium, facilitating formation of bacterial biofilms, bacterial aggregations and microcolonies, and is also a critical factor in liquid conjugation. PilV is an adhesin-type protein found on the tip of type Ⅳ pili encoded by plasmid R64, and can recognize the lipopolysaccharid (LPS) molecules that locate on bacterial membrane. The shufflon is a clustered inversion region that diversifies the PilV protein, which consequently affects the recipient recognition and conjugation frequency in liquid mating. The shufflon was firstly discovered on an IncI1 plasmid R64 and has been identified subsequently in plasmids IncI2, IncK and IncZ, as well as the pathogenicity island of Salmonella typhi. The shufflon consists of four segments including A, B, C, and D, and a specific recombination site named sfx. The shufflon is regulated by its downstream-located recombinase-encoding gene rci, and different rearrangements of the shufflon region in different plasmids were observed. Mobile colistin resistance gene mcr-1, which has attracted substantial attentions recently, is mainly located in IncI2 plasmid. The shufflon may be one of the contributors to fast spread of mcr-1. Herein, we reviewed the discovery, structure, function and prevalence of plasmid mediated shufflon, aiming to provide a theoretical basis on transmission mechanism and control strategy of drug-resistant plasmids.

Synergistic effect of β-thujaplicin and tigecycline against tet(X4)-positive Escherichia coli in vitro / 生物工程学报

The widespread of tigecycline resistance gene tet(X4) has a serious impact on the clinical efficacy of tigecycline. The development of effective antibiotic adjuvants to combat the looming tigecycline resistance is needed. The synergistic activity between the natural compound β-thujaplicin and tigecycline in vitro was determined by the checkerboard broth microdilution assay and time-dependent killing curve. The mechanism underlining the synergistic effect between β-thujaplicin and tigecycline against tet(X4)-positive Escherichia coli was investigated by determining cell membrane permeability, bacterial intracellular reactive oxygen species (ROS) content, iron content, and tigecycline content. β-thujaplicin exhibited potentiation effect on tigecycline against tet(X4)-positive E. coli in vitro, and presented no significant hemolysis and cytotoxicity within the range of antibacterial concentrations. Mechanistic studies demonstrated that β-thujaplicin significantly increased the permeability of bacterial cell membranes, chelated bacterial intracellular iron, disrupted the iron homeostasis and significantly increased intracellular ROS level. The synergistic effect of β-thujaplicin and tigecycline was identified to be related to interfere with bacterial iron metabolism and facilitate bacterial cell membrane permeability. Our studies provided theoretical and practical data for the application of combined β-thujaplicin with tigecycline in the treatment of tet(X4)-positive E. coli infection.

Bone marrow activation and autologous peripheral blood stem cell transplantation in combination with recombinant interleukin-2 application for treatment of T cell lymphoma in one case A follow-up of more than 10 years / 中国组织工程研究

A 33-year-old male patient complained of presenting goiter on the low back area for 2 months. Pathological examinations of resected goiter suggested non-Hodgkin lymphoma and showed that T cells, immunoblasts, and hemogram were roughly normal, and 2% sarcoma cells could be found in bone marrow. Stage Ⅳ T-cell non-Hodgkin's lymphoma was diagnosed. Following 4 months of chemotherapy using CHOP protocol (cyclophosphamide, adriamycin, vincristine, and prednisone included), the patient underwent bone marrow activation and autologous peripheral blood stem cell transplantation in combination with recombinant interleukin-2 application in April 1998. The preprocessing was performed under MACC protocol (L-sarcolysinum, cytarabine, cyclophosphamide, and Iomustine included). Ten days after autologous stem cell transplantation, neutrophil concentration was > 0.5×109/L and sixteen days after transplantation, blood platelet concentration was > 50×109/L. Six days after transplantation, the patient exhibited fever, and E. Coli infection was confirmed through blood culture. After antibiotic treatment, body temperature recovered to normal, and fever disappeared. The patient had been followed-up for 10 years and 10 months. During the follow-up period, he lived a normal life and work.