Objective: To develop an oral live vaccine vector which stably carries exogenous genes.Methods:SL1344ΔsipBΔasd host-vector balanced lethal system was constructed by the method of recombinant suicide plasmid-mediated allelic exchange on the basis of attenuated Salmonella typhinurium SL1344ΔsipB.Then,the biological characteristics of SL1344ΔsipBΔasd was analyzed.Results:The results showed that the mutant was stabile with the Δasd gene in vitro;the serotype and growth rate of SL1344ΔsipBΔasd strain was almost same as the parent SL1344ΔsipB and SL1344 strain.And the mutant strains remain swim ming zones.Virulence test in mice showed that the virulence of SL1344ΔsipBΔasd which carried complementary plasmid pYA3493 by electro-transformation decreased by 1.4%compared with SL1344.Conclusion: These results showed that the SL1344ΔsipBΔasd mutant was successfully constructed.It is likely that this mutant should be used as a live vector to express foreign genes.

Spinal cord injury is a catastrophic injury causing lifelong severe disabilities, and poses a great burden to the individuals, families and society. In order to promote the standardization in treatment of traumatic spinal cord injury, the consensus on the evaluation, treatment and rehabilitation of traumatic spinal cord injury was suggested by experts, who came from authoritative multicenter in China. The expert consensus, which formed a standardization process from the first aid clinical treatment to rehabilitation of spinal cord injury, shall give a better practical guide for clinic and rehabilitation physicians.

OBJECTIVE: To determine the prevalence and influencing factors of work-related musculoskeletal disorders(WMSDs) among workers in a shipyard. METHODS: A total of 496 workers in a large shipyard in Guangdong Province were selected as research subjects using the convenient sampling method. The Questionnaire of Musculoskeletal Disorders was used to investigate the prevalence of WMSDs in various regions of the body in the past year.Multivariate logistic regression was used to analyze the potential influencing factors of WMSDs in the frequently affected body parts. RESULTS: The prevalence of WMSDs was 70.2%(348/496). The prevalence rates of WMSDs in different body regions were: lower back/waist(43.1%), neck(29.4%), shoulder(29.0%), hand/wrist(25.4%), knee(22.4%), hip/leg(14.3%), ankle/foot(12.1%), upper back(11.3%) and elbow(9.3%). Multivariate logistic regression analysis results showed that increased risk of lower back/waist WMSDs occurred in workers who carry heavy objects>5.0 kg, who work in uncomfortable positions, who repeatedly perform the same work every day, and who repeatedly perform the same action using the lower limbs and ankles(P<0.05). Employees working ≤8 hours or more than 8 hours per day had higher risk of developing lower back/waist WMSDs compared with workers working 8-10 hours per day(P<0.05). CONCLUSION: The prevalence of WMSDs among workers in the shipyard is high.The lower back/waist WMSD is the most common one. The influencing factors include work organization and adverse ergonomic factors.