Evaluation of target-enrichment accompanied by next-generation sequencing for detection of four pathogens in bloodstream infections / 军事医学

Objective To establish an Ampliseq method that combines target-enrichment and the next-generation sequencing for simultaneous detection of Staphylococcus aureus, S.epidermidis, Klebsiella pneumoniae and Listeria monocytogenes in order to provide a fast and accurate means to detect pathogens in bloodstream infections.Methods A method to evaluate the LOD,specificity and sensitivity by constructing simulated samples spiked in known pathogens was established.Results and Conclusion Target-enrichment Ampliseq showed good sensitivity and specificity,and the limit of detection(LOD)was as low as 101CFU/ml.The sensitivity was 95.38%,the specificity was 95.45%and the Kappa value was between 0.839 -1.000.This method can detect S.aureus,S.epidermidis,K.pneumoniae and L.monocytogenes simultaneously in one reaction within 15 hours.

Establishment and evaluation of PCR-array for detection of six common pathogens of purulent meningitis in children / 军事医学

Objective To develop a PCR-array method for detecting common purulent meningitis pathogens including Streptococcus pneumoniae,Escherichia coli,Haemophilus influenzae type B,Neisseria meningitidis,S.agalactiae and Listeria monocytogenes in children.Methods The amplification efficiency,limit of detection (LOD) and cross-reactivity were validated with individually real-time PCR using genomic DNA of the six pathogenic bacteria.The sensitivity and specificity of the PCR-array method were evaluated using artificial cerebrospinal fluid(CSF),and the consistency between the PCR-array method and the golden method of CSF culture was evaluated using clinical samples.Results The primers and probes of the pathogens in PCR-array had high specificity,and there was no cross reaction between them.The LOD of the PCR-array method was 10 cfu/ml and very sensitive.The sensitivity and specificity of the PCR-array method could reach 95％ in the evaluation of artificial CSF,and had a good consistency with the clinical gold standard method.Conclusion The PCR-array method with high sensitivity and specificity can simultaneously detect six common pathogens in children with purulent meningitis at 2.5 h,which could provide reference for the diagnosis of purulent meningitis.

Preparation and activity analysis of RGD-mSAK (K130T, K135R) / 生物工程学报

In order to construct RGD-mSAK mutant with reduced immunogenicity, and identify its biological activity after purification, mSAK gene fragment was amplified by over-lapping extension PCR. Then the gene was inserted into the prokaryotic expression vector pBV220 with P(R)P(L) promoters after confirmed by DNA sequencing; the expression plasmid pBV220-RGD-mSAK was constructed, and then was transformed into E. coli. DH5alpha. After temperature induction, the mutant Staphylokinase was over-expressed and much of protein was in the supernate of lysate, which is over 50% of total protein in the host. The protein was isolated and purified in Q-Sepharose FF, Sephacryl S-200 and SP, high purity protein was obtained and its purity was over 98%. The thrombolysis activity of the RGD-mSAK protein is 1.68 x 10(5) u/mg by fibrin plate assay, which is slightly higher than that of the wild-type, and antiserum titers raised against this protein in guinea pigs were much lower than those of wild-type SAK, determined by ELISA. In anti-platelets aggregation assay in vitro, the RGD-mSAK protein has obvious inhibition activity of platelet aggregation in low concentration comparing to the control group and wild-type SAK group. So the RGD-mSAK protein is a low immunogenicity, bi-function molecular with both thrombolysis activity and anti-embolism activity. It provided the basis for further research of RGD-SAK.