Objective Human Lyme Borreliosis(LB), which is caused by Borrelia burgdorferi sensu lato(B. burgdorferi), has been identified as a major arthropod-borne infectious disease in China. We aimed to develop a multiple locus variable-number tandem repeat(VNTR) analysis(MLVA) assay for the genotyping of Borrelia burgdorferi strains detected in China. Methods B. garinii PBi complete 904.246 kb chromosome and two plasmids(cp26 and lp54) were screened by using Tandem Repeats Finder program for getting potential VNTR loci, the potential VNTR loci were analyzed and identified with PCR and the VNTR loci data were analyzed and MLVA clustering tree were constrcted by using the categorical coefficient and the unweighted pair-group method with arithmetic means(UPGMA). Results We identified 5 new VNTR loci through analyzing 47 potential VNTR loci. We used the MLVA protocol to analyse 101 B. burgdorferi strains detected in China and finally identified 51 unique genotypes in 4 major clusters including B. burgdorferi sensu stricto(B.b.s.s), B. garinii, B. afzelii, and B. valaisiana, consistent with the current MLSA phylogeny studies. The allele numbers of VNTR-1, VNTR-2, VNTR-3, VNTR-4, and VNTR-5 were 7, 3, 9, 7, and 6. The Hunter-Gaston index(HGI) of five VNTR loci were 0.79, 0.22, 0.77, 0.71, and 0.67, respectively. The combined HGI of five VNTR loci was 0.96. Clustering of the strains of Xinjiang, Inner Mongolia and Heilongjiang was confirmed, and this situation was consistent with the close geographical distribution of those provinces. Conclusion The MLVA protocol esytablished in this study is easy and can show strains' phylogenetic relationships to distinguish the strains of Borrelia species. It is useful for further phylogenetic and epidemiological analyses of Borrelia strains.
ZHOU XinHOU Xue XiaGENG ZhenZHAO RuiWAN Kang LinHAO Qin
Objective To study the technique of Western blot for the diagnosis of Lyme disease caused by Borrelia afzelii in China and to establish the standard criteria by operational procedure. Methods FP1, which is the representative strain of B. afzelii in China, was analyzed by SDS‐PAGE, electro transfer and immunoblotting assays. The molecular weights of the protein bands of FP1 were analyzed by Gel‐Pro analysis software. In a study using 451 serum samples (159 patients with Lyme disease and 292 controls), all observed bands were recorded. The accuracy of the WB as a diagnostic test was established by using the ROC curve and Youden index. Results Criteria for a positive diagnosis of Lyme disease were established as at least one band of P83/100, P58, P39, OspB, OspA, P30, P28, OspC, P17, and P14 in the IgG test and at least one band of P83/100, P58, P39, OspA, P30, P28, OspC, P17, and P41 in the IgM test. For IgG criteria, the sensitivity, specificity and Youden index were 69.8%, 98.3%, and 0.681, respectively; for IgM criteria, the sensitivity, specificity and Youden index were 47%, 94.2%, and 0.412, respectively. Conclusion Establishment of WB criteria for B. afzelii is important in validating the diagnostic assays for Lyme disease in China.
LIU Zhi YunHAO QinHOU Xue XiaJIANG YiGENG ZhenWU Yi MouWAN Kang Lin
Objective To optimize the performance of Pulsed-Field Gel Electrophoresis (PFGE) for the comparison of inter-laboratory results and information exchange of Borrelia burgdorferi subtyping. Methods A panel of 34 strains of B. burgdorferi were used to optimize PFGE for subtyping. In order to optimize the electrophoretic parameters (EPs), all 34 strains of B. burgdorferi were analyzed using four EPs, yielding different Simpson diversity index (D) values and the epidemiological concordance was also evaluated. Results The EP of a switch time of 1 s to 25 s for 13 h and 1 s to 10 s for 6 h produced the highest D value and was declared to be optimal for MluI and SmaI PFGE of B. burgdorferi. MluI and SmaI were selected as the first and second restriction enzymes for PFGE subtyping of B. burgdorferi according to discrimination and consistency with epidemiological data. Conclusion PFGE can be used as a valuable test for routine genospecies identification of B. burgdorferi.
GENG ZhenHOU Xue XiaHAO QinZHOU Hai JianWANG FengWAN Kang Lin
