Development of O-antigen gene cluster-specific PCRs for rapid typing six epidemic serogroups of Leptospira in China

Abstract

Background: Leptospira is the causative agent of leptospirosis. The O-antigen is the distal part of the lipopolysaccharide, which is a key component of outer membrane of Gram-negative bacteria and confers serological specificity. The epidemiology and clinical characteristics of leptospirosis are relative to the serology based taxonomic unit. Identification of Leptospira strains by serotyping is laborious and has several drawbacks.

Results: In this study, the O-antigen gene clusters of four epidemic Leptospira serogroups (serogroup Canicola, Autumnalis, Grippotyphosa and Hebdomadis) in China were sequenced and all genes were predicted in silico. Adding published sequences of two serogroups, Icterohaemorrhagiae (strain Lai and Fiocruz L1-130) and Sejroe (strain JB197 and L550), we identified six O-antigen-specific genes for six epidemic serogroups in China. PCR assays using these genes were developed and tested on 75 reference strains and 40 clinical isolates.

Conclusion: The results show that the PCR-based assays can be reliable and alternative means for rapid typing of these six serogroups of Leptospira.

Figure 1

Analysis of amplification products by electrophoresis. Amplification products obtained by PCR of DNA pools from 18 serogroups belonging to Leptospira and DNA of two non-Leptospira strains using primer pairs ict-F/R (a), can-F/R (b), aut-F/R (c), gri-F/R (d). heb-F/R (e), sej-F/R (f). 1: Icterohaemorrhagiae; 2: Javanica; 3: Canicola; 4: Ballum; 5: Pyrogenes; 6: Autumnalis; 7: Australis; 8: Pomona; 9: Grippotyphosa; 10: Hebdomadis; 11: Bataviae; 12: Tarassovi; 13: Manhao; 14: Sejroe; 15: Mini; 16: Celledoni; 17: Ranarum; 18: Sarmin; 19: S. enteritidis H9812; 20: S. aureus N315; M: DNA marker, bands with lengths of 10 kb, 8 kb, 5 kb, 2 kb 1000 bp, 700 bp, 500 bp, 400 bp, 300 bp, 200 bp and 100 bp, respectively.