Identification of Leptospira serovars by RFLP of the RNA polymerase beta subunit gene (rpoB)

Genetic basis underlying the serological affinity of leptospiral serovars from serogroups Sejroe, Mini and Hebdomadis

Leptospirosis is a widely distributed zoonosis caused by pathogenic strains of bacteria of the genus Leptospira (Phylum Spirochaetes). Its agents are commonly classified based on their antigenic characteristics into serogroups and serovars, which are relevant for epidemiologic studies and vaccine development. Serological tests are considered laborious and require a specialized infrastructure. Some molecular methods have been proposed to accelerate these procedures, but they still can not replace the immunological tests, thus requiring a further understanding of the genetic basis underlying the serological classification. In this work, we focused on elucidating the genetic factors determinant for the serogroup Sejroe, which is one of the most prevalent serogroups in livestock. For this, we conducted a comparative analysis using >700 leptospiral genomic samples available in the public database. The analysis showed that the genes comprising the rfb locus are the main genetic factors associated with the serological classification. Samples from the serogroup Sejroe have an rfb locus with a conserved gene composition that differs from most other serogroups. Hebdomadis and Mini were the only serogroups whose samples have an rfb locus with similar gene composition to those from serogroup Sejroe, corroborating with the serological affinity shared by them. Finally, we could determine a small region in the rfb locus in which each of those three serogroups can be distinguished by its gene composition. This is the first work that uses an extensive repertoire of genomic data of leptospiral samples to elucidate the molecular basis of the serological classification and open the road to more reliable strategies based on molecular methods for serodiagnosis.

Applicability of rpoB Gene for PCR-RFLP based Discrimination of Bifidobacterial Species Isolated from Human and Animal Sources

Bifidobacteria are widely used as probiotics for their application in the development of functional food and prophylactic therapy. This has necessitated the development of a molecular approach for the genera to be widely identified up to species and subspecies level. In the current study, PCR-RFLP of the partial RNA polymerase β-subunit (rpoB) gene fragment was evaluated for differential identification of Bifidobacterium species. The rpoB gene partial sequences of 575 bp were amplified from 93 previously identified isolates collected from various sources of human and animal origin along with 12 standard reference strains. The PCR amplified products were digested with three restriction endonucleases HhaI, HinfI and BanI separately. Dendrograms constructed from the patterns of HhaI, were found to be more discriminatory and successfully differentiated all the twelve species and also at sub-species level in between B. longum subsp. longum and B. longum subsp. infantis. However, B. adolescentis and B. pseudocatenulatum group clusters were not separated and represented by one group. The groups were further discriminated by HinfI restriction digestion. A separate combination thereof may be used for inferring the classification of bifidobacterial species targeted on rpoB PCR-RFLP analysis. To our knowledge, this work is the first report based on use of rpoB PCR-RFLP for discrimination of the isolates of genus Bifidobacterium and also provides insights into specific advantages of this method over hsp60 PCR-RFLP in differentiating B. longum subsp. longum and B. longum subsp. infantis.

Leptospira spp., a genus in the stage of diversity and genomic data expansion

Leptospirosis is a widespread global zoonotic bacterial disease with a noteworthy human-animal-ecosystem interface. The disease presents different clinical manifestations and a high mortality and morbidity rates in humans and animals throughout the world. Characterization and correct classification of Leptospira isolates is essential for a better understanding the epidemiological properties of the disease. In the last ten years, molecular typing tools have been developed and applied to this field. These methods together with the availability of hundreds of new whole genome sequences that belong to known and new described species are shaping the understanding and structure of the entire genus.