Advances and challenges in barcoding pathogenic and environmentalLeptospira

Abstract

Leptospirosis is a zoonotic bacterial disease of global importance. A large spectrum of asymptomatic animal hosts can carry the infection and contribute to the burden of human disease. Environmental sources of human contamination also point to the importance of a hydrotelluric reservoir. Leptospirosis can be caused by as many as 15 different pathogenic or intermediate Leptospira species. However, classification of these bacteria remains complicated through the use of both serological and genetic classification systems that show poor correlation. With the advent of molecular techniques, DNA-based barcoding offers a conceptual framework that can be used for leptospirosis surveillance as well as source tracking. In this review, we summarize some of the current techniques, highlight significant successes and weaknesses and point to the future opportunities and challenges to successfully establish a widely applicable barcoding scheme for Leptospira.

Phylogenetic relationships and diversity of bat-associated Leptospira and the histopathological evaluation of these infections in bats from Grenada, West Indies

“…Several bats in this study produced Leptospira sequences that matched with L. noguchii and L. santarosai, albeit at low identities (below 90%). However, serology identifies serotypes and does not correlate with species in typing Leptospira [8,29], and hence we cannot compare our current genomic data with past serological data with any certainty. Thus, it is necessary to confirm Leptospira strains by PCR in these and other animals going forward in order to clarify Leptospira ecology and reservoir hosts in Grenada.…”

“…However, while the DNA sequences from PCR and phylogenetic analysis merely suggest that bats in Grenada have genetically diverse genotypes, of which several are possibly novel strains, DNA sequences alone are not considered sufficient to classify our unique bat-derived Leptospira genotypes reported herein as novel strains or species. DNA-DNA hybridization and more thorough genomic sequencing are necessary before we can deem our bat-derived Leptospira as novel taxa [4,29].…”

“…PCR-based tools have become essential in studying Leptospira biology, phylogeny, and pathogenesis, and are key to diagnosing active infection. Several genes have been used singly or in tandem to type Leptospira (flaB, gyrB, rpoB, 16SrRNA rrs, secY, lipL32) [29]. In particular, the rpoB gene is an ideal target for phylogenetic analyses: it allows for discrimination among Leptospira species better than most other gene sequences (e.g., rrs, lipL32), and all recognized Leptospira species to date have partial or whole Leptospira rpoB sequence entries in GenBank due to its use in many studies [30,31].…”

“…Previous research using serology to identify and name infecting Leptospira organisms (serovars) had major limitations. Although serology can reflect the epidemiology of circulating serovars, it does not identify species conclusively [29]. Furthermore, there is poor correlation between Leptospira serological (i.e., serovar) and genomic classification (i.e., species and strain), which complicates comparing current Leptospira genomic data with past and present serological data [29].…”

“…Although serology can reflect the epidemiology of circulating serovars, it does not identify species conclusively [29]. Furthermore, there is poor correlation between Leptospira serological (i.e., serovar) and genomic classification (i.e., species and strain), which complicates comparing current Leptospira genomic data with past and present serological data [29]. For instance, strains identified as belonging to serovar Bataviae have vast genetic heterogeneity, belonging to L. borgpetersenii, and L. kirschneri, L. interrogans, L. noguchii, or L. santarosai, according to genetic analyses [8].…”