Deciphering the unexplored Leptospira diversity from soils uncovers genomic evolution to virulence

Cleavage of cell junction proteins as a host invasion strategy in leptospirosis

Infection and invasion are the prerequisites for developing the disease symptoms in a host. While the probable mechanism of host invasion and pathogenesis is known in many pathogens, very little information is available on Leptospira invasion/pathogenesis. For causing systemic infection Leptospira must transmigrate across epithelial barriers, which is the most critical and challenging step. Extracellular and membrane-bound proteases play a crucial role in the invasion process. An extensive search for the proteins experimentally proven to be involved in the invasion process through cell junction cleavage in other pathogens has resulted in identifying 26 proteins. The similarity searches on the Leptospira genome for counterparts of these 26 pathogenesis-related proteins identified at least 12 probable coding sequences. The proteins were either extracellular or membrane-bound with a proteolytic domain to cleave the cell junction proteins. This review will emphasize our current understanding of the pathogenic aspects of host cell junction-pathogenic protein interactions involved in the invasion process. Further, potential candidate proteins with cell junction cleavage properties that may be exploited in the diagnostic/therapeutic aspects of leptospirosis will also be discussed. KEY POINTS: • The review focussed on the cell junction cleavage proteins in bacterial pathogenesis • Cell junction disruptors from Leptospira genome are identified using bioinformatics • The review provides insights into the therapeutic/diagnostic interventions possible.

Leptospira interrogans encodes a canonical BamA and three novel noNterm Omp85 outer membrane protein paralogs

The Omp85 family of outer membrane proteins are ubiquitously distributed among diderm bacteria and play essential roles in outer membrane (OM) biogenesis. The majority of Omp85 orthologs are bipartite and consist of a conserved OM-embedded 16-stranded beta-barrel and variable periplasmic functional domains. Here, we demonstrate that Leptospira interrogans encodes four distinct Omp85 proteins. The presumptive leptospiral BamA, LIC11623, contains a noncanonical POTRA4 periplasmic domain that is conserved across Leptospiraceae. The remaining three leptospiral Omp85 proteins, LIC12252, LIC12254 and LIC12258, contain conserved beta-barrels but lack periplasmic domains. Two of the three 'noNterm' Omp85-like proteins were upregulated by leptospires in urine from infected mice compared to in vitro and/or following cultivation within rat peritoneal cavities. Mice infected with a L. interrogans lic11254 transposon mutant shed tenfold fewer leptospires in their urine compared to mice infected with the wild-type parent. Analyses of pathogenic and saprophytic Leptospira spp. identified five groups of noNterm Omp85 paralogs, including one pathogen- and two saprophyte-specific groups. Expanding our analysis beyond Leptospira spp., we identified additional noNterm Omp85 orthologs in bacteria isolated from diverse environments, suggesting a potential role for these previously unrecognized noNterm Omp85 proteins in physiological adaptation to harsh conditions.

Leptospiral adhesins: from identification to future perspectives

Leptospirosis is a significant zoonosis worldwide, with disease severity ranging from a mild non-specific illness to multi-organ dysfunction and hemorrhage. The disease is caused by pathogenic bacteria of the genus Leptospira, which are classified into pathogenic and saprophytic clades. Bacterial binding to host molecules and cells, coordinated by adhesin proteins, is an important step in pathogenesis. While many leptospiral adhesins have been identified, the vast majority have not been characterized in vivo. Herein, we present an overview of the current methodologies and successes in identifying adhesins in Leptospira, including known biological roles in vivo. We will also identify and discuss potential areas for future research.

Severe Leptospirosis with Acute Kidney Injury: A Case Description and Literature Review

INTRODUCTION

Leptospirosis is a globally transmitted zoonotic disease caused by Leptospira spp., a highly mobile, obligate aerobic, spiral-shaped bacteria. Described first by Adolf Weil in 1886, leptospirosis in Germany is rare, leading to a delayed diagnosis due to diverse symptoms. Most cases are mild, but severe forms, like Weil's disease, cause life-threatening complications such as fever, jaundice, hemoptysis, and acute kidney injury (AKI). The aim of this work was to provide a literature review of leptospirosis with renal manifestation based on a case report.

CASE PRESENTATION

We report the case of an 81-year-old male patient with initially unclear oliguric AKI, bilateral pulmonary infiltrates, and jaundice. After excluding common AKI causes, the expanded patient history suggested possible rat contact in his chicken coop. Finally, we serologically identified an infection with Leptospira spp. by positive IgM, proving that the illness was compatible with classical Weil's disease. The patient underwent temporary hemodialysis and antibiotic treatment with intravenous penicillin G for 2 weeks. Under therapy, the AKI, hyperbilirubinemia, and clinical condition of the patient improved. The patient was discharged after 2 weeks. In the following controls, slightly impaired kidney function was observed, indicating a progress of his chronic kidney disease (CKD).

CONCLUSION

Although leptospirosis is rare, there are some cases with a fulminant course. Impairment of renal function often correlates with severity of the disease requiring antibiotic treatment. In some cases, AKI progresses to CKD demonstrating the need to raise awareness for leptospirosis.

Leptospirosis in India: insights on circulating serovars, research lacunae and proposed strategies to control through one health approach

Leptospirosis is one of the most neglected zoonotic infections of public health concern worldwide and a remerging infection in tropical countries such as India. The infection least explored disease and the epidemiological and other critical data are scarce for the disease rate reported and to control the infection. Leptospirosis as sapronosis is as underrated as the infection itself, and this article aims to explore the significance of this aspect of the disease. The research review aimed at the epidemiological understanding of the infection to control the negative impact of the disease. A mixed review and analysis were carried out to understand the knowledge published on the critical and understudied areas like epidemiology, transmission, diagnosis, treatment, and control of infection. A systematic analysis was carried out to extract information about the reported circulating strains, and research lacunae in India with the published data available in PubMed. The article elaborately discusses crucial inference areas of infection transmission and addresses lacunae in critically unacclaimed areas of infection to control the spread of infection using one health approach (OHA), and strategies to control leptospiral infection are proposed. The article also reviewed how and why Leptospirosis can be best studied and controlled by "One health approach" in India.

Inter-species Transcriptomic Analysis Reveals a Constitutive Adaptation Against Oxidative Stress for the Highly Virulent Leptospira Species

Transcriptomic analyses across large scales of evolutionary distance have great potential to shed light on regulatory evolution but are complicated by difficulties in establishing orthology and limited availability of accessible software. We introduce here a method and a graphical user interface wrapper, called Annotator-RNAtor, for performing interspecies transcriptomic analysis and studying intragenus evolution. The pipeline uses third-party software to infer homologous genes in various species and highlight differences in the expression of the core-genes. To illustrate the methodology and demonstrate its usefulness, we focus on the emergence of the highly virulent Leptospira subclade known as P1+, which includes the causative agents of leptospirosis. Here, we expand on the genomic study through the comparison of transcriptomes between species from P1+ and their related P1- counterparts (low-virulent pathogens). In doing so, we shed light on differentially expressed pathways and focused on describing a specific example of adaptation based on a differential expression of PerRA-controlled genes. We showed that P1+ species exhibit higher expression of the katE gene, a well-known virulence determinant in pathogenic Leptospira species correlated with greater tolerance to peroxide. Switching PerRA alleles between P1+ and P1- species demonstrated that the lower repression of katE and greater tolerance to peroxide in P1+ species was solely controlled by PerRA and partly caused by a PerRA amino-acid permutation. Overall, these results demonstrate the strategic fit of the methodology and its ability to decipher adaptive transcriptomic changes, not observable by comparative genome analysis, that may have been implicated in the emergence of these pathogens.

Leptospirosis in Malaysia: current status, insights, and future prospects

Among zoonotic infections, leptospirosis has a worldwide distribution and high prevalence in tropical regions. It has a broad clinical presentation from mild to severe, life-threatening infection. Leptospires, the etiological agent of leptospirosis, are found in varied ecological niches and animal species, providing a significant source of human infection. This review aims to provide the current status of leptospirosis in Malaysia and the direction for future studies. The literature search for this review was performed using PubMed, Web of Sciences, and Google Scholar databases. The incidence of leptospirosis in Malaysia from 2004 to 2020 varied; however, a large number of cases occurred during floods. Leptospira has been isolated from wild and domestic animals as well as from the environment; among them, several novel species have been identified. In Malaysia, leptospirosis infection and death were mostly associated with recreational and non-recreational water activities. Despite the endemicity of leptospirosis, the public's knowledge, attitude, and practice level are relatively low in this country. More studies are needed in Malaysia to explore the extent of leptospirosis in different settings and locations.

Prevalence and Characteristics of Novel Pathogenic Leptospira Species in Bats in Yunnan Province, China

Leptospirosis has been identified as a zoonotic disease caused by pathogenic spirochetes of the bacterial genus Leptospira. Rodents are considered the primary hosts of these bacteria, whereas many recent studies suggest that bats may serve as potential natural reservoirs. However, studies on pathogenic spirochetes hosted by bat populations still need to be completed in China. In this study, a total of 276 bats belonging to five genera collected in Yunnan Province (Southwest China) from 2017 to 2021 were included in the screening. Pathogenic spirochetes were detected by PCR amplification and sequencing targeting four genes (rrs, secY, flaB, and LipL32), resulting in 17 positive samples. Phylogenetic analysis based on multi-loci concatenated sequences, inferred by MLST approach, identified the strains as two novel Leptospira species within the pathogenic group. Of note, only Rousettus leschenaultii was found to harbor these spirochetes, suggesting it may be one of the potential natural reservoirs in circulating leptospires in this region. Nevertheless, the pathogenesis and transmission dynamics still need to be fully understood, requiring in-depth studies on other animals and the surrounding population.

Leptospirosis in Aotearoa New Zealand: Protocol for a Nationwide Case-Control Study

BACKGROUND

In Aotearoa New Zealand, 90% of patients with notified leptospirosis (a zoonotic bacterial disease) have been men working in agricultural industries. However, since 2008, the epidemiology of notified cases has been gradually changing, that is, more women are affected; there are more cases associated with occupations traditionally not considered high risk in New Zealand; infecting serovars have changed; and many patients experience symptoms long after infection. We hypothesized that there is a shift in leptospirosis transmission patterns with substantial burden on affected patients and their families.

OBJECTIVE

In this paper, we aimed to describe the protocols used to conduct a nationwide case-control study to update leptospirosis risk factors and follow-up studies to assess the burden and sources of leptospirosis in New Zealand.

METHODS

This study used a mixed methods approach, comprising a case-control study and 4 substudies that involved cases only. Cases were recruited nationwide, and controls were frequency matched by sex and rurality. All participants were administered a case-control questionnaire (study 1), with cases being interviewed again at least 6 months after the initial survey (study 2). A subset of cases from two high-risk populations, that is, farmers and abattoir workers, were further engaged in a semistructured interview (study 3). Some cases with regular animal exposure had their in-contact animals (livestock for blood and urine and wildlife for kidney) and environment (soil, mud, and water) sampled (study 4). Patients from selected health clinics suspected of leptospirosis also had blood and urine samples collected (study 5). In studies 4 and 5, blood samples were tested using the microscopic agglutination test to test for antibody titers against Leptospira serovars Hardjo type bovis, Ballum, Tarassovi, Pomona, and Copenhageni. Blood, urine, and environmental samples were also tested for pathogenic Leptospira DNA using polymerase chain reaction.

RESULTS

Participants were recruited between July 22, 2019, and January 31, 2022, and data collection for the study has concluded. In total, 95 cases (July 25, 2019, to April 13, 2022) and 300 controls (October 19, 2019, to January 26, 2022) were interviewed for the case-control study; 91 cases participated in the follow-up interviews (July 9, 2020, to October 25, 2022); 13 cases participated in the semistructured interviews (January 26, 2021, to January 19, 2022); and 4 cases had their in-contact animals and environments sampled (October 28, 2020, and July 29, 2021). Data analysis for study 3 has concluded and 2 manuscripts have been drafted for review. Results of the other studies are being analyzed and the specific results of each study will be published as individual manuscripts..

CONCLUSIONS

The methods used in this study may provide a basis for future epidemiological studies of infectious diseases.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/47900.

Lipid A structural diversity among members of the genus Leptospira

Lipid A is the hydrophobic component of bacterial lipopolysaccharide and an activator of the host immune system. Bacteria modify their lipid A structure to adapt to the surrounding environment and, in some cases, to evade recognition by host immune cells. In this study, lipid A structural diversity within the Leptospira genus was explored. The individual Leptospira species have dramatically different pathogenic potential that ranges from non-infectious to life-threatening disease (leptospirosis). Ten distinct lipid A profiles, denoted L1-L10, were discovered across 31 Leptospira reference species, laying a foundation for lipid A-based molecular typing. Tandem MS analysis revealed structural features of Leptospira membrane lipids that might alter recognition of its lipid A by the host innate immune receptors. Results of this study will aid development of strategies to improve diagnosis and surveillance of leptospirosis, as well as guide functional studies on Leptospira lipid A activity.

Identification of Leptospira Species in Environmental Soil of Urban Settlements in Cambodia

Background: Leptospirosis represents a major public health threat in Cambodia. To help establish preventive strategies for leptospirosis, we isolated and identified Leptospira from soil collected in Phnom Penh and its neighboring province during the dry and rainy seasons. Materials and Methods: Soil samples were collected from 15 sites in the Phnom Penh metropolitan area and Kandal Province in 2019 and 2020. A total of 120 soil samples were collected and analyzed after culturing. Cultured isolates were identified at the species level using 16S rRNA and gyrB gene sequencing analysis. Results: The positive culture rate for Leptospira was significantly higher for samples collected during the rainy season (31 out of 60 samples, 51.7%) than during the dry season (19 out of 60 samples; p < 0.05, chi-squared test). In terms of sampling area, 10 (35.7%) and 13 (46.9%) soil samples from Phnom Penh and 9 (28.1%) and 18 (56.3%) soil samples from Kandal Province were culture-positive when collected during the dry and rainy seasons, respectively. Three isolates from the Kandal samples collected during the dry season were categorized as pathogenic clade type P1 according to 16S rRNA and gyrB sequence analyses. In addition, samples collected during the rainy season from Phnom Penh and Kandal Province (three each) were categorized as clade type P1. The samples with isolates in clade type P1 were collected from riverbanks during both the dry and rainy seasons and from a hospital garden during the rainy season. Conclusions: This is the first report on the isolation of clade P1 Leptospira species in environmental soil samples from Cambodia. Environmental soil appears to be a reservoir for Leptospira in the capital city and surrounding areas of Cambodia. This study contributes to the understanding of Leptospira species distribution in Asian countries.

Epidemiology of Leptospira spp. infection in a beef cattle area of Argentina

Leptospirosis is an infectious disease caused by pathogenic Leptospira that affect humans and animals. This disease is complex and non-eradicable in nature. Therefore, the understanding of it is epidemiology in different environments is crucial to implement prevention and control measures. The prevalence of Leptospira infection in beef cattle farms is affected by multiple environmental, management and individual factors. In this study, a cross-sectional serological survey was carried on to estimate the prevalence of Leptospira antibodies in beef cattle in Tandil and Ayacucho Departments (Buenos Aires Province) and to identify risk factors and spatial clusters associated with seropositivity. Using a probabilistic two-stage sampling, 25 farms and 15 animals per farm were selected. The Microagglutination Test was used to analize all serum samples. Bivariate and multivariate analyses were performed. Seventy-three out of 375 cows were seropositive, representing a positivity rate of 19.47% (95% CI: 10.51-28.42), with Sejroe and Pomona being the most reactive serogroups: 9.33% (95% CI: 6.26-12.41) and 8.27% (95% CI: 5.35-11.19), respectively. The prevalence in Ayacucho was 23.11% (95% CI: 10.05-36.17), and in Tandil, 14% (95% CI: 3.25-24.75). The animals from Ayacucho presented 2.01 (1.16-3.49) more chances of being positive compared with those from Tandil (p < 0.01). After the Generalized Linear Mixed Model (GLMM) with random effect of farm-level risk, the presence of lagoons (OR: 7.32, 95% CI: 1.68-31.8, p < 0.05) and undulating terrain (OR: 0.24, 95% CI: 0.07-0.74, p < 0.05) were associated with bovine leptospirosis. Four spatial clusters with higher rates of seropositivity were detected. A new GLMM was performed with the significant variables detected in the first GLMM and a new variable, "being inside the spatial cluster," being the only one that remained significant (OR: 9.58, 95% CI: 3.39-27.08, p < 0.0001). The animals inside the clusters belonged to farms with a greater presence of creeks (OR: 9.03, 95% CI: 3.37-24.18, p < 0.0001), higher accumulated rainfall (OR: 1.01, 95% CI: 1-1.01, p < 0.0001) and less undulating terrain (OR: 0.18, 95% CI: 0.10-0.35, p < 0.0001). We conclude that Leptospira is seroprevalent in beef cattle in Tandil and Ayacucho Departments, especially in the latter, where the largest cattle farms are located. Prevalence of seropositivity animals was associated with selected environmental risk factors.

Risk factors for Leptospira seropositivity in rural Northern Germany, 2019

We investigated seroprevalence and factors associated with Leptospira spp. infections in humans in rural Northern Germany. Sera of 450 participants were tested for leptospira-reactive IgG antibodies by two enzyme-linked immunosorbent assays (ELISA). A narrow (specific) and a broad (sensitive) case definition were applied and results compared in the analysis. Personal data were collected via questionnaire and associations with the serostatus were investigated by multivariable logistic regression. The seroprevalence estimates were 1.6% (95%-confidence interval (CI) = 0.63-3.2) under the narrow and 4.2% (95%-CI = 2.6-6.5%) under the broad case definition. Few (14%) participants knew about the pathogen. No seropositive participant recalled a prior leptospirosis diagnosis. Spending more than two hours a week in the forest was significantly associated with anti-leptospira IgG in both models (broad case definition: adjusted odds ratio (aOR) = 2.8, 95%-CI = 1.2-9.1; narrow case definition: aOR = 11.1, 95%-CI = 1.3-97.1). Regular cleaning of storage rooms was negatively associated in the broad (aOR = 0.17, 95%-CI = 0.03-0.98) and touching a dead rodent in the past 10 years in the narrow case definition model (aOR = 0.23, 95%-CI = 0.05-1.04). Our findings support risk factors identified in previous investigations. To counter the low awareness for the pathogen, we recommend that health authorities communicate risks and preventive measures to the public by using target-group specific channels.

Leptospirosis in Vietnam

Leptospirosis poses a serious public health problem in many countries because about 1 million people suffer annually from this severe, often fatal, infection. At present, its importance has been increasing due to development of integration processes, globalization and intensification of economic activities, inevitable anthropogenic transformation of landscapes as well as rise in number of people with occupational risk of pathogen exposure. The burden of human leptospirosis is expected to rise with demographic shifts and climate change that result in heavy rainfall and flooding. Regarding leptospirosis, Southeast Asia, including Vietnam, is among the most vulnerable global regions. The objective of the review was to analyze available published data on the spread of leptospirosis in Vietnam. More than 100 research articles were analyzed allowing to state that in Vietnam synanthropic rodents (rats), agricultural (buffaloes, cattle, pigs) and domestic animals (cats, dogs) are the main sources of leptospirosis infection in humans. It is essential that rats (cats and dogs also) in Vietnam are used for food. Among all farm animals, pigs are of maximal importance as a source of infection in humans. In Vietnam, Leptospira prevalence in pigs varies widely, up to 73%. It depends significantly on the location, farm size, age and gender of animals, etc. A large variety of Leptospira serovars have been identified in pigs in Vietnam: Tarassovi, Bratislava, Australis, Javanica, Autumnalis, Grippotyphosa, and some others. Official Vietnam reporting of leptospirosis cases based on clinical data does not reflect the real-life incidence rate in humans. However, the available seroprevalence studies reveal that, on average, about 10% of the Vietnamese population are infected with Leptospira. Work in agriculture is the dominant risk factor for acquiring this infection. The highest Leptospira seroprevalence rates were detected in farmers, 63.2%. Serovar diversity is typical for pathogenic Leptospira circulating in Vietnam. In humans, the most frequent are antibodies to Hebdomadis, Wolffi and Icterohaemorrhagiae, but the frequency varied markedly across the country depending on the site, possibly with relation to the environment, as well as with economic activity of the local population. In Vietnam, geographic, climatic and social differences between northern, central and southern regions contribute to the specificity of local leptospirosis epidemiology. This emphasizes the advisability of developing special measures for leptospirosis prevention taking into account regional peculiarities.

Leptospira enrichment culture followed by ONT metagenomic sequencing allows better detection of Leptospira presence and diversity in water and soil samples

Background

Leptospirosis, a life-threatening disease in humans and animals, is one of the most widespread global zoonosis. Contaminated soil and water are the major transmission sources in humans and animals. Clusters of disease outbreaks are common during rainy seasons.

Methodology/Principal findings

In this study, to detect the presence of Leptospira, we applied PCR, direct metagenomic sequencing, and enrichment culture followed by PCR and metagenomic sequencing on water and soil samples. Direct sequencing and enrichment cultures followed by PCR or sequencing effectively detected pathogenic and nonpathogenic Leptospira compared to direct PCR and 16S amplification-based metagenomic sequencing in soil or water samples. Among multiple culture media evaluated, Ellinghausen-McCullough-Johnson-Harris (EMJH) media containing antimicrobial agents was superior in recovering and detecting Leptospira from the environmental samples. Our results show that enrichment culture followed by PCR can be used to confirm the presence of pathogenic Leptospira in environmental samples. Additionally, metagenomic sequencing on enrichment cultures effectively detects the abundance and diversity of Leptospira spp. from environmental samples.

Conclusions/Significance

The selection of methodology is critical when testing environmental samples for the presence of Leptospira. Selective enrichment culture improves Leptospira detection efficacy by PCR or metagenomic sequencing and can be used successfully to understand the presence and diversity of pathogenic Leptospira during environmental surveillance.

Leptospira sanjuanensis sp. nov., a pathogenic species of the genus Leptospira isolated from soil in Puerto Rico

Two spirochetes (designated strains LGVF01 and LGVF02T) were isolated from soil samples in San Juan, Puerto Rico in HAN media after selection using a combination of ELISA, agar plating, and colony screening by Fluorescent Antibody Testing (FAT) and PCR for lipL32 and secY. Isolates were helix-shaped, aerobic, fast-growing, and highly motile. Genome sequence analysis indicated that both strains should be classified as members of a novel species within the pathogenic (P1) clade of the genus Leptospira . The average nucleotide identity between the two strains was 99.2 %, but below 93.2 % when compared to any previously described leptospiral species. Serotyping of strain LGVF02T indicates that it does not belong within any serogroup of Leptospira suggesting it also represents a new serovar. Collectively, strains LGVF01 and LGVF02T represent a new species of pathogenic leptospires for which the name Leptospira sanjuanensis sp. nov. is proposed. The type strain is LGVF02T (=NVSL-LGVF02T=KIT0302T).

Co-Radiation of Leptospira and Tenrecidae (Afrotheria) on Madagascar

Leptospirosis is a bacterial zoonosis caused by pathogenic Leptospira that are maintained in the kidney lumen of infected animals acting as reservoirs and contaminating the environment via infected urine. The investigation of leptospirosis through a One Health framework has been stimulated by notable genetic diversity of pathogenic Leptospira combined with a high infection prevalence in certain animal reservoirs. Studies of Madagascar’s native mammal fauna have revealed a diversity of Leptospira with high levels of host-specificity. Native rodents, tenrecids, and bats shelter several distinct lineages and species of Leptospira, some of which have also been detected in acute human cases. Specifically, L. mayottensis, first discovered in humans on Mayotte, an island neighboring Madagascar, was subsequently identified in a few species of tenrecids on the latter island, which comprise an endemic family of small mammals. Distinct L. mayottensis lineages were identified in shrew tenrecs (Microgale cowani and Nesogale dobsoni) on Madagascar, and later in an introduced population of spiny tenrecs (Tenrec ecaudatus) on Mayotte. These findings suggest that L. mayottensis (i) has co-radiated with tenrecids on Madagascar, and (ii) has recently emerged in human populations on Mayotte following the introduction of T. ecaudatus from Madagascar. Hitherto, L. mayottensis has not been detected in spiny tenrecs on Madagascar. In the present study, we broaden the investigation of Malagasy tenrecids and test the emergence of L. mayottensis in humans as a result of the introduction of T. ecaudatus on Mayotte. We screened by PCR 55 tenrecid samples from Madagascar, including kidney tissues from 24 individual T. ecaudatus. We describe the presence of L. mayottensis in Malagasy T. ecaudatus in agreement with the aforementioned hypothesis, as well as in M. thomasi, a tenrecid species that has not been explored thus far for Leptospira carriage.

Monitoring of Leptospira species diversity in freshwater bathing area and in rats in Paris, France

Leptospirosis is a neglected zoonotic disease with a worldwide distribution caused by bacterial pathogenic Leptospira. Rodents are considered as the main reservoir of Leptospira and transmission usually occurs through exposure to urine-contaminated environment. However, interactions between environment, rodent reservoir and human leptospirosis remain poorly studied. Here, we evaluated the concentration of Leptospira in surface water and captured rats in the city of Paris (France) from 2018 to 2020 using an integrity qPCR (Quantitative Polymerase Chain Reaction). All environmental samples (n = 1031) were positive for saprophytic Leptospira but pathogenic Leptospira P1 group were only found in 40% (n = 363; 2018) to 0% (n = 264; 2020) of samples. In the same time, analysis of 200 brown rat corpses trapped in the city, showed about 15% of positivity for Leptospira but the different method used for rats conservation (based on presence or absence of conservative agent) showed important variations in the Leptospira prevalence. Metagenomic analysis, based on rrs gene sequencing, was also carried out to evaluate the distribution of Leptospira in samples. Results could indicate that some species of Leptospira are found in surface waters as well as rats, but further study is needed to accurately describe the nature of the link between these two reservoirs. Quantification of Leptospira and pathogenic species description circulating inside animal reservoir living in the vicinity of freshwater in urban areas, will be helpful to understand the eco-epidemiology of leptospirosis and to establish prevention and intervention strategies, especially in the context of organization of recreative activity events in these urban areas.

Comparison of the Serion IgM ELISA and Microscopic Agglutination Test for diagnosis of Leptospira spp. infections in sera from different geographical origins and estimation of Leptospira seroprevalence in the Wiwa indigenous population from Colombia

Leptospirosis is among the most important zoonotic diseases in (sub-)tropical countries. The research objective was to evaluate the accuracy of the Serion IgM ELISA EST125M against the Microscopic Agglutination Test (MAT = imperfect reference test); to assess its ability to diagnose acute leptospirosis infections and to detect previous exposure to leptospires in an endemic setting. In addition, to estimate the overall Leptospira spp. seroprevalence in the Wiwa indigenous population in North-East Colombia. We analysed serum samples from confirmed leptospirosis patients from the Netherlands (N = 14), blood donor sera from Switzerland (N = 20), and sera from a cross-sectional study in Colombia (N = 321). All leptospirosis ELISA-positive, and a random of negative samples from Colombia were tested by the MAT for confirmation. The ELISA performed with a sensitivity of 100% (95% CI 77% - 100%) and a specificity of 100% (95% CI 83% - 100%) based on MAT confirmed Leptospira spp. positive and negative samples. In the cross-sectional study in Colombia, the ELISA performed with a sensitivity of 100% (95% CI 2–100%) and a specificity of 21% (95% CI 15–28%). Assuming a 5% Leptospira spp. seroprevalence in this population, the positive predictive value was 6% and the negative predictive value 100%. The Leptospira spp. seroprevalence in the Wiwas tested by the ELISA was 39%; however, by MAT only 0.3%. The ELISA is suitable to diagnose leptospirosis in acutely ill patients in Europe several days after onset of disease. For cross-sectional studies it is not recommended due to its low specificity. Despite the evidence of a high leptospirosis prevalence in other study areas and populations in Colombia, the Wiwa do not seem to be highly exposed to Leptospira spp.. Nevertheless, leptospirosis should be considered and tested in patients presenting with febrile illness.

Leptospirosis is among the most important zoonotic diseases in (sub-)tropical countries. The correct diagnosis of leptospirosis is very important to take a medical or public health decision. Therefore, we tested a serological test (ELISA) for its ability to correctly diagnose a negative sample as truly negative and a positive sample as truly positive. We tested the ELISA with European acute leptospirosis confirmed positive and negative samples and compared results with another serological test (microscopic agglutination test), which is the recognized reference test. Further, the ELISA was assessed for its ability to detect previous exposure to leptospires in serum samples from the indigenous Wiwa population from Colombia, where leptospirosis is expected to be endemic.

The ELISA performed very well with sera from patients with acute leptospirosis, however had difficulties to diagnose negative samples as truly negative in the Colombian field samples; hence unexposed persons were falsely diagnosed to be positive. Therefore, we recommend using the ELISA to detect acute leptospirosis several days after onset of illness in a non-endemic environment, but are not convinced of its usefulness to screen a population for previous Leptospira spp. exposure.

Activation of Canine, Mouse and Human TLR2 and TLR4 by Inactivated Leptospira Vaccine Strains

Canine Leptospira vaccines contain inactivated strains of pathogenic Leptospira, the causative agents of leptospirosis. For an effective response to vaccination, activation of the innate immune system via pattern recognition receptors such as TLRs is crucial. However, it is not known which TLRs are activated by Leptospira in dogs. To investigate the involvement of canine TLR2, TLR4, and TLR5 in the recognition of Leptospira, we stimulated canine moDC and reporter cells expressing canine TLR2 with either whole-inactivated bacteria or purified LPS of Leptospira strains, representing the serogroups generally used in canine leptospirosis vaccines. Using the endotoxin neutralizing reagent polymyxin B and TLR4 antagonist RS-LPS, we demonstrate that Leptospira LPS and canine TLR4 are involved in IL-1β production as well as in the uptake of inactivated Leptospira in canine moDC. Furthermore, polymyxin B only partially inhibited IL-1β production induced by inactivated Leptospira, suggesting that next to TLR4, also other TLRs may be involved. The observed activation of canine TLR2-expressing reporter cells by inactivated Leptospira strains indicates that TLR2 could be one of these TLRs. Next, we analyzed TLR2 and TLR4 activating capabilities by the same Leptospira strains using human and mouse TLR-expressing reporter cells. Inactivated Leptospira and leptospiral LPS activated not only mouse, but also human TLR4 and this activation was shown to be LPS dependent in both cases. Additionally, inactivated Leptospira activated mouse and human TLR2-expressing reporter cell lines. In our study, we could not identify significant species differences in the recognition of Leptospira by TLR2 and TLR4 between dog, human and mouse. Lastly, we show that these inactivated Leptospira strains are recognized by both mouse and human TLR5 reporter cells only after exposure to additional heat-treatment. Unfortunately, we were not able to confirm this in the canine system. Our data show that TLR2 and TLR4 are involved in the recognition of Leptospira strains used in the production of canine Leptospira vaccines. This study contributes to the understanding of Leptospira-induced innate immune responses in dogs, humans, and mice. Future studies are needed to further explore the role of canine TLR2, TLR4 and TLR5 in the induction of vaccine-mediated immunity against Leptospira.

Leptospira ainlahdjerensis sp. nov., Leptospira ainazelensis sp. nov., Leptospira abararensis sp. nov. and Leptospira chreensis sp. nov., four new species isolated from water sources in Algeria

Leptospira strains were isolated from freshwater sampled at four sites in Algeria and characterized by whole-genome sequencing and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The cells were spiral-shaped and motile. Phylogenetic and MALDI-TOF MS analyses showed that the strains can be clearly distinguished from the other described species in the genus Leptospira, therefore representing two novel species of the pathogen subclade P1 and two novel species of the saprophyte subclade S1. The names Leptospira ainlahdjerensis sp. nov. (type strain 201903070^T=KIT0297^T=CIP111912^T), Leptospira ainazelensis sp. nov. (201903071^T=KIT0298^T=CIP111913^T), Leptospira abararensis sp. nov. (201903074^T=KIT0299^T=CIP111914^T) and Leptospira chreensis (201903075^T=KIT0300^T=CIP111915^T) are proposed.

Transposable Prophages in Leptospira: An Ancient, Now Diverse, Group Predominant in Causative Agents of Weil's Disease

The virome associated with the corkscrew shaped bacterium Leptospira, responsible for Weil's disease, is scarcely known, and genetic tools available for these bacteria remain limited. To reduce these two issues, potential transposable prophages were searched in Leptospiraceae genomes. The 236 predicted transposable prophages were particularly abundant in the most pathogenic leptospiral clade, being potentially involved in the acquisition of virulent traits. According to genomic similarities and phylogenies, these prophages are distantly related to known transposable phages and are organized into six groups, one of them encompassing prophages with unusual TA-TA ends. Interestingly, structural and transposition proteins reconstruct different relationships between groups, suggesting ancestral recombinations. Based on the baseplate phylogeny, two large clades emerge, with specific gene-contents and high sequence divergence reflecting their ancient origin. Despite their high divergence, the size and overall genomic organization of all prophages are very conserved, a testimony to the highly constrained nature of their genomes. Finally, similarities between these prophages and the three known non-transposable phages infecting L. biflexa, suggest gene transfer between different Caudovirales inside their leptospiral host, and the possibility to use some of the transposable prophages in that model strain.

The FUR-like regulators PerRA and PerRB integrate a complex regulatory network that promotes mammalian host-adaptation and virulence of Leptospira interrogans

Leptospira interrogans, the causative agent of most cases of human leptospirosis, must respond to myriad environmental signals during its free-living and pathogenic lifestyles. Previously, we compared L. interrogans cultivated in vitro and in vivo using a dialysis membrane chamber (DMC) peritoneal implant model. From these studies emerged the importance of genes encoding the Peroxide responsive regulators PerRA and PerRB. First described in in Bacillus subtilis, PerRs are widespread in Gram-negative and -positive bacteria, where regulate the expression of gene products involved in detoxification of reactive oxygen species and virulence. Using perRA and perRB single and double mutants, we establish that L. interrogans requires at least one functional PerR for infectivity and renal colonization in a reservoir host. Our finding that the perRA/B double mutant survives at wild-type levels in DMCs is noteworthy as it demonstrates that the loss of virulence is not due to a metabolic lesion (i.e., metal starvation) but instead reflects dysregulation of virulence-related gene products. Comparative RNA-Seq analyses of perRA, perRB and perRA/B mutants cultivated within DMCs identified 106 genes that are dysregulated in the double mutant, including ligA, ligB and lvrA/B sensory histidine kinases. Decreased expression of LigA and LigB in the perRA/B mutant was not due to loss of LvrAB signaling. The majority of genes in the perRA and perRB single and double mutant DMC regulons were differentially expressed only in vivo, highlighting the importance of host signals for regulating gene expression in L. interrogans. Importantly, the PerRA, PerRB and PerRA/B DMC regulons each contain multiple genes related to environmental sensing and/or transcriptional regulation. Collectively, our data suggest that PerRA and PerRB are part of a complex regulatory network that promotes host adaptation by L. interrogans within mammals.

In vivo and in silico Virulence Analysis of Leptospira Species Isolated From Environments and Rodents in Leptospirosis Outbreak Areas in Malaysia

The zoonotic disease leptospirosis is caused by pathogenic species of the genus Leptospira. With the advancement of studies in leptospirosis, several new species are being reported. It has always been a query, whether Leptospira species, serovars, and strains isolated from different geographical locations contribute to the difference in the disease presentations and severity. In an epidemiological surveillance study performed in Malaysia, we isolated seven novel intermediate and saprophytic species (Leptospira semungkisensis, Leptospira fletcheri, Leptospira langatensis, Leptospira selangorensis, Leptospira jelokensis, Leptospira perdikensis, Leptospira congkakensis) from environments and three pathogenic species from rodents (Leptospira borgpetersenii strain HP364, Leptospira weilii strain SC295, Leptospira interrogans strain HP358) trapped in human leptospirosis outbreak premises. To evaluate the pathogenic potential of these isolates, we performed an in vivo and in silico virulence analysis. Environmental isolates and strain HP364 did not induce any clinical manifestations in hamsters. Strain SC295 caused inactivity and weight loss with histopathological changes in kidneys, however, all hamsters survived until the end of the experiment. Strain HP358 showed a high virulent phenotype as all infected hamsters died or were moribund within 7 days postinfection. Lungs, liver, and kidneys showed pathological changes with hemorrhage as the main presentation. In silico analysis elucidated the genome size of strain HP358 to be larger than strains HP364 and SC295 and containing virulence genes reported in Leptospira species and a high number of specific putative virulence factors. In conclusion, L. interrogans strain HP358 was highly pathogenic with fatal outcome. The constituent of Leptospira genomes may determine the level of disease severity and that needs further investigations.

Comparative Genomic Analysis and a Novel Set of Missense Mutation of the Leptospira weilii Serogroup Mini From the Urine of Asymptomatic Dogs in Thailand

Leptospira weilii belongs to the pathogenic Leptospira group and is a causal agent of human and animal leptospirosis in many world regions. L. weilii can produce varied clinical presentations from asymptomatic through acute to chronic infections and occupy several ecological niches. Nevertheless, the genomic feature and genetic basis behind the host adaptability of L. weilii remain elusive due to limited information. Therefore, this study aimed to examine the complete circular genomes of two new L. weilii serogroup Mini strains (CUDO6 and CUD13) recovered from the urine of asymptomatic dogs in Thailand and then compared with the 17 genomes available for L. weilii. Variant calling analysis (VCA) was also undertaken to gain potential insight into the missense mutations, focusing on the known pathogenesis-related genes. Whole genome sequences revealed that the CUDO6 and CUD13 strains each contained two chromosomes and one plasmid, with average genome size and G+C content of 4.37 Mbp and 40.7%, respectively. Both strains harbored almost all the confirmed pathogenesis-related genes in Leptospira. Two novel plasmid sequences, pDO6 and pD13, were identified in the strains CUDO6 and CUD13. Both plasmids contained genes responsible for stress response that may play important roles in bacterial adaptation during persistence in the kidneys. The core-single nucleotide polymorphisms phylogeny demonstrated that both strains had a close genetic relationship. Amongst the 19 L. weilii strains analyzed, the pan-genome analysis showed an open pan-genome structure, correlated with their high genetic diversity. VCA identified missense mutations in genes involved in endoflagella, lipopolysaccharide (LPS) structure, mammalian cell entry protein, and hemolytic activities, and may be associated with host-adaptation in the strains. Missense mutations of the endoflagella genes of CUDO6 and CUD13 were associated with loss of motility. These findings extend the knowledge about the pathogenic molecular mechanisms and genomic evolution of this important zoonotic pathogen.

Evaluation of a genus-specific rGroEL1-524 IgM-ELISA and commercial ELISA kits during the course of leptospirosis in Thailand

In the present study, we developed a genus-specific rGroEL_1-524 IgM-ELISA assay for use in screening diagnosis of suspected leptospirosis among acute undifferentiated febrile illness patients during acute fever. The diagnostic accuracies of the rGroEL_1–524 IgM-ELISA, commercial Panbio IgM-ELISA, and Virion-Serion Classic IgG-ELISA were evaluated using 133 Thai leptospirosis sera and 210 controls. Sensitivities were 91.7%, 59.6%, and 17.7% for acute infection, and the specificities were 92.6%, 90.2%, and 88.3% for the non-leptospirosis control, respectively. The rGroEL_1-524 IgM-ELISA had high sensitivity, at 92.3% and 91.7%, among culture-positive and MAT-negative cases at 1–3 days post-onset of symptoms (DPO1–3), respectively. Impaired specificity on scrub typhus was found, possibly from antibody cross-reaction to ortholog GroEL. Commercial Panbio IgM-ELISA had sensitivities at DPO1–3 of 30.8% and 41.7% for culture-positive and MAT-negative cases whereas Virion-Serion IgG-ELISA showed sensitivities of 5.9% and 13.3%, respectively. The rGroEL_1-524 IgM-ELISA could be useful as a screening test for early diagnosis. The performance of the commercial ELISA suggests the applicability of IgM-ELISA for diagnosis, while IgG-ELISA is useful for seroprevalence surveys. However, confirmation by reference tests is recommended.

Prevalence of Malaria and Leptospirosis Co-Infection among Febrile Patients: A Systematic Review and Meta-Analysis

Malaria and leptospirosis are important cosmopolitan infections that have emerged with overlapping geographic distribution, especially in tropical and subtropical regions. Therefore, co-infection with malaria and leptospirosis may occur in overlapping areas. The present study aimed to quantify the prevalence of malaria and leptospirosis co-infection among febrile patients. The association between malaria and leptospirosis infections was also investigated. Relevant studies that had reported malaria and leptospirosis co-infection were identified from PubMed, Scopus, and Web of Science. The risk of bias of the studies was assessed using the Joanna Briggs Institute (JBI) Critical Appraisal Tool. The pooled prevalence of malaria and leptospirosis co-infections among febrile patients and the pooled prevalence of leptospirosis infection among malaria patients were estimated using random effect models. The association between malaria and leptospirosis infection among febrile patients was estimated using random effect models. The outcomes of each study were shown in a forest plot in point estimate and 95% confidence interval (CI). Heterogeneity among the included studies was assessed using Cochran’s Q and quantified using I-squared statistics. For leptospirosis, subgroup analyses of countries, diagnostic tests, and participants’ age groups were performed to specify prevalence in each subgroup. Publication bias was assessed by funnel-plot visualization. Of the 2370 articles identified from the databases, 15 studies met the eligibility criteria and were included for qualitative and quantitative syntheses. Most of the included studies were conducted in India (5/15, 33.3%), Thailand (3/15, 20%), and Cambodia (2/15, 13.3%). Most of the enrolled cases were febrile patients (5838 cases) and malaria-positive patients (421 cases). The meta-analysis showed that the pooled prevalence of malaria and leptospirosis co-infection (86 cases) among febrile patients was 1% (95% CI: 1–2%, I²: 83.3%), while the pooled prevalence of leptospirosis infection (186 cases) among malaria patients was 13% (95% CI: 9–18%, I²: 90.3%). The meta-analysis showed that malaria and leptospirosis co-infections occurred by chance (p: 0.434, OR: 1.4, 95% CI: 0.6–3.28, I²: 85.2%). The prevalence of malaria in leptospirosis co-infection among febrile patients in the included studies was low. Co-infection was likely to occur by chance. However, as clinical symptoms of leptospirosis patients were non-specific and not distinguishable from symptoms of malaria patients, clinicians caring for febrile patients in an area where those two diseases are endemic should maintain a high index of suspicion for both diseases and whether mono-infections or co-infections are likely. Recognition of this co-infection may play an important role in reducing disease severity and treatment duration.

Next-Generation Sequencing Analysis of Pathogenic Leptospira: A Way Forward for Understanding Infectious Disease Dynamics in Low/Middle-Income, Disease-Endemic Settings

In the current genomic era, knowledge of diversity of Leptospira, the spirochetal agents of leptospirosis, is changing rapidly. Next-generation sequencing has decreased in price and increased in scale, with the potential to democratize large-scale analysis of pathogens in resource-limited, low/middle-income (LMIC) regions. Consequently, the molecular classification of Leptospira, a pathogen disproportionately affecting LMIC countries, has changed dramatically over the last decade. Leptospira classification and molecular understandings of pathogen diversity have rapidly evolved, now most precisely based on core genome analysis supplemented by new insights provided by culture-independent methods directly using body fluids such as blood and urine. In places where leptospirosis disease burden is highest, genomic technologies have not been available, and serology-based methods remain the mainstay of leptospiral classification. Understanding the epidemiology, pathogenesis, and ultimately new approaches to treating and preventing leptospirosis requires detailed knowledge of regionally circulating Leptospira in highly endemic settings. Next-generation sequencing-based, culture-independent typing overcomes the limitation of culture isolation of Leptospira from clinical samples, with promise of providing public health-actionable information applicable to leptospirosis-endemic LMIC settings.

Characterizing the transcripts of Leptospira CRISPR I-B array and its processing with endoribonuclease LinCas6

In Leptospira interrogans serovar Copenhageni, the CRISPR-Cas I-B locus possesses a CRISPR array between the two independent cas-operons. Using the reverse transcription-PCR and the in vitro endoribonuclease assay with Cas6 of Leptospira (LinCas6), we account that the CRISPR is transcriptionally active and is conventionally processed. The LinCas6 specifically excises at one site within the synthetic cognate repeat RNA or the repeats of precursor-CRISPR RNA (pre-crRNA) in the sense direction. In contrast, the antisense repeat RNA is cleaved at multiple sites. LinCas6 functions as a single turnover endoribonuclease on its repeat RNA substrate, where substitution of one of predicted active site residues (His38) resulted in reduced activity. This study highlights the comprehensive understanding of the Leptospira CRISPR array transcription and its processing by LinCas6 that is central to RNA-mediated CRISPR-Cas I-B adaptive immunity.

Vinetz J. 12 Novel clonal groups of Leptospira infecting humans in multiple contrasting epidemiological contexts in Sri Lanka

Leptospirosis is a ubiquitous zoonotic disease and a major clinical challenge owing to the multitude of clinical presentations and manifestations that are possibly attributable to the diversity of Leptospira, the understanding of which is key to study the epidemiology of this emerging global disease threat. Sri Lanka is a hotspot for leptospirosis with high levels of endemicity as well as annual epidemics. We carried out a prospective study of Leptospira diversity in Sri Lanka, covering the full range of climatic zones, geography, and clinical severity. Samples were collected for leptospiral culture from 1,192 patients from 15 of 25 districts in Sri Lanka over two and half years. Twenty-five isolates belonging to four pathogenic Leptospira species were identified: L. interrogans, L. borgpetersenii, L. weilii, and L. kirschneri. At least six serogroups were identified among the isolates: Autumnalis (6), Pyrogenes (4), Icterohaemorrhagiae (2), Celledoni (1), Grippotyphosa (2) and Bataviae (1). Seven isolates did not agglutinate using available antisera panels, suggesting new serogroups. Isolates were sequenced using an Illumina platform. These data add 25 new core genome sequence types and were clustered in 15 clonal groups, including 12 new clonal groups. L. borgpetersenii was found only in the dry zone and L. weilii only in the wet zone. Acute kidney injury and cardiovascular involvement were seen only with L. interrogans infections. Thrombocytopenia and liver impairment were seen in both L. interrogans and L. borgpetersenii infections. The inadequate sensitivity of culture isolation to identify infecting Leptospira species underscores the need for culture-independent typing methods for Leptospira.

There is a huge diversity in pathogenic Leptospira species worldwide, and our knowledge of the currently circulating species is deficient owing to limited isolation and identification of Leptospira species from endemic countries. This prospective study reveals the wide pathogen diversity that causes human leptospirosis in Sri Lanka, representing four species, more than six serogroups, and fifteen clonal groups. Further, the different geographic and climatic zone distributions and clinical manifestations observed underscores the need for prospective studies to expand the molecular epidemiological approaches to combat leptospirosis.

Anti-Leptospira immunoglobulin profiling in mice reveals strain specific IgG and persistent IgM responses associated with virulence and renal colonization

Leptospira interrogans is a pathogenic spirochete responsible for leptospirosis, a neglected, zoonotic reemerging disease. Humans are sensitive hosts and may develop severe disease. Some animal species, such as rats and mice can become asymptomatic renal carriers. More than 350 leptospiral serovars have been identified, classified on the basis of the antibody response directed against the lipopolysaccharide (LPS). Similarly to whole inactivated bacteria used as human vaccines, this response is believed to confer only short-term, serogroup-specific protection. The immune response of hosts against leptospires has not been thoroughly studied, which complicates the testing of vaccine candidates. In this work, we studied the immunoglobulin (Ig) profiles in mice infected with L. interrogans over time to determine whether this humoral response confers long-term protection after homologous challenge six months post-infection. Groups of mice were injected intraperitoneally with 2×10⁷ leptospires of one of three pathogenic serovars (Manilae, Copenhageni or Icterohaemorrhagiae), attenuated mutants or heat-killed bacteria. Leptospira-specific immunoglobulin (IgA, IgM, IgG and 4 subclasses) produced in the first weeks up to 6 months post-infection were measured by ELISA. Strikingly, we found sustained high levels of IgM in mice infected with the pathogenic Manilae and Copenhageni strains, both colonizing the kidney. In contrast, the Icterohaemorrhagiae strain did not lead to kidney colonization, even at high dose, and triggered a classical IgM response that peaked at day 8 post-infection and disappeared. The virulent Manilae and Copenhageni serovars elicited high levels and similar profiles of IgG subclasses in contrast to Icterohaemorrhagiae strains that stimulated weaker antibody responses. Inactivated heat-killed Manilae strains elicited very low responses. However, all mice pre-injected with leptospires challenged with high doses of homologous bacteria did not develop acute leptospirosis, and all antibody responses were boosted after challenge. Furthermore, we showed that 2 months post-challenge, mice pre-infected with the attenuated M895 Manilae LPS mutant or heat-killed bacterin were completely protected against renal colonization. In conclusion, we observed a sustained IgM response potentially associated with chronic leptospiral renal infection. We also demonstrated in mice different profiles of protective and cross-reactive antibodies after L. interrogans infection, depending on the serovar and virulence of strains.

Leptospira interrogans is a pathogenic spirochete responsible for leptospirosis, a neglected zoonotic reemerging disease. The immune response of hosts against these bacteria has not been thoroughly studied. Here, we studied over 6 months the antibody profiles in mice infected with L. interrogans and determined whether this humoral response confers long-term protection after homologous challenge six months after primary infection. Groups of mice were infected intraperitoneally with 2×10⁷ bacteria of one of three different pathogenic serovars (Manilae, Copenhageni and Icterohaemorrhagiae) and some corresponding attenuated avirulent mutants. We measured by ELISA each type of Leptospira-specific immunoglobulin (Ig) (IgA, IgM, IgG and 4 subclasses) produced in the first weeks up to 6 months post-infection and studied their cross-reactivities among serovars. We showed different profiles of antibody response after L. interrogans challenge in mice, depending on the serovar and virulence of strains. However, all infected mice, including the ones harboring low antibody levels, like mice vaccinated with an inactivated, heat-killed strain, were protected against leptospirosis after challenge. Notably, we also showed an unusual sustained IgM response associated with chronic leptospiral colonization. Altogether, this long-term immune protection is different from what is known in humans and warrants further investigation.

Isolation and Culture of Leptospira from Clinical and Environmental Samples

Leptospires, the etiological agents of leptospirosis, are fastidious slow-growing organisms. Here we describe the isolation and routine maintenance of leptospires from clinical (blood, urine, or tissue) and environmental (water or soil) samples. Using combinations of filtration, agar plating, and selective agents, leptospires can be isolated in pure cultures even from complex contaminated sources in standard EMJH culture medium.

Exposure to Leptospira spp. and Associated Risk Factors in the Human, Cattle and Dog Populations in Bhutan

Leptospirosis is a neglected worldwide zoonotic bacterial disease with a high prevalence in subtropical and tropical countries. The prevalence of Leptospira spp. in humans, cattle and dogs is unknown in Bhutan. Therefore, we sought to find out whether humans, cattle or dogs had been infected in the past with leptospires by measuring antibodies in the serum. We therefore collected blood from 864 humans ≥13 years of age, 130 bovines and 84 dogs from different rural and urban areas in Bhutan and tested the serum for antibodies specific for leptospires with a screening of enzyme-linked immunosorbent assays (ELISA) and a confirmatory microscopic agglutination test (MAT). In humans, 17.6% were seropositive by ELISA and 1.6% by MAT. The seropositivity was stronger in bovines (36.9%) and dogs (47.6%). "Having had a fever recently" (OR 5.2, p = 0.004), "working for the military" (OR 26.6, p = 0.028) and "being unemployed" (OR 12.9, p = 0.041) (reference category = housemaker) were statistically significantly associated with seropositivity when controlled for the effects of other risk factors. However, due to the small number of positive test results, the findings on risk factors should be interpreted with caution. Based on the serogroups found in the three species, dogs could be a source of infection for humans, or dogs and humans are exposed to the same environmental risk factors Clinical leptospirosis in humans and domestic animals should be investigated by testing blood and urine for the presence of leptospires by molecular methods (qPCR).

Leptospira interrogans serogroup Pomona strains isolated from river buffaloes

At present, little is known regarding the prevalence of buffalo leptospirosis worldwide, especially with respect to which Leptospira strains may infect this animal species. Furthermore, most investigations into this disease in buffaloes have only been performed with serological studies. In Brazil, particularly in the Amazon, buffalo production is growing and is just as important as cattle production, although few studies have been performed on buffalo compared to cattle. Thus, the aim of this study was to isolate and characterise Leptospira strains from river buffaloes raised in the Brazilian Amazon region. We collected 109 kidney samples from slaughtered buffaloes raised in the Amazon Delta region of Brazil. The samples were analysed by bacteriological culture for the isolation of leptospires, and the obtained isolates were serologically and molecularly characterised by microscopic agglutination test (MAT), DNA sequencing and multiple locus variable-number tandem repeat analysis (MLVA). Five isolates were obtained, and in serogrouping analyses, these isolates were only reactive for the Pomona serogroup, with an observed titre of 25,600. The DNA sequencing results revealed that all the isolates belonged to the species Leptospira interrogans, and the MLVA results showed that the VNTR loci 4, 7 and 10 profile of all the isolates was 4-1-10. In this study, we observed that Pomona serogroup strains circulate in buffaloes in the Amazon, showing that in Brazil, buffaloes can be affected by Leptospira strains other than the Sejroe group, which are adapted to cattle.

Pangenome analysis reveals genetic isolation in Campylobacter hyointestinalis subspecies adapted to different mammalian hosts

Campylobacter hyointestinalis is an emerging pathogen currently divided in two subspecies: C. hyointestinalis subsp. lawsonii which is predominantly recovered from pigs, and C. hyointestinalis subsp. hyointestinalis which can be found in a much wider range of mammalian hosts. Despite C. hyointestinalis being reported as an emerging pathogen, its evolutionary and host-associated diversification patterns are still vastly unexplored. For this reason, we generated whole-genome sequences of 13 C. hyointestinalis subsp. hyointestinalis strains and performed a comprehensive comparative analysis including publicly available C. hyointestinalis subsp. hyointestinalis and C. hyointestinalis subsp. lawsonii genomes, to gain insight into the genomic variation of these differentially-adapted subspecies. Both subspecies are distinct phylogenetic lineages which present an apparent barrier to homologous recombination, suggesting genetic isolation. This is further supported by accessory gene patterns that recapitulate the core genome phylogeny. Additionally, C. hyointestinalis subsp. hyointestinalis presents a bigger and more diverse accessory genome, which probably reflects its capacity to colonize different mammalian hosts unlike C. hyointestinalis subsp. lawsonii that is presumably host-restricted. This greater plasticity in the accessory genome of C. hyointestinalis subsp. hyointestinalis correlates to a higher incidence of genome-wide recombination events, that may be the underlying mechanism driving its diversification. Concordantly, both subspecies present distinct patterns of gene families involved in genome plasticity and DNA repair like CRISPR-associated proteins and restriction-modification systems. Together, our results provide an overview of the genetic mechanisms shaping the genomes of C. hyointestinalis subspecies, contributing to understand the biology of Campylobacter species that are increasingly recognized as emerging pathogens.

Leptospira in river and soil in a highly endemic area of Ecuador

BACKGROUND

Leptospira are shed into the environment via urine of infected animals. Rivers are thought to be an important risk factor for transmission to humans, though much is unknown about the types of environment or characteristics that favor survival. To address this, we screened for Leptospira DNA in two rivers in rural Ecuador where Leptospirosis is endemic.

RESULTS

We collected 112 longitudinal samples and recorded pH, temperature, river depth, precipitation, and dissolved oxygen. We also performed a series of three experiments designed to provide insight into Leptospira presence in the soil. In the first soil experiment, we characterized prevalence and co-occurrence of Leptospira with other bacterial taxa in the soil at dispersed sites along the rivers (n = 64). In the second soil experiment, we collected 24 river samples and 48 soil samples at three points along eight transects to compare the likelihood of finding Leptospira in the river and on the shore at different distances from the river. In a third experiment, we tested whether Leptospira presence is associated with soil moisture by collecting 25 soil samples from two different sites. In our river experiment, we found pathogenic Leptospira in only 4 (3.7%) of samples. In contrast, pathogenic Leptospira species were found in 22% of shore soil at dispersed sites, 16.7% of soil samples (compared to 4.2% of river samples) in the transects, and 40% of soil samples to test for associations with soil moisture.

CONCLUSIONS

Our data are limited to two sites in a highly endemic area, but the scarcity of Leptospira DNA in the river is not consistent with the widespread contention of the importance of river water for leptospirosis transmission. While Leptospira may be shed directly into the river, onto the shores, or washed into the river from more remote sites, massive dilution and limited persistence in rivers may reduce the environmental load and therefore, the epidemiological significance of such sources. It is also possible that transmission may occur more frequently on shores where people are liable to be barefoot. Molecular studies that further explore the role of rivers and water bodies in the epidemiology of leptospirosis are needed.

Potentially Pathogenic Leptospira in the Environment of an Elephant Camp in Thailand

Leptospira is the causative agent of leptospirosis, a globally emerging zoonotic disease. The infection is commonly acquired through contact with the contaminated environment. To extend the knowledge on environmental source of leptospirosis, we investigated the presence of Leptospira in an elephant camp setting where the interaction between humans, animals, and the shared environment occur particularly when engaging in recreational activities. In this study, a total of 24 environmental samples were collected from an elephant camp area in western Thailand. All samples were processed for Leptospira isolation using the EMJH medium. The identification of Leptospira species was carried out by partial 16S rRNA and secY gene sequencing. Of those 24 samples, 18 samples (75%) were culture-positive for Leptospira. The recovered leptospires were mostly derived from water and soil sampled from a river and a mud pond, the main areas for recreational activities. The majority of the isolates were classified into “Pathogens” clade (89%, 16/18) and more than half of the isolates (61%, 11/18) contained species of the “Saprophytes” clade. Notably, two soil isolates from the river beach sampling area were found to contain leptospiral DNA with high similarity to the pathogenic L. interrogans and L. santarosai. The evidence of diverse Leptospira species, particularly those belonging to the “Pathogens” clade, suggest that the shared environments of an elephant camp can serve as potential infection source and may pose a risk to the elephant camp tourists and workers.

Diverse Epidemiology of Leptospira serovars Notified in New Zealand, 1999-2017

Leptospirosis in New Zealand has been strongly associated with animal-contact occupations and with serovars Hardjo and Pomona. However, recent data suggest changes in these patterns, hence, serovar-specific epidemiology of leptospirosis from 1999 to 2017 was investigated. The 19-year average annual incidence is 2.01/100,000. Early (1999-2007) and late (2008-2017) study period comparisons showed a significant increase in notifications with serovar Ballum (IRR: 1.59, 95% CI: 1.22-2.09) in all cases and serovar Tarassovi (IRR: 1.75, 95% CI: 1.13-2.78) in Europeans and a decrease in notifications with serovars Hardjo and Pomona in all cases. Incidences of Ballum peaked in winter, Hardjo peaked in spring and Tarassovi peaked in summer. Incidence was highest in Māori (2.24/100,000) with dominant serovars being Hardjo and Pomona. Stratification by occupation showed meat workers had the highest incidence of Hardjo (57.29/100,000) and Pomona (45.32/100,000), farmers had the highest incidence of Ballum (11.09/100,000) and dairy farmers had the highest incidence of Tarassovi (12.59/100,000). Spatial analysis showed predominance of Hardjo and Pomona in Hawke's Bay, Ballum in West Coast and Northland and Tarassovi in Waikato, Taranaki and Northland. This study highlights the serovar-specific heterogeneity of human leptospirosis in New Zealand that should be considered when developing control and prevention strategies.

Whole genome sequencing and de novo assembly of three virulent Indian isolates of Leptospira

Leptospirosis is a re-emerging bacterial zoonosis caused by pathogenic Leptospira, with a worldwide distribution and becoming a major public health concern. Prophylaxis of this disease is difficult due to several factors such as non-specific variable clinical manifestation, presence of a large number of serovar, species and asymptomatic reservoir hosts, lack of proper diagnostics and vaccines. Despite its global importance and severity of the disease, knowledge about the molecular mechanism of pathogenesis and evolution of pathogenic species of Leptospira remains limited. In this study, we sequenced and analyzed three highly pathogenic species of Indian isolates of Leptospira (interrogans, santarosai, and kirschneri). Additionally, we identified some virulence-related and CRISPR-Cas genes. The virulent analysis showed 232 potential virulence factors encoding proteins in L. interrogans strain Salinem and L. santarosai strain M-4 genome. While the genome of L. kirschneri strain Wumalasena was predicted to encode 198 virulence factor proteins. The variant calling analysis revealed 1151, 19,786, and 22,996 single nucleotide polymorphisms (SNPs) for L. interrogans strain Salinem, L. kirschneri strain Wumalasena and L. santarosai strain M-4, respectively, with a maximum of 5315 missense and 12,221 synonymous mutations for L. santarosai strain M-4. The structural analyses of genomes indicated potential evidence of inversions and structural rearrangment in all three genomes. The availability of these genome sequences and in silico analysis of Leptospira will provide a basis for a deeper understanding of their molecular diversity and pathogenesis mechanism, and further pave a way towards proper management of the disease.

Detection of Pathogenic Leptospires in Water and Soil in Areas Endemic to Leptospirosis in Nicaragua

In Nicaragua, there are ideal environmental conditions for leptospirosis. The objective of this investigation was to detect pathogenic and saprophytic leptospires in water and soil samples from leptospirosis-endemic areas in Nicaragua. Seventy-eight water and 42 soil samples were collected from houses and rivers close to confirmed human cases. Leptospira spp was isolated in Ellinghausen–McCullough–Johnson–Harris (EMJH) culture medium with 5-fluororacil and positive samples were analyzed through PCR for the LipL32 gene, specific for pathogenic leptospires (P1 clade). There were 73 positive cultures from 120 samples, however only six of these (5% of all collected samples) were confirmed to be pathogenic, based on the presence of the LipL32 gene (P1 clade). Of these six pathogenic isolates, four were from Leon and two from Chinandega. Four pathogenic isolates were obtained from water and two from soil. This study proved the contamination of water and soil with pathogenic leptospires, which represents a potential risk for public health.

Seven Years Leptospirosis Follow-Up in a Critical Care Unit of a French Metropolitan Hospital; Role of Real Time PCR for a Quick and Acute Diagnosis

(1) Background: Leptospirosis infection can lead to multiple organ failure, requiring hospitalization in an intensive care unit for supportive care, along with initiation of an adapted antibiotic therapy. Achieving a quick diagnosis is decisive in the management of these patients. (2) Methods: We present here a review of leptospirosis cases diagnosed in the intensive care unit of our hospital over seven years. Clinical and biological data were gathered, and we compared the differences in terms of diagnostic method. (3) Results: Molecular biology method by Polymerase Chain Reaction (PCR) allowed quick and reliable diagnosis when performed in the first days after the symptoms began. Moreover, we identified that sampling blood and urine for PCR was more efficient than performing PCR on only one type of biological sample. (4) Conclusions: Our results confirm the efficiency of PCR for the quick diagnosis of leptospirosis and suggest that testing both blood and urine early in the disease might improve diagnosis.

Understanding leptospirosis eco-epidemiology by environmental DNA metabarcoding of irrigation water from two agro-ecological regions of Sri Lanka

Background

Leptospirosis is one of the most significant zoonoses across the world not only because of its impact on human and animal health but also because of the economic and social impact on agrarian communities. Leptospirosis is endemic in Sri Lanka where paddy farming activities, the use of draught animals in agriculture, and peridomestic animals in urban and rural areas play important roles in maintaining the infection cycle of pathogenic Leptospira, especially concerning animals as a potential reservoir. In this study, an environmental DNA (eDNA) metabarcoding methodology was applied in two different agro-ecological regions of Sri Lanka to understand the eco-epidemiology of leptospirosis.

Methodology/Principal findings

Irrigation water samples were collected in Kandy District (wet zone mid-country region 2) and Girandurukotte, Badulla District (intermediate zone low-country region 2); and analysed for the presence of pathogenic Leptospira, associated microbiome and the potential reservoir animals. Briefly, we generated PCR products for high-throughput sequencing of multiple amplicons through next-generation sequencing. The analysis of eDNA showed different environmental microbiomes in both regions and a higher diversity of Leptospira species circulating in Kandy than in Girandurukotte. Moreover, the number of sequence reads of pathogenic Leptospira species associated with clinical cases such as L. interrogans was higher in Kandy than in Girandurukotte. Kandy also showed more animal species associated with pathogenic bacterial species than Girandurukotte. Finally, several pathogenic bacterial species including Arcobacter cryaerophilus, responsible for abortion in animals, was shown to be associated with pathogenic Leptospira.

Conclusions/Significance

Leptospirosis has been considered to be endemic in wet regions, consistently, leptospiral sequences were detected strongly in Kandy. The great Leptospira species diversity in Kandy observed in this study shows that the etiological agents of leptospirosis in Sri Lanka might be underestimated. Furthermore, our eDNA metabarcoding can be used to discriminate bacterial and animal species diversity in different regions and to explore environmental microbiomes to identify other associated bacterial pathogens in the environment.

Leptospirosis is a widespread bacterial zoonosis with increasing importance due to its vast range of reservoir hosts. Early symptoms are shared by other infectious diseases common in tropical and sub-tropical regions, where the real burden and risk factors need to be known. In Sri Lanka, leptospirosis is mostly an occupational disease associated with freshwater or animal exposure in agriculture communities. Thus, there is a need for understanding the epidemiology of leptospirosis in agrarian regions of the country for developing better prevention and intervention strategies. In this study, we applied an environmental DNA metabarcoding methodology to understand the environmental microbiome, potential reservoir animals and the Leptospira species circulating in two different agro-ecological regions of Sri Lanka: Kandy (wet region mid-country region 2) and Girandurukotte (intermediate region low-country region 2). It is known that pathogenic Leptospira are excreted through the urine of reservoir animals in the environment, where they can persist in humid conditions. Congruently, this study showed a higher detection of pathogenic Leptospira in the environment of Kandy where the environmental microbiome showed a higher diversity than Girandurukotte. Potential animal reservoirs were also detected in samples positive for pathogenic Leptospira, suggesting that environmental DNA metabarcoding can provide important information for management and intervention strategies to control leptospirosis.

Survival time of Leptospira kirschneri serovar Grippotyphosa under different environmental conditions

Leptospirosis is a re-emerging zoonotic disease of high medical importance that affects humans worldwide. Humans or animals acquire an infection with pathogenic leptospires either by direct contact with infected animals or by indirect contact to contaminated environment. Survival of Leptospira spp. in the environment after having been shed via animal urine is thus a key factor to estimate the risk of infection, but not much is known about the tenacity of pathogenic leptospires. Here, the survival time of both a laboratory strain and a field strain of L. kirschneri serovar Grippotyphosa in animal urine and their tenacity while drying was investigated and compared at different temperatures (15°C-37°C). Leptospira spp. are also often found in rivers and ponds. As the infection risk for humans and animals also depends on the spreading and survival of Leptospira spp. in these environments, the survival of L. kirschneri serovar Grippotyphosa was investigated using a 50-meter-long hose system simulating a water stream. Both strains did not survive in undiluted cattle or dog urine. Comparing different temperatures and dilution media, the laboratory strain survived the longest in diluted cattle urine with a slightly alkaline pH value (3 days), whilst the field strain survived in diluted dog urine with a slightly acid pH value up to a maximum of 24 h. Both strains did not survive drying on a solid surface. In a water stream, leptospires were able to move faster or slower than the average velocity of the water due to their intrinsic mobility but were not able to survive the mechanical damage caused by running water in the hose system. From our results we conclude, that once excreted via animal urine, the leptospires immediately need moisture or a water body to survive and stay infectious.

Use of MALDI-ToF Mass Spectrometry for Identification of Leptospira

Medical microbiology has used phenotypical and metabolic criteria to identify bacterial pathogens for decades. However, no such criteria have been applied to identify leptospires at the species level. In the recent years, matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry (MS) has emerged as new tool for the identification of bacterial species in the medical microbiology laboratory. This technology has rapidly gained more and more popularity. Actually, this technique is sensitive and economic, saving both labor and bench costs, but also rapid, significantly reducing turnaround time from isolation to identification. MALDI-ToF MS provides an unprecedented tool for the rapid identification of Leptospira at the species level.

Environmental Risk of Leptospirosis in Animals: The Case of The Republic of Sakha (Yakutia), Russian Federation

Leptospirosis is a zoonotic natural focal disease caused by the pathogenic bacteria Leptospira. Its spread is related to certain ecological factors. The aim of the current research was to assess potential exposure to the infection as a function of environmental determinants in the Republic of Sakha (Yakutia), Russian Federation. We applied environmental niche modeling using leptospirosis cases in livestock and wild animals in 1995–2019 with regard to a set of landscape, climatic, and socioeconomic variables, both for the current climate and for the projected climate for 2041–2060. The MaxEnt model performed well (AUC = 0.930), with the mean temperature of the warmest quarter, mean diurnal range, land cover type, and altitude being the most contributing variables. Consequent zoning based on the proportion of high-risk cells within each administrative unit suggested that five out of the 36 districts of the Republic are at high risk in the current climate conditions, with three more districts expected to demonstrate a high risk by 2060. This study presents the first-ever attempt at leptospirosis ecological modeling in Russia. Its results correspond well to the findings of other authors and underline the importance of considering ecological factors when conducting a leptospirosis risk assessment.

Isolation and propagation of leptospires at 37 °C directly from the mammalian host

The causative agent of leptospirosis includes multiple serovars and species of pathogenic leptospires that are excreted via urine from reservoir hosts of infection. Primary isolation takes weeks to months, and is limited to semi-solid media at 28-30 °C. Here we present an alternative media formulation, HAN, compared to commercially available EMJH and the more specialized T80/40/LH media formulations, in semi-solid and liquid compositions, for the primary isolation of two diverse species and serovars of pathogenic leptospires directly from host kidney tissue. All three media types supported the isolation and propagation of L. interrogans serovar Copenhageni strain IC:20:001 in semi-solid media at 29 °C. However, only HAN and T80/40/LH supported the growth of L. borgpetersenii serovar Hardjo strain HB15B203 at 29 °C. In addition, HAN supported primary isolation at 37 °C. Both T80/40/LH and HAN supported primary isolation of strain IC:20:001 in liquid media at 29 °C but only HAN supported growth of strain HB15B203 in liquid media, at both 29 and 37 °C. HAN media supports the primary isolation of fastidious pathogenic leptospires directly from infected host tissue at either 29 or 37 °C: this formulation represents a more defined media for the continued optimization of growth factors required to support the primary isolation of the large and diverse range of species and serovars within the genus Leptospira circulating within domestic and wild animal populations.

Optimization of Culture Protocols to Isolate Leptospira spp. from Environmental Water, Field Investigation, and Identification of Factors Associated with the Presence of Leptospira spp. in the Environment

The successful culture of Leptospira spp. from the environment is challenging. Here, we optimized the isolation of Leptospira spp. from water samples spiked with different species and initial concentrations of this organism. The time periods between water sampling and the isolation process were varied (0, 2, and 4 weeks). Bacterial cultures were observed under a microscope, and cultures were graded for cell density, weekly, for 12 weeks. Most pathogenic Leptospira spp. were difficult to culture under all conditions. All conditions of water samples spiked with novel species of Leptospira subclade P1 were culture positive within 2 weeks. For Leptospira subclade P2, storing samples for 2 weeks prior to isolation resulted in more successful isolation compared with isolation after other storage conditions. For subclade S1, all samples with initial bacterial concentrations of more than 10³ colonies/mL, under all storage conditions, were successfully cultured. These results suggest that storing contaminated water samples for 2 to 4 weeks in the dark at an ambient temperature prior to culturing can improve the isolation of Leptospira spp. from the samples. We implemented this protocol and collected water samples from natural sources accessed by both humans and animals. Leptospira spp. was identified in 32% (35/109) of water samples. The animal species using a water source influenced the likelihood of water samples being contaminated with Leptospira spp. Cultures of Leptospira spp. from environmental samples can provide useful information for understanding the complex interactions between humans, animals and the environment in the transmission of leptospirosis.

Pathogenic Leptospira and their animal reservoirs: testing host specificity through experimental infection

Leptospirosis is caused by pathogenic Leptospira transmitted through contact with contaminated environments. Most mammalian species are infectable by Leptospira but only few act as efficient reservoir being capable of establishing long term kidney colonization and shedding Leptospira in urine. In Madagascar, a large diversity of pathogenic Leptospira display a tight specificity towards their endemic volant or terrestrial mammalian hosts. The basis of this specificity is unknown: it may indicate some genetically determined compatibility between host cells and bacteria or only reflect ecological constraints preventing contacts between specific hosts. In this study, Rattus norvegicus was experimentally infected with either Leptospira interrogans, Leptospira borgpetersenii or Leptospira mayottensis isolated from rats, bats or tenrecs, respectively. Leptospira borgpetersenii and L. mayottensis do not support renal colonization as featured by no shedding of live bacteria in urine and low level and sporadic detection of Leptospira DNA in kidneys. In contrast 2 out of the 7 R. norvegicus challenged with L. interrogans developed renal colonization and intense Leptospira shedding in urine throughout the 3 months of experimental infection. These data suggest that host-Leptospira specificity in this biodiversity hotspot is driven at least in part by genetic determinants likely resulting from long-term co-diversification processes.

Leptospira interrogans and Leptospira kirschneri are the dominant Leptospira species causing human leptospirosis in Central Malaysia

BACKGROUND

Leptospirosis, commonly known as rat-urine disease, is a global but endemic zoonotic disease in the tropics. Despite the historical report of leptospirosis in Malaysia, the information on human-infecting species is limited. Determining the circulating species is important to understand its epidemiology, thereby to strategize appropriate control measures through public health interventions, diagnostics, therapeutics and vaccine development.

METHODOLOGY/PRINCIPLE FINDINGS

We investigated the human-infecting Leptospira species in blood and serum samples collected from clinically suspected leptospirosis patients admitted to three tertiary care hospitals in Malaysia. From a total of 165 patients, 92 (56%) were confirmed cases of leptospirosis through Microscopic Agglutination Test (MAT) (n = 43; 47%), Polymerase Chain Reaction (PCR) (n = 63; 68%) or both MAT and PCR (n = 14; 15%). The infecting Leptospira spp., determined by partial 16S rDNA (rrs) gene sequencing revealed two pathogenic species namely Leptospira interrogans (n = 44, 70%) and Leptospira kirschneri (n = 17, 27%) and one intermediate species Leptospira wolffii (n = 2, 3%). Multilocus sequence typing (MLST) identified an isolate of L. interrogans as a novel sequence type (ST 265), suggesting that this human-infecting strain has a unique genetic profile different from similar species isolated from rodents so far.

CONCLUSIONS/SIGNIFICANCE

Leptospira interrogans and Leptospira kirschneri were identified as the dominant Leptospira species causing human leptospirosis in Central Malaysia. The existence of novel clinically important ST 265 (infecting human), that is different from rodent L. interrogans strains cautions reservoir(s) of these Leptospira lineages are yet to be identified.

Leptospira yasudae sp. nov. and Leptospira stimsonii sp. nov., two new species of the pathogenic group isolated from environmental sources

Four spirochetes (F1T, B21, YaleT and AMB6-RJ) were isolated from environmental sources: F1T and B21 from soils of an urban slum community in Salvador (Brazil), YaleT from river water in New Haven, Connecticut (USA) and AMB6-RJ from a pond in a horse farm in Rio de Janeiro (Brazil). Isolates were helix-shaped, aerobic, highly motile and non-virulent in a hamster model of infection. Draft genomes of the strains were obtained and analysed to determine the relatedness to other species of the genus Leptospira. The analysis of 498 core genes showed that strains F1T/B21 and YaleT/AMB6-RJ formed two distinct phylogenetic clades within the 'Pathogens' group (group I). The average nucleotide identity (ANI) values of strains F1T/B21 and YaleT/AMB6-RJ to other previously described Leptospira species were below <84 % and <82 %, respectively, which confirmed that these isolates should be classified as representatives of two novel species. Therefore, we propose Leptospirayasudae sp. nov. and Leptospirastimsonii sp. nov. as new species in the genus Leptospira. The type strains are F1T (=ATCC-TSD-163=KIT0259=CLEP00287) and YaleT (=ATCC-TDS-162=KIT0258=CLEP00288), respectively.