Global proteome of the saprophytic strain Leptospira biflexa and comparative analysis with pathogenic strain Leptospira interrogans uncover new pathogenesis mechanisms

Leptospira is a genus of bacteria that includes free-living saprophytic species found in water or soil, and pathogenic species, which are the etiologic agents of leptospirosis. Besides all the efforts, there are only a few proteins described as virulence factors in the pathogenic strain L. interrogans. This work aims to perform L. biflexa serovar Patoc1 strain Paris global proteome and to compare with the proteome database of pathogenic L. interrogans serovar Copenhageni strain Fiocruz L1-130. We identified a total of 2327 expressed proteins of L. biflexa by mass spectrometry. Using the Get Homologues software with the global proteome of L. biflexa and L. interrogans, we found orthologous proteins classified into conserved, low conserved, and specific proteins. Comparative bioinformatic analyses were performed to understand the biological functions of the proteins, subcellular localization, the presence of signal peptide, structural domains, and motifs using public softwares. These results lead to the selection of 182 low conserved within the saprophyte, and 176 specific proteins of L. interrogans. It is anticipated that these findings will indicate further studies to uncover virulence factors in the pathogenic strain. This work presents for the first time the global proteome of saprophytic strain L. biflexa serovar Patoc, strain Patoc1. SIGNIFICANCE: The comparative analysis established an array of specific proteins in pathogenic strain that will narrow down the identification of immune protective proteins that will help fight leptospirosis.

Non-purulent myositis caused by direct invasion of skeletal muscle tissue by Leptospira in a hamster model

Myalgia is a common symptom of Leptospira infection in humans. Autopsies have reported that muscle tissue shows degeneration and necrosis of the myofibers and infiltration of inflammatory cells composed mainly of macrophages and lymphocytes. It remains unclear whether Leptospira directly infects the muscle and how the infiltrating inflammatory cells are involved in muscle fiber destruction. This study evaluated the relationship between histopathological changes and leptospiral localization in the muscle tissue of a hamster model. The influence of macrophages in skeletal muscle injury was also investigated, using selective depletion of macrophages by administration of liposomal clodronate. Hamsters infected subcutaneously with Leptospira interrogans serovar Manilae strain UP-MMC-SM showed myositis of the thighs adjacent to the inoculated area beginning at 6 days post-infection. The myositis was non-purulent and showed sporadic degeneration and necrosis of muscle fibers. The degeneration of myofibers was accompanied by aggregations of macrophages. Immunofluorescence staining revealed leptospires surrounding the damaged muscle fibers. Subcutaneous injection of formalin-killed Leptospira or intraperitoneal injection of live Leptospira caused no myositis in hamster thighs. Liposomal clodronate treatment in infected hamsters reduced macrophage infiltration in muscle tissue without impacting bacterial clearance. Muscle necrosis was still observed in the infected hamsters treated with liposomal clodronate, and there was no significant change in serum creatine kinase levels compared to those in animals treated with liposomes alone. Our findings suggest that leptospiral invasion of muscle tissue from an inoculation site leads to the destruction of muscle fibers and causes non-purulent myositis, whereas the infiltrating macrophages contribute less to muscle destruction.

Successful treatment with streptomycin of genital leptospirosis in naturally infected cows under field conditions

The single-dose protocol of streptomycin treatment has been recommended to treat renal leptospirosis in bovines. However, treating genital infection remains a challenge. Recently, a protocol using three doses of streptomycin demonstrated effectiveness in the genital clearance of experimentally infected ewes. Therefore, the present study aimed to apply this three-dose protocol for genital infection treatment in naturally infected cows under field conditions. Thirty beef cows were diagnosed as positive by lipL32-PCR in their genital samples. Nucleotide sequences (n = 10) characterized them as Leptospira interrogans sg Sejroe, genetically related to Hardjoprajitno strains. After molecular diagnosis, 13 cows received a single dose of 25 mg/kg streptomycin. The other 17 cows were submitted to the three-dose protocol. The successful treatment rate of genital infection on the single streptomycin dose was 7/13 (53.8%), while the cows that received the three doses 16/17 were negative (94.1% of efficacy). Based on those results, we conclude that the standard treatment preconized for renal infection is not adequate for genital infection, and the three-dose protocol was successful in eliminating the carrier status of genital leptospirosis.

First report of human infection with Leptospira interrogans serovar Bratislava in the Eastern Black Sea region of Turkey

Leptospirosis is one of the most common zoonotic bacterial infections worldwide. It is an infection that usually affects people with low socioeconomic status, with morbidity and mortality risk. The clinical course of the disease may range from mild, featuring nonspecific clinical signs and symptoms, to severe, resulting in death. The respective studies conducted in Turkey indicate that leptospirosis seropositivity in animals and humans is higher in coastal and rural areas. Turkey's Eastern Black Sea Region has a humid climate with heavy rainfalls and a large population of mice and other rodents. However, a Leptospira interrogans serovar Bratislava case is yet to be reported in this region. This article reports the case of a 38-year-old patient who presented fever and acute renal failure and was diagnosed with Leptospira interrogans serovar Bratislava after hospitalization.

Protective role of stratum corneum in percutaneous Leptospira infection in a hamster model

Leptospira enters humans and animals through injured skin or mucous membranes by direct or indirect contact with urine excreted from infected reservoirs. Individuals with cut or scratched skin are at high risk of infection and are recommended to be protected from contact with Leptospira, but the risk of infection via skin without apparent wounds is unknown. We hypothesized that the stratum corneum of the epidermis might prevent percutaneous invasion of leptospires. We established a stratum corneum deficient model of hamsters using the tape stripping method. The mortality rate of hamsters lacking stratum corneum that were exposed to Leptospira was higher than that of controls with shaved skin, and was not significantly different from an epidermal wound group. These results indicated that the stratum corneum plays a critical role in protecting the host against leptospiral entry. We also examined the migration of leptospires through the monolayer of HaCaT cells (human keratinocyte cell line) using Transwell. The number of pathogenic leptospires penetrating the HaCaT cell monolayers was higher than that of non-pathogenic leptospires. Furthermore, scanning and transmission electron microscopic observations revealed that the bacteria penetrated the cell monolayers through both intracellular and intercellular routes. This suggested that pathogenic Leptospira can migrate easily through keratinocyte layers and is associated with virulence. Our study further highlights the importance of the stratum corneum as a critical barrier against the invasion of Leptospira found in contaminated soil and water. Hence, preventative measures against contact infection should be taken, even without visible skin wounds.

Neglected zoonotic bacteria causes and associated risk factors of cattle abortion in different agro-ecological zones of southwest Ethiopia

Three zoonotic bacteria, Coxiella burnetii, Leptospira spp, and Brucella spp, cause cattle abortion and significant losses in the livestock sector. However, these infections were neglected diseases in Ethiopia. Between October 2020 and October 2021, a cross-sectional study was carried out in southwest Ethiopia to determine the prevalence of abortion and identify the major zoonotic bacterial causes and risk factors that contribute to abortion. Using an indirect ELISA, antibodies to Brucella abortus, Leptospira Hardjo, and Coxiella burnetii were detected in serum samples taken from 461 cattle. Potential risk factors for cattle abortion were found using a multivariable random effect logistic regression analysis. The prevalence of cattle abortion was found to be 22.56 % (95 % CI: 18.74-26.38) in the study areas. Leptospira Hardjo (OR=1.8, 95% CI: 1.04-3.00), Coxiella burnetii (OR=2.7, 95 % CI: 1.26-5.62), and Brucella abortus (OR=9.8, 95 % CI: 1.27-17.15) were all associated with the occurrence of abortion in cattle, as were their co-infections (OR=8.1, 95 % CI: 1.28-39.33). Other risk factors for cattle abortion included breed (OR=16.7, 95 % CI: 2.20-26.77), herd size (OR=2.5, 95 % CI: 1.16-4.68), breeding method (OR=2.3, 95 % CI: 1.33-3.90), and contact with dogs (OR=2.2, 95 % CI: 1.34-3.53). According to the findings of this study, Brucella abortus, Coxiella burnetii, and Leptospira Hardjo are serious zoonoses that cause significant production loss in cattle due to abortion. To prevent transmission of these zoonotic diseases, it is crucial to implement effective control measures and increase public awareness. The causes of cattle abortion in the study areas should also be isolated and characterized.

A systematic review and meta-analysis of the epidemiology of Leptospirosis in HIV uninfected and in people living with HIV from the Southern African Development Community

BACKGROUND

Leptospirosis is an occupational, neglected febrile disease of bacterial origin transmitted between humans and animals. In this manuscript we summarize available data on Leptospira infection in HIV uninfected and in people living with HIV from the Southern African Development Community (SADC) countries, identifying gaps in knowledge and recommend future research priorities.

METHODOLOGY

Articles published between 1990 and 2021 were accessed by an online search of Google Scholar and Medline/PubMed performed between February 2020 and July 2022. The STATA program was used for the Meta-analysis. Pooled prevalence values with 95% confidence intervals and heterogeneity were determined.

RESULTS

Thirty studies from eight SADC countries, reporting the prevalence on Leptospira were reviewed. A pooled prevalence of 19% (CI: 13-25%), a heterogeneity level of 96% and index score ranging from 2 to 9 was determined. Only four (4) studies reported HIV co-infection status. Three species of Leptospira (Leptospira interrogans (4), L. kirschneri (3), Leptospira borgpetersenii (1) and 23 serogroups were identified. The most frequently reported serogroups were Icterohaemorrhagiae (13), Grippotyphosa and Australis (10) followed by Sejroe (8).

CONCLUSION

Studies on human leptospirosis in the SADC region are scarce, especially in people living with HIV. Additional studies aimed at determining the prevalence and the role of the pathogen in people living with HIV, including detailed clinical, molecular and demographic data are recommended.

Internalization of Leptospira interrogans via diverse endocytosis mechanisms in human macrophages and vascular endothelial cells

Leptospirosis, one of the leading global causes of morbidity and mortality, is an emerging public health problem, particularly in large urban centers of developing countries. Leptospirosis results from infection with an organism belonging to the Leptospira genus L. interrogans. The extensive invasive ability has previously been documented, however a mechanism that describes how the organism is internalized by human macrophages and transmigrates through human blood vessel remains poorly understood. In the present study, we utilized a human macrophage and vascular endothelial cell line to study the diverse invasive mechanisms by which L. interrogans infections occur. We found that THP-1 and HUVEC had a diverse expression of cell receptors and L. interrogans entered THP-1 and HUVEC by different pathways. In the macrophage model cell line, ITGB1/FAK-signaling mediated microfilament dependent endocytosis with lysosome fusion, whereas ITGB1/CAV-1/PI3K-signaling mediated microfilament dependent endocytosis and transcytosis without lysosome fusion in the endothelial cell model. Shedding of pathogenic leptospires from HUVEC displayed higher viability than those from THP-1. The monolayer of HUVEC maintained integrity during the infection, while 3D imaging showed that leptospires were transmigrated both intra- and intercellularly. These results indicate that endocytosis of leptospires in human macrophages and human vascular endothelial cells are quite different, macrophages are responsible for eliminating leptospires in the human body during the infection while vascular endothelial cells facilitate dissemination of leptospires from blood vessels into target organs where they cause injury.

Leptospirosis is a zoonotic bacterial disease which causes 1.03 million cases and 58,900 deaths each year. Human infections occur when the primary reservoir hosts, such as rodents, contaminate food and water with leptospires. Unlike other bacterial pathogens, leptospires invade the human body through mucosal barriers and enter the bloodstream, which can result in septicemia. Left untreated, leptospirosis can spread into multiple organs and tissues such as lungs, liver and kidneys. Pathological features of this disease include high fever, myalgia, lymphadenectasis, hemorrhaging and jaundice. Human macrophages and vascular endothelial cells play important roles in eliminating and preventing the transmission of this pathogen. We speculated that leptospires could be neutralized in macrophages and subsequently transported by vascular endothelial cells throughout the human body. In this research, the diverse mechanisms of human macrophages and vascular endothelial cells infected by leptospires were explored. Our findings can be used to improve the treatment, prevention, and supervision regarding leptospire transmission and infection.

Host and Species-Specificities of Pattern Recognition Receptors Upon Infection With Leptospira interrogans

Leptospirosis is a zoonotic infectious disease affecting all vertebrates. It is caused by species of the genus Leptospira, among which are the highly pathogenic L. interrogans. Different mammals can be either resistant or susceptible to the disease which can present a large variety of symptoms. Humans are mostly asymptomatic after infection but can have in some cases symptoms varying from a flu-like syndrome to more severe forms such as Weil’s disease, potentially leading to multiorgan failure and death. Similarly, cattle, pigs, and horses can suffer from acute forms of the disease, including morbidity, abortion, and uveitis. On the other hand, mice and rats are resistant to leptospirosis despite chronical colonization of the kidneys, excreting leptospires in urine and contributing to the transmission of the bacteria. To this date, the immune mechanisms that determine the severity of the infection and that confer susceptibility to leptospirosis remain enigmatic. To our interest, differential immune sensing of leptospires through the activation of or escape from pattern recognition receptors (PRRs) by microbe-associated molecular patterns (MAMPs) has recently been described. In this review, we will summarize these findings that suggest that in various hosts, leptospires differentially escape recognition by some Toll-like and NOD-like receptors, including TLR4, TLR5, and NOD1, although TLR2 and NLRP3 responses are conserved independently of the host. Overall, we hypothesize that these innate immune mechanisms could play a role in determining host susceptibility to leptospirosis and suggest a central, yet complex, role for TLR4.

Evaluation of the impact of chemical control on the ecology of Rattus norvegicus of an urban community in Salvador, Brazil

BACKGROUND

The presence of synanthropic rodents, such as Rattus norvegicus, in urban environments generates high costs of prophylaxis and control, in large part due to the environmental transmission of the pathogenic spirochete Leptospira interrogans, which causes leptospirosis. In Salvador, Brazil, The Center for Control of Zoonosis (CCZ) is responsible for planning and implementing Rodent Control Programs (RCP) which are based on chemical rodenticide. However, these strategies have not been standardized for use in developing countries.

AIM

This study aimed to identify the effect of a chemical control campaign on the demographic variables of urban R. norvegicus, analyzing relative abundance, sex structure, body mass, and age of the population, as well as the characterization of spatial distribution among households, rodent capture campaigns and interventions.

METHODS

This study was carried out during 2015 in three valleys of an urban poor community in Salvador. Individuals of R. norvegicus were systematically captured before (Pre-intervention) and three months (1st post-intervention) and six months (2nd post-intervention) after a chemical control intervention conducted by the CCZ in two valleys of the study area while the third valley was not included in the intervention campaign and was used as a non-intervention reference. We used analysis of variance to determine if intervention affected demographic variables and chi-square to compare proportions of infested households (Rodent infestation index-PII).

RESULTS

During the chemical intervention, 939 households were visited. In the pre-intervention campaign, an effort of 310 trap nights resulted in 43 rodents captured, and in the 1st and 2nd, post-intervention campaigns resulted in 47 rodents captured over 312 trap nights and 36 rodents captured over 324 traps-nights, respectively. The rodent infestation index (PII) points did not show a reduction between the period before the intervention and the two periods after the chemical intervention (70%, 72%, and 65%, respectively). Regarding relative abundances, there was no difference between valleys and period before and two periods after chemical intervention (trap success valley 1: 0,18; 0,19; 0,18 / Valley 3 0,15; 0,17; 0,13/ P>0,05). Other demographic results showed that there was no difference in demographic characteristics of the rodent population before and after the intervention, as well as there being no influence of the application of rodenticide on the areas of concentration of capture of rodents between the campaigns.

CONCLUSION

Our study indicates that the chemical control was not effective in controlling the population of R. norvegicus and provides evidence of the need for re-evaluation of rodent control practices in urban poor community settings.

Alive Pathogenic and Saprophytic Leptospires Enter and Exit Human and Mouse Macrophages With No Intracellular Replication

Leptospira interrogans are pathogenic bacteria responsible for leptospirosis, a zoonosis impacting 1 million people per year worldwide. Leptospires can infect all vertebrates, but not all hosts develop similar symptoms. Human and cattle may suffer from mild to acute illnesses and are therefore considered as sensitive to leptospirosis. In contrast, mice and rats remain asymptomatic upon infection, although they get chronically colonized in their kidneys. Upon infection, leptospires are stealth pathogens that partially escape the recognition by the host innate immune system. Although leptospires are mainly extracellular bacteria, it was suggested that they could also replicate within macrophages. However, contradictory data in the current literature led us to reevaluate these findings. Using a gentamicin–protection assay coupled to high-content (HC) microscopy, we observed that leptospires were internalized in vivo upon peritoneal infection of C57BL/6J mice. Additionally, three different serotypes of pathogenic L. interrogans and the saprophytic L. biflexa actively infected both human (PMA differentiated) THP1 and mouse RAW264.7 macrophage cell lines. Next, we assessed the intracellular fate of leptospires using bioluminescent strains, and we observed a drastic reduction in the leptospiral intracellular load between 3 h and 6 h post-infection, suggesting that leptospires do not replicate within these cells. Surprisingly, the classical macrophage microbicidal mechanisms (phagocytosis, autophagy, TLR–mediated ROS, and RNS production) were not responsible for the observed decrease. Finally, we demonstrated that the reduction in the intracellular load was associated with an increase of the bacteria in the supernatant, suggesting that leptospires exit both human and murine macrophages. Overall, our study reevaluated the intracellular fate of leptospires and favors an active entrance followed by a rapid exit, suggesting that leptospires do not have an intracellular lifestyle in macrophages.

Vaccination With Leptospira interrogans PF07598 Gene Family-Encoded Virulence Modifying Proteins Protects Mice From Severe Leptospirosis and Reduces Bacterial Load in the Liver and Kidney

The molecular and cellular pathogenesis of leptospirosis remains poorly understood. Based on comparative bacterial genomics data, we recently identified the hypothetical PF07598 gene family as encoding secreted exotoxins (VM proteins) that mediate cytotoxicity in vitro. To address whether VM proteins mediate in vivo leptospirosis pathogenesis, we tested the hypothesis that VM protein immunization of mice would protect against lethal challenge infection and reduce bacterial load in key target organs. C3H/HeJ mice were immunized with recombinant E. coli-produced, endotoxin-free, leptospiral VM proteins (derived from L. interrogans serovar Lai) in combination with the human-compatible adjuvant, glucopyranoside lipid A/squalene oil-in-water. Mice receiving full length recombinant VM proteins were protected from lethal challenge infection by L. interrogans serovar Canicola and had a 3-4 log₁₀ reduction in bacterial load in the liver and kidney. These experiments show that immunization with recombinant VM proteins prevents leptospirosis clinical pathogenesis and leads to markedly reduced key target organ infection in this animal model. These data support the role of leptospiral VM proteins as virulence factors and suggest the possibility that a VM protein-based, serovar-independent, pan-leptospirosis vaccine may be feasible.

Pulmonary haemorrhage as the earliest sign of severe leptospirosis in hamster model challenged with Leptospira interrogans strain HP358

Background

Severe leptospirosis is challenging as it could evolve rapidly and potentially fatal if appropriate management is not performed. An understanding of the progression and pathophysiology of Leptospira infection is important to determine the early changes that could be potentially used to predict the severe occurrence of leptospirosis. This study aimed to understand the kinetics pathogenesis of Leptospira interrogans strain HP358 in the hamster model and identify the early parameters that could be used as biomarkers to predict severe leptospirosis.

Methodology/Principal findings

Male Syrian hamsters were infected with Leptospira interrogans strain HP358 and euthanized after 24 hours, 3, 4, 5, 6 and 7 days post-infection. Blood, lungs, liver and kidneys were collected for leptospiral detection, haematology, serum biochemistry and differential expression of pro- and anti-inflammatory markers. Macroscopic and microscopic organ damages were investigated. Leptospira interrogans strain HP358 was highly pathogenic and killed hamsters within 6–7 days post-infection. Pulmonary haemorrhage and blood vessel congestion in organs were noticed as the earliest pathological changes. The damages in organs and changes in biochemistry value were preceded by changes in haematology and immune gene expression.

Conclusion/Significance

This study deciphered haemorrhage as the earliest manifestation of severe leptospirosis and high levels of IL-1β, CXCL10/IP-10, CCL3/MIP-α, neutrophils and low levels of lymphocytes and platelets serve as a cumulative panel of biomarkers in severe leptospirosis.

As the severe form of leptospirosis could progress rapidly and be potentially fatal if not treated earlier, deciphering the pathophysiology kinetics of infection is crucial to determine the parameters of disease severity. To understand this, we challenged hamsters with the highly virulent Leptospira interrogans strain HP358. Pulmonary haemorrhage was observed as the earliest pathological change followed by liver and kidneys damages. The increased expression of IL-1β, CXCL10/IP-10, CCL3/MIP-α, high neutrophils and low lymphocytes and platelets production observed in the present study indicate that these parameters could serve as a cumulative panel of biomarkers in severe leptospirosis.

Dissemination of Leptospira into the intestinal tract resulting in fecal excretion in a hamster model of subcutaneous infection with Leptospirainterrogans

Leptospirosis, caused by pathogenic Leptospira, is one of the most common zoonotic diseases in the world. It is transmitted to humans through the skin and mucous membranes by contact with water or soil contaminated with urine excreted from infected animals. In human infections, gastrointestinal symptoms such as abdominal pain, vomiting, and diarrhea have been frequently observed, but there have been no reports analyzing gastrointestinal lesions in leptospirosis, and the pathological mechanism of gastrointestinal symptoms in leptospirosis remains unclear. In this study, we investigated the pathological changes and the distribution of leptospires in the intestinal wall, and the presence of leptospires in the intestinal contents and feces, of hamsters subcutaneously infected with Leptospira interrogans. Results showed that infected hamsters had macroscopic redness in the jejunum and ileum. Submucosal hemorrhage was observed histologically, and there was no infiltration of inflammatory cells such as neutrophils. There were no obvious changes in the colon, either macroscopically or histologically, and the feces were normal (solid stools). Leptospira was isolated from all the intestinal walls from the small intestine to the colon, the intestinal contents, and the feces. These findings suggest that the invasion of leptospires into the intestinal wall and the associated submucosal hemorrhage may be the cause of the gastrointestinal symptoms observed in leptospirosis. Furthermore, not only the urine of infected animals but also the feces could be a source of infection.

Detection of Leptospira interrogans in Wild Sambar Deer (Rusa unicolor), Brazil

Leptospirosis is an emerging zoonotic disease caused by bacteria of the genus Leptospira. Wild animals may present acute disease or become chronic hosts. The present study aimed to identify Leptospira spp. infection and determine circulating serogroups in free-ranging sambar deer (Rusa unicolor) in a fragment of peri-urban tropical forest in northeastern Brazil. Blood samples were collected and subjected to microscopic agglutination testing (MAT) and PCR analysis (genes lipL32 and secY). Anti-Leptospira antibodies were detected in 60% of the animals tested, with serogroups Cynopteri (33.4%), Hebdomadis (22.2%) and Grippotyphosa (22.2%) identified as most prevalent. DNA corresponding to the pathogenic species Leptospira interrogans was detected in 2/15 (13.3%) of the samples tested. Sambar deer experience a high level of exposure to Leptospira spp. in our epidemiological setting. It is important to emphasize the implementation of effective measures (i.e., maintaining habitats and reducing human contact) for the conservation of endangered species.

The leptospiral LipL21 and LipL41 proteins exhibit a broad spectrum of interactions with host cell components

Leptospirosis is a globally prevalent zoonotic disease, and is caused by pathogenic spirochetes from the genus Leptospira. LipL21 and LipL41 are lipoproteins expressed strongly on the outer membrane of pathogenic Leptospira spp. Many studies have shown that both proteins are interesting targets for vaccines and diagnosis. However, their role in host-pathogen interactions remains underexplored. Therefore, we evaluated the capacity of LipL21 and LipL41 to bind with glycosaminoglycans (GAGs), the cell receptors and extracellular matrix, and plasma components by ELISA. Both proteins interacted with collagen IV, laminin, E-cadherin, and elastin dose-dependently. A broad-spectrum binding to plasma components was also observed. Only LipL21 interacted with all the GAG components tested, whereas LipL41 presented a concentration-dependent binding only for chondroitin 4 sulfate. Although, both proteins have the ability to interact with fibrinogen, only LipL21 inhibited fibrin clot formation partially. Both proteins exhibited a decrease in plasminogen binding in the presence of amino caproic acid (ACA), a competitive inhibitor of lysine residues, suggesting that their binding occurs via the kringle domains of plasminogen. LipL41, but not LipL21, was able to convert plasminogen to plasmin, and recruit plasminogen from normal human serum, suggesting that the interaction of this protein with plasminogen may occur in physiological conditions. This work provides the first report demonstrating the capacity of LipL21 and LipL41 to interact with a broad range of host components, highlighting their importance in host-Leptospira interactions.

Linking longitudinal and cross-sectional biomarker data to understand host-pathogen dynamics: Leptospira in California sea lions (Zalophus californianus) as a case study

Confronted with the challenge of understanding population-level processes, disease ecologists and epidemiologists often simplify quantitative data into distinct physiological states (e.g. susceptible, exposed, infected, recovered). However, data defining these states often fall along a spectrum rather than into clear categories. Hence, the host-pathogen relationship is more accurately defined using quantitative data, often integrating multiple diagnostic measures, just as clinicians do to assess their patients. We use quantitative data on a major neglected tropical disease (Leptospira interrogans) in California sea lions (Zalophus californianus) to improve individual-level and population-level understanding of this Leptospira reservoir system. We create a "host-pathogen space" by mapping multiple biomarkers of infection (e.g. serum antibodies, pathogen DNA) and disease state (e.g. serum chemistry values) from 13 longitudinally sampled, severely ill individuals to characterize changes in these values through time. Data from these individuals describe a clear, unidirectional trajectory of disease and recovery within this host-pathogen space. Remarkably, this trajectory also captures the broad patterns in larger cross-sectional datasets of 1456 wild sea lions in all states of health but sampled only once. Our framework enables us to determine an individual's location in their time-course since initial infection, and to visualize the full range of clinical states and antibody responses induced by pathogen exposure. We identify predictive relationships between biomarkers and outcomes such as survival and pathogen shedding, and use these to impute values for missing data, thus increasing the size of the useable dataset. Mapping the host-pathogen space using quantitative biomarker data enables more nuanced understanding of an individual's time course of infection, duration of immunity, and probability of being infectious. Such maps also make efficient use of limited data for rare or poorly understood diseases, by providing a means to rapidly assess the range and extent of potential clinical and immunological profiles. These approaches yield benefits for clinicians needing to triage patients, prevent transmission, and assess immunity, and for disease ecologists or epidemiologists working to develop appropriate risk management strategies to reduce transmission risk on a population scale (e.g. model parameterization using more accurate estimates of duration of immunity and infectiousness) and to assess health impacts on a population scale.

Efficacy of the Rabbit Polyclonal Anti-leptospira Antibody against Homotype or Heterotype Leptospira Infection in Hamster

Leptospirosis, caused by Leptospira, is one of the most important of neglected emerging zoonotic diseases that has important impacts on public health worldwide. Polyclonal antibody (pcAb) therapy is a potential method to process a series of pathogens for which there are limited determination of treatment, such as leptospirosis. First, we evaluated the efficacy of pcAb, derived from the sera of rabbits inoculated with Leptospira, against homotype (Leptospira interrogans serovar Lai) or heterotype (Leptospira interrogans serovar Autumnalis) Leptospira infection in a lethal hamster model. The pcAb treatment improved survival compared to the controls. The histopathology's of the infected kidney, liver and lung were also examined by hematoxylin and eosin staining. Using real-time quantitative PCR, we determined that most of the leptospires in the primary organs were almost completely removed by pcAb. In the second experiment, treatments, including antibiotic, pcAb, and combination, were started immediately after occurrence of the first serious sickness mouse in any group. No significant difference in survival rate between pcAb group and antibiotic group was found, but the combination therapy group significantly improved survival rate compared to the others (P<0.05). We conclude that the rabbit pcAb treatment may cure both the homotype and the heterotype lethal Leptospira infections in hamster, and combination therapy improved survival compared to antibiotic group in the late treatment of homotype leptospirosis.

[The cytotoxic effect and the effect of permeability with OmpA like protein Loa22 from Leptospira interrogans serovar]

OBJECTIVE

To study the toxic effect and the change of permeability on human umbilical vein endothelia (HUVE) of the Loa22 protein from virulent serovar Lai. Leptaspira interrogans by expressing its protein.

METHODS

In this study, the pGEX-Loa22 peptide prokaryotic recombinant plasmid of Leptospira interrogans serovar Lai preserved in our laboratory was used to express Loa22 fusion protein with GST lable. Then the target fusion protein was obtained by using affinity chromatography with the GST-Trap FF Column. The purified Loa22 fusion protein was detected by SDS-PAGE and confirmed by Western blot assay using the mouse anti-GST tag monoclonal anti-body. pGEX-Loa22 protein was administered to culture with human umbilical vein endothelial cells (HUVEC) to elucidate the cytotoxic role and the change of permeability of leptospiral outer membrane proteins.

RESULTS

The recombiant plasmid with Loa22 mature peptide was expressed successfully and the protein was purfied. Significant higher level of apoptosis ratio, lower CCK-8 aborntion, and increasing permeability on HUVEC were observed after treated the HUVEC with the expressed fusion protein.

CONCLUSION

The purified Loa22 fusion protein have obvious toxic effects on vascular endothelial cells, and also it can increase permeability of HUVEC.

Characterization of recombinant flagellin B protein from Leptospira interrogans

Symptoms of the early phase leptospirosis often are non-specific and can be a major problem in making a diagnosis of febrile illnesses. Rapid diagnosis of leptospirosis is of extreme importance, because antibiotic treatment provides greatest benefit when administered in early stage of the disease. Recombinant flagellin B (FlaB) gene (flaB) of Leptospira interrogans serovar Autumnalis strain Akiyami A was heterologously expressed and purified. The 35 kDa recombinant FlaB was 99% similar to the reference strain in GenBank. Rabbit polyclonal antirecombinant FlaB antibodies recognized using immunoblotting yeilded 35-36 kDa doublet from one saprophytic and eight pathogenic Leptospira serovars. Western blot assay showed that recombinant FlaB could distinguish leptospirosis from non-leptospirosis sera. This recombinant FlaB can be used in serodiagnosis of leptospirosis and identification of Leptospira spp.

Pulmonary disease in hamsters infected with Leptospira interrogans: histopathologic findings and cytokine mRNA expressions

Our aim was to evaluate the pulmonary changes induced by Leptospira interrogans infection in hamsters, and the gene expression of endogenous mediators in lung fragments during 28 days of observation. The animals were euthanized on days 4, 7, 14, 21, and 28 post-inoculation. Histopathologic lung analysis showed hemorrhage, pneumonia, alveolar congestion, and infiltrated cellular areas, with increasing severity until day 21 post-inoculation. Tumor necrosis factor (TNF)-alpha mRNA expression enhanced in first days with peak on day 4 and slightly decreased in the final phase. The interleukin (IL)-10 remained relatively constant throughout the period, with the exceptions of days 4 and 14. The endothelial nitric-oxide synthesis (eNOS) showed an increased expression on day 4, followed by an augment on days 7 and 14, and remaining constant up to day 28 post-infection. Our results demonstrate that inoculation of L. interrogans sorovar Icterohaemorrhagiae induced pulmonary lesions, including pulmonary hemorrhage, supporting that the lung is a target organ.

[Optimization of prokaryotic expression conditions of Leptospira interrogans trigeminy genus-specific protein antigen based on surface response analysis]

Lipoproteins LipL32 and LipL21 and transmembrane protein OMPL1 have been confirmed as the superficial genus-specific antigens of Leptospira interrogans, which can be used as antigens for developing a universal genetic engineering vaccine.

OBJECTIVE

In order to obtain high expression of an artificial fusion gene lipL32/1-lipL21-ompL1/2, we optimized prokaryotic expression conditions.

METHODS

We used surface response analysis based on the central composite design to optimize culture conditions of a new antigen protein by recombinant Escherichia coli DE3.The culture conditions included initial pH, induction start time, post-induction time, Isopropyl beta-D-thiogalactopyranoside (IPTG) concentration, and temperature.

RESULTS

The maximal production of antigen protein was 37.78 mg/l. The optimal culture conditions for high recombinant fusion protein was determined: initial pH 7.9, induction start time 2.5 h, a post-induction time of 5.38 h, 0.20 mM IPTG, and a post-induction temperature of 31 degrees C.

CONCLUSION

Surface response analysis based on CCD increased the target production. This statistical method reduced the number of experiments required for optimization and enabled rapid identification and integration of the key culture condition parameters for optimizing recombinant protein expression.

Binding of Leptospira to extracellular matrix proteins

BACKGROUND

Leptospirosis is a zoonotic disease of global importance. Pathogenesis caused by this infectious disease remains unclear. Attachment of pathogenic leptospires to host tissues is a crucial initial step to establish the infection.

OBJECTIVE

Study the binding of the spirochete to three types of extracellular matrix (ECM), collagen type IV, fibronectin, and laminin, which are major components of target organs.

MATERIAL AND METHOD

ELISA-based experiments were performed to determine binding of pathogenic (serovar icterohaemorrhagie) and non-pathogenic (serovar Patoc) serovars, to purified ECM.

RESULTS

Both pathogenic and non-pathogenic serovars bound to all three types of ECM in the dose-dependent manner and the binding to fibronectin is higher than to collagen and laminin (p < 0.005).

CONCLUSION

Pathogenic leptospires can bind to various types of ECM and the binding of leptospires to fibronectin was higher than to collagen and laminin. However, this capability may not be the only mechanism that makes leptospires virulent since non-pathogenic leptospire can bind the ECM as well.

A histopathological study of hearts and spleens of hamsters (Mesocricetus auratus) infected with Leptospira interrogans, serovar pyrogenes

The effects of Leptospira interrogans on the heart and spleen of hamsters were studied histopathologically. Infected hamsters were sacrificed at 1 hour, 6 hours and on days 1, 2, 3, 4, 5 and 6 after inoculation with Leptospira interrogans serovar pyrogenes. The heart and spleen of each of the sacrificed animals were removed and processed for routine conventional light microscopy. Infected hearts showed degenerative change of the cardiac muscle cells composed of cellular swelling, condensation of chromatin granules, pyknotic nuclei and acidophilic cytoplasm. Congestion of the cardiac blood vessels and hemorrhagic areas were found. Necrosis of the cardiac muscle cells was surrounded by numerous inflammatory cells. In the spleen, cellular necrosis was found scattered throughout the splenic cord. The splenic sinusoids were dilated and congested with many hemorrhagic areas. Inflammatory cell infiltration was also noted in the splenic parenchyma and the splenic sinusoids.

Prognostic factors associated with severe leptospirosis

Leptospirosis is an anthropozoonosis caused by Leptospira interrogans. It occurs worldwide and is endemic in French Polynesia. Leptospirosis is associated with a large variety of clinical symptoms. Most infections caused by leptospires are either sub-clinical or of very mild severity, but 5-10% of infections result in multiple organ damage, including kidney, liver and lung lesions. Among 71 patients hospitalised in Papeete for severe leptospirosis during a period of 2 years, the main risk-factors for a severe outcome were hypotension, oliguria and an abnormal chest auscultation at the first physical examination. Survival depends on rapid diagnosis and early appropriate management. Well-defined criteria may help physicians to improve the timely treatment of high-risk patients.

Thrombocytopenia in the experimental leptospirosis of guinea pig is not related to disseminated intravascular coagulation

Background

Thrombocytopenia is commonly observed in severe leptospirosis. However, previous studies on coagulation alterations during leptospirosis resulted in inconsistent conclusions. Some findings showed that the prominent levels of thrombocytopenia observed in severe leptospirosis did not reflect the occurrence of disseminated intravascular coagulation (DIC) syndrome, while the others reached the conclusion that the hemorrhages observed in leptospirosis were due to DIC. The aim of this study is to elucidate whether DIC is an important feature of leptospirosis.

Methods

The leptospirosis model of guinea pig was established by intraperitoneal inoculation of Leptospira interrogans strain Lai. Hematoxylin and eosin (HE) staining, electron microscopy and immunohistochemistry staining were used to detect the pathologic changes. Platelet thrombus or fibrin thrombus was detected by HE, Martius Scarlet Blue (MSB) staining and electron microscopy. Hemostatic molecular markers such as 11-dehydrogenate thromboxane B2 (11-DH-TXB2), thrombomodulin (TM), thrombin-antithrombin III complex (TAT), D-Dimer and fibrin (ogen) degradation products (FDPs) in the plasma were examined by quantitative enzyme-linked immunosorbent assay (ELISA) to evaluate the hematological coagulative alterations in leptospirosis models.

Results

Pulmonary hemorrhage appeared in the model guinea pig 24 hours after leptospires intraperitoneal inoculation, progressing to a peak at 96 hours after the infection. Leptospires were detected 24 hours post-inoculation in the liver, 48 hours in the lung and 72 hours in the kidney by immunohistochemistry staining. Spiral form of the bacteria was initially observed in the liver, lung and kidney suggestive of intact leptospires, granular form of leptospires was seen as the severity increased. Platelet aggregation in hepatic sinusoid as well as phagocytosis of erythrocytes and platelets by Kupffer cells were both observed. Neither platelet thrombus nor fibrin thrombus was found in the liver, lung or kidney via morphological observation. Thrombocytopenia was observed in all infected guinea pigs of our experimental leptospirosis study. Analysis of hematologic molecular markers showed that 11-DH-TXB2 and TM in the plasma were elevated significantly. TAT that reflects the thrombin activation had a trend of decline after infection. Although D-dimer and FDPs increased statistically, the increasing may not bear clinical significance.

Conclusion

Pathologic and hematological studies for experimental leptospirosis of guinea pig indicated that the thrombocytopenia found in guinea pigs did not correlate with the occurrence of DIC. The platelet aggregation and Kupffer cells phagocytosis might be the potential causes of thrombocytopenia in severe leptospirosis.

[Leptospirosis laboratory of WSSE in Wrocław (1947-2005). Comment on its activity]

The article summarises the 1947-2005 activity of the Leptospire Laboratory of Voivodeship Sanitary-Epidemiological Station in Wrocław (1947-2005) which is the oldest and, presently, the only health care diagnostic laboratory offering leptospirosis testing in Poland. Based on own experience the authors analysed laboratory diagnosis of leptospirosis in Poland, identifying existing problems.

Changes in lipopolysaccharide O antigen distinguish acute versus chronic Leptospira interrogans infections

Leptospirosis is the most geographically widespread zoonotic disease in the world. A severe pulmonary form of leptospirosis (SPFL) is being recognized with increased frequency. We have reported that human SPFL isolates of Leptospira cause acute lethal infection with prominent pulmonary hemorrhage in guinea pigs. We have found that the same SPFL strains cause asymptomatic infection and chronic renal shedding in rats, where infection is restricted to the renal tubules. To address the antigenic composition of host tissue-derived Leptospira (HTL), motile leptospires were purified from guinea pig liver by centrifugation on Percoll density gradients and compared to Percoll-purified in vitro-cultivated Leptospira (IVCL). The lipopolysaccharide O antigen (Oag) content of guinea pig liver-derived HTL was markedly reduced compared to that of IVCL, as demonstrated both by immunoblotting with a monoclonal antibody that was serovar specific for Oag and by periodate-silver staining. Confocal microscopy of HTL in guinea pig liver and kidney with the Oag-specific monoclonal antibody provided further evidence that diminution of the Oag content occurred in situ during lethal infection. In contrast, the Oag content of HTL in chronically infected rat renal tubules was indistinguishable from that of IVCL. These findings suggest that there may be regulation of Oag synthesis by Leptospira specific to the animal host infected. The hypothesis that the Oag content is related to whether lethal infection or chronic renal tubular colonization occurs remains to be tested.

Fatal septicemic melioidosis in a young military person possibly co-infected with Leptospira interrogans and Orientia tsutsugamushi

Concurrent melioidosis, leptospirosis, and scrub typhus after rural activities is rarely reported. A 19-year-old previously healthy man had fever onset after 2 weeks of military training. Pneumonia became evident on the fifth day of fever under intravenous penicillin and oral minocycline therapy. Acute respiratory failure developed the next day with shock and acute renal and liver function deterioration, which resulted in death. Blood cultures on the third and fifth days grew Burkholderia pseudomallei. Serology revealed leptospirosis and scrub typhus. The emergence of melioidosis in Taiwan and this death without antibiotic treatment for melioidosis alert us that B. pseudomallei should be included as a possible pathogen of pneumonia and sepsis, especially after rural activities.

Human and canine leptospirosis: serological data of São Paulo City, Brazil, 2000 to 2003

Sera from humans and dogs were tested by microscopic agglutination test. Icterohaemorrhagiae was the predominant serogroup in both groups, associated with the infestation of Rattus norvegicus.

Lipopolysaccharides of Bacteroides fragilis, Chlamydia trachomatis and Pseudomonas aeruginosa signal via toll-like receptor 2

Recognition of bacterial lipopolysaccharide (LPS) is critical in the host defence against Gram-negative infection. While enterobacterial LPS signals via Toll-like receptor 4 (TLR4), it has recently been reported that the LPS of Leptospira interrogans, Legionella pneumophila, Rhizobium species Sin-1 and at least one strain of Porphyromonas gingivalis are capable of signalling via TLR2. Using a TLR transfection assay and measurement of an NF-kappaB-sensitive promoter region, the results show that the LPS of Bacteroides fragilis NCTC-9343, Chlamydia trachomatis LGV-1 and Pseudomonas aeruginosa PAC-611 also signal via TLR2 and it is pointed out that all TLR2-signalling LPS discovered to date demonstrate relatively weak endotoxicity in some models and structural features distinct from those LPS shown to signal via TLR4.

Leptospirosis presenting as acute pancreatitis and cholecystitis

We report a rare case of a 21-year-old man with leptospirosis mimicking acute pancreatitis and cholecystitis. This case report aims at pointing out the need of taking into consideration the possibility of leptospirosis in patients with an influenza-like syndrome, headache accompanied by acute abdominal pain and a suspicious exposure in order to prevent unnecessary surgical interventions.

Markedly prolonged jaundice from simultaneous infection with hepatitis E virus and leptospira

We treated a patient simultaneously infected with hepatitis E virus and Leptospira interrogans, both acquired in China. Severe hyperbilirubinemia required nearly 200 days to resolve, transminase elevation showed a fluctuating course, and liver biopsy specimens showed fibrosis unusual for hepatitis E. Leptospirosis appeared to have altered the course of hepatitis E virus infection in this patient, even though infection with Leptospira was cleared with antibiotics by 50 days after the onset of the hepatitis symptoms.

[Weil's disease: a case report of acquired leptospirosis in Switzerland]

Leptospirosis is a rare disease in Switzerland. However its incidence is probably underestimated, due to its broad spectrum of presentations, including subclinical benign forms and the ictero-hemorragic form of the Weil's syndrome, whose mortality is high. We describe here a case of Weil's syndrome acquired in Switzerland with a favourable outcome under antibiotherapy. Even in the absence of any travel, the association of an acute renal insufficiency and jaundice with only moderate hepatic cytolysis should lead to the suspicion of leptospirosis. Clinical and epidemiological aspects of the disease are discussed in the article.

[Fever of unknown origin, head and muscle pain, hemoptysis, hepatosplenomegaly and icterus. 2 case reports]

Die Leptospirose kommt in der Schweiz aufgrund der klimatischen Verhältnisse selten vor, trotzdem wird die Inzidenz dieser Krankheit unterschätzt. Das klinische Bild ist vielfältig. Die Differentialdiagnose reicht von einer grippeähnlichen Erkrankung bis hin zur akut verlaufenden Systemerkrankung. Diese Tatsache erfordert aufgrund der therapeutischen Konsequenz, die Durchführung einer intensiven und häufig auch invasiven Diagnostik, welche letztlich oft unergiebig bleibt. Neue und vor allem schnellere diagnostische Möglichkeiten mittels PCR aus Blut, Liquor und Urin werden diskutiert, sind aber noch nicht etabliert. Eine antibiotische Therapie wird je nach Verlaufsform kontrovers beurteilt.

The changing epidemiology of leptospirosis in Israel

We reviewed all serologically confirmed cases of leptospirosis from 1985 to 1999 in Israel, where the disease is endemic. There were 59 cases, with an average annual incidence of 0.05/100,000. The dominant serogroup, Leptospira icterohemorrhagica, occurred in 29% of patients; in an earlier study (1970-1979), it accounted for only 2%. Serogroups that occurred mainly in rural areas accounted previously for 79% but had declined to 32%.

Epidemiologic features of equine Leptospira interrogans of human significance

Leptospirosis is a zoonotic bacterial disease caused by Leptospira interrogans. There is a serologic evidence that horses are exposed to L. interrogans and, as a shedder of these organisms, can be a threat to humans. We examined risk factors associated with the risk of testing seropositive to three L. interrogans serovars (L. icterohaemorrhagiae, L. grippotyphosa, and L. canicola) in the horses of New York State, in order to understand the epidemiology of the disease and suggest strategies to control and prevent equine leptospirosis. To carry out this study, blood samples were collected from a random sample of 2551 horses and tested for the presence of antibodies to the above serovars using the microscopic agglutination test. Samples with a titer $100 were considered positive. Clinical and demographic data were collected on each horse, the farms' management practices and ecology. Logistic regression analysis was used to develop a multivariate indexing system and to identify factors significantly associated with the risk of leptospirosis. Four indices were developed based on the possible sources of exposure: rodent exposure index; wildlife exposure index; soil and water index; and management index. The soil and water index was significantly associated with the risk of exposure to all three serovars. Management was positively associated with L. icterohaemorrhagiae and L. canicola. Density of horses turned out together was positively associated with the risk of exposure to L. grippotyphosa. We concluded that indirect exposure of horses to L. interrogans through contaminated soil and water appears to be significantly associated with the risk of exposure to all three serovars. Management appears to play an important role in the exposure to L. interrogans. Modification of management practices might reduce the horses' risk of exposure and hopefully minimize the human hazards.

Morphological characterization of lung and kidney lesions in C3H/HeJ mice infected with Leptospira interrogans serovar icterohaemorrhagiae: defect of CD4+ and CD8+ T-cells are prognosticators of the disease progression

Neonates and young C3H/HeJ mice were highly susceptible to lethal infection with Leptospira interrogans serovar icterohaemorrhagiae. The main pathological changes were seen by light microscopy in the lung and kidneys of 3-week-old mice at 11 days after inoculation. Lung histological lesions included small and medium-sized vasculitis with fibrinoid changes, hemorrhages, moderate infiltrate of mononuclear inflammatory cells and fibrin thrombi. In the kidney there was mild to severe acute tubular necrosis associated with interstitial nephritis. Repair of damaged tubules in surviving mice was observed within 17 days after inoculation. Pathological findings of CD4+ and CD8+ cell-depleted mice were clearly more severe than that seen in untreated animals by 17 days after inoculation. Comparatively, CD4+/CD8+ cell-depleted mice had more marked lung and kidney lesions than in the CD8+ or CD4+ cell-depleted mice. A very high level of tubular alterations was seen in the kidneys of all treated groups. Increased degrees of interstitial nephritis also reflected the T-cell subsets depletion related events. Leptospires were clearly demonstrated by immunoperoxidase close to the sites of histological damage in all infected mice. C3H/HeJ mice represent a useful model for further studies in pathogenicity of leptospires and natural resistance of the host.

Na,K-ATPase: a molecular target for Leptospira interrogans endotoxin

On the basis of our report that a glycolipoprotein fraction (GLP) extracted from Leptospira interrogans contains a potent inhibitor of renal Na,K-ATPase, we proposed that GLP-induced inhibition of Na,K-ATPase might be the primary cellular defect in the physiopathology of leptospirosis. The present study was designed to test this hypothesis by determining whether or not 1). GLP inhibits all the isoforms of Na,K-ATPase which are expressed in the tissues affected by leptospirosis, 2) Na,K-ATPase from leptospirosis-resistant species, such as the rat, is sensitive to GLP, 3) GLP inhibits Na,K-ATPase from intact cells, and 4) GLP inhibits ouabain-sensitive H,K-ATPase. The results indicate that in the rabbit, a leptospirosis-sensitive species, GLP inhibits with similar efficiency (apparent IC50: 120-220 micrograms protein GLP/ml) all isoforms of Na,K-ATPase known to be expressed in target tissues for the disease. Na,K-ATPase from rat kidney displays a sensitivity to GLP similar to that of the rabbit kidney enzyme (apparent IC50: 25-80 and 50-150 micrograms protein GLP/ml for rat and rabbit, respectively), indicating that resistance to the disease does not result from the resistance of Na,K-ATPase to GLP. GLP also reduces ouabain-sensitive rubidium uptake in rat thick ascending limbs (pmol mm-1 min-1 +/- SEM; control: 23.8 +/- 1.8; GLP, 88 micrograms protein/ml: 8.2 +/- 0.9), demonstrating that it is active in intact cells. Finally, GLP had no demonstrable effect on renal H,K-ATPase activity, even on the ouabain-sensitive form, indicating that the active principle of GLP is more specific for Na,K-ATPase than ouabain itself. Although the hypothesis remains to be demonstrated in vivo, the present findings are compatible with the putative role of GLP-induced inhibition of Na,K-ATPase as an initial mechanism in the physiopathology of leptospirosis.

Inhibition of Na,K-ATPase by an endotoxin extracted from Leptospira interrogans: a possible mechanism for the physiopathology of leptospirosis

Clinical manifestations of leptospirosis include disorders of the electrolytical balance which might be related to inhibition of Na,K-ATPase. Although the physiopathological cellular mechanism of leptospirosis remains unknown, a bacterial endotoxin has been incriminated. Therefore, we evaluated whether a glycolipoprotein fraction extracted from Leptospira interrogans and known to be cytotoxic might inhibit Na,K-ATPase. This glycolipoprotein fraction (GLP) inhibited Na,K-ATPase activity in rabbit kidney epithelial cells as well as Na,K-ATPase purified from rabbit kidney medulla. Inhibition was dose-dependent, and at maximum it almost abolished Na,K-ATPase activity whereas it had no effect on other enzymes. The GLP did not change the apparent affinity of Na,K-ATPase for potassium whereas it increased that for sodium, revealing a mechanism of inhibition different from that of ouabain. Finally, the inhibitory principle present in the GLP preparation was thermostable and was curtailed by the presence of albumin. In conclusion, a glycolipoproteic fraction extracted from Leptospira interrogans contains a specific inhibitor of Na,K-ATPase. This glycolipoproteic fraction which is present in diseased tissues might induce, through this inhibitor, cellular dysfunctions responsible for the symptoms, in particular those associated with electrolytical disorders such as disturbances of renal electrolyte handling, cardiac arrhythmia or diarrhoea.

A review of laboratory techniques and their use in the diagnosis of Leptospira interrogans serovar hardjo infection in cattle

This paper reviews the laboratory diagnosis of Leptospira hardjo infection in cattle. Two genotypes of L hardjo, Hardjoprajitno and Hardjobovis, have been identified in cattle, but only Hardjobovis has been isolated in Australia. There are problems with diagnosis and control of bovine leptospirosis. Infection is usually subclinical and the serological titres vary greatly in peak and duration. Leptospires may be excreted in urine for up to 18 months. Low microscopic agglutination test titres may be significant in unvaccinated herds as indicators of endemic infection. Vaccines differ in their composition, and their efficacy is difficult to evaluate. The serological response after vaccination is difficult to differentiate from the response after infection. Pregnant cows that become infected may abort, but this is usually after the serological response has peaked. Therefore, paired serum samples are of little use in diagnosing abortion caused by L hardjo. Fluorescent antibody techniques are more sensitive than dark field microscopy for detection of leptospires in urine and tissue samples. Techniques for culture have improved but are still difficult to perform and take 3 months or longer for results to be known. DNA probes and polymerase chain reaction tests are very sensitive and specific, quick to perform, and can be used on fluid and tissue samples.

Leptospirosis complicated by a Jarisch-Herxheimer reaction and adult respiratory distress syndrome: case report

Leptospirosis, severe infection due to Leptospira interrogans, is a potentially lethal disease that causes multiple organ failure. In addition to hepatic, renal, and CNS involvement, which are classic complications of leptospirosis, the disease may also be complicated by adult respiratory distress syndrome. Treatment with penicillin may precipitate a severe Jarisch-Herxheimer reaction. The mechanisms of Leptospira-induced toxicity remain obscure. We report a near-fatal case of leptospirosis in a patient who developed a JHR and respiratory failure immediately after initiation of therapy.

Decreased erythrocyte osmotic fragility during canine leptospirosis

Erythrocyte osmotic fragility (EOF) was carried out in nineteen dogs naturally infected by Leptospira interrogans serovar icterohaemorrhagiae/copenhagi. A decreased EOF was observed, suggesting a modification of erythrocyte components secondary to disturbances that occur during canine leptospirosis, such as renal damage and hepatic disease.

Leptospirosis presenting as atypical pneumonia, respiratory failure and pyogenic meningitis

A 20-year-old man who looked after a pack of hounds was admitted with a short history of headache, fever, haemoptysis and muscle cramps. Investigations showed type I respiratory failure with diffuse pneumonitis, pyogenic meningitis and raised liver enzymes. Leptospirosis was suspected and treated with the appropriate antibiotics leading to a full recovery. The diagnosis was confirmed by a titre of I/2560 to Leptospira icterohaemorrhagiae. The case illustrates an unusual presentation of this infection and argues for early antibiotic treatment.

Experimental infection of pregnant gilts with Leptospira interrogans serovar mozdok

Three pregnant gilts were experimentally infected with leptospires of the serovar mozdok, isolated from an aborted pig fetus from a Portuguese pig farm with abortion problems. All the gilts aborted dead or dying piglets on days 105 or 106 of pregnancy. Serovar mozdok was isolated from 12 of the 22 piglets in the three litters. Histological examination of the livers and kidneys of the gilts at the end of the experiment revealed evidence of disease, and leptospires were isolated from their kidneys. Their serological responses up to 42 days after inoculation were monitored by means of a microscopic agglutination test, using 21 antigens from 18 serogroups. Cross reactions to heterologous antigens belonging to the Grippotyphosa, Australis, Icterohaemorrhagiae and Cynopteri groups were observed in all of them.