Leptospirosis-induced meningitis and acute renal failure in a 19-month-old male child

Are Pathogenic Leptospira a Possible Cause of Aseptic Meningitis in Suspected Children in Sudan?

INTRODUCTION

Clinical presentations of leptospirosis are diverse, with meningitis easily confused with other microbial causes. We aimed to investigate the involvement of pathogenic leptospira in the cerebrospinal fluid (CSF) of meningitis-suspected children in Sudan.

METHODS

A total of 153 CSF specimens were collected over 5 months from patients attending a reference pediatric hospital in Omdurman, Sudan. All patients had provisionally been diagnosed with meningitis on admission. Demographic, clinical, and conventional laboratory findings were obtained. DNA was extracted using a QIAamp mini kit, and the secY gene investigated using real-time PCR.

RESULTS

Nine of 153 (6%) CSF specimens were positive for pathogenic leptospiral DNA. All these patients were male (seven infants and two toddlers aged ˂4 years). Typical conventional laboratory findings for aseptic meningitis (ie, CSF turbidity/pleocytosis, normal or reduced CSF glucose, normal or elevated proteins) were seen in five (56%). All patients presented with fever and seizures, 56% vomiting and stiff neck, and 29% bulging fontanel. Most (67%) patients presented in summer (March to May). Polymicrobial infections were identified in three patients (33%).

CONCLUSION

We conclude that pathogenic leptospira are probably a common cause of meningitis in children in Sudan; therefore, we recommend including leptospirosis in the differential diagnosis of CNS infections and other undifferentiated febrile illnesses in this country.

Inferring pathogen-host interactions between Leptospira interrogans and Homo sapiens using network theory

Leptospirosis is the most emerging zoonotic disease of epidemic potential caused by pathogenic species of Leptospira. The bacterium invades the host system and causes the disease by interacting with the host proteins. Analyzing these pathogen-host protein interactions (PHPIs) may provide deeper insight into the disease pathogenesis. For this analysis, inter-species as well as intra-species protein interactions networks of Leptospira interrogans and human were constructed and investigated. The topological analyses of these networks showed lesser connectivity in inter-species network than intra-species, indicating the perturbed nature of the inter-species network. Hence, it can be one of the reasons behind the disease development. A total of 35 out of 586 PHPIs were identified as key interactions based on their sub-cellular localization. Two outer membrane proteins (GpsA and MetXA) and two periplasmic proteins (Flab and GlyA) participating in PHPIs were found conserved in all pathogenic, intermediate and saprophytic spp. of Leptospira. Furthermore, the bacterial membrane proteins involved in PHPIs were found playing major roles in disruption of the immune systems and metabolic processes within host and thereby causing infectious disease. Thus, the present results signify that the membrane proteins participating in such interactions hold potential to serve as effective immunotherapeutic candidates for vaccine development.

Pathophysiology of leptospirosis

Leptospirosis is an acute septicemic illness that affects humans in all parts of the world. Approximately 10% of patients with leptospirosis develop severe disease, the Weil syndrome, with jaundice, acute kidney injury (AKI), and pulmonary hemorrhage. Leptospirosis-induced AKI is typically nonoliguric with a high frequency of hypokalemia. Experimental and clinical studies demonstrated that tubular function alterations precede a drop in the glomerular filtration rate and are mainly in the proximal tubule. Studies in humans and animals have demonstrated a decrease in the expression of proximal sodium (NHE3) and water tubular transporter, aquaporin 1 (AQP1) together with higher renal expression of the Na-K-2Cl cotransporter NKCC2. In an experimental model, at the initial phase of the disease, the expression of AQP2, the water transport of the collecting duct, is decreased, which explains the higher incidence of nonoliguric AKI. During the recovery phase of AKI, AQP2 expression increased in human and animals as a compensatory mechanism. Alveolar hemorrhage, pulmonary edema, acute respiratory distress syndrome, or a combination of these features may accompany AKI and is associated with high mortality. Studies with hamsters demonstrated that in leptospirosis a noncardiogenic pulmonary edema occurs consequently to a decrease in the clearance of alveolar fluid, due to a decrease in sodium transporter in the luminal membrane (ENaC) and an increase in the NKCC1 basolateral membrane transporter. Antibiotic treatment is efficient in the early and late/severe phases and revert all kidney transporters. Early and daily hemodialysis, low daily net fluid intake, and lung-protective strategies are recommended for critically ill patients with leptospirosis.

Aseptic meningitis caused by Leptospira spp diagnosed by polymerase chain reaction

Leptospirosis is a zoonotic disease caused by the pathogenic Leptospira spp. The clinical presentations are diverse, ranging from undifferentiated fever to fulminant disease including meningeal forms. The neurological leptospirosis forms are usually neglected. The aim of this study was to investigate leptospirosis as the cause of aseptic meningitis using different diagnostic techniques including the polymerase chain reaction (PCR). Thirty-nine cerebrospinal fluid (CSF) samples from patients presenting with meningeal abnormalities, predominance of lymphocytes and negative results by traditional microbiological tests were processed by leptospiral culture, anti-leptospiral antibody response and PCR. Leptospira spp DNA was detected in 23 (58.97%) of the CSF samples. Anti-leptospiral antibodies were found in 13 (33.33%) CSF samples. Twelve CSF samples were positive by PCR assay and negative by microscopic agglutination test (MAT) assay. Two CSF samples were positive by MAT and negative by PCR. The positive and negative agreement between both tests was 11 and 14, respectively. CSF samples from six cases of unknown diagnosis were positive by PCR assay. Eight cases showed positive results using PCR and MAT. Leptospirosis could be detected by PCR assay from the 3rd-26th day after illness onset. The sensitivity of the PCR was assessed with confirmed cases of leptospirosis (by MAT) and found to be 89.5%. All CSFs were negative by culture. PCR was found to be a powerful tool for diagnosing meningitis cases of leptospirosis. We recommend that it may be used as a supplementary diagnostic tool, especially in the early stages of the disease, when other diagnostic techniques such as serology are not sensitive.

Identification of immunodominant B- and T-cell combined epitopes in outer membrane lipoproteins LipL32 and LipL21 of Leptospira interrogans

Leptospirosis is a serious infectious disease caused by pathogenic Leptospira. B- and T-cell-mediated immune responses contribute to the mechanisms of Leptospira interrogans infection and immune intervention. LipL32 and LipL21 are the conserved outer membrane lipoproteins of L. interrogans and are considered vaccine candidates. In this study, we identified B- and T-cell combined epitopes within LipL32 and LipL21 to further develop a novel vaccine. By using a computer prediction algorithm, two B- and T-cell combined epitopes of LipL21 and four of LipL32 were predicted. All of the predicted epitopes were expressed in a phage display system. Four epitopes, LipL21 residues 97 to 112 and 176 to 184 (LipL21(97-112) and LipL21(176-184), respectively) and LipL32(133-160) and LipL32(221-247) of LipL32 were selected as antigens by Western blotting and enzyme-linked immunosorbent assay. These selected epitopes were also recognized by CD4(+) T lymphocytes derived from LipL21- or LipL32-immunized BALB/c (H-2(d)) mice and mainly polarized the immune response toward a Th1 phenotype. The identification of epitopes that have both B- and T-cell immune reactivities is of value for studying the immune mechanisms in response to leptospiral infection and for designing an effective vaccine for leptospirosis.

Leptospiral nephropathy

Leptospirosis is recognized as a globally re-emerging zoonosis. Interstitial nephritis is the principal feature of the disease. Leptospirosis-induced acute kidney injury typically is nonoliguric and includes hypokalemia. Tubular function alterations precede a decrease in the glomerular filtration rate, which could explain the high frequency of hypokalemia. Studies in human beings and animals have shown increased urinary fractional excretion of potassium and sodium, as well as an increased potassium/sodium ratio, suggesting increased distal potassium secretion caused by increased distal sodium delivery consequent to functional impairment of proximal sodium reabsorption. Confirming these findings, Western blot studies have shown lower renal expression of the sodium/hydrogen exchanger isoform 3 and of aquaporin 2, together with higher renal expression of the Na-K-2Cl cotransporter NKCC2, in infected animals. The severe form (Weil's disease) manifests as diffuse alveolar hemorrhage, pulmonary edema, acute respiratory distress syndrome, or a combination of these features, accompanied by acute kidney injury and can be highly lethal. Antibiotic treatment is efficient in the early and late/severe phases. For critically ill leptospirosis patients, the following are recommended: daily hemodialysis, low daily net fluid intake (because of the risk for pulmonary hemorrhage), and lung-protective strategies (low tidal volumes and high positive end-expiratory pressures after recruitment maneuvers).

The kidney in leptospirosis

Leptospirosis is a worldwide zoonosis. Typically, patients are young men, although children can be affected. In children, this disease causes mainly alterations of sensorium. Acute renal failure and jaundice (Weil's syndrome) are less common in children than in adults. The main renal histological findings are acute interstitial nephritis and acute tubular necrosis. Acute renal failure is characterized by hypokalemia and nonoliguria. Many factors are involved in its physiopathology: hypotension, hypovolemia, rhabdomyolysis, hyperbilirubinemia, and, primarily, the direct action of leptospiral proteins. Antibiotic administration (especially early administration) reduces length of hospitalization and leptospiruria. For children, even late antibiotic treatment has been shown to reduce the extent of acute renal failure and thrombocytopenia. Although the best method of dialysis is not yet established, early and intensive dialysis can decrease mortality. Mortality in patients with acute renal failure is approximately 15-20% in association with the presence of oliguria, higher levels of creatinine, and older age. Functional recovery is fast and complete; however, abnormal urinary concentration can persist.

Leptospirosis vaccines

Leptospirosis is a serious infection disease caused by pathogenic strains of the Leptospira spirochetes, which affects not only humans but also animals. It has long been expected to find an effective vaccine to prevent leptospirosis through immunization of high risk humans or animals. Although some leptospirosis vaccines have been obtained, the vaccination is relatively unsuccessful in clinical application despite decades of research and millions of dollars spent. In this review, the recent advancements of recombinant outer membrane protein (OMP) vaccines, lipopolysaccharide (LPS) vaccines, inactivated vaccines, attenuated vaccines and DNA vaccines against leptospirosis are reviewed. A comparison of these vaccines may lead to development of new potential methods to combat leptospirosis and facilitate the leptospirosis vaccine research. Moreover, a vaccine ontology database was built for the scientists working on the leptospirosis vaccines as a starting tool.

Evaluation of protective immunity of Leptospira immunoglobulin like protein A (LigA) DNA vaccine against challenge in hamsters

We demonstrated earlier that immunization with recombinant Leptospira immunoglobulin like protein A (LigA) induced significant protection against virulent Leptospira interrogans serovar Pomona challenge in hamsters. However, the protective immune mechanism remains unclear. In the present study we demonstrated the protective efficacy of a LigA DNA vaccine and evaluated the immune mechanism underlying the protection against leptospirosis in hamsters. The LigA DNA vaccine was constructed in two truncated forms as the conserved portion (LigAcon) and a variable portion (LigAvar). Four-week-old hamsters were immunized three times at two-week intervals with vector alone or an equal amount of a recombinant construct containing either LigAcon or LigAvar. All animals were challenged intraperitoneally 2 weeks after the last immunization with a dose (LD50=10(8)) of virulent L. interrogans serovar Pomona. Prior to challenge, four animals were sacrificed, the spleen was removed aseptically, and splenocytes were assayed for lymphocyte proliferation and cytokine profiles in response to recall antigen. The protective efficacy was evaluated on the basis of survival and histopathological lesions in the kidney. The immuno-protective mechanism was assessed on the basis of Th1/Th2 profile of cytokines in immunized animals. Our results indicate that immunization with LigA DNA vaccine provides significant protection against leptospirosis. We suggest that immuno-protection is conferred by both humoral and cellular immunity as revealed by an increase in antibody titers during subsequent boosters, significant proliferation of lymphocytes and enhancement of both Th1 and Th2 cytokines. Taken together, the present study suggests that a LigA DNA vaccine is a promising candidate for prevention of leptospirosis.

Severe acute renal failure in a child: a rare complication of anicteric leptospirosis

A 14-year-old male patient was admitted with fever, vomiting, muscular pain, mainly in the lower limbs, oliguria and oedema. The presence of rats in the vicinity of the home was reported. Laboratory tests on admission revealed severely compromised renal function and increased phosphokinase creatine and thrombocytopenia. Although the patient presented an atypical course without jaundice or meningeal involvement, early dialytic treatment was administered concomitant with empiric antibiotic therapy for leptospirosis. The probable infected serogroup by serology was Autumnalis. This atypical case illustrates that, in the presence of fever, renal failure, rhabdomyolysis and thrombocytopenia, leptospirosis should be considered, even in the absence of jaundice or meningitis, especially if there is a history of contact with carrier animals.

Immunogenicity of the recombinant leptospiral putative outer membrane proteins as vaccine candidates

Leptospiral putative outer membrane proteins (OMPs) are likely to be essential components of more effective vaccines. Recently completed genomic sequences of Leptospira allowed us to target putative OMPs for the development of recombinant vaccines. We focused on 12 putative OMPs that had no homology with other organisms listed in the NCBI database except MceI and MceII of Leptospira, which are approximately 25% homologous to MceI of Mycobacterium tuberculosis. All putative OMPs were cloned, expressed and purified as glutathione-S-transferase (GST) fusion proteins. Primary screening for immunoprotective potential was performed in hamsters challenged with an LD50 inoculum of low passage serovar Pomona. Out of these 12 OMPs three fusion proteins viz. rLp1454, rLp1118 and rMceII were found to be protective in a hamster model of leptospirosis. The protective efficacy was evaluated on the basis of survival, histopathological lesions in vital organs and antibody responses against each antigen. All the recombinant proteins were able to enhance the survival and reduce the histopathological lesions. In contrast, control animals immunized with rGST demonstrated low survival and had significant lesions. Further, these three proteins were evaluated for synergistic protective efficacy as compared to LigA, which has already been established as a protective antigen. Our results indicate that rLp1454, rLp1118, and rMceII showed protection individually and synergistically against serovar Pomona infection, which may help us to develop a multicomponent vaccine for leptospirosis.

Leptospirosis: pathogenesis, immunity, and diagnosis

PURPOSE OF REVIEW

Leptospirosis is among the most important zoonotic diseases worldwide. Completion of the genomic sequences of leptospires has facilitated advances in diagnosis and prevention of the disease, and yielded insight into its pathogenesis. This article reviews this research, emphasizing recent progress.

RECENT FINDINGS

Leptospirosis is caused by a group of highly invasive spiral bacteria (spirochetes) that can infect both people and animals. Spirochetes can survive in the environment and host, and therefore outer membrane and secretory proteins that interact with the host are of considerable interest in leptospire research. The genetic approach to studying pathogenesis is hindered by fastidious growth of pathogenic leptospires. Integrated genomic and proteomic approaches, however, have yielded enhanced understanding of the pathogenesis of leptospirosis. Furthermore, studies of innate immune response to the organism have enhanced our understanding of host susceptibility and resistance to infection. In-silico analysis and high-throughput cloning and expression have had major impacts on efforts to develop vaccine candidates and diagnostic reagents.

SUMMARY

In the future, we must effectively utilize the wealth of genetic information to combat the disease. More studies into genetics, immune mechanisms that may be exploited to prevent leptospirosis, and pathogenesis of the disease are necessary.

Antimicrobial therapy of leptospirosis

PURPOSE OF REVIEW

Leptospirosis is an important but often overlooked zoonotic disease that can cause significant morbidity and mortality. The optimal antimicrobial treatment for this disease has not been established. This review summarizes the most recent literature pertaining to the use of antimicrobial agents in the treatment of leptospirosis.

RECENT FINDINGS

Leptospira are highly susceptible to a wide variety of antimicrobials in vitro. Despite this, it is not clear what the best choice of antimicrobial agents is for human disease. Based on the best available literature, the current choices of treatment for leptospirosis include penicillin, doxycycline, cefotaxime, ceftriaxone and azithromycin. Penicillin has long been considered the treatment of choice. Doxycycline is a reasonable alternative, but concerns exist regarding its use in all patients. Recent trials have demonstrated that cefotaxime and ceftriaxone are also acceptable agents. For a variety of reasons, these may be the preferred agents at this time. Azithromycin appears promising for the treatment of less severe disease. Another option for treating leptospirosis is the fluoroquinolone antimicrobials, although adequate human trials are lacking to fully support their use.

SUMMARY

Leptospirosis is an important cause of morbidity and mortality worldwide. Despite this, the optimal treatment is not fully defined.