Molecular confirmation of co-infection by pathogenic Leptospira spp. and Orientia tsutsugamushi in patients with acute febrile illness in Thailand

Double Blow in the Tropics: A Case of Concurrent Leptospirosis and Scrub Typhus

A 34-year-old male, with no history of known previous disease, employed at a ginger farm in South India, presented with a four-day history of high-grade fever and headache. Initially, he received symptomatic treatment but was referred due to hypotension and persistent fever. Investigations showed leucocytosis, thrombocytopenia, abnormal liver function tests, renal dysfunction, and elevated C-reactive protein. Positive results were obtained for Leptospira immunoglobulin M (IgM) and scrub typhus IgM tests, indicating a coinfection, reported rarely from this region. Timely clinical suspicion, prompt laboratory diagnosis, and early treatment with doxycycline and broad-spectrum antibiotics are crucial to prevent complications and fatal outcomes in such coinfections.

Putative Pathogenic Genes of Leptospira interrogans and Leptospira weilii Isolated from Patients with Acute Febrile Illness

Leptospirosis is an important worldwide tropical disease caused by pathogenic Leptospira spp. The determination of virulence genes is important, as it influences patients' clinical manifestations and clinical outcomes. This case report focused on detecting the pathogenic genes of Leptospira in association with the clinical manifestations of patients at the Hospital Universiti Sains Malaysia, Malaysia, who presented with acute febrile illness. Two cases were found and, to the best of our knowledge, these were the first two cases in Malaysia in which patients presented with febrile illness were associated with successful Leptospira isolation from clinical samples. Both clinical isolates were identified by 16S rRNA sequencing as Leptospira weilii and Leptospira interrogans, respectively, and they were classified as pathogenic Leptospira by the presence of different pathogenic genes, based on a polymerase chain reaction (PCR) amplification of targeted genes. This report emphasizes that different infecting Leptospira species and the presence of different virulence factors cause a slight difference in clinical manifestations and laboratory findings of leptospirosis. Genomic sequencing and annotation revealed the detection of classical leptospiral virulence factor genes that were otherwise missed using PCR for detection of Leptospira weilii genome B208.

Changing spectrum of acute encephalitis syndrome in India and a syndromic approach

Acute encephalitis syndrome (AES) refers to an acute onset of fever and clinical neurological manifestation that includes mental confusion, disorientation, delirium, or coma, which may occur because of infectious or non-infectious causes. Cerebrospinal fluid (CSF) pleocytosis generally favors infectious etiology, and a normal CSF favors an encephalopathy or non-infectious AES. Among the infectious AES, viral, bacterial, rickettsial, fungal, and parasitic causes are the commonest. Geographical and seasonal clustering and other epidemiological characteristics are important in clinical decision making. Clinical markers like eschar, skin rash, myalgia, hepatosplenomegaly, thrombocytopenia, liver and kidney dysfunction, elevated serum CK, fronto-temporal or thalamic involvement on MRI, and anterior horn cell involvement are invaluable clues for the etiological diagnosis. Categorizing the AES cases into neurologic [Herpes simplex encephalitis (HSE), Japanese encephalitis (JE), and West Nile encephalitis (WNE)] and systemic (scrub typhus, malaria, dengue, and Chikungunya) helps in rational utilization of diagnostic and management resources. In neurological AES, cranial CT/MRI revealing frontotemporal lesion is consistent with HSE, and thalamic and basal ganglia lesions are consistent with JE. Cerebrospinal fluid nucleic acid detection test or IgM antibody for JE and HSE are confirmatory. Presence of frontotemporal involvement on MRI indicates acyclovir treatment pending virological confirmation. In systemic AES, CT/MRI, PCR for HSE and JE, and acyclovir therapy may not be useful, rather treatable etiologies such as malaria, scrub typhus, and leptospirosis should be looked for. If smear or antigen for malaria is positive, should receive antimalarial, if negative doxycycline and ceftriaxone should be started pending serological confirmation of scrub typhus, leptospira, or dengue. A syndromic approach of AES based on the prevalent infection in a geographical region may be developed, which may be cost-effective.

Leptospiral Infection, Pathogenesis and Its Diagnosis-A Review

Leptospirosis is a perplexing conundrum for many. In the existing literature, the pathophysiological mechanisms pertaining to leptospirosis is still not understood in full. Considered as a neglected tropical zoonotic disease, leptospirosis is culminating as a serious problem worldwide, seemingly existing as co-infections with various other unrelated diseases, including dengue and malaria. Misdiagnosis is also common as non-specific symptoms are documented extensively in the literature. This can easily lead to death, as the severe form of leptospirosis (Weil's disease) manifests as a complex of systemic complications, especially renal failure. The virulence of Leptospira sp. is usually attributed to the outer membrane proteins, including LipL32. With an armament of virulence factors at their disposal, their ability to easily adhere, invade and replicate within cells calls for a swift refinement in research progress to establish their exact pathophysiological framework. As an effort to reconstitute the current knowledge on leptospirosis, the basis of leptospiral infection, including its risk factors, classification, morphology, transmission, pathogenesis, co-infections and clinical manifestations are highlighted in this review. The various diagnostic techniques are also outlined with emphasis on their respective pros and cons.

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.

Nucleic acid and antigen detection tests for leptospirosis

BACKGROUND

Early diagnosis of leptospirosis may contribute to the effectiveness of antimicrobial therapy and early outbreak recognition. Nucleic acid and antigen detection tests have the potential for early diagnosis of leptospirosis. With this systematic review, we assessed the sensitivity and specificity of nucleic acid and antigen detection tests.

OBJECTIVES

To determine the diagnostic test accuracy of nucleic acid and antigen detection tests for the diagnosis of human symptomatic leptospirosis.

SEARCH METHODS

We searched electronic databases including MEDLINE, Embase, the Cochrane Library, and regional databases from inception to 6 July 2018. We did not apply restrictions to language or time of publication.

SELECTION CRITERIA

We included diagnostic cross-sectional studies and case-control studies of tests that made use of nucleic acid and antigen detection methods in people suspected of systemic leptospirosis. As reference standards, we considered the microscopic agglutination test alone (which detects antibodies against leptospirosis) or in a composite reference standard with culturing or other serological tests. Studies were excluded when the controls were healthy individuals or when there were insufficient data to calculate sensitivity and specificity.

DATA COLLECTION AND ANALYSIS

At least two review authors independently extracted data from each study. We used the revised Quality Assessment of Diagnostic Accuracy Studies tool (QUADAS-2) to assess risk of bias. We calculated study-specific values for sensitivity and specificity with 95% confidence intervals (CI) and pooled the results in a meta-analysis when appropriate. We used the bivariate model for index tests with one positivity threshold, and we used the hierarchical summary receiver operating characteristic model for index tests with multiple positivity thresholds. As possible sources of heterogeneity, we explored: timing of index test, disease prevalence, blood sample type, primers or target genes, and the real-time polymerase chain reaction (PCR) visualisation method. These were added as covariates to the meta-regression models.

MAIN RESULTS

We included 41 studies evaluating nine index tests (conventional PCR (in short: PCR), real-time PCR, nested PCR, PCR performed twice, loop-mediated isothermal amplification, enzyme-linked immunosorbent assay (ELISA), dot-ELISA, immunochromatography-based lateral flow assay, and dipstick assay) with 5981 participants (1834 with and 4147 without leptospirosis). Methodological quality criteria were often not reported, and the risk of bias of the reference standard was generally considered high. The applicability of findings was limited by the frequent use of frozen samples. We conducted meta-analyses for the PCR and the real-time PCR on blood products.The pooled sensitivity of the PCR was 70% (95% CI 37% to 90%) and the pooled specificity was 95% (95% CI 75% to 99%). When studies with a high risk of bias in the reference standard domain were excluded, the pooled sensitivity was 87% (95% CI 44% to 98%) and the pooled specificity was 97% (95% CI 60% to 100%). For the real-time PCR, we estimated a summary receiver operating characteristic curve. To illustrate, a point on the curve with 85% specificity had a sensitivity of 49% (95% CI 30% to 68%). Likewise, at 90% specificity, sensitivity was 40% (95% CI 24% to 59%) and at 95% specificity, sensitivity was 29% (95% CI 15% to 49%). The median specificity of real-time PCR on blood products was 92%. We did not formally compare the diagnostic test accuracy of PCR and real-time PCR, as direct comparison studies were lacking. Three of 15 studies analysing PCR on blood products reported the timing of sample collection in the studies included in the meta-analyses (range 1 to 7 days postonset of symptoms), and nine out of 16 studies analysing real-time PCR on blood products (range 1 to 19 days postonset of symptoms). In PCR studies, specificity was lower in settings with high leptospirosis prevalence. Other investigations of heterogeneity did not identify statistically significant associations. Two studies suggested that PCR and real-time PCR may be more sensitive on blood samples collected early in the disease stage. Results of other index tests were described narratively.

AUTHORS' CONCLUSIONS

The validity of review findings are limited and should be interpreted with caution. There is a substantial between-study variability in the accuracy of PCR and real-time PCR, as well as a substantial variability in the prevalence of leptospirosis. Consequently, the position of PCR and real-time PCR in the clinical pathway depends on regional considerations such as disease prevalence, factors that are likely to influence accuracy, and downstream consequences of test results. There is insufficient evidence to conclude which of the nucleic acid and antigen detection tests is the most accurate. There is preliminary evidence that PCR and real-time PCR are more sensitive on blood samples collected early in the disease stage, but this needs to be confirmed in future studies.

Development of multiplex PCR for neglected infectious diseases

Scrub typhus, murine typhus, and leptospirosis are widely neglected infectious diseases caused by Orientia tsutsugamushi, Rickettsia typhi, and pathogenic Leptospira spp., respectively. Patients usually present with non-specific symptoms and therefore are commonly diagnosed with acute undifferentiated febrile illness. Consequently, patients face delayed treatment and increased mortality. Antibody-based serological test currently used as gold standard has limitations due to insufficient antibody titers, especially in the early phase of infection. In this study, we aimed to develop multiplex PCR to combine 3 primer pairs that target specific genes encoding 56-kDa TSA of O. tsutsugamushi, 17-kDa antigen of R. typhi, and LipL32 of L. Interrogans and evaluate its performance in comparison to the standard serological tests. Using EDTA blood samples of known patients, the sensitivity and specificity of our multiplex PCR was 100% and 70%, respectively. In addition, the assay was able to diagnose the co-infection of scrub typhus and leptospirosis. The assay may be useful in identifying causative agents during the early phase of these diseases, enabling prompt and appropriate treatment.

Scrub typhus, murine typhus, and leptospirosis are diagnosed as acute undifferentiated febrile illness. Diagnostic tests for these diseases depend on antibody detection. However, antibody detection is still limited by its tendency to return negative results during the early phase of aforementioned diseases. In this study, a novel multiplex PCR has been developed for detecting Orientia tsutsugamushi, Rickettsia typhi, and Leptospira interrogans that are simultaneously amplified in a single tube. The results have shown that multiplex PCR could be used as a diagnostic tool for detecting bacteria during the early phase of scrub typhus, murine typhus, and leptospirosis, allowing for administration of appropriate treatment.

Severe leptospirosis in a patient with positive serological test for spotted fever rickettsiosis

Here, we report a case of a 64-year-old man with severe leptospirosis infected in an area in Japan that is non-endemic to leptospirosis. Initially, findings of high-grade fever, mild generalised arthralgia, rashes on the trunk, mild thrombocytopenia, elevated liver enzymes and renal dysfunction led to the suspicion of rickettsiosis, which was an endemic infectious disease in the area. Subsequently, leptospirosis was also considered after carefully reviewing patient history, which revealed that he may have been exposed to mice urine. Finally, leptospirosis was diagnosed after the serum indicated a positive PCR for leptospirosis. Furthermore, due to serum antibody positivity for Rickettsia japonica, false-positivity or coinfection of spotted fever rickettsiosis was suspected. Despite the delayed diagnosis, the patient recovered with antibiotic treatment. Thus, to prevent diagnostic errors, leptospirosis should be potentially considered with high suspicion in patients with acute undifferentiated fever, even in non-endemic areas of leptospirosis.

Leptospirosis: Molecular trial path and immunopathogenesis correlated with dengue, malaria and mimetic hemorrhagic infections

Immuno-pathogenesis of leptospirosis can be recounted well by following its trail path from entry to exit, while inducing disastrous damages in various tissues of the host. Dysregulated, inappropriate and excessive immune responses are unanimously blamed in fatal leptospirosis. The inherent abilities of the pathogen and inabilities of the host were debated targeting the severity of the disease. Hemorrhagic manifestation through various mechanisms leading to a fatal end is observed when this disease is unattended. The similar vascular destructions and hemorrhage manifestations are noted in infections with different microbes in endemic areas. The simultaneous infection in a host with more than one pathogen or parasite is referred as the coinfection. Notably, common endemic infections such as leptospirosis, dengue, chikungunya, and malaria, harbor favorable environments to flourish in similar climates, which is aggregated with stagnated water and aggravated with the poor personal and environmental hygiene of the inhabitants. These factors aid the spread of pathogens and parasites to humans and potential vectors, eventually leading to outbreaks of public health relevance. Malaria, dengue and chikungunya need mosquitoes as vectors, in contrast with leptospirosis, which directly invades human, although the environmental bacterial load is maintained through other mammals, such as rodents. The more complicating issue is that infections by different pathogens exhibiting similar symptoms but require different treatment management. The current review explores different pathogens expressing specific surface proteins and their ability to bind with array of host proteins with or without immune response to enter into the host tissues and their ability to evade the host immune responses to invade and their affinity to certain tissues leading to the common squeal of hemorrhage. Furthermore, at the host level, the increased susceptibility and inability of the host to arrest the pathogens' and parasites' spread in different tissues, various cytokines accumulated to eradicate the microorganisms and their cellular interactions, the antibody dependent defense and the susceptibility of individual organs bringing the manifestation of the diseases were explored. Lastly, we provided a discussion on the immune trail path of pathogenesis from entry to exit to narrate the similarities and dissimilarities among various hemorrhagic fevers mentioned above, in order to outline future possibilities of prevention, diagnosis, and treatment of coinfections, with special reference to endemic areas.

Scrub typhus: risks, diagnostic issues, and management challenges

Scrub typhus is an acute febrile illness in the “tsutsugamushi triangle”, transmitted by chiggers that can be treated effectively if detected early. Laboratory testing, including molecular and serological assays, is needed for confirming the diagnosis, especially in the absence of the pathognomonic eschar. In this review, factors that play a role in disease occurrence and clinical clues for diagnosis, in addition to risk factors contributing to disease severity, including mortality, are discussed in detail. Moreover, issues related to diagnostic assays, treatment, and mixed infections are also enumerated and described.

An ELISA assay using a combination of recombinant proteins from multiple strains of Orientia tsutsugamushi offers an accurate diagnosis for scrub typhus

Background

Scrub typhus (ST) is a disease caused by an obligate intracellular bacterium, Orientia tsutsugamushi, an organism that requires a BSL3 laboratory for propagation. The disease is hallmarked by an eschar at the site of the chigger bite, followed by the development of fever, malaise, myalgia, anorexia, and papulomacular rash. Indirect immunofluorescent assay (IFA) is the gold standard for scrub typhus diagnosis, however, the subjectivity of the assay, the need for a specialized laboratory and instruments has limited the wide use of the test in resource limited areas.

Methods

A recombinant-protein based enzyme linked immunosorbent assay (ELISA) using the most abundant and immunodominant protein for the detection of Orientia specific antibodies in serum has been developed. The performance of the assay was evaluated using prospectively collected acute sera from 248 randomly selected patients in Thailand. The ELISA assay was evaluated using two different cutoff values.

Results

The receiver operating characteristic (ROC) curve generated cutoff values gave slightly better consistency with diagnosis of ST than those cutoff values established by averaging ELISA optical density of known negatives at 99% confidence interval. Both cutoff values provided similar statistical parameters when compared with the diagnosis of ST, indicating the validity of both calculations to derive cutoff values. These results suggest that both IgG and IgM ELISA performed well to accurately diagnose scrub typhus cases in endemic areas using only acute serum samples.

Conclusions

We have successfully developed an ELISA assay for the detection of Orientia-specific antibodies in serum that could provide effective screening of acute sera under clinical setup and it is also a useful assay to estimate seroprevalence in various endemic areas.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2512-8) contains supplementary material, which is available to authorized users.

Scrub Typhus and Its Causative Agent, Orientia tsutsugamushi

The obligate intracellular bacterium Orientia tsutsugamushi is responsible for more than one million cases of scrub typhus annually throughout the Asia-Pacific region. Human infection occurs via the bite of the larval form (chigger) of several species of trombiculid mites. While in some patients the result of infection is a mild, febrile illness, others experience severe complications, which may even be fatal. This review discusses the genome and biology of the causative agent, the changing epidemiology of scrub typhus, the challenges of its diagnosis, and current treatment recommendations.

How to Determine the Accuracy of an Alternative Diagnostic Test when It Is Actually Better than the Reference Tests: A Re-Evaluation of Diagnostic Tests for Scrub Typhus Using Bayesian LCMs

Background

The indirect immunofluorescence assay (IFA) is considered a reference test for scrub typhus. Recently, the Scrub Typhus Infection Criteria (STIC; a combination of culture, PCR assays and IFA IgM) were proposed as a reference standard for evaluating alternative diagnostic tests. Here, we use Bayesian latent class models (LCMs) to estimate the true accuracy of each diagnostic test, and of STIC, for diagnosing scrub typhus.

Methods/Principal Findings

Data from 161 patients with undifferentiated fever were re-evaluated using Bayesian LCMs. Every patient was evaluated for the presence of an eschar, and tested with blood culture for Orientia tsutsugamushi, three different PCR assays, IFA IgM, and the Panbio IgM immunochromatographic test (ICT). True sensitivity and specificity of culture (24.4% and 100%), 56kDa PCR assay (56.8% and 98.4%), 47kDa PCR assay (63.2% and 96.1%), groEL PCR assay (71.4% and 93.0%), IFA IgM (70.0% and 83.8%), PanBio IgM ICT (72.8% and 96.8%), presence of eschar (42.7% and 98.9%) and STIC (90.5% and 82.5%) estimated by Bayesian LCM were considerably different from those obtained when using STIC as a reference standard. The IgM ICT had comparable sensitivity and significantly higher specificity compared to IFA (p=0.34 and p<0.001, respectively).

Conclusions

The low specificity of STIC was caused by the low specificity of IFA IgM. Neither STIC nor IFA IgM can be used as reference standards against which to evaluate alternative diagnostic tests. Further evaluation of new diagnostic tests should be done with a carefully selected set of diagnostic tests and appropriate statistical models.

Dot-ELISA Rapid Test Using Recombinant 56-kDa Protein Antigens for Serodiagnosis of Scrub Typhus

We developed a rapid dot-enzyme-linked immunosorbent assay (dot-ELISA) using the combination of recombinant 56-kDa protein antigens that exhibited broad reactivity with serum antibodies against the four most prevalent strains (Karp, Kato, Gilliam, and TA763) of Orientia tsutsugamushi. The assay is rapid (30 minutes), and can be done at room temperature, and results can be read by the naked eye. Only a simple shaker is required to wash the membrane. Sera from 338 patients suspected of being ill with scrub typhus from rural hospitals around Thailand were tested using this dot-ELISA. Seventy-five (22.2%) patients were found to be positive. The sensitivity and specificity of dot-ELISA were determined using the indirect immunofluorescent assay (IFA) test as the gold standard, with the cutoff titer of immunoglobulin peroxidase conjugate M (IgM)/G (IgG) greater than 1:400/1:400. The dot-ELISA had a sensitivity of 98.5%, a specificity of 96.3%, a positive predictive value of 86.7%, and a negative predictive value of 99.6% for the acute-phase specimens. The results indicate that dot-ELISA rapid test using recombinant 56-kDa protein antigen was comparable with the IFA test and may be very useful for the diagnosis of scrub typhus in rural hospitals, where IFA is not available.