Ilana Teruszkin Balassiano

Multiplex PCR-based detection of Leptospira in environmental water samples obtained from a slum settlement

The aim of this study was to apply a molecular protocol to detect leptospiral DNA in environmental water samples. The study was carried out in a peri-urban settlement in Petrópolis, state of Rio de Janeiro. A multiplex PCR method employing the primers LipL32 and 16SrRNA was used. Three out of 100 analysed samples were positive in the multiplex PCR, two were considered to have saprophytic leptospires and one had pathogenic leptospires. The results obtained supported the idea that multiplex PCR can be used to detect Leptospira spp in water samples. This method was also able to differentiate between saprophytic and pathogenic leptospires and was able to do so much more easily than conventional methodologies.

Multiplex Nucleic Acid Amplification Test for Diagnosis of Dengue Fever, Malaria, and Leptospirosis

ABSTRACT Dengue, leptospirosis, and malaria are among the most common etiologies of systemic undifferentiated febrile illness (UFI) among travelers to the developing world, and these pathogens all have the potential to cause life-threatening illness in returned travelers. The current study describes the development of an internally controlled multiplex nucleic acid amplification test for the detection of dengue virus (DENV) and Leptospira and Plasmodium species, with a specific callout for Plasmodium falciparum (referred to as the UFI assay). During analytical evaluation, the UFI assay displayed a wide dynamic range and a sensitive limit of detection for each target, including all four DENV serotypes. In a clinical evaluation including 210 previously tested samples, the sensitivities of the UFI assay were 98% for DENV (58/59 samples detected) and 100% for Leptospira and malaria (65/65 and 20/20 samples, respectively). Malaria samples included all five Plasmodium species known to cause human disease. The specificity of the UFI assay was 100% when evaluated with a panel of 66 negative clinical samples. Furthermore, no amplification was observed when extracted nucleic acids from related pathogens were tested. Compared with whole-blood samples, the UFI assay remained positive for Plasmodium in 11 plasma samples from patients with malaria (parasitemia levels of 0.0037 to 3.4%). The syndrome-based design of the UFI assay, combined with the sensitivities of the component tests, represents a significant improvement over the individual diagnostic tests available for these pathogens.

Sensitive Real-Time PCR Detection of Pathogenic Leptospira spp. and a Comparison of Nucleic Acid Amplification Methods for the Diagnosis of Leptospirosis

Background Bacteria of the genus Leptospira, the causative agents of leptospirosis, are categorized into pathogenic and non-pathogenic species. However, the benefit of using a clinical diagnostic that is specific for pathogenic species remains unclear. In this study, we present the development of a real-time PCR (rtPCR) for the detection of pathogenic Leptospira (the pathogenic rtPCR), and we perform a comparison of the pathogenic rtPCR with a published assay that detects all Leptospira species [the undifferentiated febrile illness (UFI) assay] and a reference 16S Leptospira rtPCR, which was originally designed to detect pathogenic species. Methodology/Principal Findings For the pathogenic rtPCR, a new hydrolysis probe was designed for use with primers from the UFI assay, which targets the 16S gene. The pathogenic rtPCR detected Leptospira DNA in 37/37 cultured isolates from 5 pathogenic and one intermediate species. Two strains of the non-pathogenic L. biflexa produced no signal. Clinical samples from 65 patients with suspected leptospirosis were then tested using the pathogenic rtPCR and a reference Leptospira 16S rtPCR. All 65 samples had tested positive for Leptospira using the UFI assay; 62 (95.4%) samples tested positive using the pathogenic rtPCR (p = 0.24). Only 24 (36.9%) samples tested positive in the reference 16S rtPCR (p<0.0001 for comparison with the pathogenic rtPCR and UFI assays). Amplicon sequencing confirmed the detection of pathogenic Leptospira species in 49/50 cases, including 3 cases that were only detected using the UFI assay. Conclusions/Significance The pathogenic rtPCR displayed similar sensitivity to the UFI assay when testing clinical specimens with no difference in specificity. Both assays proved significantly more sensitive than a real-time molecular test used for comparison. Future studies are needed to investigate the clinical and epidemiologic significance of more sensitive Leptospira detection using these tests.

Leptospirosis diagnosis by immunocapture polymerase chain reaction: a new tool for early diagnosis and epidemiologic surveillance

The aim of this study was to develop an immunocapture polymerase chain reaction (IC-PCR) protocol for leptospirosis. For the standardization of IC-PCR, polyclonal (AS) and monoclonal (MAb) antibodies against different serogroups and serovars of Leptospira were coupled to polystyrene plates. Human sera were artificially contaminated with leptospires and incubated on plates. The bacterial DNA was obtained and used in a multiplex PCR. Sensitivity was tested using sera contaminated with crescent concentrations of leptospires, while specificity was established using sera contaminated with different bacterial genera and sera obtained from patients positive for viral infections. IC-PCR using AS was able to recognize specific serogroups, although some cross-reactions have been observed. No cross-reactions were observed when MAbs were used; however, the sensitivity in this case was lower than that of IC-PCR using AS. IC-PCR proved to be specific to Leptospira and is a promising tool for early diagnosis of leptospirosis, providing additional information about the infecting serovar or serogroup.

The involvement of tetA and tetE tetracycline resistance genes in plasmid and chromosomal resistance of Aeromonas in Brazilian strains

This study analyzed the involvement of tetA and tetE genes in the tetracycline resistance of 16 strains of genus Aeromonas, isolated from clinical and food sources. Polymerase chain reactions revealed that 37.5% of the samples were positive for tetA, and also 37.5% were tetE positive. One isolate was positive for both genes. Only the isolate A. caviae 5.2 had its resistance associated to the presence of a plasmid, pSS2. The molecular characterization of pSS2 involved the construction of its restriction map and the determination of its size. The digestion of pSS2 with HindIII originated two fragments (A and B) that were cloned separately into the pUC18 vector. The tetA gene was shown to be located on the HindIII-A fragment by PCR. After transforming a tetracycline-sensitive strain with pSS2, the transformants expressed the resistance phenotype and harbored a plasmid whose size was identical to that of pSS2. The results confirmed the association between pSS2 and the tetracycline resistance phenotype, and suggest a feasible dissemination of tetA and tetE among strains of Aeromonas. This study suggests the spreading tetA and tetE genes in Aeromonas in Brazil and describes a resistance plasmid that probably contributes to the dissemination of the resistance.

Reverse-Transcriptase PCR Detection of Leptospira: Absence of Agreement with Single-Specimen Microscopic Agglutination Testing

Background Reference diagnostic tests for leptospirosis include nucleic acid amplification tests, bacterial culture, and microscopic agglutination testing (MAT) of acute and convalescent serum. However, clinical laboratories often do not receive paired specimens. In the current study, we tested serum samples using a highly sensitive real-time nucleic acid amplification test for Leptospira and compared results to MAT performed on the same specimens. Methods/Principal Findings 478 serum samples from suspected leptospirosis cases in Rio de Janeiro were tested using a real-time RT-PCR for the diagnosis of leptospirosis, malaria and dengue (the Lepto-MD assay). The Lepto-MD assay detects all species of Leptospira (saprophytic, intermediate, and pathogenic), and in the current study, we demonstrate that this assay amplifies both Leptospira RNA and DNA. Dengue virus RNA was identified in 10 patients, and no cases of malaria were detected. A total of 65 samples (13.6%) were positive for Leptospira: 35 samples (7.3%) in the Lepto-MD assay, 33 samples (6.9%) by MAT, and 3 samples tested positive by both (kappa statistic 0.02). Poor agreement between methods was consistent regardless of the titer used to define positive MAT results or the day of disease at sample collection. Leptospira nucleic acids were detected in the Lepto-MD assay as late as day 22, and cycle threshold values did not differ based on the day of disease. When Lepto-MD assay results were added to the MAT results for all patients in 2008 (n=818), the number of detected leptospirosis cases increased by 30.4%, from 102 (12.5%) to 133 (16.3%). Conclusions/Significance This study demonstrates a lack of agreement between nucleic acid detection of Leptospira and single-specimen MAT, which may result from the clearance of bacteremia coinciding with the appearance of agglutinating antibodies. A combined testing strategy for acute leptospirosis, including molecular and serologic testing, appears necessary to maximize case detection.

Seroepidemiology of leptospirosis among febrile patients in a rapidly growing suburban slum and a flood-vulnerable rural district in Mozambique, 2012–2014: Implications for the management of fever

OBJECTIVE Leptospirosis is one of the most widespread zoonoses in the world and is caused by spirochetes of the genus Leptospira. In Mozambique, the disease is largely ignored and its epidemiology is unknown. The objective of this study was to investigate the occurrence of leptospirosis in febrile patients. METHODS This cross-sectional study was performed between July 2012 and September 2015 among febrile patients. A total of 373 paired serum samples were drawn from febrile patients; 208 were from Caia District Hospital (rural setting) in Sofala Province and 165 were from Polana Caniço General Hospital (suburban setting) in Maputo City. Samples were initially screened using an in-house ELISA for IgM and IgG antibodies. Double positive samples were confirmed using a microagglutination test (MAT). RESULTS Of the 373 febrile patients, five (1.3%) had acute leptospirosis (MAT ≥400) and 38 (10.2%) had a presumptive infection (IgM-positive/MAT <400). While most of the patients with a presumptive infection lived in the rural setting (84.2%, 32/38), the majority of patients with acute infections (60%, 3/5) and with negative results (60.3%, 199/330) lived in the suburban setting (p=0.000). Contact with rodents was significantly higher in patient with acute leptospirosis (100%, 5/5) than in those with a presumptive infection (39.5%, 15/38) or negative results (41.8%, 138/330) (p=0.031). Four out of the five patients (80%) with acute leptospirosis were treated with antimalarial drugs although malaria results were negative. The prevailing serogroup, according to MAT results, was Australis (40%; 4/10), followed by Icterohaemorrhagiae (30%, 3/10). CONCLUSIONS This study found that leptospirosis is prevalent among Mozambicans, and most cases are misdiagnosed as malaria.

Molecular and serological characterization of Leptospira kirschneri serogroup Pomona isolated from a human case in a Brazilian rural area

INTRODUCTION: Leptospirosis is an important health concern in Brazil. Currently, information on the epidemiology of the disease in the rural areas of the country is lacking. METHODS: Serological and molecular techniques were used to characterize a clinical isolate of Leptospira. RESULTS: The strain CLEP 00060, isolated from a 59-year-old man in a rural area of Rio Grande do Sul state, Brazil, was identified as belonging to L. kirschneri serogroup Pomona serovar Mozdok. CONCLUSIONS: This study contributes to the local epidemiological knowledge of leptospirosis, prevention of the disease by vaccines, and improvements in its diagnosis.

Seroprevalence of and risk factors for leptospirosis in the City of Manaus, State of Amazonas, Brazil

INTRODUCTION Leptospirosis is caused by a bacterium of the genus Leptospira. This study aimed at investigating the seroprevalence of and risk factors for leptospirosis in humans in Manaus, State of Amazonas. METHODS Interviews were performed, and 1,000 blood serum samples were examined using a microscopic agglutination test. RESULTS Forty-three cases were positive; there were 10 serotypes, with coagglutination in 8 cases. The most frequently occurring serotypes were Icterohaemorrhagiae (20.7%), Cynopteri (20.7%), Australis (18.8%), and Copenhageni (16.9%), and the Midwest (54.7%) and South (23.8%) had the most cases; these areas lack basic sanitation. CONCLUSIONS Disease occurrence might be reduced through improved basic infrastructural conditions.