Blood Parasite Load as an Early Marker to Predict Treatment Response in Visceral Leishmaniasis in Eastern Africa

BACKGROUND

To expedite the development of new oral treatment regimens for visceral leishmaniasis (VL), there is a need for early markers to evaluate treatment response and predict long-term outcomes.

METHODS

Data from 3 clinical trials were combined in this study, in which Eastern African VL patients received various antileishmanial therapies. Leishmania kinetoplast DNA was quantified in whole blood with real-time quantitative polymerase chain reaction (qPCR) before, during, and up to 6 months after treatment. The predictive performance of pharmacodynamic parameters for clinical relapse was evaluated using receiver-operating characteristic curves. Clinical trial simulations were performed to determine the power associated with the use of blood parasite load as a surrogate endpoint to predict clinical outcome at 6 months.

RESULTS

The absolute parasite density on day 56 after start of treatment was found to be a highly sensitive predictor of relapse within 6 months of follow-up at a cutoff of 20 parasites/mL (area under the curve 0.92, specificity 0.91, sensitivity 0.89). Blood parasite loads correlated well with tissue parasite loads (ρ = 0.80) and with microscopy gradings of bone marrow and spleen aspirate smears. Clinical trial simulations indicated a > 80% power to detect a difference in cure rate between treatment regimens if this difference was high (> 50%) and when minimally 30 patients were included per regimen.

CONCLUSIONS

Blood Leishmania parasite load determined by qPCR is a promising early biomarker to predict relapse in VL patients. Once optimized, it might be useful in dose finding studies of new chemical entities.

In vitro evaluation of traditionally used Surinamese medicinal plants for their potential anti-leishmanial efficacy

ETHNOPHARMACOLOGICAL RELEVANCE

Plant-based preparations are extensively used in Surinamese folk medicine for treating leishmaniasis, but often without a scientific rationale.

AIM OF THE STUDY

To evaluate 25 Surinamese medicinal plants for their potential efficacy against leishmaniasis.

MATERIALS AND METHODS

Concentrated plant extracts were evaluated for their effect on the viability of L. (V.) guyanensis AMC, L. (L.) major NADIM5, and L. (L.) donovani GEDII promastigotes, as well as intracellular amastigotes of L. (L.) donovani BHU814 in infected THP-1 cells. Selectivity was assessed by cytotoxicity against THP-1 cells.

RESULTS

The only plant extract that showed potentially meaningful anti-leishmanial activity was that from Solanum lycocarpum that displayed mean IC50 values of about 51, 61, and <16 µg/mL against L. (V) guyanensis, L. (L) major, and L. (L) donovani promastigotes, respectively; about 374 µg/mL against L. (L) donovani amastigotes; and >500 µg/mL against THP-1 cells. The Bryophyllum pinnatum, Inga alba, and Quassia amara extracts displayed moderate to high IC50 values against promastigotes (about 51 to >500 µg/mL) and/or amastigotes (about 224 to >500 µg/mL) but were relatively toxic to THP-1 cells (IC50 values <16 to about 42 µg/mL). The remaining plant extracts exhibited in many cases IC50 values close to, around, or above 500µg/mL against promastigotes, amastigotes, and THP-1 cells.

CONCLUSIONS

The S. lycocarpum preparation may be useful against leishmaniasis and may have a good safety index, warranting further investigations into its active constituents and mechanism(s) of action.

Duplex quantitative Reverse-Transcriptase PCR for simultaneous assessment of drug activity against Leishmania intracellular amastigotes and their host cells

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A duplex qRT-PCR was optimized for use in drug screening against Leishmania.

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Drug activities were measured against the intracellular amastigote stage.

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Cytotoxicity against the human host cells was simultaneously assessed.

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Consistent and reproducible dose–response data were generated.

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Suitability of this duplex PCR for anti-leishmanial drug screening was demonstrated.

Currently available drugs for treatment of Leishmania infections are highly toxic and drug resistance to first line therapies has been observed. New, safer and more effective drugs are urgently needed to improve clinical resolution of the disease and reduce the risks associated with it. High-throughput screening of new compounds against cultured promastigotes is easy to perform, but the results are poorly predictive of in vivo efficacy. Intra-macrophage amastigote models provide a better proxy of the clinically relevant stage of disease and should be routinely implemented in the search for new anti-leishmanial agents, despite being labor intensive.

This study describes the use of a duplex quantitative Reverse-Transcriptase PCR (qRT-PCR) for assessment of drug activity against Leishmania intracellular amastigotes and their host cells. The assay simultaneously quantifies Leishmania 18S ribosomal RNA and the human β2-microglobulin (β-2M) mRNA, used for monitoring drug cytotoxicity and test performance. Accurate determination of parasite viability by the newly developed qRT-PCR was confirmed by parallel assessment of compound performance against standard microscopy. Highly reproducible anti-leishmanial activities were obtained with a set of structurally- and pharmacologically-diverse compounds, whose toxicity against host cells correlated with a low β-2M amplification. Sensitive and versatile, this duplex qRT-PCR offers a valuable tool for assessment of drug activities against Leishmania amastigotes and their host cells.

Dynamics of parasite clearance in cutaneous leishmaniasis patients treated with miltefosine

Parasite loads were quantified in repeated skin biopsies from lesions of 2 patients with Old-World cutaneous leishmaniasis (CL) caused by Leishmania major and L. infantum during and after treatment with miltefosine. Miltefosine induced a rapid therapeutic effect on both infections with an initial decline of parasites of ∼1 log/week for the L. major infection. These observations illustrate the usability of quantifying parasite loads in skin lesions as a pharmacodynamic measure and quantitative descriptor of drug effect for CL supporting clinical assessment.

Comparison of short-term and long-term protocols for stabilization and preservation of RNA and DNA of Leishmania, Trypanosoma, and Plasmodium

Molecular tools continue to be important in the prevention and control of parasitic diseases. However, using these techniques directly in the field remains a major challenge. Therefore, the preservation of clinical samples collected from endemic field areas for later analysis remains an important preanalytical process. This study aimed at identifying a suitable protocol for stabilization and preservation of RNA and DNA in bioclinical specimens for Trypanosoma, Leishmania, and Plasmodium research. Both spiked and unspiked blood samples were preserved in 7 protocols (different media; storage temperatures). Samples were evaluated for possible degradation of DNA and RNA along the storage duration up to the 10th week. Nucleic acid targets were assessed as follows: (i) Trypanosoma and Plasmodium RNA analysis was done using real-time nucleic acid sequence-based amplification (RT-NASBA) for 18S rRNA and for stage-specific Pfs25 mRNA, respectively; (ii) Trypanosoma DNA assessment analysis was conducted by using a conventional PCR for 18S rDNA; (iii) Leishmania RNA analysis was performed with a quantitative NASBA for 18S rRNA and Leishmania DNA assessment with an RT-PCR for 18S rDNA. Findings suggested that a newly developed L3™ buffer proved to be reliable and suitable for both short- and long-term preservation of parasite nucleic acid material. This buffer is envisaged to be suitable for utilization in field situations where resources are limited.

Diagnostic accuracy of the Leishmania OligoC-TesT and NASBA-Oligochromatography for diagnosis of leishmaniasis in Sudan

BACKGROUND

The Leishmania OligoC-TesT and NASBA-Oligochromatography (OC) were recently developed for simplified and standardised molecular detection of Leishmania parasites in clinical specimens. We here present the phase II evaluation of both tests for diagnosis of visceral leishmaniasis (VL), cutaneous leishmaniasis (CL) and post kala-azar dermal leishmaniasis (PKDL) in Sudan.

METHODOLOGY

The diagnostic accuracy of the tests was evaluated on 90 confirmed and 90 suspected VL cases, 7 confirmed and 8 suspected CL cases, 2 confirmed PKDL cases and 50 healthy endemic controls from Gedarif state and Khartoum state in Sudan.

PRINCIPAL FINDINGS

The OligoC-TesT as well as the NASBA-OC showed a sensitivity of 96.8% (95% CI: 83.8%-99.4%) on lymph node aspirates and of 96.2% (95% CI: 89.4%-98.7%) on blood from the confirmed VL cases. The sensitivity on bone marrow was 96.9% (95% CI: 89.3%-99.1%) and 95.3% (95% CI: 87.1%-98.4%) for the OligoC-TesT and NASBA-OC, respectively. All confirmed CL and PKDL cases were positive with both tests. On the suspected VL cases, we observed a positive OligoC-TesT and NASBA-OC result in 37.1% (95% CI: 23.2%-53.7%) and 34.3% (95% CI: 20.8%-50.9%) on lymph, in 72.7% (95% CI: 55.8%-84.9%) and 63.6% (95% CI: 46.6%-77.8%) on bone marrow and in 76.9% (95% CI: 49.7%-91.8%) and 69.2% (95% CI: 42.4%-87.3%) on blood. Seven out of 8 CL suspected cases were positive with both tests. The specificity on the healthy endemic controls was 90% (95% CI: 78.6%-95.7%) for the OligoC-TesT and 100% (95% CI: 92.9%-100.0%) for the NASBA-OC test.

CONCLUSIONS

Both tests showed high sensitivity on lymph, blood and tissue scrapings for diagnosis of VL, CL and PKDL in Sudan, but the specificity for clinical VL was significantly higher with NASBA-OC.

Phase II evaluation of sensitivity and specificity of PCR and NASBA followed by oligochromatography for diagnosis of human African trypanosomiasis in clinical samples from D.R. Congo and Uganda

Background

The polymerase chain reaction (PCR) and nucleic acid sequence-based amplification (NASBA) have been recently modified by coupling to oligochromatography (OC) for easy and fast visualisation of products. In this study we evaluate the sensitivity and specificity of the PCR-OC and NASBA-OC for diagnosis of Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense human African trypanosomiasis (HAT).

Methodology and Results

Both tests were evaluated in a case-control design on 143 HAT patients and 187 endemic controls from the Democratic Republic of Congo (DRC) and Uganda. The overall sensitivity of PCR-OC was 81.8% and the specificity was 96.8%. The PCR-OC showed a sensitivity and specificity of 82.4% and 99.2% on the specimens from DRC and 81.3% and 92.3% on those from Uganda. NASBA-OC yielded an overall sensitivity of 90.2%, and a specificity of 98.9%. The sensitivity and specificity of NASBA-OC on the specimens from DRC was 97.1% and 99.2%, respectively. On the specimens from Uganda we observed a sensitivity of 84.0% and a specificity of 98.5%.

Conclusions/Significance

The tests showed good sensitivity and specificity for the T. b. gambiense HAT in DRC but rather a low sensitivity for T. b. rhodesiense HAT in Uganda.

Diagnosis plays a central role in the control of human African trypanosomiasis (HAT) whose mainstay in disease control is chemotherapy. However, accurate diagnosis is hampered by the absence of sensitive techniques for parasite detection. Without concentrating the blood, detection thresholds can be as high as 10,000 trypanosomes per milliliter of blood. The polymerase chain reaction (PCR) and nucleic acid sequence-based amplification (NASBA) are promising molecular diagnostics that generally yield high sensitivity and could improve case detection. Recently, these two tests were coupled to oligochromatography (OC) for simplified and standardized detection of amplified products, eliminating the need for electrophoresis. In this study, we evaluated the diagnostic accuracy of these two novel tests on blood specimens from HAT patients and healthy endemic controls from D.R. Congo and Uganda. Both tests exhibited good sensitivity and specificity compared to the current diagnostic tests and may be valuable tools for sensitive and specific parasite detection in clinical specimens. These standardized molecular test formats open avenues for improved case detection, particularly in epidemiological studies and in disease diagnosis at reference centres.

Accordance and concordance of PCR and NASBA followed by oligochromatography for the molecular diagnosis of Trypanosoma brucei and Leishmania

OBJECTIVE

To evaluate the repeatability and reproducibility of four simplified molecular assays for the diagnosis of Trypanosoma brucei spp. or Leishmania ssp. in a multicentre ring trial with seven participating laboratories.

METHODS

The tests are based on PCR or NASBA amplification of the parasites nucleic acids followed by rapid read-out by oligochromatographic dipstick (PCR-OC and NASBA-OC).

RESULTS

On purified nucleic acid specimens, the repeatability and reproducibility of the tests were Tryp-PRC-OC, 91.7% and 95.5%; Tryp-NASBA-OC, 95.8% and 100%; Leish-PCR-OC, 95.9% and 98.1%; Leish-NASBA-OC, 92.3% and 98.2%. On blood specimens spiked with parasites, the repeatability and reproducibility of the tests were Tryp-PRC-OC, 78.4% and 86.6%; Tryp-NASBA-OC, 81.5% and 89.0%; Leish-PCR-OC, 87.1% and 91.7%; Leish-NASBA-OC, 74.8% and 86.2%.

CONCLUSION

As repeatability and reproducibility of the tests were satisfactory, further phase II and III evaluations in clinical and population specimens from disease endemic countries are justified.

Sensitivity and specificity of the Leishmania OligoC-TesT and NASBA-oligochromatography for diagnosis of visceral leishmaniasis in Kenya

OBJECTIVE

To estimate the sensitivity and specificity of the OligoC-TesT and nucleic acid sequence-based amplification coupled to oligochromatography (NASBA-OC) for molecular detection of Leishmania in blood from patients with confirmed visceral leishmaniasis (VL) and healthy endemic controls from Kenya.

METHODS

Blood specimens of 84 patients with confirmed VL and 98 endemic healthy controls from Baringo district in Kenya were submitted to both assays.

RESULTS

The Leishmania OligoC-TesT showed a sensitivity of 96.4% (95% confidence interval [CI]: 90-98.8%) and a specificity of 88.8% (95% CI: 81-93.6%), while the sensitivity and specificity of the NASBA-OC were 79.8% (95% CI: 67-87%) and 100% (95% CI: 96.3-100%), respectively.

CONCLUSION

Our findings indicate high sensitivity of the Leishmania OligoC-TesT on blood while the NASBA-OC is a better marker for active disease.

Development of a reverse transcriptase loop-mediated isothermal amplification (LAMP) assay for the sensitive detection of Leishmania parasites in clinical samples

Here we describe a generic, reverse transcriptase-loop-mediated isothermal amplification (RT-LAMP) assay, for the identification of Leishmania species from clinical samples. LAMP is an isothermal reaction recently developed as a point-of-care diagnostic tool. Primers were designed in the conserved region of the 18S ribosomal RNA (rRNA) gene; amplification was visualized by the pre-amplification addition of fluorescent detection reagent (FDR) and a simple UV lamp. By using a reverse-transcriptase step, the system detected infections between 10 and 100 parasites per mL. The assay was tested on a range of nucleic acid extracts from Leishmania species, visceral leishmaniasis (VL) patients from Sudan, and cutaneous leishmaniasis (CL) patients from Suriname. The sensitivity of RT-LAMP from the blood of VL patients was 83% (N = 30) compared with microscopy of bone-marrow and lymph-node aspirates; for CL patients the observed sensitivity was 98% (N = 43). The potential to use LAMP as a diagnostic tool for leishmaniasis is discussed.

Simplified molecular detection of Leishmania parasites in various clinical samples from patients with leishmaniasis

Background

Molecular methods to detect Leishmania parasites are considered specific and sensitive, but often not applied in endemic areas of developing countries due to technical complexity. In the present study isothermal, nucleic acid sequence based amplification (NASBA) was coupled to oligochromatography (OC) to develop a simplified detection method for the diagnosis of leishmaniasis. NASBA-OC, detecting Leishmania RNA, was evaluated using clinical samples from visceral leishmaniasis patients from East Africa (n = 30) and cutaneous leishmaniasis from South America (n = 70) and appropriate control samples.

Results

Analytical sensitivity was 10 parasites/ml of spiked blood, and 1 parasite/ml of culture. Diagnostic sensitivity of NASBA-OC was 93.3% (95% CI: 76.5%-98.8%) and specificity was 100% (95% CI: 91.1%-100%) on blood samples, while sensitivity and specificity on skin biopsy samples was 98.6% (95% CI: 91.2%-99.9%) and 100% (95% CI: 46.3%-100%), respectively.

Conclusion

The NASBA-OC format brings implementation of molecular diagnosis of leishmaniasis in resource poor countries one step closer.

Didelphis marsupialis (common opossum): a potential reservoir host for zoonotic leishmaniasis in the metropolitan region of Belo Horizonte (Minas Gerais, Brazil)

Identification of the zoonotic reservoir is important for leishmaniasis control program. A number of (wild) animal species may serve as reservoir hosts, including the opossum Didelphis marsupialis. A survey carried out in Didelphis specimens (n = 111) from the metropolitan region of Belo Horizonte, an important focus of human leishmaniasis in Brazil, is reported. All animals were serologically tested with indirect fluorescence antibody test (IFAT) and direct agglutination tests (DAT) based on L. (L.) donovani or L. (V.) braziliensis antigen. A sub-population (n = 20) was analyzed with polymerase chain reaction (PCR) for the presence of Leishmania-specific DNA. For species identification, PCR-positive samples were subjected to restriction enzyme fragment polymorphism (RFLP) analysis. Depending on the sero-diagnostic test employed, the sero-prevalence varied between 8.1% (9/111 animals positive with DAT test based on L. braziliensis antigen) and 21.6% (24/111 animals positive with IFAT). Five out of 20 samples analyzed with PCR tested positive for the presence of Leishmania-specific DNA. RFLP analysis revealed that two samples contained L. braziliensis complex DNA, one contained L. donovani complex DNA, and two samples could not be typed with the methodology used. These data suggest a potential role for the opossum as a reservoir host for zoonotic leishmaniasis in the region.

Diagnosis of canine leishmaniasis in the endemic area of Belo Horizonte, Minas Gerais, Brazil by parasite, antibody and DNA detection assays

Canine leishmaniasis caused by Leishmania chagasi (L. infantum) is found throughout the South American continent, including Brazil, and dogs are considered to be the main reservoir host for this parasite. To support the implementation of a diagnostic protocol for surveillance of the disease in the region of Belo Horizonte (Minas Gerais, Brazil) we have compared the sensitivity and specificity of two serological tests, indirect immunofluorescent antibody test (IFAT) and direct agglutination test (DAT), with the combination of direct microscopy-culture-PCR as the gold standard, using samples obtained from 103 dogs in the city of Belo Horizonte, Minas Gerais. The currently used standard serodiagnostic test, IFAT, had a sensitivity of 100% and its specificity was 74% compared to the gold standard of the study. The sensitivity and specificity of the DAT were 100% and 91%, respectively. On the basis of this study it is recommended to change from the IFAT to DAT for the serodiagnosis of canine leishmaniasis because of the superior specificity of the test combined with its user-friendliness.

Detection and identification of human Plasmodium species with real-time quantitative nucleic acid sequence-based amplification

Background

Decisions concerning malaria treatment depend on species identification causing disease. Microscopy is most frequently used, but at low parasitaemia (<20 parasites/μl) the technique becomes less sensitive and time consuming. Rapid diagnostic tests based on Plasmodium antigen detection do often not allow for species discrimination as microscopy does, but also become insensitive at <100 parasites/μl.

Methods

This paper reports the development of a sensitive and specific real-time Quantitative Nucleic Acid Sequence Based Amplification (real-time QT-NASBA) assays, based on the small-subunit 18S rRNA gene, to identify the four human Plasmodium species.

Results

The lower detection limit of the assay is 100 – 1000 molecules in vitro RNA for all species, which corresponds to 0.01 – 0.1 parasite per diagnostic sample (i.e. 50 μl of processed blood). The real-time QT-NASBA was further evaluated using 79 clinical samples from malaria patients: i.e. 11 Plasmodium. falciparum, 37 Plasmodium vivax, seven Plasmodium malariae, four Plasmodium ovale and 20 mixed infections. The initial diagnosis of 69 out of the 79 samples was confirmed with the developed real-time QT-NASBA. Re-analysis of seven available original slides resolved five mismatches. Three of those were initially identified as P. malariae mono-infection, but after re-reading the slides P. falciparum was found, confirming the real-time QT-NASBA result. The other two slides were of poor quality not allowing true species identification. The remaining five discordant results could not be explained by microscopy, but may be due to extreme low numbers of parasites present in the samples. In addition, 12 Plasmodium berghei isolates from mice and 20 blood samples from healthy donors did not show any reaction in the assay.

Conclusion

Real-time QT-NASBA is a very sensitive and specific technique with a detection limit of 0.1 Plasmodium parasite per diagnostic sample (50 μl of blood) and can be used for the detection, identification and quantitative measurement of low parasitaemia of Plasmodium species, thus making it an effective tool for diagnostic purposes and useful for epidemiological and drug studies.

Field evaluation of a fast anti-Leishmania antibody detection assay in Ethiopia

A fast agglutination screening test (FAST) for the detection of Leishmania antibodies in human serum samples was evaluated under harsh field conditions in northern Ethiopia. Test performance was compared with a standard serological test, namely the direct agglutination test (DAT), and with parasitology. In total, 103 suspected cases were recruited for the study. Based on parasitological examination, 49 patients were confirmed of having visceral leishmaniasis (VL) and the other 54 suspected cases were parasitologically negative. Field evaluation of FAST was possible in blood samples of 89 patients. FAST had 4 false negative results and 13 false positive results. DAT had 2 false negative results and 20 false positive results. A good degree of agreement (86.9%) was observed between FAST and DAT (kappa value 0.73). In this field-based evalauation, the sensitivity and specificity of FAST were found to be 91.1% (95% CI 77.9-97.1) and 70.5% (95% CI 54.6-82.8), respectively, compared with 95.3% (95% CI 82.9-99.2) and 62.3% (95% CI 47.9-74.9) for DAT. FAST had a high predictive value of a negative test, demonstrating that FAST could be utilised to exclude rapidly non-VL patients from a large population of suspects with fever and splenomegaly in endemic areas.

Quantitative nucleic acid sequence-based assay as a new molecular tool for detection and quantification of Leishmania parasites in skin biopsy samples

Currently available methods for the diagnosis of cutaneous leishmaniasis (CL) have low sensitivities or are unable to quantify the number of viable parasites. This constitutes a major obstacle for the diagnosis of the disease and for the study of the effectiveness of treatment schedules and urges the development of improved detection methods. In this study, quantitative nucleic acid sequence-based amplification (QT-NASBA) technology was used to detect and quantify Leishmania parasites in skin biopsy samples from CL patients. The assay is based on the detection of a small subunit rRNA (18S rRNA), which may allow for the detection of viable parasites. The QT-NASBA assay was evaluated using in vitro-cultured promastigotes and amastigotes and 2-mm skin biopsy samples from Old and New World CL patients. The study demonstrated that the lower detection limit of the QT-NASBA was two parasites per biopsy sample. Parasites could be quantified in a range of 2 to 11,300,000 parasites per biopsy sample. The QT-NASBA could detect levels of parasites 100-fold lower than those detected by conventional PCR. Test evaluation revealed that the QT-NASBA had a sensitivity of 97.5% and a specificity of 100% in the present study. The QT-NASBA is a highly sensitive and specific method that allows quantification of both Old and New World Leishmania parasites in skin biopsy samples and may provide an important tool for diagnosis as well as for monitoring the therapy of CL patients.

Application of direct agglutination test (DAT) and fast agglutination screening test (FAST) for sero-diagnosis of visceral leishmaniasis in endemic area of Minas Gerais, Brazil

Background

The direct agglutination test (DAT) has proved to be a very important sero-diagnostic tool combining high levels of intrinsic validity and ease of performance. Otherwise, fast agglutination screening test (FAST) utilises only one serum dilution making the test very suitable for the screening of large populations.

Results

We have tested FAST and DAT for the detection anti-Leishmania antibodies in serum samples from patients with American visceral (AVL) and cutaneous leishmaniases (ACL) in Minas Gerais State, Brazil. The DAT on serum and blood samples of confirmed AVL patients found all samples positive at a serum dilution of ≥ 1:800. This dilution was subsequently used as cut off value in the study. The blood and serum samples of these confirmed patients could also be clearly read in FAST using a 1:100 dilution with the same high sensitivity. DAT and FAST were not able to detect significant amounts of antibodies in samples from ACL patients and are not suitable for the diagnosis of this manifestation of the disease.

Conclusion

We suggest that both DAT and FAST are very practical diagnostic tools for the sero-diagnosis of AVL under rural conditions as both serological tests do not require sophisticated equipment, a cold chain and are very simple to perform.

Plasmodium falciparum: evaluation of a quantitative nucleic acid sequence-based amplification assay to predict the outcome of sulfadoxine-pyrimethamine treatment of uncomplicated malaria

A quantitative nucleic acid sequence-based amplification (QT-NASBA) assay was employed to predict retrospectively the outcome of sulfadoxine-pyrimethamine (SP) treatment of uncomplicated malaria in children aged <6 years in an endemic region. Blood samples were collected at initial diagnosis and during follow-up. Mutation-specific nested PCR methods to analyse DHFR (Arg-59) and DHPS (Glu-540) mutations that are associated with SP drug resistance were applied. Parasite genotyping was performed to distinguish between re-infection and recrudescence. Eighty-six patients were recruited of which 66 were available for follow-up. Nine children were classified as early treatment failure, 13 cases were classified as late clinical failure, 32 as late parasitological failure, and only 12 children had an adequate clinical and parasitological response. DHFR and DHPS mutations conferring SP resistance were abundant in the Plasmodium population. Blood samples obtained 7 days after treatment were used to predict retrospectively the outcome of SP treatment. QT-NASBA was able to give a correct prediction of treatment outcome in 85.7% of the cases. Positive predictive value (PPV) of QT-NASBA case was 95% (95% confidence interval = 88.3-100) and negative predictive value (NPV) was 63% (95% CI = 39.5-86.5). In contrast, microscopy correctly predicted outcome in only 37.5% of the cases. PPV of microscopy was 100% (95% CI = 73.9-100) and the NPV was 25.5% (95% CI = 13.0-38.0). The analysis of a day 7 blood sample with QT-NASBA allows for the prediction of late clinical or parasitological treatment failure in the majority of the cases analysed in the present study.

Sero-epidemiological study of canine Leishmania spp. infection in the municipality of Alijó (Alto Douro, Portugal)

Visceral leishmaniosis caused by Leishmania infantum is a zoonotic disease in the Mediterranean basin. We report an epidemiological survey carried out in dogs from the municipality of Alijó in the endemic region of Alto Douro (north Portugal). Performance of the direct agglutination test (DAT) was assessed in 205 matching samples of blood collected on filter paper and serum. A high degree of agreement (97.6%; k = 0.83) was found between the results obtained from both types of samples. DAT was then used to test more blood on filter paper (B-FP) samples from other dogs of the same municipality. The detected sero-prevalence was 18.7% (288/1540), with values ranging from 0.0 to 81.1% in each of the 19 parishes of Alijó. Three distinct geographical zones of mean sero-prevalence could be defined: northwestern (2.5%), intermediate (11.4%) and southern (49.9%). No statistically significant difference was observed between male (19.1%) and female (17.8%) sero-prevalences (P = 0.560). Dogs of 9-11 years of age showed the highest sero-prevalence (28.4%), but all the other age-intervals (0-2, 3-5, 6-8 and 12-17 years) presented values (15.0-22.3%) not significantly different from the mean of the whole study population. Risk factors for canine Leishmania infection were age and geographical zone. Only 5.9% of the sero-positive animals had clinical signs of canine leishmaniosis and the overall prevalence of disease was 1.1%. This study validates the use of B-FP samples and confirms DAT as a simple and sensitive serological test to evaluate the level of canine Leishmania infection in areas of high sero-prevalence.

Usefulness of quantitative nucleic Acid sequence-based amplification for diagnosis of malaria in an academic hospital setting

The aim of the present study was to evaluate the usefulness of quantitative nucleic acid sequence-based amplification (QT-NASBA) to detect Plasmodium spp. in diagnostic specimens of patients suspected of having malaria in a clinical setting in a non-endemic country. During the 4-month recruitment period, 113 patients were enrolled in the study, of which 93 were diagnosed as non-malaria and 20 as malaria cases on the basis of clinical and microscopic criteria. All microscopically positive cases had QT-NASBA counts of >0.1 parasites/ micro l and there was a significant positive correlation between the parasite counts obtained with both diagnostic methods. Of the 93 microscopically negative cases, six had a positive QT-NASBA result. Three of these cases had a recent history of malaria for which specific treatment was taken. In the other three cases there was no history of malaria and QT-NASBA results in these cases were near the cut-off level (>0.1 parasites/ micro l) of the test. The results demonstrate that QT-NASBA is a useful technology for the diagnosis of malaria in a reference laboratory, and it is very helpful in cases of low parasitemia.

Development of a fast agglutination screening test (FAST) for the detection of anti-Leishmania antibodies in dogs

A fast agglutination screening test (FAST) for the detection of anti-Leishmania antibodies in serum samples from dogs with visceral leishmaniosis was developed. The test is based on the direct agglutination test (DAT), but combines a higher parasite concentration with a smaller test volume. In contrast to the DAT, the FAST makes use of only one serum dilution and the results can be read within 3 h as opposed to 18-20 h for the DAT. The FAST was evaluated using serum samples of confirmed cases of the disease and healthy controls collected in the most important endemic regions of canine visceral leishmaniosis, import cases of canine leishmaniosis in a non-endemic country, from non-endemic healthy controls and from dogs with other diseases. The performance of the FAST was compared with standard DAT. In the present study, the FAST had a sensitivity of 93.6% and a specificity of 89.0%. The DAT had a sensitivity of 88.6% and a specificity of 96.7%. Furthermore, using a large panel of serum samples of previously examined DAT positive or negative dogs it was shown that degree of agreement between the two tests was high (95.7%; kappa value = 0.91). The FAST offers the advantages of the DAT based on freeze-dried antigen with respect to stability of the antigen, sensitivity and specificity. Moreover, the FAST allows the rapid screening of a large number of samples, which makes the test very useful for epidemiological screening of large populations of dogs.

Sero-epidemiological assessment and diagnosis of visceral leishmaniasis in an endemic locality using Fast Agglutination Screening Test (FAST)

The Fast Agglutination Screening Test (FAST) was employed on sera obtained from an endemic area of visceral leishmaniasis in southwestern Ethiopia, in February 2000. The study involved (i) active case detection among 1575 residents of two villages; and (ii) passive case detection in an outpatient clinic. Sera of 1587 individuals, including 143 sera of previously treated VL patients, were tested. Based on the size of agglutination mat, the FAST results were read qualitatively as non-reactive (-), weakly reactive (1+), moderately reactive (2+) and highly reactive (3+). All FAST reactive sera were re-tested with the Direct Agglutination Test (DAT). After clinical screening of 1625 individuals, 61 individuals with signs and symptoms of early or late VL were found; 26 sera were FAST positive. Twenty-two of these suspected VL cases were subjected to parasitological examination using lymph node aspirates. Eighteen (81.8%) were confirmed either by demonstration of amastigotes in smears or promastigotes in NNN cultures. FAST reactive anti-leishmanial antibodies were detected in 4.5% of untreated and 70.6% of previously treated patients. Forty-five sera of 1390 previously untreated asymptomatic individuals (3.2%) were found to be FAST positive. This report demonstrates that FAST is a rapid and cost-effective screening test for the diagnosis and sero-epidemiological surveillance of visceral leishmaniasis.

Development and application of 'simple' diagnostic tools for visceral leishmaniasis

The diagnosis of visceral leishmaniasis is difficult. Due to the limitations of direct methods to detect parasites, indirect immunological methods are widely employed. The simple affordable and sensitive/specific direct agglutination test (DAT) is perhaps the most important diagnostic tool under field conditions. A significant improvement of this test is the use of a freeze-dried antigen, which is heat-stable and has a long shelf-live even under harsh conditions. The performance of this antigen in DAT has been evaluated using samples collected in East Africa. The results of these studies are presented. The detection of Leishmania infection in HIV-co-infected patients is difficult. The combination of DAT-PCR may be useful for the detection of parasite infection in these patients. Finally, we present data to show that the DAT based on the freeze-dried antigen can also be used for the detection of anti-Leishmania antibodies in dogs.

Detection and quantification of Plasmodium falciparum in blood samples using quantitative nucleic acid sequence-based amplification

A quantitative nucleic acid sequence-based amplification (QT-NASBA) assay for the detection of Plasmodium parasites has been developed. Primers and probes were selected on the basis of the sequence of the small-subunit rRNA gene. Quantification was achieved by coamplification of the RNA in the sample with one modified in vitro RNA as a competitor in a single-tube NASBA reaction. Parasite densities ranging from 10 to 10(8) Plasmodium falciparum parasites per ml could be demonstrated and quantified in whole blood. This is approximately 1,000 times more sensitive than conventional microscopy analysis of thick blood smears. Comparison of the parasite densities obtained by microscopy and QT-NASBA with 120 blood samples from Kenyan patients with clinical malaria revealed that for 112 of 120 (93%) of the samples results were within a 1-log difference. QT-NASBA may be especially useful for the detection of low parasite levels in patients with early-stage malaria and for the monitoring of the efficacy of drug treatment.

Use of PCR for diagnosis of post-kala-azar dermal leishmaniasis

Microscopy and PCR were compared for use in the diagnosis of post-kala-azar dermal leishmaniasis (PKDL) in 63 patients. Aspirates of lymph nodes (samples from 52 patients), skin (23 samples), and bone marrow (18 samples) were used. For 11 patients lymph node aspiration could be repeated 6 months after they recovered from PKDL. During active PKDL, PCR was positive for 42 of 52 (80.8%) lymph node aspirates and 19 of 23 (82.7%) skin aspirates, whereas microscopy was positive for only 9 of 52 (17.3%) lymph node aspirates and 7 of 23 (30.4%) skin aspirates. PCR was always positive when parasites were seen by microscopy. When the results obtained with lymph node and skin aspirates from the same patient (n = 16) were compared, there was complete agreement. Bone marrow samples were negative by microscopy and PCR for 16 patients and positive by both methods for 1 patient; for one sample only the PCR was positive. PCR confirmed the co-occurrence of visceral leishmaniasis and PKDL in one patient and confirmed the suspicion of this co-occurrence in the other patient. After recovery, no parasites were found by microscopy, but 2 of 11 (18.2%) samples were still positive by PCR. Thirty negative controls were all found to be PCR negative, and 15 positive controls were all PCR positive. Cross-reactions with Mycobacterium leprae could be ruled out. In conclusion, PCR with inguinal lymph node or skin aspirates is suitable for confirming the clinical diagnosis of PKDL. In some patients, lymph node aspirates are probably preferred because aspiration of material from the skin may leave scars.

Detection of Onchocerca volvulus DNA in pools of wild-caught Simulium ochraceum by use of the polymerase chain reaction

The presence of Onchocerca volvulus DNA in experimentally infected flies can now be detected by use of the PCR, so that, for example, one infected Simulium damnosum can be detected in a pool of 100 uninfected flies or one S. ochraceum can be detected in pools of 20-40. As this PCR technique is specific for O. volvulus, the results are not confounded by the presence of other, unimportant, Onchocerca species, and the technique could replace time-consuming, manual dissection of flies. In 1996 and 1997, pools of 16-21 Simulium ochraceum were tested by the PCR technique. These flies had been collected biting man, between 1992 and 1994, from two hyperendemic coffee estates (fincas) in Guatemala, and stored in commercial (95%) ethanol. Collections at finca Buena Vista (869 flies in 52 pools) were made 1-2 weeks and 46 weeks after 45% of eligible subjects had been treated with ivermectin for the first time. At finca El Brote, collections (360 flies in 18 pools) were made 13 weeks before and 7 weeks after 97% of eligible subjects had received their first treatment. DNA was easily recovered from simuliids that had been stored in ethanol for up to 4 years. Of the nine pools of flies with visible blood collected at Buena Vista, each of 20 flies, eight tested positive for O. volvulus DNA. In flies without blood, 13 of 22 pools collected at Buena Vista just after treatment tested positive, whereas there were 14 positives in 22 pools taken 46 weeks later (P > 0.05). At El Brote, nine of 10 pre-treatment pools were positive, compared with three of eight taken 7 weeks post-treatment (P = 0.04), indicating that the treatments in this finca had reduced infection in the vector, and possibly transmission, by about 60%. A sub-sample of Buena Vista flies was divided into 19 sets of three separate sub-pools containing heads, thoraces and abdomens. Three pools of heads alone were positive, and had corresponding pools of positive abdomens. Three positive pools of thoraces had negative corresponding pools of heads and abdomens. These results show that PCR can be used to determine the prevalence of O. volvulus DNA in wild-caught S. ochraceum. As the infection rates observed were higher than expected from dissections reported by other workers, PCR-determined rates may not be directly comparable with traditional parameters based on the dissection of flies to reveal O. volvulus larvae.

Evaluation of PCR for diagnosis of visceral leishmaniasis

An evaluation of Leishmania PCR was performed with bone marrow, lymph node, and blood samples from 492 patients, 60 positive controls, and 90 negative controls. Results were compared with microscopy results for Giemsa-stained smears. PCR and microscopy of lymph node and bone marrow aspirates from patients with microscopically confirmed visceral leishmaniasis (VL) were equally sensitive. However, in patients clinically suspected of having VL and in whom parasites could not be demonstrated by microscopy, PCR was positive for 12 of 23 (52.2%) lymph node aspirates and 8 of 12 (66.7%) bone marrow aspirates, thus confirming the clinical diagnosis of VL. With PCR on filter paper, Leishmania DNA was detected in the blood of 33 of 47 (70%) patients with confirmed VL and in 2 of 11 (19%) patients suspected of having VL. Positive PCR results were more frequently found for blood samples on filter paper than for samples stored in EDTA. In conclusion, PCR is a more sensitive method than microscopy for the detection of Leishmania in lymph node and bone marrow aspirates, being especially useful for the confirmation of cases of suspected VL. Blood from a finger prick may be used for the initial PCR screening of people suspected of having VL. If the PCR of blood is negative, one should perform PCR with lymph node and/or bone marrow material, because PCR with these materials is more often positive.

Polymerase chain reaction for detecting Onchocerca volvulus in pools of blackflies

The detection of Onchocerca volvulus infected simuliids or blackflies is routinely done by dissection and microscopic examination of individual flies, but this method is tedious and time consuming. Here we describe a method of detecting single O. volvulus infected blackflies in pools of uninfected blackflies. Using a PCR with Onchocerca specific primers it is possible to reproducibly detect one heavily infected blackfly in a pool of 80 flies, or to detect one blackfly inoculated with one microfilaria in a pool of 20 flies. With the method described large numbers of blackflies can be rapidly screened for the presence of O. volvulus infected flies.

Sudanese mucosal leishmaniasis: epidemiology, clinical features, diagnosis, immune responses and treatment

The epidemiology, clinical features, pathology, immune responses, diagnosis and treatment of 14 patients with mucosal leishmaniasis in the Sudan are described. The condition occurred mainly in adult males, particularly in certain closely related tribes from the western Sudan. It affected the mucosa of the upper respiratory tract and/or the oral mucosa and sometimes followed treated kala azar. The parasites were sometimes confined to the mucosa, sometimes spread to the lymph nodes, and rarely infected the bone marrow and spleen. One of the 2 patients with both visceral and mucosal leishmaniasis differed from classical kala azar cases; his infection was longer lasting, he was leishmanin positive, and his peripheral mononuclear cells proliferated in response to leishmanial antigens. Mucosal leishmaniasis following treated kala azar is a similar phenomenon to post-kala azar dermal leishmaniasis and post-kala azar uveitis. Post-kala azar mucosal leishmaniasis can therefore be added to the other post-kala azar leishmanial infections. Using the polymerase chain reaction, Southern blot analysis with specific probes, and isoenzyme characterization, the causative parasite was identified as Leishmania donovani in 4 patients and as L. major in one. Unlike American mucocutaneous leishmaniasis, mucosal leishmaniasis in the Sudan was not preceded or accompanied by cutaneous lesions and the response to pentavalent antimony or ketoconazole was good.

Visceral leishmaniasis: use of the polymerase chain reaction in an epidemiological study in Baringo District, Kenya

The polymerase chain reaction was applied to capillary blood spots dried on filter paper from 20 parasitologically proved cases of visceral leishmaniasis (VL), 21 subclinical cases, and 11 healthy controls in a longitudinal study of anthroponotic VL in Baringo District, Kenya. Leishmania deoxyribonucleic acid (DNA) was detected 10.5 months before diagnosis and up to 3 years after diagnosis and apparently successful treatment. Subclinical cases can have detectable circulating parasite DNA in their blood. These findings may indicate that subclinical cases can be a reservoir and formerly treated VL patients can remain a reservoir for a long time. Xenodiagnosis should be performed on subclinical cases and former VL patients to establish their role in transmission of VL in Kenya.

Leish-KIT, a stable direct agglutination test based on freeze-dried antigen for serodiagnosis of visceral leishmaniasis

In order to increase the application potential of the direct agglutination test (DAT) for the detection of anti-Leishmania antibodies in human serum samples, we developed an antigen based on stained and freeze-dried Leishmania donovani promastigotes. We describe here the evaluation of the performance of the DAT based on this freeze-dried antigen. It was shown that the freeze-dried antigen remains fully active, even after storage at 56 degrees C for 18 months. With a cutoff value of 1:1,600, the sensitivity of the DAT was shown to be 92% and the specificity of the test was 99.7%, which were comparable with the results found for the DAT based on liquid antigen. The major advantages of the freeze-dried antigen are that the production of a large batch of this antigen allows reproducible results in the DAT over a long period of time and that the freeze-dried antigen can be stored at ambient temperature, which, as was shown, makes the test a valuable diagnostic tool for use in the field.

Detection of seven species of pathogenic leptospires by PCR using two sets of primers

Two sets of primers derived from genomic DNA libraries of Leptospira serovars icterohaemorrhagiae (strain RGA) and bim (strain 1051) enabled the amplification by PCR of target DNA fragments from leptospiral reference strains belonging to all presently described pathogenic Leptospira species. The icterohaemorrhagiae-derived primers (G1/G2) enabled amplification of DNA from L. interrogans, L. borgpetersenii, L. weilii, L. noguchii, L. santarosai and L. meyeri, whereas the bim-derived primers (B64-I/B64-II) enabled the amplification of L. kirschneri. Southern blot and DNA sequence analysis revealed inter-species DNA polymorphism within the region spanned by primers G1 and G2 between L. interrogans and various other Leptospira species. Using a mixture of primer sets G1/G2 and B64-I/B64-II, leptospires of serovars icterohaemorrhagiae, copenhageni, hardjo, pomona, grippotyphosa and bim were detected in serum samples collected from patients during the first 10 days after the onset of illness.

Development and application of the polymerase chain reaction for the detection and identification of Leishmania parasites in clinical material

Detection, diagnosis and identification of Leishmaniasis may be difficult owing to low numbers of parasites present in clinical samples. The PCR has improved the sensitivity and specificity of diagnosis of several infectious diseases. A leishmania specific PCR assay was developed based on the SSUrRNA genes which amplifies DNA of all Leishmania species. Point mutations occurring within the rRNA genes allow differentiation of the Leishmania complexes using primers constructed with the 3/ ends complementary to the specific point mutations present in the SSU rRNA genes of the Leishmania species. Biopsy material, blood, lesion impressions and blood spots on filter paper can be used in the assay. In a longitudinal study on the incidence rates of VL, subclinical cases and PKDL in an endemic region of Sudan, filter paper blood spots from proven and suspected VL patients, PKDL and control samples from an endemic region in Sudan are being taken. The blood spots were analyzed in the DAT and by PCR and results compared with clinical and parasitological data. The first results indicate that the PCR on blood spots is a simple and sensitive means of detecting active VL; in PKDL patients parasites are detectable in the skin.

Comparison of Giardia isolates from different laboratories by isoenzyme analysis and recombinant DNA probes

A total of 13 new Giardia isolates were established in axenic culture. All of the new isolates were obtained by excystation of Giardia cysts from the feces of patients in Dutch hospitals. These isolates were subjected to isoenzyme and DNA analysis together with isolates from Poland, Belgium, and various other parts of the world. Isoenzyme analysis revealed that nearly all of the newly established isolates exhibited unique zymodemes. Isolates obtained from individuals from Belgium and Poland, on the other hand, displayed single zymodemes. Genomic DNA libraries were constructed from isolates belonging to the latter two zymodemes; specific and common recombinant DNA clones were selected from these libraries. Differential screening revealed that the two isolates had only 80% of the clones in common. Restriction-fragment-length polymorphism analysis using three different probes together with two synthetic probes that are complementary to Giardia structural protein genes led to the separation of all isolates into two major groups; within these groups, a further division could be made by application of other techniques or probes. The results of DNA analysis and zymodeme classification were in general agreement; in the present report they are compared with the data in the literature and discussed.

Sequence analysis of small subunit ribosomal RNA genes and its use for detection and identification of Leishmania parasites

The sequence of the most variable part of the small subunit ribosomal RNA (SSU rRNA) gene, comprising 800 bases, was analysed for 9 Leishmania taxa and compared with those of Trypanosoma brucei, Trypanosoma cruzi and Crithidia fasciculata. Considerable differences were observed between the sequence of the Leishmania taxa on the one hand and those of Crithidia and Trypanosoma on the other. Amongst the Leishmania taxa only a few point mutations were found, all located within 2 sequence blocks in the central part of the SSU rRNA gene, which are unique for Kinetoplastida. These unique sequences were used for the development of kinetoplastid-specific probes and a Leishmania-specific PCR assay of high sensitivity (less than 10 parasites could be detected). Based on the observed point-mutations an identification of the Leishmania parasites, according to complex, could be achieved by direct sequencing, restriction fragment analysis or single-stranded conformation polymorphism of the PCR-generated fragments.

Detection and identification of Leishmania parasites by in situ hybridization with total and recombinant DNA probes

In situ hybridization on cultured promastigotes and sandfly smears were performed with nonradioactively labeled total DNA and recombinant DNA probes containing minicircle kinetoplast DNA (kDNA) or nuclear DNA inserts. Total DNA probes lack specificity whereas recombinant nuclear DNA probes work only if they contain repetitive sequences. Minicircle kDNAs of five Leishmania isolates, representative of five Leishmania taxa found in Kenya, were sequenced. Comparison of the sequences showed a 150-bp region with around 80% homology, whereas the rest of the minicircles had about 50% homology. Nevertheless, application of these probes in in situ hybridization assays as tested on Leishmania promastigotes in the vector gave good specificity and hybridization signal. Two types of labeling were tested: incorporation of biotin-labeled dUTP or directly horseradish peroxidase (HRP)-labeled nucleotides. Both techniques provided good sensitivity and signal-to-noise ratio on cultured promastigotes. Hybridization with HRP-labeled kDNA probes gave a superior signal-to-noise ratio if tested on sandfly preparations. This method provided a reliable and fast identification and facilitated the detection of promastigotes in sandflies. The technique presented here may be helpful in rapid identification of Leishmania promastigotes, and thus make epidemiological studies easier and less time consuming.

Characterization of serovars of the genus Leptospira by DNA hybridization with hardjobovis and icterohaemorrhagiae recombinant probes with special attention to serogroup sejroe

Recombinant DNA probes derived from genomic libraries of serovars hardjobovis and icterohaemorrhagiae were applied for the characterization of leptospires. Differences in hybridization signals in combination with the banding pattern appear to provide good characteristics for strain typing. The banding patterns were easy to distinguish, since the recombinant DNA probes hybridized with a limited number of fragments. They were also indicative of genomic relationships between serovars. The probes suggested the existence of four subgroups with extensive genomic homology within the serogroup Sejroe. A number of serovars outside the serogroup Sejroe showed genomic homology with these subgroups. Amplification with the polymerase chain reaction showed a correlation with the genomic homologies demonstrated by Southern analysis. Knowledge about genomic relationships between leptospiral strains, as revealed by Southern analysis, may lead to a more rational approach for primer selection for polymerase chain reaction or cloning of particular genes.

Mucocutaneous leishmaniasis due to Leishmania (Leishmania) infantum: biochemical characterization

A vegetative mass in the right nasal cavity of a 62-year-old man from Palma de Mallorca, Spain, was found to be due to Leishmania. The organism was isolated in culture and characterized by in situ hybridization, Southern blot hybridization, and isoenzyme analysis; it was thus demonstrated to be the most common enzyme variant 1 (MON 1) of Leishmania (Leishmania) infantum.

Comparison of dot blot with in-situ hybridization for the detection of Neisseria gonorrhoeae in urethral exudate

Dot blot hybridization and in-situ hybridization with DNA probes prepared from total genomic gonococcal DNA were compared with Gram staining and culturing for the detection of gonococci in urethral exudates. Fifteen of 60 patients were positive by at least one of the four methods. Gram staining and in-situ hybridization scored best with 13 positives but culture and dot blot hybridization yielded only 10 and 9 positives respectively. The failure to detect gonococci in culture can be explained by overgrowth in one case and possibly self medication with ampicillin before culture in another. The in-situ hybridization test is a fast and sensitive hybridization method for the detection of gonococci in urethral exudate from men.

Identification of 'Old World' Leishmania by DNA recombinant probes

Leishmania are usually identified by iso-enzyme analysis. This method works well, but there is a need for an additional, more simple, method of identification. Here we present data that show that in a Southern blot analysis, recombinant DNA probes in combination with certain restriction enzymes can differentiate between taxa of Leishmania. Probes based on clones selected from a L. infantum cDNA library gave characteristic patterns on Southern blots for reference strains of the different types of Leishmania found in Europe, Africa and Asia. Within the different taxa little or no variation was observed. Although the L. infantum derived probes showed a somewhat stronger hybridization for strains of the L. donovani complex, the signal obtained with most probes was satisfactory for L. major, L. aethiopica and L. tropica. Within the L. donovani complex none of the selected probes differentiated between isolates belonging to L. infantum, L. chagasi or L. donovani. Probes containing kinetoplast DNA showed considerable variation in hybridization within a taxon.

An immunoprotective monoclonal antibody directed against Leptospira interrogans serovar copenhageni

A monoclonal antibody (mAb) was prepared by hybridoma technology in BALB/c mice immunized to Leptospira interrogans serovar copenhageni. This mAb agglutinated serovars copenhageni and icterohaemorrhagiae to high titres and protected hamsters, dogs and monkeys against challenge with a virulent strain of serovar copenhageni. The mAb gave protection to hamsters at dilutions up to 1 in 1000; at a 1 in 10 dilution the protective effect lasted for at least two weeks. Biochemical analysis by SDS-PAGE and Western blotting indicated that this mAb reacted with an epitope of a carbohydrate nature.

Comparison of two nonculture techniques for detection of Hemophilus influenzae in sputum. In situ hybridization and immunoperoxidase staining with monoclonal antibodies

Two nonculture methods, in situ hybridization and immunoperoxidase staining with monoclonal antibodies, were compared for the detection of Hemophilus influenzae in 184 sputa. For in situ hybridization, a biotin-labeled probe of total genomic DNA of H influenzae type b was prepared that hybridizes specifically with H influenzae, H parainfluenzae, H hemolyticus, and H parahemolyticus DNA. Immunoperoxidase staining was done with monoclonal antibody 8BD9 directed against outer membrane protein P6 of H influenzae. Both techniques detected Hemophilus in sputum equally well and were superior to culture: all 30 sputum samples culture-positive for H influenzae were positive on both nonculture tests, and 13 additional positive sputum samples were detected from which Hemophilus was not cultured. The higher sensitivity of the nonculture tests was mainly attributed to culture failure because of overgrowth of H influenzae by other bacteria, especially in patients with cystic fibrosis. The immunoperoxidase staining technique appeared slightly easier and quicker to perform than the in situ hybridization test. For the in situ DNA hybridization probe, DNA can be prepared from any strain of H influenzae. The immunoperoxidase test requires monoclonal antibody 8BD9 but has a higher specificity than the hybridization technique. Both techniques can be reliably applied, especially for the detection of Hemophilus in sputum of patients with cystic fibrosis.

DNA hybridization with hardjobovis-specific recombinant probes as a method for type discrimination of Leptospira interrogans serovar hardjo

Restriction endonuclease analysis of DNA of Leptospira interrogans, serovar hardjo, showed two distinct types within this serovar. These two types, hardjoprajitno and hardjobovis, cannot be differentiated by monoclonal antibodies. Application of 32P- or biotin-labelled total DNA probes in dot-blot or in situ hybridization assays showed a high sensitivity of the assays but also considerable cross-hybridization. Therefore, a genomic library of hardjobovis was constructed and a number of hardjobovis-specific recombinant clones were isolated. Finally, four clones were selected on the basis of a strong hybridization signal and a high specificity for hardjobovis as compared to hardjoprajitno. In a dot-blot assay as well as in in situ hybridization experiments all four clones gave strong signals, and no cross-hybridization with hardjoprajitno was observed in either type of assay. Our results indicate that specific recombinant DNA probes might provide tools for routine diagnosis and classification in cases of hardjo infections.

Comparative classification of Leptospira serovars of the Pomona group by monoclonal antibodies and restriction-endonuclease analysis

The serovars of the Pomona group of Leptospira interrogans are antigenically closely related and can be classified only with difficulty by conventional typing methods. Monoclonal antibodies (MCAs) were prepared to serovars of the Pomona group. The MCAs were directed against antigens of polysaccharide nature. A battery of six MCAs was selected for the classification of Pomona group reference strains. These MCAs could be used for the typing of all Pomona group strains and unknown isolates. Alternatively, DNA was extracted from the same strains and isolates and digested with restriction enzymes. The patterns that were obtained after gel separation of the DNA digests were characteristic and also allowed classification. Restriction enzyme analysis was complicated but gave detailed information. Classification with MCAs could be easily and rapidly performed.

Detection of Leishmania parasites by DNA in situ hybridization with non-radioactive probes

In situ hybridization techniques develop rapidly into diagnostic tools of considerable value for detection of viruses and bacteria. Here we report the application of this technique for the detection of Leishmania parasites. Biotin-labelled total promastigote DNA was hybridized to cultured Leishmania parasites and to blood and impression smears of infected mice. In promastigotes kinetoplasts were strongly stained, nuclei somewhat more diffuse. In amastigotes both nuclear and kinetoplast DNA hybridized strongly. Amastigotes were easily detected in tissue of infected mice by their stable configuration of kinetoplast and nuclei. Cross-hybridization was observed between Leishmania donovani and L. tropica, but not between these two and L. braziliensis or Trypanosoma cruzi. A minor aspecific staining of host cell nuclei in the smears did not interfere with the detectability of the parasites.

Detection of Leptospira interrogans in clinical specimens by in situ hybridization using biotin-labelled DNA probes

In situ DNA hybridization using biotin-labelled leptospiral DNA was performed on clinical specimens to investigate its usefulness as a technique for the identification of Leptospira interrogans. The applicability of this test in blood, urine and liver smears was demonstrated. In situ DNA hybridization can be completed in only 4 h and it combines the advantage of visualization of the leptospiral morphology with the specificity of the hybridization reaction. No cross-hybridization was observed with other bacteria. This study shows that hybridization in situ can be simple to perform and may contribute to a rapid diagnosis.