Occurrence of false-positive results in three paratuberculosis - ELISAs performed in a tuberculous herd.

The interference of bovine tuberculosis (TB) on the efficacy of paratuberculosis (PTB) diagnostic tests has been evaluated. A group of 32 tuberculous cows identified by both intradermal tests and gamma-interferon assay, 16 of them confirmed by the recovery of M.bovis from tissues, was tested by three different PTB- ELISAs, being two commercials and one in-house. The rest of the adult animals of the herds, totalizing 216 TB-negative animals, were also tested as a control group. Fecal culture for PTB was negative in all animals, but seven (21.8%) tuberculous cows produced false-positive reactions when tested by various PTB-ELISAs, leading to a misdiagnosis. Tuberculosis impairs the specificity of serological tests for paratuberculosis diagnosis and should be considered for the reliability of PTB control programs.

Paratuberculosis: an update

Paratuberculosis is a chronic enteritis that affects ruminants and is caused by Mycobacterium avium paratuberculosis (Map). The disease is worldwide spread and causes important economic losses. In Brazil, the bacillus was isolated in the south and northeast regions of the country and in Rio de Janeiro, but there are no enough epidemiological studies about its occurrence. Isolation of Map from tissues or fecal samples is 100% specific, but Map shows the most fastidious growth of all mycobacteria. Incubation lasts 8 -12 weeks, with a dependency on exogenous mycobactin J. Diagnostic tests based on specific DNA sequences allow fast and secure identification, and PCR has been used to confirm positive culture results and to identify Map in feces, milk and tissues. The most frequently used target sequences are the gene encoding the 16S rRNA, and the insertion element IS900. Serological assays are widely used for the herd diagnosis of the disease. A commercial ELISA with M. phlei pre-adsorption step achieves a specificity of 95.4% to 99% and a sensitivity of about 45%. Until now, there is no effective treatment for ill animals and control programs are based on managing procedures of herds and culling of symptomatic animals. In Brazil, paratuberculosis was recently identified and has been demonstrated even in autochthonous closed herds. Therefore, it is essential to perform an epidemiological national research and to investigate the economic impact of the disease in our herds. These results could promote a control program of paratuberculosis adapted to the Brazilian requirements.

A Paratuberculose é uma enterite crônica que afeta ruminantes, causada por Mycobacterium avium paratuberculosis (Map). A doença é cosmopolita e determina importantes perdas econômicas. No Brasil, o agente foi isolado nas regiões Sul e Nordeste além do Rio de Janeiro, mas não há estudos epidemiológicos suficientes sobre sua ocorrência. O isolamento de Map dos tecidos ou amostras fecais é 100% especifico, mas Map apresenta o crescimento mais fastidioso dentre todas as micobactérias, com período de incubação de até 8 -12 semanas, dependente de fonte exógena de micobactina J. Os testes diagnósticos baseados em seqüências especificas de DNA permitem uma identificação rápida e segura, e PCR tem sido usado para confirmar resultados de cultura positiva e para identificar Map em fezes, leite ou tecidos. O alvo mais frequentemente utilizado é o gene que codifica para o 16S rRNA, e o elemento de inserção IS900. Testes sorológicos são amplamente utilizados para o diagnóstico de rebanho. Um ELISA comercial com uma etapa de pré-adsorção com M. phlei alcança uma especificidade de 95,4% a 99% e uma sensibilidade de cerca de 45%. Até agora, não existe tratamento efetivo para animais doentes e os programas de controle são baseados em medidas de manejo e descarte dos animais sintomáticos. No Brasil, a paratuberculose foi recentemente demonstrada mesmo em rebanhos fechados e autóctones. Assim, é essencial realizar-se um inquérito epidemiológico nacional e investigar o impacto econômico da enfermidade em nossos rebanhos. Estes resultados poderiam ser utilizados para um programa de controle da paratuberculose adaptado ás necessidades de nosso país.

Paratuberculosis: an update: [review]

Paratuberculosis is a chronic enteritis that affects ruminants and is caused by Mycobacterium avium paratuberculosis (Map). The disease is worldwide spread and causes important economic losses. In Brazil, the bacillus was isolated in the south and northeast regions of the country and in Rio de Janeiro, but there are no enough epidemiological studies about its occurrence. Isolation of Map from tissues or fecal samples is 100 percent specific, but Map shows the most fastidious growth of all mycobacteria. Incubation lasts 8 -12 weeks, with a dependency on exogenous mycobactin J. Diagnostic tests based on specific DNA sequences allow fast and secure identification, and PCR has been used to confirm positive culture results and to identify Map in feces, milk and tissues. The most frequently used target sequences are the gene encoding the 16S rRNA, and the insertion element IS900. Serological assays are widely used for the herd diagnosis of the disease. A commercial ELISA with M. phlei pre-adsorption step achieves a specificity of 95.4 percent to 99 percent and a sensitivity of about 45 percent. Until now, there is no effective treatment for ill animals and control programs are based on managing procedures of herds and culling of symptomatic animals. In Brazil, paratuberculosis was recently identified and has been demonstrated even in autochthonous closed herds. Therefore, it is essential to perform an epidemiological national research and to investigate the economic impact of the disease in our herds. These results could promote a control program of paratuberculosis adapted to the Brazilian requirements.

A Paratuberculose é uma enterite crônica que afeta ruminantes, causada por Mycobacterium avium paratuberculosis (Map). A doença é cosmopolita e determina importantes perdas econômicas. No Brasil, o agente foi isolado nas regiões Sul e Nordeste além do Rio de Janeiro, mas não há estudos epidemiológicos suficientes sobre sua ocorrência. O isolamento de Map dos tecidos ou amostras fecais é 100 por cento especifico, mas Map apresenta o crescimento mais fastidioso dentre todas as micobactérias, com período de incubação de até 8 -12 semanas, dependente de fonte exógena de micobactina J. Os testes diagnósticos baseados em seqüências especificas de DNA permitem uma identificação rápida e segura, e PCR tem sido usado para confirmar resultados de cultura positiva e para identificar Map em fezes, leite ou tecidos. O alvo mais frequentemente utilizado é o gene que codifica para o 16S rRNA, e o elemento de inserção IS900. Testes sorológicos são amplamente utilizados para o diagnóstico de rebanho. Um ELISA comercial com uma etapa de pré-adsorção com M. phlei alcança uma especificidade de 95,4 por cento a 99 por cento e uma sensibilidade de cerca de 45 por cento. Até agora, não existe tratamento efetivo para animais doentes e os programas de controle são baseados em medidas de manejo e descarte dos animais sintomáticos. No Brasil, a paratuberculose foi recentemente demonstrada mesmo em rebanhos fechados e autóctones. Assim, é essencial realizar-se um inquérito epidemiológico nacional e investigar o impacto econômico da enfermidade em nossos rebanhos. Estes resultados poderiam ser utilizados para um programa de controle da paratuberculose adaptado ás necessidades de nosso país.

Sexual behaviour and infection rates for HIV, blood-borne and sexually transmitted infections among patients attending drug treatment centres in Rio de Janeiro, Brazil.

A survey was carried out in 2 drug use treatment centres (TCs) in Rio de Janeiro, Brazil, to assess risk behaviours, HIV infection and other sexually transmitted infections/blood-borne infections (STIs/BBIs). Two hundred and twenty-five drug users (195 males and 30 females) were interviewed and clinically examined, and their blood and urine were tested for STIs/BBIs. Prevalences (%) for these infections were as follows--HIV: 0.9, hepatitis B virus (HBV): 14.7, hepatitis C virus (HCV): 5.8, syphilis: 5.3, gonorrhoea/chlamydia (CT/NG): 4.7. In bivariate analyses CT/NG infection was associated with younger age (P=0.003); current genitourinary symptoms (odds ratio [OR]=6.2) and a mainly illegal source of income (OR=9.1). Hepatitis C infection was associated with a history of ever having injected any drug (OR=19.6), and with each one of the injected drugs. After multiple logistic regression, lower educational level (adjusted odds ratio [AOR]=3.70) and 'ever having injected drugs' (AOR=3.69) remained as independent risk factors for hepatitis B infection. In conclusion, TCs must implement programmes directed towards the prevention of STIs/BBIs.

A recombinant peptide antigen line immunoassay optimized for the confirmation of Chagas' disease.

BACKGROUND: The transfusion of contaminated blood has become the major route of transmission for Chagas' disease in Brazil. Current screening tests are insensitive and yield conflicting results, while confirmatory assays do not exist. A line immunoassay (INNO-LIA Chagas Ab [INNO-LIA]) combining relevant, immunodominant recombinant and synthetic antigens on a single nylon membrane strip was evaluated for the serologic confirmation of Chagas' disease. STUDY DESIGN AND METHODS: Sera from 1062 patients and healthy residents of four Brazilian regions endemic for Chagas' disease were used for test optimization. The established confirmation algorithm was evaluated with an independent set of positive (n = 75) and negative (n = 148) samples. RESULTS: In the optimization phase, without an established comparative gold standard, the results with the INNO-LIA were compared with those obtained in four other screening assays. In the validation phase, the INNO-LIA showed a sensitivity of 100 percent (95% CI, 95.21-100) and a specificity of 99.32 percent (95% CI, 96.29-99.98) for well-characterized sera. Moreover, its specificity reached 100 percent with a set of 40 sera obtained from patients with documented leishmaniasis. The interpretation criteria defined in this study indicated that the INNO-LIA accurately detected the presence of antibodies to various specific antigens of Trypanosoma cruzi. CONCLUSION: The INNO-LIA Chagas Ab assay may become the first commercial assay to reliably confirm the presence of antibodies to T. cruzi.

In situ hybridization: a molecular approach for the diagnosis of the microsporidian parasite Enterocytozoon bieneusi.

Microsporidia are emerging as opportunistic pathogens in patients with acquired immunodeficiency syndrome (AIDS). Enterocytozoon bieneusi is the most commonly reported microsporidium that is detected in gastrointestinal specimens. This report describes an in situ hybridization technique with a 30-base specific synthetic DNA probe for detection of E bieneusi by light microscopy. Formalin-fixed paraffin-embedded duodenal biopsy specimens from three patients with AIDS, chronic diarrhea, and E bieneusi infection confirmed by electron microscopy were used in this study. Light microscopic examination after colorimetric detection allowed the identification of different stages of the pathogen's life cycle in the cytoplasm of enterocytes. No cross-reactivity was noted between the probe and human DNA. Our study underscores the applicability of a synthetic-labeled oligonucleotide for the detection and identification of E bieneusi in clinical samples.

Evaluation of three commercial enzyme-linked immunosorbent assays for diagnosis of Chagas' disease.

Chagas' disease is a common cause of morbidity in Latin American countries. In Brazil, naturally occurring transmission of its etiologic agent, Trypanosoma cruzi, has been almost completely abolished through effective control programs aimed at the triatomid insect vector. Thus, transfusion of blood from infected donors has become the major route for contracting Chagas' disease due to the socioeconomically motivated migration of residents from areas where the disease is endemic to the larger urban centers. Therefore, the employment of screening tests is mandatory for all blood banks throughout the country. We compared the diagnostic performances of three commercially available screening assays used in routine testing in Brazilian blood banks: the Abbott Chagas antibody enzyme immunoassay (Abbott Laboratórios do Brasil, São Paulo), the BIOELISACRUZI kit (Biolab-Mérieux, Rio de Janeiro, Brazil), and the BIOZIMA Chagas kit (Polychaco S.A.I.C., Buenos Aires, Argentina). The evaluation was performed with sera obtained from chagasic patients and healthy residents of four different areas in Brazil where Chagas' disease is either endemic or emergent and where clinical manifestations of the disease and circulating parasite strains vary. The results obtained with each kit were compared to matched in-house enzyme-linked immunosorbent assay and immunofluorescence assay data obtained for each sample. Depending on the area under investigation, the three commercial kits produced specificity values between 93.3 and 100.0%, sensitivity values between 97.7 and 100%, and accuracies ranging from 93.6 to 100.0%.

Performance of HTLV-1 screening assays in Brazil.

In recent years a variety of studies have been carried out to compare the accuracy (generally expressed in terms of sensitivity and specificity) of commercially available anti-HTLV tests. None of these studies were performed in Brazil or in any other South American country. During the characterization of our Brazilian reference panel we evaluated the sensitivities and specificities of the Abbott HTLV EIA (100%; 89.7%) and the Biochrom HTLV-1/-2 ELISA (100%; 42.4%). Our conclusion was that both assays may be problematic in terms of correctly identifying HTLV-negative sera. We therefore adjusted the cut-off values using receiver operating characteristics (ROC). ROC analysis, which involves calculating sensitivity and specificity for several cut-off values, can be used to ascertain the co-variation in the specificity and sensitivity of any assay giving quantitative results. The optimum cut-off value for the assay in a given study population is the point that gives highest possible sensitivity in conjunction with a small false-positive fraction. Using the HTLV-1/-2 Western blot as the "gold standard", we were able to improve the specificity of the Biochrom HTLV-1/-2 assay to 95% without affecting its sensitivity of 100%. However, it seems that when using the Biochrom HTLV-1/-2 ELISA, there may be problems in separating positive and negative sera. In the case of the Abbott HTLV EIA, our ROC analysis revealed that the cut-off value suggested by the manufacturer was nearly identical to the optimum cut-off value. Adjustment will affect neither sensitivity nor specificity. However, a slight adjustment of the cut-off value result in a clearer separation of the positive and negative populations. Furthermore, we assume that this adjustment will help to avoid false-positive results when larger serum panels are investigated. Further investigations will show whether or not this problem is linked to the geographical regions where the test is performed (e.g. polyclonal stimulation due to parasitic infections in tropical countries).

Polymerase chain reaction detection of Trypanosoma cruzi in human blood samples as a tool for diagnosis and treatment evaluation.

Trypanosoma cruzi specific sequences were amplified by the polymerase chain reaction from total blood of human chagasic patients and normal individuals. A 330 bp fragment originating from kinetoplast DNA was specifically detected in most chagasic individuals. We tested the sensitivity and specificity of this method in normal and affected individuals attending the Evandro Chagas Hospital, Rio de Janeiro. The results of these tests were compared with serological diagnosis performed using standard techniques, and in some cases with xenodiagnosis. We found that none of the serologically negative individuals gave any specific amplification product, whereas 55 out of 61 patients previously serodiagnosed as chagasic were positive using the PCR method (sensitivity: 90%). Xenodiagnosis, which is currently considered to be the most sensitive parasitological technique for Chagas' disease diagnosis, detected only 12 out of 28 serologically positive patients (sensitivity: 43%). The usefulness of the PCR method was further investigated with chagasic patients who had received anti-parasite treatment with benznidazole. It has always been difficult to evaluate the incidence of cure in such cases by serology, since a humoral response against T. cruzi antigens may remain for years even in the absence of the parasite. We observed a positive amplification result in only 9 out of 32 treated patients who remained reactive when tested using classical serology. These observations suggest that PCR is the most sensitive technique available for direct detection of T. cruzi in chagasic patients and that it can be a very useful instrument for the follow-up of patients after specific treatment.

Use of a simplified polymerase chain reaction procedure to detect Trypanosoma cruzi in blood samples from chronic chagasic patients in a rural endemic area.

The feasibility of using DNA amplification by the polymerase chain reaction (PCR) for specific detection of Trypanosoma cruzi in human blood specimens was investigated. One hundred blood samples were collected in an endemic area of Minas Gerais, Brazil. They were submitted to DNA extraction and PCR amplification with kinetoplast DNA-specific primers using a simplified boiling procedure that linearized most minicircle molecules without the aid of chemical reagents. Samples that gave negative results were checked for possible inhibition of amplification using primers derived from a human-specific sequence, and those showing some level of inhibition were retested after a new DNA extraction. Of 86 patients previously diagnosed as chagasic by serologic techniques, 83 were positive in our PCR test (sensitivity = 96.5%), including all the xenodiagnosis-positive patients and 21 (87.5%) of 24 xenodiagnosis-negative individuals. In addition, four of six patients with doubtful serologic results were confirmed as positive by PCR. Our results suggest that the PCR may be a useful complement to serology in the diagnosis of Chagas' disease, and that it is the most powerful technique available for parasite detection in patients with chronic disease.

Chagas' disease diagnosis: evaluation of several tests in blood bank screening.

Blood transfusion is one of the principal routes of transmission of Chagas' disease, a major endemic disease in Latin America. Methods for blood screening are not accurate and may yield false results that lead to high social and economic costs. This study compares two methods of diagnosing Chagas' disease (indirect immunofluorescence and hemagglutination) and several enzyme-linked immunosorbent assays (ELISAs) with regard to specificity and sensitivity, by using human sera with known serologic and parasitologic characteristics, as well as samples with discrepant results on conventional serologic tests. An ELISA using recombinant antigens showed no cross-reactivity with sera that were positive for other diseases. All evaluated ELISAs performed well, and their use may lead to a reduction of more than 50 percent in the number of discordant sera. Further improvements are needed in view of the complexity of the serologic diagnosis of Chagas' disease.

Use of recombinant antigens for the accurate immunodiagnosis of Chagas' disease.

We tested two Trypanosoma cruzi recombinant antigens in a diagnostic test for Chagas' disease. These antigens were a cytoplasmic repetitive antigen (CRA) and a flagellar repetitive antigen (FRA). The results indicate that the recombinant antigens give better results when used in combination than when used separately, and that the removal of the beta-galactosidase portion of the recombinant fusion proteins increases the specificity of the diagnostic test for Chagas' disease. In addition, a direct enzyme-linked immunosorbent assay (ELISA), which involves the use of peroxidase-labeled antigens to detect the immune-complexes, was developed and compared with a conventional ELISA. The results indicate that the recombinant (CRA+FRA) ELISA is better than the conventional ELISA in the diagnosis of Chagas' disease, providing 100% specificity and sensitivity in all sera tested to date. The recombinant ELISA was compared with conventional serologic tests (hemagglutination and immunofluorescence) for Chagas' disease diagnosis, and the results show that the recombinant ELISA does not give rise to false-positive results that are observed with the two other tests. The use of the recombinant ELISA should be useful in the prevention of transmission of Chagas' disease by blood transfusions.

Description of putative ribosomal RNAs with low abundance, developmental regulation, and the identifier sequence.

Three RNA species (5, 2, 0.15 kb) characterized by the repetitive identifier (ID) sequence, expressed constitutively, and at low abundance have been identified in rat L6 muscle cells by hybridization to cDNA pL6-411. Comigration of these three RNAs with 28, 18, and 5.8 S ribosomal RNAs (rRNAs) has suggested the possibility that pL6-411 RNAs are related to ribosomes or ribosome-like structures. Subsequent experiments showed that pL6-411-related RNAs could indeed be found in ribosome-like particles which were indistinguishable from ribosomes when separated on sucrose gradients under native (low salt, isolation of intact ribosomes) or denaturing conditions (detergent, high salt, isolation of ribosome subunits). Furthermore, we demonstrate that pL6-411-related RNAs are cytoplasmic in L6 cells, may be transcribed in nucleoli, and, based on their nucleotide sequence, have the potential of inter- and intramolecular hybridization. Expression of pL6-411 RNAs was also shown in adult as well as in fetal rat tissues after Day 14 of gestation. These above findings provide supportive evidence for the hypothesis that pL6-411 5- and 2-kb RNAs could exist in a subset of ribosomes. These ribosome-like pL6-411 particles nevertheless differ from ribosomes in that their associated RNAs have different nucleotide sequences, are of lower abundance, and are up-regulated later in development than rRNAs. We discuss our results in the context of a postulated ribosome subset containing RNAs other than rRNAs. These ribosome-like particles might be involved in the translational control of ID-positive mRNAs.