Potential application of new diagnostic methods for controlling bovine tuberculosis in Brazil

Mycobacterium bovis induced human tuberculosis in India: Current status, challenges & opportunities

Tuberculosis (TB) caused by Mycobacterium tuberculosis is a leading cause of human deaths due to any infectious disease worldwide. However, infection of Mycobacterium bovis, primarily an animal pathogen, also leads to the development of 'human tuberculosis'. Infected animals have been considered the major source of M. bovis infection and humans get exposed to M. bovis through close contact with infected animals or consumption of contaminated milk, unpasteurized dairy products and improperly cooked contaminated meat. The information on the global distribution of bovine TB (bTB) is limited, but the disease has been reported from all the livestock-producing middle- and low-income countries of the world. In recent years, there is a renewed interest for the control of bTB to minimize human infection worldwide. In India, while the sporadic presence of M. bovis has been reported in domestic animals, animal-derived food products and human beings from different geographical regions of the country, the information on the national prevalence of bTB and transmission dynamics of zoonotic TB is, however, not available. The present article reviewed published information on the status of M. bovis-induced zoonotic TB to highlight the key challenges and opportunities for intervention to minimize the risk of M. bovis infection in humans and secure optimum animal productivity in India.

Use of a gyrB PCR-RFLP method to diagnose tuberculosis and identify the causative Mycobacterium sp. in cattle and humans

GyrB PCR-restriction fragment length polymorphism (RFLP) could be applied to diagnose bovine and human tuberculosis and detect the causative agent. The lymph nodes and lungs from 50 cattle positive in tuberculin skin test were examined by histopathology and PCR-RFLP of a 1020-bp fragment of the gyrB gene. Swab smear samples from the nasal cavity, pleural, and abdominal cavities were also evaluated by cytological methods. Furthermore, the cultures of 50 sputum samples from the patients were assessed by PCR-RFLP using RsaI, TaqI, SacII enzymes. In histopathology, 39 cattle were positive and the acid-fast bacilli were seen in the Ziehl-Neelsen stained sections. Using gyrB PCR-RFLP, M. bovis was found as the etiological agent in 41 cattle. In terms of the human samples, the causative agent in 41 samples was M. tuberculosis, and M. bovis was isolated from two samples. It seems that gyrB PCR-RFLP could be applied as an accurate and reliable method for identifying the M. tuberculosis complex (MBTC) MBTC species. The isolation of M. bovis from the human specimens should be considered in the control strategies for tuberculosis.

A molecular strategy to optimize bovine tuberculosis post-mortem diagnosis and the exposure to Mycobacterium tuberculosis variant bovis

Bovine tuberculosis (bTB) is a zoonotic disease caused by Mycobacterium tuberculosis var. bovis, for which the definitive diagnosis is accomplished by bacterial isolation, which has biosafety issues and requires long time. Thus, diagnostic methods with potential to be faster and more efficient can represent an advance in bTB epidemiological knowledge and decrease exposure to M. tuberculosis var. bovis. This study aimed to validate a molecular test for bTB post-mortem diagnosis, as a strategy to reduce waste in bovine production. A total of 185 tissues from animals of infected herds or with suspected lesions at abattoir were evaluated through bacterial isolation, PCR and histopathology. PCR and histopathology showed sensitivities of 45.1% and 71.2%, respectively, and specificities of 83.3% and 83.0%, respectively, when compared to bacterial isolation. The combination of both tests resulted in enhanced specificity and positive predictive values.Therefore, PCR in conjunction with histopathology may be used as screening, in which concordant results can be considered conclusive, and discordant results may be submitted to bacterial isolation.

Utility of xpert® MTB/RIF ultra assay in the rapid diagnosis of bovine tuberculosis in wildlife and livestock animals from South Africa

Members of the Mycobacterium tuberculosis complex (MTBC) bacteria, mainly Mycobacterium bovis (M. bovis), cause bovine tuberculosis (bTB) in livestock and wildlife animals. Confirmation of the disease is through culture and verification of the causative agent by molecular tests. In this study, we assessed the utility of the Xpert ® MTB/RIF Ultra assay, an automated molecular test originally designed to improve the detection of tuberculosis (TB) and rifampicin resistance in clinical sputum samples of human origin, by conducting a comparative evaluation with a culture based method routinely used at the Onderstepoort Veterinary Research (OVR). A total of 167 samples (tissue, n = 165; pus, n = 1; abscess, n = 1) from different wildlife and livestock animals (from 65 individual animals) were analyzed. Mycobacterium tuberculosis complex species was isolated in 63 (37.72 %) of the 167 samples, and was detected in 79 (47.3 %) of the samples by Xpert ® MTB/RIF Ultra assay. Based on the standard culture test, the diagnostic sensitivity and specificity of the Xpert ® MTB/RIF Ultra assay was found to be 95.24 % and 82 % respectively. All animals that were confirmed bTB positive by culture method were also found to be positive with the Xpert ® MTB/RIF Ultra assay in at least one sample (indicating a 100 % sensitivity of the method at the animal level). Non-tuberculous mycobacteria were isolated in 9 (3.4 %) of the samples analysed and none were detected by Xpert ® MTB/RIF Ultra assay, highlighting that this molecular test is highly specific. Xpert ® MTB/RIF Ultra assay was found to have great potential for the rapid diagnosis of the bTB in animals, hence allowing early intervention by regulatory authorities.

ELISA using a recombinant chimera of ESAT-6/MPB70/MPB83 for Mycobacterium bovis diagnosis in naturally infected cattle

Bovine tuberculosis (bTB) control programs generally rely on intradermal tuberculin tests for the antemortem diagnosis of Mycobacterium bovis infection in cattle, but these tests detect only a portion of the infected animals. The aim of the present study was to evaluate the diagnostic coverage of a combination of the bTB antemortem techniques known as the comparative intradermal tuberculin test (CITT) and an ELISA based on a recombinant chimera of ESAT-6/MPB70/MPB83 as the antigen in cattle. The results were compared to postmortem findings based on M. bovis culturing and PCR. Paired comparisons of all data (n=92) demonstrated that ELISA and LST results compared to the culturing results did not present significant differences (P=0.27 on McNemar’s test and P=0.12 on Fisher’s exact test, respectively). Using culturing as the gold standard, the sensitivity and specificity of ELISA were 79.5% (95% CI: 64.5–89.2%) and 75.5% (95% CI: 62.4–85.1%), respectively, whereas LST demonstrated 100% sensitivity (95% CI: 91.03–100%) and 92.5% specificity (95% CI: 82.1–97.0%). The ELISA results did not reveal significant differences in relation to the LST results (P>0.99 on Fisher’s exact test). Using the latter as the gold standard, the sensitivity and specificity of ELISA were 79.1% (95% CI: 64.8–88.6%) and 79.6% (95% CI: 66.4–88.5%), respectively. The use of ELISA with the recombinant chimera of ESAT-6/MPB70/MPB83 as the antigen complements the diagnostic coverage provided by CITT and increases the removal of infected animals from herds.

Positive Correlation between IP-10 and IFN-γ Levels in Rhesus Monkeys (Macaca mulatta) with Either Naturally Acquired or Experimental Infection of Mycobacterium tuberculosis

Numerous studies identify that IP-10 and IFN-γ are involved in leucocyte migration and activation and regarded as promising surrogate biomarkers in human and bovine tuberculosis infection, but there is lack of evidence for IP-10 in nonhuman primates. In this study, we directly determined IP-10 and IFN-γ levels in plasma from 30 healthy monkeys, 30 monkeys with naturally acquired tuberculosis, 4 monkeys experimentally infected with tuberculosis, and PPD stimulated whole blood of 14 monkeys with naturally acquired tuberculosis by ELISA. Higher plasma levels of IP-10 and IFN-γ were observed in natural tuberculosis monkeys than in healthy controls. The dynamic changes of plasma IP-10 and IFN-γ in experimental infections showed consistent representation of a transient increase during the infection period. After PPD stimulation, release of IP-10 and IFN-γ is significantly induced in natural tuberculosis monkeys, but the stimulation index of IP-10 was significantly lower than IFN-γ. Further analysis showed that positive correlation between IP-10 and IFN-γ existed in healthy and tuberculosis monkeys. Our findings support plasma IP-10 and IFN-γ as biomarkers for monitoring ongoing inflammation of nonhuman primate tuberculosis, and IFN-γ is a more valuable diagnostic biomarker.

Comparative study of Mycobacterium bovis primary isolation methods

For the definitive diagnosis of bovine tuberculosis, isolation of the etiologic agent is required. However, there is no consensus on the best methodology for isolation of Mycobacterium bovis in Brazil. This study evaluated the most used decontaminants and culture media in the country, in order to identify the best combination for the Brazilian samples. Three decontaminants – 2% sodium hydroxide (w/v), 0.75% hexadecylpiridinium chloride (w/v) and 5% sulphuric acid (v/v) and four culture media – 7H11 Middlebrook with additives and OADC supplement “A” (7H11 A), the same media with another supplement trademark (7H11 B), tuberculosis blood agar (B83) and Stonebrink's medium were compared. Regarding the isolation, there were no significant differences between the decontaminants and media combinations, except 7H11A combined to any decontaminant. However, the mean colonies score was significantly greater when the samples were decontaminated with 5% sulphuric acid and inoculated in 7H11 B or SB, without significant difference between them, although colonies appeared earlier on 7H11B than on SB. The trademark of OADC supplement influenced the isolation rate and the number of isolated colonies in Middlebrook 7H11. An incubation time of four weeks was required to detect all positive samples in 7H11 B after decontamination with 5% sulphuric acid but there was an increase in the number of colonies until the sixth week of incubation. Overall, the best strategy for the primary isolation of M. bovis from Brazilian samples was the decontamination with 5% sulphuric acid (final concentration) and inoculation in Middlebrook 7H11 medium formulated with OADC supplement “B”.

Molecular Typing of Mycobacterium bovis from Cattle Reared in Midwest Brazil

Mycobacterium bovis is the causative agent of bovine tuberculosis (BTB), the pathogen responsible for serious economic impact on the livestock sector. In order to obtain data on isolated M. bovis strains and assist in the control and eradication program for BTB, a cross sectional descriptive molecular epidemiology study in the Brazilian Midwest was conducted. Through spoligotyping and 24-loci MIRU-VNTR methods, 37 clinical isolates of M. bovis circulating in the region were analyzed, 10 isolated from the state of Mato Grosso, 12 from the state of Mato Grosso do Sul and 15 from the state of Goiás. The spoligotyping analysis identified 10 distinct M. bovis profiles (SB0121 n = 14, SB0295 n = 6, SB0140 n = 6, SB0881 n = 3, SB1144 n = 2, SB1145 n = 2, SB0134 n = 1, SB1050 n = 1, SB1055 n = 1, SB1136 n = 1) grouped in six clusters and four orphan patterns. The MIRU-VNTR 24-loci grouped the same isolates in six clusters and 22 unique orphan patterns, showing higher discriminatory power than spoligotyping. When associating the results of both techniques, the isolates were grouped in five clusters and 24 unique M. bovis profiles. Among the 24-loci MIRU-VNTR evaluated, two, ETR-A and QUB 11b loci, showed high discriminatory ability (h = ≥ 0.50), while MIRU 16, MIRU 27, ETR-B, ETR-C, Mtub21 and QUB 26 loci showed moderate ability (h = 0.33 or h = 0.49) and were the most effective in evaluating the genotypic similarities among the clinical M. bovis isolate samples. Herein, the 29 patterns found amongst the 37 isolates of M. bovis circulating in the Brazilian Midwest can be due to the animal movement between regions, municipalities and farms, thus causing the spread of various M. bovis strains in herds from Midwest Brazil.

Evaluation of complementary diagnostic tools for bovine tuberculosis detection in dairy herds from India

Aim:

A cross-sectional study was undertaken to know the herd prevalence and evaluate the single intradermal tuberculin testing (SITT), culture isolation, and polymerase chain reaction (PCR) analysis for the diagnosis of bovine tuberculosis (TB).

Materials and Methods:

A total of 541 cows of three dairy farms of Bareilly and Mukteshwar were screened by SITT followed by collection of pre-scapular lymph node (PSLN) aspirates (71), milk (54), and blood (71) samples from reactor animals. These clinical samples were processed for culture isolation and direct PCR-based identification and species differentiation.

Results:

Out of 541 cows screened by SITT, 71 (13.12%) animals were found positive. Mycobacteria were isolated from 3 (4.22%) PSLN aspirate but not from any cultured milk and blood samples. 28 (39.43%) PSLN aspirate and 5 (9.25%) milk samples were positive for Mycobacterium TB (MTB) complex (MTC) by PCR amplification for the IS6110 insertion sequence; however, blood samples were found negative. For species differentiation, multiplex-PCR using 12.7 kb primers was conducted. Out of 28 PSLN aspirate, Mycobacterium bovis was detected in 18 (64.28%) and MTB in 8 (28.57%), whereas 2 aspirate samples (7.14%) were positive for both the species. All the five milk positive samples were positive for M. bovis.

Conclusion:

Direct detection of bovine TB by a molecular-based method in dairy animals after preliminary screening was appeared to be more sensitive and specific compared to the conventional method (i.e., culture isolation). Its application in form of serial testing methodology for the routine diagnosis and thereafter, culling of infected stock may be suggested for the control programs in dairy herds. The PSLN aspirate was found to be the most suitable specimen for culture isolation and PCR-based detection of Mycobacterium spp. among live infected animals.

Exames complementares no diagnóstico da tuberculose em bovinos reagentes à tuberculinização comparada

RESUMO: Objetivou-se com este estudo comparar diferentes métodos complementares de diagnóstico (macroscópico, histopatológico, sorológico e molecular) da tuberculose, em bovinos naturalmente infectados. O trabalho deu-se por meio de amostras colhidas em abate sanitário de 40 bovinos reagentes no teste cervical comparativo (TCC) para tuberculose. A inspeção macroscópica post mortem das carcaças foi acompanhada de colheita de amostras de muco nasal, sangue e tecido (fígado, pulmão e linfonodo mediastínico) para realização do exame de reação em cadeia pela polimerase (PCR), de Enzyme-Linked Immunosorbent Assay (ELISA) e histopatológico com colorações de hematoxilina-eosina (HE) e Ziehl-Neelsen (ZN), respectivamente. Dos 40 bovinos inspecionados no abate, 22 (55%) animais apresentaram algum tipo de lesão macroscópica sugestiva de tuberculose. Nos achados histopatológicos visualizados em HE, 13 (32,5%) carcaças apontaram alterações histológicas, sendo 6 (15%) nos linfonodos mediastínicos, 5 (12,5%) no fígado e 3 (7,5%) no pulmão. Não foi observada a presença de bacilos álcool-ácido resistentes em nenhuma das amostras avaliadas. O ensaio sorológico de ELISA/IDEXX(r) identificou um (2,5%) animal reagente, e o teste de PCR detectou DNA de Mycobacterium bovis em uma (2,5%) amostra. Concluiu-se que entre os exames complementares de diagnóstico avaliados nenhum foi capaz de detectar todos os animais que estavam positivos na tuberculinização, porém a associação de diferentes métodos pode garantir a confiabilidade do diagnóstico.

Molecular Epidemiology of Mycobacterium bovis in Humans and Cattle

Bovine tuberculosis (bTB), caused by Mycobacterium bovis (M. bovis), is a serious re-emerging disease in both animals and humans. The evolution of the Multi- and Extensively drug-resistant M. bovis strains (MDR-TB and XDR-TB) represents a global threat to public health. Worldwide, the disease is responsible for great economic losses in the veterinary field, serious threat to the ecosystem, and about 3.1% of human TB cases, up to 16% in Tanzania. Only thorough investigation to understand the pathogen's epidemiology can help in controlling the disease and minimizing its threat. For this purpose, various tools have been developed for use in advanced molecular epidemiological studies of bTB, either alone or in combination with standard conventional epidemiological approaches. These techniques enable the analysis of the intra- and inter-species transmission dynamics of bTB. The delivered data can reveal detailed insights into the source of infection, correlations among human and bovine isolates, strain diversity and evolution, spread, geographical localization, host preference, tracing of certain virulence factors such as antibiotic resistance genes, and finally the risk factors for the maintenance and spread of M. bovis. They also allow for the determination of epidemic and endemic strains. This, in turn, has a significant diagnostic impact and helps in vaccine development for bTB eradication programs. The present review discusses many topics including the aetiology, epidemiology and importance of M. bovis, the prevalence of bTB in humans and animals in various countries, the molecular epidemiology of M. bovis, and finally applied molecular epidemiological techniques.

Diagnosis of bovine tuberculosis: review of main techniques

Abstract Bovine tuberculosis (BTB) remains an important economic and zoonotic problem in Latin America. Traditionally, the fight against BTB is initiated by the implementation of routine diagnostic tests for certification of free properties. The diagnosis of BTB can be made by direct and indirect methods, in which we can mention clinical, post mortem, histopathological, immunological, bacteriological and molecular methods. The renewal of scientific interest in tuberculosis in recent year has led to develop and improve methods of diagnosis, prevention, control and eradication of BTB. The aim of this review is to present and discuss different diagnosis methods of BTB.

Molecular diagnosis of bovine tuberculosis in bovine and human samples: implications for zoonosis

ABSTRACT 

Aim: To develop emerging diagnostic technique for bovine tuberculosis and to identify its potential risk factors. Materials & methods: Bacterial genomic DNA was isolated from bovine milk and human sputum samples and subjected to PCR using specific primer pairs. PCR results were validated using bacteriological cultures. Results: PCR amplification of the targeted DNA fragment of Mycobacterium bovis was successful in 12.33% (37/300) of the bovine samples. Interestingly, 500-bp DNA fragment was also amplified in 6.67% (6/90) of the sputum indicating the possibility of zoonotic transmission. Rearing of livestock in household, unpasteurized milk consumption and smoking were identified as potential risk factors. Conclusion: Results of the study may add value to bovine tuberculosis eradication campaigns to achieve the One Health initiative.

Molecular typing of Mycobacterium bovis isolates: a review

Mycobacterium bovis is the main causative agent of animal tuberculosis (TB) and it may cause TB in humans. Molecular typing of M. bovis isolates provides precise epidemiological data on issues of inter- or intra-herd transmission and wildlife reservoirs. Techniques used for typing M. bovis have evolved over the last 2 decades, and PCR-based methods such as spoligotyping and mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) have been extensively used. These techniques can provide epidemiological information about isolates of M. Bovis that may help control bovine TB by indicating possible links between diseased animals, detecting and sampling outbreaks, and even demonstrating cases of laboratory cross-contamination between samples. This review will focus on techniques used for the molecular typing of M. bovis and discuss their general aspects and applications.

A multidisciplinary approach to diagnose naturally occurring bovine tuberculosis in Brazil

A herd infected naturally with tuberculosis was investigated by different diagnostic methods. Ninety days after a screening test that identified 21 cows as skin test positive, a Comparative Intradermal Tuberculin Test (CITT) was performed in those 21 cows and in 29 other randomly selected skin test negative cows. Milk samples and nasal swabs were collected prior to the CITT for bacteriological culture and PCR, while blood samples were collected for IFN release and antibody responses to MPB70 and MPB83, at three time points post tuberculin injection. Animals positive by CITT were slaughtered and disease confirmation undertaken. Based on the Kappa test, IFN was comparable to the standard tests (culture, PCR and CITT) at all three sampling points. Results from both antibody ELISAs were similar but were not comparable to the standard tests. T-test analysis of the CITT, IFN and ELISAs demonstrated that their performances were not correlated. There is increasing recognition that individually, available diagnostic tests do not detect all infected cattle. Therefore, a comprehensive strategy for the diagnosis of bovine TB should include test results for the detection of both cellular and humoral immune responses where there may be animals at different stages of infection.

Accurate diagnostics for Bovine tuberculosis based on high-throughput sequencing

Background

Bovine tuberculosis (bTB) is an enduring contagious disease of cattle that has caused substantial losses to the global livestock industry. Despite large-scale eradication efforts, bTB continues to persist. Current bTB tests rely on the measurement of immune responses in vivo (skin tests), and in vitro (bovine interferon-γ release assay). Recent developments are characterized by interrogating the expression of an increasing number of genes that participate in the immune response. Currently used assays have the disadvantages of limited sensitivity and specificity, which may lead to incomplete eradication of bTB. Moreover, bTB that reemerges from wild disease reservoirs requires early and reliable diagnostics to prevent further spread. In this work, we use high-throughput sequencing of the peripheral blood mononuclear cells (PBMCs) transcriptome to identify an extensive panel of genes that participate in the immune response. We also investigate the possibility of developing a reliable bTB classification framework based on RNA-Seq reads.

Methodology/Principal Findings

Pooled PBMC mRNA samples from unaffected calves as well as from those with disease progression of 1 and 2 months were sequenced using the Illumina Genome Analyzer II. More than 90 million reads were splice-aligned against the reference genome, and deposited to the database for further expression analysis and visualization. Using this database, we identified 2,312 genes that were differentially expressed in response to bTB infection (p<10⁻⁸). We achieved a bTB infected status classification accuracy of more than 99% with split-sample validation on newly designed and learned mixtures of expression profiles.

Conclusions/Significance

We demonstrated that bTB can be accurately diagnosed at the early stages of disease progression based on RNA-Seq high-throughput sequencing. The inclusion of multiple genes in the diagnostic panel, combined with the superior sensitivity and broader dynamic range of RNA-Seq, has the potential to improve the accuracy of bTB diagnostics. The computational pipeline used for the project is available from http://code.google.com/p/bovine-tb-prediction.

Assessing the histopathology to depict the different stages of bovine tuberculosis infection in a naturally infected herd

The standard method for detection of bovine tuberculosis (TB) is the single intradermal tuberculin test (SITT). Nevertheless, current studies suggest that a single test is not enough to detect all cattle infected by TB, particularly when animals present different stages of infection. A dairy herd comprised of 270 cows was studied and 15 were reactive to SITT plus nine inconclusive animals. Blood samples (for IFN and ELISA) were collected from these 24 cows. At 30 days after injection of PPD, all the cows that were reactive to any of the employed tests were slaughtered, and tissues were processed by Bacteriology, Histopathology (HP) and PCR. According to HP 33.4% of the animals were positive, 45.8% inconclusive and 20.8% were negative. The inconclusive samples came from IFN positive animals, signalizing recent infection. Regarding the animals that were negative to HP, all of them were identified by IFN while ELISA was negative. Immune responses are different in recent and advanced infections, what supports the identification between chronically or recently infected animals. This multidisciplinary approach is mandatory for the interpretation of the various tools that are frequently employed for the diagnosis of TB and mainly to identify all infected animals.

Use of recombinant proteins MPB70 or MPB83 as capture antigens in ELISAs to confirm bovine tuberculosis infections in Brazil

The objective was to evaluate the use of two indirect IgG-ELISA tests (with recombinant proteins MPB70 or MPB83, respectively, as capture antigens) as confirmatory tests for diagnosis of bovine tuberculosis in a herd of naturally infected dairy cows. Results for ELISA-MPB70 and ELISA-MPB83 were similar (kappa statistic=0.92) on Days 0 (day of intradermal injection with purified protein derivatives, PPD), 7, and 21. The kappa statistic between ELISA and the Comparative Intradermal Tuberculin Test, as well as ELISA sensitivity and specificity (relative to culture or PCR as standards) were: 0.7, 34.4% and 75% on Day 0; 0.25, 53.8% and 66.6% on Day 7; and 0.01, 1.8% and 77.7% on Day 21, respectively. In conclusion, although ELISAs using MPB70 or MPB83 as antigens were not reliable indicators of infection status, especially on Days 7 and 21, they were of potential value as complementary tools to intradermal PPD testing.