Molecular differentiation of Mycobacterium bovis isolates. Review of main techniques and applications

Spatial distribution of Mycobacterium bovis spoligotypes in cattle from the state of Minas Gerais, Brazil

Genotyping methods have led to a better understanding of the epidemiology of Mycobacterium bovis (M. bovis) infection, and its transmission dynamics, as well as the possible phylogenetic relationships between Mycobacterium strains, thus making bovine tuberculosis control programs more efficient. The goal of this study was to characterize the main spoligotypes of M. bovis isolated from cattle in the State of Minas Gerais, Brazil. It was carried out in 28 municipalities of "Triângulo Mineiro" and "Alto Paranaíba" regions of the state. Viscera samples were obtained from 58 bovines positive for tuberculosis according to comparative cervical tests, and from another 100 bovines with lesions suggestive of tuberculosis, which were donated by the National Agricultural Laboratory of Pedro Leopoldo, Minas Gerais. Microbiological isolation was performed in Stonebrink medium, and molecular identification of mycobacteria was performed by PCR. Genotyping was performed using the spoligotyping method at the Agrobiotechnology and Molecular Biology Institute of National Agricultural Technology Institute-National Scientific and Technical Research Council, Buenos Aires, Argentina. Among the 158 viscera samples, we obtained 40 (25%) isolates of M. bovis, and detected 11 spoligotype patterns, with a predominance of SB1142 (37.5%), SB0121 (25.0%), and SB1145 (10.0%). Other standards, SB0295, SB1050, SB0881, SB1144, SB1802, SB0140, SB0120, and SB0849, varied from 2.5 to 7.5%, heterogeneously distributed among the municipalities. The presence of spoligotypes shared with other Brazilian states and different countries indicates their possible exchange through epidemiological relationships, such as the transit of live animals and/or genetic similarity between strains that share a common ancestor.

Evaluation of the discriminatory power of spoligotyping and 19-locus mycobacterial interspersed repetitive unit-variable number of tandem repeat analysis (MIRU-VNTR) of Mycobacterium bovis strains isolated from cattle in Algeria

Bovine tuberculosis (bTB) caused by Mycobacterium (M.) bovis and M. caprae is a transmissible disease of livestock, notifiable to the World Organization for Animal Health (OIE). BTB particularly affects cattle and small ruminants and can be transmitted to humans thereby posing a significant threat to veterinary and public health worldwide. M. bovis is the principal cause of bTB in Algeria. In order to better understand the route of spreading and elaborate an eradication program, isolation and characterization of mycobacteria from Algerian cattle was performed. Sixty strains belonging to the M. tuberculosis complex were analyzed by spoligotyping, thereof 42 by 19-locus-MIRU-VNTR-typing. Spoligotyping revealed 16 distinguishable patterns (Hunter-Gaston discriminatory index [HGDI] of 0.8294), with types SB0120 (n = 20) and SB0121 (n = 13) being the most frequent patterns, representing 55% of the strains. Analyses based on 19-locus-MIRU-VNTR yielded 32 different profiles, five clusters and one orphan pattern, showing higher discriminatory power (HGDI = 0.9779) than spoligotyping. Seven VNTR-loci [VNTR 577 (alias ETR C), 2163b (QU11b), 2165 (ETR A), 2461 (ETR B), 3007 (MIRU 27), 2163a (QUB11a) and 3232 (QUB 3232)] were the most discriminative loci (HGDI ˃ 0.50). In conclusion, 19-locus-MIRU-VNTR yielded more information than spoligotyping concerning molecular differentiation of strains and better supports the elucidation of transmission routes of M. bovis between Algerian cattle herds.

The hard numbers of tuberculosis epidemiology in wildlife: A meta-regression and systematic review

Tuberculosis (TB) is a widespread disease that crosses the human and animal health boundaries, with infection being reported in wildlife, from temperate and subtropical to arctic regions. Often, TB in wild species is closely associated with disease occurrence in livestock but the TB burden in wildlife remains poorly quantified on a global level. Through meta-regression and systematic review, this study aimed to summarize global information on TB prevalence in commonly infected wildlife species and to draw a global picture of the scientific knowledge accumulated in wildlife TB. For these purposes, a literature search was conducted through the Web of Science and Google Scholar. The 223 articles retrieved, concerning a 39-year period, were submitted to bibliometric analysis and 54 publications regarding three wildlife hosts fulfilled the criteria for meta-regression. Using a random-effects model, the worldwide pooled TB prevalence in wild boar is higher than for any other species and estimated as 21.98%, peaking in Spain (31.68%), Italy (23.84%) and Hungary (18.12%). The pooled prevalence of TB in red deer is estimated at 13.71%, with Austria (31.58%), Portugal (27.75%), New Zealand (19.26%) and Spain (12.08%) positioning on the top, while for European badger it was computed 11.75%, peaking in the UK (16.43%) and Ireland (22.87%). Despite these hard numbers, a declining trend in wildlife TB prevalence is apparent over the last decades. The overall heterogeneity calculated by multivariable regression ranged from 28.61% (wild boar) to 60.92% (red deer), indicating that other unexplored moderators could explain disease burden. The systematic review shows that the most prolific countries contributing to knowledge related with wildlife TB are settled in Europe and Mycobacterium bovis is the most reported pathogen (89.5%). This study provides insight into the global epidemiology of wildlife TB, ascertaining research gaps that need to be explored and informing how should surveillance be refined.

Multispacer Sequence Typing for Mycobacterium bovis Genotyping

The molecular typing of Mycobacterium bovis, which causes bovine tuberculosis, can be accomplished by combining different polymorphic markers, contributing to its epidemiological investigation. Multispacer sequence typing (MST) is a sequencing-based method that employs intergenic regions susceptible to higher mutation rates given the low selection pressure. It has been applied to M. tuberculosis, but not to M. bovis. The aim of this study was to evaluate a MST for M. bovis. A total of 58 strains isolated from tissues with lesions suggestive of bovine tuberculosis, coming from cattle herds in six Brazilian states and four standard samples of M. bovis were typified employing the MST technique. Fourteen intergenic regions were used, and four types of genetic events were reported: single nucleotide mutation (SNP), insertion, deletion, and tandem repeat (TR). Seven loci were chosen for typing. Twenty-eight type sequences (ST) were identified, indicating type sequences (ST) were identified, indicating a 92.9% HGDI (Hunter Gaston Discriminatory Index). The data were used to analyze the evolutionary patterns of these isolates and correlate them to phylogeographic lineages based on the formation of clonal complexes generated from eBURST software. Later, we associated the MST with spoligotyping technique, currently considered the gold standard for classification of M. bovis. The results support the MST as an alternative method for genotyping of M. bovis. The method has the advantage of sequencing and the availability of sequences analyzed in public databases, which can be used by professionals around the world as a tool for further analysis. This was the first study to identify the variability of isolates of M. bovis by the MST method.

Broad diversity of Mycobacterium tuberculosis complex strains isolated from humans and cattle in Northern Algeria suggests a zoonotic transmission cycle

Mycobacterium tuberculosis complex (MTBC) comprises closely related species responsible for human and animal tuberculosis (TB). Efficient species determination is useful for epidemiological purposes, especially for the elucidation of the zoonotic contribution. In Algeria, data on MTBC genotypes are largely unknown. In this study, we aimed to investigate the occurrence and diversity of MTBC genotypes causing human and bovine TB in Northern Algeria. During a two-year sampling period (2017-2019) in two regions of Northern Algeria, we observed an overall prevalence of 6.5% of tuberculosis (TB) among slaughtered cattle, which is higher than previous Algerian data yet comparable to neighboring countries. A total of 296 Mycobacterium tuberculosis complex (MTBC) isolates were genotyped by spoligotyping: 181 from tissues with TB-like lesions collected from 181 cattle carcasses and 115 from TB patients. In human isolates, we identified 107 M. tuberculosis, seven M. bovis and one "M. pinnipedii-like", while for bovine samples, 174 isolates were identified as M. bovis, three as M. caprae, three as "M. pinnipedii-like" and one as "M. microti-like". The majority of isolates (89.2%) belonged to 72 different known Shared International Types (SIT) or M. bovis spoligotypes (SB), while we also identified seven new SB profiles (SB2695 to SB2701). Twenty-eight of the SB profiles were new to Algeria. Our data suggest zoonotic transmission in Sétif, where significantly more TB was observed among cattle (20%) compared to the slaughterhouses from the three other regions (5.4%-7.3%) (p < 0.0001), with the isolation of the same M. bovis genotypes from TB patients. The present study showed a high genetic diversity of MTBC isolated from human and cattle in Northern Algeria. Even though relatively small in terms of numbers, our data suggest the zoonotic transmission of TB from cattle to humans, suggesting the need for stronger eradication strategies for bovine TB.

Phylogenetic relationships investigation of Mycobacterium caprae strains from sympatric wild boar and goats based on whole genome sequencing

Tuberculosis (TB) in wildlife challenges epidemiological surveillance and disease control. An outbreak of TB was detected in a free‐ranging wild boar population of a Natural Park in Catalonia (Spain) and the outbreak investigation was conducted in the area. During the study period (2015–2020), 278 wild boars were analysed by gross pathology, histopathology, mycobacterial culture and DVR‐spoligotyping. In addition, all cattle (49) and goat (47) herds of the area were tested with tuberculin skin test. TB compatible lesions were detected in 21 wild boars, and Mycobacterium caprae was isolated in 17 of them with two different spoligotypes: SB0415 (13) and SB1908 (4). Only two goat herds showed TB positive animals that were subsequently slaughtered. M. caprae with the spoligotypes SB0416 and SB0415 were isolated from these animals. To investigate the phylogenetic relationships and the transmission chain of the outbreak, nine strains isolated from six wild boars and three goats of the study area were analysed by whole genome sequencing (WGS) followed by single nucleotide polymorphism (SNP) analysis by maximum likelihood and median‐joining network inference methods. Results indicated that infected wild boars maintained M. caprae strains circulation in their own population and have likely transmitted the infection to goats, thus acting as TB reservoirs, compromising the success of livestock TB eradication campaigns and posing a risk for public health. The results also highlighted the usefulness of WGS followed by SNP analysis in providing relevant epidemiological information when detailed contact data are missing.

Global trends of epidemiological research in livestock tuberculosis for the last four decades

Animal tuberculosis (TB) caused by Mycobacterium tuberculosis complex (MTC) bacteria remains as one of the most significant infectious diseases of livestock, despite decades of eradication programmes and research efforts, in an era where the livestock sector is among the most important and rapidly expanding commercial agricultural segments worldwide. This work provides a global overview of the spatial and temporal trends of reported scientific knowledge of TB in livestock, aiming to gain insights into research subtopics within the animal TB epidemiology domain and to highlight territorial inequalities regarding data reporting and research outputs over the years. To deliver such information, peer-reviewed reports of TB studies in livestock were retrieved from the Web of Science and Google Scholar, systematized and dissected. The validated data set contained 443 occurrence observations, covering the 1981-2020 period (39 years). We highlight a clear move towards transdisciplinary areas and the One Health approach, with a global temporal increase in publications combining livestock with wildlife and/or human components, which reflect the importance of non-prototypical hosts as key to understanding animal TB. It becomes evident that cattle is the main host across works from all continents; however, many regions remain poorly surveyed. TB research in livestock in low-/middle-income countries is markedly growing, reflecting changes in animal husbandry, but also mirroring the globalization era, with a marked increase in international collaboration and capacitation programmes for scientific and technological development. This review gives an overview of the most prolific continents, countries and research fields in animal TB epidemiology, clearly outlining knowledge gaps and key priority topics. The estimated growth trend of livestock production until 2050, particularly in Asia and Africa, in response to human population growth and animal-protein demand, will require further investment in early surveillance and adaptive research to accommodate the higher diversity of livestock species and MTC members and raising the possibility to fine-tune funding schemes.

Mycobacterium bovis: From Genotyping to Genome Sequencing

Mycobacterium bovis is the main pathogen of bovine, zoonotic, and wildlife tuberculosis. Despite the existence of programs for bovine tuberculosis (bTB) control in many regions, the disease remains a challenge for the veterinary and public health sectors, especially in developing countries and in high-income nations with wildlife reservoirs. Current bTB control programs are mostly based on test-and-slaughter, movement restrictions, and post-mortem inspection measures. In certain settings, contact tracing and surveillance has benefited from M. bovis genotyping techniques. More recently, whole-genome sequencing (WGS) has become the preferential technique to inform outbreak response through contact tracing and source identification for many infectious diseases. As the cost per genome decreases, the application of WGS to bTB control programs is inevitable moving forward. However, there are technical challenges in data analyses and interpretation that hinder the implementation of M. bovis WGS as a molecular epidemiology tool. Therefore, the aim of this review is to describe M. bovis genotyping techniques and discuss current standards and challenges of the use of M. bovis WGS for transmission investigation, surveillance, and global lineages distribution. We compiled a series of associated research gaps to be explored with the ultimate goal of implementing M. bovis WGS in a standardized manner in bTB control programs.

Tuberculosis Caused by Mycobacterium bovis in a Sheep Flock Colocated with a Tuberculous Dairy Cattle Herd in Central Ethiopia

Mycobacterium bovis (M. bovis) has an exceptionally wide host range including sheep. Information on tuberculosis (TB) in sheep is scarce, and there appears to be conflicting opinions about the relative susceptibility of sheep to infection. In Ethiopia, there was no single previous report on tuberculosis in sheep, though mixed farming of cattle and sheep is a common practice. In this study, following the observation of TB-like lesions on sheep died from sheep flock kept in contact with cattle herd, further investigation was conducted on the flock to assess the magnitude of the infection and identify and characterize the causative M. bovis strain. An outbreak investigation was carried out on 26 eligible sheep out of 33 sheep found on the farm. Comparative intradermal tuberculin (CIDT) test, postmortem examination, Mycobacterium culturing, and spoligotyping were the techniques used in the study. The prevalence of TB in the tested sheep was 15% (4/26). All the sheep that were positive to CIDT had gross lesions suggestive of TB. Three of the positive sheep had extensive and multiple lesions. M. bovis was isolated from all four sheep and the strain was identified as spoligotype SBO134. The in-contact dairy cows were screened for TB and 98% (45/46) of the cows tested positive to CIDT. Furthermore, the same strain, SB0134, was also isolated from the two in-contact cows. The isolation of a matching genotype (SB0134) of M. bovis from both species sharing a known epidemiologic link strongly suggests that the sheep flock might have acquired the pathogen from the dairy cows. This warrants strict physical separation of the sheep flock from the cattle herd to prevent such interspecies transmission of M. bovis.

Molecular epidemiology of Mycobacterium tuberculosis complex strains isolated from livestock and wild animals in Italy suggests the need for a different eradication strategy for bovine tuberculosis

Bovine tuberculosis (bTB) is an important zoonosis, which has been re-emerging in different ecological scenarios. In Sicily, Italy, from 2004 to 2014, an anatomopathological survey for tuberculosis-like lesions both in farmed and wild animals was performed. The isolates were genotyped using spoligotyping and Mycobacterial Interspersed Repetitive Units-Variable Number of Tandem Repeats (MIRU-VNTR) techniques. High prevalence of lesions was observed for cattle (4%), pigs (4.9%) and wild boars (6.8%), and a total of 625 Mycobacterium bovis isolates were identified. Genotyping analysis showed the presence of 37 different spoligotypes including fifteen spoligotypes not present in other Italian regions and 266 MIRU-VNTR profiles. Spoligotype SB0120 exhibited the highest prevalence in cattle (50%) and pigs (56%) and the highest genetic variety with 126 different MIRU-VNTR profiles. The isolation of M. bovis in a farmer underlines the importance of M. bovis identification during the human TB diagnostic processes. This study supported the use of the genotyping analysis as a valuable tool for the evaluation of the epidemiological role of pigs and other domestic reservoirs such as goats and the role of wildlife in the maintenance of bTB infection.

Diagnosis of mycobacteria in bovine milk: an overview

Tuberculosis remains as the world's biggest threat. In 2014, human tuberculosis ranked as a major infectious disease by the first time, overcoming HIV death rates. Bovine tuberculosis is a chronic disease of global distribution that affects animals and can be transmitted to humans by the consumption of raw milk, representing a serious public health concern. Despite the efforts of different countries to control and eradicate bovine tuberculosis, the high negative economic impact on meat and milk production chains remains, given the decreased production efficiency (approximately 25%), the high number of condemned carcasses, and increased animal culling rates. This scenario has motivated the establishment of official programs based on regulations and diagnostic procedures. Although Mycobacterium tuberculosis and Mycobacterium bovis are the major pathogenic species to humans and bovines, respectively, nontuberculous mycobacteria within the Mycobacterium genus have become increasingly important in recent decades due to human infections, including the ones that occur in immunocompetent people. Diagnosis of mycobacteria can be performed by microbiological culture from tissue samples (lymph nodes, lungs) and secretions (sputum, milk). In general, these pathogens demand special nutrient requirements for isolation/growth, and the use of selective and rich culture media. Indeed, within these genera, mycobacteria are classified as either fast- or slow-growth microorganisms. Regarding the latter ones, incubation times can vary from 45 to 90 days. Although microbiological culture is still considered the gold standard method for diagnosis, molecular approaches have been increasingly used. We describe here an overview of the diagnosis of Mycobacterium species in bovine milk.

Development of a novel immunochromatographic lateral flow assay specific for Mycobacterium bovis cells and its application in combination with immunomagnetic separation to test badger faeces

BACKGROUND

The European badger is an important wildlife reservoir of Mycobacterium bovis implicated in the spread of bovine tuberculosis in the United Kingdom and Ireland. Infected badgers are known to shed M. bovis in their urine and faeces, which may contaminate the environment. To aid bovine tuberculosis control efforts novel diagnostic tests for detecting infected and shedding badgers are needed. We proposed development of a novel, rapid immunochromatographic lateral flow device (LFD) as a non-invasive test to detect M. bovis cells in badger faeces. Its application in combination with immunomagnetic separation (IMS) to detect Mycobacterium bovis cells in badger faeces is reported here.

RESULTS

A novel prototype LFD for M. bovis cells was successfully developed, with unique specificity for M. bovis and a limit of detection 50% (LOD50%) of 1.7 × 104 M. bovis cells/ml. When IMS was employed to selectively capture and concentrate M. bovis cells from badger faeces prior to LFD testing, the LOD50% of the IMS-LFD assay was 2.8 × 105 M. bovis cells/ml faecal homogenate. Faeces samples collected from latrines at badger setts in a region of endemic bovine tuberculosis infection were tested; 78 (18%) of 441 samples tested IMS-LFD assay positive, whereas 140 (32%) tested IMS-qPCR positive (Kappa agreement -0.009 ± 0.044, p = 0.838). Subsequently, when 130 faeces samples from live captured, or captive, badgers of known infection status (on the basis of StatPak, interferon-γ and/or culture results) were tested, the IMS-LFD assay had higher relative diagnostic specificity (Sp 0.926), but poorer relative diagnostic sensitivity (Se 0.081), than IMS-qPCR (Sp 0.706, Se 0.581) and IMS-culture (Sp 0.794, Se 0.436).

CONCLUSIONS

The novel IMS-LFD assay, although very specific for M. bovis, has low analytical sensitivity (indicated by the LOD50%) and would only detect badgers shedding high numbers of M. bovis (>104-5 cells/g) in their faeces. The novel LFD would, therefore, have limited value as a non-invasive test for badger TB surveillance purposes but it may have value for alternative veterinary diagnostic applications.

Genotyping and Resolution of a Case of Osteomyelitis in a 16-Month-Old Boy of Hispanic/African American Ethnicity

Most cases of osteomyelitis in children are caused by Staphylococcus aureus, although Kingella kingae, various streptococci, and Salmonella species also underlie this condition. Organisms such as Mycobacterium, Histoplasma, and Cryptococcus are much less commonly identified as etiologic agents in osteomyelitis. This case report describes a 16-month-old boy of Hispanic/African American ethnicity who had extensive inflammation of and discharge from his right ankle. Imaging studies supported a diagnosis of osteomyelitis. Acid-fast bacillus (AFB) and routine wound cultures were ordered on the wound discharge. The AFB culture yielded a positive result for Mycobacterium bovis, and molecular diagnostic testing further genotyped the microorganism as Mycobacterium bovis, Bacillus Calmette-Guerin (BCG). Herein, we report a rare case of osteomyelitis that we believe resulted from a BCG vaccine that the patient had received outside the United States.

Identificação e genotipagem de Mycobacterium bovis em bovinos positivos no teste intradérmico para tuberculose em Mato Grosso do Sul

Neste estudo, realizou-se genotipagem de isolados de Mycobacterium bovis, provenientes de amostras de tecidos de bovinos positivos no teste cervical comparativo (TCC) para tuberculose em Mato Grosso do Sul, por meio da técnica de spoligotyping. Tecidos de 13 bovinos positivos, oriundos de diferentes municípios do estado, foram cultivados em meio de Stonebrink. As colônias resultantes foram submetidas à coloração de Ziehl-Neelsen e todos os isolados apresentaram características tintoriais de BAAR. Os 13 isolados de BAAR foram identificados por PCR multiplex (mPCR). O gene hsp65 foi alvo para identificação de Mycobacterium spp, a sequência de inserção IS6110 foi alvo para identificação de complexo Mycobacterium tuberculosis (CMT) e a região rvd1rv2031c foi explorada para detecção de M. bovis. Os isolados micobacterianos foram genotipados pela técnica de spoligotyping. Dos 13 bovinos, sete tinham pelo menos uma lesão sugestiva de tuberculose em linfonodos retrofaríngeos, parotídeos e pulmonares ou no pulmão, e em seis não foram encontradas lesões visíveis sugestivas da doença. Na mPCR, 11/13 (84,6%) isolados foram positivos para Mycobacterium spp; 8/13 (61,5%) positivos para CMT e 7/13 (53,8%) positivos para M. bovis. Com base no spoligotyping, oito isolados de BAAR foram agrupados dentro de três diferentes agrupamentos de genótipos e uma amostra remanescente apresentou perfil único, sendo quatro isolados com padrão de espoligotipo SB0121, dois SB1145, dois SB0881 e um SB0140. A técnica de spoligotyping demonstrou que há diversidade genética entre os espoligotipos presentes no estado de Mato Grosso do Sul, embora predomine o perfil SB0121

Extent of Mycobacterium bovis transmission among animals of dairy and beef cattle and deer farms in South Korea determined by variable-number tandem repeats typing

Identifying sources of Mycobacterium bovis transmission would be essential for establishing effective control programs of bovine tuberculosis (TB), a major zoonosis threatening human health worldwide. As an effort to determine the extent of M. bovis transmission among dairy and beef cattle and deer populations, a mycobacterial interspersed repetitive units (MIRU)-variable-number tandem repeats (VNTR) typing method was employed for analysis of 131 M. bovis isolates from 59 Holstein dairy cattle, 39 Korean beef cattle, and 33 deer. Of 31 MIRU-VNTR markers, 15 showed allelic diversity. The most discriminatory locus for M. bovis isolates was VNTR 3336 (h=0.59) followed by QUB 26, MIRU 31, VNTR 2401, and VNTR 3171 which showed high discriminatory power (h=0.43). The combined VNTR loci had an allelic diversity of 0.83. On the basis of the VNTR profiles of 30 VNTR loci, 24 genotypes were identified, and two genotypes were highly prevalent among all M. bovis isolates (33.6% and 19.1%, respectively), thus indicating that more than 50% of the isolates shared common molecular characteristics. Six additional genotypes were common in 2 of the 3 animal species, suggesting a wide interspecies transmission of M. bovis. This study thus demonstrates that MIRU-VNTR typing is useful in differentiation of M. bovis isolates and that M. bovis transmission occurs frequently among farmed animal species, highlighting the importance of bovine TB control programs in different animal species which are often raised in the same villages.

Isolation and molecular characterization of Mycobacterium tuberculosis from humans and cattle in Namwala District, Zambia

Mycobacterium tuberculosis, the causative agent of tuberculosis in humans, is considered primarily a human pathogen. It has, however, been reported in a wide range of domestic and wild animals, often living in close prolonged contact with humans. Sputum samples in which acid fast bacteria were detected in smears were collected from patients at three health facilities in Namwala district, Zambia. Samples from cattle presenting gross lesions compatible with bovine tuberculosis were collected at a local abattoir in the same district. Isolated mycobacteria were identified and genotyped using classical molecular methods. From a total of 33 isolates of M. tuberculosis detected (30 from humans and 3 from cattle), two cattle isolates shared the same spoligotype and MIRU-VNTR pattern with a human patient. This study has for the first time documented the isolation of M. tuberculosis from cattle in Zambia and provides molecular evidence of an epidemiological link between M. tuberculosis isolates from humans and cattle in Namwala district. A possible spill back of M. tuberculosis to humans cannot be excluded and therefore further studies documenting to what extent M. tuberculosis is shed in cattle milk are needed. This finding further suggests that veterinary public health measures to control human TB, should also take into account the bovine reservoir.

Molecular typing of Mycobacterium bovis isolated in the south of Brazil

Bovine tuberculosis is a major infectious disease of the cattle. In this study, 85 M. bovis isolates from 162 lymph nodes, obtained from a herd of cattle on a farm in southern Brazil, were evaluated using spoligotyping and VNTR. The strains were grouped into five clusters and five orphans, showing a heterogenic genetic profile, what could represent diverse geographic origins of the introduced cows and/or the frequent movement of cattle between different properties.

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.

Characterization of Mycobacterium bovis from Humans and Cattle in Namwala District, Zambia

Tuberculosis remains a major public health problem in Zambia. While human to human transmission of Mycobacterium tuberculosis is of major importance in driving the tuberculosis epidemic, the impact of Mycobacterium bovis transmission from infected cattle is largely unknown. This cross-sectional study aimed at molecular characterization of M. bovis in humans and cattle. A total of 100 human sputum samples and 67 bovine tissues were collected and analyzed for the presence of mycobacteria. Of 65 human samples that harbored acid fast bacteria (AFB), 55 isolates were obtained of which 34 were identified as M. tuberculosis and 2 as M. bovis. AFB-positive bovine samples (n = 67) yielded 47 mycobacterial isolates among which 25 were identified as M. bovis and no M. tuberculosis was found. Among the M. bovis isolates, spoligotyping revealed a high homogeneity in genotypes circulating in Namwala district. Human and cattle isolates shared identical MIRU-VNTR genotypes, suggesting that transmission between the two hosts may occur. Therefore, this study has documented zoonotic TB in human patients in Namwala district of Zambia. However, further molecular epidemiological studies in the study area are recommended.

Múltiplas estirpes de isolados de Mycobacteriumbovis identificados por tipagem molecular em bovinos abatidos em matadouros-frigoríficos

O objetivo do presente trabalho foi utilizar métodos bacteriológicos e moleculares para a identificação do Mycobacteriumbovis em lesões observadas em carcaças de bovinos durante a inspeção postmortem de rotina em matadouros-frigoríficos com serviço de inspeção oficial. Foi acompanhado o abate e a inspeção de 825.394 bovinos, sadios ao exame ante mortem pelo serviço de inspeção oficial em dez matadouros-frigoríficos do estado da Bahia. Carcaça de 180 bovinos apresentaram lesões sugestivas de tuberculose e por outras linfadenites. No isolamento bacteriano, 25 amostras apresentaram crescimento disgônico de colônias de coloração creme-amareladas em meio de cultura Stonebrink-Leslie. Desses isolados, 14 foram identificados como M. bovis PCR multiplex e pela técnica do spoligotyping foram discriminados oito diferentes espoligotipos do M. bovis, sendo sete descritos na literatura e um novo spoligotipo sem descrição anterior. O espoligotipo majoritário foi o SB0121, com cinco amostras, sendo descrito no Brasil e em outros países, seguidos por dois clusters, SB295 e SB1055, com dois isolados cada. O espoligotipo SB1145 e SB1648 foram referidos apenas no Brasil e Dinamarca, respectivamente. O espoligotipo SB140 já foi encontrado no Brasil, Argentina, Uruguai e Paraguai. Estes resultados demonstram que os espoligotipos obtidos são compartilhados, até o momento, entre estados brasileiros e entre países da América Latina e Europa. Sendo assim, a discriminação molecular de isolados de M. bovis através do Spoligotyping constitui-se numa ferramenta para estudos epidemiológicos da tuberculose bovina no Estado da Bahia.

Multi-locus variable-number tandem repeat analysis (MLVA) reveals heterogeneity of Mycobacterium bovis strains and multiple genotype infections of cattle in Ethiopia

Bovine tuberculosis (BTB) remains a major threat to animal and human health, and obstructs international and inter-regional livestock trade in Ethiopia. Many aspects of epidemiology of BTB and its causative agent, Mycobacterium bovis (M. bovis) are not well known. Aims of the study were to elucidate molecular characteristics of M. bovis strains using MLVA typing method. Further aim was to determine infection pressure associated with occurrence of multiple genotypes in individual infected cattle. Data and samples were collected in the period July 2006-January 2007 in cattle slaughtered at five representative abattoirs across the country. Molecular investigation of the isolates was carried out using multilocus variable-number tandem-repeat analysis (MLVA) of 28 variable numbers of tandem repeat (VNTR) loci, and the results were compared to spoligotyping. This study is believed to contribute to the knowledge of molecular genetics and epidemiology of M. bovis in Ethiopia and elsewhere with similar BTB epidemic situation and livestock production settings. Four-hundred and six tissue samples from 337 carcasses revealing gross pathologic lesions compatible with BTB were collected from five abattoirs. Fifty-eight isolates obtained from cultured samples were subjected to region of difference (RD) analysis and MLVA typing. RD confirmed all isolates as being M. bovis. MLVA revealed a high heterogeneity of M. bovis (19 genotypes) and the discriminatory power of MLVA was higher than for spoligotyping (Hunter-Gaston Diversity Index (HGDI) 0.92 vs. 0.82). Adoption of the nine VNTR loci with ⩾3 alleles provided good differentiation between the isolates. However, differentiation was optimized when MLVA was combined with spoligotyping (HGDI=0.99). MLVA confirmed infections with multiple genotypes in 38.5% (10/26) of individual animals. In conclusion, the usefulness of MLVA for genotyping M. bovis in high prevalence settings was demonstrated. BTB in Ethiopia is caused by heterogeneous populations of M. bovis and individual carcasses were often infected with different genotypes, indicating a high infection pressure perhaps related to the absence of protective immunity conferred by infection.

Genotypic characterization by spoligotyping and VNTR typing of Mycobacterium bovis and Mycobacterium caprae isolates from cattle of Tunisia

This work is an approach to the molecular epidemiology of Mycobacterium tuberculosis complex (MTBC) bovine infections in Tunisia. A total of 35 MTBC isolates from both lateral retropharyngeal lymph node samples of cattle slaughtered in different Tunisian regions were genotyped by spoligotyping and variable number tandem repeat typing (VNTR)-typing. Spoligotyping allowed to identify two profiles not previously registered, namely SB2024, a Mycobacterium caprae isolate from Nabeul Region (North East Tunisia), the first description of this species in the country, and SB2025 (Mycobacterium bovis) from Sfax Region (Southern Tunisia). A second M. caprae isolate with a spoligotyping profile previously described in Europe mainland, SB0418, was also isolated from a bovine of Sfax region. Both isolates suggest the possibility of a widespread distribution of this species in the country. The predominant spoligotype was SB0120, present in all Tunisian regions selected for the study but Nabeul. Molecular typing also allowed to describe a mixed infection caused by two different M. bovis isolates (SB0120 and SB0848) in the same animal. VNTR typing was highly discriminant by testing a panel of six loci. Loci QUB3232 and QUB11b were the most discriminant, whereas ETR-D and QUB11a had the lower diversity index. The value of allelic diversity can significantly vary among countries; thus, it is important to standardize a panel of loci for future inter-laboratory comparisons. Although VNTR typing proved to be useful for an efficient discrimination among MTBC isolates, especially in combination with spoligotyping, further studies are needed in order to assess the genetic diversity of the MTBC in Tunisia.

Molecular discrimination of Mycobacterium bovis in São Paulo, Brazil

Mycobacterium bovis, a member of the Mycobacterium tuberculosis complex, is the most common agent of cattle tuberculosis, a zoonosis that causes losses in meat and milk production in several countries. In order to support epidemiological studies aimed at controlling the disease, several methods for molecular discrimination of M. bovis isolates have recently been developed. The most frequently used are spacer oligonucleotide typing (spoligotyping), mycobacterial interspersed repetitive units (MIRU), and exact tandem repeat (ETR), but they all have different discriminatory power. In the present study, allelic diversity was calculated for each MIRU and ETR locus, and the Hunter-Gaston discriminatory index (HGI) was calculated for spoligotyping, 10 MIRUs, and 3 ETRs, in 116 isolates of M. bovis obtained from cattle. The analysis of allelic diversity indicated that MIRUs 16, 26, and 27, and ETRs A, B, and C, showed the greatest diversity between the assayed loci. The HGIs for each of the techniques were: spoligotyping=0.738381; MIRU=0.829835; and ETR=0.825337. The associations of the methods' improved discriminatory power were: spoligotyping+MIRU=0.930585; spoligotyping+ETR=0.931034; and MIRU+ETR=0.953373. The greatest discriminatory power was obtained when the three techniques were associated (HGI=0.98051). Considering the analyses of the present study, spoligotyping should be the first method to be used because it differentiates M. bovis from the other members of the Mycobacterium tuberculosis complex. As the associations of MIRU and ETR with spoligotyping resulted in nearly identical HGIs, ETR seems to be the best choice after spoligotyping, because it is faster and more economical than MIRU. Finally, MIRU should be the last method used. In spite of this finding, the choice of the method used should be based on the discriminatory power necessary for the objective at hand.

Spoligotyping and variable number tandem repeat analysis of Mycobacterium bovis isolates from cattle in Brazil

We performed spoligotyping and 12-mycobacterial interspersed repetitive unit-variable number tandem repeats (MIRU-VNTRs) typing to characterise Mycobacterium bovis isolates collected from tissue samples of bovines with lesions suggestive for tuberculosis during slaughter inspection procedures in abattoirs in Brazil. High-quality genotypes were obtained with both procedures for 61 isolates that were obtained from 185 bovine tissue samples and all of these isolates were identified as M. bovis by conventional identification procedures. On the basis of the spoligotyping, 53 isolates were grouped into nine clusters and the remaining eight isolates were unique types, resulting in 17 spoligotypes. The majority of the Brazilian M. bovis isolates displayed spoligotype patterns that have been previously observed in strains isolated from cattle in other countries. MIRU-VNTR typing produced 16 distinct genotypes, with 53 isolates forming eight of the groups, and individual isolates with unique VNTR profiles forming the remaining eight groups. The allelic diversity of each VNTR locus was calculated and only two of the 12-MIRU-VNTR loci presented scores with either a moderate (0.4, MIRU16) or high (0.6, MIRU26) discriminatory index (h). Both typing methods produced similar discriminatory indexes (spoligotyping h = 0.85; MIRU-VNTR h = 0.86) and the combination of the two methods increased the h value to 0.94, resulting in 29 distinct patterns. These results confirm that spoligotyping and VNTR analysis are valuable tools for studying the molecular epidemiology of M. bovis infections in Brazil.

Bovine tuberculosis in South Darfur State, Sudan: an abattoir study based on microscopy and molecular detection methods

Bovine tuberculosis (BTB) is a widespread zoonosis in developing countries but has received little attention in many sub-Saharan African countries including Sudan and particularly in some parts such as Darfur states. This study aimed to detect bovine tuberculosis among caseous materials of cattle slaughtered in abattoirs in South Darfur State, Sudan by using microscopic and PCR-based methods. The study was a cross-sectional abattoir-based study which examined a total of 6,680 bovine carcasses for caseous lesions in South Darfur State between 2007 and 2009. Collected specimens were examined for the presence of acid-fast bacilli (AFB) by using microscopic and culture techniques. Isolated mycobacteria were identified by selected conventional cultural and biochemical tests in comparison to a single tube multiplex PCR (m-PCR) assay which detect Mycobacterium bovis-specific 168-bp amplicons. Of the total 6,680 slaughtered cattle examined in South Darfur, 400 (6 %) showed caseations restricted to lymph nodes (86.8 %) or generalized (13.2 %). Bovine tuberculosis was diagnosed in 12 (0.18 %), bovine farcy in 59 (0.88 %), unidentified mycobacteria in 6 (0.09 %), and missed or contaminated cultures in 7 (0.1 %). Out of 18 cultures with nonbranching acid-fast rods, 12 amplified unique 168-bp sequence specific for M. bovis and subsequently confirmed as M. bovis. With the exception of the reference M. tuberculosis strains, none of the remaining AFB amplified the 337-bp amplicon specific for M. tuberculosis. It could be concluded that bovine tuberculosis is prevalent among cattle in South Darfur representing 4.5 % from all slaughtered cattle with caseous lesions. The study sustains microscopy as a useful and accessible technique for detecting AFB. m-PCR assay proved to be valuable for confirmation of BTB and its differentiation from other related mycobacteriosis, notably bovine farcy.

DNA Typing of Mycobacterium bovis Isolates from Badgers (Meles meles) Culled from Areas in Ireland with Different Levels of Tuberculosis Prevalence

Badgers (Meles meles) have been implicated in the transmission of Mycobacterium bovis infection to cattle in Ireland and UK. Recent studies in Ireland have shown that although the disease is endemic in badgers, the prevalence of disease is not uniform throughout the country and can vary among subpopulations. The extent to which the prevalence levels in badgers impact on the prevalence in cattle is not known. Previously, DNA fingerprinting has shown that M. bovis strain types are shared between badgers and cattle, and that there are a large number of strain types circulating in the two species. In this study we have carried out spoligotyping and variable number tandem repeat (VNTR) analysis of M. bovis isolates from two groups of badgers, representing a wide geographic area, with different tuberculosis prevalence levels. The results of the typing show that there is no geographic clustering of strain types associated with prevalence. However, two VNTR profiles were identified that appear to be associated with high- and low-prevalence M. bovis infection levels, respectively. In addition, spoligotyping and VNTR analysis has provided evidence, for the first time, of multiple infections of individual badgers with different M. bovis strains.

Risk factors associated with bovine tuberculosis and molecular characterization of Mycobacterium bovis strains in urban settings in Niger

A retrospective and a longitudinal survey were carried out at the abattoir of Niamey. Results showed a highly significant difference in suspected tuberculosis (TB) gross lesions among different animal species (P < 0.0001). The proportion of carcasses with TB-like lesions was 0.19% among cattle, 0.11% among camels, 0.001% among sheep and 0.0006% among goats. In cattle, cows are significantly more affected than the other categories (P < 0.001). Also in cattle, TB-like lesions are mostly localized in the lungs (92.77%) followed by the lymph nodes (50.87%) and the liver (32.40%). The prevalence of gross lesions compatible with bovine TB (BTB) is strongly influenced by the season (P < 0.0001), is closely correlated with the origin of the animals (P < 0.001) and has a negative impact on the weight of affected animals (P < 0.0001). Sixty-two samples of suspected TB gross lesions were subject to microbiological analysis and molecular typing of strains. Mycobacterium bovis was identified in 18 animals showing five different spoligotypes, belonging to type 'African 1' previously identified in Central and West Africa. In addition, a profile (SB1982) not previously reported distinguished by the absence of spacers 3, 4, 9, 16, 22, 30 and 39-43 has been characterized in this study. To assess risk factors for BTB transmission, a questionnaire on animal husbandry practices, food habits, and clinical signs of TB in animals and humans was submitted to the heads of 1131 randomly selected households. The main risk factors identified are consumption of unpasteurized milk (91%) and lack of hygiene within households (32-74%). Clinical signs that could be attributed to TB were also reported both in humans and in animals of the households.

Advances in molecular diagnostics for Mycobacterium bovis

The two most important molecular diagnostic techniques for bovine tuberculosis are the polymerase chain reaction (PCR) because of its rapid determination of infection, and DNA strain typing because of its ability to answer important epidemiological questions. PCR tests for Mycobacterium bovis have been improved through recent advances in PCR technology, but still lack the sensitivity of good culture methods, and in some situations are susceptible to giving both false negative and false positive results. Therefore, PCR does not usually replace the need for culture, but is used to provide fast preliminary results. DNA typing of M. bovis isolates by restriction endonuclease analysis (REA) was developed 25 years ago in New Zealand, and remains an important tool in the New Zealand control scheme, where the typing results are combined with other information to determine large and expensive possum poisoning operations. A range of other DNA typing systems developed for M. bovis in the 1990 s have assisted epidemiological investigations in some countries but are now less commonly used. Variable number tandem repeat (VNTR) typing and spoligotyping, either alone or together, have now become the preferred approaches as they are robust and amenable to electronic analysis and comparison. Spoligotyping gives only moderate discrimination but can be easily applied to large numbers of isolates, and VNTR typing provides better discrimination than all other methods except for REA. While the current typing techniques are sufficient for most epidemiological purposes, more discriminating methods are likely to become available in the near future.

Molecular characterization of Mycobacterium bovis isolates from Ethiopian cattle

Background

Bovine Tuberculosis (BTB) is a widespread and endemic disease of cattle in Ethiopia. Information relating to genotypic characteristics of Mycobacterium bovis strains affecting the cattle population in Ethiopia is limited. We carried out molecular characterization of M. bovis strains isolated from BTB infected cattle using the spoligotyping technique. The relationship between distribution of spoligotypes and recorded variables was also investigated. A new approach that can numerically reflect the degree of genetic polymorphism in a M. bovis population was also developed. The study was conducted from July 2006 to January 2007 in cattle slaughtered at five representative abattoirs in Ethiopia.

Results

Forty-five M. bovis isolates were obtained from 406 pathologic tissue specimens collected from 337 carcasses with lesions compatible with BTB. Twelve spoligotypes were identified from 34 distinct strains; with SB1176 as a dominant spoligotype (41.2% of the isolates) followed by SB0133 (14.7%). Comparison of spoligotypes with an M. bovis global database http://www.mbovis.org revealed six new spoligotypes which were subsequently registered in the database with international identification codes of SB1517, SB1518, SB1519, SB1520, SB1521 and SB1522. The majority of strains were obtained from cattle slaughtered at Addis Ababa abattoir. On the basis of the Spoligotype Evolutionary Index, SEI (a numeric expression approach to make standardized comparison of spoligotype evolution), M. bovis isolates from Ethiopia were relatively more heterogeneous (SEI = 3.2) compared to isolates from other countries. This might be attributed to extensive livestock movement linked to trading or seasonal migration, high degree of livestock mingling, and also diversities of the country's agricultural and livestock ecosystems, in addition to lack of disease control measures that led to high infection prevalence. Multiple spoligotype infection was recorded in nine (50%) of infected carcasses and this may indicate the prevailing high degree of super infection.

Conclusions

This study provided molecular evidence for the widespread distribution of M. bovis in the cattle population in Ethiopia. It also demonstrated a relatively high degree of genetic polymorphism of the isolates. Further molecular investigation of M. bovis strains in humans and other domestic animals is recommended in order to elucidate the zoonotic importance as well as reservoirs and pattern of transmission among various hosts.

A review of infection of wildlife hosts with Mycobacterium bovis and the diagnostic difficulties of the 'no visible lesion' presentation

The pathology, frequency and diagnostic implications of 'no visible lesion' (NVL) tuberculosis (Tb), i.e. infection with Mycobacterium bovis in the absence of macroscopic lesions, are described in a wide taxonomic range of wildlife hosts. Information collected and evaluated on the definition and occurrence of NVL Tb, histopathological characteristics, post-mortem techniques to detect minimal lesions, and diagnostic difficulties revealed most Tb-infected individuals with NVL had minute tuberculous lesions, which were difficult to see by eye. Acid-fast organisms (AFO) were sometimes detected in the lesions. Ideally, mycobacterial culture of pools of lymph nodes and/or oropharyngeal tonsils is necessary for the accurate diagnosis of Tb in the absence of macroscopic lesions. At a very minimum, the diagnostic methods applied for studying the prevalence of Tb in the population should be clearly described, to allow comparison between studies.

Molecular typing of Mycobacterium bovis strains isolated in Italy from 2000 to 2006 and evaluation of variable-number tandem repeats for geographically optimized genotyping

Spoligotyping and exact tandem repeat (ETR) analysis of Mycobacterium bovis and M. caprae isolated strains has been routinely carried out in Italy since 2000 to obtain a database of genetic profiles and support traditional epidemiological investigations. In this study, we characterized 1,503 M. bovis and 57 M. caprae isolates obtained from 2000 to 2006 in 747 cattle herds mainly located in northern Italy. We identified 81 spoligotypes and 113 ETR profiles, while the combination of spoligotyping/ETR analysis differentiated 228 genotypes, with genotypic diversity indices of 0.70 (spoligotyping), 0.94 (ETR-A to -E typing), and 0.97 (spoligotyping/ETR-A to -E typing), respectively. Despite the high degree of resolution obtained, the spoligotyping/ETR methods were not discriminative enough in the case of genotypes characterized by the combination of SB0120, the predominant spoligotype in Italy, with the most common ETR profiles. To obtain a more informative subset of typing loci, 24 mycobacterial interspersed repetitive unit-variable-number tandem repeat (MIRU-VNTR) markers were evaluated by analyzing a panel of 100 epidemiologically unrelated SB0120 isolates. The panel was differentiated into 89 profiles with an overall genotypic diversity of 0.987 that could be also achieved by using a minimal group of 13 loci: ETR-A, -B, and -E; MIRU 26 and 40; and VNTR 2163a, 2163b, 3155, 1612, 4052, 1895, 3232, and 3336. The allelic diversity index and the stability of single loci was evaluated to provide the most discriminative genotyping method for locally prevalent strains.

Genotyping North American animal Mycobacterium bovis isolates using multilocus variable number tandem repeat analysis

Multilocus variable number tandem repeat analysis (MLVA) has recently emerged as a genotyping method that is both robust and highly discriminatory for the differentiation of Mycobacterium tuberculosis complex (MTBC) strains, including Mycobacterium bovis. However, MLVA assessment of M. bovis isolates recovered from animals in North America has been limited. Using an epidemiologically diverse set of 41 North American M. bovis animal isolates, MLVA, based on 27 published variable number tandem repeat (VNTR) loci, was evaluated. Nineteen loci displayed polymorphism, which resulted in differentiation of 21 unique MLVA genotypes. A subset of 6 loci differentiated the isolates into 14 genetically related groups that displayed remarkable concordance with the epidemiological data gathered via traditional trace-back methods. In most cases, MLVA exhibited greater resolution than spoligotyping, which differentiated the isolates into 11 groups. MLVA genotyping of M. bovis shows great potential as a molecular typing tool for characterizing the epidemiology of M. bovis animal infections in North America. However, the greatest resolution was achieved by using a combination of both MLVA and spoligotyping.

Isolation and identification of bovine tuberculosis in a Brazilian herd (São Paulo)

Mycobacterium was verified in animals from a Brazilian dairy herd, a total of 42 samples from 30 cows were submitted to culture and the isolated strains were analyzed by two polymerase chain reaction (PCR), the first specific for species belonging to the Mycobacterium complex (MTBC) and the other for differentiating M. tuberculosis from M. bovis. Twenty seven samples (64.3%) from 18 animals (60%) were positive for mycobacteria by culture, including samples from 15 retrofaryngeal lymphnodes (55.5%), 9 prescapular lymphnodes (33.3%), 2 lungs (7.4%), and 1 liver (3.7%). All isolated colonies were confirmed by PCR to contain MTBC organisms, and were identified as M. bovis by the same methodology.

High Mycobacterium bovis genetic diversity in a low prevalence setting

The genetic diversity among South African Mycobacterium bovis isolates from cattle was determined by genetic fingerprinting. The restriction fragment length polymorphism (RFLP) markers IS6110 and polymorphic GC-rich sequence (PGRS) as well as spoligotyping and determination of variable number of tandem repeats (VNTR) were used to characterize sub samples of 91 M. bovis field isolates. PGRS RFLP was the single most discriminatory method and combinations of typing methods, which included IS6110 and/or PGRS had the highest discriminatory power, able to reveal 29 distinct genotypes among 35 farms with no epidemiological link. Three of the farms were co-infected with two genetically unrelated strains. In contrast to reports from European and also other colonised countries on the African continent our findings are suggestive of a high genetic diversity of M. bovis in South Africa's cattle population, implying a variety of unrelated ancestor strains. Despite effective intervention through test-and-slaughter campaigns no indication of a 'founder effect' was apparent in the panel of isolates derived from all infected provinces.

Characterisation of mycobacteria isolated from slaughter cattle in pastoral regions of Uganda

Background

Bovine tuberculosis is a zoonotic problem in pastoral cattle and communities in Uganda. Tuberculin tests in pastoral cattle had shown a high herd but low animal prevalence, with a high proportion of avian reactors. No work had been done to identify the mycobacterial species involved. The objective of the study was to isolate and characterise Mycobacterial species causing tuberculous lesions in slaughtered animals. Lesioned organs compatible with bovine tuberculosis in slaughtered cattle from pastoral areas in Uganda were collected and cultured to isolate mycobacteria. AccuProbe culture identification kits for the Mycobacterium tuberculosis complex, M. avium complex and M. avium were used to identify the isolates. Spoligotyping and Insertion Sequence (IS) 1311 and IS1245 Restriction Fragment Length Polymorphism analysis (RFLP) were used to further characterise the isolates.

Results

Of the 61 lesioned organs and tissues cultured, 19 isolates were identified as M. bovis, 3 as M. avium subsp.hominissuis, 1 as M. intracellulare, 1 as a mixed culture of M. bovis and M. avium sp. and 1 as M. avium sp. and unidentified mycobacteria. Eleven other mycobacteria outside the tuberculosis and avium complex groups were also isolated. Ten new spoligopatterns grouped into three clusters were identified from M. bovis isolates. Two of the three M. avium subsp.hominissuis isolates showed similar patterns on the IS1311 RFLP but all were different on the IS1245 RFLP.

Conclusion

The isolation of M. bovis confirms the ongoing infection with spoligotypes unique to Uganda. Isolation of environmental mycobacteria could explain the high avian or non specific tuberculin reactor patterns commonly observed in pastoral cattle and suggests their pathogenic or opportunistic role in the infection of cattle with disseminated bovine tuberculous lesions.

Genetic Diversity of Xylella fastidiosa Strains from Costa Rica, São Paulo, Brazil, and United States

ABSTRACT The diversity of 42 Xylella fastidiosa strains from Costa Rica, São Paulo, Brazil, and the United States were analyzed using the sequence of the 16S rRNA gene by variable number of tandem repeat (VNTR) fragment analysis and by restriction fragment length polymorphisms (RFLP) of a specific polymerase chain reaction (PCR)-amplification product using enzyme CfoI. Limited variability in the sequence of the 16S rRNA gene was observed and, although the separation was not absolute, most strains from Costa Rica clustered with strains from the United States and not with strains from São Paulo. The PCR-RFLP produced different patterns of DNA bands. The same pattern was shared by strains from Costa Rica, the United States, and two coffee strains from São Paulo, but a different pattern was observed in six coffee and orange strains from Brazil. In all, 32 amplification products were scored in the VNTR fragment analysis. The total variation observed among the X. fastidiosa strains had significant (P < 0.001) contributions from both geography and host origin as inferred by Nei's values of genetic diversity and WINAMOVA statistics. The strains from Costa Rica were isolated from diseased grapevines, coffee, and sweet orange and these strains grouped together and could be distinguished from strains from grapevine from the United States or from either coffee or sweet orange from São Paulo. The strains tested from Costa Rica are most likely of local origin, although the possibility that they have been introduced along with horticultural crops cannot be excluded. In either case, they are examples of independent selection of strains of X. fastidiosa affecting coffee and sweet orange. Greater genetic similarity was observed between strains from Costa Rica and the United States than with those from São Paulo.

Evaluation of the BD ProbeTec ET system for direct detection of Mycobacterium bovis in veterinary specimens

We describe the application of the BD ProbeTec ET direct tuberculosis system for the detection of Mycobacterium bovis in bovine and cervine lymph node tissues. Compared to traditional culture, the overall sensitivity, specificity, and positive and negative predictive values of the BD ProbeTec were 87, 100, 100, and 87%, respectively.

Mycobacteria causing human cervical lymphadenitis in pastoral communities in the Karamoja region of Uganda

Mycobacteria from lymph node biopsies of patients with cervical lymphadenitis reporting for tuberculosis treatment in Matany and Moroto Hospitals in the transhumant areas of Karamoja, Uganda were isolated and characterized. The AccuProbe culture identification kits for Mycobacterium tuberculosis complex (MTC), M. avium complex (MAC) and M. avium were used to identify the isolates. Spoligotyping, IS901 PCR and IS1311 and IS1245 restriction fragment length polymorphism (RFLP) were used to characterize the isolates. Of the 43 biopsies, ten M. avium, seven M. tuberculosis, three M. bovis, and two M. intracellulare were isolated. Two isolates could not be identified with AccuProbe and from 19 samples no mycobacteria could be isolated. Three isolates with the Beijing spoligotype were identified from the seven M. tuberculosis isolates. The spoligopatterns of the M. bovis isolates had previously been detected in cattle in Uganda. Isolation of members of the MAC group reflects the complex interaction between the transhumant communities, water sources and their cattle. None of the M. avium isolates harboured IS901, and all showed several bands on IS1311 and IS1245 RFLP, in accordance with M. avium subsp. hominissuis. Composite dendrograms of IS1311 and IS1245 RFLP showed that the isolates were similar and identical patterns were found. The isolation of M. bovis confirms the human infection with zoonotic mycobacteria in areas where consumption of raw milk and meat is routine. Isolation of environmental mycobacteria also confirms their increasing role in human disease and the occupational risk of infection in the transhumant ecosystem in the absence of safe drinking water and environmental contamination.

Bottlenecks and broomsticks: the molecular evolution of Mycobacterium bovis

Mycobacterium bovis is the cause of tuberculosis in cattle and is a member of the Mycobacterium tuberculosis complex. In contrast to many other pathogenic bacterial species, there is little evidence for the transfer and recombination of genes between cells. The clonality of this group of organisms indicates that the population structure is dominated by reductions in diversity, caused either by population bottlenecks or selective sweeps as entire chromosomes become fixed in the population. We describe how these forces have shaped not only the phylogeny of this group but also, at a very local level, the population structure of Mycobacterium bovis in the British Isles. We also discuss the practical implications of applying this knowledge to understanding the spread of infection and the development of improved vaccines and diagnostic tests.

Human Mycobacterium bovis infection in the United Kingdom: Incidence, risks, control measures and review of the zoonotic aspects of bovine tuberculosis

Amongst the members of the Mycobacterium tuberculosis complex (MTBC), M. tuberculosis is mainly a human pathogen, whereas M. bovis has a broad host range and is the principal agent responsible for tuberculosis (TB) in domestic and wild mammals. M. bovis also infects humans, causing zoonotic TB through ingestion, inhalation and, less frequently, by contact with mucous membranes and broken skin. Zoonotic TB is indistinguishable clinically or pathologically from TB caused by M. tuberculosis. Differentiation between the causative organisms may only be achieved by sophisticated laboratory methods involving bacteriological culture of clinical specimens, followed by typing of isolates according to growth characteristics, biochemical properties, routine resistance to pyrazinamide (PZA) and specific non-commercial nucleic acid techniques. All this makes it difficult to accurately estimate the proportion of human TB cases caused by M. bovis infection, particularly in developing countries. Distinguishing between the various members of the MTBC is essential for epidemiological investigation of human cases and, to a lesser degree, for adequate chemotherapy of the human TB patient. Zoonotic TB was formerly an endemic disease in the UK population, usually transmitted to man by consumption of raw cows' milk. Human infection with M. bovis in the UK has been largely controlled through pasteurization of cows' milk and systematic culling of cattle reacting to compulsory tuberculin tests. Nowadays the majority of the 7000 cases of human TB annually reported in the UK are due to M. tuberculosis acquired directly from an infectious person. In the period 1990-2003, between 17 and 50 new cases of human M. bovis infection were confirmed every year in the UK. This represented between 0.5% and 1.5% of all the culture-confirmed TB cases, a proportion similar to that of other industrialized countries. Most cases of zoonotic TB diagnosed in the UK are attributed to (i) reactivation of long-standing latent infections acquired before widespread adoption of milk pasteurization, or (ii) M. bovis infections contracted abroad. Since 1990, only one case has been documented in the UK of confirmed, indigenous human M. bovis infection recently acquired from an animal source. Therefore, for the overwhelming majority of the population, the risk of contracting M. bovis infection from animals appears to be extremely low. However, bovine TB is once again a major animal health problem in the UK. Given the increasing numbers of cattle herds being affected each year, physicians and other public health professionals must remember that zoonotic TB is not just a disease of the past. A significant risk of M. bovis infection remains in certain segments of the UK population in the form of (i) continuing on-farm consumption of unpasteurized cows' milk, (ii) retail sales by approved establishments of unpasteurized milk and dairy products and (iii) occupational exposure to infectious aerosols from tuberculous animals and their carcases.

Multiple-locus variable number tandem repeats analysis for genetic fingerprinting of pathogenic bacteria

DNA fingerprinting has attracted considerable interest as means for identifying, tracing and preventing the dissemination of infectious agents. Various methods have been developed for typing of pathogenic bacteria, which differ in discriminative power, reproducibility and ease of interpretation. During recent years a typing method, which uses the information provided by whole genome sequencing of bacterial species, has gained increased attention. Short sequence repeat (SSR) motifs are known to undergo frequent variation in the number of repeated units through cellular mechanisms most commonly active during chromosome replication. A class of SSRs, named variable number of tandem repeats (VNTRs), has proven to be a suitable target for assessing genetic polymorphisms within bacterial species. This review attempts to give an overview of bacterial agents where VNTR-based typing, or multiple-locus variant-repeat analysis (MLVA) has been developed for typing purposes, together with addressing advantages and drawbacks associated with the use of tandem repeated DNA motifs as targets for bacterial typing and identification.