Limited usefulness of the IS6110 touchdown-PCR in blood for tuberculin skin test false-negative cattle with serological response to Mycobacterium bovis.

Ante-mortem diagnosis of bovine tuberculosis (bTB) is based mainly on the tuberculin skin test (TST) and the ɣ-IFN release assay (IGRA). Some infected animals escape screening tests, thus, limit herd sanitation. Previous reports have suggested a predominant pattern of multi-organ lesions attributable to Mycobacterium bovis (the causative agent of bTB) bacteraemia. A case-control study was conducted to investigate blood PCR as an alternative tool for improving ante-mortem detection of TST false-negative bovines. Cases comprised 70 TST false-negative bovines (cases), which were serology positive, and controls included 81 TST positive bovines; all of them confirmed as infected with M. bovis. Detection of the IS6110 target through touchdown blood-PCR (IS6110 TD-PCR) was performed. The positivity of the blood-PCR was 27.2% in the control group. This performance was similar to the 15% obtained among cases (p = 0.134). Most cases identified by the IS6110 TD-PCR exhibited focalized lesions (p = 0.002). Results demonstrated that blood-PCR could detect TST false-negative cattle, even if they are negative for IGRA. Considering that cases exhibited humoral response to M. bovis, further studies conducted in a pre-serological stage could provide evidence about the real contribution of the technique in herds.

[Interlaboratory test: Isolation of Mycobacterium bovis from granulomatous lesions in bovine]. / Ensayo interlaboratorio: aislamiento de Mycobacterium bovis a partir de lesiones granulomatosas en bovinos.

Mycobacterium bovis is the causative agent of bovine tuberculosis. The diagnostic laboratory confirmation is made through bacterial isolation. The aim of interlaboratory tests is to assess the performance of each participant in comparison with other of similar capacities. The test objective was to determine the efficiency of isolation of M. bovis. Four laboratories were part of the test and processed 25 blind tissue samples from granulomatous lesions and with previous M. bovis isolation. The laboratory that had the highest proportion of isolates was A (68%), followed by C (60%) and then B and D (both with 52%). The greatest concordance was observed between B-D and B-C laboratories (68%). The differences could be due to specific factors in each laboratory procedures. This type of interlaboratory tests highlights errors in the bacteriology and identifies critical points in the process to detect M. bovis accurately.

Identification and evaluation of new Mycobacterium bovis antigens in the in vitro interferon gamma release assay for bovine tuberculosis diagnosis.

Bovine tuberculosis (bTB) is a common zoonotic disease, caused by Mycobacterium bovis (M. bovis), responsible for significant economic losses worldwide. Its diagnosis is based on the detection of cell mediated immunity under the exposure to protein purified derivative tuberculin (PPD), a complex and poorly characterized reagent. The cross-reactivity to non-tuberculous mycobacterium species (false-positive results) has been crucial to develop a more proper antigen. In the present study, we selected six M. bovis Open Reading Frames (Mb1992, Mb2031c, Mb2319, Mb2843c, Mb2845c and Mb3212c) by in-silico analysis and evaluated them in experimental and natural infection; none of these antigens had been previously assessed as diagnostic antigens for bTB. The reactivity performance was tested in animals with both positive and negative Tuberculin Skin Test (TST) results as well as in cattle infected with Mycobacterium avium subesp. paratuberculosis (MAP). The six recombinant antigens individually induced an IFN-γ response, with overall responder frequency ranging from 18.3 to 31%. Mb2845c was the most valuable antigen with the potential to discriminate TST-positive cattle from either TST-negative or MAP infected animals. Mb2845c showed similar performance to that observed with ESAT-6 and PPD-B among TST and MTC specific-PCR positive animals, although this result needs to be proven in further studies with a higher sample size. Our data confirm the feacibility to implement bioinformatic screening tools and suggest Mb2845c as a potential diagnostic antigen to be tested in protein cocktails to evaluate their contribution to bTB diagnosis.

Genotyping Mycobacterium bovis from cattle in the Central Pampas of Argentina: temporal and regional trends

Mycobacterium bovis is the causative agent of bovine tuberculosis (TB), a disease that affects approximately 5% of Argentinean cattle. Among the molecular methods for genotyping, the most convenient are spoligotyping and variable number of tandem repeats (VNTR). A total of 378 samples from bovines with visible lesions consistent with TB were collected at slaughterhouses in three provinces, yielding 265 M. bovis spoligotyped isolates, which were distributed into 35 spoligotypes. In addition, 197 isolates were also typed by the VNTR method and 54 combined VNTR types were detected. There were 24 clusters and 27 orphan types. When both typing methods were combined, 98 spoligotypes and VNTR types were observed with 27 clusters and 71 orphan types. By performing a meta-analysis with previous spoligotyping results, we identified regional and temporal trends in the population structure of M. bovis. For SB0140, the most predominant spoligotype in Argentina, the prevalence percentage remained high during different periods, varying from 25.5-57.8% (1994-2011). By contrast, the second and third most prevalent spoligotypes exhibited important fluctuations. This study shows that there has been an expansion in ancestral lineages as demonstrated by spoligotyping. However, exact tandem repeat typing suggests dynamic changes in the clonal population of this microorganism.

Genotyping Mycobacterium bovis from cattle in the Central Pampas of Argentina: temporal and regional trends.

Mycobacterium bovis is the causative agent of bovine tuberculosis (TB), a disease that affects approximately 5% of Argentinean cattle. Among the molecular methods for genotyping, the most convenient are spoligotyping and variable number of tandem repeats (VNTR). A total of 378 samples from bovines with visible lesions consistent with TB were collected at slaughterhouses in three provinces, yielding 265 M. bovis spoligotyped isolates, which were distributed into 35 spoligotypes. In addition, 197 isolates were also typed by the VNTR method and 54 combined VNTR types were detected. There were 24 clusters and 27 orphan types. When both typing methods were combined, 98 spoligotypes and VNTR types were observed with 27 clusters and 71 orphan types. By performing a meta-analysis with previous spoligotyping results, we identified regional and temporal trends in the population structure of M. bovis. For SB0140, the most predominant spoligotype in Argentina, the prevalence percentage remained high during different periods, varying from 25.5-57.8% (1994-2011). By contrast, the second and third most prevalent spoligotypes exhibited important fluctuations. This study shows that there has been an expansion in ancestral lineages as demonstrated by spoligotyping. However, exact tandem repeat typing suggests dynamic changes in the clonal population of this microorganism.

Association between spoligotype-VNTR types and virulence of Mycobacterium bovis in cattle.

Mycobacterium bovis is the causative agent of bovine tuberculosis, a disease that affects approximately 5% of Argentine cattle. The aim of this research was to study if it is possible to infer the degree of virulence of different M. bovis genotypes based on scorified observations of tuberculosis lesions in cattle. In this study, we performed association analyses between several parameters with tuberculosis lesions: M. bovis genotype, degree of progression of tuberculosis, and animal age. For this purpose, the genotype was determined by spoligotyping and the degree of bovine tuberculosis gross lesion was quantified with a score based on clinical observations (number, size, and location of granulomas along with histopathologic features). This study was performed with naturally infected cattle of slaughterhouses from three provinces in Argentina. A total of 265 M. bovis isolates were obtained from 378 pathological lesion samples and 192 spoligotyping and VNTR (based on ETR sequences) typing patterns were obtained. SB0140 was the most predominant spoligotype, followed by SB0145. The spoligotype with the highest lesion score was SB0273 (median score of 27 ± 4.46), followed by SB0520 (18 ± 5.8). Furthermore, the most common spoligotype, SB0140, had a median score of 11 ± 0.74. Finally, the spoligotype with the lowest score was SB0145 (8 ± 1.0). ETR typing of SB0140, SB0145, SB0273, and SB0520 did not subdivide the lesion scores in those spoligotypes. In conclusion, SB0273 and SB0520 were the spoligotypes with the strongest association with hypervirulence and both spoligotypes were only found in Río Cuarto at the south of Córdoba province. Interestingly, there is no other report of any of these spoligotyes in Latin America.

European 1: a globally important clonal complex of Mycobacterium bovis.

We have identified a globally important clonal complex of Mycobacterium bovis by deletion analysis of over one thousand strains from over 30 countries. We initially show that over 99% of the strains of M. bovis, the cause of bovine tuberculosis, isolated from cattle in the Republic of Ireland and the UK are closely related and are members of a single clonal complex marked by the deletion of chromosomal region RDEu1 and we named this clonal complex European 1 (Eu1). Eu1 strains were present at less than 14% of French, Portuguese and Spanish isolates of M. bovis but are rare in other mainland European countries and Iran. However, strains of the Eu1 clonal complex were found at high frequency in former trading partners of the UK (USA, South Africa, New Zealand, Australia and Canada). The Americas, with the exception of Brazil, are dominated by the Eu1 clonal complex which was at high frequency in Argentina, Chile, Ecuador and Mexico as well as North America. Eu1 was rare or absent in the African countries surveyed except South Africa. A small sample of strains from Taiwan were non-Eu1 but, surprisingly, isolates from Korea and Kazakhstan were members of the Eu1 clonal complex. The simplest explanation for much of the current distribution of the Eu1 clonal complex is that it was spread in infected cattle, such as Herefords, from the UK to former trading partners, although there is evidence of secondary dispersion since. This is the first identification of a globally dispersed clonal complex M. bovis and indicates that much of the current global distribution of this important veterinary pathogen has resulted from relatively recent International trade in cattle.