Use of Hugh and Leifson's medium as a simple screening test to aid in the differentiation of Arcobacter spp. from background flora during their isolation from foodstuffs

AIMS

To investigate the suitability of Hugh and Leifson's medium (HLM) as the basis of a simple screening test to differentiate between contaminants and Arcobacter spp. during their isolation from foodstuffs.

METHODS AND RESULTS

Characterized Arcobacter spp. were obtained from recognized culture collections. Wild-type isolates of Arcobacter spp. and contaminants were obtained using published isolation protocols. Retail packs of red meats were used as the source of the isolates. Eighteen defined Arcobacter spp. gave no reaction on HLM, as did 10 local wild-type isolates. Overall 163 contaminants were studied for oxidative reactions on HLM and 86% of isolates demonstrated this property.

CONCLUSIONS

HLM can usefully serve as a simple and effective screening test to differentiate between Arcobacter spp. and contaminants.

SIGNIFICANCE AND IMPACT OF THE STUDY

Arcobacter isolation procedures are still being developed, and no effective diagnostic media currently exist. Rapidly excluding most contaminants can markedly increase the efficiency of isolation procedures by removing the need for extensive biotyping or the requirement to isolate DNA and conduct PCR tests.

Campylobacter spp. in conventional broiler flocks in Northern Ireland: epidemiology and risk factors

Risk factors for Campylobacter infection in conventional broiler flocks in the time period up to the first removal of birds to slaughter were investigated over a maximum of five consecutive production cycles in a cohort of 88 broiler farms in Northern Ireland. Samples for Campylobacter culture, which consisted of 14 cloacal swabs per flock, were collected from one house on each farm prior to the first depopulation of birds. In total 388 flocks were sampled, of which 163 tested positive for Campylobacter spp. (42.0%; 95% CI 35.1-48.9%). Data on farm and flock variables were obtained from questionnaires and random-effects logistic regression modelling used to investigate the association between these and the Campylobacter status of flocks. Six variables, all of which were significant at p<0.05, were included in the final multivariable model. These included a combined variable on the presence of rodents on farms, which showed an increased odds of infection in flocks where the farmer reported having observed rodents during the production cycle (OR=2.1) and/or where rodent droppings were observed at the sampling visit (OR=2.9). Other variables that were significantly associated with an increased odds of infection included the age of the birds at sampling (odds ratio for its linear effect=1.16 for each day of increase in age), season (summer versus other seasons OR=2.0), farms with three or more broiler houses (OR=2.9 compared to those with one house), the frequency of footbath disinfectant changes (OR=2.5 for once weekly and OR=4.0 for less than once weekly compared to twice weekly changes) and a categorical variable on the standard of tidiness and cleanliness of the broiler house ante-room (OR=2.0 and OR=4.9 for flocks from houses with poorer standards). There was no significant evidence of direct carry-over of infection from one production cycle to the next, neither was there evidence of other farm species acting as a source of infection.

Salmonella in slaughter pigs in Northern Ireland: prevalence and use of statistical modelling to investigate sample and abattoir effects

A cross-sectional survey of pigs at slaughter in Northern Ireland was undertaken to determine the overall prevalence of Salmonella infection. In total 513 pigs were sampled across four abattoirs, with Salmonella spp. isolated from the caecal contents of 31.4% (95% confidence interval [CI] 27.4%-35.4%) and from 40.0% (95% CI 35.8%-44.3%) of swabs taken from the surface of carcasses post-evisceration. Two serovars, S. Typhimurium and S. Derby, were predominant and accounted for 52% and 35% respectively, of isolates from caecal contents. Antimicrobial resistance was most common amongst isolates of S. Typhimurium with 63.9% multiresistant compared to 10.8% of S. Derby isolates and 8.0% of other Salmonella spp. The proportion of pigs showing serological evidence of infection was significantly lower, with 11.5% (95% CI 8.9%-14.6%) and 10.1% (95% CI 7.7%-13.1%) of meat-juice samples giving positive and suspect reactions, respectively. The ratio of caecal positive to serologically positive animals is higher than in a number of other studies and may suggest recent infection, such as infection occurring during transport or lairage, in a proportion of animals. Statistical (logistic regression) modelling was used to investigate the association between the risk of Salmonella on carcasses and the isolation of Salmonella from caecal contents, and/or the serological status of the animal, while adjusting for other possible explanatory and confounding variables such as abattoir, season, day and time of sampling. The occurrence of Salmonella in caecal contents (odds ratio [OR] 2.39; 95% CI 1.52-3.77) or a suspect/positive serological reaction (OR 2.15; 95% CI 1.28-3.61) were both independently associated with the occurrence of Salmonella on carcasses in homebred, but interestingly not in imported animals. In most multivariable models there were also significant differences in carcass contamination between seasons with the highest odds of carcass contamination occurring in the April to June quarter and the lowest in the October to December quarter. Differences between sampling days were also evident with the highest odds of carcass contamination at the end of the week (Fridays) and the lowest at the start of the week (Mondays). These associations, after adjusting for the caecal or serological result, would suggest the occurrence of abattoir effects, such varying residual levels of abattoir contamination, which are independent of the individual pig status.

Molecular analyses of mycobacteria other than the M. tuberculosis complex isolated from Northern Ireland cattle

Mycobacteria other than the Mycobacterium tuberculosis complex (MOTT), isolated from Northern Ireland cattle, were identified by PCR amplification of the 16S rRNA gene, and subsequent reverse cross blot hybridisation and sequence analyses. Elucidation of the MOTT species was to facilitate specificity testing of new and existing diagnostic test reagents for bovine tuberculosis. The presence of the genes for potential diagnostic antigens: MPB70, MPB64, ESAT-6 and CFP-10 in the isolated MOTT species was investigated. Molecular analyses of cultured isolates from bovine lymph node specimens of 48 cattle identified a wide variety of mycobacterial species including Mycobacterium nonchromogenicum, Mycobacterium malmoense, Mycobacterium bohemicum, Mycobacterium paratuberculosis, Mycobacterium avium, Mycobacterium kansasii, Mycobacterium holsaticum, Mycobacterium palustre, Mycobacterium sp. IWGMT 90210, Mycobacterium sp. LIV-2129, a potentially novel mycobacterial species (EMBL/GenBank/DDBJ Accession Number AJ617495) and Rhodococcus equi. Apart from M. kansasii, the results of traditional (standard phenotypic and biochemical) and molecular identification methods did not correlate well, with traditional methods identifying fewer species. Most of the species identified were either recognised pathogenic or potential pathogenic species. The genes for ESAT-6, CFP-10 and, unusually, MPB64 were detected in M. kansasii only. The MPB70 gene was not detected in any of the species. This study supported restricted species distribution of these genes as well as identifying a different range of MOTT species that could be included in specificity testing of new diagnostic reagents for bovine tuberculosis.

PCR studies of feline leprosy cases

16S rRNA gene sequence analysis provided evidence for two different mycobacterial species, Mycobacterium lepraemurium and a potentially novel species, as causative agents of 'feline leprosy'. Comparison of 16S rRNA gene sequence data obtained for M. lepraemurium and the potentially novel species indicated 12 nucleotide differences over a 446 bp region encompassing the V2 and V3 hypervariable regions. From available 16S rRNA gene sequence data, M. lepraemurium shared greatest nucleotide identity with M. avium subsp paratuberculosis and M. avium. The novel species had a long helix 18 in the V3 region and shared greatest nucleotide identity with M. leprae, M. haemophilum and M. malmoense. The novel species had an additional 'A' nucleotide at position 105 of the aligned 16S rRNA gene sequence, the only other mycobacterial database sequence having this same extra nucleotide being M. leprae. This nucleotide variation was exploited to develop specific PCR assays for the two species. These were found to be effective and specific when tested against a panel of mycobacteria including species found in feline leprosy lesions and closely related mycobacteria and also when applied directly to formalin-fixed, paraffin-embedded tissues from feline leprosy cases.

Bovine tuberculosis: an old disease but a new threat to Africa

Bovine tuberculosis (TB) is a disease characterised by progressive development of specific granulomatous lesions or tubercles in lung tissue, lymph nodes or other organs. Mycobacterium bovis is the causative agent of the disease. Bovine species, including bison and buffaloes, are susceptible to the disease, but nearly all warm-blooded animals can be affected. All species are not equally susceptible to the disease; some are spill-over (end) hosts and others maintenance hosts. In Africa, bovine TB primarily affects cattle; however, infection in other farm and domestic animals, such as sheep, goats, pigs, dogs and cats, is not uncommon. Wild ruminants and carnivores are also affected and are the natural reservoirs of the infectious agent in the wild. Man is also susceptible to the disease, the highest risk groups being individuals with concomitant HIV/AIDS infection. In Africa, human TB is widely known to be caused by M. tuberculosis; however, an unknown proportion of cases are due to M. bovis. This infection in humans is under-reported as a result of the diagnostic limitations of many laboratories in distinguishing M. bovis from M. tuberculosis. None of the national reports submitted to the OIE and WHO by African member states mention the importance of M. bovis in human TB cases. Consumption of unpasteurised milk and poorly heat-treated meat and close contact with infected animals represent the main sources of infection for humans. This review attempts to examine the impact of bovine TB on the health of animals and humans.

Mycobacterium nonchromogenicum in nasal mucus from cattle in a herd infected with bovine tuberculosis

Skin test negative cattle from a herd containing an unusually high proportion (194/382) of tuberculin skin test positive cattle were investigated for remaining Mycobacterium bovis infected animals. Blood samples from the skin test negative cattle, analysed by an antibody ELISA and an interferon-gamma assay, were mostly test negative for M. bovis. Radiometric culture of nasal mucus samples from 48 of the cattle yielded 22 culture positives with acid-fast bacilli and cording in 6 of these. Subculture on solid media was successful for 7, including 2 with cording of the 22 radiometric culture positives. Mycobacterium tuberculosis complex DNA probe testing using the Accuprobe (Gen-Probe, Inc.) and M. tuberculosis complex-specific PCR amplification, performed on the solid media subcultures, were negative. 16S rRNA PCR and sequence analysis were successful for 6 of the 7 solid media subcultures obtained and revealed the presence of Mycobacterium nonchromogenicum in all 6 subcultures. This is the first report of M. nonchromogenicum in nasal mucus of cattle. The observation highlights the importance of integrating definitive tests such as the PCR for diagnosis of bovine tuberculosis and indicates a possible zoonotic risk.

Antimicrobial susceptibility of Campylobacter spp. isolated from broiler chickens in Northern Ireland

Between February 2000 and October 2001, cloacal swabs were collected from 387 broiler chicken flocks in Northern Ireland. Campylobacter isolates from the 262 positive flocks were tested with common antimicrobial agents using a disc diffusion method and by Etests. Resistance to erythromycin, gentamicin and chloramphenicol was <1%, whereas for ampicillin, nalidixic acid and tetracycline, resistance was 33%, 10% and 13%, respectively. Ciprofloxacin resistance was 3%, one of the lowest in recent reports from studies on human or poultry isolates. Sequence data of the quinolone resistance-determining region of the gyrA gene showed a mutation leading to Thr-86 to Ile substitution among highly resistant ciprofloxacin isolates. Only 0.8% of the isolates studied were resistant to four or more antibiotics.

Mycobacterium bovis infection and tuberculosis in cattle

This review considers the possible events that can occur when cattle are exposed to Mycobacterium bovis and, where appropriate, draws on principles accepted for tuberculosis infection in humans and laboratory animal models. Consideration is given to the many complex factors which influence the outcome of challenge with tubercle bacilli. These include features inherent to the mycobacterium, the host and the environment. It is apparent that clinical disease probably occurs only in a relatively small, but undetermined, proportion of cattle that are exposed to Al. bovis. The majority of animals may clear infection or control the bacilli, possibly in a condition of latency. It is concluded that a better understanding of the dynamics of the events following M. bovis exposure and subsequent infection in cattle would be of significant benefit in developing new tools appropriate for disease control and to designing optimal approaches for their application.

Molecular epidemiology of Mycobacterium bovis: exploiting molecular data

'Molecular epidemiology' is defined as the integration of conventional epidemiological approaches with molecular techniques to track specific strains of pathogens in order to understand the distribution of disease in populations. It has become a very powerful tool in the study of Mycobacterium tuberculosis and human tuberculosis, where it has been exploited to provide 'added value' to conventional epidemiological approaches (contact tracing) and has often challenged accepted dogmas. It has been used to confirm epidemiologically suspected transmission, to detect epidemiologically unsuspected transmission, to identify risk factors and environments where transmission is occurring, to detect laboratory errors and to monitor the efficacy of tuberculosis control programmes. For Mycobacterium bovis and bovine tuberculosis, molecular epidemiology has a key role to play in providing more precise epidemiological data on the issues of interbovine transmission and the role of wildlife reservoirs in disease maintenance and transmission. M. bovis strains may also differ in key biological properties, such as virulence, transmissibility, stability and antigenic variation, which may help to explain field observations. There may be correlation between strain type and 'herd level' factors such as breakdown size etc. Molecular 'strain typing' studies have provided useful information in several countries, notably New Zealand, where strain typing data is used as an integral part of M. bovis control schemes, to influence the level of herd testing or wildlife control and to define the extent and spread of infected wildlife. This presentation will review the methods and approaches currently appropriate for M. bovis strain typing and will review selected applications as well as discussing future perspectives and challenges for the application of molecular epidemiology to bovine tuberculosis.

Immune responses in bovine tuberculosis

Knowledge of the immune responses which develop in cattle following infection with Mycobacterium bovis is essential both to the understanding of disease pathogenesis and to the logical development of immune-dependent tools, such as diagnostic tests and vaccines, which can be used to combat the disease. Studies of field cases of bovine tuberculosis (TB) and of experimental bovine models of M. bovis infection have indicated that cell-mediated immune responses (CMI) predominate within a spectrum of immunity which exists. This paper reviews aspects of recent research and indicates how knowledge of T-cell antigenic targets in bovine TB along with increasing knowledge of T-cell subpopulations and their interactions with M. bovis -infected macrophages provides opportunities for the development of better methods for disease control.

Pathogenesis of tuberculosis in cattle

There has been a renewed interest in the pathogenesis of bovine tuberculosis in many countries, in an attempt to understand better its transmission, to improve diagnosis and assess the potential of vaccination. This paper, which overviews current knowledge of aspects of the pathogenesis of bovine tuberculosis, draws from studies of field cases and experimental infections and highlights deficiencies in current understanding. The pathogenesis of bovine tuberculosis has not received the same level of attention as with human tuberculosis, and in many instances, the processes involved in bovine tuberculosis have been drawn from studies of human tuberculosis or from small animal models of infection. This paper however, considers the successful emulation of naturally acquired tuberculosis using experimental cattle models and identifies the complex and integrated nature of microbiological, immunological and pathological events involved. Current understanding of the initiation of infection, immune responses, and subsequent pathology, which can vary significantly in individual animals are discussed. Whilst there are aspects of M. bovis that still remain elusive to scientific investigation, further studies on the pathogenesis of bovine tuberculosis are advocated as necessary to provide a better scientific basis on which to review control and eradication strategies, which are currently less than effective in many regions.

Detection of Mycobacterium bovis in bovine clinical specimens using real-time fluorescence and fluorescence resonance energy transfer probe rapid-cycle PCR

Nucleic acid sequence capture extraction was coupled with LightCycler PCR amplification and product detection using real-time fluorescence for rapid, definitive detection of Mycobacterium bovis in lymph node specimens from 38 cattle with bovine tuberculosis lesions. PCR amplification of sequence-captured DNA using both a conventional heating block thermocycler and a LightCycler thermocycler was compared with culture and histopathological analyses. Conventional PCR enabled detection of 26 of 28 culture-positive specimens (93%) in approximately 9 h, and the LightCycler PCR detected 20 of 28 culture-positive specimens (71%) in only 30 min. Specific confirmation of Mycobacterium tuberculosis complex DNA was achieved by LightCycler PCR amplification using Syb Green 1 and an M. tuberculosis complex-specific Cy5-labeled fluorescence resonance energy transfer probe. The system described here enabled rapid and specific laboratory confirmation of bovine tuberculosis, and this is the first report of the detection of M. bovis in tissues using LightCycler PCR. The fluorescence technology used in the study has potential to allow development of a high-throughput molecular diagnostic test for bovine tuberculosis.

Lymphocyte subtypes in experimentally induced early-stage bovine tuberculous lesions

The identity of the lymphocyte subtypes constituting the lymphocytic mantle within developing early-stage lesions of bovine tuberculosis was investigated immunohistochemically in calves inoculated intranasally with 2 x 10(7) colony-forming units of a field isolate of Mycobacterium bovis. Pulmonary lesions were examined 7, 14, 21, 28 and 42 days after inoculation, and bronchial lymph node lesions at 35 days. The immunolabelling results reported were obtained with monoclonal antibodies against two T-cell epitopes (WC1+ gamma delta and CD2+) and against B-cell epitopes. Large numbers of CD2+ T-lymphocytes were observed around developing areas of necrosis throughout the study; WC1+ gamma delta cells, however, were more numerous at these sites up to and including day 21. On the other hand, aggregates of B lymphocytes did not become prominent in areas adjacent to lesions until day 42. The results suggest that these lymphocyte phenotypes play a role in the pathogenesis of early-stage lesions.

Dominant-negative polo-like kinase 1 induces mitotic catastrophe independent of cdc25C function

Polo-like kinase 1 (PLK1), which has been shown to have a critical role in mitosis, is one possible target for cancer therapeutic intervention. PLK1, at least in Xenopus, starts the mitotic cascade by phosphorylating and activating cdc25C phosphatase. Also, loss of PLK1 function has been shown to induce mitotic catastrophe in a HeLa cervical carcinoma cell line but not in normal Hs68 fibroblasts. We wanted to understand whether the selective mitotic catastrophe in HeLa cells could be extended to other tumor types, and, if so, whether it could be attributable to a tumor-specific loss of dependence on PLK1 for cdc25C activation. When PLK1 function was blocked through adenovirus delivery of a dominant-negative gene, we observed tumor-selective apoptosis in most tumor cell lines. In some lines, dominant-negative PLK1 induced a mitotic catastrophe similar to that published in HeLa cells (K. E. Mundt et al., Biochem. Biophys Res. Commun., 239: 377-385, 1997). Normal human mammary epithelial cells, although arrested in mitosis, appeared to escape the loss of centrosome maturation and mitotic catastrophe seen in tumor lines. Mitotic phosphorylation of cdc25C and activation of cdk1 was blocked by dominant-negative PLK1 in human mammary epithelial cells as well as in the tumor lines regardless of whether they underwent mitotic catastrophe. These data strongly argue that the mitotic catastrophe is not attributable to a lack of dependence for PLK1 in activating cdc25C.

Cattle-to-cattle transmission of bovine tuberculosis

In developed countries, Mycobacterium bovis infection in cattle is now mostly confined to the respiratory system, which reflects transmission and establishment of infection mainly by this route. A single bacillus transported within a droplet nucleus is probably sufficient to establish infection within the bovine lung. Infected cattle should always be considered as potential sources of infection, since studies have demonstrated that a significant proportion of tuberculous cattle excrete M. bovis. In general, the dynamics of M. bovis transmission are poorly understood and the conditions under which a tuberculous animal becomes an effective disseminator of infection are currently not defined although environmental contamination appears to be a less effective method of disease transmission. Field studies indicate a wide spectrum of transmission rates but generally the spread of M. bovis infection is still considered to be a relatively slow process. Slaughter of diseased cattle detected by tuberculin testing and at meat plant inspection has been shown to be an effective policy for tuberculosis eradication, provided there are no other reservoirs of infection and all involved in the cattle industry are committed to a policy of eradication. Epidemiological approaches, particularly case-control studies, seem to provide the best method for quantifying the relative importance of the various sources of M. bovis transmission to cattle and modelling techniques can be used to assist in the design of cost-effective control measures that may lead to tuberculosis eradication.

IgG isotype antibody responses to epitopes of the Mycobacterium bovis protein MPB70 in immunised and in tuberculin skin test-reactor cattle

Serological assays may have merit in identifying animals in advanced stages of bovine tuberculosis, but most tests have had sub-optimal sensitivities and specificities. The Mycobacterium bovis protein MPB70 has been identified as a B-cell target with diagnostic potential in measurement of pre- and post-skin-test antibody responses. One observation, which has potential practical application, has been that skin testing with tuberculin boosts IgG(1) anti-MPB70 antibody responses in cattle with tuberculous lesions. However, serological cross-reactivities with bacteria, such as Nocardia asteroides, have been described for this protein. With the aim of identifying candidate reagents for improved diagnostic tests, this study investigated IgG isotype antibody responses to MPB70 at the epitope level and, because of the previous findings, focused on IgG(1) responses following skin testing. Screening of a panel of overlapping synthetic peptides using sera from cattle immunised with MPB70 and cattle infected with M. bovis showed that two regions of the protein (residues 21-70 and 101-120) contain dominant B-cell epitopes. No individual epitope appeared to be selectively recognised by one isotype of IgG antibody. Investigation of IgG(1) responses showed that recognition of the epitope within residues 51-70 was boosted strongly by tuberculin injections in skin-test positive cattle and that this memory response was generally a feature of cattle which were found to have macroscopic, tuberculous lesions.

Assessment of defined antigens for the diagnosis of bovine tuberculosis in skin test-reactor cattle

The continued use of purified protein derivative (PPD) tuberculin is considered to be the main factor which limits the specificity of diagnostic tests for bovine tuberculosis (TB). This study evaluated a whole blood interferon-gamma (IFN-gamma) assay and compared the diagnostic potential of PPD with two tuberculosis-specific antigens, ESAT-6 and MPB70. To provide estimates of sensitivity and specificity, responses were measured in 180 skin test-reacting cattle, of which 131 were confirmed as tuberculous, and in 128 cattle from TB-free herds. For the skin test reactors, there was a positive correlation between the IFN-gamma responses to PPD from Mycobacterium bovis (PPDB) and PPD from Mycobacterium avium (PPDA), indicating cross-reactivity between these complex antigens which are the basis of the skin test. In comparisons of the ESAT-6 IFN-gamma test with a PPD IFN-gamma test (using PPDB compared with PPDA), there was a decrease in sensitivity (76.3 per cent vs 89.3 per cent), but a clear increase in specificity (99.2 per cent vs 92.2 per cent). The provision of high specificity, even with lower sensitivity, offers major benefits for testing in areas with a low incidence of TB.

In vitro T-cell activation of monocyte-derived macrophages by soluble messengers or cell-to-cell contact in bovine tuberculosis

The macrophage plays a dual role in tuberculosis, promoting not only protection against mycobacteria, but also survival of the pathogen. Macrophages inhibit multiplication of mycobacteria but also act in concert with lymphocytes through presentation of antigens to T cells. Studies in animal and human infections have suggested a correlation of in vitro growth rates of mycobacteria with in vivo virulence, using uracil uptake to assess mycobacterial metabolism. This study found that blood-derived, non-activated bovine macrophages were capable of controlling Mycobacterium bovis bacillus Calmette-Gurin growth for up to 96 hr, but were permissive to intracellular growth of virulent M. bovis. The present investigation compared the in vitro modulation of these macrophage activities by cytokine-rich T-cell supernatants or cell-to-cell contact. On the one hand, treatment of cultured monocytes with mitogen-produced T-cell supernatants promoted morphological changes suggestive of an activation status, enhanced the antigen presentation capabilities of monocytes and up-regulated major histocompatibility complex class II expression. However, this activation was not associated with enhanced anti-M. bovis activity. On the other hand, incubation of infected monocytes with T-cell populations resulted in proportionally increased inhibition of M. bovis uracil uptake. This inhibition was also seen using cells from uninfected animals and indicated the necessity for cell-to-cell contact to promote antimycobacterial capability.

Simultaneous detection and strain differentiation of Mycobacterium bovis directly from bovine tissue specimens by spoligotyping

Culture of Mycobacterium bovis is used routinely to support field diagnosis of bovine tuberculosis; however, this method is slow. Rapid detection and strain-typing of M. bovis directly from 37 lesioned bovine lymph node specimens was performed by the polymerase chain reaction (PCR) based method, spoligotyping. Mycobacterial DNA was extracted from the specimens using a nucleic acid sequence capture technique. Two sets of specimens were tested, the first set comprising 16 decontaminated tissue homogenates from lesioned lymph node specimens which had been processed for BACTEC culture and a second set of 21 non-decontaminated lesioned lymph node specimens. Both sets of specimens had been frozen before analysis. Sequence capture PCR enabled detection and strain-typing of M. bovis directly from 15 of the 16 decontaminated homogenates and all 21 of the non-decontaminated tissues. Four spoligotype (ST) patterns were obtained from each set; ST1, ST2, ST3 and ST16 were detected in the decontaminated specimens and ST1, ST2, ST11 and ST14 in the non-decontaminated specimens. For both sets of specimens, ST1 was the predominant strain type detected. ST patterns obtained from the BACTEC cultures of the decontaminated specimens were in agreement with those obtained directly from the tissue. The sensitivity of detection by sequence capture-PCR compared very favourably with that of BACTEC culture. ST patterns were obtained directly from tissues of 34 of the 35 culture positive specimens and the two culture negative specimens. DNA extraction from the 21 non-decontaminated specimens involved an initial stomaching treatment. An assessment of sequence capture on both liquid alone and liquid and tissue homogenate combined, following stomaching, indicated that PCR was less successful on the liquid component alone.

Cellular interactions in bovine tuberculosis: release of active mycobacteria from infected macrophages by antigen-stimulated T cells

The outcome of Mycobacterium bovis infections depends on the interactions of infected macrophages with T lymphocytes. Several studies in humans and in mouse models have suggested an important role for cytotoxicity in the protective immune response to mycobacterial infections, and both CD4+ and CD8+ T cells have been shown to elicit appropriate cytolytic activity. The present study investigated in vitro interactions of T cells with M. bovis-infected macrophages in bovine tuberculosis. The results showed that following interaction with antigen-stimulated peripheral blood mononuclear cells (PBMC) from infected cattle, there was an increased presence of M. bovis in the extracellular compartment of infected macrophage cultures, as measured by incorporation of [3H]uracil into mycobacterial RNA. Furthermore, out of a panel of T-cell clones from infected cattle, it was found that a higher proportion of CD8+ clones produced an increase in the number of metabolically active extracellular M. bovis organisms compared with CD4+ clones. Finally, a positive correlation between percentage of antigen-dependent release of mycobacteria and total uracil uptake by M. bovis within culture systems was detected. This could be regarded as an indication of preferential intracellular control of mycobacteria by activated macrophages.

Lesions in cattle exposed to Mycobacterium bovis-inoculated calves

Nine calves were housed for periods ranging from 24 to 117 days in close contact with cattle inoculated intranasally with Mycobacterium bovis. These "in-contact" calves were examined immunologically and bacteriologically during the period of exposure, and pathologically and immunocytochemically post mortem. Three became infected by day 14, as indicated by the detection of M. bovis in nasal mucus. In-vitro interferon-gamma production and lymphocyte proliferation were detected after stimulation of peripheral blood with M. bovis antigens in the majority of in-contact animals by day 28; this provided support for the role of immunological mechanisms in pathogenesis. Tuberculous lesions were found in the submandibular and bronchomediastinal lymph nodes and in the lungs of the in-contact calves; in distribution and appearance the lesions resembled those observed in naturally occurring disease. The distribution of M. bovis antigen and the numbers of mycobacteria within pulmonary lesions are reported. 1999 Harcourt Publishers Ltd.

Generation of CD8(+) T-cell responses to Mycobacterium bovis and mycobacterial antigen in experimental bovine tuberculosis

Protective immunity against tuberculosis is considered to be essentially cell mediated, and an important role for CD8(+) T lymphocytes has been suggested by several studies of murine and human infections. The present work, using an experimental model of infection with Mycobacterium bovis in cattle, showed that live M. bovis elicits the activation of CD8(+) T cells in vitro. However, a sonic extract prepared from M. bovis (MBSE) and protein purified derivative (PPDb) also induced a considerable degree of activation of the CD8(+) T cells. Analysis of proliferative responses of peripheral blood mononuclear cells, purified CD8(+) T cells, and CD8(+) T-cell clones to M. bovis and to soluble antigenic preparations (MBSE, PPDb) showed that the responses of all three types of cells were always superior for live mycobacteria but that strong responses were also obtained with complex soluble preparations. Furthermore, while cytotoxic capabilities were not investigated, the CD8(+) T cells were found to produce and release gamma interferon in response to antigen (live and soluble), which indicated one possible protective mechanism for these cells in bovine tuberculosis. Finally, it was demonstrated by metabolic inhibition with brefeldin A and cytochalasin D at the clonal level that an endogenous pathway of antigen processing is required for presentation to bovine CD8(+) cells and that presentation is also dependent on phagocytosis of the antigen.

Tonsillar lesions in cattle naturally infected with Mycobacterium bovis

The upper respiratory tract surfaces, the palatine and pharyngeal tonsils and associated lymph nodes of 32 tuberculin reactor cattle were examined pathologically and bacteriologically. Tuberculous lesions were observed histologically in the palatine tonsils of five animals and in both the palatine and pharyngeal tonsils of a sixth. Mycobacterium bovis was cultured from the tonsils of four of these animals and from the palatine or pharyngeal tonsils of a further eight cattle in which no lesions were observed. The upper respiratory tract surfaces of 10 animals were M bovis-positive.

Early lesion formation in cattle experimentally infected with Mycobacterium bovis

Early lesion formation was examined in 13 calves inoculated intranasally with 2 x 10(7) colony-forming units of Mycobacterium bovis and killed either singly or in pairs at intervals of < or = 7 days from post-inoculation day (pid) 3 to pid 42. Immunological examinations were carried out before and after infection, and sequential necropsies were performed. M. bovis was recovered as early as pid 3, from the upper respiratory tract mucosae, retropharyngeal lymph nodes and caudal lung lobe. Gross tuberculous lesions were detected in both the upper respiratory tract mucosae and in the lungs of the calves killed from pid 14 onwards. Lesions were also present in the lymph nodes draining these areas. On histological examination, neutrophils appeared to play a key role in the earliest stages of lesion formation, and lesion mineralization was observed for the first time at pid 35. The contemporaneous development of lesions and cellular immunity, as demonstrated by in-vitro lymphocyte proliferation and interferon-gamma assay responses, provided further evidence of the role of immunopathogenic mechanisms in the development of bovine tuberculosis.

T-cell recognition of mycobacterial proteins MPB70 and MPB64 in cattle immunized with antigen and infected with Mycobacterium bovis

Defined antigenic reagents and knowledge of T-cell responses are required for the design of improved diagnostic tests for bovine tuberculosis. The limited species distribution of Mycobacterium bovis antigens MPB70 and MPB64 has indicated their potential for inclusion in future tests. The strategy adopted in this study was to define bovine T-cell responses to these antigens at the epitope level, using cattle immunized with recombinant forms of the antigens, and to compare these responses with cattle which had been experimentally infected with M. bovis. Panels of synthetic peptides (20-mers with 10-residue overlaps) were used and five epitopes were identified and found to be powerful stimulators of T-cell responses in both types of animal (residues 81-100 and 174-190 for MPB70, and residues 1-20, 41-60 and 181-200 for MPB64). Further investigation in larger numbers of cattle (n = 14) of mixed breeds from tuberculosis-infected herds confirmed that each peptide produced response in several of the cattle, but no single peptide was recognized by all animals. However, the limited numbers of animals in this study suggest that peptide reagents may identify as many positive animals as the intact antigenic protein and could form components of a future diagnostic test. The use of cattle immunized with the proteins of interest has proved to be an interesting model for studying the nature of bovine T-cell responses to defined mycobacterial proteins.

Mycobacterial antigen-specific antibody responses in bovine tuberculosis: an ELISA with potential to confirm disease status

Serological assays may help to identify animals in advanced stages of bovine tuberculosis, but most of the tests available have suboptimal sensitivities and specificities. This study was designed to determine whether the antibody responses to defined antigens (rMPB70, rMPB64 and rMPB59) of Mycobacterium bovis at the immunoglobulin subclass level could be used to develop improved serological tests. In experimentally infected cattle it was found that the predominant serum antibody response was to rMPB70, and that an IgG1 response to this antigen was boosted strongly by skin testing. Studies in naturally infected cattle suggested that this memory IgG1 anti-rMPB70 response may be able to differentiate between skin test-reactor animals with and without lesions by comparing the ratio of the antibody response before and after skin testing. The study has provided a clearer understanding of the kinetics of antibody responses to defined mycobacterial antigens at the subclass level in bovine tuberculosis and has made it possible to develop a novel ELISA system which may be useful in disease diagnosis.

Rapid diagnosis and strain differentiation of Mycobacterium bovis in radiometric culture by spoligotyping

An assessment of spoligotyping for rapid detection and strain typing of Mycobacterium bovis isolates in radiometric culture was made. Spoligotyping was applied to BACTEC 12B broth cultures of 54 lesioned bovine lymph node specimens from 44 herds in Northern Ireland. A nucleic acid sequence capture technique was performed on BACTEC cultures at growth index points of approximately (approximately) 60, approximately 200, and 999. Definitive spoligotype patterns were obtained for 90.4% and 94.2% of all 52 BACTEC culture-positives at growth indexes approximately 60 and approximately 200, respectively. Within 10 days, definitive spoligotype patterns were obtained for 84.6% of the culture-positives. This technique, therefore, allowed earlier and more accurate diagnosis of M. bovis than traditional methodologies, as well as simultaneous strain differentiation. Application of this molecular tool to BACTEC cultures would be a significant advance in bovine tuberculosis eradication programmes. Seven distinct spoligotype patterns were identified in this study, 2 of which (ST21 and ST25), had not been identified previously in cattle from Northern Ireland. Two spoligotype patterns (ST1 and ST2) accounted for 80.7% of the culture-positives. These were found to have widespread geographic distribution, whereas 1 spoligotype pattern (ST14) had limited geographical distribution.

Spacer oligotyping of Mycobacterium bovis isolates compared to typing by restriction fragment length polymorphism using PGRS, DR and IS6110 probes

Ninety-two Mycobacterium bovis isolates from cattle, deer and badgers in Northern Ireland and the Republic of Ireland were genotyped by spacer-oligotyping (spoligotyping) and 67 of these were analysed by restriction fragment length polymorphism (RFLP). RFLP analysis was performed using three DNA probes, PGRS, DR and IS6110. Forty-seven of the M. bovis isolates were from 45 different sources; these were typed using both RFLP and spoligotyping. These 47 isolates could be differentiated into 24 different RFLP types and 15 distinct spoligotypes. Although RFLP was found to be more discriminatory compared to the present spoligotyping technique, spoligotyping was able to differentiate 21 RFLP type 'ACA' isolates into three different patterns. The remaining 45 M. bovis isolates were from a small case study, involving infected cattle, deer and badgers from the same geographic region. All these isolates were analysed by spoligotyping and a selection of 20 isolates were RFLP typed. All the isolates in the case study had the same spoligotype pattern with the exception of one cervine isolate. Similarly all the isolates typed by RFLP had the same pattern. Consequently, the predominant strain in the case study was not host restricted. The consistency between the results obtained using the two techniques indicates the potential value of both techniques for epidemiological studies. Spoligotyping was found to be a much more rapid technique and easier to perform, requiring less sophisticated computer software for strain typing. Spoligotyping results were more readily documented and analysed and the technique was also more suitable than RFLP analysis for large-scale screening studies.

Recognition of a common mycobacterial T-cell epitope in MPB59 of Mycobacterium bovis

Bovine tuberculosis, which persists as a residual level of infection in many European countries, has implications not only for the economy of farming communities but also for human health. The aim of this study was to identify a common mycobacterial antigen which was recognized in bovine tuberculosis and to characterize the response to this antigen at the epitope level. A T-cell clone, phenotype CD4+, raised from an animal experimentally infected with Mycobacterium bovis was shown to proliferate in response to a panel of sonicates derived from different mycobacterial species indicating recognition of an antigen with broad specificity. This antigen was subsequently shown to be MPB59. Recognition of MPB59 at the epitope level was determined in experimental and field cases of bovine tuberculosis using a panel of synthetic peptides (20-mers with 10-residue overlaps) incorporating the signal sequence and mature protein. The results showed that in vitro interferon-gamma was predominantly produced in response to adjacent peptides numbers 10 and 11, suggesting that the dominant epitope was contained in the overlap, correlating to residues 101-110 (YYQSGLSIVM). This epitope was recognized by 54% of tuberculous cattle of mixed breeds, which suggests that it may be genetically permissive in terms of major histocompatibility complex presentation. Sequence analysis confirmed that there were only minor differences in the amino acid composition within this region for various mycobacterial species, which could explain the common T-cell recognition described in this study. Common recognition of this epitope indicates that it would have limited potential for use as a diagnostic reagent per se but may have potential for inclusion in a subunit vaccine.

Development of mycobacterial species-specific DNA probes by subtraction hybridization

Subtraction hybridization was used to identify sequences of Mycobacterium bovis DNA which might be of diagnostic value. Genomic DNA from Mycobacterium avium, isolated commonly from cattle and whose tuberculin is used in the comparative intradermal tuberculin test, was subtracted from M. bovis genomic DNA. A novel sequence, of 131 bp, which appears to be Mycobacterium tuberculosis complex-specific was identified. The specificity of this sequence was stringently tested by a probe and polymerase chain reaction (PCR) assay. Nucleotide identity determination and sequence comparisons revealed that the 131-bp sequence is located directly upstream of a potential isocitrate dehydrogenase (IDH) coding gene and may be of diagnostic value, enabling differentiation of M. tuberculosis complex mycobacteria from other mycobacterial species.

Determination of the etiology of presumptive feline leprosy by 16S rRNA gene analysis

PCR-amplified 16S rRNA gene sequences were obtained directly from tissue specimens from eight cats with presumptive feline leprosy. Acid-fast bacilli were observed in sections from all eight specimens, but culture for mycobacteria was successful for one specimen only. Analysis of the V2 variable region of each 16S rRNA PCR product identified a sequence with 100% nucleotide identity to the sequences of Mycobacterium lepraemurium, Mycobacterium avium, and Mycobacterium paratuberculosis in four of the specimens from cats with feline leprosy. Separate M. paratuberculosis- and M. avium-specific PCR amplifications of the four specimens were negative, thus substantiating the identification of M. lepraemurium in these specimens from cats with feline leprosy. Further sequence analysis of the V3 variable region of one of the four specimens provided conclusive evidence of the presence of M. lepraemurium. This is the first report of the definitive identification of M. lepraemurium in cats with feline leprosy by molecular biology-based analyses. M. avium, which is rarely reported in cats, and Mycobacterium chitae, a reported nonpathogenic, rapidly growing mycobacterial species found in the environment, were identified in the specimen from which acid-fast bacilli were cultured. Two of the specimens from cats were infected with a potentially novel species of mycobacteria which had a 16S rRNA gene sequence sharing the closest nucleotide sequence identity with that of Mycobacterium malmoense. Molecular biology-based analyses provided for the accurate and rapid diagnosis of mycobacterial infections in cats and circumvented the problems of culture and misdiagnosis of feline leprosy associated with traditional methods.

Differentiation of Mycobacterium bovis isolates from animals by DNA typing

The insertion sequence IS6110 and the direct repeat (DR) specific to tuberculosis complex mycobacteria and the highly repeated DNA sequence, the polymorphic GC-rich repeat sequence (PGRS), were systematically used to identify restriction fragment length polymorphisms (RFLPs) within 210 isolates of Mycobacterium bovis. The isolates were primarily of bovine origin, but isolates from badgers, feral deer, sheep, humans, and a pig were included. The RFLP probes IS6110, DR, and PGRS individually identified 17, 18, and 18 different RFLP types, respectively, but in combination these probes identified a total of 39 different M. bovis RFLP types. The recommendations (J. D. A. van Embden, M. D. Cave, J. T. Crawford, J. W. Dale, K. D. Eisenach, B. Gicquel, P. W. M. Hermans, C. Martin, R. McAdam, T. M. Shinnick, and P. M. Small, J. Clin. Microbiol. 31:406-409, 1993) for a standardized RFLP analysis for M. tuberculosis were adapted to facilitate gel documentation, image analysis, and construction of a database of RFLP types. In the present study the same M. bovis RFLP types were evident in the various animal species included, indicating that the strains were not host restricted. Application of these techniques to defined field studies should help elucidate more accurately aspects of the epidemiology of bovine tuberculosis in different countries.

Vaccination of the badger (Meles meles) against Mycobacterium bovis

This review summarizes current knowledge relating to the potential development of a vaccine against Mycobacterium bovis (M. bovis) for use in badgers. The serious economic loss incurred from bovine tuberculosis in Ireland is highlighted. The problems presented to national bovine tuberculosis eradication programmes by wildlife reservoirs of M bovis, in particular the badger and the brushtail possum, are outlined. Badger and possum ecology and the epidemiology of M. bovis infection in these species are compared in relation to control strategies. Current information regarding the immune responses of badgers and possums to M. bovis infection is presented. Vaccine types, carrier and adjuvant systems, available vaccines for human and animal tuberculosis and delivery to wildlife species are described. The feasibility of vaccinating badgers against M. bovis infection and the possible options for a vaccination strategy are discussed.

Dynamic changes in circulating and antigen-responsive T-cell subpopulations post-Mycobacterium bovis infection in cattle

Bovine tuberculosis is a threat to animal and human health in several countries. Greater understanding of the immunology of the disease is required to develop improved tests and vaccines. This study has used a model of bovine tuberculosis, established in the natural host, to investigate the dynamic changes that occur in the circulating T-cell subpopulations after infection. When the phenotypic composition of the peripheral blood lymphocytes was determined pre- and post-experimental infection, the response to disease comprised three phases. Firstly, the WC1/gamma delta T cells decreased and then increased, suggesting localization to developing lesions and clonal expansion. Secondly, the CD4:CD8 ratio increased. Thirdly, the CD4:CD8 ratio decreased to less than pre-infection measurements. The latter changes suggested sequential involvement of CD4 and then CD8 T cells. The proportion of cells expressing interleukin-2 receptor (IL-2R) also increased. Panels of T-cell clones were established at various stages post-infection and all clones that exhibited antigen responsiveness were phenotyped. T-cell clones from early infection were WC1/gamma delta and CD4 in phenotype, while CD8 clones appeared later in infection, eventually becoming dominant. Therefore, from in vivo and in vitro evidence, it was suggested that there is a dynamic progression in the T-cell subpopulations involved dominantly in responses to mycobacteria.

Inactivation of Mycobacterium paratuberculosis in cows' milk at pasteurization temperatures

The thermal inactivation of 11 strains of Mycobacterium paratuberculosis at pasteurization temperatures was investigated. Cows' milk inoculated with M. paratuberculosis at two levels (10(7) and 10(4) CFU/ml) was pasteurized in the laboratory by (i) a standard holder method (63.5 degrees C for 30 min) and (ii) a high-temperature, short-time (HTST) method (71.7 degrees C for 15 s). Additional heating times of 5, 10, 15, 20, and 40 min at 63.5 degrees C were included to enable the construction of a thermal death curve for the organism. Viability after pasteurization was assessed by culture on Herrold's egg yolk medium containing mycobactin J (HEYM) and in BACTEC Middlebrook 12B radiometric medium supplemented with mycobactin J and sterile egg yolk emulsion. Confirmation of acid-fast survivors of pasteurization as viable M. paratuberculosis cells was achieved by subculture on HEYM to indicate viability coupled with PCR using M. paratuberculosis-specific 1S900 primers. When milk was initially inoculated with 10(6) to 10(7) CFU of M. paratuberculosis per ml, M. paratuberculosis cells were isolated from 27 of 28 (96%) and 29 of 34 (85%) pasteurized milk samples heat treated by the holder and HTST methods, respectively. Correspondingly, when 10(3) to 10(4) CFU of M. paratuberculosis per ml of milk were present before heat treatment, M. paratuberculosis cells were isolated from 14 of 28 (50%) and 19 of 33 (58%) pasteurized milk samples heat treated by the holder and HTST methods, respectively. The thermal death curve for M. paratuberculosis was concave in shape, exhibiting a rapid initial death rate followed by significant "tailing." Results indicate that when large numbers of M. paratuberculosis cells are present in milk, the organism may not be completely inactivated by heat treatments simulating holder and HTST pasteurization under laboratory conditions.

Peptide mapping of bovine T-cell epitopes for the 38 kDa tuberculosis antigen

Mycobacterium bovis infection in cattle continues to be a problem in several regions, partly due to inadequate diagnostic tests. The aim of this study was to use an experimental model of the natural disease to identify T-cell epitopes from the mycobacterial 38 kDa antigen as potentially specific diagnostic reagents. A panel of overlapping synthetic peptides (16-mers with a five-residue overlap) were produced from the published amino acid sequence. It was found that peripheral blood lymphocytes from at least three of four experimentally infected animals, which were considered to be in either Th1- or Th1/Th2-dominated stages of anti-mycobacterial immunity, proliferated in response to five epitopes (residues 1-27, 88-107, 122-138, 243-260 and 307-328). However, in vitro production of IFN-gamma was detected only in response to epitope 122-138, indicating a role in protective immunity. The peptides were not recognized by control, uninfected animals, but all epitopes showed various degrees of recognition by animals which were field reactors to intradermal tuberculin testing. Furthermore, epitopes 1-27, 88-107 and 122-138 were recognized by four breeds of cattle and by animals from separate herds, suggesting genetic permissiveness in recognition which would be essential in the development of a diagnostic test.

Genomic fingerprinting of Mycobacterium bovis from cattle by restriction fragment length polymorphism analysis

Two insertion sequences, IS6110 and IS1081, specific to the tuberculosis complex mycobacteria and a highly reiterated DNA element (pTBN12) cloned from Mycobacterium tuberculosis were systematically used to identify restriction fragment length polymorphism (RFLP) types among bovine isolates of Mycobacterium bovis in Northern Ireland. In a sample of 109 isolates, probes IS6110, IS1081, and pTBN12 identified 10, 2, and 12 distinct patterns, respectively. By combining the patterns generated by the three probes it was possible to identify 28 distinct RFLP types. The standard protocol advocated for RFLP analysis of M. tuberculosis was used and would facilitate computer-based gel documentation and image analysis to establish a database of M. bovis types for large-scale epidemiological studies. These procedures will facilitate interlaboratory comparisons of M. bovis isolates and will help to elucidate the precise epidemiology of bovine tuberculosis in different countries.

Immunoblot analysis of humoral immune responses to Mycobacterium bovis in experimentally infected cattle: early recognition of a 26-kilodalton antigen

Development of a serodiagnostic test for bovine tuberculosis necessitates an understanding of the humoral immune responses of animals following infection with Mycobacterium bovis. The antibody responses in groups of calves challenged intranasally with different doses of M. bovis (approximately 10(2), 10(4), and 10(6) CFU) or placed in contact with the infected animals were analyzed by immunoelectrophoretic blotting in which a whole-cell sonicate of M. bovis was utilized as an antigen. Antibody responses were evident early in infections in which calves were exposed to high doses of M. bovis, while in groups exposed to lower doses, the time until antibody was detected increased as the challenge dose decreased. In cattle exposed to M. bovis, immunoblot analysis showed antibody responses to three main antigens of 26, 22, and 16 kDa. It was further demonstrated that antibody responses to the 26-kDa antigen appeared earliest in the course of infection. Preliminary investigations in this study have identified a 26-kDa antigen for potential use in improved serodiagnosis by enzyme-linked immunosorbent assays.

Detection of Mycobacterium bovis infection in skin test-negative cattle with an assay for bovine interferon-gamma

Mycobacterium bovis was isolated from respiratory secretions and lymph nodes from 15 skin test-negative cattle which exhibited interferon-gamma responses. These field cases, identified by blood testing, constituted a significant proportion of skin test-negative cattle which had been subjected to extensive post mortem examinations. Typical tuberculous lesions were found in seven of them. The consequences of cattle with early tuberculosis infection not being detected by traditional tuberculin testing are considered.

Identification of bovine T-cell epitopes for three Mycobacterium bovis antigens: MPB70, 19,000 MW and MPB57

Bovine tuberculosis remains a serious problem in several regions, partly due to a lack of specific diagnostic tests. The aim of this study was to identify bovine T-cell epitopes for defined Mycobacterium bovis antigens using an experimental model of the natural disease. Panels of synthetic peptides (16-mers with five residue overlaps) were produced from published amino acid sequences for MPB70, the 19,000 MW antigen and MPB57. In vitro lymphocyte proliferation assays were used to identify T-cell epitopes. Lymphocytes from experimentally infected cattle proliferated in response to five epitopes (residues 88-105 and 144-163 for MPB70; 1-16 and 67-84 for the 19,000 MW antigen; and 85-100 for MBP57). These epitopes were not recognized by control, non-infected animals, but were recognized by field reactors to intradermal tuberculin testing. All five epitopes were recognized by three different breeds of cattle (Friesian, Charolais and Simmental). In addition, the bovine T-cell epitopes identified for the 19,000 MW antigen in this study were similar to epitopes previously reported for man and mouse. Thus, as well as identifying candidate reagents for improved diagnostic tests and vaccination, this study provides evidence for genetic promiscuity T-cell recognition of major myobacterial epitopes.

Pathogenesis of Mycobacterium bovis infection in cattle

This paper reviews the pathogenesis of Mycobacterium bovis infection in cattle, focusing on aspects relating to the host rather than the organism. A broad concept of pathogenesis has been considered and information is presented on sources and routes of infection, as well as the immune responses and pathology. In addition, data is presented on the excretion of M. bovis from tuberculous cattle.

Identification of mycobacteria from animals by restriction enzyme analysis and direct DNA cycle sequencing of polymerase chain reaction-amplified 16S rRNA gene sequences

Two methods, based on analysis of the polymerase chain reaction-amplified 16S rRNA gene by restriction enzyme analysis (REA) or direct cycle sequencing, were developed for rapid identification of mycobacteria isolated from animals and were compared to traditional phenotypic typing. BACTEC 7H12 cultures of the specimens were examined for "cording," and specific polymerase chain reaction amplification was performed to identify the presence of tubercle complex mycobacteria. Combined results of separate REAs with HhaI, MspI, MboI, and ThaI differentiated 12 of 15 mycobacterial species tested. HhaI, MspI, and ThaI restriction enzyme profiles differentiated Actinobacillus species from mycobacterial species. Mycobacterium bovis could not be differentiated from M. bovis BCG or Mycobacterium tuberculosis. Similarly, Mycobacterium avium and Mycobacterium paratuberculosis could not be distinguished from each other by REA but were differentiated by cycle sequencing. Compared with traditional typing, both methods allowed rapid and more accurate identification of acid-fast organisms recovered from 21 specimens of bovine and badger origin. Two groups of isolates were not typed definitively by either molecular method. One group of four isolates may constitute a new species phylogenetically very closely related to Mycobacterium simiae. The remaining unidentified isolates (three badger and one bovine) had identical restriction enzyme profiles and shared 100% nucleotide identify over the sequenced signature region. This nucleotide sequence most closely resembled the data base sequence of Mycobacterium senegalense.

Isolation of Mycobacterium bovis from the respiratory tracts of skin test-negative cattle

Mycobacterium bovis was isolated from the respiratory tracts of three cattle which registered negative to tuberculin testing; no tuberculous lesions were found and the culture of lymph nodes and other tissues proved negative. One animal was from a group of five calves which had been inoculated intranasally with M bovis, and the organism was recovered once only from nasal mucus sampled 100 days after inoculation. The second animal had had contact with experimentally infected cattle which were excreting M bovis and the third was from a commercial farm. The results of ELISAS for antimycobacterial antibodies and interferon-gamma, and of lymphocyte transformation assays are presented. The animals' immune responses provided evidence that each of them had been challenged.

ELISA tests for antibodies in experimental bovine tuberculosis

It was shown that 10(4) cfu of a field isolate of Mycobacterium bovis caused illness in five experimentally infected calves; one of these died. One of three contact calves also became clinically infected. Considerable variation in the humoral response of the affected animals was demonstrated by ELISAs using purified protein derivative (PPD) and phosphatide antigens. The inoculation of antigens used in the comparative tuberculin skin test significantly enhanced the level of PPD antibodies in the affected animals whereas that of the apparently non-infected contact animals remained unchanged.

Profiles of toxin production by thermophilic Campylobacter of animal origin

Seventy-five strains of Campylobacter jejuni and C. coli, which were isolated from a variety of animal species, primarily poultry, were examined for production of toxin. Polymyxin extracts were tested in in vitro assays using CHO-KI, FCL (foetal calf lung), Vero, HeLa and CEF (chicken embryo fibroblast) cells. The toxic effects observed were cell rounding and death. Extracts from almost all C. jejuni and C. coli strains were toxic to both CHO-KI and FCL cells and 69.0% of C. jejuni isolates and 75% of C. coli isolates were also toxic to CEF cells. 50.7% of C. jejuni extracts were toxic to Vero cells and 46.5% toxic to HeLa cells. None of the C. coli isolates were toxic to either of these cell lines. None of the strains tested produced cytotonic enterotoxin. No differences in toxigenicity patterns were evident between Campylobacter isolated from different sources.

Genetic analysis of the adenovirus E4 6/7 trans activator: interaction with E2F and induction of a stable DNA-protein complex are critical for activity

The adenovirus early E4 transcription unit encodes a 19-kDa polypeptide that trans activates transcription of the early E2 gene and is dependent on the binding sites for the E2F transcription factor. Biochemical assays have shown that the E4 protein, a product of the 6/7 open reading frame, interacts with the E2F transcription factor and alters its DNA binding characteristics, resulting in the formation of a very stable DNA-protein complex. We have generated a series of E4 mutants to determine the requirements for the interaction with E2F and the induction of a stable E2F complex on the E2 promoter in relation to the trans activation of E2 transcription. We find that the trans-activation function of E4 is dependent on the ability of the protein to interact with E2F and that full trans activation is dependent on the induction of the E2F stable complex. Interestingly, several mutants distinguish these events, since they retain the ability to interact with E2F but have lost the capacity to induce the stable complex. Since these mutants can still trans activate, albeit at reduced levels, these results suggest that the E4 protein contributes to trans activation that is independent of stable complex formation.

A mathematical model for Mycobacterium bovis excretion from tuberculous cattle

An analysis was carried out of available information from a series of experiments on the excretion of M. bovis from infected cattle. The analysis indicated that an inverse exponential relationship exists between 'dose' of organisms given and the delay before excretion commences. This relationship was represented mathematically. Available field data supported the relationship and indicated that in natural bovine tuberculosis excretion of M. bovis begins around 87 days after infection occurs. It is also suggested that the data supports the concept of single nuclei infections in cattle.