'Original mycobacterial sin'

Mycobacterium avium ssp. paratuberculosis and Crohn's Disease-Diagnostic Microbiological Investigations Can Inform New Therapeutic Approaches

Mycobacterium avium ssp. paratuberculosis (MAP) is the cause of Johne's disease (JD), which is a chronic infectious gastrointestinal disease of ruminants and is often fatal. In humans, MAP has been associated with Crohn's disease (CD) for over a century, without conclusive evidence of pathogenicity. Numerous researchers have contributed to the subject, but there is still a need for evidence of the causation of CD by MAP. An infectious aetiology in CD that is attributable to MAP can only be proven by bacteriological investigations. There is an urgency in resolving this question due to the rising global incidence rates of CD. Recent papers have indicated the "therapeutic ceiling" may be close in the development of new biologics. Clinical trial outcomes have demonstrated mild or inconsistent improvements in therapeutic interventions over the last decades when compared with placebo. The necessity to revisit therapeutic options for CD is becoming more urgent and a renewed focus on causation is essential for progress in identifying new treatment options. This manuscript discusses newer interventions, such as vaccination, FMT, dietary remediation and gut microbiome regulation, that will become more relevant as existing therapeutic options expire. Revisiting the MAP theory as a potential infectious cause of CD, rather than the prevailing concept of an "aberrant immune response" will require expanding the current therapeutic programme to include potential new alternatives, and combinations of existing treatments. To advance research on MAP in humans, it is essential for microbiologists and medical scientists to microscopically detect CWDM and to biologically amplify the growth by directed culture.

Tuberculosis vaccination needs to avoid 'decoy' immune reactions

Current search for a new effective vaccine against tuberculosis involves selected antigens, vectors and adjuvants. These are being evaluated usually by their booster inoculation following priming with Bacillus Calmette-Guerin. The purpose of this article is to point out, that despite being attenuated of virulence, priming with BCG may still involve immune mechanisms, which are not favourable for protection against active disease. It is postulated, that the responsible 'decoy' constituents selected during the evolution of pathogenic tubercle bacilli may be involved in the evasion from bactericidal host resistance and stimulate immune responses of a cytokine phenotype, which lead to the transition from latent closed granulomas to reactivation with infectious lung cavities. The decoy mechanisms appear as favourable for most infected subjects but leading in a minority of cases to pathology which can effectively transmit the infection. It is proposed that construction and development of new vaccine candidates could benefit from avoiding decoy-type immune mechanisms.

Isolation of non-tuberculosis mycobacteria in treated dental unit waterlines

OBJECTIVE

The purpose of the study was to investigate the presence of non-tuberculosis mycobacteria (NTM) in dental unit waterlines that were being routinely treated with an intermittent use waterline cleaner.

STUDY DESIGN

The study was conducted at a hospital dentistry clinic where immunocompromised patients are seen. Water samples from two lines on one of two dental units were taken before and after routine weekend chemical treatment. Sampling was repeated on two subsequent occasions, on the same unit, at three monthly intervals. Laboratory techniques included centrifugation and membrane filtration to detect small numbers of organisms.

RESULTS

Mycobacterium simiae was isolated from one of the four pre-treatment samples and from two of the four post-treatment samples. Mycobacterium mucogenicum was isolated from one of the four post-treatment samples.

CONCLUSIONS

This pilot study found that NTM were present in DUWLs that were being routinely treated with an intermittent use chemical cleaner. Practitioners are urged to understand the limitations of available DUWL treatments, and to consider the use of sterile water for non-surgical, as well as surgical, treatment of immunocompromised patients.

A longitudinal study of environmental mycobacteria on a farm in south-west England

Soil, stream beds and cattle drinking troughs were sampled every 3 months over 3 years. More than 750 putative mycobacteria were isolated and grouped into more than 50 biotypes pending full identification. Samples from woodland and farmed land yielded fewer isolates per site compared with other terrains (P < 0.05). Some seasonal effects were noted but the greatest difference was between years 1 and 3. This appeared not to be due to differences in temperature, rainfall or experimental procedure, but coincided with the introduction of organic farming practices. In year 3 there was a significant increase in nitrate-reducing slow growers, both pigmented (P < or = 0.006) and non-pigmented strains (P < or = 0.002), and a shift in biotypes was noted. In contrast, all fast growers declined with time, as did those slow growers unable to reduce nitrate. Changing farming practice may alter the profile of environmental mycobacteria, which has important implications for the immunological priming of humans and animals.

Specific antibody responses to Mycobacterium bovis in infected cattle analysed with six mycobacterial antigens in enzyme-linked immunosorbent assays

A total of 23 (15.3 per cent) of 150 cattle infected with Mycobacterium bovis and which had never been tuberculin tested showed specific antibody responses to M bovis. Their sera may be important keys to the identification of unique M bovis antigens for use in specific serodiagnostic tests. Assessment of specific and non-specific responses was done by screening sera in six indirect anti-IgG enzyme-linked immunosorbent assays using whole cell sonicates of M bovis and five members of the Mycobacterium avium-intracellulare-scrofulaceum complex as respective antigens. Sera from 16 infected cattle that had been tuberculin tested positive and nine uninfected cattle (never tuberculin tested) were also assayed for specific and non-specific responses. Three other findings emerged. First, 43 of the 150 infected animals (28.7 per cent) showed no antibody responses to any of the mycobacterial antigens used. Secondly, the cattle showing the highest antibody levels were associated with the greatest cross reactivity. Lastly, the results indicated that tuberculin injections may increase antibody responses to shared, rather than specific, M bovis antigens in infected cattle.

Evidence for a highly conserved, immunoreactive lipid in Mycobacterium tuberculosis

A survey of the fractionated lipids of Mycobacterium tuberculosis H37Rv was conducted using rabbit antiserum raised to homologous and heterologous mycobacteria. One minor, highly apolar lipid was resolved by Florisil column chromatography, which reacted preferentially to anti-M. tuberculosis H37Rv rabbit antibodies. Other chromatographic properties, i.e., thin-layer chromatographic mobility and staining properties, suggested an analog of the phenolic glycolipid of Mycobacterium leprae. Preliminary results in the application of the glycolipid to tuberculous populations in northeast Thailand suggest a usefulness in screening for tuberculosis.

Profiles of skin test reactivity to antigens of various mycobacterial species in a human population and in experimental infections

Sensitivity profiles to 6 mycobacterial skin test antigens prepared from Mycobacterium tuberculosis, M. kansasii, M. scrofulaceum, M. intracellulare, M. avium and M. fortuitum were obtained in 6 groups of guinea pigs, each infected with one of the 6 mycobacterial species. Each group of animals showed the greatest sensitivity towards the homologous antigen. A second infection with a different species was super-imposed two months after the skin tests; the sensitivity towards the second species usually became dominant. Sensitivity profiles with the 6 antigens in a large random sample of the population of a district of Haiti resembled closely the sensitivity profiles for all the guinea pigs infected with two mycobacterial species. This suggested that the Haitian population consisted of a mixture of persons infected with one or more mycobacteria. Haitians with the largest to an antigen, which was at least 6 mm in diameter and at least 2 mm larger than the reaction to any other antigen, were assumed to be infected with the corresponding mycobacterial species. Sensitivity profiles of these persons resembled closely the sensitivity profiles of guinea pigs infected with the same species. In the Haitian population prevalence of infection with other mycobacterial species was much more common than infection with M tuberculosis. In spite of this, after 15 years of age only the tuberculosis infection rates increased with age, suggesting that allergy produced by M. tuberculosis infection was stronger and subject to much less waning than allergy produced by other mycobacterial infections.

Recent European research activities in mycobacteriology

The subject of mycobacteriology is becoming an increasingly popular and complex one and the contribution by European scientists has been considerable. The important areas of research include taxonomy and the improvement of identification methods; biochemistry, including enzymology, metabolic regulation, lipid chemistry, iron uptake and metabolism, pigment synthesis and DNA chemistry; genetics and bacteriophages; ecology, including the effect of contact with environmental mycobacteria on the mammalian immune response; immunology; and the association of disease and cell-wall-free mycobacteria and studies on the leprosy bacillus. The European Society of Mycobacteriologists has recently been founded to unite workers in these disciplines and to promote and disseminate knowledge in this subject.

The specificity of the humoral immune response to soluble mycobacterial antigens in tuberculosis

A high proportion of patient with tuberculosis have been shown to produce significant levels of antibodies to antigens unique to Mycobacterium tuberculosis, antigens restricted to the slowly growing mycobacteria and antigens common to all species in the genus. About 20% of patients with this disease do not have significantly elevated levels of antibodies to any of these groups of antigens. Consequently, the availability of highly purified soluble antigens specific for M. tuberculosis would not permit more cases of tuberculosis to be diagnosed serologically.

Tuberculin hypersensitivity following BCG vaccination in Brisbane school children

Seven hundred and fifty Brisbane school children were tuberculin tested, in paired groups, with purified protein derivatives of Mycobacterium tuberculosis, bovis, BCG and avium. Reaction to avian PPD were stronger than to any of the others used. This finding may be of some importance in interpreting the variation in protection afforded by BCG vaccination.