Genotyping did not evidence any contribution of Mycobacterium bovis to human tuberculosis in Brazil

Abstract

The contribution of Mycobacterium bovis to the global burden of tuberculosis (TB) in man is likely to be underestimated due to its dysgonic growth characteristics and because of the absence of pyruvate in most used media is disadvantageous for its primary isolation. In Brazil Mycobacterium culture, identification and susceptibility tests are performed only in TB reference centers, usually for selected cases. Moreover, solid, egg-based, glycerol-containing (without pyruvate supplementation) Löwenstein-Jensen (L-J) or Ogawa media are routinely used, unfavouring M. bovis isolation. To determine the importance of M. bovis as a public health threat in Brazil we investigated 3046 suspected TB patients inoculating their clinical samples onto routine L-J and L-J pyruvate enriched media. A total of 1796 specimens were culture positive for Mycobacterium spp. and 702 TB cases were confirmed. Surprisingly we did not detect one single case of M. bovis in the resulting collection of 1674 isolates recovered from M. bovis favourable medium analyzed by conventional and molecular speciation methods. Also, bacillary DNA present on 454 sputum smears from 223 TB patients were OxyR genotyped and none was recognized as M. bovis. Our data indicate that M. bovis importance on the burden of human TB in Brazil is marginal.

Genotyping and rifampicin and isoniazid resistance in Mycobacterium bovis strains isolated from the lymph nodes of slaughtered cattle

“…Studies in Mexico have reported a greater prevalence, with annual rates of up to 40% [4]. In Brazil, published studies on this issue are rare, and some of them did not find M. bovis strains in samples of human tuberculosis [5,6]. In contrast, a study in the state of Minas Gerais showed that M. bovis accounted for 1.6% of the mycobacterial isolates obtained from patients with tuberculosis [7].…”

Isolation and identification of Mycobacterium bovis in milk from cows in northeastern Brazil

“…However, infection in humans is generally not confirmed by isolation and identification of the agent, making it impossible to identify the possible source of infection. In addition, the human diseases caused by M. tuberculosis and M. bovis are indistinguishable using clinical, radiological and pathological methods (ROCHA et al, 2011). Transmission of M. bovis to humans occurs through consumption of raw milk and dairy products, or through contact with secretions from fistulated abscesses.…”

Tuberculosis caused by RD<SUP>Rio</SUP> <I>Mycobacterium tuberculosis</I> is not associated with differential clinical features

“…3–6 In previous studies, we described that the clonally derived RD Rio strains of M. tuberculosis are defined by a ~26.3 kb deletion resulting in the loss or modification of 10 genes, including two preproenkephalin genes known to be recognized by host immunity. 7 In prior publications from our group, insertion sequence (IS) 6110 restriction fragment length polymorphism and MIRU-VNTR typing showed that the RD Rio sublineage likely occurred at a more distant evolutionary time, as both methods indicated considerable divergence, while it remains in the Euro-American M. tuberculosis lineage as well as belonging to the single nucleotide polymorphism Cluster VI grouping.…”