Dominique Terru

First Molecular Epidemiology Study of Mycobacterium tuberculosis in Burkina Faso

ABSTRACT We conducted a molecular epidemiology study on 120 Mycobacterium tuberculosis isolates from patients presenting pulmonary tuberculosis (TB) in Burkina Faso. Classical antibiogram studies and genetic characterization, using mycobacterial interspersed repetitive-unit-variable-number tandem-repeat (MIRU-VNTR) typing and spoligotyping, were applied after culture. Molecular analysis of specific signatures showed that all TB cases reported in this study were caused by M. tuberculosis and identified no Mycobacterium bovis or Mycobacterium africanum isolates. This result is unexpected, as M. africanum strains were reportedly the etiologic agent in 20% of TB cases 2 decades ago. The comparison of spoligotypes from Burkina Faso with an international spoligotype database (SpolDB4) showed that the majority of isolates belong to major clades of M. tuberculosis (Haarlem, 9%; Latin American-Mediterranean, 30%; and T, 20%). The predominant group of isolates (30%) corresponds to spoligotype 61, described in Cameroon as the “Cameroon family.” In Burkina Faso, as in Cameroon, this family could be associated with recent transmission of TB, suggesting a recent expansion in West Africa. Our data suggest a low level of primary drug resistance that may be a positive result of the Directly Observed Therapy Shortcourse program. Besides, based on spoligotyping plus MIRU-VNTR, data showed a high number of clusters in our sample, suggesting a high level of recent TB transmission in Burkina Faso. Nevertheless, an important genetic polymorphism was observed in this country, reflecting an endemicity situation where the control of TB would have less impact in the main towns.

Genetic diversity and population structure of Mycobacterium marinum: New insights into host and environmental specificities

ABSTRACT Mycobacterium marinum causes a systemic tuberculosis-like disease in fish and skin infections in humans that can spread to deeper structures, resulting in tenosynovitis, arthritis, and osteomyelitis. However, little information is available concerning (i) the intraspecific genetic diversity of M. marinum isolated from humans and animals; (ii) M. marinum genotype circulation in the different ecosystems, and (iii) the link between M. marinum genetic diversity and hosts (humans and fish). Here, we conducted a genetic study on 89 M. marinum isolates from humans (n = 68) and fish (n = 21) by using mycobacterial interspersed repetitive units-variable number of tandem repeats (MIRU-VNTR) typing. The results show that the M. marinum population is genetically structured not only according to the host but also according to the ecosystem as well as to tissue tropism in humans. This suggests the existence of different genetic pools in the function of the biological and ecological compartments. Moreover, the presence of only certain M. marinum genotypes in humans suggests a different zoonotic potential of the M. marinum genotypes. Considering that the infection is linked to aquarium activity, a significant genetic difference was also detected when the human tissue tropism of M. marinum was taken into consideration, with a higher genetic polymorphism in strains isolated from patients with cutaneous forms than from individuals with deeper-structure infection. It appears that only few genotypes can produce deeper infections in humans, suggesting that the immune system might play a filtering role.

Pyoderma vegetans in a renal transplant recipient: first case of human infection with Nocardia vinacea.

Bacteria of the Nocardia species are commonly found in the natural environment. Some of these bacilli are potential pathogens, especially among immunocompromised patients. We have recently observed a cutaneous infection by Nocardia vinacea, which represents, to the best of our knowledge, the first documented case of N. vinacea infection in humans. A 60-year-old woman was examined 4 weeks after the appearance of a painful skin lesion on the right forearm that had initially grown within a few days. She had received a renal transplant 1 year before for an autosomal dominant polycystic kidney disease diagnosed 25 years earlier. Living in the south of France, she had not traveled the past 10 years. The graft function was satisfactory (serum creatinine 125 mol/L, estimated creatinine clearance 75 mL/ min/1.73 m). Her usual treatment included prednisolone (10 mg/day) and tacrolimus (4 mg/day). The lesion was well delineated, measuring 5 4 cm, with an exudative vegetant appearance and secretion of pus when submitted to pressure (Fig. 1). The patient presented no fever, no change of general state, and no sign of infection elsewhere. Blood analysis and chest x-rays revealed no abnormalities. An initial skin biopsy excluded a neoplasic proliferation. It showed an epidermal hyperplasia infiltrated by neutrophils suggesting an infection. A first analysis of pus samples failed to reveal any bacterium. A second cutaneous biopsy and pus samples were collected for further bacteriologic, mycologic, and mycobacteriologic analyses. Among the various culture conditions, bacterial growth was detected in the liquid medium specific for mycobacteria after 72 hr of incubation at 30°C. Gram staining revealed gram-positive bacilli affiliated with the genus Nocardia by using phenotypic techniques. 16S rRNA gene sequencing identified N. vinacea (100% sequence identity to N. vinacea IFM0344, GenBank accession number AB162802). The antibiogram indicated a sensitivity to trimethoprim-sulfametoxazol, which was then administrated orally to the patient in association with argentic sulfadiazine ointment. This treatment eliminated the lesion in less than 1 month. In this case, the primary cutaneous nocardiosis was identified in an immunocompromised patient. Usually, this type of infection is found in immunocompetent people after a skin rupture and is mainly due to N. Brasiliensis (1). Cutaneous nocardia infection can also result from an internal diffusion of the bacteria after inhalation of the germ. In this case, however, no internal infection was found. As the patient reported regular gardening activities, we suspect that the infection may have occurred from a minor unnoticed wound inflicted while gardening. This hypothesis is reinforced by the fact that N. vinacea was first isolated from soil (2). In addition, N. vinacea was cultured after analysis of numerous samples using various conditions. Indeed, its optimal growth temperature is 30°C, a temperature close to that of the skin surface, and N. vinacea could remain undetected by conventional methods with incubation at 37°C (2). This bacteria may be part of newly emerging germs susceptible to infect humans. To minimize the risk of a severe general dissemination, the

High IFN-γ Release and Impaired Capacity of Multi-Cytokine Secretion in IGRA Supernatants Are Associated with Active Tuberculosis.

Interferon gamma (IFN-γ) release assays (IGRAs) detect Mycobacterium tuberculosis (Mtb) infection regardless of the active (ATB) or latent (LTBI) forms of tuberculosis (TB). In this study, Mtb-specific T cell response against region of deletion 1 (RD1) antigens were explored by a microbead multiplex assay performed in T-SPOT TB assay (T-SPOT) supernatants from 35 patients with ATB and 115 patients with LTBI. T-SPOT is positive when over 7 IFN-γ secreting cells (SC)/250 000 peripheral blood mononuclear cells (PBMC) are enumerated. However, over 100 IFN-γ SC /250 000 PBMC were more frequently observed in the ATB group compared to the LTBI group. By contrast, lower cytokine concentrations and lower cytokine productions relative to IFN-γ secretion were observed for IL 4, IL-12, TNF-α, GM-CSF, Eotaxin and IFN-α when compared to LTBI. Thus, high IFN-γ release and low cytokine secretions in relation with IFN-γ production appeared as signatures of ATB, corroborating that multicytokine Mtb-specific response against RD1 antigens reflects host capacity to contain TB reactivation. In this way, testing cytokine profile in IGRA supernatants would be helpful to improve ATB screening strategy including immunologic tests.

B cells response directed against Cut4 and CFP21 lipolytic enzymes in active and latent tuberculosis infections

Background Better understanding of the immune response directed against Mycobacterium tuberculosis (Mtb) is critical for development of vaccine strategies and diagnosis tests. Previous studies suggested that Mtb enzymes involved in lipid metabolism, are associated with persistence and/or reactivation of dormant bacilli. Methods Circulating antibodies secreting cells (ASCs), memory B cells, and antibodies directed against Cut4 (Rv3452) and CFP21 (Rv1984c) antigens were explored in subjects with either active- or latent-tuberculosis (LTB), and in Mtb-uninfected individuals. Results Circulating anti-Cut4 ASCs were detected in 11/14 (78.6%) subjects from the active TB group vs. 4/17 (23.5%) from the LTB group (p = 0.001). Anti-CFP21 ASCs were found in 11/14 (78.6%) active TB vs. in 5/17 (29.4%) LTB cases (p = 0.01). Circulating anti-Cut4 and anti-CFP21 ASCs were not detected in 38 Mtb uninfected controls. Memory B cells directed against either Cut4 or CFP21 were identified in 8/11 (72.7%) and in 9/11 (81.8%) subjects with LTB infection, respectively, and in 2/6 Mtb uninfected individuals (33.3%). High level of anti-Cut4 and anti-CFP21 IgG were observed in active TB cases. Conclusion Circulating IgG SCs directed against Cut4 or CFP21 were mostly detected in patients presenting an active form of the disease, suggesting that TB reactivation triggers an immune response against these two antigens.