Genetic diversity and drug resistance pattern of Mycobacterium tuberculosis strains isolated from pulmonary tuberculosis patients in the Benishangul Gumuz region and its surroundings, Northwest Ethiopia.

INTRODUCTION: Tuberculosis (TB) remains a major global public health problem and is the leading cause of death from a single bacterium, Mycobacterium tuberculosis (MTB) complex. The emergence and spread of drug-resistant strains aggravate the problem, especially in tuberculosis high burden countries such as Ethiopia. The supposedly high initial cost of laboratory diagnosis coupled with scarce financial resources has limited collection of information about drug resistance patterns and circulating strains in peripheral and emerging regions of Ethiopia. Here, we investigated drug susceptibility and genetic diversity of mycobacterial isolates among pulmonary tuberculosis patients in the Benishangul Gumuz region and its surroundings in northwest Ethiopia. METHODS AND MATERIAL: In a cross-sectional study, 107 consecutive sputum smear-positive pulmonary tuberculosis (PTB) patients diagnosed at two hospitals and seven health centers were enrolled between October 2013 and June 2014. Sputum samples were cultured at Armauer Hansen Research Institute (AHRI) TB laboratory, and drug susceptibility testing (DST) was performed against Isoniazid, Rifampicin, Ethambutol, and Streptomycin using the indirect proportion method. Isolates were characterized using polymerase chain reaction (PCR)based Region of Difference 9 (RD9) testing and spoligotyping. Statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) for Windows version 24.0. RESULTS: Of 107 acid-fast-bacilli (AFB) smear-positive sputum samples collected, 81.3% (87/107) were culture positive. A PCR based RD9 testing revealed that all the 87 isolates were M. tuberculosis. Of these isolates, 16.1% (14/87) resistance to one or more drugs was observed. Isoniazid monoresistance occurred in 6.9% (6/87). Multidrug resistance (MDR) was observed in two isolates (2.3%), one of which was resistant to all the four drugs tested. Spoligotyping revealed that the majority, 61.3% (46/75) of strains could be grouped into ten spoligotype patterns containing two to 11 isolates each while the remaining 38.7% (29/75) were unique. SIT289 (11 isolates) and SIT53 (nine isolates) constituted 43.5% (20/46) among clustered isolates while 29.3% (22/75) were ''New" to the database. The dominant families were T, 37% (28/75), CAS, 16.0% (12/75), and H, 8% (6/75), adding up to 51.3% (46/75) of all isolates identified. CONCLUSION AND RECOMMENDATIONS: The current study indicates a moderate prevalence of MDR TB. However, the observed high monoresistance to Isoniazid, one of the two proxy drugs for MDR-TB, reveals the hidden potential threat fora sudden increase in MDR-TB if resistance to Rifampicin would increase. Clustered spoligotype patterns suggest ongoing active tuberculosis transmission in the area. The results underscore the need for enhanced monitoring of TB drug resistance and epidemiological studies in this and other peripheral regions of the country using robust molecular tools with high discriminatory power such as the Mycobacterial Interspersed Repetitive Units -Variable Number of Tandem Repeats (MIRU-VNTR) typing and whole-genome sequencing (WGS).

Performance of diagnostic tests for pulmonary tuberculosis in indigenous populations in Brazil: the contribution of Rapid Molecular Testing.

OBJECTIVE: To evaluate the accuracy of rapid molecular testing as a diagnostic tool and estimate the incidence of smear-positive pulmonary tuberculosis among the indigenous population. METHODS: This is an epidemiological study based on secondary data. We calculated the incidence of smear-positive pulmonary tuberculosis between January 1st, 2011 and December 31, 2016, and the performance of bacilloscopy and rapid molecular testing in diagnosing pulmonary tuberculosis compared to sputum culture (standard test). RESULTS: We included 4,048 cases of indigenous people with respiratory symptoms who provided sputum samples for analysis. Among them, 3.7%, 6.7%, and 3.7% had positive results for bacilloscopy, sputum culture, and rapid molecular testing, respectively. The mean incidence of pulmonary tuberculosis was 269.3/100 thousand inhabitants. Rapid molecular testing had 93.1% sensitivity and 98.2% specificity, compared to sputum culture. Bacilloscopy showed 55.1% sensitivity and 99.6% specificity. CONCLUSIONS: Rapid molecular testing can be useful in remote areas with limited resources and a high incidence of tuberculosis, such as indigenous villages in rural regions of Brazil. In addition, the main advantages of rapid molecular testing are its easy handling, fast results, and the possibility of detecting rifampicin resistance. Together, these attributes enable the early start of treatment, contributing to reduce the transmission in communities recognized as vulnerable to infection and disease.

Performance of diagnostic tests for pulmonary tuberculosis in indigenous populations in Brazil: the contribution of Rapid Molecular Testing / Desempenho de testes para o diagnóstico de tuberculose pulmonar em populações indígenas no Brasil: a contribuição do Teste Rápido Molecular

ABSTRACT Objective: To evaluate the accuracy of rapid molecular testing as a diagnostic tool and estimate the incidence of smear-positive pulmonary tuberculosis among the indigenous population. Methods: This is an epidemiological study based on secondary data. We calculated the incidence of smear-positive pulmonary tuberculosis between January 1st, 2011 and December 31, 2016, and the performance of bacilloscopy and rapid molecular testing in diagnosing pulmonary tuberculosis compared to sputum culture (standard test). Results: We included 4,048 cases of indigenous people with respiratory symptoms who provided sputum samples for analysis. Among them, 3.7%, 6.7%, and 3.7% had positive results for bacilloscopy, sputum culture, and rapid molecular testing, respectively. The mean incidence of pulmonary tuberculosis was 269.3/100 thousand inhabitants. Rapid molecular testing had 93.1% sensitivity and 98.2% specificity, compared to sputum culture. Bacilloscopy showed 55.1% sensitivity and 99.6% specificity. Conclusions: Rapid molecular testing can be useful in remote areas with limited resources and a high incidence of tuberculosis, such as indigenous villages in rural regions of Brazil. In addition, the main advantages of rapid molecular testing are its easy handling, fast results, and the possibility of detecting rifampicin resistance. Together, these attributes enable the early start of treatment, contributing to reduce the transmission in communities recognized as vulnerable to infection and disease.

RESUMO Objetivo: Avaliar a acurácia do teste rápido molecular como ferramenta diagnóstica e estimar a incidência de casos pulmonares positivos entre a população indígena. Métodos: Estudo epidemiológico baseado em dados secundários. Foi calculada a incidência de casos de tuberculose pulmonar positiva entre 1° de janeiro de 2011 e 31 de dezembro de 2016, e o desempenho da baciloscopia e do teste rápido molecular no diagnóstico de tuberculose pulmonar, em comparação à cultura de escarro (teste padrão). Resultados: Foram incluídos 4.048 casos de indígenas considerados sintomáticos respiratórios, que forneceram amostras de escarro para análise. Destes, 3,7%, 6,7% e 3,7% apresentaram resultados positivos para baciloscopia, cultura e teste rápido molecular, respectivamente. A incidência média de tuberculose pulmonar foi de 269,3/100 mil habitantes. A sensibilidade do teste rápido molecular, em relação à cultura, foi 93,1% e a especificidade foi 98,2%. A baciloscopia apresentou sensibilidade 55,1% e especificidade 99,6%. Conclusões: O teste rápido molecular pode ser útil em áreas remotas, com recursos limitados e incidência de tuberculose elevada, como as aldeias indígenas nas áreas rurais do país. Ademais, o teste rápido molecular apresenta como principais vantagens o fácil manuseio, os resultados rápidos e a possibilidade de identificar a resistência à rifampicina. Em conjunto, esses atributos facilitam o início do tratamento precoce, contribuindo para reduzir a transmissão em comunidades reconhecidamente vulneráveis à infecção e à doença.

Extended spectrum of antibiotic susceptibility for tuberculosis, Djibouti.

In the Horn of Africa, there is a high prevalence of tuberculosis that is reported to be partly driven by multidrug-resistant (MDR) Mycobacterium tuberculosis strictu sensu strains. We conducted a prospective study to investigate M. tuberculosis complex species causing tuberculosis in Djibouti, and their in vitro susceptibility to standard anti-tuberculous antibiotics in addition to clofazimine, minocycline, chloramphenicol and sulfadiazine. Among the 118 mycobacteria isolates from 118 successive patients with suspected pulmonary tuberculosis, 111 strains of M. tuberculosis, five Mycobacterium canettii, one 'Mycobacterium simulans' and one Mycobacterium kansasii were identified. Drug-susceptibility tests performed on the first 78 isolates yielded nine MDR M. tuberculosis isolates. All isolates were fully susceptible to clofazimine, minocycline and chloramphenicol, and 75 of 78 isolates were susceptible to sulfadiazine. In the Horn of Africa, patients with confirmed pulmonary tuberculosis caused by an in vitro susceptible strain may benefit from anti-leprosy drugs, sulfamides and phenicol antibiotics.

Determination of Lipoprotein Z-Specific IgA in Tuberculosis and Latent Tuberculosis Infection.

Tuberculosis (TB) remains one of the most severe infectious diseases. It is still of paramount importance to establish more accurate, rapid, and efficient diagnostic methods. Since infection with Mycobacterium tuberculosis (M. tb) is largely mediated through the respiratory tract, IgA responses against mycobacterial proteins are worthy of investigation for their potential clinical utility. In this study, the IgA response targeting lipoprotein Z (LppZ) was determined by using a homemade ELISA with plasma of TB patients (N = 125), LTBI individuals (N = 92), healthy controls (HCs) (N = 165), as well as TB patients undergoing anti-TB treatment (N = 9). In parallel the antigen-specific IFN-γ release from PBMCs triggered by LppZ and M. tb-specific ESAT-6 or CFP-10 was detected by using an ELISPOT assay. It was found that the LppZ-specific IgA level was dramatically higher in TB patients than in HCs (p < 0.0001). Compared to that before anti-TB treatment, the LppZ-specific IgA level decreased substantially after 2 months of anti-TB treatment (p = 0.0297) and remained at low levels until the end of the treatment. What is more, pulmonary TB patients exhibited significantly higher LppZ-specific IgA-values than extra-pulmonary TB patients (p = 0.0296). Interestingly, the LppZ-specific IgA-values were negatively correlated to the amounts of IFN-γ released in response to LppZ with statistical significance (r = -0.5806, p = 0.0002). LppZ-specific IgA level was also higher in LTBI individuals than in HCs (p < 0.0001). Additionally there were some PPD+ HC individuals with high LppZ-specific IgA levels but the potential of this assay for identifying leaky LTBI in PPD+ HCs needs to be further investigated through follow-up studies. The sensitivity of detecting TB solely with ESAT-6 or CFP-10-specific IFN-γ release was increased by including the LppZ-specific IgA results, respectively, from 86.11 to 100% and 88.89 to 100%; the sensitivity of screening for LTBI was increased from 80.36 to 83.93% and 57.14 to 69.64%, respectively. The higher LppZ-specific IgA responses in TB and LTBI populations than in controls indicated high immunoreactivity to LppZ upon M. tb infection. Although the assay was not efficient enough for independent application in sero-diagnosis, LppZ-specific IgA might become a complementary biomarker for the improvement of TB and LTBI screening.

S100A12: Friend or foe in pulmonary tuberculosis?

In humans, S100A12 (also named Calgranulin C and EN-RAGE) is mainly expressed and secreted by neutrophil granulocytes. Extracellular S100A12 is involved in innate immune responses against microorganisms and parasites. S100A12 is a ligand for the receptor for advanced glycation end products (RAGE), which is a cell surface receptor on macrophages, endothelium, and lymphocytes. In a recent study, Realegeno et al. showed that S100A12 exerts antimicrobial activity against Mycobacterium leprae in infected human macrophages. Recently, some interesting data on the antimicrobial activity of S100A12 have been reported. Proinflammatory role of S100A12 is supported by another newly found receptor, Toll-like receptor 4 (TLR4). These observations emphasize the importance of S100A12 for the development of potential therapeutic approaches to increase protective immunity or reduce immunopathogenesis.

Clofazimine has delayed antimicrobial activity against Mycobacterium tuberculosis both in vitro and in vivo.

OBJECTIVES: The anti-leprosy drug clofazimine has been shown to have antimicrobial activity against Mycobacterium tuberculosis and has been associated with treatment-shortening activity in both clinical and preclinical studies of TB chemotherapy. However, a reported lack of early bactericidal activity (EBA) in TB patients has raised questions regarding the usefulness of clofazimine as an anti-TB drug. Our objective was to systematically evaluate the EBA of clofazimine in vitro and in vivo to provide insight into how and when this drug exerts its antimicrobial activity against M. tuberculosis. METHODS: We evaluated the 14 day EBA of clofazimine (i) in vitro at concentrations ranging from 4 times below to 4 times above the MIC for M. tuberculosis and (ii) in vivo in infected BALB/c mice at doses ranging from 1.5 to 100 mg/kg/day, and serum clofazimine levels were measured. In both experiments, isoniazid was used as the positive control. RESULTS: In vitro, clofazimine, at any concentration tested, did not exhibit bactericidal activity during the first week of exposure; however, in the second week, it exhibited concentration-dependent antimicrobial activity. In vivo, clofazimine, at any dose administered, did not exhibit bactericidal activity during the first week, and limited antimicrobial activity was observed during the second week of administration. While serum clofazimine levels were clearly dose dependent, the antimicrobial activity was not significantly related to the dose administered. CONCLUSIONS: Our data suggest that clofazimine's delayed antimicrobial activity may be due more to its mechanism of action rather than to host-related factors.

Diagnosis of tuberculosis based on the detection of a cocktail of mycobacterial antigen 85B, ESAT-6 and cord factor by immuno-PCR.

Attempts were made to enhance the sensitivity of immuno-PCR assay based on the detection of cocktail of mycobacterial antigen 85B (Rv1886c), ESAT-6 (Rv3875) and cord factor (trehalose 6,6'-dimycolate) in pulmonary and extrapulmonary TB patients. Detection of Ag85B was found to be superior to the detection of cocktail in TB patients.

Inoculation site leprosy in a tattoo as a paradoxical reaction following tuberculosis treatment.

We present a patient who developed inoculation site leprosy in a tattoo, which was confirmed by Mycobacterium leprae DNA sequencing of a polymerase chain reaction product from a skin biopsy. His leprosy became manifest as a paradoxical reaction only after 8 weeks of treatment for pulmonary tuberculosis.

Trend of childhood TB case notification in Lagos, Nigeria, 2011-2014.

BACKGROUND: Childhood tuberculosis (TB) has been neglected by national TB programs in sub-Saharan Africa because of the emphasis on adult smear-positive TB cases. About 80,000 HIV children die from TB, and over 550,000 childhood TB cases occur annually, representing 6% of the global TB burden, making TB an important cause of morbidity and mortality in children. Thus, this study assessed the trend of childhood TB cases notified in Lagos, Nigeria from 2011 to 2014. METHODS: Retrospective data review of childhood TB cases notified to the Lagos State TB and Leprosy Control Programme (LSTBLCP) between January 1, 2011 and December 31, 2014. RESULTS: A total of 2396 children were treated for all forms of TB representing 6.8% of the total 35,305 TB cases notified during the study period. This constituted 1102 (46%) males and 1294 (54%) females. There was a progressive increase in the proportion of children treated for TB from 495 (5.9%) in 2011, 539 (6.4%) in 2012, 682 (7.2%) in 2013 and 680 (7.6%) in 2014. Of the total childhood TB cases notified, 16.3-20% were new sputum pulmonary smear positive; 68.2-74.6% were new sputum pulmonary smear negative; while extra-pulmonary TB accounted for 6.7-10.6%. The case notification rate (CNR) of childhood TB per 100,000 increased from 13.4 in 2011, 14.3 in 2012, 17.7 in 2013 and 17.2 in 2014. CONCLUSION: There was an increase in the case notification rate of TB among children between 2011 and 2014. Efforts should be made to sustain this increasing trend.

Relative value of immunohistochemistry in detection of mycobacterial antigen in suspected cases of tuberculosis in tissue sections.

BACKGROUND: The diagnosis of tuberculosis (TB) depends on identification of the infecting organism. The diagnosis presents as a challenge due to its diverse clinical presentation and low yield of acid-fast bacilli (AFB) in tissue sections. AIM: The aim of the present study is immunohistochemical localization of tubercle bacilli or their components that persist in the granulomas, but have lost the property of staining with acid-fast stain, assess the advantage of immunostaining over conventional Ziehl-Neelsen (ZN) staining and further to study the staining pattern on immunohistochemistry (IHC). MATERIALS AND METHODS: The study population comprised 100 suspected cases of TB. Tissue sections from these were subjected to hematoxylin and eosin, ZN and IHC staining using polyclonal antibody to Mycobacterium tuberculosis followed by a comparative analysis of the results. Cases of lepromatous leprosy were used as a positive control. RESULTS: Acid-fast bacilli were identified by ZN stain in 23% of cases. IHC identified 72% cases. In the present study, IHC had higher sensitivity (95.56%) and negative predictive value (96.43%), but lower specificity (35.06%) and positive predictive value (30.56%) than ZN stain which had the sensitivity, specificity, positive predictive value and negative predictive values of 30.56%, 96.43%, 95.65% and 41.56% respectively. CONCLUSION: Immunohistochemistry is a simple and sensitive technique for localization of tubercle bacilli and their components on tissue sections. It can be easily incorporated in routine histopathology laboratory and serve as an efficient diagnostic adjunct to conventional ZN staining. This will help reduce the practice of prescribing empirical antitubercular treatment based on clinical suspicion alone.

Characterization of a cross-reactive, immunodominant and HLA-promiscuous epitope of Mycobacterium tuberculosis-specific major antigenic protein PPE68.

PPE68 (Rv3873), a major antignic protein encoded by Mycobacteriun tuberculosis-specific genomic region of difference (RD)1, is a strong stimulator of peripheral blood mononuclear cells (PBMCs) obtained from tuberculosis patients and Mycobacterium bovis bacillus Calmette Guerin (BCG)-vaccianted healthy subjects in T helper (Th)1 cell assays, i.e. antigen-induced proliferation and interferon-gamma (IFN-γ) secretion. To confirm the antigen-specific recognition of PPE68 by T cells in IFN-γ assays, antigen-induced human T-cell lines were established from PBMCs of M. Bovis BCG-vaccinated and HLA-heterogeneous healthy subjects and tested with peptide pools of RD1 proteins. The results showed that PPE68 was recognized by antigen-specific T-cell lines from HLA-heteregeneous subjects. To further identify the immunodominant and HLA-promiscuous Th1-1 cell epitopes present in PPE68, 24 synthetic peptides covering the sequence of PPE68 were indivdually analyzed for HLA-DR binding prediction analysis and tested with PBMCs from M. bovis BCG-vaccinated and HLA-heterogeuous healthy subjects in IFN-γ assays. The results identified the peptide P9, i.e. aa 121-VLTATNFFGINTIPIALTEMDYFIR-145, as an immunodominant and HLA-DR promiscuous peptide of PPE68. Furthermore, by using deletion peptides, the immunodominant and HLA-DR promiscuous core sequence was mapped to aa 127-FFGINTIPIA-136. Interestingly, the core sequence is present in several PPE proteins of M. tuberculosis, and conserved in all sequenced strains/species of M. tuberculosis and M. tuberculosis complex, and several other pathogenic mycobacterial species, including M. leprae and M. avium-intracellulalae complex. These results suggest that the peptide aa 121-145 may be exploited as a peptide-based vaccine candidate against tuberculosis and other mycobacterial diseases.

Leprosy and tuberculosis co-infection: clinical and immunological report of two cases and review of the literature.

A review of the records of patients seen between 2004 and 2011 at the Dermatology Clinic of the São Paulo University Medical School showed that only two leprosy patients had been co-infected with tuberculosis (TB). One patient showed a type 1 leprosy reaction during the first 3 months of treatment of pleural TB and in the other patient, pulmonary TB was diagnosed during the first 3 months of treatment of a type 1 leprosy reaction. Both patients showed normal cellular immune response tests, including those of the interferon-gamma (IFN-γ)/interleukin 12 (IL-12) axis. Although both mycobacterial infections are endemic in developing countries like Brazil, the co-infection has hardly been reported in the last decade. There is no suitable explanation for this observation. The reports on the interaction between the two mycobacteria are highly speculative: some studies suggest that leprosy, especially the anergic form, would predispose to TB, whereas other investigations suggested an antagonism between the two diseases.

Evaluation of a simplified IS6110 PCR for the rapid diagnosis of Mycobacterium tuberculosis in an area with high tuberculosis incidence.

PURPOSE: To assess the diagnostic yield of a simplified IS6110-PCR in an area with high tuberculosis incidence. METHODS: Pulmonary (218) and extrapulmonary (121) samples were collected from 236 patients including smearpositive leprosy patients. All samples were processed to detect acidfast bacilli by microscopy, culture on solid media and PCR. To remove PCR inhibitors, three washing steps of the decontaminated pellet were included before mycobacterial cell lysis by heat treatment. No detergents, enzymes, or chelating agents were used. From the 339 samples, 34 were selected basing on their large volume and were tested by the commercial kit GenoType Mycobacteria Direct (GTMD) (VER 4, Hain Lifescience, Germany) in addition to the tests cited above. RESULTS: The overall sensitivity and specificity of PCR were 93.8 and 98.6% for pulmonary samples, 63.6 and 100% for extrapulmonary samples, respectively. The assay detected MTC in 94.2% of smear positive samples with a positive predictive value of 100%. No inhibition was found among seven samples that were PCR negative but bacteriological confirmed as containing Mycobacterium tuberculosis. No false positive result occurred with samples from leprosy patients. The sensitivities for PCR and GTMD were 81.8 and 75%, respectively. CONCLUSION: PCR could efficiently complement conventional bacteriological tools for the rapid diagnosis of tuberculosis but cannot replace them.

Evaluation of the diagnostic value of measuring IgG, IgM, and IgA antibodies to mycobacterial A60 antigen in active tuberculosis.

The purpose of the present study was to evaluate the clinical usefulness of detection of serum immunoglobulin A (IgA), IgG, and IgM antibodies raised against the mycobacterial A60 antigen for the diagnosis and discrimination of active tuberculosis (TB) from other pulmonary diseases. Three commercially available ELISA kits (IgA, IgG, and IgM) (ANDA Biologicals, Strasbourg, France) were evaluated simultaneously in 246 serum samples from 3 groups of patients: group I, 171 patients with active TB (128 pulmonary TB and 43 extrapulmonary TB); group II, 73 patients with pulmonary non-TB diseases; and group III, 2 leprosies patients. The sensitivities of tests ranged from 31.3% (IgA) to 94% (IgG) in pulmonary TB patients and from 21% (IgA) to 84% (IgG) in extrapulmonary TB patients. The specificities of assays varied from 92% (IgG) to 96% (IgA) in the pulmonary non-TB group. Combination of IgG with IgA and/or IgM does not improve its sensitivity. Clinical use of the A60-based serodiagnostic IgG assay is of great value for the rapid diagnosis and discrimination between active TB and pulmonary non-TB diseases. Moreover, this test could be used to increase diagnostic accuracy, especially for smear-negative TB cases, which are difficult to diagnose.

What has Karonga taught us? Tuberculosis studied over three decades.

This paper summarises tuberculosis (TB) research over almost 30 years in Karonga District, northern Malawi, an area typical of much of rural Africa. The dominant factor has been the human immunodeficiency virus (HIV), which arrived in the district about 1980, leading to an increase in TB incidence to a peak of approximately 65 smear-positive pulmonary cases per 100000 population in 2000. Tuberculin surveys indicate annual risks of Mycobacterium tuberculosis infection of approximately 1%; thus, most of the population is uninfected and at risk of primary infection and disease. Molecular epidemiological studies demonstrate that about two thirds of TB arises from recent infection, but recognisable recent contact is responsible for only about 10% of disease. By 2001, 57% of TB was directly attributable to HIV, implying that it would have declined were it not for HIV. HIV infection increases the risk of TB most among young adults, and greatly increases the risk of recurrence from new infection after treatment. Mortality rates in the HIV-infected are high, but there is no association of HIV with drug resistance. Other risk factors with relatively smaller effects include age and sex, contact, several genetic polymorphisms and area. Neither one nor two doses of the bacille Calmette-Guérin (BCG) vaccine provides protection against adult pulmonary TB, despite protecting against leprosy. Skin test surveys, cohort studies and comparative immunological studies with the UK suggest that exposure to environmental mycobacteria provides some protection against TB and that BCG's failure is attributable partly to this widespread heterologous exposure masking effects of the vaccine. Drug resistance has remained constant (<10%) over more than 20 years. Immunotherapy with M. vaccae provided no benefits, but treatment of HIV-positive patients with cotrimoxazole reduced mortality. The Karonga programme illustrates the value of long-term population-based studies to investigate the natural history of TB and to influence TB control policy. Current studies focus on immunological markers of infection, disease and protection, and on elucidating the impact of antiretroviral treatment on TB incidence at population level.

The phenolic glycolipid of Mycobacterium tuberculosis differentially modulates the early host cytokine response but does not in itself confer hypervirulence.

Mycobacterium tuberculosis possesses a diversity of potential virulence factors including complex branched lipids such as the phenolic glycolipid PGL-tb. PGL-tb expression by the clinical M. tuberculosis isolate HN878 has been associated with a less efficient Th1 response and increased virulence in mice and rabbits. It has been suggested that the W-Beijing family is the only group of M. tuberculosis strains with an intact pks1-15 gene, required for the synthesis of PGL-tb and capable of producing PGL-tb. We have found that some strains with an intact pks1-15 do not produce PGL-tb while others may produce a variant of PGL-tb. We examined the early host cytokine response to infection with these strains in vitro to better understand the effect of PGL-tb synthesis on immune responses. In addition, we generated a PGL-tb-producing H37Rv in order to determine the effect of PGL-tb production on the host immune response during infection by a strain normally devoid of PGL-tb synthesis. We observed that PGL-tb production by clinical M. tuberculosis isolates affected cytokine production differently depending on the background of the strain. Importantly, while ectopic PGL-tb production by H37Rv suppressed the induction of several pro- and anti-inflammatory cytokines in vitro in human monocytes, it did not lead to increased virulence in infected mice and rabbits. Collectively, our data indicate that, while PGL-tb may play a role in the immunogenicity and/or virulence of M. tuberculosis, it probably acts in concert with other bacterial factors which seem to be dependent on the background of the strain.

False-positive amplified Mycobacterium tuberculosis direct test results for samples containing Mycobacterium leprae.

Nucleic acid amplification tests are widely used in mycobacteriology laboratories to rapidly detect Mycobacterium tuberculosis complex directly in clinical specimens. A positive result provides an early diagnosis of tuberculosis, allowing initiation of appropriate therapy and public health measures.

Elevated serum CCL2 concomitant with a reduced mycobacterium-induced response leads to disease dissemination in leprosy.

Mycobacterium leprae and Mycobacterium tuberculosis are successful intracellular pathogens which down regulate host immune responses. T-cell interferon-gamma (IFNgamma) and macrophage tumour necrosis factor-alpha (TNFalpha) activate chemokines such as, C-C chemokine ligand-2 (CCL2) and CCL5, which play a role in granuloma formation. Lepromatous leprosy is characterized by defective granulomas with lowered T-cell- and macrophage-mediated responses. Tuberculosis (TB) can be localized to the lung, whereby discreet granulomas are formed. The role of chemokines in leprosy infections is as yet unclear. We compared chemokine responses in lepromatous leprosy and pulmonary tuberculosis patients. Circulating serum CCL2 was raised while CCL5 was lowered in leprosy, as compared with TB patients and healthy controls. However, both Mycobacterium bovis BCG- (P=0.08) and M. leprae-induced (P=0.05) CCL2 secretion was reduced in leprosy. In leprosy, BCG induced greater CCL2 (P=0.01), TNFalpha (P=0.02) and somewhat greater CCL5 (P=0.08) than M. leprae, while CXCL8 induction was comparable. Overall levels of Mycobacterium-induced CCL2, TNFalpha and CXCL8 were two to threefold lower, and CCL5 was 10-fold lower in leprosy as compared with TB. Reduced inducible CCL2 combined with a lowered TNFalpha response in lepromatous leprosy may contribute to the unrestricted growth and dissemination of mycobacteria found in the disease.