Current World Health Organisation targets calling for an end to the global tuberculosis (TB) epidemic by 2035 require a dramatic improvement in current case-detection strategies. A reliance on passive case finding (PCF) has resulted consistently, in over three million infectious TB cases per year, being missed by the health system, leading to ongoing transmission of infection within families and communities. Active case finding (ACF) for TB has been recognized as an important complementary strategy to PCF, in order to diagnose and treat patients earlier, reducing the period of infectiousness and therefore transmission. ACF may also achieve substantial population-level TB control. Local TB epidemiology and the resources available in each setting will influence which populations should be screened, and the types of ACF interventions to use for maximal impact. TB control programs should begin with the highest risk groups and broaden their activities as resources allow. Mathematical models can help to predict the population-level effects and the cost-effectiveness of a variety of ACF strategies on different risk populations.

[ABSTRACT]  [FULL TEXT]  [PDF]  [Mobile Full text]  [EPub] [CITATIONS]

Objective/background: Microbial infections such as tuberculosis is a major cause of mortality worldwide. Plant-derived phytochemicals have a long history of providing much-needed novel therapeutics. Triterpenoids are among the prominent phytochemicals that possess numerous biological activities. Among them is maslinic acid (MA), a biologically active olean-type pentacyclic triterpenoid. In search of a novel antimicrobial agent, we aimed to evaluate the antimicrobial potential of MA. Methods: Antibacterial and antifungal activity was evaluated through the agar well diffusion method. Antitubercular activity was analysed through the agar well diffusion and disc diffusion methods, respectively. Antioxidant capacity was determined through assays for total antioxidant capacity, 2,2-diphenyl-1-picrylhydrazyl radical scavenging, hydrogen peroxide radical scavenging, and Fe³⁺ reducing power. The program Prediction of Activity Spectra for Substances was used to calculate the possible biological activity of MA. Results: MA showed dose-dependent antioxidant activity similar to that of ascorbic acid. It had no inhibitory effect on bacterial strains, but it had moderate activity against the fungi Aspergillus flavus and Ustilago maydis, with Aspergillus niger being the most sensitive to MA. MA also exhibited strong antimycobacterial activity. Probable antioxidant, antibacterial, and antifungal activity of MA based on software calculations are 0.479, 0.363 and 0.589 respectively. Conclusion: This work provides scientific evidence of the antioxidant, antifungal, and antimycobacterial activities of MA, showing its potential application in the development of natural antioxidants and antimicrobial agents for the agro-food and pharmaceutical industries.

[ABSTRACT]  [FULL TEXT]  [PDF]  [Mobile Full text]  [EPub] [CITATIONS]

Looking at the chapter on “natural history” in any tuberculosis (TB) reference book, there is a kind of certainty regarding TB in adults. That is the concept of “post-primary” TB described as the reactivation of dormant bacilli hidden in an old lesion developed during infancy due to a type of local immunosuppression. Intriguingly, this concept involves at least two major uncertainties: how can dormant bacilli remain for such a long period, almost a lifetime, in an old lesion, taking into account granuloma dynamism; and what sort of local immunosuppression is the one that facilitates reactivation? The controversy between reactivation and exogenous reinfection as the cause of active TB started very soon in TB research. Interestingly, this “balance” was disturbed in the 1960 s when the “Unitary Concept” became very successful in supporting the reactivation dogma. The “Unitary Concept” was mainly based on the data of tuberculin surveillance during the pre-antibiotic era as well as the data obtained from experimental modelling in animals. At the same time, the “Three-risks model” appeared to explain the relationship between the risk of infection and TB incidence, granting reinfection a key role in adult TB together with primary infection. This role was reinforced by the studies of recurrence based on molecular epidemiology, and a better knowledge of the immune response, granuloma dynamics, and lung physiology. Now it is a matter of taking it into account when designing new prophylactic and therapeutic strategies and also reflecting it in text books to better illustrate to our students.

[ABSTRACT]  [FULL TEXT]  [PDF]  [Mobile Full text]  [EPub] [CITATIONS]

Tuberculosis is one of the leading causes of death by Mycobacterium tuberculosis (Mtb) affecting millions of people worldwide. Mycobacterium species enter host macrophages during infection and target various cellular organelles and their function for their own benefit. Mitochondria appear to be among the important targets for bacterial pathogens. Mtb and other pathogenic bacteria secrete various proteins that initiate structural changes in mitochondria to modulate its function. Additionally, virulent mycobacteria interfere with the balance between pro- and anti-apoptotic factors to inhibit apoptosis and, in later stages, promote necrosis. Furthermore, mitochondria perform multiple biological functions in the cell, and the inhibition of these functions by bacterial proteins promotes Mtb survival, growth, and successful infection.

[ABSTRACT]  [FULL TEXT]  [PDF]  [Mobile Full text]  [EPub] [CITATIONS]

Objective/Background: Multidrug-resistant tuberculosis (MDR-TB) is growing globally and becoming a major challenge for national TB control programs. Therefore, rapid identification of MDR strains of Mycobacterium tuberculosis and monitoring their transmission could contribute significantly to the control of TB. The GenoType MTBDRplus assay has been recommended by the World Health Organization to identify rifampicin (RIF)- and isoniazid (INH)-resistant M. Tuberculosis isolates. This study was carried out to evaluate the performance of the GenoType MTBDRplus assay for the detection of RIF- and INH-resistant M. Tuberculosis isolates in central Ethiopia. Methods: A total of 279 M. Tuberculosis strains isolated from active TB cases in central Ethiopia were evaluated for their drug sensitivity by the conventional drug-susceptibility test (DST) and compared with data derived from the GenoType MTBDRplus assay. The DST served as the gold standard for evaluating the GenoType MTBDRplus assay. Results: The sensitivity and specificity of the GenoType MTBDRplus assay for the detection of RIF-resistant M. Tuberculosis isolates were 80.0% and 99.6%, respectively. Its sensitivity and specificity for the detection of INH-resistant M. Tuberculosis isolates were 82.7% and 99.6%, respectively, whereas they were 75.0% and 100%, respectively, for the detection of MDR M. Tuberculosis strains. The concordances of the GenoType MTBDRplus assay and the conventional DST for the detection of RIF and INH susceptibility were 80% (8/10) and 86.2% (25/29), respectively. Furthermore, the concordance of the two tests for the detection of MDR M. Tuberculosis strains was 75%. Specific mutations were detected in 55.6% (5/9) of the RIF-resistant isolates, with the highest mutation rate (33.3%) for the rpoB gene (Codon S531L). For INH-resistant isolates, the highest mutation rate (88.8%) related to a katG mutation (Codon S315T1). Conclusion: The findings of this study revealed that the GenoType MTBDRplus assay has high sensitivity and specificity for the detection of RIF and INH resistance. These preliminary data support the notion that the assay should be considered as an alternative to the DST for the characterization of MDR in M. Tuberculosis isolates and the control of TB.

[ABSTRACT]  [FULL TEXT]  [PDF]  [Mobile Full text]  [EPub] [CITATIONS]

Tuberculosis (TB) ranks alongside HIV as the leading cause of death worldwide, killing 1.5million people in 2014. Traditional laboratory techniques do not provide sufficiently rapid results to inform clinicians on appropriate treatment, especially in the face of increasingly prevalent drug-resistant TB. Rapid molecular methods such as PCR and LAMP are vital tools in the fight against TB, however, rapid advances in next generation sequencing (NGS) technology are allowing increasingly rapid and accurate sequencing of entire bacterial genomes at ever decreasing cost, providing unprecedented depth of information. These advances mean NGS stands to revolutionise the diagnosis and epidemiological study of Mycobacterium tuberculosis infection. This review focuses on current applications of NGS for TB diagnosis including sequencing cultured isolates to predict drug resistance and, more desirably, direct diagnostic metagenomic sequencing of clinical samples. Also discussed is the potential impact of NGS on the epidemiological study of TB and some of the key challenges that need to be overcome to enable this promising technology to be translated into routine use.

[ABSTRACT]  [FULL TEXT]  [PDF]  [Mobile Full text]  [EPub] [CITATIONS]

Objective/Background: Tuberculosis (TB) remains a global threat, claiming one-third of the population annually. The ever increasing emergence of multidrug-resistant TB (MDR-TB) is the major impediment to effective anti-TB therapy. Under such circumstances, deciphering the antimycobacterial potential of natural compounds has gained considerable prominence. This study evaluated the antimycobacterial activity of vanillin (Van), a natural food-flavoring agent and preservative, along with its potential mechanisms of action. Methods: Drug susceptibilities were performed using broth microdilution, spot, and filter-disc assays. Membrane damage was studied by nitrocefin hydrolysis and electron microscopy. Virulence attributes were assessed by biofilm formation and cell adherence. Iron availability was estimated by enzymatic (ferroxidase) assay. Results: We found that the antimycobacterial activity of Van against Mycobacterium smegmatis (a surrogate of Mycobacterium tuberculosis) is 125 μg/mL. Additionally, we observed disruption of membrane homeostasis in the presence of Van, as revealed by enhanced membrane permeability and transmission electron microscopy images showing a disturbed cell envelope. Concomitant with our findings, we also observed that Van leads to enhanced drug susceptibility to membrane targeting known anti-TB drugs. Furthermore, Van affects significant virulence traits of Mycobacterium by inhibiting biofilm formation and cell adhesion. Finally, we observed that Van disrupted iron homeostasis as displayed by hypersensitivity to iron deprivation. Conclusion: The results established for the first time that Van could be an effective antimycobacterial agent that could be exploited further in treating mycobacterial infections.

[ABSTRACT]  [FULL TEXT]  [PDF]  [Mobile Full text]  [EPub] [CITATIONS]

Objective/background: Cell wall-deficient bacterial forms (L-forms) may occur along with resistance to factors that trigger their appearance. It is of interest to study the relationship between the L-form transformation of Mycobacterium tuberculosis and the exhibition of drug tolerance to ethambutol (EMB), an inhibitor of cell wall synthesis. Methods: L-form variant was produced from a sensitive EMB strain of M. Tuberculosis through a cryogenic stress treatment protocol and was subsequently cultivated in Middlebrook 7H9 semisolid medium, containing EMB in a minimal inhibitory concentration of 2 mg/L. Susceptibility to EMB of the parental strain and its L-form variant was evaluated phenotypically and using polymerase chain reaction-restriction fragment length polymorphism assay targeting a mutation in the embB306 gene fragment. Results: In contrast to the sensitivity to EMB of the parental strain, its L-form variant showed phenotypic resistance to high concentrations of EMB (16 mg/L), but the mutation in embB306 was not found. Electron microscopy observation of the L-form variant showed a heterogenic population of bacteria, with different degrees of cell wall deficiency, as well as cells of protoplastic type without cell walls. Of special interest were the observed capsule-like structures around the L-form cells and the biofilm-like matrix produced by the L-form population. Conclusion: We suggest that the expression of phenotypic resistance to EMB in M. Tuberculosis can be associated with alterations or loss of cell walls in L-form bacteria, respectively, which results in a lack of a specific target for EMB action. In addition, production of capsule-like structures and biofilm matrix by L-forms could contribute to their resistance and survival in the presence of antibacterial agents.

[ABSTRACT]  [FULL TEXT]  [PDF]  [Mobile Full text]  [EPub] [CITATIONS]

Mycobacterium tuberculosis, the causative agent of tuberculosis, is an intracellular pathogen with several survival mechanisms aimed at subverting the host immune system. Apoptosis has been shown to be mycobactericidal, to activate CD8⁺ T cells, and to be modulated by mycobacterial proteins. Since few mycobacterial proteins have so far been directly implicated in the interactions between M. Tuberculosis and host cell apoptosis, we screened M. Tuberculosis H₃₇Rv transposon mutants to identify mutants that fail to inhibit cell death (FID). One of these FID mutants, FID19, had a transposon insertion in Rv2456c and is important for survival in host cells. The lack of the protein resulted in enhanced caspase-3 mediated apoptosis, which is probably due to an inability to activate nuclear factor-κB. Additionally, FID19 infection enhanced polyfunctional CD8⁺ T cells and induced a higher frequency of interferon-γ secreting immune cells in a murine model. Taken together, our data suggest that Rv2456c is important for the survival of H₃₇Rv by subduing the innate and ultimately adaptive immune responses of its host by preventing apoptosis of the infected cell. Better understanding of the host-mycobacterial interactions may be beneficial to develop novel drug targets and engineer more efficacious vaccine strains against tuberculosis.

[ABSTRACT]  [FULL TEXT]  [PDF]  [Mobile Full text]  [EPub] [CITATIONS]

Background/Objective: Tuberculous pleurisy is a diagnostic challenge due to its nonspecific clinical presentation, paucibacillary nature of the effusion together with the inefficiency of conventional laboratory methods motivating the evaluation of variable diagnostic strategies. Methods: Using thoracoscopy, the pleural cavity of 50 patients with undiagnosed exudative pleural effusion were fully examined and biopsy specimens of affected parietal pleura were taken under direct vision. Pleural fluid and biopsy specimen were subjected to microscopic examination (direct and after cytocentrifugation), culture, PCR, and histopathological examination. Results: The pleural biopsy specimens proved to have a higher detection rate of tubercle bacilli than pleural fluid. Also, cytocentrifugation improved the sensitivity of microscopic detection for both pleural fluid and biopsy specimens. Conclusion: The combination of microbiological results and histopathology examination of the pleural biopsy specimens is essential for the diagnosis of tuberculous pleurisy, as microbiological examination of pleural biopsy specimens has proved to have a higher detection rate than pleural fluid examination.

[ABSTRACT]  [FULL TEXT]  [PDF]  [Mobile Full text]  [EPub] [CITATIONS]

Objective/background: The objective/background of this work was to study the efficacy and safety of quercetin and polyvinylpyrrolidone (QP) in the treatment of patients with newly diagnosed destructive pulmonary tuberculosis in comparison with standard antimycobacterial therapy. Materials and methods: The study involved 124 patients aged between 20 years and 70 years with newly diagnosed destructive pulmonary tuberculosis. Patients were allocated to two groups. The first (control) group of patients received standard antimycobacterial and pathogenetic therapy and included 31 (25.00±3.89%) patients. The second (main) group of patients received QP therapy in addition to chemotherapy and included 93 (75.00±3.89%) patients. Results: Intoxication symptoms in the second group were reduced following 1.33±0.15 months, whereas in the first group intoxication symptoms were reduced following 2.64±0.20 months, p < .001. Conclusion: Administration of QP combined with chemotherapy in patients with newly diagnosed destructive pulmonary tuberculosis resulted in a comparatively quick reduction of disease manifestation.

[ABSTRACT]  [FULL TEXT]  [PDF]  [Mobile Full text]  [EPub] [CITATIONS]

The use of bronchoscopes has increased in tuberculosis (TB) diagnostics to circumvent the diagnostic challenges that are associated with low sputum volume and smear-negative TB. In healthcare facilities situated in low income countries that have a high burden of TB, adequate decontamination of bronchoscopes is a challenge and often overlooked to save on time and costs. This amplifies the risk of outbreaks and pseudo-outbreaks due to Mycobacterium tuberculosis and nontuberculosis mycobacteria. In this minireview, we review published literature of contaminated bronchoscopes causing pseudo-outbreaks of M. Tuberculosis and nontuberculosis mycobacteria in an effort to determine common sources, and possible mitigation strategies in low-resource settings.

[ABSTRACT]  [FULL TEXT]  [PDF]  [Mobile Full text]  [EPub] [CITATIONS]

Objective/background: Early initiation of therapy in patients with tuberculosis is imperative for its control. Conventional methods of susceptibility testing such as the proportion method (PM) require visual detection and counting of colonies that takes up to 6 weeks. Rapid and simple phenotypic methods that have been endorsed by the World Health Organization can serve as alternatives. Methods: In this study, we evaluated the colorimetric nitrate reductase assay, which utilizes the detection of nitrate reduction as an indicator of growth much earlier compared with PM (within 7–14 days). The susceptibility of 75 clinical isolates of Mycobacterium tuberculosis to four first-line antitubercular drugs was tested by nitrate reductase assay and compared with the standard PM. In this assay, inoculation was done on both drug-free and drug-containing Löwenstein–Jensen medium containing sodium nitrate. After incubation for 7–14 days, reduction to nitrite was taken as an indicator of growth, which was detected by color change on addition of Griess reagent. Results: Agreement between nitrate reductase assay and PM was 100% for rifampicin, 97.30% for isoniazid, 93.30% for streptomycin, and 98.60% for ethambutol. Cost/isolate with this assay was found to be approximately two times lesser than that of PM. All results were obtained in 7–14 days by nitrate reductase assay, which was significantly rapid compared with 42 days taken for obtaining results by PM. Conclusion: Nitrate reductase assay can be used as a rapid and inexpensive method for drug-susceptibility testing of M. Tuberculosis for first-line antitubercular drugs without compromising accuracy of standard methods.

[ABSTRACT]  [FULL TEXT]  [PDF]  [Mobile Full text]  [EPub] [CITATIONS]

The percentage of extrapulmonary tuberculosis (EPTB) among new and relapse tuberculosis cases in South Asia (Afghanistan, Pakistan, India, and Bangladesh) ranged from 19% to 23% in 2014. While tuberculosis was reportedly more prevalent in males, a higher preponderance of EPTB was observed in females. National tuberculosis control programs are highly focused on pulmonary tuberculosis. This creates gaps in the surveillance, diagnosis, and study of EPTB among females, which is especially pronounced in the South Asian setting. We have reviewed recently published literatures from January 2010 to June 2016 reporting EPTB in females with a view to evaluate the current epidemiology, risk factors, diagnostic modalities, and treatment outcomes. We report significant gaps in the surveillance of EPTB among women in South Asia, emphasizing the need for greater focus on EPTB in females to overcome current surveillance and knowledge gaps.

[ABSTRACT]  [FULL TEXT]  [PDF]  [Mobile Full text]  [EPub] [CITATIONS]

Objective/background: Fluoroquinolones (FQs) are important anti-tuberculous drugs for the treatment of multidrug-resistant (MDR) tuberculosis. Resistance to FQs leads to fewer options for treatment of tuberculosis (TB), and infection with such strains may also require longer treatment duration. Trends of resistance in Mycobacterium tuberculosis (MTB) are indicators of MTB-resistance evolution. Drivers of such resistance need to be understood and studied to inform preventive strategies. Methods: Here, we present FQ-resistance rates and trends in Pakistan from 2010 to 2015 and compare rates with FQ-consumption data and rates in other community pathogens. Results: Our results reveal a recent decrease in FQ-resistance rates in MTB, but an increase in resistance for Haemophilus influenzae and Shigella spp. Correlation of FQ resistance with FQ consumption at the population level was weak for MTB, although strong associations were noted for H. influenzae and Shigella spp. Conclusion: We discuss the possible reasons for the decrease in resistance rates in TB, putative drivers of resistance other than volume of FQ consumption, and the possible impact of the National Tuberculosis Programme and drug regulatory activities.

[ABSTRACT]  [FULL TEXT]  [PDF]  [Mobile Full text]  [EPub] [CITATIONS]

Objective/background: Tuberculosis (TB) is a worldwide public health problem. It is a contagious and grave disease caused by Mycobacterium tuberculosis. Current drugs such as isoniazid, pyrazinamide, and rifampicin used for the treatment of tuberculosis are potentially hepatotoxic and can lead to drug hepatitis. In order to improve the follow-up of TB patients in Cameroon, we carried out a study which aimed to evaluate the hepatotoxicity risk factors associated with anti-TB drugs. Methods: The studies were performed on 75 participants who had visited the Loum District Hospital located in the littoral region of Cameroon for their routine consultation. Participants have been selected based on pre-established criteria of inclusion and exclusion. Prior to the informed consent signature, patients were given compelling information about the objective and the result output of the study. They were questioned about antioxidant food and alcohol consumption as well as some clinical signs of hepatotoxicity such as fever, nausea, vomiting, and tiredness. The collected blood was tested for the determination of biochemical markers (transaminases and C-reactive protein) using standard spectrophotometric methods. Results: Biochemical analysis of samples showed a significant increase (p < .05) of aspartate aminotransferase and alanine aminotransferase values in TB patients coinfected with human immunodeficiency virus/AIDS (33.28±16.58UI/L and 30.84±17.17UI/L, respectively) compared with the respective values of the controls (16.35±5.31UI/L and 16.45±4.83UI/L). Taking individually, the liver injury patient percentage of TB patients was significant compared to TBC when considering alanine aminotransferase and aspartate aminotransferase parameters. When considering risk factors, antioxidant food consumption significantly reduced the liver injury patient percentage for the above parameters, whereas an opposite situation was observed with alcohol consumption between TB-coinfection and TB patients. Regarding the C-reactive protein results, the percentage of positive tests was very high among coinfected patients (40%) compared with the control (15%). The interactions between parameters related to alcohol consumption and intake of antioxidant foods showed a slight decrease in activity compared with interactions without food. Conclusion: The results showed that human immunodeficiency virus status and alcohol consumption constitutes aggravating factors for the occurrence of hepatic toxicity. In addition, the consumption of antioxidant foods simultaneously with TB drugs help in reducing the hepatotoxic effects of these drugs.

[ABSTRACT]  [FULL TEXT]  [PDF]  [Mobile Full text]  [EPub] [CITATIONS]

Objective/background: The objectives of this study are to describe the acid-fast bacilli (AFB) yield of a front-loaded scheme in which an additional on-the-spot specimen (Xspot [Xs]) was collected 1 h after the first spot specimen and to compare the default rate between the front-loaded and standard schemes. The performance of the front-loaded sputum microscopy was also compared with the standard World Health Organization (WHO) method for the diagnosis of pulmonary tuberculosis (PTB) in Anambra State, Nigeria. Methods: A total of 1487 individuals with presumptive pulmonary TB participated. Participants' age ranged from 15 years and above. Three sputum specimens were submitted as spot–early morning–spot. An additional specimen (Xs) was submitted 1 h after the first spot. The sputum smears were stained using the Ziehl–Neelsen technique. Results: A total of 183 (12.3%) patients were AFB positive. The front-loaded scheme identified 182 (99%) TB patients, whereas the standard scheme identified 183 (100%) TB patients. The difference was not statistically significant (p > .05). The first two specimens of each scheme (S–Xs vs. S–M) identified 176 (96.2%) and 181 (98.9%) of PTB patients, respectively. Neither difference was statistically significant (p > .05). Default during the diagnostic process was 11% in the standard but only 0.7% in the front-load scheme. The difference was significant (p < .05). Conclusion: Front-loaded smear microscopy has similar performance compared with the standard scheme. More presumptive PTB cases defaulted in the standard than in the front-loaded scheme. Front-loaded smear microscopy could therefore be used in the diagnosis in PTB in Anambra State.

[ABSTRACT]  [FULL TEXT]  [PDF]  [Mobile Full text]  [EPub] [CITATIONS]

[FULL TEXT]  [PDF]  [Mobile Full text]  [EPub]