Antimicrobial activity of carvacrol and its derivatives on Mycobacterium spp.: systematic review of preclinical studies.

Background: The scope of the study was to analyze original preclinical studies on the antimicrobial effects of carvacrol and derivatives on the Mycobacterium genus. Materials & methods: According to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement, four databases (PubMed, Web of Science, SCOPUS and EMBASE) were searched. Results: The search retrieved 392 records, of which 11 papers were selected. Heterogeneity in the techniques and mycobacterial targets was observed. Carvacrol demonstrated synergistic antimycobacterial activity with rifampicin against multidrug-resistant Mycobacterium tuberculosis on membranes and biofilms. In silico approaches showed specific targets in mycobacteria, by inhibition and molecular docking assays, on the enzyme chorismate mutase and the heat shock protein 16.3. Conclusion: Carvacrol has been shown to be a scaffold candidate for future molecules with activity against mycobacteria.

Synthesis of 1,3,4-oxadiazoles with 4-methoxynaphthalene ring: discovering new compounds with antimicrobial activity.

Background: Paracoccidioidomycosis (PCM) is a systemic infection caused by Paracoccidioides spp. (Pb). PCM can be associated or clinically confused with tuberculosis (TB), another pulmonary infection, caused by Mycobacterium tuberculosis (Mtb). Futhermore, the long treatment time of TB and PCM and the cases of TB drug resistance impose difficulties for the cure of these diseases. Results: New 1,3,4-oxadiazoles containing the 4-methoxynaphthalene ring were synthesized and their antimicrobial activity was evaluated against Pb and Mtb. The derivative 6n (with 2-hydroxy-5-nitrophenyl subunit) is the most promising of the series. Conclusion: The 1,3,4-oxadiazole 6n can be used as a prototype drug candidate, with anti-Pb and anti-MTb activities, showing a broad-spectrum profile for the treatment of both pulmonary infections.

Binding of piperine to mycobacterial RNA polymerase improves the efficacy of rifampicin activity against Mycobacterium leprae and nontuberculous mycobacteria.

Piperine (PPN) is a known inhibitor of efflux pumps in Mycobacterium tuberculosis and in vitro synergism with rifampicin (RIF) has been proven. The current study evaluates the activity of PPN and synergism with RIF in rapidly and slowly growing nontuberculous mycobacteria (NTM). Also, to propose a possible mechanism of interaction of PPN with M. leprae (Mlp) RNA polymerase (RNAp). Minimal inhibitory concentration and drug combination assay was determined by resazurin microtiter assay and resazurin drug combination assay, respectively. In silico evaluation of PPN binding was performed by molecular docking and molecular dynamics (MD). PPN showed higher antimicrobial activity against rapidly growing NTM (32-128 mg/L) rather than for slowly growing NTM (≥ 256 mg/L). Further, 77.8% of NTM tested exhibited FICI ≤ 0.5 when exposed to PPN and RIF combination, regardless of growth speed. Docking and MD simulations showed a possible PPN binding site at the interface between ß and ß' subunits of RNAp, in close proximity to the trigger-helix and bridge-helix elements. MD results indicated that PPN binding hindered the mobility of these elements, which are essential for RNA transcription. We hypothesize that PPN binding might affect mycobacterial RNAp activity, and, possibly, RIF activity and that this mechanism is partially responsible for synergic behaviors with RIF reported in vitro. Communicated by Ramaswamy H. Sarma.

Polymyxin B Activity Rescue by (-)-Camphene-Based Thiosemicarbazide Against Carbapenem-Resistant Enterobacterales.

Due to the significant shortage of therapeutic options for carbapenem-resistant Enterobacterales (CRE) infections, new drugs or therapeutic combinations are urgently required. We show in this study that (-)-camphene-based thiosemicarbazide (TSC) may act synergistically with polymyxin B (PMB) against CRE, rescuing the activity of this antimicrobial. With the specific aim of a better molecular understanding of this effect caused by the presence of TSC, theoretical calculations were also performed in this study. Based on these findings, it is concluded that the presence of TSC moieties contributes to significant changes in the hydrogen atom charge of PMB structure, which trend more positives for the PMB/TSC system studied. This could lead to the formation of stronger hydrogen bonds in the Enterobacterales active site and, thus contribute to a molecular understanding of the PMB rescue of activity promoted by the presence of TSC moiety. As such, the clinical potential of these drug combinations requires further evaluation.

Cord factor producer Mycobacterium abscessus subsp. bolletii in asymptomatic immunocompetent host sputa samples

Abstract We report a case of Mycobacterium abscessus subsp. bolletii colonization in upper respiratory tract of an immunocompetent patient, who was misdiagnosed as tuberculosis by Acid Fast Bacilli (AFB) and cord factor formation observed directly from the sputa culture in liquid medium. This fact reflected a significant impact on the individual case's life and showed the importance to identify the mycobacteria isolated from clinical sample at species level, and to determine the true implication of nontuberculous mycobacteria (NTM) detected in clinical samples.

Detection of Group B Streptococcus in vaginal swabs, without prior enrichment, by qPCR.

Group B Streptococcus (GBS) infection in newborns during childbirth can result in death. We described a method to detect GBS from vaginal swabs in pregnant women, without prior enrichment, using real-time polymerase chain reaction (qPCR), and compared its results to the culture method. The qPCR outperforms culture method.

Activity of (-)-Camphene Derivatives Against Mycobacterium tuberculosis in Acidic pH.

BACKGROUND: For more than 60 years, the lack of new anti-tuberculosis drugs and the increase of resistant Mycobacterium tuberculosis lineages exhibit a therapeutic challenge, demanding new options for the treatment of resistant tuberculosis. OBJECTIVE: Herein, we determined the (i) activities of (-)-camphene and its derivatives and (ii) combinatory effect with pyrazinamide (PZA) against Mycobacterium tuberculosis in acidic pH and (iii) cytotoxicity on VERO cells. METHODS: The activity of (-)-camphene and its 15 derivatives was determined in M. tuberculosis H37Rv in culture medium at pH 6.0 by Resazurin Microtiter Assay Plate (REMA). The activity and combinatory study of three (-)-camphene derivatives with PZA was carried out on seven multidrugresistant (MDR) clinical isolates by REMA and Checkerboard, respectively. The assay of 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) bromide in VERO cells was used to determine the derivatives' cytotoxicity. RESULTS: Four (-)-camphene derivatives, (4), (5a) (5d) and (5h), showed a reduction in the MIC value at pH 6.0 compared to the MIC detected at pH 6.8 in M. tuberculosis H37Rv and multidrug resistant clinical isolates. Three (-)-camphene derivatives, (4), (5d) and (5h), showed synergistic effect (FICI ≤ 0.5) combined with PZA and were more selective for M. tuberculosis than VERO cell (selective index from 7.7 to 84.2). CONCLUSION: Three (-)-camphene derivatives have shown to be promising anti-TB molecule scaffolds due to their low MIC values in acidic pH against MDR M. tuberculosis clinical isolates, synergism with PZA and low cytotoxicity.

Antituberculosis Activities of Lapachol and ß-Lapachone in Combination with Other Drugs in Acidic pH.

Background: The treatment of multidrug-resistant tuberculosis (MDR-TB) is a challenge to be overcome. The increase of resistant isolates associated with serious side effects during therapy leads to the search for substances that have anti-TB activity, which make treatment less toxic, and also act in the macrophage acidic environment promoted by the infection. Objective: The aim of this study was to investigate lapachol and ß-lapachone activities in combination with other drugs against Mycobacterium tuberculosis at neutral and acidic pH and its cytotoxicity. Design: Inhibitory and bactericidal activities against M. tuberculosis and clinical isolates were determined. Drug combination and cytotoxicity assay were carried out using standard TB drugs and/or N-acetylcysteine (NAC). Results: Both naphthoquinones presented activity against MDR clinical isolates. The combinations with the first-line TB drugs demonstrated an additive effect and ß-lapachone+NAC were synergic against H37Rv. Lapachol activity at acidic pH and its association with NAC improved the selectivity index. Lapachol and ß-lapachone produced cell morphological changes in bacilli at pH 6.0 and 6.8, respectively. Conclusion: Lapachol revealed promising anti-TB activity, especially associated with NAC.

Insight about cell wall remodulation triggered by rifampicin in Mycobacterium tuberculosis.

Rifampicin plays an important role during the treatment of tuberculosis, which makes it to be recommended throughout the regimen. The molecular target for rifampicin activity and resistance is the bacterial RNA polymerase coded by rpoB. However, it has been observed that Mycobacterium tuberculosis could use different metabolic pathways contributing to drug activity/resistance. In this sense, Proteomics analysis has been a key aspect towards the understanding of the dynamic genome expression triggered by drugs and other M. tuberculosis hostile stimuli. Herein, we aimed to report the changes in the M. tuberculosis protein profile triggered by rifampicin. The M. tuberculosis H37Rv strain was submitted to 12, 24 and 48 h of rifampicin challenge, at the minimal inhibitory concentration (0.03 µg mL-1), and proteins were extracted. The protein identification was carried out by liquid chromatography coupled to mass spectrometry (LC-MS). Four proteins, Ino1 (Rv0046c), FabD (Rv2243), EsxK (Rv1197) and PPE60 (Rv3478) were statistically underexpressed over 48 h of rifampicin exposure, indicating that in addition to the known activity of rifampin in transcriptional machinery in M. tuberculosis, processes related to disturbance in cell wall synthesis and lipid metabolism in the bacillus are also triggered by rifampicin contributing to bacillus death.

Minimum Bactericidal Concentration Techniques in Mycobacterium tuberculosis: A Systematic Review.

Minimum bactericidal concentration (MBC) assay is an accepted parameter for evaluating new antimicrobial agents, and it is frequently used as a research tool to provide a prediction of bacterial eradication. To the best of our knowledge, there is no standardization among researchers regarding the technique used to detect a drug's MBC in Mycobacterium tuberculosis. Thus, the aim of this systematic review is to discuss the available literature in determining a drug's MBC in M. tuberculosis, to find the most commonly used technique and standardize the process. A broad and rigorous literature search of three electronic databases (PubMed, Web of Knowledge, and LILACS) was performed according to the PRISMA statement. We considered studies that were published from January 1, 1990 to February 19, 2019. Google Scholar was also searched to increase the number of publications. We searched for articles using the MeSH terms "microbiological techniques," "Mycobacterium," "antibacterial agents." In addition, free terms were used in the search. The search yielded 6,674 publications. After filter application, 5,348 publications remained. Of these, we evaluated the full text of 187 publications. By applying the inclusion criteria, 69 studies were included in the present systematic review. In the literature analyzed, a great variety in the techniques used to determine a drug's MBC in M. tuberculosis was observed. The most common variability is related to the culture media used, culture incubation time, and the percentage of bacterial death for the drug to be considered as bactericidal. The most commonly used technique for drug's MBC determination was carried out using the drug's minimum inhibitory concentration (MIC) assay. Aliquots from prior MIC values were subcultured in Middlebrook agar and incubated for 4 weeks at 35°C for determining the colony forming unit (CFU) with relevance to detect 99.9% bacilli killed or reduction in 3 log10 viable bacilli.

Synthesis and anti-Mycobacterium tuberculosis activity of imide-ß-carboline and carbomethoxy-ß-carboline derivatives.

A series of methyl ß-carboline carboxylates (2a-g) and of imide-ß-carboline derivatives containing the phthalimide (4a-g), maleimide (5b, g) and succinimide (6b, e, g) moiety were synthesized, and evaluated for their activity against Mycobacterium tuberculosis H37Rv. The most active ß-carboline derivatives against the reference strain were assayed for their cytotoxicity and the activity against resistant M. tuberculosis clinical isolates. Farther, structure-activity relationship (SAR) studies were carried out using the three and four-dimensional approaches for starting to understand the way of ß-carboline activity in M. tuberculosis. All 19 ß-carboline derivatives were assayed, firstly, by determining the minimum inhibitory concentration (MIC) using resazurin microtiter assay plate (REMA) in M. tuberculosis H37Rv. Then, five derivatives (2c, 4a, 4e, 4g, 6g), which showed MIC ≤ 125 µg/mL, were assayed in nine resistant M. tuberculosis clinical isolates (five MDR, three isoniazid monoresistant and one isoniazid plus streptomycin resistant). The MIC values against the resistant clinical isolates ranged from 31.25 to >250 µg/mL. All five derivatives were non-cytotoxic to the VERO cell line, determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, at the tested concentration (selectivity index ranged from <1.74 to 14.4). Our study demonstrated that (2c) and (6g) derivatives had better anti-M. tuberculosis activity, especially against resistant clinical isolates, what makes them scaffold candidates for further investigations about their anti-tuberculosis activity. The SAR study conducted with the 19 ß-carboline derivatives showed the importance of steric effects for the synthesized ß-carbolines against M tuberculosis, and these models can be used for future proposition of new derivatives, increasing the chances of obtaining potentially anti-tuberculosis compounds.

Occurrence of Mycoplasmaspp. and Ureaplasmaspp. in genital specimens

Mycoplasmaspp. and Ureaplasmaspp. belong tohumans'genitourinary microbiota and sometimesare associated with infections of the genitourinarytract. The aim of this study was to evaluate the occurrence of Mycoplasmaspp. and Ureaplasmaspp. in genital specimens from patients of the 15thRegional de Saúde of ParanáState, Brazil, and to correlate the results with clinical and laboratory data.A retrospective cross-sectional study was conducted,based on the analysis of results of vaginal, endocervical, urine andurethral culture for mycoplasmas from patients attended in areference laboratory, from January 2009 to December 2016. We evaluated 2,475 results of culture for mycoplasmas. A total of 50.8% patients were positive for mycoplasmas. Of these, 76.8%had positive culture exclusively for Ureaplasmaspp. and 4.7% for Mycoplasmahominis. Both microorganisms were isolated in the microbiology culture of 18.5% of patients. Among the positive culture, 81.4% had significant concentrations.Bacterialvaginosis was the most common alteration observed in association with mycoplasmas.Thehigh positivity of cultures for mycoplasmas, especially Ureaplasmaspp. found in our study, highlightthe presence of these microorganisms in many of the genital tract disorders that can be sexually transmitted and, consequently, should not be neglected.

Is the efflux pump inhibitor Verapamil a potential booster for isoniazid against Mycobacterium tuberculosis?

The membrane-based efflux pump systems are recognized to have an important role in pathogenicity and drug resistance in Mycobacterium tuberculosis by the extrusion of toxic substrates and drugs from the inner bacillus. This study aimed to investigate the in vitro interaction of Verapamil (VP), an efflux pump inhibitor, with the classical first-line anti-tuberculosis drug isoniazid (INH) in resistant and susceptible M. tuberculosis clinical isolates. Seven multidrug-resistant (MDR), three INH monoresistant and four susceptible M. tuberculosis clinical isolates were tested for the INH and VP combination by modified Resazurin Microtiter Assay Plate (REMA). Fractional Inhibitory Concentration (FIC) and Modulation Factor (MF) were determined. The INH plus VP combination showed no significant change in the Minimum inhibitory concentration (MIC) values of INH (FIC≥ 0.5; MF=1 or 2).The use of VP in tuberculosis therapy should be managed carefully, considering the resistance caused by specific mutation in katG and inhA genes, in which the use of these EPIs may have no success. The use of EPIs as an adjunctive drug in the anti-tuberculosis therapy should be further investigated on a larger number of M. tuberculosis clinical isolates with different resistant profile.

Possible Binding of Piperine in Mycobacterium tuberculosis RNA Polymerase and Rifampin Synergism.

The activity of rifampin (RIF) and piperine was evaluated at the relative transcript levels of 12 efflux pumps (EPs), and an additional mechanism was proposed to be behind the synergic interactions of piperine plus RIF in Mycobacterium tuberculosis AutoDock v4.2.3 and Molegro v6 programs were used to evaluate PIP binding in M. tuberculosis RNA polymerase (RNAP). A hypothesis has been raised that piperine interferes in M. tuberculosis growth through RNAP inhibition, differently from what was previously endorsed for EP inhibition only.

Ginger essential oil and fractions against Mycobacterium spp.

ETHNOPHARMACOLOGICAL RELEVANCE: Zingiber officinale (ginger) is a perennial herbaceous plant native in tropical Asia and generally cultivated in most American tropical countries with widespread use in popular medicine. Ginger essential oil (GEO) has been reported to exhibit several biological activities, such as antimicrobial. AIMS OF THE STUDY: The aim of this study was to determine the composition and the property of GEO and related fractions against Mtb and NTM, as well as their cytotoxicity. METHODS AND MATERIALS: GEO was obtained by hydrodistillation and fractionation was performed. Chemical characterization of GEO and fractions were carried out by gas chromatography/mass spectrometry. The antimycobacterial activity was evaluated by resazurin microtiter assay plate and broth microdilution method for Mtb and NTM, respectively. The cytotoxicity in Vero cells was assessed by MTT colorimetric assay. RESULTS: The analyses showed 63 compounds in the GEO sample, characterized by a high number of monoterpenes and sesquiterpenes. GEO fractionation rendered 11 fractions (FR1 to FR11). GEO and fractions minimum inhibitory concentration ranged from 31.25 to >250 µg/mL against Mtb and from 15.6 to >250 µg/mL against NTM. GEO showed better activity against NTM, M. chelonae, and M. abscessus sub. massiliense, than the semi-pure fractions. One fraction (FR5), containing γ-eudesmol as the main compound, was the most active against Mtb and NTM. The GEO and semi-pure fractions cytotoxicity assay showed CC50 63.3 µg/mL, and 36.3-312.5 µg/mL, respectively. CONCLUSIONS: In general, GEO showed a mix of monoterpenes and sesquiterpenes and a better antimycobacterial activity than the semi-pure fractions. Cytotoxic effects of GEO and its fractions should be better investigated.

Anti-Mycobacterium tuberculosis activity of essential oil and 6,7-dehydroroyleanone isolated from leaves of Tetradenia riparia (Hochst.) Codd (Lamiaceae).

BACKGROUND: The global resurgence of tuberculosis (TB) and the development of drug resistance, as multidrug-resistant (MDR) and extensively drug-resistant (XDR) Mycobacterium tuberculosis isolates, are a threat to TB control and have created a need for new and more effective anti-TB drugs. AIM: The current study evaluated the in vitro cytotoxicity and activity of Tetradenia riparia essential oil (TrEO) and 6,7-dehydroroyleanone pure compound against M. tuberculosis H37Rv and susceptible and resistant clinical isolates. METHODS: The in vitro activities of TrEO and 6,7-dehydroroyleanone were determined by Resazurin Microtiter Assay Plate (REMA). The cytotoxicity was evaluated in murine peritoneal macrophages by Alamar Blue assay. The cytotoxic effects were expressed as median concentration cytotoxicity (CC50) and the selectivity index (SI) was calculated. RESULTS: TrEO and 6,7-dehydroroyleanone showed activity against M. tuberculosis H37Rv with minimum inhibitory concentration (MIC) 62.5 µg/ml and 31.2 µg/ml, respectively. Both of them exhibited activities against resistant and susceptible M. tuberculosis clinical isolates with MIC values between 31.2 and 62.5 µg/ml. Cytotoxicity assays showed SI 1.9 and 7.9 for TrEO and 6,7-dehydroroyleanone, respectively. CONCLUSION: These results revealed that TrEO isolated from leaves of T. riparia and the pure compound 6,7-dehydroroyleanone display good activity against M. tuberculosis clinical isolates, including MDR isolates, with low cytotoxicity to murine macrophages. The 6,7-dehydroroyleanone compound is a potential candidate for anti-TB drug.

Combinatory activity of linezolid and levofloxacin with antituberculosis drugs in Mycobacterium tuberculosis.

SETTING: The increase of multidrug and extensively drug resistant Mycobacterium tuberculosis strains turns the search for new tuberculosis (TB) treatment options of paramount importance. OBJECTIVE: In this sense, the present study evaluates the in vitro activity of isoniazid (INH)/rifampicin (RIF)/levofloxacin (LVX) and INH/RIF/linezolid (LNZ) combinations in resistant M. tuberculosis. DESIGN: The activities of the combinations were evaluated with M. tuberculosis H37Rv, susceptible and 10 resistant clinical isolates by three-dimensional checkerboard. LVX and LNZ were used as the third drug at fixed ½ and » minimum inhibitory concentration (MIC). INH and RIF were tested at concentrations ranging from 0.0009 µg/mL to 50 µg/mL and 0.0009 µg/mL to 800 µg/mL, respectively. The combinatorial effects were determined by the Fractional Inhibitory Concentration Index (FICI). FICI values ≤ 0.75, 0.75-4 and ≥4 were considered as synergism, indifferent and antagonism, respectively. RESULTS: MIC ranged from 0.03 - 6.25 µg/mL for INH, 0.008-100 µg/mL for RIF, 0.12-0.25 µg/mL for LVX and 0.25-0.5 µg/mL for LNZ in the H37Rv and all clinical isolates. INH/RIF/LVX and INH/RIF/LNZ synergisms were observed in 40 and 50% of the resistant M. tuberculosis clinical isolates and better observed for INH and RIF combined to LVX or LNZ at » MIC. CONCLUSION: The present study calls attention for the potential use of INH/RIF/LVX and INH/RIF/LNZ combinations in the treatment of resistant TB.

RDRioMycobacterium tuberculosis lineage in the Brazil/Paraguay/Argentina triple border.

The high tuberculosis (TB) incidence rates, the closeness of the cities and the high migration flux on the Brazil/Paraguay/Argentina border deserves an in-depth study, using Mycobacterial Interspersed Repetitive Unit (MIRU) and Spoligotyping genetic markers to explore the impact of the Mycobacterium tuberculosis RDRio lineage on disease transmission and resistance to anti-TB drugs in this setting. Although without the totality of M. tuberculosis isolates causing TB in this studied setting, a number of 97 isolates obtained from sputa samples culture of patients with confirmed TB, from 2013 to 2015, were submitted to 24 loci MIRU, Spoligotyping, detection of RDRio lineage and detection of mutation related to isoniazid and rifampicin resistance by MTBDRplus/DNA STRIP. In this sample, it was observed high clonal variability of circulating M. tuberculosis isolates causing TB in Brazilian cities bordering Paraguay and Argentina. The percentage of RDRio lineage causing TB in this setting was 15.46%, and lower than the detected in different areas of Brazil. According to 24 loci MIRU, the major MIRU International Type (MIT) related with RDRio lineage were MIT 26, MIT 738, MIT 601 with four, two and one isolates, respectively. Eight isolates with RDRio marker were classified as orphans. The mainly Spoligofamily related with RDRio lineage was LAM1 and LAM9 and no relationship between RDRio lineage and resistance in M. tuberculosis isolates circulating in this setting could be established. This work is pioneer in studying the dynamics of RDRio lineage transmission on the Brazil/Paraguay/Argentina border and deserves further studies to analyze the real contribution of the RDRio lineage in outbreaks and the risk of significant development of MDR-TB in the setting studied.

Intramacrophage Mycobacterium tuberculosis efflux pump gene regulation after rifampicin and verapamil exposure.

Objectives: Since resistance of Mycobacterium tuberculosis (Mtb) partially derives from efflux pumps (EPs) in the plasma membrane, the current study evaluates EPs in Mtb exposed to rifampicin in the presence of the EP inhibitor verapamil, within a macrophage environment. Methods: Human acute monocytic leukaemia cell line THP-1 was infected with Mtb H37Rv and exposed to rifampicin and verapamil alone and in combination for 24 and 72 h. After RNA extraction, quantitative PCR was carried out for 11 EP genes using SYBR green PCR master mix in the StepOne™ Real-Time PCR System. Results: After 24 h of exposure to rifampicin, Mtb H37Rv showed that 10 EP genes were up-regulated when compared with the control. The rifampicin/verapamil combination induced down-regulation of 54.5% (6/11) of the EP genes. At 72 h, rifampicin exposure induced up-regulation of 10 EP genes and rifampicin/verapamil induced down-regulation of 8 EP genes, which suggests effective EP-inhibitory activity of verapamil against Mtb H37Rv in an intramacrophage environment. Conclusions: The current study demonstrated that rifampicin/verapamil caused down-regulation of several EP genes in Mtb inside the macrophage environment. In vivo trials may show that rifampicin/verapamil therapy could be of value in enhancing anti-TB treatment.

Fast detection of Mycobacterium tuberculosis in culture-positive sputum samples by nitrate reductase activity

ABSTRACT Microscopy and bacterial culture are the main tools in the diagnosis of tuberculosis. Since the slow growth of Mycobacterium tuberculosis impairs rapid diagnosis strategies, especially in countries where the latter are the only available resources, the ongoing development of new and inexpensive tools based on mycobacterial metabolism optimizing growth detection with preliminary identification is greatly welcome. When compared to the other species from the M. tuberculosis complex, M. tuberculosis is a strong nitrate reducer. Current assay compares the nitrate reductase activity of M. tuberculosis from pulmonary specimens cultivated in nitrate-supplemented media. Fifty-five sputum samples were decontaminated and inoculated in conventional (Middlebrook 7H9, Ogawa Kudoh-OK) and in nitrate-supplemented media (Middlebrook 7H9-N, Ogawa Kudoh-N). An aliquot from the media directly reacted with Griess reagent (7H9-N and OK-N) every five days, or transferred to a nitrate substrate solution (7H9, OK). Nitrate to nitrite reduction was considered positive, revealed by the pink color, indicating bacterial growth. As reference method, the Mycobacteria Growth Indicator Tube (MGIT) was used for sensitivity calculations and statistical analysis. 7H9-N and OK-N assays proved to perform better in detecting M. tuberculosis than conventional assays (7H9 and OK). Indeed, broth nitrate-supplemented medium (7H9-N) was comparable to MGIT to detect M. tuberculosis, except in growth detection time. Results show that 7H9-N may be used as an alternative tool particularly in low-income countries since it is a simple and cheap technique, and does not restrict diagnosis to single-source products.