L-Alanine specifically potentiates fluoroquinolone efficacy against Mycobacterium persisters via increased intracellular reactive oxygen species.

Tuberculosis caused by Mycobacterium tuberculosis remains a major global health concern; M. tuberculosis drug resistance and persistence further fueled the situation. Nutrient supportive therapy was intensively pursued to complement the conventional treatment, as well as their synergy with current antibiotics. To explore whether L-alanine can synergize with fluoroquinolones against M. tuberculosis, M. smegmatis was used as a surrogate in this study. We found that L-alanine can boost the bactericidal efficacy of fluoroquinolones, increasing the production of intracellular reactive oxygen species. This effect is very significant for persisters. Accelerated tricarboxylic acid cycle and/or nucleotide metabolism were observed after the addition of L-alanine. M. smegmatis MSMEG2660 is a homolog of the alanine dehydrogenase (Rv2780, MSMEG2659) negative regulator Rv2779c and involved in the L-alanine potentiation of fluoroquinolone via funneling more alanine into tricarboxylic acid. Deletion mutant of the MSMEG2660 (∆Ms2660) became more susceptible, and more readily revived from persistence. We firstly found that L-alanine can synergize with fluoroquinolones against Mycobacterium, especially the persisters via promoting metabolism. This will inspire new avenue to eliminate Mycobacterium persisters.

A rare case of an HIV-seronegative AIDS patient with Pneumocystis jirovecii pneumonia.

BACKGROUND: As technology progresses, several highly sensitive human immunodeficiency virus (HIV) screening kits are being researched and developed to quickly and efficiently identify serum HIV antibodies within the non-window period. In individuals who are HIV-seronegative, HIV infections that are not within a window period are rare. In such cases, all antibody detection methods will fail, and misdiagnosing these patients will have catastrophic consequences. CASE PRESENTATION: A 22-year-old male Chinese patient with diffuse exudative lesions in both lungs and initial symptoms of cough and dyspnoea was diagnosed with Pneumocystis jirovecii pneumonia (PJP) by aetiological examination, and the patient's plasma CD4+ T-cell count was extremely low. In China, PJP is prevalent in HIV-infected individuals. Pneumocystis jirovecii (P. jirovecii) has a high colonisation rate in patients with HIV infections. This patient was naturally suspected of being an HIV patient; however, serum HIV antibody tests were negative using both an enzyme-linked immunosorbent assay (ELISA) and a latex agglutination assay, and HIV was not detected by western blotting. Subsequently, the plasma HIV viral load was found to be extremely high on two repeated plasma HIV RNA tests, thus confirming HIV-seronegative acquired immunodeficiency syndrome (AIDS) in this patient. With administration of effective anti-P. jirovecii treatment and highly active antiretroviral therapy (HAART) after diagnosis, the patient's disease condition was rapidly controlled. CONCLUSION: This is the second reported case in China of an HIV-seronegative AIDS patient. Such cases are also rare worldwide. Although HIV-seronegative HIV infections are rare, AIDS should be considered in immunodeficient patients with opportunistic infections, even if the test results are HIV-seronegative. Plasma HIV RNA testing is important for such patients.

l-Serine potentiates fluoroquinolone activity against Escherichia coli by enhancing endogenous reactive oxygen species production.

BACKGROUND: The increase in multiple antimicrobial-resistant bacteria seriously threatens global public health. Novel effective strategies are urgently needed. l-Serine was reported as the most effective amino acid inhibitor against bacterial growth and can sensitize Escherichia coli cells to gentamicin. It is currently unknown whether l-serine affects other type of antibiotics such as ß-lactams and fluoroquinolones. METHODS: Using E. coli, we studied the combination of l-serine with diverse antibiotics against laboratory and clinical E. coli cultures and persisters. The intracellular NAD(+)/NADH level and ROS were determined using kits. Total cellular iron was determined by using a colorimetric ferrozine-based assay. RESULTS: Exogenous l-serine sensitized E. coli ATCC 25922 and clinically isolated fluoroquinolone-resistant E. coli to fluoroquinolones. This potentiation is independent of growth phase. Addition of serine increases the production of NADH. The underlying mechanism of this strategy is that the combination of serine with ofloxacin or moxifloxacin increases the NAD(+)/NADH ratio, disrupts the Fe-S clusters and increases the production of endogenous reactive oxygen species. Furthermore, we used a serine and ofloxacin or moxifloxacin combination in vitro to combat bacterial persister cells, compared with antibiotic treatment alone; combinational treatments of persister cells with antibiotics and l-serine resulted in a significantly greater decrease in cell viability. CONCLUSIONS: To our knowledge, this is the first report that l-serine can potentiate the action of ofloxacin or moxifloxacin against Gram-negative bacteria and could constitute a new strategy for the eradication of bacterial infections.

Mycobacteriophage putative GTPase-activating protein can potentiate antibiotics.

The soaring incidences of infection by antimicrobial resistant (AR) pathogens and shortage of effective antibiotics with new mechanisms of action have renewed interest in phage therapy. This scenario is exemplified by resistant tuberculosis (TB), caused by resistant Mycobacterium tuberculosis. Mycobacteriophage SWU1 A321_gp67 encodes a putative GTPase-activating protein. Mycobacterium smegmatis with gp67 overexpression showed changed colony formation and biofilm morphology and supports the efficacy of streptomycin and capreomycin against Mycobacterium. gp67 down-regulated the transcription of genes involved in cell wall and biofilm development. To our knowledge, this is the first report to show that phage protein in addition to lysin or recombination components can synergize with existing antibiotics. Phage components might represent a promising new clue for better antibiotic potentiators.

Regulatory effect of AMP-activated protein kinase on pulmonary hypertension induced by chronic hypoxia in rats: in vivo and in vitro studies.

Activation of AMP-activated protein kinase (AMPK) plays an important role in cardiovascular protection. It can inhibit arterial smooth muscle cell proliferation and cardiac fibroblast collagen synthesis induced by anoxia. However, the role of AMPK-dependent signalling cascades in the pulmonary vascular system is currently unknown. This study aims to determine the effects of AMPK on pulmonary hypertension and pulmonary vessel remodelling induced by hypoxia in rats using in vivo and in vitro studies. In vivo study: pulmonary hypertension, right ventricular hypertrophy and pulmonary vascular remodelling were found in hypoxic rats. Meanwhile, AMPKα1 and phosphorylated AMPKα1 were increased markedly in pulmonary arterioles and lung tissues. Mean pulmonary arterial pressure, index of right ventricular hypertrophy and parameters of pulmonary vascular remodelling, including vessel wall area/total area, density of nuclei in medial smooth muscle cells, and thickness of the medial smooth muscle cell layer were markedly suppressed by AICAR, an AMPK agonist. In vitro study: the expression of AMPKα1 and phosphorylated AMPKα1 was increased in pulmonary artery smooth muscle cells (PASMCs) under hypoxic conditions. The effects of PASMC proliferation stimulated by hypoxia were reinforced by treatment with Compound C, an AMPK inhibitor. AICAR inhibited the proliferation of PASMCs stimulated by hypoxia. These findings suggest that AMPK is involved in the formation of hypoxia-induced pulmonary hypertension and pulmonary vessel remodelling. Up-regulating AMPK can contribute to decreasing pulmonary vessel remodelling and pulmonary hypertension induced by hypoxia.

Mycobacterium tuberculosis PE_PGRS1 promotes mycobacteria intracellular survival via reducing the concentration of intracellular free Ca2+ and suppressing endoplasmic reticulum stress.

Mycobacterium tuberculosis (M. tuberculosis) is the causative agent of tuberculosis (TB). And the PE_PGRS family members of M. tuberculosis are closely associated with virulence and antigen presentation but with function largely elusive. PE_PGRS1(Rv0109) contained 7 Ca2+ binding domains of GGXGXD/NXUX (X is any amino acid), which can reduce intracellular Ca2+ surge. In addition, PE_PGRS1 can mitigate the activation of PERK branch in endoplasmic reticulum (ER) stress by down-regulating the expression of CHOP, Bip, p-PERK, p-eIF2α, and ATF4. Interestingly, we found that two splicing variations of Bax/Bcl-2, Baxß, and Bcl-2α, were differentially expressed after infection with Ms_PE_PGRS1, and may be involved in the regulation of apoptosis. Hence, this study identified that PE_PGRS1 is a novel calcium-associated protein that can decrease intracellular Ca2+ levels and the PERK axis. And the weakening of the PERK-eIF2α-ATF4 axis reduces THP-1 macrophages apoptosis, promotes the survival of mycobacteria in macrophages.

A Dueling-Competent Signal-Sensing Module Guides Precise Delivery of Cargo Proteins into Target Cells by Engineered Pseudomonas aeruginosa.

To recognize and manipulate a specific microbe of a crowded community is a highly challenging task in synthetic biology. Here we introduce a highly selective protein delivery platform, termed DUEC, which responds to direct contact of attacking cells by engineering the tit-for-tat/dueling response of H1-T6SS (type VI secretion system) in Pseudomonas aeruginosa. Using a Cre-recombinase-dependent reporter, we screened H1-T6SS-secreted substrates and developed Tse6N as the most effective secretion tag for Cre delivery. DUEC cells can discriminately deliver the Tse6N-Cre cargo into the cytosol of T6SS+ but not T6SS- Vibrio cholerae cells. DUEC could also deliver a nuclease cargo, Tse6N-NucSe1, to selectively kill provoking cells in a mixed community. These data demonstrate that the DUEC cell not only is a prototypical physical-contact sensor and delivery platform but also may be coupled with recombination-based circuits with the potential for complex tasks in mixed microbial communities.

Toripalimab and anlotinib as a maintenance treatment for extensive-stage small-cell lung cancer: a case report.

Small-cell lung cancer (SCLC) is characterized by rapid proliferation, high growth fraction and early locoregional and distant metastases. SCLC has been found to be significantly sensitive to platinum-etoposide chemotherapy, but most patients relapse within 6 months of completing initial treatment and median overall survival is about 10 months. Despite the current immunotherapy-treatment approach, median survival time and progression-free survival remain short. This case shows the potential efficacy of maintenance therapy with toripalimab and anlotinib after first-line platinum-etoposide chemotherapy in a patient with extensive-stage SCLC. The combination treatment prolonged the progression-free survival to approximately 13 months and overall survival to 25 months; this is well above the existing standard, and this patient did not experience any major adverse effects during the course of therapy.

Treatment failure in a patient infected with Listeria sepsis combined with latent meningitis: A case report.

BACKGROUND: Listeria is a food-borne disease, which is rarely prevalent in the normal population; it mostly occurs in pregnant women, newborns, immunodeficiency patients, and the elderly. The main manifestations of this disease in patients include sepsis, meningitis, etc, and the mortality rate remains high, although the onset of meningitis is relatively insidious. CASE SUMMARY: A 75-year-old man presented with a fever for 1 wk and was admitted to the hospital for diagnosis and management of a lung infection. His condition improved after receiving anti-infective treatment for 2 wk. However, soon after he was discharged from the hospital, he developed fever again, and gradually developed various neurological symptoms, impaired consciousness, and stiff neck. Thereafter, through the cerebrospinal fluid metagenomic testing and blood culture, the patient was diagnosed with Listeria monocytogenes meningitis and sepsis. The patient died after being given active treatment, which included penicillin application and invasive respiratory support. CONCLUSION: This case highlights the ultimate importance of early identification and timely application of the various sensitive antibiotics, such as penicillin, vancomycin, meropenem, etc. Therefore, for high-risk populations with unknown causes of fever, multiple blood cultures, timely cerebrospinal fluid examination, and metagenomic detection technology can assist in confirming the diagnosis quickly, thereby guiding the proper application of antibiotics and improving the prognosis.

Mycobacterium Fluoroquinolone Resistance Protein D (MfpD), a GTPase-Activating Protein of GTPase MfpB, Is Involved in Fluoroquinolones Potency.

Tuberculosis (TB) caused by Mycobacterium tuberculosis infection remains one of the most serious global health problems. Fluoroquinolones (FQs) are an important component of drug regimens against multidrug-resistant tuberculosis, but challenged by the emergence of FQ-resistant strains. Mycobacterium fluoroquinolone resistance protein A (MfpA) is a pentapeptide protein that confers resistance to FQs. MfpA is the fifth gene in the mfp operon among most Mycobacterium, implying other mfp genes might regulate the activity of MfpA. To elucidate the function of this operon, we constructed deletion mutants and rescued strains and found that MfpD is a GTPase-activating protein (GAP) involved in FQs activity. We showed that the recombinant strains overexpressing mfpD became more sensitive to FQs, whereas an mfpD deletion mutant was more resistant to FQs. By using site-directed mutagenesis and mycobacterial protein fragment complementation, we genetically demonstrated that mfpD participated in FQs susceptibility via directly acting on mfpB. We further biochemically demonstrated that MfpD was a GAP capable of stimulating the GTPase activity of MfpB. Our studies suggest that MfpD, a GAP of MfpB, is involved in MfpA-mediated FQs resistance. The function of MfpD adds new insights into the role of the mfp operon in Mycobacterium fluoroquinolone resistance. IMPORTANCE Tuberculosis is one of the leading causes of morbidity and mortality worldwide largely due to increasingly prevalent drug-resistant strains. Fluoroquinolones are important antibiotics used for treating multidrug-resistant tuberculosis (MDR-TB). The resistance mechanism mediated by the Mycobacterium fluoroquinolone resistance protein (MfpA) is unique in Mycobacterium. However, the regulatory mechanism of MfpA remains largely unclear. In this study, we first report that MfpD acts as a GAP for MfpB and characterize a novel pathway that controls Mycobacterium small G proteins. Our findings provide new insights into the regulation of MfpA and inspiration for new candidate targets for the discovery and development of anti-TB drugs.

Delivery of an Rhs-family nuclease effector reveals direct penetration of the gram-positive cell envelope by a type VI secretion system in Acidovorax citrulli.

The type VI secretion system (T6SS) is a double-tubular nanomachine widely found in gram-negative bacteria. Its spear-like Hcp tube is capable of penetrating a neighboring cell for cytosol-to-cytosol protein delivery. However, gram-positive bacteria have been considered impenetrable to such T6SS action. Here we report that the T6SS of a plant pathogen, Acidovorax citrulli (AC), could deliver an Rhs-family nuclease effector RhsB to kill not only gram-negative but also gram-positive bacteria. Using bioinformatic, biochemical, and genetic assays, we systematically identified T6SS-secreted effectors and determined that RhsB is a crucial antibacterial effector. RhsB contains an N-terminal PAAR domain, a middle Rhs domain, and an unknown C-terminal domain. RhsB is subject to self-cleavage at both its N- and C-terminal domains and its secretion requires the upstream-encoded chaperone EagT2 and VgrG3. The toxic C-terminus of RhsB exhibits DNase activities and such toxicity is neutralized by either of the two downstream immunity proteins, RimB1 and RimB2. Deletion of rhsB significantly impairs the ability of killing Bacillus subtilis while ectopic expression of immunity proteins RimB1 or RimB2 confers protection. We demonstrate that the AC T6SS not only can effectively outcompete Escherichia coli and B. subtilis in planta but also is highly potent in killing other bacterial and fungal species. Collectively, these findings highlight the greatly expanded capabilities of T6SS in modulating microbiome compositions in complex environments.

LncRNA-LINC01089 inhibits lung adenocarcinoma cell proliferation and promotes apoptosis via sponging miR-543.

LINC01089, a newly discovered long non-coding RNA (lncRNA), has been reported to inhibit the progression of various types of cancers. This study aimed to characterize LINC01089 in the pathogenesis of lung adenocarcinoma (LUAD). LINC01089 expression in LUAD tissues or/and cells and its association with the overall survival of LUAD patients was analyzed in The Cancer Genome Atlas (TCGA)-LUAD database, by qRT-PCR or by Kaplan-Meier's curve. Databases of StarBase, LncBase, and DEmiRNA were used to predict and confirm the interaction between LINC01089 and potential LINC01089-targeted microRNAs (miRNAs). The expressions of these miRNAs in LUAD tissues or/and cells were determined by qRT-PCR, and dual-luciferase reporter assay was performed to validate lncRNA-miRNA interaction. The expressions of B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax) and Cleaved caspase-3 in LUAD cells were analyzed by Western blot. LINC01089 improved overall survival of LUAD patients and was low-expressed in LUAD. Upregulating LINC01089 expression reduced LUAD cell viability, inhibited colony formation, enhanced apoptosis, accompanied by downregulated Bcl-2 and miR-543 and upregulated Bax and Cleaved caspase-3. MiR-543 was determined as a target gene of LINC01089, and was high-expressed in LUAD tissues. Upregulating miR-543 expression induced the opposite effects to LINC01089 upregulation on these cellular biological behaviors and the expressions of Bcl-2, Bax and Cleaved caspase-3. Moreover, the effects of miR-543 upregulation and LINC01089 upregulation were mutually counteracted by each other. LINC01089 inhibited lung adenocarcinoma cell proliferation and promoted apoptosis via sponging miR-543.

Choriocarcinoma Masquerading as Lung Abscess or Lung Cancer: A Case with Atypical Imaging Findings.

BACKGROUND: Choriocarcinoma is a highly malignant trophoblastic tumor. However, the awareness surrounding its atypical clinical presentation is insufficient. The presence of a solitary lung lesion without uterine lesions often leads to misdiagnosis or missed diagnosis, which in turn causes delayed treatment or even multiple metastases throughout the body. CASE PRESENTATION: We present the case of a 36-year-old female patient who was misdiagnosed with a lung abscess and received suboptimal anti-infective treatment. She then underwent left upper lobectomy and was misdiagnosed with lung cancer by abscess incision and drainage in thoracic surgery, however, the results after pleural effusion removal were suboptimal. During this time a breast nodule was found, and a large segment of the right breast was excised and misdiagnosed as breast cancer but was finally diagnosed as choriocarcinoma with multiple metastases of lung and breast. Multiple metastases were also detected in the head, liver, kidney, and bones. The patient underwent multiple adjuvant chemotherapies. The blood ß-hCG level gradually declined to normal. When we reported this case, that is, seven months after the diagnosis, the patient was still alive, and the disease was stable without progress. CONCLUSION: Choriocarcinoma with a solitary lung lesion as the first presentation and no lesions in the uterus is clinically rare. This may lead to a delay in diagnosis due to poor awareness of the disease and the appearance of multiple metastases throughout the body. Clinicians should be more aware of choriocarcinoma with an atypical presentation to reduce misdiagnosis and missed diagnosis.

Mycobacterium Lrp/AsnC family transcriptional factor modulates the arginase pathway as both a sensor and a transcriptional repressor.

L-Arginine is the precursor of nitric oxide (NO), a host immune effector against intracellular pathogens including Mycobacterium tuberculosis (M. tb). Pathogens including M. tb have evolved various strategies targeting arginine to block the production of NO for better survival and proliferation. However, L-arginine metabolism and regulation in Mycobacterium are poorly understood. Here, we report the identification of M. smegmatis MSMEG_1415 (homolog of M. tb Rv2324) as an arginine-responsive transcriptional factor regulating the arginase pathway. In the absence of L-arginine, MSMEG_1415 acts as a repressor to inhibit the transcription of the roc (for arginine, ornithine catabolism) gene cluster, thereby switching off the arginase pathway. Treatment with L-arginine relieves the transcriptional inhibition of MSMEG_1415 on the roc gene cluster to activate the arginase pathway. Moreover, the L-arginine-MSMEG_1415 complex activates the transcription of the roc gene cluster by recognizing and binding a 15-bp palindrome motif, thereby preventing the excess accumulation of L-arginine in M. smegmatis. Physiologically, MSMEG_1415 confers mycobacteria resistance to starvation and fluoroquinolones exposure, suggestive of its important role in M. smegmatis persistence. The results uncover a unique regulatory mechanism of arginine metabolism in mycobacteria and identify M. tb Rv2324 as an attractive candidate target for the design of drugs against tuberculosis.

Response to Afatinib in a Patient with NSCLC Harboring Novel EGFR Exon 20 Insertion Mutations.

PURPOSE: Most epidermal growth factor receptor (EGFR) exon 20 insertion (ex20ins) mutations are resistant to tyrosine kinase inhibitors (TKIs). While some non-small cell lung cancer (NSCLC) patients harboring special subtypes of EGFR ex20ins still achieved clinical response after TKIs treatment, identifying special subtypes of EGFR ex20ins is helpful to find out NSCLC patients who can respond to TKIs. CASE PRESENTATION: A 71-year-old non-smoker Chinese female was diagnosed with advanced lung adenocarcinoma harboring EGFR ex20ins (N771delinsKG). The patient received first-line afatinib (40 mg/day) therapy and a significant and substantial reduction in tumor size was observed subsequently. According to RESIST 1.1, a radiological partial response was achieved. The final progression-free survival was 10 months. CONCLUSION: This is the first published case report of EGFR N771delinsKG lung adenocarcinoma, which highlighted the heterogeneity of clinical response to TKIs for EGFR ex20ins-mutant NSCLC. Such results need to be further investigated in prospective studies.

Mycobacterium tuberculosis Rv0341 Promotes Mycobacterium Survival in In Vitro Hostile Environments and within Macrophages and Induces Cytokines Expression.

Mycobacterium tuberculosis represents an ancient deadly human pathogen that can survive and multiply within macrophages. The effectors are key players for the successful pathogenesis of this bacterium. M. tuberculosis open reading frame (ORF) Rv0341, a pathogenic mycobacteria-specific gene, was found to be upregulated in macrophages isolated from human tuberculosis granuloma and inside the macrophages during in vitro infection by M. tuberculosis. To understand the exact role of this gene, we expressed the Rv0341 gene in M. smegmatis, which is a non-pathogenic Mycobacterium. We found that Rv0341 expression can alter colony morphology, reduce the sliding capability, and decrease the cell wall permeability of M. smegmatis. Furthermore, Rv0341 remarkably enhanced M. smegmatis survival within macrophages and under multiple in vitro stress conditions when compared with the control strain. Ms_Rv0341 significantly induced expression of TNF-α, IL-1ß, and IL-10 compared with M. smegmatis harboring an empty vector. In summary, these data suggest that Rv0341 is one of the M. tuberculosis virulence determinants that can promote bacilli survival in harsh conditions and inside macrophages.

Mycobacterium tuberculosis Rv0426c promotes recombinant mycobacteria intracellular survival via manipulating host inflammatory cytokines and suppressing cell apoptosis.

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb) is still a leading cause of death worldwide. M. tuberculosis has evolved multipronged strategies to subvert host immune defenses and establish an immunologically privileged niche in macrophages. Rv0426c has been predicted to be an effector involved in the Mtb-host interactions. To investigate the potential role played by Rv0426c, we constructed recombinant M. smegmatis strains with heterologous expression of Rv0426c. We observed that Rv0426c recombinants became more susceptible to various stresses by increasing cell wall permeability, however with elevated early survival rate within macrophages. This was accompanied by decreased levels of pro-inflammatory cytokines and host cell apoptosis. The data suggested that Rv0426c was a new player involved in the interactions between Mtb and macrophages.

Mce-associated protein Rv0177 alters the cell wall structure of Mycobacterium smegmatis and promotes macrophage apoptosis via regulating the cytokines.

The success of Mycobacterium tuberculosis as a pathogen largely contributes to its ability to infect, modify and persist within the host cells. M. tuberculosis Rv0177 is a gene of the mce1 operon (Mammalian cell entry), encoding a conserved hypothetical protein, essential for M. tuberculosis survival and up-regulated within murine macrophages. To explore its function, Rv0177 was heterologously expressed in M. smegmatis. The recombinant protein was located in the cell wall. M. smegmatis recombinant strain expressing Rv0177 altered sliding motility, its cell wall architecture and the permeability. Moreover, M. smegmatis expressing Rv0177 could up-regulate MCP-1 and downregulate the IL-6 expression in RAW264.7 macrophages in comparison to the control. MS_Rv0177 increased the expression of MCP-1 inducible protein (MCPIP) and a C/EBP homologous protein (CHOP) owing to MCP-1. In addition, the JNK signaling pathway was engaged in the interplay between MS_Rv0177 and macrophages. The macrophage caspase-3 activation and cell apoptosis were induced by the recombinant. This provided novel functional cues for the MCE-associated Rv0177.

Mycobacterium tuberculosis metC (Rv3340) derived hydrogen sulphide conferring bacteria stress survival.

Tuberculosis, especially multidrug resistant cases, remains an enormous public health threat. Mycobacterium tuberculosis metC (Rv3340) an enzyme involved in methionine biosynthesis was identified and characterised for antimicrobial susceptibility. We reported that the overexpression of Rv3340 in Mycobacterium smegmatis (Ms_Rv3340) produces hydrogen sulphide (H2S) for its energy in harsh conditions. The produced H2S sustained Ms_Rv3340 against streptomycin, whereas the chemical inhibition of H2S caused streptomycin lethality to Ms_Rv3340. Further analysis showed that cysteine-H2O2 treatment of Ms-Rv3340 initiated DNA damage via Fenton reaction. Ms_Rv3340 downregulated the expression levels of three streptomycin responsive genes. To our knowledge, no study has been previously reported that M. tuberculosis metC (Rv3340) can generates H2S modulating resistant to streptomycin which provides a greater perception toward the treatment and control of tuberculosis.

The Synergistic Effect of Exogenous Glutamine and Rifampicin Against Mycobacterium Persisters.

Persisters, stochastic dormant variants of normal bacteria cell, represent a significant portion of the survivors upon exposure to antibiotics and other environmental stresses, which contributes substantially to high level antibiotics tolerance. Glutamine is a crucial component of the Mycobacteria nitrogen pool that is indispensable for survival upon stresses. To study whether a synergistic effect exists between glutamine and antibiotics against Mycobacterial persisters, the efficacy of rifampicin alone or together with exogenous glutamine upon Mycobacterium smegmatis mc2 155 persisters was monitored. The result showed that glutamine decreases M. smegmatis tolerance to rifampicin upon starvation. The reactive oxygen species level of the strains treated with rifampicin and glutamine increased. The synergism of glutamine and rifampicin to kill persisters might derive from altering the oxidative phosphorylation and TCA cycle, as both evidenced by both ATP level increase and transcriptome change. Glutamine might represent a synergistic agent of rifampicin to kill Mycobacteria persisters.