Tuberculosis (TB) is responsible for nearly 1.4 million deaths globally every year and continues to remain a serious threat to human health. The problem is further complicated by the growing ...incidence of multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB), emphasizing the need for the development of new drugs against this disease. Phagosomal maturation arrest is an important strategy employed by Mycobacterium tuberculosis to evade the host immune system. Secretory acid phosphatase (SapM) of M.tuberculosis is known to dephosphorylate phosphotidylinositol 3-phosphate (PI3P) present on phagosomes. However, there have been divergent reports on the involvement of SapM in phagosomal maturation arrest in mycobacteria. This study was aimed at reascertaining the involvement of SapM in phagosomal maturation arrest in M.tuberculosis. Further, for the first time, we have also studied whether SapM is essential for the pathogenesis of M.tuberculosis. By deleting the sapM gene of M.tuberculosis, we demonstrate that MtbΔsapM is defective in the arrest of phagosomal maturation as well as for growth in human THP-1 macrophages. We further show that MtbΔsapM is severely attenuated for growth in the lungs and spleen of guinea pigs and has a significantly reduced ability to cause pathological damage in the host when compared with the parental strain. Also, the guinea pigs infected with MtbΔsapM exhibited a significantly enhanced survival when compared with M.tuberculosis infected animals. The importance of SapM in phagosomal maturation arrest as well as in the pathogenesis of M.tuberculosis establishes it as an attractive target for the development of new therapeutic molecules against tuberculosis.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Background. Low iron availability in the host upregulates the mbt gene cluster of Mycobacterium tuberculosis, which is responsible for mycobactin biosynthesis. However, the biological significance of ...mycobactins in the growth of this pathogen and in disease progression has not been elucidated. Methods. We have disrupted the mbtE gene (Rv2380c) in the mbt cluster to evaluate the importance of mycobactin biosynthesis in the growth and virulence of M. tuberculosis. Results. The mbtE mutant (MtbAmbtE) was unable to synthesize mycobactins, displayed an altered colony morphology, and was attenuated for growth in broth culture and in macrophages. Transmission electron microscopy revealed that MtbAmbtE displayed an altered cell wall permeability. The growth characteristics and colony morphology of MtbAmbtE were similar to wild type when the medium was supplemented with mycobactins or when MtbAmbtE was genetically complemented with the mbtE gene. Moreover, guinea pigs infected with MtbAmbtE exhibited a significantly reduced bacillary load and histopathological damage in the organs, in comparison to M. tuberculosis-infected animals. Conclusions. This study highlights the importance of mycobactins in the growth and virulence of M. tuberculosis and establishes the enzymes of mycobactin biosynthesis as novel targets for the development of therapeutic interventions against tuberculosis.
During the establishment of an infection, bacterial pathogens encounter oxidative stress resulting in the production of DNA lesions. Majority of these lesions are repaired by base excision repair ...(BER) pathway. Amongst these, abasic sites are the most frequent lesions in DNA. Class II apurinic/apyrimidinic (AP) endonucleases play a major role in BER of damaged DNA comprising of abasic sites. Mycobacterium tuberculosis, a deadly pathogen, resides in the human macrophages and is continually subjected to oxidative assaults. We have characterized for the first time two AP endonucleases namely Endonuclease IV (End) and Exonuclease III (XthA) that perform distinct functions in M.tuberculosis. We demonstrate that M.tuberculosis End is a typical AP endonuclease while XthA is predominantly a 3'→5' exonuclease. The AP endonuclease activity of End and XthA was stimulated by Mg(2+) and Ca(2+) and displayed a preferential recognition for abasic site paired opposite to a cytosine residue in DNA. Moreover, End exhibited metal ion independent 3'→5' exonuclease activity while in the case of XthA this activity was metal ion dependent. We demonstrate that End is not only a more efficient AP endonuclease than XthA but it also represents the major AP endonuclease activity in M.tuberculosis and plays a crucial role in defense against oxidative stress.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We have deposited polycrystalline Re-doped (Fe65Co35)(100−x)Rex (0≤x≤12.6 at. %) thin films grown under identical conditions and sandwiched between thin layers of Ru in order to study the phenomenon ...of spin pumping as a function of Re concentration. In-plane and out-of-plane ferromagnetic resonance spectroscopy results show an enhancement of the Gilbert damping with an increase in Re doping. We find 98% enhancement in the real part of effective spin mixing conductance Re(geff↑↓) with Re doping. Conversely, the Re(geff↑↓) does not change with Re doping in Fe65Co35 thin films which are seeded and capped with Cu layers. The enhancement in Re(geff↑↓) of Re-doped Fe65Co35 thin films sandwiched between thin layers of Ru is linked to the Re doping-induced change of the interface electronic structure in the nonmagnetic Ru layer. The saturation magnetization decreases 35% with increasing Re doping up to 12.6 at. %. This study opens a direction of tuning the spin mixing conductance in magnetic heterostructures by doping of the ferromagnetic layer, which is essential for the realization of energy-efficient operation of spintronic devices.
Health care workers HCW are at a higher risk of infection SARS CoV2 infection due to frequent and close contact to patients with COVID-19.
Serum samples from 500 HCW's were tested for SARS CoV2 IgG ...antibodies in October 2020. A questionnaire was used to collect demographic and clinical data. All these HCWs were tested for COVID-19, in 2nd week of September 2020, as a hospital policy.
Anti SARS CoV2 antibodies were detected in 128/ 500 25.6% HCWs. A total of 195/ 500 39% enrolled cases had already tested positive for Covid-19 at least once in last six months by RT-PCR. Sixty eight percent of HCWs with previous COVID-19 positivity by RT- PCR tested positive for Anti SARS CoV2 antibodies, whereas only 2.76% of asymptomatic HCWs tested positive. Of 121 anti SARS-CoV-2 IgG positive persons, 70 57.85% had CT value < 25. Low CT value and asymptomatic cases had a strong reverse statistically significant association with SARS CoV2 IgG antibody positivity.
We report that sero-conversion rate in HCWs is similar to that in general population suggesting that preventive practices used in hospitals are satisfactory. Cases with low viral counts in respiratory sample and asymptomatic cases have lower rate of seroconversion.
The aim of the study was to trace and understand the origin of Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) through various available literatures and accessible databases. ...Although the world enters the third year of the coronavirus disease 2019 pandemic, health and socioeconomic impacts continue to mount, the origin and mechanisms of spill‐over of the SARS‐CoV‐2 into humans remain elusive. Therefore, a systematic review of the literature was performed that showcased the integrated information obtained through manual searches, digital databases (PubMed, CINAHL, and MEDLINE) searches, and searches from legitimate publications (1966–2022), followed by meta‐analysis. Our systematic analysis data proposed three postulated hypotheses concerning the origin of the SARS‐CoV‐2, which include zoonotic origin (Z), laboratory origin (L), and obscure origin (O). Despite the fact that the zoonotic origin for SARS‐CoV‐2 has not been conclusively identified to date, our data suggest a zoonotic origin, in contrast to some alternative concepts, including the probability of a laboratory incident or leak. Our data exhibit that zoonotic origin (Z) has higher evidence‐based support as compared to laboratory origin (L). Importantly, based on all the studies included, we generated the forest plot with 95% confidence intervals (CIs) of the risk ratio estimates. Our meta‐analysis further supports the zoonotic origin of SARS/SARS‐CoV‐2 in the included studies.
In host cells, Mycobacterium tuberculosis encounters an array of reactive molecules capable of damaging its genome. Non-bulky DNA lesions are the most common damages produced on the exposure of the ...pathogen to reactive species and base excision repair (BER) pathway is involved in the repair of such damage. During BER, apurinic/apyrimidinic (AP) endonuclease enzymes repair the abasic sites that are generated after spontaneous DNA base loss or by the action of DNA glycosylases, which if left unrepaired lead to inhibition of replication and transcription. However, the role of AP endonucleases in imparting protection against DNA damage and in the growth and pathogenesis of M.tuberculosis has not yet been elucidated. To demonstrate the biological significance of these enzymes in M.tuberculosis, it would be desirable to disrupt the relevant genes and evaluate the resulting mutants for their ability to grow in the host and cause disease. In this study, we have generated M.tuberculosis mutants of the base excision repair (BER) system, disrupted in either one (MtbΔend or MtbΔxthA) or both the AP endonucleases (MtbΔendΔxthA). We demonstrate that these genes are crucial for bacteria to withstand alkylation and oxidative stress in vitro. In addition, the mutant disrupted in both the AP endonucleases (MtbΔendΔxthA) exhibited a significant reduction in its ability to survive inside human macrophages. However, infection of guinea pigs with either MtbΔend or MtbΔxthA or MtbΔendΔxthA resulted in the similar bacillary load and pathological damage in the organs as observed in the case of infection with wild-type M.tuberculosis. The implications of these observations are discussed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Although peritoneal tuberculosis (TB) is one of the important differential diagnoses among cirrhotic patients with ascites, a peritoneal biopsy is not always available. High ascitic fluid adenosine ...deaminase (ADA) has been indicative of peritoneal TB. On the other hand, studies to assess its diagnostic utility based on the confirmation of peritoneal biopsy in cirrhotic patients are scarce.
Patients with new-onset ascites were enrolled prospectively from a tertiary hospital. Peritoneal biopsy was applied according to clinical judgment when required. Based on pathology diagnosis of the peritoneum, the diagnostic efficacy of ascitic fluid ADA for peritoneal TB was evaluated in total and cirrhotic patients, respectively.
Among 286 patients enrolled, 78 were diagnosed with peritoneal TB. One hundred and thirty-two patients had cirrhosis, and 30 of those were diagnosed with peritoneal TB. The mean ADA was 72.2 U/L and 22.7 U/L in the peritoneal and non-peritoneal TB group, respectively, among the total study population, and 64.0 U/L and 19.1 U/L in the peritoneal and non-peritoneal TB group, respectively, among the subgroup with cirrhosis. The area under the curve for ADA to diagnose peritoneal TB was 0.96 in the total study population with a cutoff value of 41.1 U/L, and 0.93 in cirrhotic patients with a cutoff value of 39.9 U/L.
The ascitic fluid ADA measurements showed high diagnostic performance for peritoneal tuberculosis in patients with ascites regardless of cirrhosis at a similar cutoff value.
Primaquine (PQ) is the only drug used to prevent relapse of malaria due to P. vivax and P. ovale, by eradicating the dormant liver form of the parasite (hypnozoites). The side‐effects associated with ...PQ limits is uses in treatment of malaria. To overcome the premature oxidative deamination and to increase the life span of drug in the biological system, the novel glyco‐conjugates of PQ were synthesized by coupling of primaquine with hexoses in phosphate buffer. The saccharide part of the hybrid molecules thought to direct the drug to the liver, where hypnozoites resides. All the synthesized compounds were fully characterized and evaluated for their radical curative activities. The three compounds viz glucoside (15a), galactoside (15b) and mannoside (15c) with high activity were tested for their activity in rhesus monkeys where the most active compound 15b showed twofold activity (100% radical curative activity at 1.92 mmol/kg) than the standard drug PQ diphosphate (3.861 mmol/kg). It is proposed that results from these studies may be advantageous to develop a new potent tissue schizonticide antimalarial compound.
The three compounds viz glucoside (15a), galactoside (15b), and mannoside (15c) with high activity were tested and most active compound 15b showed twofold activity than the standard drug Primaquine diphosphate.
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