Ancestral reconstruction of the MotA stator subunit reveals that conserved residues far from the pore are required to drive flagellar motility

The bacterial flagellar motor (BFM) is a rotary nanomachine powered by the translocation of ions across the inner membrane through the stator complex. The stator complex consists of two membrane proteins: MotA and MotB (in H⁺-powered motors), or PomA and PomB (in Na⁺-powered motors). In this study, we used ancestral sequence reconstruction (ASR) to probe which residues of MotA correlate with function and may have been conserved to preserve motor function. We reconstructed 10 ancestral sequences of MotA and found four of them were motile in combination with contemporary Escherichia coli MotB and in combination with our previously published functional ancestral MotBs. Sequence comparison between wild-type (WT) E. coli MotA and MotA-ASRs revealed 30 critical residues across multiple domains of MotA that were conserved among all motile stator units. These conserved residues included pore-facing, cytoplasm-facing, and MotA-MotA intermolecular facing sites. Overall, this work demonstrates the role of ASR in assessing conserved variable residues in a subunit of a molecular complex.

A novel class of antimicrobial drugs selectively targets a Mycobacterium tuberculosis PE-PGRS protein

The continued spread of drug-resistant tuberculosis is one of the most pressing and complex challenges facing tuberculosis management worldwide. Therefore, developing a new class of drugs is necessary and urgently needed to cope with the increasing threat of drug-resistant tuberculosis. This study aims to discover a potential new class of tuberculosis drug candidates different from existing tuberculosis drugs. By screening a library of compounds, methyl (S)-1-((3-alkoxy-6,7-dimethoxyphenanthren-9-yl)methyl)-5-oxopyrrolidine-2-carboxylate (PP) derivatives with antitubercular activity were discovered. MIC ranges for PP1S, PP2S, and PP3S against clinically isolated drug-resistant Mycobacterium tuberculosis strains were 0.78 to 3.13, 0.19 to 1.56, and 0.78 to 6.25 μg/ml, respectively. PPs demonstrated antitubercular activities in macrophage and tuberculosis mouse models, showing no detectable toxicity in all assays tested. PPs specifically inhibited M. tuberculosis without significantly changing the intestinal microbiome in mice. Mutants selected in vitro suggest that the drug targets the PE-PGRS57, which has been found only in the genomes of the M. tuberculosis complex, highlighting the specificity and safety potency of this compound. As PPs show an excellent safety profile and highly selective toxicity specific to M. tuberculosis, PPs are considered a promising new candidate for the treatment of drug-resistant tuberculosis while maintaining microbiome homeostasis.

In Vitro and In Vivo Anti-Clostridioides difficile Effect of a Probiotic Bacillus amyloliquefaciens Strain

Clostridioides difficile infection (CDI) is a significant cause of hospital-acquired and antibiotic-mediated intestinal diseases and is a growing global public health concern. Overuse of antibiotics and their effect on normal intestinal flora has increased the incidence and severity of infections. Thus, the development of new, effective, and safe treatment options is a high priority. Here, we report a new probiotic strain, Bacillus amyloliquefaciens (BA PMC-80), and its in vitro/in vivo anti-C. difficile effect as a prospective novel candidate for replacing conventional antibiotics. BA PMC-80 showed a significant anti-C. difficile effect in coculture assay, and its cell-free supernatant (CFS) also exhibited a considerable anti-C. difficile effect with an 89.06 μg/ml 50% minimal inhibitory concentration (MIC) in broth microdilution assay. The CFS was stable and equally functional under different pHs, heat, and proteinase treatments. It also exhibited a high sensitivity against current antibiotics and no toxicity in subchronic toxicity testing in hamsters. Finally, BA PMC-80 showed a moderate effect in a hamster CDI model with reduced infection severity and delayed death. However, further studies are required to optimize the treatment condition of the hamster CDI model for better efficacy and identify the antimicrobial compound produced by BA PMC-80.

Ancestral Sequence Reconstructions of MotB Are Proton-Motile and Require MotA for Motility

The bacterial flagellar motor (BFM) is a nanomachine that rotates the flagellum to propel many known bacteria. The BFM is powered by ion transit across the cell membrane through the stator complex, a membrane protein. Different bacteria use various ions to run their BFM, but the majority of BFMs are powered by either proton (H+) or sodium (Na+) ions. The transmembrane (TM) domain of the B-subunit of the stator complex is crucial for ion selectivity, as it forms the ion channel in complex with TM3 and TM4 of the A-subunit. In this study, we reconstructed and engineered thirteen ancestral sequences of the stator B-subunit to evaluate the functional properties and ionic power source of the stator proteins at reconstruction nodes to evaluate the potential of ancestral sequence reconstruction (ASR) methods for stator engineering and to test specific motifs previously hypothesized to be involved in ion-selectivity. We found that all thirteen of our reconstructed ancient B-subunit proteins could assemble into functional stator complexes in combination with the contemporary Escherichia coli MotA-subunit to restore motility in stator deleted E. coli strains. The flagellar rotation of the thirteen ancestral MotBs was found to be Na+ independent which suggested that the F30/Y30 residue was not significantly correlated with sodium/proton phenotype, in contrast to what we had reported previously. Additionally, four among the thirteen reconstructed B-subunits were compatible with the A-subunit of Aquifex aeolicus and able to function in a sodium-independent manner. Overall, this work demonstrates the use of ancestral reconstruction to generate novel stators and quantify which residues are correlated with which ionic power source.

Melanin Bleaching and Melanogenesis Inhibition Effects of Pediococcus acidilactici PMC48 Isolated from Korean Perilla Leaf Kimchi

Overproduction and accumulation of melanin in the skin will darken the skin and cause skin disorders. So far, components that can inhibit tyrosinase, a melanin synthase of melanocytes, have been developed and used as ingredients of cosmetics or pharmaceutical products. However, most of existing substances can only inhibit the biosynthesis of melanin while melanin that is already synthesized and deposited is not directly decomposed. Thus, their effects in decreasing melanin concentration in the skin are weak. To overcome the limitation of existing therapeutic agents, we started to develop a substance that could directly biodegrade melanin. We screened traditional fermented food microorganisms for their abilities to direct biodegrade melanin. As a result, we found that a kimchi-derived Pediococcus acidilactici PMC48 had a direct melanin-degrading effect. This PMC48 strain is a new strain, different from P. acidilactici strains reported so far. It not only directly degrades melanin, but also has tyrosinase-inhibiting effect. It has a direct melanindecomposition effect. It exceeds existing melanin synthesis-inhibiting technology. It is expected to be of high value as a raw material for melanin degradation drugs and cosmetics.

Effect of Intravenous Paracetamol with Bupivacaine Scalp Nerve Block on Haemodynamics Response as Well as Anaesthetic Requirements during Supratentorial Craniotomies

Noxious stimuli during craniotomy may encourage hypertension and tachycardia, which may rise to morbidity in patients with intracranial hypertension. After craniotomy a moderate level of postoperative pain observed. The objective of this study was to observe the effect of intravenous paracetamol with bupivacaine scalp nerve block (SNB) on haemodynamics response as well as anaesthetic & analgesic requirements during supratentorial craniotomies. This is a single-blind, placebo-controlled, randomized clinical trial carried out in the Neurosurgery operation theatre from August 2015 to July 2017 under supervision of Department of Anaesthesia, Analgesia and Intensive Care Medicine of Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh. A total of 40 patients aged 18-60 years with supratentorial space occupying lesion undergoing craniotomy under general anaesthesia who were attended in the department of Neurosurgery, BSMMU were enrolled in this study and they were divided randomly into two groups, 20 patients in each. The Group A received 100ml normal saline infusion and 0.25% bupivacaine (20ml) in scalp block, while the Group B received intravenous injection paracetamol (1gm) and 0.25% bupivacaine (total 20ml) in scalp block. Statistical analyses were obtained Statistical Packages for Social Sciences (SPSS-22). The mean systolic blood pressure varied within the normal range in both groups. The mean DBP of Group B remained significantly lower than that of Group A in different follow up except at 30 minutes and 60 minutes after dura incision. However, mean MAP of Group B remained significantly lower than that of Group A in different time interval. The mean heart rate of Group B remained significantly lower than that of Group A. The mean intraoperative propofol as well as fentanyl requirements were significantly decreased in Group B in comparison to Group A. The combination of intravenous paracetamol with bupivacaine scalp nerve block provides better intra-operative haemodynamic stability and neurosurgical compliances for the patients undergoing supratentorial craniotomies under general anaesthesia.

Vitamin D Profile in Juvenile Idiopathic Arthritis Patients in a Tertiary Care Hospital in Bangladesh

There are multi-factorial causes of decrease in bone mass in Juvenile Idiopathic Arthritis (JIA) patients who correlate with the duration of active disease. By measuring the vitamin D level we can assess the deficiency or insufficiency earlier and can predict the risk of osteoporotic bone fracture & can give appropriate supplementation of vitamin D & calcium. This study was done to determine the status of serum 25(OH)D in patients with JIA and to see the relationship among various subtypes and disease duration. In this cross sectional study 30 (Thirty) newly diagnosed cases of JIA attending the pediatric rheumatology clinic of Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh from July 2014 to December 2015 were included. Thirty age and sex matched control were selected and serum 25(OH)D was measured in cases and controls. Among JIA patients, 60% and among controls 33% had hypo-vitaminosis D. In JIA group the mean level of serum 25(OH)D was lower than control group and the result is statistically significant in cases of poly-articular JIA and systemic JIA (SJIA). There is significant difference of the mean values of vitamin D levels in JIA and control groups for the cases of hypo-vitaminosis D. Level of serum 25(OH)D significantly decreased as disease duration continue increased. More than half of JIA patients had hypo-vitaminosis D. It is more significant in cases of poly-articular JIA and systemic JIA (SJIA). There was negative relationship between serum 25(OH)D level and disease duration.

Long-term effect of medium cut-off dialyzer on middle uremic toxins and cell-free hemoglobin

The medium cut-off (MCO) dialyzer has shown good clearance of large middle molecules, but its long-term effects are unclear. We investigated whether MCO hemodialysis (HD) over one year could reduce middle molecule levels and cell-free hemoglobin (CFH), without albumin loss. A prospective cohort study in 57 hemodialysis patients was conducted. The patients were assigned to the MCO dialyzer group or the high-flux dialyzer group, according to the HD machine they used. The reduction ratio (RR) and one-year changes in small and middle molecules and CFH were analyzed. Over a 12-month follow-up, MCO HD did not reduce the serum levels of middle molecules (lambda free light chain [FLC], from 135.7 ± 39.9 to 132.0 ± 39.1 mg/L; kappa FLC, from 168.2 ± 58.5 to 167.7 ± 65.8 mg/L; β2-microglobulin, from 25.6 ± 9.6 to 28.4 ± 4.8 mg/L) or albumin (from 3.96 ± 0.31 to 3.94 ± 0.37 g/dL). MCO HD provided excellent RR of lambda FLC (49.3 ± 10.3%), kappa FLC (69.6 ± 10.4%) and β2-microglobulin (80.9 ± 7.3%), compared to high-flux HD. CFH was also removed well during an MCO HD session (RR of CPH, 85.5 [78.7–97.3] %), but long-term change was not significant (from 57.8 [46.2–79.1] to 62.0 [54.6–116.7] mg/L). The MCO dialyzer can be used effectively and safely in conventional HD settings, but long-term effects on large middle molecules and CFH were not significant. Further studies are needed to verify clinical benefits of the MCO dialyzer.

In vitro activity of collinin isolated from the leaves of Zanthoxylum schinifolium against multidrug- and extensively drug-resistant Mycobacterium tuberculosis

BACKGROUND

Tuberculosis is a very serious infectious disease that threatens humanity, and the emergence of multidrug-resistant (MDR), extensively drug-resistant (XDR) strains resistant to drugs suggests that new drug development is urgent. In order to develop new tuberculosis drug, we have conducted in vitro anti-tubercular tests on thousands of plant-derived substances and finally found collinin extracted from the leaves of Zanthoxylum schinifolium, which has an excellent anti-tuberculosis effect.

PURPOSE

To isolate an anti-tubercular bioactive compound from the leaves of Z. schinifolium and evaluate whether this agent demonstrates any potential in vitro characteristics suitable for the development of future anti-tubercular drugs to treat MDR and XDR Mycobacterium tuberculosis.

METHODS

The methanolic extracts of the leaves of Z. schinifolium were subjected to bioassay-guided fractionation against M. tuberculosis using a microbial cell viability assay. In addition, following cell cytotoxicity assay, an intracellular anti-mycobacterial activity of the most active anti-tubercular compound was investigated after it was purified.

RESULTS

The active compound with anti-tubercular activity isolated from leaves of Z. schinifolium was identified as a collinin. The extracted collinin showed anti-tubercular activity against both drug-susceptible and -resistant strains of M. tuberculosis at 50% minimum inhibitory concentrations (MIC₅₀s) of 3.13-6.25 µg/ml in culture broth and MIC₅₀s of 6.25-12.50 µg/ml inside Raw264.7 and A549 cells. Collinin had no cytotoxicity against human lung pneumocytes up to a concentration of 100 µg/ml (selectivity index > 16-32).

CONCLUSIONS

Collinin extracted from the leaves of Z. schinifolium significantly inhibits the growth of MDR and XDR M. tuberculosis in the culture broth. In addition, it also inhibits the growth of intracellular drug-susceptible and drug-resistant tuberculosis in Raw264.7 and A549 cells. To our knowledge, this is the first report on the in vitro anti-tubercular activity of collinin, and our data suggest collinin as a potential drug to treat drug-resistant tuberculosis. Further studies are warranted to assess the in vivo efficacy and therapeutic potential of collinin.

In Vitro Effect of DFC-2 on Mycolic Acid Biosynthesis in Mycobacterium tuberculosis

DFC-2, a methyl 5-[2-(dimethylamino)ethoxy]-7,12-dioxo-7,12-dihydrodinaphtho[1,2-b:2',3'-d]furan-6-carboxylate, is reported to have antitubercular effects against Mycobacterium tuberculosis. At concentrations ranging from 0.19 to 0.39 μg/ml, DFC-2 inhibited both drug-susceptible and -resistant strains of M. tuberculosis. Microarray analyses were employed to gain insights into the molecular mechanisms of DFC-2's action in M. tuberculosis. The most affected functional gene category was "lipid biosynthesis," which is involved in mycolic acid synthesis. The decrease in transcription of genes related to mycolic acid synthesis was confirmed by RT-PCR. Furthermore, we found that DFC-2 triggered a reduction in mycolic acid levels, showing a similar pattern to that of mycolic acid synthesis inhibitor isoniazid. These results may explain how this compound kills mycobacteria efficiently by inhibiting mycolic acid synthesis.

Acute, subchronic oral toxicity, toxicokinetics, and genotoxicity studies of DFC-2, an antitubercular drug candidate

The infectious disease tuberculosis remains a serious global health issue and is responsible for nearly 1.8 million deaths every year. In our previous study, DFC-2 was confirmed to show anti-tubercular activity against drug-susceptible and drug-resistant strains of Mycobacterium tuberculosis. To support the safety-in-use of DFC-2 as an anti-tubercular drug, DFC-2 was tested via single- and 28-day repeated-dose oral toxicity study and mutagenicity assays. In the oral toxicity study, a single oral dose of DFC-2 at 2000 mg/kg did not produce deaths or abnormal lesions in the internal organs of rats. The results of a 28-day orally repeated dose of DFC-2 did not show treatment-related deaths or obvious toxicity symptoms in the animals treated with a dose of 300 mg/kg/day during the experimental period. Therefore, the no-observed-adverse-effect level (NOAEL) of DFC-2 was determined as 300 mg/kg/day for both male and female rats. In addition, DFC-2 showed no genetic toxicity in in vitro bacterial reverse mutation test, in vitro chromosomal aberration test, and in vivo mouse bone marrow micronucleus formation test. These results indicate that DFC-2 is a promising anti-tubercular drug candidate with a favorable safety profile.

In vitro activity of alpha-viniferin isolated from the roots of Carex humilis against Mycobacterium tuberculosis

This study explores the antitubercular activity of α-viniferin, a bioactive phytochemical compound obtained from Carex humilis. α-Viniferin was active against both drug-susceptible and -resistant strains of Mycobacterium tuberculosis at MIC₅₀s of 4.6 μM in culture broth medium and MIC₅₀s of 2.3-4.6 μM inside macrophages and pneumocytes. In combination with streptomycin and ethambutol, α-viniferin exhibited an additive effect and partial synergy, respectively, against M. tuberculosis H37Rv. α-Viniferin also did not show cytotoxicity in any of the cell lines tested up to a concentration of 147 μM, which gives this compound a selectivity index of >32. Moreover, α-viniferin was active against 3 Staphylococcus species, including methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant Staphylococcus aureus (MRSA), and methicillin-resistant Staphylococcus epidermidis (MRSE).

Thymoquinone (TQ) inhibits the replication of intracellular Mycobacterium tuberculosis in macrophages and modulates nitric oxide production

Background

Human tuberculosis, which is caused by the pathogen Mycobacterium tuberculosis, remains a major public health concern. Increasing drug resistance poses a threat of disease resurgence and continues to cause considerable mortality worldwide, which necessitates the development of new drugs with improved efficacy. Thymoquinone (TQ), an essential compound of Nigella sativa, was previously reported as an active anti-tuberculosis agent.

Methods

In this study, the effects of TQ on intracellular mycobacterial replication are examined in macrophages. In addition, its effect on mycobacteria-induced NO production and pro-inflammatory responses were investigated in Mycobacterium tuberculosis (MTB)-infected Type II human alveolar and human myeloid cell lines.

Results

TQ at concentrations ranging from 12.5 to 25 μg/mL and 6.25 to 12.5 μg/mL reduced intracellular M. tuberculosis H37Rv and extensively drug-resistant tuberculosis (XDR-TB) 72 h post-infection in RAW 264.7 cells. TQ treatment also produced a concentration-dependent reduction in nitric oxide production in both H37Rv and XDR-TB infected RAW 264.7 cells. Furthermore, TQ reduced the expression of inducible nitric oxide synthase (iNOS) and pro-inflammatory molecules such as tumor necrosis factor-alpha (TNF-α) and interlukin-6 (IL-6) in H37Rv-infected cells and eventually reduced pathogen-derived stress in host cells.

Conclusions

TQ inhibits intracellular H37Rv and XDR-TB replication and MTB-induced production of NO and pro-inflammatory molecules. Therefore, along with its anti-inflammatory effects, TQ represents a prospective treatment option to combat Mycobacterium tuberculosis infection.

Macrophage Activation Syndrome in Paediatric Rheumatic Diseases

Macrophage activation syndrome (MAS) is a potentially fatal complication of rheumatic disorders, which commonly occurs in systemic juvenile idiopathic arthritis (sJIA).This study was carried out with the aims of describing the clinical features, laboratory findings and outcomes of MAS associated with paediatric rheumatic diseases in the Department of Paediatrics, Bangabandhu Sheikh Mujib Medical University (BSMMU) and compare these results with previous studies on MAS. This retrospective study was conducted in the paediatric rheumatology wing of the Department of Paediatrics, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh. Clinical and laboratory profile of all the diagnosed cases of MAS were analyzed from the medical records from January 2010 to July 2015. Among 10 MAS patients, 6 were female and 4 were male. Seven patients of systemic JIA, two patients of SLE and one patient with Kawasaki Disease developed MAS in their course of primary disease. Mean duration of primary disease prior to development of MAS was 2.9 years and mean age of onset was 9.1 years. High continued fever and new onset hepatosplenomegaly were the hallmark of the clinical presentation. White blood cell count and platelet count came down from the mean of 16.2 to 10.2×10⁹/L and 254 to 90×10⁹/L. Mean erythrocyte sedimentation rate was dropped from 56 to 29 mm/hr. Six patients had abnormal liver enzyme level (ALT) and 5 had evidence of coagulopathy (prolonged prothrombin time and APTT) at the onset of disease. Hyperferritinnemia were found in all the patients. Bone marrow study was done in 5 patients but features of hamophagocytosis were found only in 2 patients. All patients received intravenous steroid and 3 patients who did not respond to steroid received additional cyclosporine. Mortality rate was 30% in this series. Macrophage activation syndrome is a fatal complication of paediatric rheumatic diseases among which s-JIA was predominant. Early diagnosis and aggressive therapy is essential to reduce the morbidity and mortality of this illness.

Poncet's disease (tubercular rheumatism) - a case report

Poncet's disease is a rare condition in childhood. It occurs due to immunological reaction to tubercular protein resulting in reactive arthritis and manifest with polyarthritis associated with features of active tuberculosis. We are reporting a case of Poncet's disease that was initially treated as a case of Juvenile Idiopathic Arthritis (JIA) without any improvement. The diagnosis was made clinically from history and physical findings with supportive radiological findings and confirmed by granulomatous changes on FNAC. Our patient improved dramatically after treatment with anti-tubercular drugs. Though very rare, Poncet's disease should be strongly considered in the differential diagnosis of fever and polyarthritis of obscure cause, especially in tubercular endemic countries like ours.

Moebius syndrome with Taussig-Bing anomaly

We report a 6 years old male child, presented with difficulty in swallowing, crying and smiling from early infancy and recurrent episodes of cyanosis on exertion for about 2 years. He had facial dysmorphism, clubbing and polydactyly and right sided lower motor neuron type of facial nerve palsy. On examination and relevant investigations findings were consistent with Moebius syndrome and Taussig-Bing anomaly. Moebius syndrome comprises of congenital facial nerve palsy with or without palsy of the other cranial nerves and the associated organ system malformations. Taussig-Bing anomaly is a rare congenital heart malformation consisting of a transposed aorta, a large pulmonary artery which arises primarily from the right ventricle and ventricular septal defect. Simultaneous occurrence of Moebius syndrome and Taussig-Bing anomaly has not yet been reported in the past.

Relationship between Ig-E Levels and Lung Function Tests in Children with Asthma

Background: Asthma is the most common chronic disorder in childhood. A high level of Ig E is associated with asthma. Objectives: The present study was carried out to observe the relation of serum IgE level with lung function parameters in asthma children and apparently healthy normal children. Methods: This study was carried out in the out patient department of paediatrics, Dhaka Medical College, Dhaka between January 2010 and June 2010. Total sixty children with age range from six to fifteen years of both sexes were included in this study. Thirty children suffering from asthma and thirty apparently healthy children with no systemic disorder were taken as study population. Serum Ig-E levels were measured in all subjects using a standard Immulite assay by ELISA method. Subjects were classified as having high IgE if their total IgE level was greater than or equal to 100 IU /ml .Subjects were classified as having low IgE if their total IgE level was less than 100 IU /ml. Spirometry was conducted on all patients by using Spirolab a new generation spirometer according to American Thoracic Society standards. Data were analyzed by unpaired t test and Chi-squares test. Results: The mean percentage of predicted values of FEV1, FVC, FEV1/FVC% were significantly lower in high Ig E (>100 IU/ml) level group in comparison with low Ig E(<100 IU/ml) group. Conclusion: Therefore the result of the present study reveals that higher IgE is related with lower lung function and also there were more chance in symptoms based asthma in our study populations.  DOI: 10.3329/jdmc.v19i1.6242 J Dhaka Med Coll. 2010; 19(1) : 3-6.