Biosynthesis of Silver Nanoparticles by Marine Actinobacterium Nocardiopsis dassonvillei and Exploring Their Therapeutic Potentials

Nanoparticles have recently emerged as a popular research topic. Because of their potential applications in therapeutic applications, biosynthesized silver nanoparticles (Bio-AgNPs) have gained much attention in recent years. Cell-free extracts (CFE) from a marine culture of actinobacteria and silver nitrate were used to reduce Ag+ ions and create Bio-AgNPs. Nocardiopsis dasonvillei KY772427, a new silver-tolerant actinomycete strain, was isolated from marine water and used to synthesize AgNPs. In order to characterize Bio-AgNPs, UV-Vis spectral analysis, Fourier transform infrared (FTIR), transmission electron microscopy (TEM), and dynamic light scattering spectroscopy (DLS) were all utilized. Using UV-Vis spectroscopy, a peak in the surface plasmon resonance (SPR) spectrum at 430 nm revealed the presence of Bio-AgNPs. The TEM revealed spherical AgNPs with a diameter of 29.28 nm. DLS determined that Bio-AgNPs have a diameter of 56.1 nm and a negative surface charge (-1.46 mV). The minimum inhibitory concentration (MIC) of Bio-AgNPs was determined against microbial strains. Using resazurin-based microtiter dilution, the synergistic effect of Bio-AgNPs with antimicrobials was investigated. Pseudomonas aeruginosa had the lowest MIC of Bio-AgNPs (4 μg/ml). Surprisingly, the combination of antimicrobials and Bio-AgNPs had a significant synergistic effect on the tested strains. The insecticidal activity of Bio-AgNPs (200 μg/ml) against Macrosiphum rosae was found to be maximal after 36 h. Additionally, Bio-AgNPs demonstrated significant scavenging activity against 2,2'-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl (OH - ) radicals, with IC 50 values of 4.08 and 8.9 g/ml, respectively. In vitro studies using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay revealed a concentration-dependent decrease in cell viability when CaCo2 cells were exposed to Bio-AgNPs. With the decrease in cell viability, lactate dehydrogenase leakage (LDH) increased. The findings of this study open up a new avenue for the use of marine Nocardiopsis dasonvillei to produce Bio-AgNPs, which have significant antimicrobial, antioxidant, insecticidal, and anticancer potential.

P1492 A rare case of a spontaneous rupture of a congenital inter ventricular septum diverticulum in an adult

Introduction

A ventricular diverticulum is a rare cardiac anomaly with its true incidence is likely to be underestimated, as most patients are thought to be asymptomatic. Possible known complications include conduction abnormalities, rupture, bacterial endocarditis, and thromboembolism. We report a case of inter ventricular septum diverticulum detected incidentally in an adult during echocardiography and which ruptured spontaneously after 3 years of follow up.

Case report

A 36-year-old asymptomatic gentleman was referred for cardiac evaluation as a part of pre employment general check-up. He was controlled hypertensive on medical treatment. He had no history myocardial infarction (MI), arrhythmias, or stroke. He had never experienced exertional dyspnoea or chest pain. Physical examination was unremarkable.

Transthoracic echocardiography revealed mild left ventricle hypertrophy with normal global and regional contractility with an ejection fraction of 58%. In addition, it showed a myocardial out-pouching (11x9 mm) localized at the basal third of the posterior inter-ventricular septum and bulging into the right ventricle and moving in synchrony with the rest of the left ventricle with no shunt (figures A&B&C).

The patient’s history allowed us to exclude a post-ischemic LV aneurysm and an infective genesis of the lesion.

Contrast enhanced EKG gated cardiac computed tomography confirmed the presence of a blind ended diverticulum of the interventricular septum which was stretching and protruding into the right ventricle. The septum and the diverticulum were intact with no evidence of associated septal defects, (figures D&E&F).

Three years later, during his regular follow up, a loud pan-systolic murmur was heard along the left sternal border. His repeated echocardiographic study revealed a rupture of the inter ventricular septal diverticulum into the right ventricle, with a left to right shunt of a peak systolic gradient of 71 mmHg, (Fig G). His blood pressure was 100/60.

Cardiac magnetic resonance confirmed the rupture of the interventricular septum diverticulum. It revealed a tiny defect with a left to right shunt and the calculated QP/QS was 1.3, (fig H&I).

As the patient was asymptomatic and the shunt was insignificant, the decision was made to be managed conservatively and not to intervene with surgery at this point. This was to avoid the potential of surgical complications as disruption of the patient’s conduction system and the chance of post-operative arrhythmia.

Abstract P1492 Figure.

P1494 Incidental finding of aortic aneurysm formation following 34 years of coarctation repair by dacron patch aortoplasty

Introduction

Aneurysms are found following all types of surgical repair of aortic coarctation, especially after Dacron patch aortoplasty.

We describe the finding of an aortic aneurysm in an asymptomatic 52-year-old male, who was managed by Dacron patch aortoplasty for native coarctation of the aorta 34 years earlier.

Case report

A 52-year male, smoker, hypertensive on medication He had previous history of surgical repair of aortic coarctation at age of 18 years .

Repair was by Dacron patch aortoplasty. Since then, his regular follow up was unremarkable. Recently, he was referred for cardiac evaluation as a part of pre-employment general check-up. He was asymptomatic with no history of shortness of breath or chest pain.

Physical examination revealed that the pulse in the left arm was reduced in volume in comparison to the right one. The heart sounds were essentially normal but a pericardial murmur was audible, perhaps reflecting residual collateral flow. Blood pressure was 156/83 mmHg in right arm and 142/81 in the left arm.

Transthoracic echocardiography revealed mild left ventricular hypertrophy with normal global and regional contractility and an ejection fraction of 58%. Supra sternal window images showed dilatation of the three aortic arch branches. The distal portion of aortic arch just distal to origin of left subclavian artery was narrowed with a peak systolic gradient across of 34 mmHg. A cystic structure (1.7 cm x 1.9 cm) was visualized attached to the narrowed segment of the aorta, suggestive of a saccular aneurysm, (figures A&B&C).

Computed tomography aortogram showed a narrow-necked aneurysm arising from the posterolateral aspect of the distal aortic arch (anticipated site of the coarctation repair graft anastomosis). A small laminated thrombus was also noted within. Aneurysm measured approximately 2.2 x 3.3 cm in its craniocaudal and anteroposterior dimensions respectively, with no evidence of aortic luminal compromise. (figures D&E&F).

Management

Aneurysmectomy was performed subsequently. Interposition polyester grafts were used to reconstruct the aortic arch and proximal descending aorta and to connect this aortic segment to the subclavian artery via a lateral thoracotomy. The postoperative course thereafter was uneventful. Conclusion: This is a rare insidious complication of Dacron patch aortoplasty that occurred after more than 3 decades, which highlights the importance of diagnostic imaging in the follow up of these patients

Abstract P1494 Figure.

P885 Pulmonary artery stent implantation in an adult with chronic thromboembolic pulmonary stenosis

Introduction

Pulmonary artery stenosis presenting in adults is rare. Chronic thromboembolic pulmonary hypertension (CTEPH) is by far the most common cause of pulmonary artery stenosis. Stenosis in these patients are not caused by an abnormality of the arterial wall itself, but by intraluminal narrowing as a result of the only partially resolved and organized thromboembolism. In contrast to paediatric patients, in adults with pulmonary artery stenosis, pulmonary stenting is not routinely performed.

Case report

A 51-year male, smoker, diabetic, hypertensive, and with chronic kidney disease. He was diagnosed two years earlier with bilateral multiple pulmonary emboli and was maintained on oral anticoagulation therapy. Recently, he presented with gradually progressive shortness of breath and signs of right ventricular failure.

Diagnostic imaging: 1-Transthoracic and transesophageal echocardiography showed normal global systolic left ventricular function with no regional wall motion abnormalities, dilated right ventricle (RV) with moderately impaired function, severe pulmonic valve incompetence, mild tricuspid incompetence and a severely elevated right ventricular systolic pressure (RVSP) of 82 mmHg. In addition, a small rounded mass (6 x 11 mm) was visualized attached to the posterior wall of the RV outflow tract (RVOT) about 15mm proximal to the pulmonary valve annulus, (figure A). 2- Computed tomography pulmonary angiography showed a right main pulmonary artery (RPA) with circumferential narrowing, which was highly suggestive of chronic thrombosis. There was an abrupt tapering noted in the segmental branches of the right lower lobar pulmonary artery, with non-opacification of the distal arteries. No contrast opacification was noted in the right upper lobe pulmonary arteries. The left main pulmonary artery showed thickening of its bifurcation, again suggestive of chronic thrombosis, with narrowing of its left upper lobar branch, (figures B&C). 3-Cardiac magnetic resonance (CMR) showed a non enhancing RVOT mass protruding through the incompetent pulmonary valve during systole with features suggestive of a thrombus.

Management

In view of the clinical history, CTEPH was considered to be the most likely aetiology of the pulmonary hypertension. The decision was to perform balloon angioplasty and stent implantation in the RPA. Immediately after the procedure, RVSP was reduced from 80 to 50 mmHg. The clinical course after this procedure was uncomplicated and the patient showed significant clinical improvement.

Follow up CMR showed patent stent with improvement of RV function ( fig D)

Abstract P885 Figure.

Emergence of Multidrug- and Pandrug- Resistant Pseudomonas aeruginosa from Five Hospitals in Qatar

Background

A global rise in multidrug-resistant (MDR) nosocomial infections has led to a significant increase in morbidity and mortality. MDR Gram-negative bacteria (GNB) are recognised for rapidly developing drug resistance. Despite Pseudomonas aeruginosa being the second most common GNB isolated from healthcare associated infections, the magnitude of MDR P. aeruginosa (MDR-PA) has not been evaluated in Qatar.

Aim

To assess the prevalence and antimicrobial susceptibility patterns of MDR-PA from 5 major hospitals in Qatar.

Methods

A total of 2533 P. aeruginosa clinical isolates were collected over a one-year period. MDR-PA was defined as resistance to at least one agent of ≥ 3 antibiotic classes. Clinical and demographic data were collected prospectively.

Findings

The overall prevalence of MDR-PA isolates was 8.1% (205/2533); the majority of isolates were from patients exposed to antibiotics during 90 days prior to isolation (85.4 %, 177/205), and the infections were mainly hospital-acquired (95.1%, 195/205) with only 4.9% from the community. The majority of MDR-PA isolates were resistant to cefepime (96.6%, 198/205), ciprofloxacin, piperacillin/tazobactam (91%, 186/205), and meropenem (90%, 184/205). Patient comorbidities with MDR-PA were diabetes mellitus (47.3%, n=97), malignancy (17.1%, n=35), end-stage renal disease (13.7%, n=28) and heart failure (10.7%, n=22).

Conclusion

There was a significant prevalence of MDR-PA in Qatar, primarily from healthcare facilities and associated with prior antibiotic treatment. There was an alarming level of antimicrobial resistance to carbapenems. Our results are part of a national surveillance of MDR to establish effective containment plans.

Ribonucleotide reductase in Bacillus subtilis--evidence for a Mn-dependent enzyme

The reduction of 2'-ribonucleotides to 2'-deoxyribonucleotides, a unique step in DNA formation, is catalyzed by ribonucleotide reductase (RRase), an allosterically regulated, cell cycle-dependent enzyme. This work reports a reversible impairment of DNA formation and ribonucleotide reduction upon manganese depletion in Bacillus subtilis demonstrated through in vivo labeling with necleic acid precursors and enzyme assays with ether-permeabilized cells. No deoxyadenosylcobalamin-dependent reduction of ribonucleotides was detected in the cytosol, and the properties of a partially purified enzyme fraction, i.e., sensitivity towards EDTA and hydroxyurea (HU), indicated a metal-dependent type of RRase. The enzyme was enriched by gel filtration on Superose 12 from glycerol- or fumarate-grown cells and submitted to Q-band electron paramagnetic resonance (EPR) spectroscopy for further characterization of the metal center. A distinct Mn(II) signal was obtained in both preparations characteristic of a protein-bound mangaenese in a mononuclear metal center with axial symmetry. The intensity of this Mn signal was not affected by addition of the radical scavenger HU (10 mM) but reduced in the presence of 2.5 mM EDTA. On the basis of these results, we suggest that Bacillus subtilis has a Mn-dependent ribonucleotide reductase.