Gram-positive Research Articles

Investigating the Inhibitory Effect of Animal Antimicrobial Peptides on Gram-Positive and Gram-Negative Bacteria in Diabetic Foot Ulcers

Investigating the Inhibitory Effect of Animal Antimicrobial Peptides on Gram-Positive and Gram-Negative Bacteria in Diabetic Foot Ulcers

Novel, eco-friendly α-tocopherol/layered double hydroxides/poly(3-hydroxyoctanoate)-based active packaging materials with enhanced antimicrobial, barrier and antioxidant activities

Among various climate actions taken as a response to environmental concerns, important and highly influential are ones related to the packaging industry being still one of the largest plastic sectors responsible for the majority of post-consumer wastes. Therefore, in this manuscript, for the first time assessment of the potential application of biodegradable bacterially derived poly(3-hydroxyoctanoate) (P(3HO)) doped with functional 2D nanoparticles as a more sustainable active packaging material has been investigated. In particular, P(3HO) combined with two types of layered double hydroxide (LDHs) modified with α-tocopherol (type of vitamin E) was applied for the fabrication of polymeric nanocomposite films and a comprehensive investigation of their structure and relevant properties (mechanical, barrier, bactericidal, and antioxidative) was performed. Permeation study revealed that P(3HO)-based films with 4 wt% tocopherol-modified nanoparticles meet the barrier requirements for storing fruits and vegetables, whereas antibacterial assay indicated inhibited growth of Gram-positive bacteria (particularly S. Aureus). Monitoring of polyphenols (PPH) content in strawberries after 6 days of storage at room conditions showed a slightly higher level of PPH with reference to fresh fruits, which indicates the preserved freshness of strawberries kept in P(3HO) containing 4 wt% Zn-based LDHs modified with tocopherol contrary to fruits kept in commercial polypropylene packaging which led to significant drop in PPH content. Thus, the application-focused experiments indicated that investigated P(3HO)-based nanocomposites are promising candidates for more sustainable active packaging that may extend the shelf-life of fruits and protect consumers from food-borne pathogenic bacteria.

The Wheel of Fortune: Helical Wheel Alanine Scanning of a Spider Venom Antimicrobial Peptide Reveals Residues Involved in Antimicrobial and Cytotoxic Activity.

A preference for several amino acids is observed to occur at particular positions of cationic α-helical antimicrobial peptides (AMPs), which ensures the formation of amphipathic regions once they assume their correct secondary structure in membranes or membrane-mimicking environments and makes them active against pathogens. This study determined the effect of alanine mutations on the secondary structure and bioactivity of lyp1987 (GRLQAFLAKMKEIAAQTL-NH2), a cationic α-helical AMP obtained from the venom of Lycosa poonaensis which exhibits broad range activity against Gram-positive and Gram-negative bacteria with micromolar minimum inhibitory concentrations (MIC). CD spectroscopy revealed no significant difference in the secondary structure, with all alanine-substituted analogs exhibiting predominantly α-helical structure in buffered 2,2,2-trifluoroethanol solution. Alanine substitution at Glu12 and Thr17 increased the activity of lyp1987 against Gram-positive and -negative bacteria, while alanine substitution at Lys9 increased its selectivity against Gram-positive bacteria. Further investigation can be done to determine positions and substitutions that will give less cytotoxic analogs.

Synthesis, characterization and antibacterial activity of hexasubstituted Coumarin-based Schiff base derivative of cyclophosphazene

This study focuses on synthesis and characterization of hexa-substituted coumarin based Schiff base derivative of cyclotriphosphazene (Compound 3). The antibacterial activity of Compound 3 was evaluated against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Pseudomonas aeruginosa (P. aeruginosa), and Klebsiella pneumoniae (K. pneumoniae) bacterial strains using minimum inhibitory concentration (MIC) and percentage-killing method. Compound 3 exhibited a lower MIC of 300 μg/mL against S. aureus than 500 μg/mL for P. aeruginosa and K. pneumoniae, indicating greater efficacy against Gram-positive bacteria. Percentage-killing data confirmed Compound 3 significant bactericidal activity against S. aureus across concentrations ranging from 100 to 500 μg/mL, comparable to ampicillin. In contrast, its efficacy against Gram-negative strains was lower, suggesting a more selective spectrum of activity. These findings suggest that Compound 3 shows promise as a potential antibacterial agent with preferential activity against Gram-positive bacteria, warranting further investigation into its mechanism of action and therapeutic potential.

Lactoferrin: a secret weapon in the war against pathogenic bacteria

The excessive use of antibiotics to treat bacterial infectious diseases in all living beings has caused a global epidemic of bacterial resistance to antibiotics, leading to the emergence of multidrug-resistant and pandrug-resistant strains. In 2019, the World Health Organization (WHO) reported that antimicrobial resistance causes at least 700,000 deaths per year worldwide. Therefore, in this global war against microorganisms, a therapeutic alternative is necessary to help us win this battle. A key in this race against the clock could be lactoferrin (Lf), a cationic glycoprotein of the mammalian innate immune system that is highly conserved among mammals. Lf is a multifunctional glycoprotein with immunomodulatory, anticarcinogenic, wound-healing, antioxidant, antimicrobial, and bone regeneration properties, in addition to improving the gut microbiota. Lf limits the growth of microorganisms through the sequestration of iron but can also interact directly with some components of the outer membrane of Gram-negative bacteria or bind to teichoic acids in Gram-positive bacteria, destabilizing the membrane and resulting in lysis. Moreover, cleavage of the Lf molecule could promote the production of lactoferricins (Lfcins) and lactoferrampin (Lfampin) from the N-terminal end, which are known to often have stronger antimicrobial effects than the native molecule, as well as analogous peptides, such as HLopt2, which have also shown enhanced antimicrobial activity. Bovine Lf (bLf) has been approved by the US Food and Drug Administration (FDA), and the European Food Safety Authority for its use as a dietary supplement in food products. Because of its effectiveness, accessibility, low cost, and nontoxicity, Lf could be a promising alternative for preventing or treating infections in animals and humans.

Bacterial Photodynamic Inactivation: Eradication of Staphylococcus aureus and Escherichia coli Mediated by Pyridinium-Pyrazolyl Zinc(II) Phthalocyanines.

Antimicrobial resistance remains an enduring global health issue, manifested when microorganisms, such as bacteria, lack responsiveness to antimicrobial treatments. Photodynamic inactivation (PDI) of microorganisms arises as a noninvasive, nontoxic, and repeatable alternative for the inactivation of a broad range of pathogens. So, this study reports the synthesis, structural characterization, and photophysical properties of a new tetra-β-substituted pyridinium-pyrazolyl zinc(II) phthalocyanine (ZnPc 1a) that was compared with two previously described pyridinium-pyrazolyl ZnPcs 2a and 3a. The PDI efficacy of these three ZnPcs (1a-3a) against a drug-resistant Gram-positive bacterium (as Staphylococcus aureus) and a Gram-negative bacterium (as Escherichia coli) is also reported. The PDI efficacy toward these bacteria was examined with ZnPcs 1a-3a in the 5.0-10.0 μM range using a white light source with an irradiance of 150 mW/cm2. All ZnPcs displayed a significant PDI activity against S. aureus, with reductions superior to 3 Log CFU/mL. Increasing the treatment time, the E. coli was inactivated until the detection limit of the method (>6.3 Log CFU/mL) using the quaternized ZnPcs 1a-3a (10.0 μM, 120 min) being the inactivation time was reduced when added the KI for ZnPcs 1a and 3a. These findings demonstrate the effective PDI performance of pyridinium-pyrazolyl group-bearing PSs, indicating their potential use as a versatile antimicrobial agent for managing infections induced by Gram-negative and Gram-positive bacteria.

Listeria in Pregnancy—The Forgotten Culprit

Listeria monocytogenes is a Gram-positive bacterium that causes listeriosis, a severe foodborne illness that is particularly dangerous during pregnancy. It thrives in diverse environments, including refrigerated conditions and food production facilities, due to its adaptability to varying temperatures, pH levels, and salt concentrations. Its virulence stems from the ability to invade host cells, particularly macrophages and epithelial cells, and avoid, or at least postpone, immune detection by utilizing virulence factors such as internalins, listeriolysin O, and actin assembly-inducing protein. This intracellular motility and biofilm formation make LM a persistent pathogen in food safety and public health. Pregnant women are at a much higher risk of listeriosis, which can result in serious fetal complications such as miscarriage, stillbirth, and preterm labor due to LM’s affinity for placental tissues. The vertical transmission of LM from mother to fetus can lead to neonatal listeriosis, which can result in sepsis and meningitis, with high mortality rates if not promptly treated. Early diagnosis and treatment with antibiotics, such as ampicillin or gentamicin, are crucial for maternal and neonatal outcomes.

Zn(II)-based mechanically flexible metallosupramolecular network: Investigating rheology, morphology, anti-bacterial effect and semiconducting device performances

Synthesis of supramolecular Zn(II)-metallogel of succinic acid with N,N′-dimethyl formamide (DMF) solvent has been explored in this present study. Succinic acid is used as a low molecular weight gelator (LMWG) and DMF acts as a metallogel-immobilized solvent-media. Mechanical flexibility, viscous, and elastic behaviours of the metallogel are characterized by exhaustive rheological experiments. Different rheological parameters like storage modulus (G′) and loss modulus (G″) are evaluated for certain regions of shear strain and angular frequency. The morphological decoration of xerogel material obtained from Zn(II)-based metallosupramolecular gel (i.e., Zn-Succinic) has been visualized through field emission scanning electron microscope (FESEM). Energy dispersive X-ray analysis (EDX) verifies the active involvement of metallogel-forming chemical constituents. The flexible metallosupramolecular scaffold-construction strategy has been unveiled through infrared spectroscopic data and ESI-Mass investigations. The antibacterial potency of Zn(II)-directed metallogel has also been verified against several Gram-positive bacteria (i.e., Bacillus cereus (ATCC 13061), Bacillus subtilis (MTCC 121), Listeria monocytogenes (MTCC 657), Staphylococcus aureus (MTCC 96)), and two Gram-negative bacterial strains (i.e., Salmonella typhimurium (MTCC 98) and Escherichia coli (MTCC 1667)). Even, Zn-Succinic metallogel exhibits Schottky diode behaviour with a significant non-linear rectifying nature in I-V curve, proving the semiconducting diode features with electrical parameters.

Silver nanoparticles synthesized using aerial part of Achillea fragrantissima and evaluation of their bioactivities

Achillea fragrantissima (A. fragrantissima), a desert plant, is used internally in Arabian traditional medicine to treat inflammatory, spasmodic gastrointestinal disorders, and hepatobiliary diseases. The study focuses on the environmentally friendly production of silver nanoparticles (AgNPs) from the water-based aerial parts of the A. fragrantissima plant and their ability to kill bacteria and cells. Ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR) were used to describe the AgNPs. They were then tested for their ability to fight cancer and bacteria. A change in colour from yellow to brown and a surface plasmon resonance peak at 440 nm, seen with UV-Vis spectroscopy, showed that AgNPs had formed. In a Gas Chromatography-Mass Spectrometry (GC-MS) test of the aerial parts of A. fragrantissima, twenty bioactive components were found. These included isolongifolol and 3E,10Z-Oxacyclotrideca-3,10-diene-2,7-dione, methylbuta-1,3-dienyl)-7-oxabicyclo [4.1.0] heptan-3-ol. The extract exhibited high phenolic and flavonoid content (77.52 ± 1.46 mg GAE/g dry weight and 59 ± 2.17 mg QE/g dry weight, respectively). According to the IC50 values of 17.2 ± 1.18 and 14 ± 2.43 µg/mL, the AgNPs had a lot of power to kill cancer cells from the MCF-7 and HepG2 lines. Some genes that cause cell death (caspase-3, 8, 9, and Bax) were turned on more in the treated cells compared to the control cells that had not been treated. These genes were Bcl-xL and Bcl-2. Additionally, substantial activity against both Gram-positive bacteria and Gram-negative bacteria was found by antibacterial screening. Overall, this study underscores A. fragrantissima’s diverse biological activity and its potential in drug discovery and nanomedicine, promoting the development of natural antibacterial and anticancer therapies.

Synthesis, Biological Evaluation, andMolecular Docking Studies of Indole-Based Heterocyclic Scaffolds as Potential Antibacterial Agents.

This study aimed to synthesize C3-indole derivatives linked to various heterocyclic scaffolds, including thiophenes, thiazolidine-4-ones, and 1,3,4-thiadiazoles, via the reaction of ethylthioacetanilide 2 with different α-haloketones.The structures of the target compounds were established using 1H and 13C nuclear magnetic resonance spectroscopy, mass spectrometry, infrared spectroscopy, and elemental analysis. The synthesized compounds were tested for antimicrobial activity against different microbes: S. aureus ATCC 6538 (Gram-positive bacteria), E. coli ATCC 25933 (Gram-negative bacteria), C. albicans ATCC 10231 (yeast), and fungi (A. niger NRRL-A326). Thiophene 6a, thiazolidine-4-one 8, and compound 10d exhibited the highest antimicrobial activities. The molecular docking study showed that compounds 2, 4, 6a, and 6c had good binding energy and favorable binding modes of interactions with the DNA gyrase B enzymes (PDB: 3U2D) and (PDB: 1S14). The results showed that the NH group of the indole in compounds 2 and 4, together with the nitrile group (CN), played an important role in inhibiting DNA gyrase B of S. aureus, PDB: 3U2D. Furthermore, the NH of the indole ring, together with the ethylamino group of compound 2, was crucial in inhibiting DNA gyrase B of E. coli, PDB: 1S14. These results could inspire further development of indole derivatives as antimicrobial drugs.

Bacterial profiles and their antibiotic susceptibility patterns in neonatal sepsis at the University of Gondar Comprehensive Specialized Hospital, Ethiopia.

Neonatal sepsis is a major cause of morbidity and mortality worldwide. Understanding the bacterial profiles and antibiotic susceptibility patterns causing neonatal sepsis is crucial for guiding appropriate treatment, improving patient outcomes, and combating the emergence of antibiotic resistance. Despite its importance, data regarding neonatal sepsis in the study area is limited. Therefore, this study aimed to characterize the bacterial pathogens and identify associated factors among neonates with suspected sepsis at the University of Gondar Comprehensive Specialized Hospital, Ethiopia. A cross-sectional study was conducted by reviewing laboratory records of neonates admitted for suspected sepsis from January 2019 to December 2021. Data were checked for completeness and encoded in a spreadsheet program. Then, data were exported to STATA version 17 for analysis. Descriptive statistics such as frequency and percentage were computed. The association between neonatal sepsis and potential risk factors was assessed using Pearson's chi-square test. A p-value of < 0.05, was considered statistically significant. A total of 1,236 neonates were included. Of these, 96.2% (1,190/1,236) had a fever before admission. The prevalence of culture-confirmed sepsis was 25.4% (314/1,236). Bacterial pathogens accounted for 23% (284/1,236) of these isolates, with Gram-negative bacteria being more prevalent at 75.3% (214/284) than Gram-positive bacteria at 24.7% (70/284). The most frequently isolated bacterial pathogens were K. pneumoniae 38.7% (110/284) and S. aureus 13% (37/284). The isolates demonstrated a high resistance level to commonly used antibiotics, with 61.6% exhibiting multidrug resistance. K. pneumoniae showed the highest rate of multidrug resistance (90.9%). Neonatal sepsis was associated with several factors, including fever before and after admission, hypothermia, increased respiration, suspected pneumonia, and suspected meningitis. This study identified a high prevalence of culture-confirmed sepsis in neonates at UoGCSH, with Gram-negative bacteria, especially K. pneumoniae, dominating the isolated pathogens. The isolated bacteria exhibited alarming resistance to commonly used antibiotics, with a high proportion demonstrating multidrug resistance. Implementing effective antibiotic stewardship programs is crucial to optimize antibiotic use, reduce unnecessary prescriptions, and curb the spread of resistant strains.

Bacterial inhibition and biofilm eradication ability of low-toxic deep eutectic solvents prepared from lactic acid and quaternary ammonium compounds

In the present communication, the preparation of deep eutectic solvents (DESs) based on an aqueous solution of lactic acid (LA) and two different quaternary ammonium compounds, choline chloride (ChCl) and tetraethylammonium chloride (TEAC), is proposed for the application as an antibacterial agent. The antibacterial and cytotoxic properties of the DESs obtained were studied and found to be highly effective in inhibiting both Gram-positive and Gram-negative bacteria and eradicating bacterial biofilms. Moreover, the DESs obtained exhibited reduced cytotoxicity towards soft tissue cells compared to the aqueous LA solution. The excellent antibacterial properties and low cytotoxicity of the DESs prepared make them a promising candidate for the development of novel antimicrobial agents or antibacterial eutectogels for delivery systems and tissue engineering applications.

Steroids produced by Cladosporium anthropophilum, an endophytic fungus Isolated from Avicennia marina (Forssk.) Vierh and Their Antibacterial Activity

This work was conducted to isolate the steroid compounds from an endophytic fungus Cladosporium anthropophilum and determine their effects against 4 strains of bacteria. The fungi were afforded from a mangrove plant Avicennia marina (Forssk.) Vierh of Acanthaceae family, growing in West Java, Indonesia. The fermentation and isolation of C. anthropophilum yielded 3 ergostane-type steroids including a highly oxidized one, identified as penicisteroid A (1), ergosterol (2), and ergosterol-5,8-peroxide (3), together with 2 stigmastanes, characterized as stigmasterol (4), and stigmasterol-5,8-peroxide (5). The elucidation structure of all isolated steroids was performed by extensive spectroscopic measurements (MS, IR, 1D, and 2D NMR) and supported by a comparison of previously reported spectral data. Subsequently, the potential of the 5 steroids as well as methanol, n-hexane, and ethyl acetate extracts were evaluated against 2 Gram-positive bacteria, Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 and 2 Gram-negative bacteria, Vibrio harveyi ATCC 5339 and Escherichia coli ATCC 25922. The results showed that none of the isolated steroids were active, while the 3 extracts exhibited significant inhibition against all the tested bacteria’s growth and enabled us to propose the synergistic effects between active compounds in these extracts and their antibacterial activity. HIGHLIGHTS An isolated and identified endophytic fungus, Cladosporium anthropophilum, from a mangrove plant Avicennia marina (Forssk.) Vierh yielded five steroids. A chromatography technique and spectroscopic method were utilized for separation processes and structure determination, respectively. An antibacterial assay against two Gram-positive bacteria ( aureus and E. faecalis) and two Gram-negative bacteria (V. harveyi and E. coli) implied the synergistic effects between five isolated steroids and their parent extracts. A further investigation is highly recommended to explore the possibility of these five steroids as a potential source of active compounds. GRAPHICAL ABSTRACT

Identification of pathogenic bacteria from eggshell of leatherback sea turtle (Dermochelys coriacea) in Lampuuk Beach, Aceh Besar using 16S rRNA gene

Currently, the leatherback turtle population in Indonesia tends to decline. One of the factors that cause turtles' existence is the turtle eggs that fail to hatch because bacteria contaminate them, 80% of the reasons turtle eggs fail to hatch are due to infection by microorganisms found on the eggshell. Turtle eggs have a soft structure and there are pores that function for gas exchange and water absorption. Microorganisms in sand can infect turtle eggs through the pores and cause hatching failure. This study aims to isolate and identify pathogenic bacteria found in leatherback turtle eggshell (Dermochelys coriacea) from Lampuuk Beach, Aceh Besar, based on the 16S rRNA gene analysis. Eight eggshell samples from leatherback turtle eggs that failed and hatched were cultured on Nutrient Agar (NA) medium. Then, the samples were inoculated on a blood agar medium for haemolysis test. Molecular identification of the 16S rRNA gene was also carried out to determine bacterial species. A total of five bacterial colonies from leatherback turtle eggshells were successfully isolated consisting of two Gram-negative bacteria (Penyu Belimbing Aceh (PBA) = PBA-1 and PBA-2 and three Gram-positive bacteria (PBA-3, PBA-4, and PBA-5). Based on the haemolysis test, the five bacterial isolates were unable to haemolyze blood. Bacterial DNA of PBA-1 and PBA-2 were successfully isolated and amplified using polymerase chain reaction (PCR) with a DNA target of ~1500 bp. Analysis using BLASTN and phylogenetic tree construction showed that PBA-1 isolate had 98.64% similarity with Acinetobacter baumannii, while PBA-2 isolate had 97.82% similarity with Enterobacter kobei. Both bacteria are members of the Enterobacteriaceae family. It can be concluded that, there were two pathogenic bacteria can potentially be opportunistic pathogens found in leatherback turtle eggshells that failed or succeeded in hatching, namely A. baumannii and E. Kobei

Investigation on taxonomy, secondary metabolites and antibacterial activity of Streptomyces sediminicola sp. nov., a novel marine sediment-derived Actinobacteria.

Marine actinomycetes, especially Streptomyces, are recognized as excellent producers of diverse and bioactive secondary metabolites on account of the multiplicity of marine habitations and unique ecological conditions, which are yet to be explored in terms of taxonomy, ecology, and functional activity. Isolation, culture and genome analysis of novel species of Streptomyces to explore their potential for discovering bioactive compounds is an important approach in natural product research. A marine actinobacteria, designated strain SCSIO 75703T, was isolated, and the potential for bioactive natural product discovery was evaluated based on genome mining, compound detection, and antimicrobial activity assays. The phylogenetic, phenotypic and chemotaxonomic analyses indicate that strain SCSIO 75703T represents a novel species in genus Streptomyces, for which the name Streptomyces sediminicola sp. nov. is proposed. Genome analysis revealed the presence of 25 secondary metabolite biosynthetic gene clusters. The screening for antibacterial activity reveals the potential to produce bioactive metabolites, highlighting its value for in-depth exploration of chemical constituents. Seven compounds (1-7) were separated from the fractions guided by antibacterial activities, including three indole alkaloids (1-3), three polyketide derivatives (4-6), and 4-(dimethylamino)benzoic acid (7). These primarily antibacterial components were identified as anthracimycin (4), 2-epi-anthracimycin (5) and β-rubromycin (6), presenting strong antibacterial activities against Gram-positive bacteria with the MIC value ranged from 0.125 to 16μg/mL. Additionally,, monaprenylindole A (1) and 3-cyanomethyl-6-prenylindole (2) displayed moderate inhibitory activities against α-glucosidase with the IC50 values of 83.27 and 86.21μg/mL, respectively. Strain SCSIO 75703T was isolated from marine sediment and identified as a novel species within the genus Streptomyces. Based on genomic analysis, compounds isolation and bioactivity studies, seven compounds were identified, with anthracimycin and β-rubromycin showing significant biological activity and promising potential for further applications.

The Description of Microbial Pattern and Antibiotic Sensitivity Among Pediatric Patients at RSUP M Djamil Padang

Background Infection alludes to the invasion and multiplication of either microorganisms or parasites inside bodily tissues. The management of such infections is closely interrelated to the use of antibiotics. Ineffective use of antibiotics is contributed to the antibiotic resistance. Severe disease complications and lengthy hospital stays are among essential reasons why physicians may prescribe myriad types of antibiotics for longer durations. In effort to diminish resistance, the selection of antibiotics ought to be based on information about the bacterial spectrum causing the infection and the patterns of sensitivity to antibiotics. Annual reporting of microbial patterns and sensitivity testing is essential, particularly for pediatric ward patients, as it provides a guide for administering relevant antibiotics and preventing further spread of infections. Objectives This study evaluated microbial patterns, sensitivity test results, and antibiotic resistance among patients in the pediatric ward of RSUP M Djamil Padang from January-December 2020, with a total of 138 samples. Results The proportion of gram-negative and gram-positive bacteria are 83.3% and 16.7%, respectively. The most prevalent gram-negative bacteria are Klebsiella pneumoniae (28.9%), Escherichia coli (26.1%). Pseudomonas aeruginosa (7.9%), Staphylococcus epidermidis (7.2%) and Acinetobacter baumannii (3.7%) also present. These bacteria are predominantly found in samples of feces, urine, and blood. Gram-positive bacteria show notable resistance to the antibiotics such as erythromycin (22.2%), trimethoprim-sulfamethoxazole (19%), and ciprofloxacin (15.8%), while being sensitive to chloramphenicol (17.4%), vancomycin (15.1%), and tetracycline (12%). In contrast, gram-negative bacteria exhibit resistance to ampicillin (16.5%), ceftriaxone (12.1%), and ceftazidime (11.3%), but are sensitive to amikacin (19.8%), meropenem (19.4%), and gentamicin (10.9%). Keywords: microbial patterns, antibiotic sensitivity, pediatric ward

Ag induced plasmonic TiO2 for photocatalytic degradation of pharmaceutical under visible light: Insights into mechanism, antimicrobial and cytotoxicity studies

Global concerns include water scarcity and shortage, which are escalated by organic pollutants such as naproxen (NPX) that deteriorate drinking water and taint access to safe drinking water by humans. Moreover, NPX may cause gastrointestinal difficulties, cardiovascular risks, kidney damage, allergic reactions, liver toxicity, bleeding issues and pregnancy risks, hence it is essential to remove it in water. Ag-TiO2 was synthesized by hydrothermal method for NPX degradation. Ag on TiO2 reduced the band gap and surface area of TiO2 and resulted in a plasmonic Ag-TiO2 composite of 0.2 % Ag. The photocatalytic degradation of 0.2 % Ag-TiO2 was 80 % in 180 minutes using a solar simulator during NPX degradation with a first order reaction rate that was 3.6 times faster than that of pure TiO2 and the catalyst showed good stability for four cycles. The dual activity of Ag0 surface plasmon resonance improved light absorption capability and enhanced charge transfer for increased photodegradation rate and stability. The antibacterial studies demonstrated that 0.2 % Ag-TiO2 posted strong antibacterial properties under light irradiation and less in the dark, with a greater effect on gram-negative than gram-positive bacteria. The minimum inhibitory concentration (MIC) values of 620, 1250, 2500, 2500 µg/mL were attained against B. subtilis, S. aureus, E. coli and S. typhimurium bacteria, respectively. The low cell toxicity of 0.2 % Ag-TiO2 was determined using human embryonic kidney (HEK293) cells with an inhibitory concentration (IC50) of 61.09 ± 0.24 µg/mL under light irradiation. Radical trapping experiments demonstrated that hydroxyl radicals (OH•) played a vital role during the degradation and bactericidal activity of NPX under light irradiation. This work advances new insights on the synthesis of less toxic nanoparticles with high photocatalytic and bactericidal activity for possible applications at industrial scale.

Functionalized polyaniline nanofibrils on lamellar structured zirconium for effective bone mineralization

The surface physiology of certain implant material has the ability to promote implant–cell signalling process through which a stable environment is formed. The formation of this favourable environment hastens the process of biomineralization and regeneration. In this context, Zirconium (Zr) when treated with alkali undergoes a surface modification which results in the development of a lamellar structured Zirconium (ATZ). Further, encapsulation of polyaniline (PAni) on ATZ was achieved through the electropolymerization technique which results in an effective and homogeneous electrodeposition of PAni nanofibrils on ATZ surface. A high resolution scanning electron microscope analysis (HR-SEM), phase analysis and functional group analysis were carried out confirming the semi-crystalline PAni nanofibrils braided on the ATZ surface. Potentiodynamic polarization studies of the coated sample exhibited higher Ecorr (−0.060 V) and lower icorr (0.007 µA/cm2) values signifying its better corrosion resistance behaviour in higher potentials coupled with lower electrochemical activity in the SBF medium. The porosity of PAni/ATZ nanofibril was 0.007 % and it provides an effective platform for implant-tissue attachment. The In-vitro biomineralization studies proved the bioactivity of PAni/ATZ which forms well-matured HAp spherules over the surface. Further, hemocompatibility studies of PAni/ATZ expressed a hemolytic rate of ∼0.39 % which denotes it’s biocompatible and non-hemolytic behaviour with the blood cells. Further, the coated sample on gram-positive and gram-negative bacteria causes demise of bacterial cell wall and exhibits higher inhibition percentage. In addition, a standard MTT assay of PAni/ATZ provides an effective support in maintaining cell viability and aids in proliferation of MG-63 cells. Thus, the results demonstrate that the nanoscale surface architecture of PAni/ATZ could serve as a potential and conducive environment for bone-implant interaction on the implant material for better osseointegration.

Investigating the Antibacterial Effect of a Novel Gallic Acid-Based Green Sanitizer Formulation.

The purpose of the present study was to investigate the mechanism of action of our newly developed green sanitizer formulation comprising a natural phenolic compound, gallic acid (GA), strengthened by the Generally Recognized as Safe (GRAS) materials hydrogen peroxide (H2O2) and DL-lactic acid (LA). Combining 8 mM GA with 1 mM H2O2 resulted in an abundant generation of reactive oxygen species (ROS) and a bactericidal effect towards Gram-negative (Escherichia coli, Pseudomonas syringae, and Pectobacterium brasiliense) and Gram-positive (Bacillus subtilis) bacteria (4 to 8 log CFU mL-1 reduction). However, the exposure to this dual formulation (DF) caused only a modest 0.7 log CFU mL-1 reduction in the Gram-positive L. innocua population. Amending the DF with 20 mM LA to yield a triple formulation (TF) resulted in the efficient synergistic control of L. innocua proliferation without increasing ROS production. Despite the inability to grow on plates (>7 log CFU mL-1 population reduction), the TF-exposed L. innocua maintained high intracellular ATP pools and stable membrane integrity. The response of L. innocua to TF could be qualified as a "viable but nonculturable" (VBNC) phenomenon, while with the other species tested this formulation caused cell death. This research system may offer a platform for exploring the VBNC phenomenon, a critical food safety topic.

The impact of the COVID-19 pandemic on pediatric bloodstream infections and alteration in antimicrobial resistance phenotypes in Gram-positive bacteria, 2020–2022

BackgroundAlteration in the etiology of pediatric bloodstream infections (BSIs) and antimicrobial resistance (AMR) is not well known during the Coronavirus disease 2019 (COVID-19) pandemic. This study aimed to investigate the impact of the COVID-19 pandemic on pediatric BSIs and alteration in antimicrobial resistance phenotypes in Gram-positive bacteria.MethodsThe frequency of BSIs among children under 18 years old was retrospectively recorded in a tertiary children’s hospital in Tehran, Iran from February 2020 to December 2022. The status of COVID-19 infection using reverse transcription polymerase chain reaction, bacteremia/fungemia according to BACTEC 9120 Culture System results, characterization of bacteria using biochemical tests, and antimicrobial susceptibility patterns for Gram-positive bacterial isolates using disk diffusion method were determined. Statistical analysis was done to measure the correlation of COVID-19 infection with BSIs and AMR.ResultsOut of 13,345 COVID-19 tests and 4,194 BACTEC blood culture requests, bacteremia/fungemia were confirmed in 10.37% (435/4,194) of the patients who requested both tests simultaneously. The COVID-19 infection was confirmed in 25.3% (110/435) of the patients with bacteremia/fungemia. The infection with characterized Gram-positive bacteria (GPB) and fungi was detected in 32.3% (140/433) and 8.31% (36/433) of the cases, respectively. Coagulase-negative Staphylococcus (CNS, 72, 16.62%), S. aureus (36, 8.3%), and Enterococcus spp. (22, 5%) were among the common isolates. Candida spp. and non-Candida yeasts were detected in 6.7% and 13.4% of the cases, respectively. A positive correlation was shown between the CNS bacteremia and COVID-19 infection (p-value = 0.019). Antibiotic susceptibility testing results showed the highest frequency of resistance to azithromycin among CNS, azithromycin and tetracycline among S. aureus and tetracycline among Enterococcus spp. Methicillin-resistance phenotype in the S. aureus (MRSA) and coagulase-negative Staphylococcus spp. (MR-CNS) was detected in 40% and 61.5% of the strains, respectively and the Enterococci were resistant to vancomycin in 33.3% of the isolates.ConclusionA decline in the trend of BSIs by GPB and an increase in AMR was shown in children during the COVID-19 pandemic. Increasing antibiotic resistance is a concern; however, chloramphenicol, linezolid, and vancomycin remain active against common causes of GPB-BSIs.