Human Bacterial Pathogens Research Articles

Streptococcus pneumoniae extracellular vesicles aggravate alveolar epithelial barrier disruption via autophagic degradation of OCLN (occludin)

ABSTRACT Streptococcus pneumoniae (S. pneumoniae) represents a major human bacterial pathogen leading to high morbidity and mortality in children and the elderly. Recent research emphasizes the role of extracellular vesicles (EVs) in bacterial pathogenicity. However, the contribution of S. pneumoniae EVs (pEVs) to host-microbe interactions has remained unclear. Here, we observed that S. pneumoniae infections in mice led to severe lung injuries and alveolar epithelial barrier (AEB) dysfunction. Infections of S. pneumoniae reduced the protein expression of tight junction protein OCLN (occludin) and activated macroautophagy/autophagy in lung tissues of mice and A549 cells. Mechanically, S. pneumoniae induced autophagosomal degradation of OCLN leading to AEB impairment in the A549 monolayer. S. pneumoniae released the pEVs that could be internalized by alveolar epithelial cells. Through proteomics, we profiled the cargo proteins inside pEVs and found that these pEVs contained many virulence factors, among which we identified a eukaryotic-like serine-threonine kinase protein StkP. The internalized StkP could induce the phosphorylation of BECN1 (beclin 1) at Ser93 and Ser96 sites, initiating autophagy and resulting in autophagy-dependent OCLN degradation and AEB dysfunction. Finally, the deletion of stkP in S. pneumoniae completely protected infected mice from death, significantly alleviated OCLN degradation in vivo, and largely abolished the AEB disruption caused by pEVs in vitro. Overall, our results suggested that pEVs played a crucial role in the spread of S. pneumoniae virulence factors. The cargo protein StkP in pEVs could communicate with host target proteins and even hijack the BECN1 autophagy initiation pathway, contributing to AEB disruption and bacterial pathogenicity. Abbreviations: AEB: alveolarepithelial barrier; AECs: alveolar epithelial cells; ATG16L1: autophagy related 16 like 1; ATP:adenosine 5’-triphosphate; BafA1: bafilomycin A1; BBB: blood-brain barrier; CFU: colony-forming unit; co-IP: co-immunoprecipitation; CQ:chloroquine; CTRL: control; DiO: 3,3′-dioctadecylox-acarbocyanineperchlorate; DOX: doxycycline; DTT: dithiothreitol; ECIS: electricalcell-substrate impedance sensing; eGFP: enhanced green fluorescentprotein; ermR: erythromycin-resistance expression cassette; Ery: erythromycin; eSTKs: eukaryotic-like serine-threoninekinases; EVs: extracellular vesicles; HA: hemagglutinin; H&E: hematoxylin and eosin; HsLC3B: human LC3B; hpi: hours post-infection; IP: immunoprecipitation; KD: knockdown; KO: knockout; LAMP1: lysosomal associated membrane protein 1; LC/MS: liquid chromatography-mass spectrometry; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MVs: membranevesicles; NC:negative control; NETs:neutrophil extracellular traps; OD: optical density; OMVs: outer membrane vesicles; PBS: phosphate-buffered saline; pEVs: S.pneumoniaeextracellular vesicles; protK: proteinase K; Rapa: rapamycin; RNAi: RNA interference; S.aureus: Staphylococcusaureus; SNF:supernatant fluid; sgRNA: single guide RNA; S.pneumoniae: Streptococcuspneumoniae; S.suis: Streptococcussuis; TEER: trans-epithelium electrical resistance; moi: multiplicity ofinfection; TEM:transmission electron microscope; TJproteins: tight junction proteins; TJP1/ZO-1: tight junction protein1; TSA: tryptic soy agar; WB: western blot; WT: wild-type

The emergence of highly resistant and hypervirulent Klebsiella pneumoniae CC14 clone in a tertiary hospital over 8 years

BackgroundKlebsiella pneumoniae is a major bacterial and opportunistic human pathogen, increasingly recognized as a healthcare burden globally. The convergence of resistance and virulence in K. pneumoniae strains has led to the formation of hypervirulent and multidrug-resistant strains with dual risk, limiting treatment options. K. pneumoniae clones are known to emerge locally and spread globally. Therefore, an understanding of the dynamics and evolution of the emerging strains in hospitals is warranted to prevent future outbreaks.MethodsIn this study, we conducted an in-depth genomic analysis on a large-scale collection of 328 multidrug-resistant (MDR) K. pneumoniae strains recovered from 239 patients from a single major hospital in the western coastal city of Jeddah in Saudi Arabia from 2014 through 2022. We employed a broad range of phylogenetic and phylodynamic methods to understand the evolution of the predominant clones on epidemiological time scales, virulence and resistance determinants, and their dynamics. We also integrated the genomic data with detailed electronic health record (EHR) data for the patients to understand the clinical implications of the resistance and virulence of different strains.ResultsWe discovered a diverse population underlying the infections, with most strains belonging to Clonal Complex 14 (CC14) exhibiting dominance. Specifically, we observed the emergence and continuous expansion of strains belonging to the dominant ST2096 in the CC14 clade across hospital wards in recent years. These strains acquired resistance mutations against colistin and extended spectrum β-lactamase (ESBL) and carbapenemase genes, namely blaOXA-48 and blaOXA-232, located on three distinct plasmids, on epidemiological time scales. Strains of ST2096 exhibited a high virulence level with the presence of the siderophore aerobactin (iuc) locus situated on the same mosaic plasmid as the ESBL gene. Integration of ST2096 with EHR data confirmed the significant link between colonization by ST2096 and the diagnosis of sepsis and elevated in-hospital mortality (p-value < 0.05).ConclusionsOverall, these results demonstrate the clinical significance of ST2096 clones and illustrate the rapid evolution of an emerging hypervirulent and MDR K. pneumoniae in a clinical setting.

Antibiofilm Efficacy and Mode of Action of Etlingera elatior Extracts Against Staphylococcus aureus

Staphylococcus aureus represents a major bacterial human pathogen that causes a wide variety of clinical manifestations. Various medicinal plants have been used to control its infection, however, the effect of Etlingera elatior on S. aureus biofilm is still uncertain. Thus, the objective of this study was to evaluate the antibacterial and antibiofilm efficacy of E. elatior extracts against S. aureus. Phytochemical screening was carried out to determine the presence of phenols, tannins, saponins, and alkaloids in different extracts (acetone, methanol, ethanol, and aqueous) of E. elatior. Antibacterial activities were determined by disk diffusion assay, minimum inhibitory concentration assay (MIC), and minimum bactericidal concentration assay (MBC) while antibiofilm activities were determined by crystal violet assay and Fourier-transform infrared (FTIR) spectroscopy. All the extracts were found to contain phenols, tannins, saponins, and alkaloids. Only acetone extract showed a high amount of saponins. Among all the extracts, acetone extract showed the widest inhibition zone (21.23±0.2 mm), lowest MIC (20 mg/mL), and lowest MBC (50 mg/mL) values. The acetone extract also showed the highest antibiofilm activities at all biofilm stages (6 hr: 12%-31%; 12 hr: 20%-36%; 18 hr: 27%-32%; 24 hr: 5%-46%). Further analysis with FTIR spectroscopy revealed spectral changes associated with proteins (1700–1400 cm-1), phospholipids, and polysaccharides (1300–700 cm-1) in S. aureus biofilm following the treatment with 200 mg/mL of E. elatior extracts. In conclusion, E. elatior is a potential source of antibacterial and antibiofilm agents to control S. aureus infections. Changes in the composition of proteins, phospholipids, and polysaccharides may mediate the biofilm inhibition by E. elatior extracts. The acetone extract of E. elatior may be useful for various applications such as antimicrobial topical cream and wound dressing.

Antibacterial Activity of the Leaf Extract of Acalypha wilkesiana against some Human Bacterial Pathogens

Humanity has long been creating traditional treatments based on the knowledge of medicinal plants found worldwide. The medicinal potential of Acalypha wilkesiana in treating skin and gastrointestinal problems is highly appreciated. This study aimed to examine the Acalypha wilkesiana leaf extract's antibacterial effectiveness against a variety of human bacterial infections. Standard techniques were used to determine whether secondary metabolites were present in methanolic, ethanolic, and hot water extracts. The plant extracts were evaluated for their ability to inhibit the growth of bacteria obtained from Bells University of Technology, including Staphylococcus aureus, Staphylococcus saprophyticus, Enterococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa. Agar diffusion was used for antibacterial activities, and Mueller Hinton Agar (MHA) minimum inhibitory concentration (MIC) was determined using the agar dilution method. According to the study's findings, the plant sample included flavonoids, tannin, alkaloids, and saponins. With a MIC of 2.5 mg/mL against Pseudomonas aeruginosa and Enterococcus faecalis and 5.0 mg/mL against Staphylococcus aureus, hot water extract exhibited the highest activity level against all tested isolates. As a result, Acalypha wilkesiana leaf extract exhibited broad-spectrum antibacterial activity.

Diagnostic Approaches to Helicobacter pylori: A Comparative Study of Detection in Gastric Biopsy and Aspirates.

Background Helicobacter pyloriis one of the most common bacterial pathogens in humans. It is a microaerophilic bacteria with multiple unipolar flagella. It is associated with the development of various lesions like chronic gastritis, gastric ulcers, adenocarcinoma, and mucosa-associated lymphomas. The aim of this study was a comparative evaluation of the rapid urease test (RUT) and polymerase chain reaction (PCR) in gastric biopsy and aspirates for the detection ofH. pyloriinfection and to further determine the sensitivity and specificity of RUT and PCR. Method Endoscopic guided biopsy tissue and gastric aspirate specimens were collected from 110 patients with symptoms like gastritis, dyspepsia, etc., and subjected to RUT and PCR for detection ofH. pyloriinfection. Results A total of 110 samples, including both biopsy tissue (77) and gastric aspirate (33) were subjected to RUT and PCR. RUT for biopsy tissue showed the highest sensitivity (97.18%), compared to gastric aspirate (78.94%). Comparing RUT with PCR, the sensitivity and specificity of PCR were 93.33% and 90.0%, respectively. The positive predictive value (PPV) of PCR was 97.67%, the negative predictive value (NPV) was 75.0%, and the accuracy was 92.73%. Conclusion The present study showed that RUT is a rapid and accurate invasive test for the detection ofHelicobacter pyloriinfection in biopsy tissue as compared to gastric aspirate specimens, which are more sensitive to PCR. The study also showed that biopsy tissue was found to be a superior specimen for the detection ofHelicobacter pylorias compared to gastric aspirate.

Green Synthesis of Cobalt Oxide Nanoparticles with In-vitro Cytotoxicity Assessment Using Pomegranate (Punica granatum L.) Seed Oil: A Promising Approach for Antimicrobial and Anticancer Applications

Green synthesis of nanoparticles and their pharmacological implementation have gained importance in the field of nanotechnology. This study primarily aims to explore the use of Punica granatum L. seed oil as a reducing agent for the synthesis of cobalt nanoparticles, making it both economically and pharmacologically valuable. Gas chromatography-mass spectroscopy analysis was carried out to study the active metabolites present in P. granatum seed oil. The green synthesis of cobalt nanoparticles was established based on the color change of the reaction mixture from dark green to light green. These particles showed a ?max at 279.88 nm for UV-visible spectrometry analysis. Furthermore, X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscope (FE SEM) and Dynamic Light Scattering (DLS) were performed to confirm the nature of these nanoparticles. The pharmacological potential of these cobalt oxide nanoparticles was tested against microbial pathogens. The results suggest that these nanoparticles exhibited significant activity against various human bacterial and fungal pathogens. Additionally, in in vitro cytotoxicity analysis, demonstrated that CoONPs selectively targeted MCF-7 cancer cells with a significant IC50 value compared to non-cancerous cells (L929). In conclusion, this study demonstrated that green synthesized CoONPs using P. granatum show significant potential against eukaryotic cancer cells and microbial pathogens. Furthermore, this study has implications for medical research centers and pharmaceutical industries in addressing modern challenges such as increasing antibiotic resistance in communities.

Site properties, environmental factors, and crop identify influence soil bacterial communities more than municipal biosolid application

Reducing the environmental impact of Canadian field crop agriculture, including the reliance on conventional synthesised fertilisers, are key societal targets for establishing long-term sustainable practices. Municipal biosolids (MSB) are an abundant, residual organic material, rich in phosphate, nitrogen and other oligo-nutrients, that could be used in conjunction with conventional fertilisers to decrease their use. Though MBS have previously been shown to be an effective fertiliser substitute for different crops, including corn and soybean, there remain key knowledge gaps concerning the impact of MBS on the resident soil bacterial communities in agro-ecosystems. We hypothesised that the MBS fertiliser amendment would not significantly impact the structure or function of the soil bacterial communities, nor contribute to the spread of human pathogenic bacteria, in corn or soybean agricultural systems. In field experiments, fertiliser regimes for both crops were amended with MBS, and compared to corn and soybean plots with standard fertiliser treatments. We repeated this across four different agricultural sites in Quebec, over 2021 and 2022. We sampled MBS-treated, and untreated soils, and identified the composition of the soil bacterial communities via 16S rRNA metabarcoding. We found no indication that the MBS fertiliser amendment altered the structure of the soil bacterial communities, but rather that the soil type and crop identities were the most significant factors in structuring the bacterial communities. Moreover, there was no evidence that the MBS-treated soils were enriched in potential human bacterial pathogens over the two years of our study. Our analysis indicates that not only can MBS function as substitutes for conventional, synthesised fertilisers, but that they also do not disrupt the structure of the resident soil bacterial communities in the short term. Finally, we suggest that the use of MBS in agro-ecosystems poses no greater concern to the public than existing soil bacterial communities. This highlights the significant role MBS could potentially have in reducing the use of conventional industrial fertilisers and improving agricultural production, without risking environmental contamination.

Morinda citrifolia leaf assisted synthesis of ZnO decorated Ag bio-nanocomposites for in-vitro cytotoxicity, antimicrobial and anticancer applications.

This study used Morinda citrifolia leaf (MCL) extract to synthesise Zinc oxide nanoparticles (ZnO NPs) and ZnO decorated silver nanocomposites (ZnO/Ag NCs). The synthesized nanomaterials structural morphology and crystallinity were characterized using a Field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) analysis. The antimicrobial activity of ZnO NPs and ZnO/Ag NCs was evaluated using human nosocomial bacterial pathogens. The highest antimicrobial activity was recorded for ZnO/Ag NCs at the minimum inhibitory concentration (MIC) at 80 and 100μg/mL for Escherichia coli, Pseudomonas aeruginosa and Bacillus subtilis, Staphylococcus aureus than ZnO NPs at the MIC of 120 and 140μg/mL for Bacillus subtilis and Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus. Furthermore, ROS detection, viability assay and bacterial membrane integrity analysis of ZnO/Ag NCs treated P. aeruginosa and S. aureus revealed the fundamental bactericidal mechanism involving cell wall, cell membrane interaction and release of cytoplasmic contents. In addition, ZnO/Ag NCs and ZnO NPs showed higher toxicity towards A549 lung cancer cells than the non-cancerous RAW264 macrophage cells, with IC50 of 242 and 398µg/mL respectively, compared to IC50 of 402 and 494µg/mL for the macrophage cells. These results suggest that the ZnO/Ag NCs can be effectively used to develop antimicrobial and anticancer materials.

Estimating between-country migration in pneumococcal populations.

Streptococcus pneumoniae (the pneumococcus) is a globally distributed, human obligate opportunistic bacterial pathogen which, although often carried commensally, is also a significant cause of invasive disease. Apart from multi-drug resistant and virulent clones, the rate and direction of pneumococcal dissemination between different countries remains largely unknown. The ability for the pneumococcus to take a foothold in a country depends on existing population configuration, the extent of vaccine implementation, as well as human mobility since it is a human obligate bacterium. To shed light on its international movement, we used extensive genome data from the Global Pneumococcal Sequencing project and estimated migration parameters between multiple countries in Africa. Data on allele frequencies of polymorphisms at housekeeping-like loci for multiple different lineages circulating in the populations of South Africa, Malawi, Kenya, and The Gambia were used to calculate the fixation index (Fst) between countries. We then further used these summaries to fit migration coalescent models with the likelihood-free inference algorithms available in the ELFI software package. Synthetic datawere additionally used to validate the inference approach. Our results demonstrate country-pair specific migration patterns and heterogeneity in the extent of migration between different lineages. Our approach demonstrates that coalescent models can be effectively used for inferring migration rates for bacterial species and lineages provided sufficiently granular population genomics surveillance data. Further, it can demonstrate the connectivity of respiratory disease agents between countries to inform intervention policy in the longer term.

Aristolochia bracteolata flower extract based phytosynthesis and characterization of AgNPs: Antimicrobial, antidiabetic, and antioxidant activities potential assessment

The study was carried out to evaluate the effectiveness of the Aristolochia bracteolata water flower extract-mediated AgNPs synthesis and assess their antimicrobial potential. According to the experimental and analytical results, A. bracteolata flower extract can produce valuable AgNPs. The characteristic features of these AgNPs were assessed with UV–visible spectrophotometer, Fourier transform-infrared spectroscopy, Transmission Electron Microscope, Scanning Electron Microscopy, as well as. Under UV–vis. spectrum results, showed major peak at 430 nm and recorded essential functional groups responsible for reducing, capping, and stabilizing AgNPs by FT-IR analysis. In addition, the size and shape of the synthesized AgNPs were found as 21.11–25.17 nm and spherical/octahedral shape. The A. bracteolata fabricated NPs showed remarkable antimicrobial activity against fish bacterial pathogens (V. parahaemolytics, Serratia sp., B. subtilis, and E. coli) as well as common fungal pathogens (A. niger, C. albicans, A. flavus, and A. terreus) at the quantity of 100 μg mL−1 than positive controls. Nevertheless, it was not effective against human bacterial pathogens. It concludes that AgNPs synthesized from A. bracteolata aqueous flower extract have excellent antimicrobial activity and may have a variety of biomedical applications.

Functional characterization and transcriptional analysis of degQ of Xanthomonas campestris pathovar campestris.

High-temperature-requirement protein A (HtrA) family proteins play important roles in controlling protein quality and are recognized as virulence factors in numerous animal and human bacterial pathogens. The role of HtrA family proteins in plant pathogens remains largely unexplored. Here, we investigated the HtrA family protein, DegQ, in the crucifer black rot pathogen Xanthomonas campestris pathovar campestris (Xcc). DegQ is essential for bacterial attachment and full virulence of Xcc. Moreover, the degQ mutant strain showed increased sensitivity to heat treatment and sodium dodecyl sulfate. Expressing the intact degQ gene in trans in the degQ mutant could reverse the observed phenotypic changes. In addition, we demonstrated that the DegQ protein exhibited chaperone-like activity. Transcriptional analysis displayed that degQ expression was induced under heat treatment. Our results contribute to understanding the function and expression of DegQ of Xcc for the first time and provide a novel perspective about HtrA family proteins in plant pathogen.

Leveraging Plasma-Activated Seawater for the Control of Human Norovirus and Bacterial Pathogens in Shellfish Depuration.

Cold plasma is a promising alternative for water treatment owing to pathogen control and a plethora of issues in the agriculture and food sectors. Shellfish pose a serious risk to public health and are linked to large viral and bacterial outbreaks. Hence, current European regulations mandate a depuration step for shellfish on the basis of their geographical growth area. This study investigated the inactivation of relevant viral and bacterial pathogens of three plasma-activated seawaters (PASWs), and their reactive oxygen and nitrogen species (RONS) composition, as being primarily responsible for microbial inactivation. Specifically, F-specific (MS2) and somatic (φ174) bacteriophage, cultivable surrogate (murine norovirus, MNV, and Tulane virus, TV), and human norovirus (HuNoV GII.4) inactivation was determined using plaque counts and infectivity assays, including the novel human intestinal enteroid (HIE) model for HuNoV. Moreover, the kinetic decay of Escherichia coli, Salmonella spp., and Vibrio parahaemolyticus was characterized. The results showed the complete inactivation of phages (6-8 log), surrogates (5-6 log), HuNoV (6 log), and bacterial (6-7 log) pathogens within 24 h while preventing cytotoxicity effects and preserving mussel viability. Nitrites (NO2-) were found to be mostly correlated with microbial decay. This research shows that PASWs are a suitable option to depurate bivalve mollusks and control the biohazard risk linked to their microbiological contamination, either viral or bacterial.

Structural determination and kinetic analysis of the transketolase from Vibrio vulnificus reveal unexpected cooperative behavior.

Vibrio vulnificus (vv) is a multidrug-resistant human bacterial pathogen whose prevalence is expected to increase over the years. Transketolases (TK), transferases catalyzing two reactions of the nonoxidative branch of the pentose-phosphate pathway and therefore linked to several crucial metabolic pathways, are potential targets for new drugs against this pathogen. Here, the vvTK is crystallized and its structure is solved at 2.1 Å. A crown of 6 histidyl residues is observed in the active site and expected to participate in the thiamine pyrophosphate (cofactor) activation. Docking of fructose-6-phosphate and ferricyanide used in the activity assay, suggests that both substrates can bind vvTK simultaneously. This is confirmed by steady-state kinetics showing a sequential mechanism, on the contrary to the natural transferase reaction which follows a substituted mechanism. Inhibition by the I38-49 inhibitor (2-(4-ethoxyphenyl)-1-(pyrimidin-2-yl)-1H-pyrrolo[2,3-b]pyridine) reveals for the first time a cooperative behavior of a TK and docking experiments suggest a previously undescribed binding site at the interface between the pyrophosphate and pyridinium domains.

Evaluation of in-vitro antibacterial activity of extracts of Calpurina aurea, Vernonia amygdalina and Rumex nepalensis in Goba district, southeastern Ethiopia

ABSTRACT The great majority of the rural populations in developing countries relies on traditional medicinal plants for treating different diseases. This study investigated the antibacterial activity of Calpurnia aurea, Vernonia amygdalina, and Rumex nepalensis collected from Goba District, Bale Zone, southeastern Ethiopia against five human bacterial test pathogens (Escherichia coli, Salmonella typhi, Staphylococcus aureus, Shigella dysenteriae and Pseudomonas aeruginosa). Plant specimens were extracted with 70% ethanol, 80% methanol, petroleum ether, and distilled water. The crude extracts were evaluated against test pathogens using agar well diffusion and micro dilution methods. The highest yield was achieved by aqueous extract of C. aurea leaf (16.6 mg/ml). The antibacterial activity of the plants’ extracts ranged from a zone of inhibition of 5.4 ± 0.4 mm to 23.0 ± 0.3 mm. Overall, the highest zone of inhibition (23 ± 0.3 mm) and the highest activity index (AI) comparable to 80% of inhibition by standard antibiotic ciprofloxacin (5 µg/disc) were revealed by the methanol extract of C. aurea leaves against S. aureus. The smallest minimum inhibitory concentration (0.78 mg/ml) was achieved by 80% methanol extracts of C. aurea roots and V. amygdalina leaves against S. aureus and E. coli, respectively. Our study revealed promising antibacterial activity of the evaluated plants.. Further studies are required to evaluate the active ingredients at the in-vitro and in-vivo levels.

The intracellular growth of the vacuolar pathogen Legionella pneumophila is dependent on the acyl chain composition of host membranes

Legionella pneumophila is an accidental human bacterial pathogen that infects and replicates within alveolar macrophages causing a severe atypical pneumonia known as Legionnaires’ disease. As a prototypical vacuolar pathogen L. pneumophila establishes a unique endoplasmic reticulum (ER)-derived organelle within which bacterial replication takes place. Bacteria-derived proteins are deposited in the host cytosol and in the lumen of the pathogen-occupied vacuole via a type IVb (T4bSS) and a type II (T2SS) secretion system respectively. These secretion system effector proteins manipulate multiple host functions to facilitate intracellular survival of the bacteria. Subversion of host membrane glycerophospholipids (GPLs) by the internalized bacteria via distinct mechanisms feature prominently in trafficking and biogenesis of the Legionella-containing vacuole (LCV). Conventional GPLs composed of a glycerol backbone linked to a polar headgroup and esterified with two fatty acids constitute the bulk of membrane lipids in eukaryotic cells. The acyl chain composition of GPLs dictates phase separation of the lipid bilayer and therefore determines the physiochemical properties of biological membranes - such as membrane disorder, fluidity and permeability. In mammalian cells, fatty acids esterified in membrane GPLs are sourced endogenously from de novo synthesis or via internalization from the exogenous pool of lipids present in serum and other interstitial fluids. Here, we exploited the preferential utilization of exogenous fatty acids for GPL synthesis by macrophages to reprogram the acyl chain composition of host membranes and investigated its impact on LCV homeostasis and L. pneumophila intracellular replication. Using saturated fatty acids as well as cis- and trans- isomers of monounsaturated fatty acids we discovered that under conditions promoting lipid packing and membrane rigidification L. pneumophila intracellular replication was significantly reduced. Palmitoleic acid – a C16:1 monounsaturated fatty acid – that promotes membrane disorder when enriched in GPLs significantly increased bacterial replication within human and murine macrophages but not in axenic growth assays. Lipidome analysis of infected macrophages showed that treatment with exogenous palmitoleic acid resulted in membrane acyl chain reprogramming in a manner that promotes membrane disorder and live-cell imaging revealed that the consequences of increasing membrane disorder impinge on several LCV homeostasis parameters. Collectively, we provide experimental evidence that L. pneumophila replication within its intracellular niche is a function of the lipid bilayer disorder and hydrophobic thickness.

Comparative phytochemical analysis and antimicrobial activity of methanol extracts of Hairy roots and wild roots from Aerva javanica (Burm.f) Juss. ex Schult against selected pathogenic microorganisms

Transformed root culture in Aerva javanica was investigated for amassing of alkaloids. Leaves of A. javanica were used as establishing material for induction of hairy roots via the Agrobacterium rhizogenes A4 strain. Three hairy root lines from leaf explants upon growth kinetics were attained. Maceration method was used for preparation of different extracts viz. chloroform, petroleum ether, ethyl acetate, acetone and methanol. The extracts were examined against human bacterial pathogens by agar well diffusion method. According to our results, methanol extracts of hairy roots showed a significant antimicrobial activity against the tested pathogens particularly Pseudomonas aerogenes (19.29 ± 0.23mm) followed by Bacillus subtilis (18.49 ± 0.43mm) and Staphylococcus epidermidis (18.49 ± 0.68mm) rather than wild root extract. Methanol extracts of hairy root sample inhibited pathogen development better than other extracts and also than wild root extracts. Phytochemical analysis exhibited the presence of alkaloids, flavonoids, steroids, tannins, sugars and glycosides found only in methanol extract of A. javanica hairy roots. The results revealed that methanol extract of A. javanica hairy roots has potential activity than the other extracts as well as standard drugs (Spreptomycin). Further studies are needed related to pharmacological activities.

Biomimetic synthesis of Ag@Fe bimetallic nanoparticles from Palmyra sprouts extract and their antibacterial, photocatalytic degradation of malachite green

The present study aimed to biomimetic synthesis of silver-iron bimetallic nanoparticles (Ag@Fe BMNPs) was achieved by bio-reduction of silver nitrate (AgNO3) and Ferric(III) nitrate Fe(NO3)3 using Palmyra sprout (PS) extract. The synthesized PS-Ag@Fe BMNPs were characterized by UV–Visible spectrophotometer, Fourier-transform infrared (FT-IR) spectroscopy, High-resolution scanning electron microscope (HR-TEM), Field-emission scanning electron microscope (FE-SEM), vibrating sample magnetometer (VSM), and X-ray diffraction (XRD), respectively. The UV–Vis spectra of PS-Ag@Fe BMNPs showed a broad absorption peak at 310 nm and FT-IR represented bioactive functional groups. The results of the XRD pattern confirmed the crystalline nature of PS-Ag@Fe BMNPs. HR-TEM and FE-SEM results prove the spherical shape of PS-Ag@Fe BMNPs and the presence of Ag and Fe peaks at 3.0, 6.4, and 7.2 keV, respectively. The photocatalytic efficiency of PS-Ag@Fe BMNPs against malachite green (MG) showed 91.23 % decolorization within 180 min of direct sunlight irradiation. In addition, antibacterial properties of PS-Ag@Fe BMNPs against human bacterial pathogens was evaluated. Hence, the green synthesized PS-Ag@Fe BMNPs were confirmed to be a potential substance for biomedical and environmental remediation.

The antibacterial activity and mechanism of a novel peptide MR-22 against multidrug-resistant Escherichia coli.

Bacterial infections have become serious threats to human health, and the excessive use of antibiotics has led to the emergence of multidrug-resistant (MDR) bacteria. E. coli is a human bacterial pathogen, which can cause severe infectious. Antimicrobial peptides are considered the most promising alternative to traditional antibiotics. The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and hemolytic activity were determined by the microdilution method. The antimicrobial kinetics of MR-22 against E. coli were studied by growth curves and time-killing curves. The cytotoxicity of MR-22 was detected by the CCK-8 assay. The antimicrobial activity of MR-22 in salt, serum, heat and trypsin was determined by the microdilution method. The antimicrobial mechanism of MR-22 against drug-resistant E. coli was studied by Scanning Electron Microscope, laser confocal microscopy, and Flow Cytometry. The in vivo antibacterial activity of MR-22 was evaluated by the mice model of peritonitis. In this study, MR-22 is a new antimicrobial peptide with good activity that has demonstrated against MDR E. coli. The antimicrobial activity of MR-22 exhibited stability under conditions of high temperature, 10% FBS, and Ca2+. However, a decline of the activity was observed in the presence of Na+, serum, and trypsin. MR-22 had no significant cytotoxicity or hemolysis in vitro. SEM and fluorescent images revealed that MR-22 could disrupt the integrity of cell membrane. DCFH-DA indicated that MR-22 increased the content of reactive oxygen species, while it decreased the content of intracellular ATP. In mice model of peritonitis, MR-22 exhibited potent antibacterial activity in vivo. These results indicated that MR-22 is a potential drug candidate against drug-resistant E. coli.

NO3− as an electron acceptor elevates antibiotic resistance gene and human bacterial pathogen risks in managed aquifer recharge (MAR): A comparison with O2

Managed aquifer recharge (MAR) stands out as a promising strategy for ensuring water resource sustainability. This study delves into the comparative impact of nitrate (NO3−) and oxygen (O2) as electron acceptors in MAR on water quality and safety. Notably, NO3−, acting as an electron acceptor, has the potential to enrich denitrifying bacteria, serving as hosts for antibiotic resistance genes (ARGs) and enriching human bacterial pathogens (HBPs) compared to O2. However, a direct comparison between NO3− and O2 remains unexplored. This study assessed risks in MAR effluent induced by NO3− and O2, alongside the presence of the typical refractory antibiotic sulfamethoxazole. Key findings reveal that NO3− as an electron acceptor resulted in a 2 times reduction in dissolved organic carbon content compared to O2, primarily due to a decrease in soluble microbial product production. Furthermore, NO3− significantly enriched denitrifying bacteria, the primary hosts of major ARGs, by 747%, resulting in a 66% increase in the overall abundance of ARGs in the effluent of NO3− MAR compared to O2. This escalation was predominantly attributed to horizontal gene transfer mechanisms, as evidenced by a notable 78% increase in the relative abundance of mobile ARGs, alongside a minor 27% rise in chromosomal ARGs. Additionally, the numerous denitrifying bacteria enriched under NO3− influence also belong to the HBP category, resulting in a significant 114% increase in the abundance of all HBPs. The co-occurrence of ARGs and HBPs was also observed to intensify under NO3− influence. Thus, NO3− as an electron acceptor in MAR elevates ARG and HBP risks compared to O2, potentially compromising groundwater quality and safety.

Distribution of antibiotic resistance genes and their pathogen hosts in duck farm environments in south-east coastal China

Livestock farms are major reservoirs of antibiotic resistance genes (ARGs) that are discharged into the environment. However, the abundance, diversity, and transmission of ARGs in duck farms and its impact on surrounding environments remain to be further explored. Therefore, the characteristics of ARGs and their bacterial hosts from duck farms and surrounding environment were investigated by using metagenomic sequencing. Eighteen ARG types which consist of 823 subtypes were identified and the majority conferred resistance to multidrug, tetracyclines, aminoglycosides, chloramphenicols, MLS, and sulfonamides. The floR gene was the most abundant subtype, followed by sul1, tetM, sul2, and tetL. ARG abundance in fecal sample was significantly higher than soil and water sample. Our results also lead to a hypothesis that Shandong province have been the most contaminated by ARGs from duck farm compared with other four provinces. PcoA results showed that the composition of ARG subtypes in water and soil samples was similar, but there were significant differences between water and feces samples. However, the composition of ARG subtypes were similar between samples from five provinces. Bacterial hosts of ARG subtypes were taxonomically assigned to eight phyla that were dominated by the Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria. In addition, some human bacterial pathogens could be enriched in duck feces, including Enterococcus faecium, Acinetobacter baumannii, and Staphylococcus aureus, and even serve as the carrier of ARGs. The combined results indicate that a comprehensive overview of the diversity and abundance of ARGs, and strong association between ARGs and bacterial community shift proposed, and benefit effective measures to improve safety of antibiotics use in livestock and poultry farming.Key points• ARG distribution was widespread in the duck farms and surroundings environment• ARG abundance on the duck farms was significantly higher than in soil and water• Human bacterial pathogens may serve as the vectors for ARGs