Pathogenic Gram-negative Bacteria Research Articles

The aryl hydrocarbon receptor and FOS mediate cytotoxicity induced by Acinetobacter baumannii

Acinetobacter baumannii is a pathogenic and multidrug-resistant Gram-negative bacterium that causes severe nosocomial infections. To better understand the mechanism of pathogenesis, we compare the proteomes of uninfected and infected human cells, revealing that transcription factor FOS is the host protein most strongly induced by A. baumannii infection. Pharmacological inhibition of FOS reduces the cytotoxicity of A. baumannii in cell-based models, and similar results are also observed in a mouse infection model. A. baumannii outer membrane vesicles (OMVs) are shown to activate the aryl hydrocarbon receptor (AHR) of host cells by inducing the host enzyme tryptophan-2,3-dioxygenase (TDO), producing the ligand kynurenine, which binds AHR. Following ligand binding, AHR is a direct transcriptional activator of the FOS gene. We propose that A. baumannii infection impacts the host tryptophan metabolism and promotes AHR- and FOS-mediated cytotoxicity of infected cells.

Glycoengineering with neuraminic acid analogs to label lipooligosaccharides and detect native sialyltransferase activity in gram-negative bacteria.

Lipooligosaccharides (LOS) are the most abundant cell surface glycoconjugates on the outer membrane of Gram-negative bacteria. They play important roles in host-microbe interactions. Certain Gram-negative pathogenic bacteria cap their LOS with the sialic acid, N-acetylneuraminic acid (Neu5Ac), to mimic host glycans that among others protects these bacteria from recognition by the hosts immune system. This process of molecular mimicry is not fully understood and remains under investigated. To explore the functional role of sialic acid-capped lipooligosaccharides (LOS) at the molecular level, it is important to have tools readily available for the detection and manipulation of both Neu5Ac on glycoconjugates and the involved sialyltransferases, preferably in live bacteria. We and others have shown that the native sialyltransferases of some Gram-negative bacteria can incorporate extracellular unnatural sialic acid nucleotides onto their LOS. We here report on the expanded use of native bacterial sialyltransferases to incorporate neuraminic acids analogs with a reporter group into the LOS of a variety of Gram-negative bacteria. We show that this approach offers a quick strategy to screen bacteria for the expression of functional sialyltransferases and the ability to use exogenous CMP-Neu5Ac to decorate their glycoconjugates. For selected bacteria we also show this strategy complements two other glycoengineering techniques, Metabolic Oligosaccharide Engineering (MOE) and Selective Exo-Enzymatic Labeling (SEEL), and that together they provide tools to modify, label, detect and visualize sialylation of bacterial LOS.

Synthesis and characterization of a zinc-triazole coordination complex with potent antimicrobial and anticancer properties

The synthesis, characterization, and biological appraisement of a novel coordination compound [Zn(C4N4H5O)2(H2O)2]Cl have been comprehensively studied. The compound was synthesized using N-(1H-1,2,4-triazol-3-yl) acetamide and ZnCl2·6H2O, yielding a product characterized by FT-IR, elemental analysis, thermogravimetric analysis (TGA), and single crystal X-ray diffraction. FT-IR spectra confirmed the successful coordination of the ligand to the zinc ion, with significant shifts in characteristic absorption bands such as CO (1685 cm⁻¹), CN (1624 cm⁻¹), and NH (3394 cm⁻¹). Single crystal X-ray diffraction analyses revealed that the complex crystallized in the monoclinic system with space group P21/c and forms six-membered chelate rings. The unit cell parameters were a = 6.0595(3) Å, b = 14.2956(7) Å, c = 9.4762(4) Å, and β = 93.275(4)°. Thermal analysis showed that the complex undergoes stepwise decomposition with significant mass losses at various temperature intervals, including an overall mass loss of 71.09 % between 200 °C and 885 °C. Molecular docking studies indicated strong interactions between the [Zn(C4N4H5O)2(H2O)2]Cl complex and the 6QF6 cancer-related protein antigen A4, with low binding energy values (-9.32 to -8.44 kcal/mol) suggesting high binding affinity and potential biological activity. In vitro antimicrobial screening against several pathogenic microorganisms, viz. both gram-positive and gram-negative bacteria, demonstrated that the [Zn(C4N4H5O)2(H2O)2]Cl complex exhibited superior antibacterial activity, with inhibition zone diameters of 15.3 ± 0.47 mm for Bacillus subtilis and 24.17±0.56 mm for Agrobacterium tumefaciens, compared to N-(1H-1,2,4-triazol-3-yl) acetamide alone and some standard antibiotics. These findings highlight the [Zn(C4N4H5O)2(H2O)2]Cl complex as a promising candidate for developing new antimicrobial and anticancer agents, providing a foundation for further research and potential therapeutic applications.

Bioemulsifier from sponge-associated bacteria reduces staphylococcal biofilm

Biofilm formation is a major health concern and studies have been pursued to find compounds able to prevent biofilm establishment and remove pre-existing biofilms. While biosurfactants (BS) have been well-known for possessing antibiofilm activities, bioemulsifiers (BE) are still scarcely explored for this purpose. The present study aimed to evaluate the bioemulsifying properties of cell-free supernatants produced by Bacillaceae and Vibrio strains isolated from marine sponges and investigate their antiadhesive and antibiofilm activities against different pathogenic Gram-positive and Gram-negative bacteria. The BE production by the marine strains was confirmed by the emulsion test, drop-collapsing, oil-displacement, cell hydrophobicity and hemolysis assays. Notably, Bacillus cereus 64BHI1101 displayed remarkable emulsifying activity and the ultrastructure analysis of its BE extract (BE64-1) revealed the presence of structures typically observed in macromolecules composed of polysaccharides and proteins. BE64-1 showed notable antiadhesive and antibiofilm activities against Staphylococcus aureus, with a reduction of adherence of up to 100 % and a dispersion of biofilm of 80 %, without affecting its growth. BE64-1 also showed inhibition of Staphylococcus epidermidis and Escherichia coli biofilm formation and adhesion. Thus, this study provides a starting point for exploring the antiadhesive and antibiofilm activities of BE from sponge-associated bacteria, which could serve as a valuable tool for future research to combat S. aureus biofilms.

Identification and Functional Analysis of ncRNAs Regulating Intrinsic Polymyxin Resistance in Foodborne Proteus vulgaris.

Polymyxin, known as the "last line of defense" against bacterial infection, exerts a significant inhibitory effect on a wide range of Gram-negative pathogenic bacteria. The presence of strains, specifically Proteus vulgaris species, displaying intrinsic polymyxin resistance poses significant challenges to current clinical treatment. However, the underlying mechanism responsible for this intrinsic resistance remains unclear. Bacterial non-coding RNAs (ncRNAs) are abundant in genomes and have been demonstrated to have significant regulatory roles in antibiotic resistance across various bacterial species. However, it remains to be determined whether ncRNAs in Proteus vulgaris can regulate intrinsic polymyxin resistance. This study focused on investigating the foodborne Proteus vulgaris strain P3M and its intrinsic polymyxin resistance regulation mediated by ncRNAs. Through a combination of bioinformatics analysis, mutant construction, and phenotypic experimental verification, we successfully identified the ncRNAs involved and their potential target genes. These findings serve as an essential foundation for the precise identification of ncRNAs participating in the intricate regulation process of polymyxin resistance. Additionally, this study offers valuable insights into the efficient screening of bacterial ncRNAs that contribute positively to antibiotic resistance regulation.

The effect of selenium on the intestinal health of juvenile grass carp based on the ERS-autophagy pathway

Selenium (Se), a trace element, is vital for the maintenance of cellular redox balance, thyroid hormone metabolism, inflammation, and immunity. Aeromonas hydrophila (A. hydrophila) is a common Gram-negative conditional pathogenic bacterium in fish culture, posing a serious threat to intensive aquaculture. Our study investigated the influence of dietary Se on the intestinal immune function of grass carp (Ctenopharyngodon idella) and the related regulatory mechanisms. The 2160 healthy juvenile grass carp (9.76 ± 0.005 g) were randomly assigned to 6 test groups of 6 replicates each, and fed graded selenomethionine (0.05, 0.20, 0.40, 0.61, 0.77, 0.98 mg Se/kg diet) for 70 days and then injected with A. hydrophila for a 6-day attack test. The results indicated that appropriate Se levels (0.40 mg/kg diet) alleviated intestinal damage caused by A. hydrophila and increased intestinal immune substances C3 and C4 levels as well as the activity of acid phosphatase (ACP) and lysozyme (LZ) (P > 0.05). Appropriate levels of Se (0.40 mg/kg-0.61 mg/kg diet) decreased intestinal pro-inflammatory cytokines (IFN-γ2, IL-6, IL-12p35, IL-17 A F and IL-17D) mRNA levels (P > 0.05) and increased intestinal anti-inflammatory factors (TGF-β1, IL-4/13A, IL-4/13B, IL-10 and IL-22) mRNA levels (P > 0.05) in juvenile grass carp. Further studies revealed that Se (0.40 mg/kg-0.61 mg/kg diet) inhibited intestinal endoplasmic reticulum stress (ERS)-related signaling pathway. Furthermore, we found that appropriate levels of Se (0.40 mg/kg-0.61 mg/kg diet) inhibited intestinal autophagy in juvenile grass carp, which may be related to ULK1, Beclin 1, ATG5, ATG12, LC3, and P62. In conclusion, appropriate levels of Se can alleviate intestinal inflammation and inhibit ERS and autophagy in juvenile grass carp. A quadratic regression analysis of intestinal ACP and LZ also indicated that the Se requirements of juvenile grass carp were 0.59 and 0.51 mg/kg, respectively.

A phosphodiesterase CpdB in Yersinia pseudotuberculosis degrades CDNs to inhibit innate immune response

Yersinia pseudotuberculosis (Yptb) is a pathogenic gram-negative bacterium that can colonize the intestines of different animals. Its infection leads to the activation of the host’s innate immunity. Both host and bacterial-derived cyclic dinucleotides (CDNs) could activate the innate immune response of host cells. In bacteria, CDNs like c-di-AMP, c-di-GMP, or 3′3'-cGAMP can be hydrolyzed by different hydrolases. Recent studies showed that the degradation of those second messengers helps the pathogen evade immune detection. In this study, we identified a hydrolase, YPK_3776, namely CpdB in Yptb. CpdB is predicted to bind bacterial-derived c-di-AMP, c-di-GMP, 3′3'-cGAMP and host-derived 2′3'-cGAMP. Surprisingly, by using high-performance liquid chromatography (HPLC), we found that CpdB could only degrade bacterial-derived CDNs but not host-derived 2′3'-cGAMP. In addition, CpdB has 2′3'-cNMP activity. Consistently, the Yptb mutant lacking the cpdB gene exhibited a higher level of intracellular c-di-GMP. Furthermore, the ∆cpdB mutant elicited stronger innate immune responses during Yptb infection in macrophages, suggesting CpdB enables Yptb to evade host immune surveillance. Furthermore, CpdB inhibited the Yptb-induced innate immune response in a STING-dependent manner. Finally, we showed the ∆cpdB infection in mice model exhibited in lower bacterial burden, as compared to wild-type strain infection, indicating CpdB is important for bacterial survival in the host. Together, we identified a cyclic dinucleotide hydrolase CpdB in Yptb that could degrade bacterial-derived CDNs which help the pathogen to evade immune detection via the STING pathway.

Quantum dots as a fluorescent labeling tool for live-cell imaging of Leptospira.

Leptospirosis is a global public health problem caused by Gram-negative pathogenic bacteria belonging to the genus Leptospira. The disease is transmitted through the urine of infected animals, which contaminates water and soil, leading to the infection of other animals and humans. Currently, several approaches exist to detect these bacteria; however, a new sensitive method for the live-cell imaging of Leptospira is required. In this study, we report the green synthesis of cadmium telluride quantum dots (CdTe QDs) which are unique fluorescent nanocrystals with a high fluorescence quantum yield capable of modifying cell surfaces and are biocompatible with cells. The fabrication of QDs with concanavalin A (ConA), a carbohydrate-binding lectin and known biological probe for Gram-negative bacteria, produced ConA-QDs which can effectively bind on Leptospira and exhibit strong fluorescence under simple fluorescence microscopy, allowing the live-cell imaging of the bacteria. Overall, we performed the simple synthesis of ConA-QDs and demonstrated their potential use as versatile fluorescent probes for the live-cell imaging of Leptospira. This technique could be further applied to track leptospiral cells and study the infection mechanism, contributing to a more thorough understanding of leptospirosis and how to control it in the future.

Detection of Molecular Vibrations of Shigella Pathogenic Gram-negative Bacterium with Surface Enhanced Raman Spectroscopy (SERS) Biosensors and Investigation of its Antibacterial Activity with Silver Nanoparticles Prepared by the Tollens Method in a Laboratory Environment

Detection of Molecular Vibrations of Shigella Pathogenic Gram-negative Bacterium with Surface Enhanced Raman Spectroscopy (SERS) Biosensors and Investigation of its Antibacterial Activity with Silver Nanoparticles Prepared by the Tollens Method in a Laboratory Environment

Metabolic and Lipid Biomarkers for Pathogenic Algae, Fungi, Cyanobacteria, Mycobacteria, Gram-Positive Bacteria, and Gram-Negative Bacteria.

The utilization of metabolomics and lipidomics analytical platforms in the study of pathogenic microbes is slowly expanding. These research approaches will significantly contribute to the establishment of microbial metabolite and lipid databases of significant value to all researchers in microbiology. In this review, we present a high-level overview of some examples of biomarkers that can be used to detect the presence of microbes, monitor the expansion/decline of a microbe population, and add to our understanding of microbe biofilms and pathogenicity. In addition, increased knowledge of the metabolic functions of pathogenic microbes can contribute to our understanding of microbes that are utilized in diverse industrial applications. Our review focuses on lipids, secondary metabolites, and non-ribosomal peptides that can be monitored using electrospray ionization high-resolution mass spectrometry (ESI-HRMS).

Medical Device-Associated Infections Caused by Biofilm-Forming Microbial Pathogens and Controlling Strategies.

Hospital-acquired infections, also known as nosocomial infections, include bloodstream infections, surgical site infections, skin and soft tissue infections, respiratory tract infections, and urinary tract infections. According to reports, Gram-positive and Gram-negative pathogenic bacteria account for up to 70% of nosocomial infections in intensive care unit (ICU) patients. Biofilm production is a main virulence mechanism and a distinguishing feature of bacterial pathogens. Most bacterial pathogens develop biofilms at the solid-liquid and air-liquid interfaces. An essential requirement for biofilm production is the presence of a conditioning film. A conditioning film provides the first surface on which bacteria can adhere and fosters the growth of biofilms by creating a favorable environment. The conditioning film improves microbial adherence by delivering chemical signals or generating microenvironments. Microorganisms use this coating as a nutrient source. The film gathers both inorganic and organic substances from its surroundings, or these substances are generated by microbes in the film. These nutrients boost the initial growth of the adhering bacteria and facilitate biofilm formation by acting as a food source. Coatings with combined antibacterial efficacy and antifouling properties provide further benefits by preventing dead cells and debris from adhering to the surfaces. In the present review, we address numerous pathogenic microbes that form biofilms on the surfaces of biomedical devices. In addition, we explore several efficient smart antiadhesive coatings on the surfaces of biomedical device-relevant materials that manage nosocomial infections caused by biofilm-forming microbial pathogens.

In vitro Evaluation of Antimicrobial Activity of Syzigium aromaticum (Clove) against Bacteria Isolated from Different Clinical Specimens in Shendi Town, Sudan

Background: Herbal medicinal products have been documented as a significant source for discovering new pharmaceutical molecules that have been used to treat serious diseases. It has been postulated that the geographical locations of the herbs affect the constituents of their essential oils and thus the degree of their antimicrobial action. Syzigium aromaticum (clove) is a traditional spice used as an antimicrobial agent and an alternative solution to increased antibiotic resistance by bacterial strains. Objective: This study aimed to study the in vitro antimicrobial activity of different clove concentrations against bacteria isolated from clinical specimens. Methods: This is a prospective cross-sectional study conducted in Shendi City, Sudan, from February to March 2023, at the Microbiology Laboratory, Faculty of Medical Laboratory Sciences. 50 samples were collected from urine and wounds, from which eight strains of pathogenic gram-positive and gram-negative bacteria were isolated and identified using gram stain and biochemical tests. Clove was tested using a 100%, 50%, 25%, and 12.5% concentration. Results: Out of 50 clinical specimens, standard strains were confirmed as S. aureus 13 (26%), S. epidermidis 7 (14%), E. faecalis 1 (2%), E. coli 15 (30%), Enterobacter 3 (6%), Citrobacter 2 (4%), K. pneumoniae 4 (8%), and P. aeruginosa 5 (10%). Clove showed remarkable antimicrobial activity against all clinical isolates and standard strains. Conclusion: The findings of this study showed that the aqueous extract of clove can exhibit high antimicrobial activity against all types of tested organisms, both clinical and standard. The findings indicate that, besides being safe and sensorial attractive, Clove has antimicrobial activity, making it an herbal antimicrobial agent.

KpsS1 Mediates the Glycosylation of Pseudaminic Acid in Acinetobacter Baumannii.

Pseudaminic acid (Pse) is found in the polysaccharide structures of the cell surface of various Gram-negative pathogenic bacteria including Acinetobacter baumannii and considered as an important component of cell surface glycans including oligosaccharides and glycoproteins. However, the glycosyltransferase that is responsible for the Pse glycosylation in A. baumannii remains unknown yet. In this study, through comparative genomics analysis of Pse-positive and negative A. baumannii clinical isolates, we identified a potential glycosyltransferase, KpsS1, located right downstream of the Pse biosynthesis genetic locus. Deletion of this gene in an Pse-positive A. baumannii strain, Ab8, impaired the glycosylation of Pse to the surface CPS and proteins, while the gene knockout strain, Ab8ΔkpsS1, could still produce Pse with 2.86 folds higher amount than that of Ab8. Furthermore, impairment of Pse glycosylation affected the morphology and virulence potential of A. baumannii, suggesting the important role of this protein. This study will provide insights into the further understanding of Pse in bacterial physiology and pathogenesis.

Photocatalytic, Antimicrobial, and Cytotoxic Efficacy of Biogenic Silver Nanoparticles Fabricated by Bacillus amyloliquefaciens

The biomass filtrate of the endophytic bacterial strain Bacillus amyloliquefaciens Fa.2 was utilized for the eco-friendly production of silver nanoparticles (Ag-NPs). The yellowish-brown color’s optical properties showed a maximum surface plasmon resonance at 415 nm. The morphological and elemental composition analysis reveals the formation of spherical shapes with sizes of 5–40 nm, and the Ag ion comprises the major component of the produced Ag-NPs. X-ray diffraction confirmed the crystalline structure, whereas dynamic light scattering reveals the high stability of synthesized Ag-NPs with a polydispersity index of 0.413 and a negative zeta potential value. The photocatalytic experiment showed the efficacy of Ag-NPs to degrade methylene blue with maximum percentages of 73.9 ± 0.5 and 87.4 ± 0.9% under sunshine and UV irradiation, respectively, compared with 39.8% under dark conditions after 210 min. Additionally, the reusability of Ag-NPs was still more active for the fifth run, with a percentage decrease of 11.6% compared with the first run. Interestingly, the biogenic Ag-NPs showed superior antimicrobial activity against different pathogenic Gram-negative bacteria (MIC = 6.25 µg mL−1), Gram-positive bacteria (MIC = 12.5 µg mL−1), and uni- and multicellular fungi (MIC = 12.5 µg mL−1). Moreover, the biosynthesized Ag-NPs could target cancer cells (Pc3 and Mcf7) at low concentrations compared with normal cell (Vero) lines. The IC50 of normal cells is 383.7 ± 4.1 µg mL−1 compared with IC50 Pc3 (2.5 ± 3.5 µg mL−1) and McF7 (156.1 ± 6.8 µg mL−1). Overall, the bacterially synthesized Ag-NPs showed multifunctional features to be used in environmental catalysis and biomedical applications.

Biological Activity of Horehound (Marrubium vulgare L.) Herb Grown in Poland and Its Phytochemical Composition.

Marrubium vulgare (Lamiaceae) is a plant which has long been known and used in traditional medicine for various purposes. However, few recent studies have documented its chemical composition and biological properties. The present study investigated the phytochemical composition of horehound, as well as its protective, antioxidant, and antimicrobial potential. GC-MS analysis revealed that the major components of horehound essential oil are E-caryophyllene (35.7%), germacrene D (25.2%), and bicyclogermacrene (10.6%). The biological activity of horehound hydroethanolic herb extract derives from multiple chemical compounds, including polyphenols (55.72 mg/mL), flavonoids (11.01 mg/mL), phenolic acids (4.33 mg/mL), and tannins (4.46 mg/mL). Chromatographic analyses of the extract identified 12 phenolic compounds, of which ferulic acid, catechin, quercetin, protocatechuic acid, rutin, and syringic acid (35.42, 24.69, 20.65, 18.70, 14.46, and 12.69 mg/mL, respectively) were the main constituents. Its DPPH radical scavenging ability was 68.29%, while its antioxidant properties, determined by the FRAP method, were at the level of 1.22 mmol/L. Moreover, M. vulgare extract decreased the level of intracellular reactive oxygen species in the fibroblasts and keratinocytes in vitro, achieving the strongest antioxidant effect at a concentration of 2.5% in the case of both types of skin cells. Extracts from the horehound herb showed significant antimicrobial and anti-biofilm activity, confirming the plant's potential in therapeutic applications against various microbial pathogens (gram-positive and gram-negative bacteria and fungi). The research results demonstrate the protective effect of horehound extract on the viability of both fibroblasts and keratinocytes in vitro. To sum up, M. vulgare, as a valuable natural material with high preventive and therapeutic effectiveness, is a potential candidate for new applications in the pharmaceutical and cosmetics industries.

The Role of Bacterial Extracellular Vesicles in the Immune Response to Pathogens, and Therapeutic Opportunities.

Pathogenic bacteria have several mechanisms to evade the host's immune response and achieve an efficient infection. Bacterial extracellular vesicles (EVs) are a relevant cellular communication mechanism, since they can interact with other bacterial cells and with host cells. In this review, we focus on the EVs produced by some World Health Organization (WHO) priority Gram-negative and Gram-positive pathogenic bacteria; by spore-producing bacteria; by Mycobacterium tuberculosis (a bacteria with a complex cell wall); and by Treponema pallidum (a bacteria without lipopolysaccharide). We describe the classification and the general properties of bacterial EVs, their role during bacterial infections and their effects on the host immune response. Bacterial EVs contain pathogen-associated molecular patterns that activate innate immune receptors, which leads to cytokine production and inflammation, but they also contain antigens that induce the activation of B and T cell responses. Understanding the many effects of bacterial EVs on the host's immune response can yield new insights on the pathogenesis of clinically important infections, but it can also lead to the development of EV-based diagnostic and therapeutic strategies. In addition, since EVs are efficient activators of both the innate and the adaptive immune responses, they constitute a promising platform for vaccine development.

Correlation Analysis between STING Promoter Polymorphism and Susceptibility to Infection after Chemotherapy for Multiple Myeloma

To investigate the correlation between the stimulator of interferon genes (STING ) promoter polymorphism and the susceptibility to infection after chemotherapy for multiple myeloma. A total of 102 patients who had undergone chemotherapy for multiple myeloma in our hospital from January 2016 to July 2022 were selected. Depending on the presence or absence of infection after chemotherapy, the enrolled patients were divided into infection group (53 cases) and non-infection group (49 cases). The infection sites and distribution characteristics of pathogenic bacteria of the infection group were analyzed. The genotype distribution of STING gene promoter rs587777609 was compared between the two groups, and the risk factors of infection after chemotherapy for multiple myeloma were analyzed. For infection site, digestive system, respiratory system, urinary system, skin and mucous membranes accounted for 43.40%, 26.42%, 20.75%, and 9.43%, respectively. For pathogenic bacteria, Gram-negative bacteria, Gram-positive bacteria and fungi accounted for 57.14%, 26.98%, and 15.87%, respectively. The CC genotype frequency of STING gene rs587777609 locus in the infection group was lower than that in the non-infection group, while the TT genotype frequency was higher than that in the non-infection group (P < 0.05). The proportions of patients with diabetes, chronic obstructive pulmonary disease, renal insufficiency, serum albumin level< 35 g/L, ISS stage III, mechanical ventilation, and indwelling catheter in the infection group were higher than those in the non-infection group (P < 0.05). Multivariate logistic regression analysis showed that diabetes (OR =1.992), serum albumin level< 35 g/L (OR =2.782), ISS stage III (OR =2.707), mechanical ventilation (OR =3.031), and TT genotype (OR =2.401) were risk factors of infection after chemotherapy for multiple myeloma (P < 0.05). There is a correlation between STING promoter polymorphism and the susceptibility to infection after chemotherapy for multiple myeloma, and patients with TT genotype have a higher risk of infection.

A Gram-negative-selective antibiotic that spares the gut microbiome.

Infections caused by Gram-negative pathogens are increasingly prevalent and are typically treated with broad-spectrum antibiotics, resulting in disruption of the gut microbiome and susceptibility to secondary infections1-3. There is a critical need for antibiotics that are selective both for Gram-negative bacteria over Gram-positive bacteria, as well as for pathogenic bacteria over commensal bacteria. Here we report the design and discovery of lolamicin, a Gram-negative-specific antibiotic targeting the lipoprotein transport system. Lolamicin has activity against a panel of more than 130 multidrug-resistant clinical isolates, shows efficacy in multiple mouse models of acute pneumonia and septicaemia infection, and spares the gut microbiome in mice, preventing secondary infection with Clostridioides difficile. The selective killing of pathogenic Gram-negative bacteria by lolamicin is a consequence of low sequence homology for the target in pathogenic bacteria versus commensals; this doubly selective strategy can be a blueprint for the development of other microbiome-sparing antibiotics.

Prevalence and Antibiotic Susceptibility of Gram-Negative Bacteria Isolated from Different Meat Samples in Baghdad City

Background: The occurrence of Gram-negative (G -ve) bacteria in meat samples raises a major concern due to the possibility of drug resistance incidence since G -ve bacteria have built-in resistance mechanisms and can pass on genetic elements that enable other bacterial species to develop into drug-resistant as well. This drug resistance could be transferred to consumers through a food-borne route. This study aimed to evaluate the prevalence of Gram-negative bacteria in meat samples as well as to detect their antibiotic susceptibility patterns. Methods: For this purpose, 100 meat samples (ground meat, raw burgers, frozen chicken, and chicken carcasses) were collected, and obtained isolates were identified using conventional microbiological techniques including cultural and microscopic identification. After that antibiotic susceptibility patterns were detected using Kirby Bauer's disc diffusion method. Results: Results showed that 91 of the samples were harboring Gram-negative bacteria and E.coli was the most common isolate (51.64%) followed by Klebsiella pneumoniae (18.68%) while the least common isolate was each of E. coli O157:H7, Aeromonas hydrophila, Kluyvera spp., Raoultella terrigena, Hafnia alvei, and Serratia marcescens (1.10%). Susceptibility test showed that all isolates were susceptible to Meropenem and Imipenem while Ampicillin was the most resisted antibiotic. Conclusion: We conclude that meat samples harbor numerous pathogenic Gram-negative bacteria which showed antibiotic-resistant ability toward most tested drugs. However, Meropenem and Imipenem were the least resisted drugs which makes them an appropriate choice for the treatment of foodborne infections.

PurA is the main target of aurodox, a type III secretion system inhibitor

Anti-microbial resistance (AMR) is one of the greatest threats to global health. The continual battle between the emergence of AMR and the development of drugs will be extremely difficult to stop as long as traditional anti-biotic approaches are taken. In order to overcome this impasse, we here focused on the type III secretion system (T3SS), which is highly conserved in many Gram-negative pathogenic bacteria. The T3SS is known to be indispensable in establishing disease processes but not essential for pathogen survival. Therefore, T3SS inhibitors may be innovative anti-infective agents that could dramatically reduce the evolutionary selective pressure on strains resistant to treatment. Based on this concept, we previously identified a polyketide natural product, aurodox (AD), as a specific T3SS inhibitor using our original screening system. However, despite its promise as a unique anti-infective drug of AD, the molecular target of AD has remained unclear. In this paper, using an innovative chemistry and genetic biology-based approach, we show that AD binds to adenylosuccinate synthase (PurA), which suppresses the production of the secreted proteins from T3SS, resulting in the expression of bacterial virulence both in vitro and in vivo experiments. Our findings illuminate the potential of PurA as a target of anti-infective drugs and vaccination and could open a avenue for application of PurA in the regulation of T3SS.