Persistent bacterial infections, antibiotic tolerance, and the oxidative stress response

Effect of host microenvironment and bacterial lifestyles on antimicrobial sensitivity and implications for susceptibility testing

Bacterial infections remain a major global health issue, with antimicrobial resistance (AMR) worsening the crisis. However, treatment failure can occur even when bacteria show antibiotic susceptibility in diagnostic tests. We explore factors such as phenotypic resilience, bacterial lifestyles such as biofilms, and differences between laboratory tests and real infection sites, highlighting the need for improved platforms to better predict treatment outcomes, and reviewing emerging technologies aimed at improving susceptibility testing.

Modulating oxidative stress: a reliable strategy for coping with community-acquired pneumonia in older adults

Community-acquired pneumonia (CAP) remains one of the leading respiratory diseases worldwide. With the aging of the global population, the morbidity, criticality and mortality rates of CAP in older adults remain high every year. Modulating the signaling pathways that cause the inflammatory response and improve the immune function of patients has become the focus of reducing inflammatory damage in the lungs, especially CAP in older adults. As an important factor that causes the inflammatory response of CAP and affects the immune status of the body, oxidative stress plays an important role in the occurrence, development and treatment of CAP. Furthermore, in older adults with CAP, oxidative stress is closely associated with immune senescence, sarcopenia, frailty, aging, multimorbidity, and polypharmacy. Therefore, multiple perspectives combined with the disease characteristics of older adults with CAP were reviewed to clarify the research progress and application value of modulating oxidative stress in older adults with CAP. Clearly, there is no doubt that targeted modulation of oxidative stress benefits CAP in older adults. However, many challenges and unknowns concerning how to modulate oxidative stress for further practical clinical applications exist, and more targeted research is needed. Moreover, the limitations and challenges of modulating oxidative stress are analyzed with the aim of providing references and ideas for future clinical treatment or further research in older adults with CAP.

Influence of agarose in semi-IPN hydrogels for sustained Polymyxin B release

Hydrogels (HGs) are 3-D polymeric networks with high water content, making them appropriate for biomedical applications such as drug delivery systems. This study examines the impact of agarose in semi-interpenetrating polymer networks (Semi-IPNs) based on poly(acrylic acid) (p(AA)), N, N' Methylenebis(acrylamide) (MBA) and agarose (AGA) on the sustained release of Polymyxin B (PolB). Agarose incorporation improved the mechanical strength, swelling behavior and drug retention capacity of the HG. We synthesized the Semi-IPN HGs via free radical polymerization and characterized their structural and thermal properties using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The features of swelling under physiological conditions were carried out. Additionally, we conducted release kinetics using the three prepared HGs, each of which had a distinct amount of AGA. The findings demonstrated that the Semi-IPN HGs with greater AGA concentrations had drug release profiles that were slower and more sustained, making them perfect for long-term therapeutic uses. We also tested the PolB-loaded HGs' antimicrobial efficacy against Pseudomonas aeruginosa, and they showed sustained antibacterial activity. Using NIH-3T3 fibroblast cells, we verified the HGs' biocompatibility, demonstrating their appropriateness for use in biomedicine. According to these findings, agarose modified Semi-IPN HGs may find application in long-term medication delivery systems that aid in the treatment of infections and promote wound healing.

The Invisible Threat of Antibiotic Resistance in Food

The continued and improper use of antibiotics has resulted in the emergence of antibiotic resistance (AR). The dissemination of antibiotic-resistant microorganisms occurs via a multitude of pathways, including the food supply. The failure to comply with the regulatory withdrawal period associated with the treatment of domestic animals or the illicit use of antibiotics as growth promoters has contributed to the proliferation of antibiotic-resistant bacteria in meat and dairy products. It was demonstrated that not only do animal and human pathogens act as donors of antibiotic resistance genes, but also that lactic acid bacteria can serve as reservoirs of genes encoding for antibiotic resistance. Consequently, the consumption of fermented foods also presents a potential conduit for the dissemination of AR. This review provides an overview of the potential for the transmission of antibiotic resistance in a range of traditional and novel foods. The literature data reveal that foodborne microbes can be a significant factor in the dissemination of antibiotic resistance.

Enhancing antibiotic therapy through comprehensive pharmacokinetic/pharmacodynamic principles

Antibiotic therapy relies on understanding both pharmacokinetics (PK) and pharmacodynamics (PD), which respectively address drug absorption, distribution, and elimination, and the relationship between drug concentration and antimicrobial efficacy. This review synthesizes decades of research, drawing from in-vitro studies, in-vivo models, and clinical observations, to elucidate the temporal dynamics of antibiotic activity. We explore how these dynamics, including concentration-effect relationships and post antibiotic effects, inform the classification of antibiotics based on their PD profiles. Additionally, we discuss the pivotal role of PK/PD principles in determining optimal dosage regimens. By providing a comprehensive overview of PK/PD principles in antibiotic therapy, this review aims to enhance understanding and improve treatment outcomes in clinical practice.

Harnessing Cyclic di-GMP Signaling: A Strategic Approach to Combat Bacterial Biofilm-Associated Chronic Infections

Cyclic dimeric guanosine monophosphate (c-di-GMP) plays a vital role within the nucleotide signaling network of bacteria, participating in various biological processes such as biofilm formation and toxin production, among others. Substantial evidence demonstrates its critical involvement in the progression of chronic infections. Treating chronic infections seems critical, and there is a worldwide quest for drugs that target pathogens' unique and complex virulence-associated signaling networks. c-di-GMP is a promising therapeutic target by serving as a distinct virulence factor, solving problems associated with drug resistance, biofilm dispersion, and its related septicemia complications. c-di-GMP levels act as checkpoints for several biofilm-associated molecular pathways, viz., Gac/Rsm, BrlR, and SagS signaling systems. C-di-GMP is also engaged in the Wsp chemosensory pathway responsible for rugose small colony variants observed in cystic fibrosis-related lung infections. Considering all factors, c-di-GMP serves as a pivotal hub in the intricate cascade of biofilm regulation. By overseeing QS systems, exopolysaccharide synthesis, and antibiotic resistance pathways in chronic infections, it emerges as a linchpin for effective drug development strategies against biofilm-related ailments. This underscores the significance of understanding the multifaceted signaling networks. c-di-GMP's role is highlighted in this review as a concealed virulence component in various bacterial pathogens, suggesting that medications targeting it could hold promise in treating chronic disorders associated with biofilms.

Adaptive Resistance of Staphylococcus aureus to Cefquinome Sulfate in an In Vitro Pharmacokinetic Model with Transcriptomic Insights

Cefquinome sulfate has a strong killing effect against Staphylococcus aureus (S. aureus), but bacterial resistance has become increasingly widespread. Experiments were conducted to investigate the pattern of adaptive resistance of S. aureus to cefquinome sulfate under different dosage regimens by using pharmacokinetic-pharmacodynamics (PK-PD) modeling, and the adaptive-resistant bacteria in different states were screened and subjected to transcriptomic sequencing. The results showed that the minimum inhibitory concentration of Staphylococcus aureus under the action of cefquinome sulfate was 0.5 μg/mL, the anti-mutation concentration was 1.6 μg/mL, and the mutation selection window range was 0.5~1.6 μg/mL. In the in vitro pharmacokinetic model to simulate different dosing regimens in the animal body, there are certain rules for the emergence of adaptive drug-resistant bacteria: the intensity of bacterial resistance gradually increased with culture time, and the order of emergence was tolerant bacteria (TO) followed by persistent bacteria (PE) and finally resistant bacteria (RE). The sequence reflected the evolution of adaptive drug resistance. Transcriptome Gene Ontology (GO) analysis revealed that differentially expressed genes were involved in cellular respiration, energy derivation by oxidation of organic compounds, and oxidation-reduction processes. The differentially expressed genes identified functioned in the synthesis of cell membranes, cytoplasm, and intracellular parts. A Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis found that 65 genes were differentially expressed after cefquinome sulfate treatment, of which 35 genes were significantly upregulated and 30 genes were significantly downregulated. Five genes, sdhB, sdhA, pdhA, lpdA, and sucC, may be involved in network regulation. This study revealed the cross-regulation of multiple metabolic pathway networks and the targets of network regulation of S. aureus to produce adaptive drug resistance. The results will provide guidance for clinical drug use in animals infected with S. aureus.

JM, Hubbard AE, Mertens AN, Lin A. Treatment heterogeneity of water, sanitation, hygiene, and nutrition interventions on child growth by environmental enteric dysfunction and pathogen status for young children in Bangladesh

BACKGROUND

Water, sanitation, hygiene (WSH), nutrition (N), and combined (N+WSH) interventions are often implemented by global health organizations, but WSH interventions may insufficiently reduce pathogen exposure, and nutrition interventions may be modified by environmental enteric dysfunction (EED), a condition of increased intestinal permeability and inflammation. This study investigated the heterogeneity of these treatments' effects based on individual pathogen and EED biomarker status with respect to child linear growth.

METHODS

We applied cross-validated targeted maximum likelihood estimation and super learner ensemble machine learning to assess the conditional treatment effects in subgroups defined by biomarker and pathogen status. We analyzed treatment (N+WSH, WSH, N, or control) randomly assigned in-utero, child pathogen and EED data at 14 months of age, and child HAZ at 28 months of age. We estimated the difference in mean child height for age Z-score (HAZ) under the treatment rule and the difference in stratified treatment effect (treatment effect difference) comparing children with high versus low pathogen/biomarker status while controlling for baseline covariates.

RESULTS

We analyzed data from 1,522 children who had a median HAZ of -1.56. We found that fecal myeloperoxidase (N+WSH treatment effect difference 0.0007 HAZ, WSH treatment effect difference 0.1032 HAZ, N treatment effect difference 0.0037 HAZ) and Campylobacter infection (N+WSH treatment effect difference 0.0011 HAZ, WSH difference 0.0119 HAZ, N difference 0.0255 HAZ) were associated with greater effect of all interventions on anthropometry. In other words, children with high myeloperoxidase or Campylobacter infection experienced a greater impact of the interventions on anthropometry. We found that a treatment rule that assigned the N+WSH (HAZ difference 0.23, 95% CI (0.05, 0.41)) and WSH (HAZ difference 0.17, 95% CI (0.04, 0.30)) interventions based on EED biomarkers and pathogens increased predicted child growth compared to the randomly allocated intervention.

CONCLUSIONS

These findings indicate that EED biomarkers and pathogen status, particularly Campylobacter and myeloperoxidase (a measure of gut inflammation), may be related to the impact of N+WSH, WSH, and N interventions on child linear growth.

Therapeutic Indices of Topical Antiseptics in Wound Care: A Systematic Review

GENERAL PURPOSE

To review the therapeutic indices of topical antiseptics for bacterial species commonly isolated from chronic wounds.

TARGET AUDIENCE

This continuing education activity is intended for physicians, physician assistants, nurse practitioners, and registered nurses with an interest in skin and wound care.

LEARNING OBJECTIVES/OUTCOMES

After participating in this educational activity, the participant will:1. Explain the mechanisms underlying chronic wound physiology and their implications for effective wound healing and management.2. Evaluate the role of therapeutic index values for topical antiseptics in chronic wound management.3. Apply evidence-based treatment strategies for chronic wound management.

Aminoglycoside heteroresistance in Enterobacter cloacae is driven by the cell envelope stress response

Enterobacter cloacae is a Gram-negative nosocomial pathogen of the ESKAPE (Enterococcus, Staphylococcus, Klebsiella, Acinetobacter, Pseudomonas, and Enterobacter spp.) priority group with increasing multi-drug resistance via the acquisition of resistance plasmids. However, E. cloacae can also display forms of antibiotic refractoriness, such as heteroresistance and tolerance. Here, we report that E. cloacae displays transient heteroresistance to aminoglycosides, which is accompanied with the formation of small colony variants (SCVs) with increased minimum inhibitor concentration (MIC) of gentamicin and other aminoglycosides used in the clinic, but not other antibiotic classes. To explore the underlying mechanisms, we performed RNA sequencing of heteroresistant bacteria, which revealed global gene expression changes and a signature of the CpxRA cell envelope stress response. Deletion of the cpxRA two-component system abrogated aminoglycoside heteroresistance and SCV formation, pointing to its indispensable role in these processes. The introduction of a constitutively active allele of cpxA led to high aminoglycoside MICs, consistent with cell envelope stress response driving these behaviors in E. cloacae. Cell envelope stress can be caused by environmental cues, including heavy metals. Indeed, bacterial exposure to copper increased gentamicin MIC in the wild-type but not in the ΔcpxRA mutant. Moreover, copper exposure also elevated the gentamicin MICs of clinical isolates from bloodstream infections, suggesting that CpxRA- and copper-dependent aminoglycoside resistance is broadly conserved in E. cloacae strains. Altogether, we establish that E. cloacae relies on transcriptional reprogramming via the envelope stress response pathway for transient resistance to a major class of frontline antibiotic.IMPORTANCEEnterobacter cloacae is a bacterium that belongs to the WHO high-priority group and an increasing threat worldwide due its multi-drug resistance. E. cloacae can also display heteroresistance, which has been linked to treatment failure. We report that E. cloacae shows heteroresistance to aminoglycoside antibiotics. These are important frontline microbicidal drugs used against Gram-negative bacterial infections; therefore, understanding how resistance develops among sensitive strains is important. We show that aminoglycoside resistance is driven by the activation of the cell envelope stress response and transcriptional reprogramming via the CpxRA two-component system. Furthermore, heterologous activation of envelope stress via copper, typically a heavy metal with antimicrobial actions, also increased aminoglycoside MICs of the E. cloacae type strain and clinical strains isolated from bloodstream infections. Our study suggests aminoglycoside recalcitrance in E. cloacae could be broadly conserved and cautions against the undesirable effects of copper.

Metabolites augment oxidative stress to sensitize antibiotic-tolerant Staphylococcus aureus to fluoroquinolones

If left unchecked, infections involving antibiotic-refractory bacteria are expected to cause millions of deaths per year in the coming decades. Beyond genetically resistant bacteria, persisters, which are genetically susceptible cells that survive antibiotic doses that kill the rest of the clonal population, can potentially contribute to treatment failure and infection relapse. Stationary-phase bacterial cultures are enriched with persisters, and it has been shown that stimulating these populations with exogenous nutrients can reduce persistence to different classes of antibiotics, including topoisomerase-targeting fluoroquinolones (FQs). In this study, we show that adding glucose and amino acids to nutrient-starved Staphylococcus aureus cultures enhanced their sensitivity to FQs, including delafloxacin (Dela)-a drug that was recently approved for treating staphylococcal infections. We found that while the added nutrients increased nucleic acid synthesis, this increase was not required to sensitize S. aureus to FQs. We further demonstrate that addition of these nutrients increases membrane potential and the ability to generate harmful reactive oxygen species (ROS) during FQ treatment. Chelating iron, scavenging hydroxyl radicals, and limiting oxygenation during FQ treatment and during recovery following FQ treatment rescued nutrient-stimulated S. aureus. In all, our data suggest that while nutrient stimulation increases the activity of FQ targets in stationary-phase S. aureus, the resulting generation of ROS, presumably made possible through metabolic upregulation, is the primary driver of increased sensitivity to these drugs.IMPORTANCEStaphylococcus aureus causes many chronic and relapsing infections because of its ability to endure host immunity and antibiotic therapy. While several studies have focused on the nutrient requirements for the formation and maintenance of staphylococcal infections, the effects of the nutrient environment on bacterial responses to antibiotic treatment remain understudied. Here, we show that adding nutrients to starved S. aureus activates biosynthetic processes, including DNA synthesis, but it is the generation of harmful reactive oxidants that sensitizes S. aureus to DNA topoisomerase-targeting FQs. Our results suggest that the development of approaches aimed at perturbing metabolism and increasing oxidative stress can potentiate the bactericidal activity of FQs against antibiotic-tolerant S. aureus.

Contribution of the infection ecosystem and biogeography to antibiotic failure in vivo

The acquisition of antibiotic resistance in bacteria, though a deeply concerning international issue, is reasonably well-understood at a mechanistic level. Less well-understood is why bacteria that are sensitive in vitro to well-established and widely-used antibiotics sometimes fail to respond to these agents in vivo. This is a particularly common problem in chronic, polymicrobial infection scenarios. Here, we discuss this in vitro-in vivo disconnect from the perspective of the bacterium, focusing in particular on how infection micro/macro-environment, biogeography, and the presence of co-habiting species affect the response to antibiotics. Using selected exemplars, we also consider interventions that might improve treatment outcomes, as well as ecologically 'eubiotic' approaches that have less of an impact on the patient's commensal microflora. In our view, the accrued data strongly suggest that we need a more comprehensive understanding of the in situ microbiology at infection sites.

Green synthesis of selenium nanoparticles from Cassia javanica flowers extract and their medical and agricultural applications

Nanostructured materials are advantageous within numerous fields of medicine owing to their intriguing qualities, which include their size, reactive surface, bioactivity, potential for modification, and optical characteristics. Cassia javanica flower extract was used as a chelating agent in an environmentally friendly process to create SeNPs FTIR, XRD, and TEM, SAED were utilized to analyze and characterize the synthesized. The findings showed that the MIC of Se NPs against B. subtilis and S. aureus was 500 µg/ml. Conversely, the MIC for P. aeruginosa, E. coli, and C. albicans were 125, 250, and 62.5 µg/ml, respectively. Hence, SeNPs considerably reduced the activity; the inhibition peaked at 77.6% at 250 µg/ml to reach 49.04% at 7.8 µg/ml. Which showed the greatest suppression of MRSA biofilm formation without affecting bacterial growth. SeNPs showed an intriguing antioxidant capacity, achieving an IC50 of 53.34 µg/ml. This study looked how soaking seeds before sowing them with Se NPs at 50, 100, and 200 ppm affected the plants' development in different parameters, as well as their yield of Vicia faba L. The growth conditions were effectively increased by soaking application of various quantities of Se NPs. The highest values of dry weight/pod (g), number of seeds/plant, weight of 100 seeds (g), and number of pods/plant were caused by high concentrations of Se NPs, by 28.43, 89.60, 18.20, and 94.11%, respectively.

Oxidative stress response in avian pathogenic Escherichia coli

Avian pathogenic Escherichia coli (APEC) leads to significant economic losses in the poultry industry worldwide and restricts the development of the poultry industry. Oxidative stress, through the production of reactive oxygen species (ROS), damage iron‑sulfur (FeS) clusters, cysteine and methionine protein residues, and DNA, and then result in bacterial cells death. APEC has evolved a series of regulation systems to sense and quickly and appropriately respond to oxidative stress. Quorum sensing (QS), second messenger (SM), transcription factors (TFs), small regulatory RNAs (sRNAs), and two-component system (TCS) are important regulation systems ubiquitous in bacteria. It is of great significance to control APEC infection through investigating the molecular regulation mechanism on APEC adapting to oxidative stress. However, how the cross-talk among these regulation systems co-regulates transcription of oxidative stress-response genes in APEC has not been reported. This review suggests exploring connector proteins that co-regulate these regulation systems that co-activate transcription of oxidative stress-response genes to disrupt bacterial antioxidative defense mechanism in APEC, and then using these connector proteins as drug targets to control APEC infection. This review might contribute to illustrating the functional mechanism of APEC adapting to oxidative stress and exploring potential drug targets for the prevention and treatment of APEC infection.

Netupitant Exhibits Potent Activity on Mycobacterium tuberculosis Persisters

In Mycobacterium tuberculosis (Mtb), persisters are genotypically drug-sensitive bacteria that nonetheless survive antibiotic treatment. Persisters represent a significant challenge to shortening TB treatment and preventing relapse, underscoring the need for new therapeutic strategies. In this study, we screened 2,336 FDA-approved compounds to identify agents that enhance the sterilizing activity of standard anti-TB drugs and prevent the regrowth of persisters. Netupitant (NTP), an FDA-approved antiemetic, emerged as a promising candidate with bacteriostatic activity on its own. However, in combination with isoniazid (INH) and rifampicin (RIF), NTP eliminated viable Mtb cells within 7 days, achieving a >6-log reduction in colony-forming units (CFUs) compared to the 2.5-log reduction observed with INH-RIF alone. NTP also demonstrated broad-spectrum efficacy, enhancing the activity of multiple TB drugs, including ethambutol, moxifloxacin, amikacin, and bedaquiline. Notably, NTP retained its potency under hypoxic and caseum-mimicking conditions, both of which are known to enrich for non-replicating, drug-tolerant cells. Interestingly, under hypoxic conditions, NTP demonstrated strong tuberculocidal activity, achieving an approximate 4-log CFU reduction, whereas high-dose INH-RIF was ineffective. Transcriptomic analysis revealed that NTP primarily disrupts cellular bioenergetics, with significant downregulation observed in activities associated with the electron transport chain, oxidative phosphorylation, NADH-ubiquinone oxidoreductase, succinate dehydrogenase, and ATP synthesis. While further studies are required to decipher the mechanism of action and resistance profile of NTP, and to assess its in vivo efficacy, these findings underscore its potential as a promising adjunct to existing TB therapies.

A perspective on nanomaterials against Campylobacter jejuni biofilm - New control strategies

Campylobacter jejuni - a Gram-negative bacterium - is considered the fourth cause of diarrheic diseases that can form biofilms (mono and multi-species) or colonize pre-existing biofilms adhering to both, inert or biotic surfaces; its biofilms contribute to transmission through the food chain and survival under harsh environmental conditions. Thus, developing alternatives against this pathogen is compulsory. Nanomaterials have revolutionized the way of fighting infections related to biofilms due to their unique properties compared to traditional antibiotics. Nanomaterials have also been used against C. jejuni based on zinc, titanium, silver, molybdenum, magnesium, cobalt, erbium, lithium, nickel, hydroxide, polyethylene, graphene, lipids, chitosan, and poly(lactic-co-glycolic acid) (PLGA). Those organic and inorganic materials have synthesized nanoparticles, nanofillers, nanowires, nanoferrites, double layers, nanocomposites, and films that have encapsulated, entrapped, coated or doped molecules. Additionally, bare metal nanoparticles have been tested by their antimicrobial activity on planktonic and sessile forms. Therefore, the present review aimed to describe general biology, virulence factors, host-pathogen relationships and biofilm formation, as well as nanomaterials and nanoparticles fighting against C. jejuni biofilms. Considerations are presented and placed in perspective.

Detection of pathogenic gram-negative bacteria using an antimicrobial peptides-modified bipolar electrode-electrochemiluminescence platform

Real-time, label-free detection of gram-negative bacteria with high selectivity and sensitivity is demonstrated using a bipolar electrode-electrochemiluminescence (BPE-ECL) platform. This platform utilizes anode luminescence and cathode modification of antimicrobial peptides (AMPs) to effectively capture bacteria. Magainin I, basic AMP from Xenopus skin, boasting an α-helix structure, exhibits a preferential affinity for the surface of gram-negative pathogens. The covalent attachment of the peptide's C-terminal carboxylic acid to the free amines of a previously thiolated linker ensures its secure immobilization onto the surface of the interdigitated gold-plated cathode of BPE. The AMP-modified BPE sensor, when exposed to varying concentrations of gram-negative bacteria, produces reproducible ECL intensities, allowing for the detection of peptide-bacteria interactions within the range 1 to 104 CFU mL-1. Furthermore, this AMP-modified BPE sensor demonstrates a selective capacity to detect Escherichia coli O157:H7 amidst other gram-negative strains, even at a concentration of 1-CFU mL-1. This study underscores the high selectivity of Magainin I in bacterial detection, and the AMP-modified BPE-ECL system holds significant promise for rapid detection of gram-negative bacteria in various applications. The AMP-modified BPE sensor generated reproducible ECL intensity that detected peptide-bacteria interactions in the range 1 to 104 CFU mL-1. The AMP-modified BPE sensor also selectively detected E. coli O157:H7 from other gram-negative strains at a concentration of 1-CFU mL-1. In this paper, AMP demonstrated high selectivity in bacterial detection. The AMP-modified BPE-ECL system prepared has a great potential for application in the field of rapid detection of gram-negative bacteria.

P-glycoprotein inhibitors as an adjunct therapy for TB

The primary challenge in TB treatment is the emergence of multidrug-resistant TB (MDR-TB). One of the major factors responsible for MDR is the upregulation of efflux pumps. Permeation-glycoprotein (P-gp), an efflux pump, hinders the bioavailability of the administered drugs inside the infected cells. Simultaneously, angiogenesis, the formation of new blood vessels, contributes to drug delivery complexities. TB infection triggers a cascade of events that upregulates the expression of angiogenic factors and P-gp. The combined action of P-gp and angiogenesis foster the emergence of MDR-TB. Understanding these mechanisms is pivotal for developing targeted interventions to overcome MDR in TB. P-gp inhibitors, such as verapamil, and anti-angiogenic drugs, including bevacizumab, have shown improvement in TB drug delivery to granuloma. In this review, we discuss the potential of P-gp inhibitors as an adjunct therapy to shorten TB treatment.

GC-MS Profiling and Pharmacological Potential of Physconia venusta (Ach.) Poelt

Objectives

Lichens are complex symbiotic organisms that generate various bioactive compounds with significant therapeutic value. We investigated the chemical composition and bioactivity of the acetone extract of the Algerian lichen Physconia venusta (Ach.) poet.

Materials and Methods

Phytochemical screening was performed using gas chromatography-mass spectrometry (GC-MS). The antibacterial activity was assessed against Escherichia coli, Pseudomonas aeruginosa, Salmonella enteritidis, Salmonella typhi, Staphylococcus aureus, Listeria monocytogenes, and Bacillus subtilis using an agar diffusion test with the determination of the minimal inhibition concentration (MIC), while the antioxidant activity was determined using different chemical methods (DPPH, ABTS, CUPRAC, reducing power, superoxide anion scavenging, β-carotene bleaching, and metal chelate). In addition, cytotoxic activity was tested using Artemia salina (Brine shrimp) bioassay.

Results

The studied extract exhibited intense antibacterial activity against E. coli and S. aureus with inhibition diameters of 28 ± 0.01 and 22 ± 0.01 mm, respectively, with a MIC value of 6.25 mg/mL and a selectivity index of 2.8. The obtained extract showed different antioxidant trends depending on the selected assay. GC-MS analysis revealed many secondary metabolites.

Conclusion

P. venusta, a type of lichen, is a potential source of bioactive substances that could be used in pharmaceuticals.

Reactive Oxygen Species (ROS)-Mediated Antibacterial Oxidative Therapies: Available Methods to Generate ROS and a Novel Option Proposal

The increasing emergence of multidrug-resistant (MDR) pathogens causes difficult-to-treat infections with long-term hospitalizations and a high incidence of death, thus representing a global public health problem. To manage MDR bacteria bugs, new antimicrobial strategies are necessary, and their introduction in practice is a daily challenge for scientists in the field. An extensively studied approach to treating MDR infections consists of inducing high levels of reactive oxygen species (ROS) by several methods. Although further clinical investigations are mandatory on the possible toxic effects of ROS on mammalian cells, clinical evaluations are extremely promising, and their topical use to treat infected wounds and ulcers, also in presence of biofilm, is already clinically approved. Biochar (BC) is a carbonaceous material obtained by pyrolysis of different vegetable and animal biomass feedstocks at 200-1000 °C in the limited presence of O2. Recently, it has been demonstrated that BC's capability of removing organic and inorganic xenobiotics is mainly due to the presence of persistent free radicals (PFRs), which can activate oxygen, H2O2, or persulfate in the presence or absence of transition metals by electron transfer, thus generating ROS, which in turn degrade pollutants by advanced oxidation processes (AOPs). In this context, the antibacterial effects of BC-containing PFRs have been demonstrated by some authors against Escherichia coli and Staphylococcus aureus, thus giving birth to our idea of the possible use of BC-derived PFRs as a novel method capable of inducing ROS generation for antimicrobial oxidative therapy. Here, the general aspects concerning ROS physiological and pathological production and regulation and the mechanism by which they could exert antimicrobial effects have been reviewed. The methods currently adopted to induce ROS production for antimicrobial oxidative therapy have been discussed. Finally, for the first time, BC-related PFRs have been proposed as a new source of ROS for antimicrobial therapy via AOPs.

Exploring Therapeutic Potential of Catalase: Strategies in Disease Prevention and Management

The antioxidant defense mechanisms play a critical role in mitigating the deleterious effects of reactive oxygen species (ROS). Catalase stands out as a paramount enzymatic antioxidant. It efficiently catalyzes the decomposition of hydrogen peroxide (H2O2) into water and oxygen, a potentially harmful byproduct of cellular metabolism. This reaction detoxifies H2O2 and prevents oxidative damage. Catalase has been extensively studied as a therapeutic antioxidant. Its applications range from direct supplementation in conditions characterized by oxidative stress to gene therapy approaches to enhance endogenous catalase activity. The enzyme's stability, bioavailability, and the specificity of its delivery to target tissues are significant hurdles. Furthermore, studies employing conventional catalase formulations often face issues related to enzyme purity, activity, and longevity in the biological milieu. Addressing these challenges necessitates rigorous scientific inquiry and well-designed clinical trials. Such trials must be underpinned by sound experimental designs, incorporating advanced catalase formulations or novel delivery systems that can overcome existing limitations. Enhancing catalase's stability, specificity, and longevity in vivo could unlock its full therapeutic potential. It is necessary to understand the role of catalase in disease-specific contexts, paving the way for precision antioxidant therapy that could significantly impact the treatment of diseases associated with oxidative stress.

Unlocking the enigma of phenotypic drug tolerance: Mechanisms and emerging therapeutic strategies

In the ongoing battle against antimicrobial resistance, phenotypic drug tolerance poses a formidable challenge. This adaptive ability of microorganisms to withstand drug pressure without genetic alterations further complicating global healthcare challenges. Microbial populations employ an array of persistence mechanisms, including dormancy, biofilm formation, adaptation to intracellular environments, and the adoption of L-forms, to develop drug tolerance. Moreover, molecular mechanisms like toxin-antitoxin modules, oxidative stress responses, energy metabolism, and (p)ppGpp signaling contribute to this phenomenon. Understanding these persistence mechanisms is crucial for predicting drug efficacy, developing strategies for chronic bacterial infections, and exploring innovative therapies for refractory infections. In this comprehensive review, we dissect the intricacies of drug tolerance and persister formation, explore their role in acquired drug resistance, and highlight emerging therapeutic approaches to combat phenotypic drug tolerance. Furthermore, we outline the future landscape of interventions for persistent bacterial infections.

Discovery of antibiotics that selectively kill metabolically dormant bacteria

There is a need to discover and develop non-toxic antibiotics that are effective against metabolically dormant bacteria, which underlie chronic infections and promote antibiotic resistance. Traditional antibiotic discovery has historically favored compounds effective against actively metabolizing cells, a property that is not predictive of efficacy in metabolically inactive contexts. Here, we combine a stationary-phase screening method with deep learning-powered virtual screens and toxicity filtering to discover compounds with lethality against metabolically dormant bacteria and favorable toxicity profiles. The most potent and structurally distinct compound without any obvious mechanistic liability was semapimod, an anti-inflammatory drug effective against stationary-phase E. coli and A. baumannii. Integrating microbiological assays, biochemical measurements, and single-cell microscopy, we show that semapimod selectively disrupts and permeabilizes the bacterial outer membrane by binding lipopolysaccharide. This work illustrates the value of harnessing non-traditional screening methods and deep learning models to identify non-toxic antibacterial compounds that are effective in infection-relevant contexts.

Treatment Heterogeneity of Water, Sanitation, Hygiene, and Nutrition Interventions on Child Growth by Environmental Enteric Dysfunction and Pathogen Status for Young Children in Bangladesh

Background

Water, sanitation, hygiene (WSH), nutrition (N), and combined (N+WSH) interventions are often implemented by global health organizations, but WSH interventions may insufficiently reduce pathogen exposure, and nutrition interventions may be modified by environmental enteric dysfunction (EED), a condition of increased intestinal permeability and inflammation. This study investigated the heterogeneity of these treatments' effects based on individual pathogen and EED biomarker status with respect to child linear growth.

Methods

We applied cross-validated targeted maximum likelihood estimation and super learner ensemble machine learning to assess the conditional treatment effects in subgroups defined by biomarker and pathogen status. We analyzed treatment (N+WSH, WSH, N, or control) randomly assigned in-utero, child pathogen and EED data at 14 months of age, and child LAZ at 28 months of age. We estimated the difference in mean child length for age Z-score (LAZ) under the treatment rule and the difference in stratified treatment effect (treatment effect difference) comparing children with high versus low pathogen/biomarker status while controlling for baseline covariates.

Results

We analyzed data from 1,522 children, who had median LAZ of -1.56. We found that myeloperoxidase (N+WSH treatment effect difference 0.0007 LAZ, WSH treatment effect difference 0.1032 LAZ, N treatment effect difference 0.0037 LAZ) and Campylobacter infection (N+WSH treatment effect difference 0.0011 LAZ, WSH difference 0.0119 LAZ, N difference 0.0255 LAZ) were associated with greater effect of all interventions on growth. In other words, children with high myeloperoxidase or Campylobacter infection experienced a greater impact of the interventions on growth. We found that a treatment rule that assigned the N+WSH (LAZ difference 0.23, 95% CI (0.05, 0.41)) and WSH (LAZ difference 0.17, 95% CI (0.04, 0.30)) interventions based on EED biomarkers and pathogens increased predicted child growth compared to the randomly allocated intervention.

Conclusions

These findings indicate that EED biomarker and pathogen status, particularly Campylobacter and myeloperoxidase (a measure of gut inflammation), may be related to impact of N+WSH, WSH, and N interventions on child linear growth.

Strategies for the eradication of intracellular bacterial pathogens

Intracellular pathogens affect a significant portion of world population and cause millions of deaths each year. They can invade host cells and survive inside them and are extremely resistant to immune systems and antibiotics. Current treatments have limitations, and therefore, new effective therapies are needed to combat this ongoing health challenge. Active research efforts have been made to develop many new strategies to eradicate these intracellular pathogens. In this review, we focus on the intracellular bacterial pathogens and first introduce several representative intracellular bacteria and the diseases they cause. We then discuss the challenges in eradicating these bacteria and summarize the current therapeutics for intracellular bacteria. Finally, recent advances in intracellular bacteria eradication are highlighted.

Understanding bacterial pathogenicity: a closer look at the journey of harmful microbes

Bacteria are the most prevalent form of microorganisms and are classified into two categories based on their mode of existence: intracellular and extracellular. While most bacteria are beneficial to human health, others are pathogenic and can cause mild to severe infections. These bacteria use various mechanisms to evade host immunity and cause diseases in humans. The susceptibility of a host to bacterial infection depends on the effectiveness of the immune system, overall health, and genetic factors. Malnutrition, chronic illnesses, and age-related vulnerabilities are the additional confounders to disease severity phenotypes. The impact of bacterial pathogens on public health includes the transmission of these pathogens from healthcare facilities, which contributes to increased morbidity and mortality. To identify the most significant threats to public health, it is crucial to understand the global burden of common bacterial pathogens and their pathogenicity. This knowledge is required to improve immunization rates, improve the effectiveness of vaccines, and consider the impact of antimicrobial resistance when assessing the situation. Many bacteria have developed antimicrobial resistance, which has significant implications for infectious diseases and favors the survival of resilient microorganisms. This review emphasizes the significance of understanding the bacterial pathogens that cause this health threat on a global scale.

Solving polymicrobial puzzles: evolutionary dynamics and future directions

Polymicrobial infections include various microorganisms, often necessitating different treatment methods than a monomicrobial infection. Scientists have been puzzled by the complex interactions within these communities for generations. The presence of specific microorganisms warrants a chronic infection and impacts crucial factors such as virulence and antibiotic susceptibility. Game theory is valuable for scenarios involving multiple decision-makers, but its relevance to polymicrobial infections is limited. Eco-evolutionary dynamics introduce causation for multiple proteomic interactions like metabolic syntropy and niche segregation. The review culminates both these giants to form evolutionary dynamics (ED). There is a significant amount of literature on inter-bacterial interactions that remain unsynchronised. Such raw data can only be moulded by analysing the ED involved. The review culminates the inter-bacterial interactions in multiple clinically relevant polymicrobial infections like chronic wounds, CAUTI, otitis media and dental carries. The data is further moulded with ED to analyse the niche colonisation of two notoriously competitive bacteria: S.aureus and P.aeruginosa. The review attempts to develop a future trajectory for polymicrobial research by following recent innovative strategies incorporating ED to curb polymicrobial infections.

Antibiotic Efficacy in Escherichia coli and Klebsiella pneumoniae Under Nutrient Limitation and Effectiveness of Colistin-Based Antibiotic Combinations to Eradicate Persister Cells

Persister cells are responsible for recurrent or chronic infections resulting in antibiotic treatment failure. We aimed to investigate antibiotic efficacy in Escherichia coli and Klebsiella pneumoniae strains with limited metabolic activity. Bacterial cells cultured in nutrient-limited media showed characteristic persister phenotypes, including low intracellular ATP concentration, maintenance of antibiotic susceptibility, and an increase of (p)ppGpp levels. Amikacin showed no bactericidal activity under nutrient limitation conditions; however, metabolism-dependent ciprofloxacin exhibited metabolism-independent activity. The activity of colistin was metabolism-dependent, but it was retained under limited nutrient conditions. Nutrient limitation and antibiotic stress were related to the SOS response through recA expression in all four strains of E. coli and K. pneumoniae. However, the mRNA expression patterns of relA and spoT (associated with (p)ppGpp synthesis) and hpf and rpoS (downstream target genes of (p)ppGpp signaling) varied according to bacterial species, strain, and antibiotics, indicating diverse responses to nutrient stress in various persister cells. We also investigated the efficacy of antibiotic combinations to eradicate persister cells. As a result, colistin-based combinations were effective in the eradication of both E. coli and K. pneumoniae persister cells. In this study, persister cells were shown to be induced by metabolic stress, reducing antibiotic efficacy. We identified that combinations of colistin with amikacin or ciprofloxacin were effective to eliminate E. coli and K. pneumoniae persister cells.

A review on the effects of discharging conventionally treated livestock waste to the environmental resistome

Globally, animal production has developed rapidly as a consequence of the ongoing population growth, to support food security. This has consequently led to an extensive use of antibiotics to promote growth and prevent diseases in animals. However, most antibiotics are not fully metabolized by these animals, leading to their excretion within urine and faeces, thus making these wastes a major reservoir of antibiotics residues, antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB) in the environment. Farmers normally depend on conventional treatment methods to mitigate the environmental impact of animal waste; however, these methods are not fully efficient to remove the environmental resistome. The present study reviewed the variability of residual antibiotics, ARB, as well as ARGs in the conventionally treated waste and assessed how discharging it could increase resistome in the receiving environments. Wherein, considering the efficiency and environmental safety, an addition of pre-treatments steps with these conventional treatment methods could enhance the removal of antibiotic resistance agents from livestock waste.

Photocatalytic effect of N-TiO2 conjugated with folic acid against biofilm-forming resistant bacteria

Antibiotic resistance challenges the treatment of bacterial biofilm-related infections, but the use of nanoparticles as a treatment is a promising strategy to overcome bacterial infections. This study applied nitrogen-doped titanium dioxide (N-TiO2) conjugated with folic acid (FA) on biofilm-forming resistant bacteria. The photocatalytic effect of TiO2 nanoparticles (NPs) was studied under ultraviolet (UV), visible light, and dark conditions at 60, 120, and 180 min against planktonic cells and biofilms of Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa. TiO2 NPs were in the anatase phase, spherical shaped with sizes of 10-13 nm, and effectively doped and conjugated with N and FA. The FA-conjugated nanoparticles (N-TiO2-FA and FA-TiO2) were shown to have a bactericidal effect on all bacteria between 60 and 180 min under UV and visible light conditions. Concerning biofilms, N-TiO2-FA was shown to have a highly disruptive effect on all bacterial biofilms under UV irradiation at 180 min. Meanwhile, the nanoparticles did not show DNA damaging potential and they had no cytostatic effect, indicating that these NPs are biocompatible. In sum, nanoparticle conjugation with FA promoted photocatalytic effectiveness, revealing the promise this nanomaterial holds as a biocompatible antimicrobial agent.

Fluoroquinolone and beta-lactam antimicrobials induce different transcriptome profiles in Salmonella enterica persister cells

Here, we investigate the transcriptome profiles of two S. Enteritidis and one S. Schwarzengrund isolates that present different persister levels when exposed to ciprofloxacin or ceftazidime. It was possible to note a distinct transcript profile among isolates, time of exposure, and treatment. We could not find a commonly expressed transcript profile that plays a role in persister formation after S. enterica exposure to beta-lactam or fluoroquinolone, as only three DEGs presented the same behavior under the conditions and isolates tested. It appears that the formation of persisters in S. enterica after exposure to ciprofloxacin is linked to the overexpression of genes involved in the SOS response (recA), cell division inhibitor (sulA), iron-sulfur metabolism (hscA and iscS), and type I TA system (tisB). On the other hand, most genes differentially expressed in S. enterica after exposure to ceftazidime appeared to be downregulated and were part of the flagellar assembly apparatus, citrate cycle (TCA cycle), glycolysis/gluconeogenesis, carbon metabolism, bacterial secretion system, quorum sensing, pyruvate metabolism pathway, and biosynthesis of secondary metabolites. The different transcriptome profiles found in S. enterica persisters induced by ciprofloxacin and ceftazidime suggest that these cells modulate their response differently according to each stress.

Shigella Serotypes Associated With Carriage in Humans Establish Persistent Infection in Zebrafish

Shigella represents a paraphyletic group of enteroinvasive Escherichia coli. More than 40 Shigella serotypes have been reported. However, most cases within the men who have sex with men (MSM) community are attributed to 3 serotypes: Shigella sonnei unique serotype and Shigella flexneri 2a and 3a serotypes. Using the zebrafish model, we demonstrate that Shigella can establish persistent infection in vivo. Bacteria are not cleared by the immune system and become antibiotic tolerant. Establishment of persistent infection depends on the O-antigen, a key constituent of the bacterial surface and a serotype determinant. Representative isolates associated with MSM transmission persist in zebrafish, while representative isolates of a serotype not associated with MSM transmission do not. Isolates of a Shigella serotype establishing persistent infections elicited significantly less macrophage death in vivo than isolates of a serotype unable to persist. We conclude that zebrafish are a valuable platform to illuminate factors underlying establishment of Shigella persistent infection in humans.

Regulation of σB-Dependent Biofilm Formation in Staphylococcus aureus through Strain-Specific Signaling Induced by Diosgenin

Staphylococcus aureus is a commensal skin bacterium and a causative agent of infectious diseases. Biofilm formation in S. aureus is a mechanism that facilitates the emergence of resistant strains. This study proposes a mechanism for the regulation of biofilm formation in S. aureus through strain-specific physiological changes induced by the plant steroid diosgenin. A comparison of diosgenin-induced changes in the expression of regulatory genes associated with physiological changes revealed the intracellular regulatory mechanisms involved in biofilm formation. Diosgenin reduced biofilm formation in S. aureus ATCC 6538 and methicillin-resistant S. aureus (MRSA) CCARM 3090 by 39% and 61%, respectively. Conversely, it increased biofilm formation in S. aureus ATCC 29213 and MRSA CCARM 3820 by 186% and 582%, respectively. Cell surface hydrophobicity and extracellular protein and carbohydrate contents changed in a strain-specific manner in response to biofilm formation. An assessment of the changes in gene expression associated with biofilm formation revealed that diosgenin treatment decreased the expression of icaA and spa and increased the expression of RNAIII, agrA, sarA, and sigB in S. aureus ATCC 6538 and MRSA CCARM 3090; however, contrasting gene expression changes were noted in S. aureus ATCC 29213 and MRSA CCARM 3820. These results suggest that a regulatory mechanism of biofilm formation is that activated sigB expression sequentially increases the expression of sarA, agrA, and RNAIII. This increased RNAIII expression decreases the expression of spa, a surface-associated adhesion factor. An additional regulatory mechanism of biofilm formation is that activated sigB expression decreases the expression of an unknown regulator that increases the expression of icaA. This in turn decreases the expression of icaA, which decreases the synthesis of polysaccharide intercellular adhesins and ultimately inhibits biofilm formation. By assessing strain-specific contrasting regulatory signals induced by diosgenin in S. aureus without gene mutation, this study elucidated the signal transduction mechanisms that regulate biofilm formation based on physiological and gene expression changes.

Mechanisms of Virulence Reprogramming in Bacterial Pathogens

Bacteria are single-celled organisms that carry a comparatively small set of genetic information, typically consisting of a few thousand genes that can be selectively activated or repressed in an energy-efficient manner and transcribed to encode various biological functions in accordance with environmental changes. Research over the last few decades has uncovered various ingenious molecular mechanisms that allow bacterial pathogens to sense and respond to different environmental cues or signals to activate or suppress the expression of specific genes in order to suppress host defenses and establish infections. In the setting of infection, pathogenic bacteria have evolved various intelligent mechanisms to reprogram their virulence to adapt to environmental changes and maintain a dominant advantage over host and microbial competitors in new niches. This review summarizes the bacterial virulence programming mechanisms that enable pathogens to switch from acute to chronic infection, from local to systemic infection, and from infection to colonization. It also discusses the implications of these findings for the development of new strategies to combat bacterial infections.

Environmental conditions define the energetics of bacterial dormancy and its antibiotic susceptibility

Bacterial cells that stop growing but maintain viability and the capability to regrow are termed dormant and have been shown to transiently tolerate high concentrations of antimicrobials. Links between tolerance and cellular energetics as a possible explanation for the tolerance, have been investigated and have produced mixed and seemingly contradictory results. Because dormancy merely indicates growth arrest, which can be induced by various stimuli, we hypothesize that dormant cells may exist in a range of energetic states that depend on the environment. To energetically characterize different dormancies, we first induce them in a way that results in dormant populations and subsequently measure both of their main energy sources, the proton motive force magnitude and the concentration of ATP. We find that different types of dormancy exhibit characteristic energetic profiles that vary in level and dynamics. The energetic makeup was associated with survival to some antibiotics but not others. Our findings portray dormancy as a state that is rich in phenotypes with various stress survival capabilities. Because environmental conditions outside of the lab often halt or limit microbial growth, a typologization of dormant states may yield relevant insights on the survival and evolutionary strategies of these organisms.

Lipoxin A4 promotes antibiotic and monocyte bacterial killing in established Pseudomonas aeruginosa biofilm formed under hydrodynamic conditions

Pseudomonas aeruginosa is a gram-negative, opportunistic bacteria commonly found in wounds and in lungs of immunocompromised patients. These bacteria commonly form biofilms which encapsulate the bacteria, making it difficult for antibiotics or immune cells to reach the bacterial cells. We previously reported that Lipoxin A4 (LxA4 ), a Specialized Pro-resolving Mediator, has direct effects on P. aeruginosa where it reduced biofilm formation and promoted ciprofloxacin antibiotic efficacy in a static biofilm-forming system. In the current studies, we examined the actions of LxA4 on established biofilms formed in a biofilm reactor under dynamic conditions with constant flow and shear stress. These conditions allow for biofilm growth with nutrient replenishment and for examination of bacteria within the biofilm structure. We show that LxA4 helped ciprofloxacin reduction of live/dead ratio of bacteria within the biofilm. THP-1 monocytes interacted with the biofilm to increase the number of viable bacteria within the biofilm as well as TNF-α production in the biofilm milieu, suggesting that monocyte interaction with bacterial biofilm exacerbates the inflammatory state. Pre-treatment of the THP-1 monocytes with LxA4 abolished the increase in biofilm bacteria and reduced TNF-α production. The effect of decreased biofilm bacteria was associated with increased LxA4 -induced monocyte adherence to biofilm but not increased bacteria killing suggesting that the mechanism for the reduced biofilm bacteria was due to LxA4 -mediated increase in adherence to biofilm. These results suggest that LxA4 can help antibiotic efficacy and promote monocyte activity against established P. aeruginosa biofilm formed under hydrodynamic conditions.

1,8-Cineol (Eucalyptol) Disrupts Membrane Integrity and Induces Oxidative Stress in Methicillin-Resistant Staphylococcus aureus

Due to the increased emergence of drug-resistant bacteria, the declining efficiency of traditional antimicrobials has generated severe concerns in recent years. Subsequently, more interest in other antimicrobial agents from natural resources draws more attention as an alternative to conventional medications. This study investigated the bactericidal mechanism of monoterpene 1,8-cineol (eucalyptol), a major compound of various essential oils, against methicillin-resistant Staphylococcus aureus (MRSA). The antibacterial activity of 1,8-cineol was assessed by an MTT assay against clinical and reference MRSA strains. A cell membrane integrity test, followed by zeta potential (ZP) measurements, was performed to evaluate the disruption of the bacterial membrane integrity. Additionally, the cytotoxic effect of this molecule on MRSA bacteria was investigated by monitoring reactive oxygen species (ROS) generation, lipid peroxidation (MDA), and antioxidant enzyme activities (CAT and SOD). Regarding the anti-staphylococcal effect, the obtained results revealed the antibacterial efficacy of 1,8-cineol wherein the minimum inhibitory concentrations were equal to 7.23 mg/mL. Furthermore, it enhanced membrane permeability, with a 5.36-fold increase in nucleic acid and protein leakage as compared with untreated strains, along with the alteration of surface charge (ZP) in MRSA cells. The tested compound caused an increase in ROS generation reaching 17,462 FU and MDA production, reaching 9.56 μM/mg protein, in treated bacterial cells, along with a decrease in oxidative stress enzymes activities. Our findings suggest that 1,8-cineol has the ability to damage the membrane integrity and induce ROS-mediated oxidative stress in MRSA cells, leading to its antagonistic effect against this pathogen and consequently aiding in the reversal of antibiotic resistance.

Mycobacterium tuberculosis grows linearly at the single-cell level with larger variability than model organisms

The ability of bacterial pathogens to regulate growth is crucial to control homeostasis, virulence, and drug response. Yet, we do not understand the growth and cell cycle behaviors of Mycobacterium tuberculosis (Mtb), a slow-growing pathogen, at the single-cell level. Here, we use time-lapse imaging and mathematical modeling to characterize these fundamental properties of Mtb. Whereas most organisms grow exponentially at the single-cell level, we find that Mtb exhibits a unique linear growth mode. Mtb growth characteristics are highly variable from cell-to-cell, notably in their growth speeds, cell cycle timing, and cell sizes. Together, our study demonstrates that growth behavior of Mtb diverges from what we have learned from model bacteria. Instead, Mtb generates a heterogeneous population while growing slowly and linearly. Our study provides a new level of detail into how Mtb grows and creates heterogeneity, and motivates more studies of growth behaviors in bacterial pathogens.

The versatile defender: exploring the multifaceted role of p62 in intracellular bacterial infection

As a highly conserved, multifunctional protein with multiple domains, p62/SQSTM1 plays a crucial role in several essential cellular activities, particularly selective autophagy. Recent research has shown that p62 is crucial in eradicating intracellular bacteria by xenophagy, a selective autophagic process that identifies and eliminates such microorganisms. This review highlights the various roles of p62 in intracellular bacterial infections, including both direct and indirect, antibacterial and infection-promoting aspects, and xenophagy-dependent and independent functions, as documented in published literature. Additionally, the potential applications of synthetic drugs targeting the p62-mediated xenophagy mechanism and unresolved questions about p62's roles in bacterial infections are also discussed.

Vitamin K3 (Menadione) is a multifunctional microbicide acting as a photosensitizer and synergizing with blue light to kill drug-resistant bacteria in biofilms

Cutaneous bacterial wound infections typically involve gram-positive cocci such as Staphylococcus aureus (SA) and usually become biofilm infections. Bacteria in biofilms may be 100-1000-fold more resistant to an antibiotic than the clinical laboratory minimal inhibitory concentration (MIC) for that antibiotic, contributing to antimicrobial resistance (AMR). AMR is a growing global threat to humanity. One pathogen-antibiotic resistant combination, methicillin-resistant SA (MRSA) caused more deaths globally than any other such combination in a recent worldwide statistical review. Many wound infections are accessible to light. Antimicrobial phototherapy, and particularly antimicrobial blue light therapy (aBL) is an innovative non-antibiotic approach often overlooked as a possible alternative or adjunctive therapy to reduce antibiotic use. We therefore focused on aBL treatment of biofilm infections, especially MRSA, focusing on in vitro and ex vivo porcine skin models of bacterial biofilm infections. Since aBL is microbicidal through the generation of reactive oxygen species (ROS), we hypothesized that menadione (Vitamin K3), a multifunctional ROS generator, might enhance aBL. Our studies suggest that menadione can synergize with aBL to increase both ROS and microbicidal effects, acting as a photosensitizer as well as an ROS recycler in the treatment of biofilm infections. Vitamin K3/menadione has been given orally and intravenously worldwide to thousands of patients. We conclude that menadione/Vitamin K3 can be used as an adjunct to antimicrobial blue light therapy, increasing the effectiveness of this modality in the treatment of biofilm infections, thereby presenting a potential alternative to antibiotic therapy, to which biofilm infections are so resistant.

Insights into the Microbicidal, Antibiofilm, Antioxidant and Toxicity Profile of New O-Aryl-Carbamoyl-Oxymino-Fluorene Derivatives

The unprecedented increase in microbial resistance rates to all current drugs raises an acute need for the design of more effective antimicrobial strategies. Moreover, the importance of oxidative stress due to chronic inflammation in infections with resistant bacteria represents a key factor for the development of new antibacterial agents with potential antioxidant effects. Thus, the purpose of this study was to bioevaluate new O-aryl-carbamoyl-oxymino-fluorene derivatives for their potential use against infectious diseases. With this aim, their antimicrobial effect was evaluated using quantitative assays (minimum inhibitory/bactericidal/biofilms inhibitory concentrations) (MIC/MBC/MBIC), the obtained values being 0.156-10/0.312-10/0.009-1.25 mg/mL), while some of the involved mechanisms (i.e., membrane depolarization) were investigated by flow cytometry. The antioxidant activity was evaluated by studying the scavenger capacity of DPPH and ABTS•+ radicals and the toxicity was tested in vitro on three cell lines and in vivo on the crustacean Artemia franciscana Kellog. The four compounds derived from 9H-fluoren-9-one oxime proved to exhibit promising antimicrobial features and particularly, a significant antibiofilm activity. The presence of chlorine induced an electron-withdrawing effect, favoring the anti-Staphylococcus aureus and that of the methyl group exhibited a +I effect of enhancing the anti-Candida albicans activity. The IC50 values calculated in the two toxicity assays revealed similar values and the potential of these compounds to inhibit the proliferation of tumoral cells. Taken together, all these data demonstrate the potential of the tested compounds to be further used for the development of novel antimicrobial and anticancer agents.

Intracellular persister: A stealth agent recalcitrant to antibiotics

The bulk of bacteria transiently evading appropriate antibiotic regimes and recovered from non-resolutive infections are commonly refer to as persisters. In this mini-review, we discuss how antibiotic persisters stem from the interplay between the pathogen and the cellular defenses mechanisms and its underlying heterogeneity.

A novel chemogenomic discovery platform identifies bioactive hits with rapid bactericidal activity against Mycobacteroides Abscessus

Mycobacteroides abscessus (M. ab) infections are innately resistant to most currently available antibiotics and present a growing, poorly addressed medical need. The existing treatment regimens are lengthy and produce inadequate outcomes for many patients. Importantly, most clinically used drugs and drug candidates against M. ab are either bacteriostatic, or only weakly bactericidal. New strategies exploring a broader chemical space are urgently needed, as innovative agents in development are scarce and hit rates in large unbiased screens against the mycobacterium have been discouragingly low. Here we present a computational chemogenomics-driven approach to discovery of novel antibacterials that effectively reveals drug-like compounds active against M. ab, paired with small sets of predicted molecular targets for the compounds. Several of the bioactive hits identified exhibited rapid bactericidal, including sterilizing, activity against the mycobacterium, indicating that there are currently unexploited chemically tractable molecular mechanisms for rapid sterilization of M. ab. Interestingly, starvation, which typically induces drug tolerance, sensitized M. ab to some of the compounds, resulting in potencies similar to those of drugs in clinical use. The presented drug discovery platform has potential to identify highly differentiated prototype anti-infective molecules and thereby contribute to development of regimens for shorter treatment and improved outcomes for non-tuberculous mycobacterial infections.

Evaluation of antibiofilm and cytotoxicity effect of Rumex vesicarius methanol extract

Background

Bacterial resistant to antibiotics represents an obstacle in medication management in hospitals. Biofilm can be easily formed by bacteria in indwelling medical devices. By increasing numbers of patients using indwelling medical devices, we have to find an effective antibiofilm for the eradication of biofilm-associated infections.

Methods

The present study was designed to evaluate the antibiofilm and cytotoxicity effect of methanol extract of Rumex vesicarius L. leaves (Polygonaceae). Antibacterial and antibiofilm assays were investigated in this study against different standard and pathogenic bacteria isolates from endotracheal tubes in intensive care units (Staphylococcus aureus, Staphylococcus epidermidis, Proteus vulgaris, Klebsiella pneumoniae, and Pseudomonas aeruginosa). Scanning electron microscopy was used to demonstrate the reduction of biofilm formation using methanol extract of R. vesicarius. Also, cytotoxicity of R. vesicarius L. was evaluated by using the lactate dehydrogenase assay.

Results

R. vesicarius displayed a broad spectrum and antibacterial activity against the tested organisms. The minimal inhibitory concentration of the methanol extract was 62.5–125 mg/mL for gram positive while in case of gram negative, it was 125–250 mg/mL. While the result in case of minimal bactericidal concentration was 250–500 mg/mL in case of gram positive and was 500–1,000 mg/mL in case of gram negative.

Conclusion

Our results recommend usage of R. vesicarius as a promising antibiofilm to combat infection in indwelling medical devices.

Glucose-Induced Enhanced Virulence in Strains of Multidrug-Resistant Pseudomonas aeruginosa Isolated from Diabetic Patients

Pseudomonas aeruginosa is known for its metabolic versatility and uses a variety of substrates; interestingly, glucose is not the favored carbon source. Although glucose is not readily utilized by them, there is a possibility that the increased susceptibility of diabetics to infections with P. aeruginosa is related to the effect of glucose on the expression of virulence genes. The curiosity in understanding the effect of glucose on virulence gene expression in P. aeruginosa and the lacuna of studies in this field prompted us to undertake the current investigation. It included the quantification of various virulence factors and their gene expression upon supplementation with glucose in clinical MDR P. aeruginosa isolates recovered from diabetics. Interestingly, the study observed a remarkable difference in the virulence attributes in the isolates with and without glucose supplementation. External glucose was found to be modulating the QS gene expression, thus altering the elaboration of other virulence factors. Variations in the gene expressions induced by glucose partly explain the increased susceptibility of diabetic patients to P. aeruginosa infections.

Bacterial Infections and Cancer: Exploring This Association And Its Implications for Cancer Patients

Bacterial infections are common in the etiology of human diseases owing to the ubiquity of bacteria. Such infections promote the development of periodontal disease, bacterial pneumonia, typhoid, acute gastroenteritis, and diarrhea in susceptible hosts. These diseases may be resolved using antibiotics/antimicrobial therapy in some hosts. However, other hosts may be unable to eliminate the bacteria, allowing them to persist for long durations and significantly increasing the carrier's risk of developing cancer over time. Indeed, infectious pathogens are modifiable cancer risk factors, and through this comprehensive review, we highlight the complex relationship between bacterial infections and the development of several cancer types. For this review, searches were performed on the PubMed, Embase, and Web of Science databases encompassing the entirety of 2022. Based on our investigation, we found several critical associations, of which some are causative: Porphyromonas gingivalis and Fusobacterium nucleatum are associated with periodontal disease, Salmonella spp., Clostridium perfringens, Escherichia coli, Campylobacter spp., and Shigella are associated with gastroenteritis. Helicobacter pylori infection is implicated in the etiology of gastric cancer, and persistent Chlamydia infections present a risk factor for the development of cervical carcinoma, especially in patients with the human papillomavirus (HPV) coinfection. Salmonella typhi infections are linked with gallbladder cancer, and Chlamydia pneumoniae infection is implicated in lung cancer, etc. This knowledge helps identify the adaptation strategies used by bacteria to evade antibiotic/antimicrobial therapy. The article also sheds light on the role of antibiotics in cancer treatment, the consequences of their use, and strategies for limiting antibiotic resistance. Finally, the dual role of bacteria in cancer development as well as in cancer therapy is briefly discussed, as this is an area that may help to facilitate the development of novel microbe-based therapeutics as a means of securing improved outcomes.

Expanding therapeutic strategies for intracellular bacterial infections through conjugates of apoptotic body-antimicrobial peptides

Macrophage intracellular infections are difficult to treat because conventional antibiotics tend to have poor penetration of mammalian cells. As a consequence, the immune response is affected and bacteria remain protected inside macrophages. The use of antimicrobial peptides (AMPs) is one of the alternatives developed as new treatments because of their broad spectrum of action. To improve drug delivery into the intracellular space, extracellular vesicles (EVs) have emerged as an innovative strategy for drug delivery. In particular, apoptotic bodies (ApoBDs) are EVs that exhibit attraction to macrophages, which makes them a promising means of improving AMP delivery to treat macrophage intracellular infections. Here, we review important aspects that should be taken into account when developing ApoBD-AMP conjugates.

Nanocarriers for the delivery of antibiotics into cells against intracellular bacterial infection

The barrier function of host cells enables intracellular bacteria to evade the lethality of the host immune system and antibiotics, thereby causing chronic and recurrent infections that seriously threaten human health. Currently, the main clinical strategy for the treatment of intracellular bacterial infections involves the use of long-term and high-dose antibiotics. However, insufficient intracellular delivery of antibiotics along with various resistance mechanisms not only weakens the efficacy of current therapies but also causes serious adverse drug reactions, further increasing the disease and economic burden. Improving the delivery efficiency, intracellular accumulation, and action time of antibiotics remains the most economical and effective way to treat intracellular bacterial infections. The rapid development of nanotechnology provides a strategy to efficiently deliver antibiotics against intracellular bacterial infections into cells. In this review, we summarize the types of common intracellular pathogens, the difficulties faced by antibiotics in the treatment of intracellular bacterial infections, and the research progress of several types of representative nanocarriers for the delivery of antibiotics against intracellular bacterial infections that have emerged in recent years. This review is expected to provide a reference for further elucidating the intracellular transport mechanism of nanocarrier-drug complexes, designing safer and more effective nanocarriers and establishing new strategies against intracellular bacterial infection.

A Bibliometric Analysis of Research on Bacterial Persisters

BACKGROUND

In the past two decades, the surge of research on bacterial persisters has been inspired as increasingly concerning about the frequent failure of antibiotics treatment. This study was aimed at presenting a bibliometric and visualized analysis of relative publications on bacterial persisters, which offered insights into the development and research trends of this field.

METHODS

The Web of Science Core Collection and Ovid MEDLINE databases were utilized to retrieve relevant publications on bacterial persisters from 2001 to 2021. After manual selection, data including titles, authors, journals, author keywords, addresses, the number of citations, and publication years were subsequently extracted. The data analysis and visual mapping were conducted with Excel, SPSS, R studio, and VOSviewer.

RESULTS

In this study, 1,903 relevant publications on bacterial persisters were included. During 2001-2021, there was an exponential growth in the quantity of publications. It was found that these studies were conducted by 7,182 authors from 74 different countries. The USA led the scientific production with the highest total number of publications (859) and citation frequency (52,022). The Antimicrobial Agents and Chemotherapy was the most influential journal with 113 relevant publications. The cooccurrence analysis revealed that studies on bacterial persisters focused on four aspects: "the role of persisters in biofilms," "clinical persistent infection," "anti-persister treatment," and "mechanism of persister formation."

CONCLUSION

In the past two decades, the global field of bacterial persisters has significantly increased. The USA was the leading country in this field. Mechanistic studies continued to be the future hotspots, which may be helpful to adopt new strategies against persisters and solve the problem of chronic infection in the clinic.

Antibacterial Activity of a Natural Clay Mineral against Burkholderia cepacia Complex and Other Bacterial Pathogens Isolated from People with Cystic Fibrosis

There is an impending crisis in healthcare brought about by a new era of untreatable infections caused by bacteria resistant to all available antibiotics. Thus, there is an urgent need to identify novel antimicrobial agents to counter the continuing threat posed by formerly treatable infections. We previously reported that a natural mineral clay known as Kisameet clay (KC) is a potent inhibitor of the organisms responsible for acute infections. Chronic bacterial infections present another major challenge to treatment by antimicrobials, due to their prolonged nature, which results in repeated exposure to antibiotics and a constant selection for antimicrobial resistance. A prime example is bacteria belonging to the Burkholderia cepacia complex (Bcc), which particularly causes some of the most serious chronic lung infections in patients with cystic fibrosis (CF) associated with unpredictable clinical outcomes, poor prognosis, and high mortality rates. Eradication of these organisms from CF patients with limited effective antimicrobial options is a major challenge. Novel therapeutic approaches are urgently required. Here, we report the in vitro antibacterial activity of KC aqueous suspensions (1-10% w/v) and its aqueous extract (L100) against a collection of extensively and multi-drug resistant clinical isolates of Bcc, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia isolated from patients with CF. These findings present a potential novel therapy for further investigation in the clinic.