Potential Treatment Options in a Post-antibiotic Era

NagZ modulates the virulence of E. cloacae by acting through the gene of unknown function, ECL_03795

β-N-acetylglucosaminidase (NagZ), a cytosolic glucosaminidase, plays a pivotal role in peptidoglycan recycling. Previous research demonstrated that NagZ knockout significantly eradicated AmpC-dependent β-lactam resistance in Enterobacter cloacae. However, NagZ's role in the virulence of E. cloacae remains unclear. Our study, incorporating data on mouse and Galleria mellonella larval mortality rates, inflammation markers, and histopathological examinations, revealed a substantial reduction in the virulence of E. cloacae following NagZ knockout. Transcriptome sequencing uncovered differential gene expression between NagZ knockout and wild-type strains, particularly in nucleotide metabolism pathways. Further investigation demonstrated that NagZ deletion led to a significant increase in cyclic diguanosine monophosphate (c-di-GMP) levels. Additionally, transcriptome sequencing and RT-qPCR confirmed significant differences in the expression of ECL_03795, a gene with an unknown function but speculated to be involved in c-di-GMP metabolism due to its EAL domain known for phosphodiesterase activity. Interestingly, in ECL_03795 knockout strains, a notable reduction in the virulence was observed, and virulence was rescued upon complementation with ECL_03795. Consequently, our study suggests that NagZ's function on virulence is partially mediated through the ECL_03795→c-di-GMP pathway, providing insight into the development of novel therapies and strongly supporting the interest in creating highly efficient NagZ inhibitors.

Development of Xanthoangelol-Derived Compounds with Membrane-Disrupting Effects against Gram-Positive Bacteria

Infections caused by multidrug-resistant pathogens have emerged as a serious threat to public health. To develop new antibacterial agents to combat such drug-resistant bacteria, a class of novel amphiphilic xanthoangelol-derived compounds were designed and synthesized by mimicking the structure and function of antimicrobial peptides (AMPs). Among them, compound 9h displayed excellent antimicrobial activity against the Gram-positive strains tested (MICs = 0.5-2 μg/mL), comparable to vancomycin, and with low hemolytic toxicity and good membrane selectivity. Additionally, compound 9h demonstrated rapid bactericidal effects, low resistance frequency, low cytotoxicity, and good plasma stability. Mechanistic studies further revealed that compound 9h had good membrane-targeting ability and was able to destroy the integrity of bacterial cell membranes, causing an increase in intracellular ROS and the leakage of DNA and proteins, thus accelerating bacterial death. These results make 9h a promising antimicrobial candidate to combat bacterial infection.

Antimicrobial Resistance in Aquaculture: Risk Mitigation within the One Health Context

The application of antimicrobials in aquaculture primarily aims to prevent and treat bacterial infections in fish, but their inappropriate use may result in the emergence of zoonotic antibiotic-resistant bacteria and the subsequent transmission of resistant strains to humans via food consumption. The aquatic environment serves as a potential reservoir for resistant bacteria, providing an ideal breeding ground for development of antimicrobial resistance (AMR). The mutual inter-connection of intensive fish-farming systems with terrestrial environments, the food processing industry and human population creates pathways for the transmission of resistant bacteria, exacerbating the problem further. The aim of this study was to provide an overview of the most effective and available risk mitigation strategies to tackle AMR in aquaculture, based on the One Health (OH) concept. The stringent antimicrobial use guidelines, promoting disease control methods like enhanced farm biosecurity measures and vaccinations, alternatives to antibiotics (ABs) (prebiotics, probiotics, immunostimulants, essential oils (EOs), peptides and phage therapy), feeding practices, genetics, monitoring water quality, and improving wastewater treatment, rather than applying excessive use of antimicrobials, can effectively prevent the development of AMR and release of resistant bacteria into the environment and food. The contribution of the environment to AMR development traditionally receives less attention, and, therefore, environmental aspects should be included more prominently in OH efforts to predict, detect and prevent the risks to health. This is of particular importance for low and middle-income countries with a lack of integration of the national AMR action plans (NAPs) with the aquaculture-producing environment. Integrated control of AMR in fisheries based on the OH approach can contribute to substantial decrease in resistance, and such is the case in Asia, where in aquaculture, the percentage of antimicrobial compounds with resistance exceeding 50% (P50) decreased from 52% to 22% within the period of the previous two decades.

Tackling transmission of infectious diseases: A probiotic-based system as a remedy for the spread of pathogenic and resistant microbes

Built environments (BEs) currently represent the areas in which human beings spend most of their life. Consistently, microbes populating BEs mostly derive from human occupants and can be easily transferred from BE to occupants. The hospital microbiome is a paradigmatic example, representing a reservoir for harmful pathogens that can be transmitted to susceptible patients, causing the healthcare-associated infections (HAIs). Environmental cleaning is a crucial pillar in controlling BE pathogens and preventing related infections, and chemical disinfectants have been largely used so far towards this aim. However, despite their immediate effect, chemical-based disinfection is unable to prevent recontamination, has a high environmental impact, and can select/increase antimicrobial resistance (AMR) in treated microbes. To overcome these limitations, probiotic-based sanitation (PBS) strategies were recently proposed, built on the use of detergents added with selected probiotics able to displace surrounding pathogens by competitive exclusion. PBS was reported as an effective and low-impact alternative to chemical disinfection, providing stable rebalance of the BE microbiome and significantly reducing pathogens and HAIs compared to disinfectants, without exacerbating AMR and pollution concerns. This minireview summarizes the most significant results obtained by applying PBS in sanitary and non-sanitary settings, which overall suggest that PBS may effectively tackle the infectious risk meanwhile preventing the further spread of pathogenic and resistant microbes.

Poly(amino acid)-based drug delivery nanoparticles eliminate Methicillin resistant Staphylococcus aureus via tunable release of antibiotic

Bacterial infections threaten public health, and novel therapeutic strategies critically demand to be explored. Herein, poly(amino acid) (PAA)-based drug delivery nanoparticles (NPs) were designed for eliminating Methicillin resistant Staphylococcus aureus (MRSA) via tunable release of antibiotic. Using N-acryloyl amino acids (valine, valine methyl ester, aspartic acid, serine) as monomers, four kinds of amphiphilic PAAs were synthesized via photoinduced electron/energy transfer-reversible addition fragmentation chain-transfer (PET-RAFT) polymerization and were further assembled into nano-sized delivery systems. Their assemble behavior was drove mainly by hydrophobic/hydrophilic interaction, which determined the particle size, efficacy of drug loading and release; but numerous hydrogen bonding (HB) interaction also played an important role in regulating morphologies of the NPs and enriching drug-binding capacity. By changing the HB- and hydrophobic-interaction of the PAAs, the particle sizes (240.7 nm-302.7 nm), the drug loading efficiency (9.57%-19.76%), and the Rifampicin (Rif) release rate (49.6%-69.7%) of the PAA-based NPs could be tunable. Specially, the antimicrobial properties of the Rif-loaded NPs are found to be related to the release of Rif, which was determined by its hydrophobic interaction with hydrophobic blocks and HB interaction with hydrophilic blocks. These studies provide a new outlook for the design of delivery systems for the therapy of bacterial infection.

Allicin Alleviated LPS-Induced Mastitis via the TLR4/NF-κB Signaling Pathway in Bovine Mammary Epithelial Cells

Dairy farming is the most important economic activity in animal husbandry. Mastitis is the most common disease in dairy cattle and has a significant impact on milk quality and yield. The natural extract allicin, which is the main active ingredient of the sulfur-containing organic compounds in garlic, has anti-inflammatory, anticancer, antioxidant, and antibacterial properties; however, the specific mechanism underlying its effect on mastitis in dairy cows needs to be determined. Therefore, in this study, whether allicin can reduce lipopolysaccharide (LPS)-induced inflammation in the mammary epithelium of dairy cows was investigated. A cellular model of mammary inflammation was established by pretreating bovine mammary epithelial cells (MAC-T) with 10 µg/mL LPS, and the cultures were then treated with varying concentrations of allicin (0, 1, 2.5, 5, and 7.5 µM) added to the culture medium. MAC-T cells were examined using RT-qPCR and Western blotting to determine the effect of allicin. Subsequently, the level of phosphorylated nuclear factor kappa-B (NF-κB) was measured to further explore the mechanism underlying the effect of allicin on bovine mammary epithelial cell inflammation. Treatment with 2.5 µM allicin considerably decreased the LPS-induced increase in the levels of the inflammatory cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α) and inhibited activation of the NOD-like receptor protein 3 (NLRP3) inflammasome in cow mammary epithelial cells. Further research revealed that allicin also inhibited the phosphorylation of inhibitors of nuclear factor kappa-B-α (IκB-α) and NF-κB p65. In mice, LPS-induced mastitis was also ameliorated by allicin. Therefore, we hypothesize that allicin alleviated LPS-induced inflammation in the mammary epithelial cells of cows probably by affecting the TLR4/NF-κB signaling pathway. Allicin will likely become an alternative to antibiotics for the treatment of mastitis in cows.

Therapeutics for fulminant hepatitis caused by enteroviruses in neonates

Neonatal infection with nonpolio enteroviruses (EVs) causes nonspecific febrile illnesses and even life-threatening multiorgan failure. Hepatitis, which often results in hepatic necrosis followed by disseminated intravascular coagulopathy, is one of the most severe and frequent fatal neonatal EV infection complications. Coxsackievirus B (CVB) 1–5 and many echoviruses have been most commonly identified. Neonatal EV infection treatment has usually involved initial supportive care. Studies for CVB and echovirus infection treatments were developed for more than thirty years. Intravenous immunoglobulin and pleconaril therapy was performed in some clinical trials. Additionally, other studies demonstrated antiviral and/or anti-inflammatory pathogenesis mechanisms of neonatal EV hepatitis in in vitro or in vivo models. These treatments represented promising options for the clinical practice of neonatal EV hepatitis. However, further investigation is needed to elucidate the whole therapeutic potential and safety problems.

Imagining the postantibiotic future: the visual culture of a global health threat

This article is concerned with the visual culture of global health data using antimicrobial resistance (AMR) as an example. I explore how public health data and knowledge are repackaged into visualisations and presented in four contemporary genres: the animation, the TED Talk, the documentary and the satire programme. I focus on how different actors describe a world in which there are no or few antibiotics that are effective against bacterial infections. I examine the form, content and style of the visual cultural of AMR, examining how these genres tell a story of impending apocalypse while also trying to advert it. This is a form of story-telling based around the if/then structure: we are told that if we do not take certain actions today, then we will face a postantibiotic future with certain, often catastrophic, consequences. Within this if/then structure, there are various aims and objectives: the goal may be preventing further spread of AMR, building awareness or pushing for certain policy or funding decisions. These stories also serve to place or deflect blame, on animals, occupations, patients, industries and others and to highlight risks and consequences. These examples share similarities in the forms of story-telling and narrative, and in the use of specific data sources and other images. By using several Swedish examples, I demonstrate how global data are reinterpreted for a national audience. Overall, I argue that while the convergence of a dominant narrative indicates scientific consensus, this consensus also stifles our collective imagination in finding new solutions to the problem. Finally, I also use the example of AMR to discuss the need for a broader social science and humanities engagement with the visual culture of global health data.

Oridonin Attenuates Burkholderia cenocepacia Virulence by Suppressing Quorum-Sensing Signaling

Burkholderia cenocepacia is a human opportunistic pathogen that mostly employs two types of quorum-sensing (QS) systems to regulate its various biological functions and pathogenicity: the cis-2-dodecenoic acid (BDSF) system and the N-acyl homoserine lactone (AHL) system. In this study, we reported that oridonin, which was screened from a collection of natural products, disrupted important B. cenocepacia phenotypes, including motility, biofilm formation, protease production, and virulence. Genetic and biochemical analyses showed that oridonin inhibited the production of BDSF and AHL signals by decreasing the expression of their synthase-encoding genes. Furthermore, we revealed that oridonin directly binds to the regulator RqpR of the two-component system RqpSR that dominates the above-mentioned QS systems to inhibit the expression of the BDSF and AHL signal synthase-encoding genes. Oridonin also binds to the transcriptional regulator CepR of the cep AHL system to inhibit its binding to the promoter of bclACB. These findings suggest that oridonin could potentially be developed as a new QS inhibitor against pathogenic B. cenocepacia. IMPORTANCE Burkholderia cenocepacia is an important human opportunistic pathogen that can cause life-threatening infections in susceptible individuals. It employs quorum-sensing (QS) systems to regulate biological functions and virulence. In this study, we have identified a lead compound, oridonin, that is capable of interfering with B. cenocepacia QS signaling and physiology. We demonstrate that oridonin suppressed cis-2-dodecenoic acid (BDSF) and N-acyl homoserine lactone (AHL) signal production and attenuated virulence in B. cenocepacia. Oridonin also impaired QS-regulated phenotypes in various Burkholderia species. These results suggest that oridonin could interfere with QS signaling in many Burkholderia species and might be developed as a new antibacterial agent.

Investigation into the Metabolism of Quaternary Ammonium Compound Disinfectants by Bacteria

Since the start of the COVID-19 pandemic, our reliance on disinfectants and sanitizers and the use thereof has grown. While this may protect human health, it may be selecting for antimicrobial-resistant microorganisms, including those that are not only capable of growth in the presence of disinfectants but also thrive using this as an energy source. Furthermore, there is a growing concern in emerging nosocomial pathogens, which have shown resistance to antibiotics and disinfectants. This rise in resistance has led to the investigation of various mechanisms behind resistance, such as biofilms, efflux pumps, and mobile genetic elements. Although many resistance mechanisms have been identified, it was discovered that some potentially pathogenic microbes could metabolize these compounds, which remains an avenue for further investigation. Investigating alternative metabolic pathways in microorganisms capable of growth using disinfectants as their sole carbon and energy source may provide insight into the metabolism of quaternary ammonium compound (QAC)-based antimicrobials. Many of the metabolic reactions proposed include hydroxylation, N-dealkylation, N-demethylation, and β-oxidation of QACs. If clear metabolic pathways and reactions are elucidated, possible alternative approaches to QACs may be advised. Alternatively, this may provide opportunities for biodegradation of the compounds that adversely affect the environment.

Impact of Peptidoglycan Recycling Blockade and Expression of Horizontally Acquired β-Lactamases on Pseudomonas aeruginosa Virulence

In the current scenario of antibiotic resistance magnification, new weapons against top nosocomial pathogens like Pseudomonas aeruginosa are urgently needed. The interplay between β-lactam resistance and virulence is considered a promising source of targets to be attacked by antivirulence therapies, and in this regard, we previously showed that a peptidoglycan recycling blockade dramatically attenuated the pathogenic power of P. aeruginosa strains hyperproducing the chromosomal β-lactamase AmpC. Here, we sought to ascertain whether this observation could be applicable to other β-lactamases. To do so, P. aeruginosa wild-type or peptidoglycan recycling-defective strains (ΔampG and ΔnagZ) harboring different cloned β-lactamases (transferable GES, VIM, and OXA types) were used to assess their virulence in Galleria mellonella larvae by determining 50% lethal doses (LD50s). A mild yet significant LD50 increase was observed after peptidoglycan recycling disruption per se, whereas the expression of class A and B enzymes did not impact virulence. While the production of the narrow-spectrum class D OXA-2 entailed a slight attenuation, its extended-spectrum derivatives OXA-226 (W159R [bearing a change of W to R at position 159]), OXA-161 (N148D), and principally, OXA-539 (D149 duplication) were associated with outstanding virulence impairments, especially in recycling-defective backgrounds (with some LD50s being >1,000-fold that of the wild type). Although their exact molecular bases remain to be deciphered, these results suggest that mutations affecting the catalytic center and, therefore, the hydrolytic spectrum of OXA-2-derived enzymes also drastically impact the pathogenic power of P. aeruginosa. This work provides new and relevant knowledge to the complex topic of the interplay between the production of β-lactamases and virulence that could be useful to build future therapeutic strategies against P. aeruginosa. IMPORTANCE Pseudomonas aeruginosa is one of the leading nosocomial pathogens whose growing resistance makes the development of therapeutic options extremely urgent. The resistance-virulence interplay has classically aroused researchers' interest as a source of therapeutic targets. In this regard, we describe a wide array of virulence attenuations associated with different transferable β-lactamases, among which the production of OXA-2-derived extended-spectrum β-lactamases stood out as a dramatic handicap for pathogenesis, likely as a side effect of mutations causing the expansion of their hydrolytic spectrums. Moreover, our results confirm the validity of disturbing peptidoglycan recycling as a weapon to attenuate P. aeruginosa virulence in class C and D β-lactamase production backgrounds. In the current scenario of dissemination of horizontally acquired β-lactamases, this work brings out new data on the complex interplay between the production of specific enzymes and virulence attenuation that, if complemented with the characterization of the underlying mechanisms, will likely be exploitable to develop future virulence-targeting antipseudomonal strategies.

Combined in-vitro and on-farm evaluation of commercial disinfectants used against Brachyspira hyodysenteriae

BACKGROUND

Swine dysentery (SD) is a severe infectious disease with a relevant impact on pig production usually caused by Brachyspira hyodysenteriae, although B. hampsonii causes an identical clinical picture. SD control relies on antimicrobials, good management practices and strict biosecurity with cleaning and disinfection as crucial tools to avoid the pathogen transmission. This study evaluates the in-vitro efficacy of an array of commercial disinfectants against a collection of B. hyodysenteriae isolates using broth tests. The efficacy of cleaning and disinfection protocols was also evaluated on two farms with endemic SD using surface swabs collected in emptied pens before and after cleaning and disinfection procedures, using both real-time PCR and bacterial microbiological culture.

RESULTS

Most of the commercial disinfectants evaluated were effective against all B. hyodysenteriae isolates tested, with a reduction of more than 5.00 log10 CFU/mL (bactericidal efficacy of 99.999%). However, some isolates exhibited reduced susceptibility to Virkon-S and Limoseptic disinfectants. The evaluation of cleaning and disinfection protocols on farms with SD outbreaks showed that approximately half the pens tested (n = 25) were positive by real-time PCR after pigs removal (mean B. hyodysenteriae counts 5.72 ± 1.04 log10 CFU/mL) while almost 20% of the pens remained positive after cleaning (n = 7) and disinfection (n = 5) procedures although with significantly lower, mean estimates (4.31 ± 0.43 log10 CFU/mL and 4.01 ± 0.55 log10 CFU/mL, respectively).

CONCLUSIONS

These results show the efficacy of disinfectants against B. hyodysenteriae but also stress the need to implement adequately the cleaning and disinfection protocols on pig farms and review and revise their efficiency periodically.

Antibacterial, Antifungal and Anticancer Activities of Compounds Produced by Newly Isolated Streptomyces Strains from the Szczelina Chochołowska Cave (Tatra Mountains, Poland)

Resistance of bacteria, fungi and cancer cells to antibiotics and other drugs is recognized as one of the major problems in current medicine. Therefore, a search for new biologically active compounds able to either kill pathogenic cells or inhibit their growth is mandatory. Hard-to-reach habitats appear to be unexplored sources of microorganisms producing previously unknown antibiotics and other molecules revealing potentially therapeutic properties. Caves belong to such habitats, and Actinobacteria are a predominant group of microorganisms occurring there. This group of bacteria are known for production of many antibiotics and other bioactive compounds. Interestingly, it was demonstrated previously that infection with bacteriophages might enhance production of antibiotics by them. Here, we describe a series of newly isolated strains of Actinobacteria that were found in caves from the Tatra Mountains (Poland). Phage induction tests indicated that some of them may bear active prophages able to produce virions upon treatment with mitomycin C or UV irradiation. Among all the examined bacteria, two newly isolated Streptomyces sp. strains were further characterized to demonstrate their ability to inhibit the growth of pathogenic bacteria (strains of Staphylococcus aureus, Salmonella enterica, Enterococcus sp., Escherichia coli, and Pseudomonas aeruginosa) and fungi (different species and strains from the genus Candida). Moreover, extracts from these Streptomyces strains reduced viability of the breast-cancer cell line T47D. Chemical analyses of these extracts indicated the presence of isomers of dichloranthrabenzoxocinone and 4,10- or 10,12-dichloro-3-O-methylanthrabenzoxocinone, which are putative antimicrobial compounds. Moreover, various previously unknown (unclassified) molecules were also detected using liquid chromatography-mass spectrometry, suggesting that tested Streptomyces strains may synthesize a battery of bioactive compounds with antibacterial, antifungal, and anticancer activities. These results indicate that further studies on the newly isolated Actinobacteria might be a promising approach to develop novel antibacterial, antifungal, and/or anticancer drugs.

Bacterial Outer Membrane Vesicles as a Versatile Tool in Vaccine Research and the Fight against Antimicrobial Resistance

Gram-negative bacteria include a number of pathogens that cause disease in humans and animals. Although antibiotics are still effective in treating a considerable range of infections caused by Gram-negative bacteria, the alarming increase of antimicrobial resistance (AMR) induced by excessive use of antibiotics has raised global concerns. Therefore, alternative strategies must be developed to prevent and treat bacterial infections and prevent the advent of a postantibiotic era. Vaccines, one of the greatest achievements in the history of medical science, hold extraordinary potential to prevent bacterial infections and thereby reduce the need for antibiotics. Novel bacterial vaccines are urgently needed, however, and outer membrane vesicles (OMVs), naturally produced by Gram-negative bacteria, represent a promising and versatile tool that can be employed as adjuvants, antigens, and delivery platforms in the development of vaccines against Gram-negative bacteria. Here, we provide an overview of the many roles OMVs can play in vaccine development and the mechanisms behind these applications. Methods to improve OMV yields and a comparison of different strategies for OMV isolation aiming at cost-effective production of OMV-based vaccines are also reviewed.

There is no market for new antibiotics: this allows an open approach to research and development

There is an increasingly urgent need for new antibiotics, yet there is a significant and persistent economic problem when it comes to developing such medicines. The problem stems from the perceived need for a "market" to drive commercial antibiotic development. In this article, we explore abandoning the market as a prerequisite for successful antibiotic research and development. Once one stops trying to fix a market model that has stopped functioning, one is free to carry out research and development (R&D) in ways that are more openly collaborative, a mechanism that has been demonstrably effective for the R&D underpinning the response to the COVID pandemic. New "open source" research models have great potential for the development of medicines for areas of public health where the traditional profit-driven model struggles to deliver. New financial initiatives, including major push/pull incentives, aimed at fixing the broken antibiotics market provide one possible means for funding an openly collaborative approach to drug development. We argue that now is therefore the time to evaluate, at scale, whether such methods can deliver new medicines through to patients, in a timely manner.

The antiseptic Miramistin: a review of its comparative in vitro and clinical activity

Miramistin is a topical antiseptic with broad antimicrobial action, including activity against biofilms and a clinical profile showing good tolerability. Miramistin was developed within a framework of the Soviet Union Cold War Space Program. It is available for clinical use in several prior Soviet bloc countries, but barely known outside of these countries and there is almost no mention of miramistin in the English literature. However, considering emerging antimicrobial resistance, the significant potential of miramistin justifies its re-evaluation for use in other geographical areas and conditions. The review consists of two parts: (i) a review of the existing literature on miramistin in English, Russian and Ukrainian languages; (ii) a summary of most commonly used antiseptics as comparators of miramistin. The oral LD50 was 1200 mg/kg, 1000 mg/kg and 100 g/L in rats, mice and fish, respectively. Based on the results of the review, we suggest possible applications of miramistin and potential benefits over currently used agents. Miramistin offers a novel, low toxicity antiseptic with many potential clinical uses that need better study which could address some of the negative impact of antimicrobial, antiseptic and disinfectant resistance.

Ketone- and Cyano-Selenoesters to Overcome Efflux Pump, Quorum-Sensing, and Biofilm-Mediated Resistance

The emergence of drug-resistant pathogens leads to a gradual decline in the efficacy of many antibacterial agents, which poses a serious problem for proper therapy. Multidrug resistance (MDR) mechanisms allow resistant bacteria to have limited uptake of drugs, modification of their target molecules, drug inactivation, or release of the drug into the extracellular space by efflux pumps (EPs). In previous studies, selenoesters have proved to be promising derivatives with a noteworthy antimicrobial activity. On the basis of these results, two series of novel selenoesters were synthesized to achieve more potent antibacterial activity on Gram-positive and Gram-negative bacteria. Fifteen selenoesters (eight ketone-selenoesters and seven cyano-selenoesters) were investigated with regards to their efflux pump-inhibiting, anti-quorum-sensing (QS), and anti-biofilm effects in vitro. According to the results of the antibacterial activity, the ketone-selenoesters proved to be more potent antibacterial compounds than the cyano-selenoesters. With regard to efflux pump inhibition, one cyano-selenoester on methicillin-resistant S. aureus and one ketone-selenoester on Salmonella Typhimurium were potent inhibitors. The biofilm inhibitory capacity and the ability of the derivatives to disrupt mature biofilms were noteworthy in all the experimental systems applied. Regarding QS inhibition, four ketone-selenoesters and three cyano-selenoesters exerted a noteworthy effect on Vibrio campbellii strains.

Antibacterial nanotruffles for treatment of intracellular bacterial infection

Bacterial pathogens residing in host macrophages in intracellular infections are hard to eradicate because traditional antibiotics do not readily enter the cells or get eliminated via efflux pumps. To overcome this challenge, we developed a new particle formulation with a size amenable to selective macrophage uptake, loaded with two antibacterial agents - pexiganan and silver (Ag) nanoparticles. Here, pexiganan was loaded in 600 nm poly(lactic-co-glycolic acid) (PLGA) particles (NP), and the particle surface was modified with an iron-tannic acid supramolecular complex (pTA) that help attach Ag nanoparticles. PLGA particles coated with Ag (NP-pTA-Ag) were taken up by macrophages, but not by non-phagocytic cells, such as fibroblasts, reducing non-specific toxicity associated with Ag nanoparticles. NP-pTA-Ag loaded with pexiganan (Pex@NP-pTA-Ag) showed more potent antibacterial activity against various intracellular pathogens than NP-pTA-Ag or Pex@NP (pexiganan-loaded NP with no Ag), suggesting a collaborative function between pexiganan and Ag nanoparticles. Mouse whole-body imaging demonstrated that, upon intravenous injection, NP-pTA-Ag quickly accumulated in the liver and spleen, where intracellular bacteria tend to reside. These results support that Pex@NP-pTA-Ag is a promising strategy for the treatment of intracellular bacterial infection.

ISG15 Acts as a Mediator of Innate Immune Response to Pseudomonas aeruginosa Infection in C57BL/6J Mouse Corneas

Purpose

IFN-stimulated gene (ISG) 15 is a type 1 IFN-induced protein and known to modify target proteins in a manner similar to ubiquitylation (protein conjugation by ISG15 is termed ISGylation). We sought to determine the role of ISG15 and its underlying mechanisms in corneal innate immune defense against Pseudomonas aeruginosa keratitis.

Methods

ISG15 expression in cultured human corneal epithelial cells (HCECs) and mouse corneas was determined by PCR and Western blot analysis. Gene knockout mice were used to define the role of ISG15 signaling in controlling the severity of P. aeruginosa keratitis, which was assessed with photographing, clinical scoring, bacterial counting, myeloperoxidase assay, and quantitative PCR determination of cytokine expression. Integrin LFA-1 inhibitor was used to assess its involvement of ISG15 signaling in P. aeruginosa-infected corneas.

Results

Heat-killed P. aeruginosa induced ISG15 expression in cultured HCECs and accumulation in the conditioned media. Isg15 deficiency accelerated keratitis progress, suppressed IFNγ and CXCL10, and promoted IL-1β while exhibiting no effects on IFNα expression. Moreover, exogenous ISG15 protected the corneas of wild-type mice from P. aeruginosa infection while markedly reducing the severity of P. aeruginosa keratitis in type 1 IFN-receptor knockout mice. Exogenous ISG15 increased bacteriostatic activity of B6 mouse corneal homogenates, and inhibition of LFA-1 exacerbated the severity of and abolished protective effects of ISG15 on P. aeruginosa keratitis.

Conclusions

Type 1 INF-induced ISG15 regulates the innate immune response and greatly reduces the susceptibility of B6 mouse corneas to P. aeruginosa infection in an LFA-1-dependent manner.

In vitro and in vivo efficacy of combinations of colistin and different endolysins against clinical strains of multi-drug resistant pathogens

The emergence of multidrug resistant (MDR) pathogenic bacteria is jeopardizing the value of antimicrobials, which had previously changed the course of medical science. In this study, we identified endolysins ElyA1 and ElyA2 (GH108-PG3 family), present in the genome of bacteriophages Ab1051Φ and Ab1052Φ, respectively. The muralytic activity of these endolysins against MDR clinical isolates (Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae) was tested using the turbidity reduction assay. Minimal inhibitory concentrations (MICs) of endolysin, colistin and a combination of endolysin and colistin were determined, and the antimicrobial activity of each treatment was confirmed by time kill curves. Endolysin ElyA1 displayed activity against all 25 strains of A. baumannii and P. aeruginosa tested and against 13 out of 17 strains of K. pneumoniae. Endolysin ElyA2 did not display any such activity. The combined antimicrobial activity of colistin and ElyA1 yielded a reduction in the colistin MIC for all strains studied, except K. pneumoniae. These results were confirmed in vivo in G. mellonella survival assays and in murine skin and lung infection models. In conclusion, combining colistin (1/4 MIC) with the new endolysin ElyA1 (350 µg) enhanced the bactericidal activity of colistin in both in vitro and in vivo studies. This will potentially enable reduction of the dose of colistin used in clinical practice.

Investigating Bacteriophages Targeting the Opportunistic Pathogen Acinetobacter baumannii

The multi-drug resistance of the opportunistic pathogen Acinetobacter baumannii is of growing concern, with many clinical isolates proving to be resistant to last resort as well as front line antibiotic treatments. The use of bacteriophages is an attractive alternative to controlling and treating this emerging nosocomial pathogen. In this study, we have investigated bacteriophages collected from hospital wastewater in Thailand and we have explored their activity against clinical isolates of A. baumannii. Bacteriophage vB_AbaM_PhT2 showed 28% host range against 150 multidrug resistant (MDR) isolates and whole genome sequencing did not detect any known virulence factors or antibiotic resistance genes. Purified vB_AbaM_PhT2 samples had endotoxin levels below those recommended for preclinical trials and were not shown to be directly cytotoxic to human cell lines in vitro. The treatment of human brain and bladder cell lines grown in the presence of A. baumannii with this bacteriophage released significantly less lactate dehydrogenase compared to samples with no bacteriophage treatment, indicating that vB_AbaM_PhT2 can protect from A. baumannii induced cellular damage. Our results have also indicated that there is synergy between this bacteriophage and the end line antibiotic colistin. We therefore propose bacteriophage vB_AbaM_PhT2 as a good candidate for future research and for its potential development into a surface antimicrobial for use in hospitals.

Concanavalin A-targeted mesoporous silica nanoparticles for infection treatment

The ability of bacteria to form biofilms hinders any conventional treatment for chronic infections and has serious socio-economic implications. For this purpose, a nanocarrier capable of overcoming the barrier of the mucopolysaccharide matrix of the biofilm and releasing its loaded-antibiotic within this matrix would be desirable. Herein, we developed a new nanosystem based on levofloxacin (LEVO)-loaded mesoporous silica nanoparticles (MSN) decorated with the lectin concanavalin A (ConA). The presence of ConA promotes the internalization of this nanosystem into the biofilm matrix, which increases the antimicrobial efficacy of the antibiotic hosted within the mesopores. This nanodevice is envisioned as a promising alternative to conventional treatments for infection by improving the antimicrobial efficacy and reducing side effects. STATEMENT OF SIGNIFICANCE: The present study is focused on finding an adequate therapeutic solution for the treatment of bone infection using nanocarriers that are capable of overcoming the biofilm barrier by increasing the therapeutic efficacy of the loaded antibiotic. For this purpose, we present a nanoantibiotic that increases the effectiveness of levofloxacin to destroy the biofilm formed by the model bacterium E. coli. This work opens new lines of research in the treatment of chronic infections based on nanomedicines.

Novel approach to combat antibiotic resistance: evaluation of some Armenian herb crude extracts for their antibiotic modulatory and antiviral properties

AIMS

One of the strategies to combat antibiotic resistance can be the use of plant materials in combination with antibiotics, taking into account that phytochemicals can act as antibiotic resistance-modifying agents. This can give a second life to the traditional antibiotics. The aim was to evaluate antibiotic modulatory effect of crude extracts from Agrimonia eupatoria, Hypericum alpestre, Rumex obtusifolius and Sanguisorba officinalis herbs towards several commercial antibiotics using some Gram-positive and Gram-negative bacteria.

METHODS

The antibiotic modulatory activity was tested by determining MICs of antibiotics in the absence and presence of plant crude extracts at subinhibitory concentrations. Antiviral potential of different extracts of tested plant materials was also explored by double overlay plaque assay.

RESULTS

The tested plant crude extracts exhibited high modulatory activity towards used antibiotics. Particularly, high modulatory activity was observed with extracts of H. alpestre and R. obtusifolius. Many plant-antibiotic combinations induced the decrease in MICs of antibiotics up to ~fourfold indicating synergy. Moreover, the similar change was observed at both subinhibitory concentrations (MIC/2 and MIC/4) of the same plant crude extract. High anti-phage activity of plants with the exception of Lilium armenum against T4 phage of Escherichia coli C-T4 was also shown.

CONCLUSIONS

Plant crude extract or commercial antibiotic combinations significantly increased the efficiency of antibiotics. Tested plant materials with exception of L. armenum have antiviral property.

SIGNIFICANCE AND IMPACT OF THE STUDY

For the first time, antibiotic modulatory activity of tested herb extracts was shown, which could have potential in practical applications. Tested plant materials with exception of L. armenum could have prospective, as a source of new antiviral compounds.

BD-2 and BD-3 increase skin flap survival in a model of ischemia and Pseudomonas aeruginosa infection

The main aim of this work was to study the usefulness of human β-defensins 2 (BD-2) and 3 (BD-3), which are part of the innate immune system, in the treatment of infected ischemic skin flaps. We investigated the effect of transducing rat ischemic skin flaps with lentiviral vectors encoding human BD-2, BD-3, or both BD-2 and BD-3, to increase flap survival in the context of a P. aeruginosa infection associated with a foreign body. The secondary endpoints assessed were: bacterial counts, and biofilm formation on the surface of the foreign body. A local ischemic environment was created by producing arterialized venous flaps in the left epigastric region of rats. Flaps were intentionally infected by placing underneath them two catheters with 105 CFU of P. aeruginosa before the surgical wounds were hermetically closed. Flap biopsies were performed 3 and 7 days post-operatively, and the specimens submitted to immunohistochemical analysis for BD-2 and BD-3, as well as to bacterial quantification. Subsequently, the catheter segments were analyzed with scanning electron microscopy (SEM). Flaps transduced with BD-2 and BD-3 showed expression of these defensins and presented increased flap survival. Rats transduced with BD-3 presented a net reduction in the number of P. aeruginosa on the surface of the foreign body and lesser biofilm formation.

Connecting iron acquisition and biofilm formation in the ESKAPE pathogens as a strategy for combatting antibiotic resistance

The rise of antibiotic resistant bacteria has become a problem of global concern. Of particular interest are the ESKAPE pathogens, species with high rates of multi-drug resistant infections. Novel antibiotic mechanisms of action are necessary to compliment traditional therapeutics. Recent research has focused on targeting virulence factors as a method of combatting infection without creating selective pressure for resistance or damaging the host commensal microbiome. Some investigations into one such virulence behavior, iron acquisition, have displayed additional effects on another virulence behavior, biofilm formation. The use of exogenous iron-chelators, gallium as an iron mimic, and inhibition of siderophore-mediated iron acquisition are all strategies for disturbing iron-homeostasis that have implicated effects on biofilms. However, the exact nature of this connection remains ambiguous. Herein we summarize these findings and identify opportunities for further investigation.

An Innovative Strategy for the Effective Reduction of MDR Pathogens from the Nosocomial Environment

Antimicrobial resistance (AMR) is currently one of the main concerns for human health.Due to its rapid increase and global diffusion, several common microbial infections might become not curable in the future decades, making it impossible to apply other lifesaver therapies, such as transplant or chemotherapy.AMR is frequently observed in hospital pathogens, due to selective pressure exerted by antibiotic use, and consistently with this, in the recent years, many actions have been proposed to limit AMR spread, including hygiene measures for hospital professionals and a wiser antibiotic usage.Indeed, the hospital environment itself represents a reservoir of pathogens, whose control was so far addressed by conventional sanitation procedures, which however cannot prevent recontamination and might further favour the selection of resistant strains.Here we report the results collected by studying an innovative sanitation strategy based on the use of probiotic bacteria, capable of reducing in a stable way the surface load of pathogens and their AMR. Collected data suggest that this system might contribute significantly to AMR control and might be thus considered as one of the tools for AMR and infection prevention and control.