Mycological evaluation of frozen meat with special reference to yeasts.

Background and Aim: Fungi can play beneficial and detrimental roles in meat products; however, the diversity and significance of fungi in meat products are poorly understood. This study aimed to isolate and characterize fungal species from frozen beef samples collected from retail stores in the Qena Governorate, Egypt. Materials and Methods: A total of 70 frozen beef samples were collected from retail stores in Qena, Egypt. All samples were subjected to mycological examination. Fungal colonies were identified using conventional approaches, as well as the VITEK 2 system and DNA sequencing of the internal transcribed spacer region. Analyses of enzymatic activity, biofilm formation ability, and the antimicrobial resistance profiles of the isolated yeasts were also conducted. Results: Molds and yeasts were isolated from 40% and 60% of meat samples, respectively. Mold isolates were dominated by Aspergillus, Penicillium, and Cladosporium spp., whereas yeast isolates were identified as Candida albicans, Candida parapsilosis, Yarrowia lipolytica, Saccharomyces cerevisiae, and Rhodotorula mucilaginosa. Compared to other yeast species, the highest production of lipase and protease was observed in Candida species. The strongest ability to form biofilms was observed in Candida spp., followed by S. cerevisiae, Y. lipolytica, and R. mucilaginosa. The results of antimicrobial susceptibility testing revealed that all yeast isolates showed notable resistance to fluconazole and itraconazole. Conclusion: A significant correlation between antimicrobial resistance and biofilm formation was observed in several species. This study highlights the importance of the dangers of yeasts in food products and the extent of their impact on public health.

Detection of ß-Lactamase Resistance and Biofilm Genes in Pseudomonas Species Isolated from Chickens.

Bacteria of the genus Pseudomonas are pathogens in both humans and animals. The most prevalent nosocomial pathogen is P. aeruginosa, particularly strains with elevated antibiotic resistance. In this study, a total of eighteen previously identified Pseudomonas species strains, were isolated from chicken. These strains were screened for biofilm formation and antibiotic resistance. In addition, we evaluated clove oil's effectiveness against Pseudomonas isolates as an antibiofilm agent. The results showed that Pseudomonas species isolates were resistant to most antibiotics tested, particularly those from the ß-lactamase family. A significant correlation (p < 0.05) between the development of multidrug-resistant isolates and biofilms is too informal. After amplifying the AmpC-plasmid-mediated genes (blaCMY, blaMIR, DHA, and FOX) and biofilm-related genes (psld, rhlA, and pelA) in most of our isolates, PCR confirmed this relationship. Clove oil has a potent antibiofilm effect against Pseudomonas isolates, and may provide a treatment for bacteria that form biofilms and are resistant to antimicrobials.

Molecular characterization of Escherichia coli isolated from milk samples with regard to virulence factors and antibiotic resistance.

BACKGROUND AND AIM: Raw milk is considered an essential source of nutrition during all stages of human life because it offers a valuable supply of protein and minerals. Importantly, milk is considered a good media for the growth and contamination of many pathogenic bacteria, especially food-borne pathogens such as Escherichia coli. Thus, the objective of this study was to characterize E. coli and detect its virulence factors and antibiotic resistance from raw milk samples. MATERIALS AND METHODS: Raw milk samples (n=100) were collected from different localities in Qena, Egypt, and investigated for the presence of E. coli using different biochemical tests, IMViC tests, serotyping to detect somatic antigen type, and molecularly by polymerase chain reaction (PCR) tests. The presence of different virulence and antimicrobial genes (hly, eae, stx1, stx2, blaTEM, tetA(A), and tetB genes) in E. coli isolates was evaluated using PCR. RESULTS: The results demonstrated that 10 out of 100 milk samples were contaminated with E. coli. Depending on serology, the isolates were classified as O114 (one isolate), O27 (two isolates), O111 (one isolate), O125 (two isolates), and untypeable (five isolates) E. coli. The sequencing of partially amplified 16S rRNA of the untypeable isolates resulted in one isolate, which was initially misidentified as untypeable E. coli but later proved as Enterobacter hormaechei. Moreover, antibacterial susceptibility analysis revealed that nearly all isolates were resistant to more than 3 families of antibiotics, particularly to b-lactams, clindamycin, and rifampin. PCR results demonstrated that all E. coli isolates showed an accurate amplicon for the blaTEM and tetA(A) genes, four isolates harbored eae gene, other four harbored tetB gene, and only one isolate exhibited a positive stx2 gene. CONCLUSION: Our study explored vital methods for identifying E. coli as a harmful pathogen of raw milk using 16S rRNA sequencing, phylogenetic analysis, and detection of virulence factors and antibiotic-resistant genes.

Control of Virulent Listeria monocytogenes Originating from Dairy Products and Cattle Environment Using Marine Algal Extracts, Silver Nanoparticles Thereof, and Quaternary Disinfectants.

INTRODUCTION: Listeria monocytogenes is an important foodborne pathogen of public- and animal-health concern globally. The persistence of L. monocytogenes in the dairy-processing environment has multifactorial causes, including lack of hygiene, inefficient cleaning, and improper disinfection practices. MATERIALS AND METHODS: A total of 300 dairy-product and environmental samples were collected from dairy-cattle facilities and local dairy shops and vendors in Qena, Egypt. Samples were screened for the incidence of Listeria spp. and to detect virulence determinants and disinfectant-resistance genes. Three marine algal species - Caulerpa racemosa, Jania rubens, and Padina pavonica - were collected from Hurghada on the Red Sea coast. Algal extracts were screened using gas chromatography-mass spectrometry. The antimicrobial activity of some marine algal extracts, nanoparticles derived therefrom, and some disinfectants against L. monocytogenes strains were assessed in vitro using agar-well diffusion and liquid-broth methods. The impact of P. pavonica extract on the growth and survival of virulent L. monocytogenes in cheese and whey were clarified. RESULTS AND DISCUSSION: The incidence of L. monocytogenes in dairy products and environmental samples was 15.5% and 19%, respectively. The most common toxigenic gene profile found among the isolates was hlyA +-inlA +-prfA +. The sensitivity pattern of L. monocytogenes strains to disinfectant containing alkyl (C12-16) dimethyl BAC was high compared to other tested quaternary ammonium compounds (QAC) disinfectants tested, which showed lower log reductions against resistant strains. The QAC disinfectant-resistance gene qacH was detected in 40% of the isolates. Potent bactericidal activity of a petroleum ether extract of P. pavonica and silver nanoparticles of P. pavonica were obtained against the virulent L. monocytogenes strain. The population of L. monocytogenes in cheese curd and whey after 14 days was reduced at a rate of 9 log CFU/g and 8 log CFU/mL, respectively due to the effect of P. pavonica extract. After 28 days of storage, L. monocytogenes was completely inactivated in those dairy products. CONCLUSION: P. pavonica extract showed promising antimicrobial properties, calling for further comprehensive studies prior to it being applied in the food industry to enhance the safety, quality, and shelf life of products and protect public health.

An Overview of SARS-CoV-2 and Animal Infection.

A novel coronavirus has been reported as the causative pathogen of the Coronavirus disease 2019 (COVID-19) outbreak in Wuhan city, China in December 2019. Due to the rapid spread of the virus worldwide, it has been announced as a pandemic by the World Health Organization (WHO). Hospitalized patients in Wuhan were associated with the Huanan seafood wholesale market where live animals, such as poultry, bats, snakes, frogs, rabbits, marmots, and hedgehogs are sold in that market which suggests a possible zoonotic infection. It was suggested that bat is the natural host of SARS-CoV-2, but the intermediate host is still unclear. It is essential to identify the potential intermediate host to interrupt the transmission chain of the virus. Pangolin is a highly suspected candidate as an intermediate host for SARS-CoV-2. Recently, SARS-CoV-2 infection has been reported in cats, dogs, tigers, and lions. More recently SARS-CoV-2 infection affected minks severely and zoonotic transfer with a variant SARS-CoV-2 strain evidenced in Denmark, Netherlands, USA, and Spain suggesting animal-to-human and animal-to-animal transmission within mink farms. Furthermore, experimental studies documented the susceptibility of different animal species to SARS-CoV-2, such as mice, golden hamsters, cats, ferrets, non-human primates, and treeshrews. It is also essential to know the possibility of infection for other animal species. This short review aims to provide an overview on the relation between severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection and animals.

Enhanced Microbial Decontamination Using Non-thermal Low Pressure Argon Plasma Jet.

BACKGROUND AND OBJECTIVE: Atmospheric pressure plasma jet (APPJ) gained great interest due to its effectiveness as selective non-lethal technique with low operational costs. In this study, argon APPJ system was designed and the generated cold plasma was applied in disinfection of microbial cells. MATERIALS AND METHODS: Argon APPJ was generated by blowing argon through capillary metallic tube inserted in alumina and powered by 8-25 kHz sinusoidal voltage waveform. The plasma applied in inactivation of microbes by direct exposure of cell suspension, approximately 10 mm below jet nozzle, for different intervals. Interference of organics in exposure medium, on lethal activity of plasma was investigated. RESULTS: APPJ jet induced high levels of reactive oxygen (ROS) and nitrogen species (RNS). Jet length increased with applied voltage and flow rate in laminar mode, but decreased with flow rate in turbulent mode. Percent reduction in living cell count was 98.3 and 94.1%, for E. coli and S. aureus suspended in water after 30s of exposure, respectively, with 2.7- and 2-folds increase in plasma lethal activity, as compared with LB broth medium. D-values (Decimal Reduction Time) were increased from 34-333, 37-476 and 139-385 s for E. coli, S. aureus and C. albicans in water and complex liquid organic media, respectively. CONCLUSION: Designed argon APPJ system can be used in disinfection of different microbes. Plasma antimicrobial activity drastically decreased in presence of organic matter. The generated plasma can be promising approach for treatment of diseases, especially caused by antibiotic-resistant pathogens.

Rapid Uptake and Photodynamic Inactivation of Staphylococci by Ga(III)-Protoporphyrin IX.

Antimicrobial photodynamic therapy (aPDT) is a promising method for the topical treatment of drug-resistant staphylococcal infections and can be further improved by identifying mechanisms that increase the specificity of photosensitizer uptake by bacteria. Here we show that Ga(III)-protoporphyrin IX chloride (Ga-PpIX), a fluorescent hemin analog with previously undisclosed photosensitizing properties, can be taken up within seconds by Staphylococcus aureus including multidrug-resistant strains such as MRSA. The uptake of Ga-PpIX by staphylococci is likely diffusion-limited and is attributed to the expression of high-affinity cell-surface hemin receptors (CSHRs), namely iron-regulated surface determinant (Isd) proteins. A structure-activity study reveals the ionic character of both the heme center and propionyl groups to be important for uptake specificity. Ga-PpIX was evaluated as a photosensitizer against S. aureus and several clinical isolates of MRSA using a visible light source, with antimicrobial activity at 0.03 µM with 10 s of irradiation by a 405 nm diode array (1.4 J/cm2); antimicrobial activity could also be achieved within minutes using a compact fluorescent lightbulb. GaPpIX was not only many times more potent than PpIX, a standard photosensitizer featured in clinical aPDI, but also demonstrated low cytotoxicity against HEK293 cells and human keratinocytes. Ga-PpIX uptake was screened against a diverse panel of bacterial pathogens using a fluorescence-based imaging assay, which revealed rapid uptake by several Gram-positive species known to express CSHRs, suggesting future candidates for targeted aPDT.

Antibacterial activity and safety of commercial veterinary cationic steroid antibiotics and neutral superoxidized water.

Antibiotic resistance of bacteria common to the ocular surface is an evolving problem. Thus, novel treatment options with new modes of action are required. We investigated the antibacterial activity and safety of three commercially available topical veterinary ophthalmic products (cationic steroid antibiotics, products A and B, and a neutral superoxidized water, product C) to determine their potential use as antimicrobial alternatives. The minimum inhibitory concentrations (MIC) of the three products were determined against 17 antibiotic resistant bacterial clinical isolates from the ocular surface. Using a standard cytotoxicity assay, the products at varying concentrations were evaluated with a corneal fibroblast cell line and a macrophage-like cell line to determine their potential toxic effect in vitro. The commercial ophthalmic solutions, ofloxacin 0.3%, tobramycin 0.3% and gentamicin 0.3% were used as positive controls for the MIC and tobramycin 0.3% was used as positive control for the cytotoxicity assays. For the MIC, Product C showed no inhibition of growth for any organisms, while Products A and B showed inhibition of growth similar to slightly less than the positive controls. For the cytotoxicity assays, Product C exhibited minimal toxicity while Products A and B exhibited toxicity similar to the controls. In conclusion, Product C had no antibacterial activity in these assays, while Products A and B had antibacterial profiles similar to slightly less than common topical ophthalmic antibiotics and cytotoxicity profiles similar to common topical ophthalmic antibiotics. To our knowledge, this is the first report on the antibacterial activity and safety of the cationic steroid antibiotics and superoxidized water.

Antibiotic Susceptibility Determination within One Cell Cycle at Single-Bacterium Level by Stimulated Raman Metabolic Imaging.

The widespread use of antibiotics has significantly increased the number of resistant bacteria, which has also increased the urgency of rapid bacterial detection and profiling their antibiotic response. Current clinical methods for antibiotic susceptibility testing (AST) rely on culture and require at least 16 to 24 h to conduct. Therefore, there is an urgent need for a rapid method that can test the susceptibility of bacteria in a culture-free manner. Here we demonstrate a rapid AST method by monitoring the glucose metabolic activity of live bacteria at the single-cell level with hyperspectral stimulated Raman scattering (SRS) imaging. Using vancomycin-susceptible and -resistant enterococci E. faecalis as models, we demonstrate that the metabolic uptake of deuterated glucose in a single living bacterium can be quantitatively monitored via hyperspectral SRS imaging. Remarkably, the metabolic activity of susceptible bacteria responds differently to antibiotics from the resistant strain within only 0.5 h from the addition of antibiotics. Therefore, bacterial susceptibility and the minimum inhibitory concentration (MIC) of antibiotics can be determined within one cell cycle. Our metabolic imaging method is applicable to other bacteria species including E. coli, K. Pneumoniae, and S. aureus as well as different antibiotics, regardless of their mechanisms of inhibiting or killing bacteria.

Discovery of a Novel Dibromoquinoline Compound Exhibiting Potent Antifungal and Antivirulence Activity That Targets Metal Ion Homeostasis.

Globally, invasive fungal infections pose a significant challenge to modern human medicine due to the limited number of antifungal drugs and the rise in resistance to current antifungal agents. A vast majority of invasive fungal infections are caused by species of Candida, Cryptococcus, and Aspergillus. Novel antifungal molecules consisting of unexploited chemical scaffolds with a unique mechanism are a pressing need. The present study identifies a dibromoquinoline compound (4b) with broad-spectrum antifungal activity that inhibits the growth of pertinent species of Candida (chiefly C. albicans), Cryptococcus, and Aspergillus at a concentration of as low as 0.5 µg/mL. Furthermore, 4b, at a subinhibitory concentration, interfered with the expression of two key virulence factors (hyphae and biofilm formation) involved in C. albicans pathogenesis. Three yeast deletion strains ( cox17Δ, ssa1Δ, and aft2Δ) related to metal ion homeostasis were found to be highly sensitive to 4b in growth assays, indicating that the compound exerts its antifungal effect through a unique, previously unexploited mechanism. Supplementing the media with either copper or iron ions reversed the strain sensitivity to 4b, further corroborating that the compound targets metal ion homeostasis. 4b's potent antifungal activity was validated in vivo, as the compound enhanced the survival of Caenorhabditis elegans infected with fluconazole-resistant C. albicans. The present study indicates that 4b warrants further investigation as a novel antifungal agent.

Stimulated Raman Imaging Reveals Aberrant Lipogenesis as a Metabolic Marker for Azole-Resistant Candida albicans.

Candida albicans is the single most prevalent cause of fungal bloodstream infections worldwide causing significant mortality as high as 50 percent. This high mortality rate is, in part, due to the inability to initiate an effective antifungal therapy early in the disease process. Mortality rates significantly increase after 12 hours of delay in initiating the appropriate antifungal therapy following a positive blood culture. Early administration of appropriate antifungal therapy is hampered by the slow turnovers of the conventional antimicrobial testing techniques, which require days of incubation. To address this unmet need, we explored the potential of employing stimulated Raman scattering (SRS) imaging to probe for metabolic differences between fluconazole-susceptible and -resistant strains at a single cell level in search of a metabolic signature. Metabolism is integral to pathogenicity. Since only a few hours are needed to observe a full metabolic cycle in C. albicans, metabolic profiling provides an avenue for rapid antimicrobial susceptibility testing. C-H frequency (2850 cm-1) SRS imaging revealed a substantial difference in lipogenesis between the fluconazole-susceptible and -resistant C. albicans. Exposure to fluconazole, an antimicrobial drug that targets ergosterol biosynthesis, only affected the lipogenesis in the susceptible strain. These results show that single cell metabolic imaging via SRS microscopy can be used for rapid detection of antimicrobial susceptibility.

Bacteriological profiling of diphenylureas as a novel class of antibiotics against methicillin-resistant Staphylococcus aureus.

Bacterial resistance to antibiotics remains an imposing global public health challenge. Of the most serious pathogens, methicillin-resistant Staphylococcus aureus (MRSA) is problematic given strains have emerged that exhibit resistance to several antibiotic classes including ß-lactams and agents of last resort such as vancomycin. New antibacterial agents composed of unique chemical scaffolds are needed to counter this public health challenge. The present study examines two synthetic diphenylurea compounds 1 and 2 that inhibit growth of clinically-relevant isolates of MRSA at concentrations as low as 4 µg/mL and are non-toxic to human colorectal cells at concentrations up to 128 µg/mL. Both compounds exhibit rapid bactericidal activity, completely eliminating a high inoculum of MRSA within four hours. MRSA mutants exhibiting resistance to 1 and 2 could not be isolated, indicating a low likelihood of rapid resistance emerging to these compounds. Bacterial cytological profiling revealed the diphenylureas exert their antibacterial activity by targeting bacterial cell wall synthesis. Both compounds demonstrate the ability to resensitize vancomycin-resistant Staphylococcus aureus to the effect of vancomycin. The present study lays the foundation for further investigation and development of diphenylurea compounds as a new class of antibacterial agents.

Investigation of aryl isonitrile compounds with potent, broad-spectrum antifungal activity.

Invasive fungal infections present a formidable global public health challenge due to the limited number of approved antifungal agents and the emergence of resistance to the frontline treatment options, such as fluconazole. Three fungal pathogens of significant concern are Candida, Cryptococcus, and Aspergillus given their propensity to cause opportunistic infections in immunocompromised individuals. New antifungal agents composed of unique chemical scaffolds are needed to address this public health challenge. The present study examines the structure-activity relationship of a set of aryl isonitrile compounds that possess broad-spectrum antifungal activity primarily against species of Candida and Cryptococcus. The most potent derivatives are capable of inhibiting growth of these key pathogens at concentrations as low as 0.5µM. Remarkably, the most active compounds exhibit an excellent safety profile and are non-toxic to mammalian cells even at concentrations up to 256µM. The present study lays the foundation for further investigation of aryl isonitrile compounds as a new class of antifungal agents.

Phenylthiazole Antibacterial Agents Targeting Cell Wall Synthesis Exhibit Potent Activity in Vitro and in Vivo against Vancomycin-Resistant Enterococci.

The emergence of antibiotic-resistant bacterial species, such as vancomycin-resistant enterococci (VRE), necessitates the development of new antimicrobials. Here, we investigate the spectrum of antibacterial activity of three phenylthiazole-substituted aminoguanidines. These compounds possess potent activity against VRE, inhibiting growth of clinical isolates at concentrations as low as 0.5 µg/mL. The compounds exerted a rapid bactericidal effect, targeting cell wall synthesis. Transposon mutagenesis suggested three possible targets: YubA, YubB (undecaprenyl diphosphate phosphatase (UPPP)), and YubD. Both UPPP as well as undecaprenyl diphosphate synthase were inhibited by compound 1. YubA and YubD are annotated as transporters and may also be targets because 1 collapsed the proton motive force in membrane vesicles. Using Caenorhabditis elegans, we demonstrate that two compounds (1, 3, at 20 µg/mL) retain potent activity in vivo, significantly reducing the burden of VRE in infected worms. Taken altogether, the results indicate that compounds 1 and 3 warrant further investigation as novel antibacterial agents against drug-resistant enterococci.

Diphenylurea derivatives for combating methicillin- and vancomycin-resistant Staphylococcus aureus.

A new class of diphenylurea was identified as a novel antibacterial scaffold with an antibacterial spectrum that includes highly resistant staphylococcal isolates, namely methicillin- and vancomycin-resistant Staphylococcus aureus (MRSA & VRSA). Starting with a lead compound 3 that carries an aminoguanidine functionality from one side and a n-butyl moiety on the other ring, several analogues were prepared. Considering the pharmacokinetic parameters as a key factor in structural optimization, the structure-activity-relationships (SARs) at the lipophilic side chain were rigorously examined leading to the discovery of the cycloheptyloxyl analogue 21n as a potential drug-candidate. This compound has several notable advantages over vancomycin and linezolid including rapid killing kinetics against MRSA and the ability to target and reduce the burden of MRSA harboring inside immune cells (macrophages). Furthermore, the potent anti-MRSA activity of 21n was confirmed in vivo using a Caenorhabditis elegans animal model. The present study provides a foundation for further development of diphenylurea compounds as potential therapeutic agents to address the burgeoning challenge of bacterial resistance to antibiotics.

In Vitro Screening of an FDA-Approved Library Against ESKAPE Pathogens.

Bacterial resistance to conventional antibiotics is an increasingly serious threat to public health worldwide that requires immediate exploration and the development of novel antimicrobial compounds. Drug repurposing is an inexpensive and untapped source of new antimicrobial leads, and it holds many attractive features warranting further attention for antimicrobial drug discovery. In an effort to repurpose drugs and explore new leads in the field of antimicrobial drug discovery, we performed a whole-cell screening assay of 1,600 Food and Drug Administration (FDA) approved drugs against Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter cloacae (ESKAPE) pathogens. The in vitro screening identified 49 non-antimicrobial drugs that were active against at least one species of ESKAPE pathogen. Although some of these drugs were known to have antibacterial activity, many have never been reported before. In particular, sulfonamide-containing structures represent a novel drug scaffold that should be investigated further. The characteristics of these drugs as antimicrobial agents may offer a safe, effective, and quick supplement to current approaches to treating bacterial infections.

Aryl-alkyl-lysines: Membrane-Active Fungicides That Act against Biofilms of Candida albicans.

Mortality due to pathogenic fungi has been exacerbated by the rapid development of resistance to frontline antifungal drugs. Fungicidal compounds with novel mechanisms of action are urgently needed. Aryl-alkyl-lysines, which are membrane-active small molecules, were earlier shown to be broad-spectrum antibacterial agents with potency in vitro and in vivo. Herein, we report the antifungal properties of aryl-alkyl-lysines. After identifying the most active compound (NCK-10), we tested its activity against a panel of clinically relevant pathogenic fungi and examined NCK-10's effect against immature and mature biofilms of Candida albicans. NCK-10 was capable of inhibiting the growth of various species of fungi (including Candida spp., Cryptococcus spp., and Aspergillus fumigatus) at concentrations similar to those of antifungal drugs used clinically. It was observed that polarization and permeability of the fungal cell membrane were compromised upon addition of NCK-10, indicating its mechanism is disruption of the fungal cell membrane. In addition to interfering with the growth of planktonic fungi, NCK-10 demonstrated the ability to both inhibit biofilm formation and reduce the metabolic activity of cells in C. albicans biofilm. Additionally, our compound was capable of crossing the blood-brain barrier in an in vitro model, expanding the potential antifungal applications for NCK-10. Overall, aryl-alkyl-lysines were found to be excellent compounds that warrant further investigation as novel antifungal agents.

Label-Free Detection and Discrimination of Bacterial Pathogens Based on Hemin Recognition.

Hemin linked to hexa(ethylene glycol)bishydrazide was patterned by inkjet printing into periodic microarrays, and evaluated for their ability to capture bacterial pathogens expressing various hemin receptors. Bacterial adhesion was imaged under darkfield conditions with Fourier analysis, supporting a label-free method of pathogen detection. Hemin microarrays were screened against a panel of 16 bacteria and found capable of capturing multiple species, some with limits of detection as low as 10(3) cfu/mL. Several Gram-positive strains including Staphylococcus aureus and Bacillus anthracis also exhibited rapid adhesion, enabling pattern recognition within minutes of exposure. This can be attributed to differences in hemin acquisition systems: aggressively adherent bacteria express cell-surface hemin receptors (CSHRs) that enable direct hemin binding and uptake, whereas other types of bacteria including most Gram-negative strains rely on the secretion and recapture of soluble proteins (hemophores) for hemin acquisition, with consequently longer times for ligand binding and detection.

Repurposing celecoxib as a topical antimicrobial agent.

There is an urgent need for new antibiotics and alternative strategies to combat multidrug-resistant bacterial pathogens, which are a growing clinical issue. Repurposing existing approved drugs with known pharmacology and toxicology is an alternative strategy to accelerate antimicrobial research and development. In this study, we show that celecoxib, a marketed inhibitor of cyclooxygenase-2, exhibits broad-spectrum antimicrobial activity against Gram-positive pathogens from a variety of genera, including Staphylococcus, Streptococcus, Listeria, Bacillus, and Mycobacterium, but not against Gram-negative pathogens. However, celecoxib is active against all of the Gram-negative bacteria tested, including strains of, Acinetobacter, and Pseudomonas, when their intrinsic resistance is artificially compromised by outer membrane permeabilizing agents such as colistin. The effect of celecoxib on incorporation of radioactive precursors into macromolecules in Staphylococcus aureus was examined. The primary antimicrobial mechanism of action of celecoxib was the dose-dependent inhibition of RNA, DNA, and protein synthesis. Further, we demonstrate the in vivo efficacy of celecoxib in a methicillin-resistant S. aureus (MRSA) infected Caenorhabditis elegans whole animal model. Topical application of celecoxib (1 and 2%) significantly reduced the mean bacterial count in a mouse model of MRSA skin infection. Further, celecoxib decreased the levels of all inflammatory cytokines tested, including tumor necrosis factor-α, interleukin-6, interleukin-1 beta, and monocyte chemo attractant protein-1 in wounds caused by MRSA infection. Celecoxib also exhibited synergy with many conventional antimicrobials when tested against four clinical isolates of S. aureus. Collectively, these results demonstrate that celecoxib alone, or in combination with traditional antimicrobials, has a potential to use as a topical drug for the treatment of bacterial skin infections.

Repurposing Clinical Molecule Ebselen to Combat Drug Resistant Pathogens.

Without a doubt, our current antimicrobials are losing the battle in the fight against newly-emerged multidrug-resistant pathogens. There is a pressing, unmet need for novel antimicrobials and novel approaches to develop them; however, it is becoming increasingly difficult and costly to develop new antimicrobials. One strategy to reduce the time and cost associated with antimicrobial innovation is drug repurposing, which is to find new applications outside the scope of the original medical indication of the drug. Ebselen, an organoselenium clinical molecule, possesses potent antimicrobial activity against clinical multidrug-resistant Gram-positive pathogens, including Staphylococcus, Streptococcus, and Enterococcus, but not against Gram-negative pathogens. Moreover, the activity of ebselen against Gram-positive pathogens exceeded those activities determined for vancomycin and linezolid, drugs of choice for treatment of Enterococcus and Staphylococcus infections. The minimum inhibitory concentrations of ebselen at which 90% of clinical isolates of Enterococcus and Staphylococcus were inhibited (MIC90) were found to be 0.5 and 0.25 mg/L, respectively. Ebselen showed significant clearance of intracellular methicillin-resistant S. aureus (MRSA) in comparison to vancomycin and linezolid. We demonstrated that ebselen inhibits the bacterial translation process without affecting mitochondrial biogenesis. Additionally, ebselen was found to exhibit excellent activity in vivo in a Caenorhabditis elegans MRSA-infected whole animal model. Finally, ebselen showed synergistic activities with conventional antimicrobials against MRSA. Taken together, our results demonstrate that ebselen, with its potent antimicrobial activity and safety profiles, can be potentially used to treat multidrug resistant Gram-positive bacterial infections alone or in combination with other antibiotics and should be further clinically evaluated.