Low Resistance Potential Research Articles

Identification of CH2-linked quinolone-aminopyrimidine hybrids as potent anti-MRSA agents: Low resistance potential and lack of cross-resistance with fluoroquinolone antibiotics

The structural optimization of B14, an antibacterial agent we previously obtained, has led to the discovery of a new class of CH2-linked quinolone-aminopyrimidine hybrids with potent anti-MRSA activities. Surprisingly, the hybrids lacking a C-6 fluoro atom at the quinolone nucleus showed equal or even stronger anti-MRSA activities than their corresponding 6-fluoro counterparts, despite the well-established structure-activity relationships (SARs) indicating that the 6-fluoro substituent enhances the antibacterial activity in conventional fluoroquinolone antibiotics. Moreover, these new hybrids, albeit structurally related to conventional fluoroquinolones, showed no cross-resistance with fluoroquinolone drugs. The most active compound, 15m, exhibited excellent activities with a MIC value of 0.39 μg/mL against both fluoroquinolone-sensitive strain USA500 and -resistant MRSA isolate Mu50. Further resistance development studies indicated MRSA is unlikely to acquire resistance against 15m. Moreover, 15m displayed favorable in vivo half-life and safety profiles. These findings suggest a rationale for further evolution of quinolone antibiotics with a high barrier to resistance.

A study on drug usage pattern of antibiotics in patients with skin disorders

Antibiotics are the crucial drugs of choice, and they are the greatest contributors to the treatment of bacterial skin diseases. The objective of the present study is to assess the drug usage patterns of antibiotics in the Department of Dermatology, Venereology, & Leprosy (DVL). A Cross-Sectional Study was conducted with ethical approval for a period of 6 calendar months. Patients were recruited according to the eligibility criteria. Relevant details were collected according to the objectives and analyzed using Microsoft Excel. During the study period, 200 patients were recruited, of which 64% were male. Most patients were in the age group of 21-40 (36%). The most commonly reported disease during our study was secondary pyoderma occurring over eczema (29.5%), followed by Psoriasis (9.5%). Penicillin (32%) and Cephalosporin (32%) were the most prescribed categories. Mainly, a duration of less than or equal to 1 week was recommended. A total of 680 drugs were prescribed, and the average number of drugs per encounter with an antibiotic was 4.50%. The percentage of encounters with injections was 12%, and the percentage of medicine from the Essential Medicine List (EML) was 43%. Most drugs were prescribed from the access groups according to the World Health Organization (WHO) AWARE (Access, Watch, Reserve) classification. According to the AWARE classification, drugs with lower resistance potential were commonly practiced here. This reflects good prescribing practice. The findings provide insight that, during our study period, the burden of bacterial skin diseases is lower in this locality when compared with other skin diseases.

Preliminary insight on diarylpentanoids as potential antimalarials: In silico, in vitro pLDH and in vivo zebrafish toxicity assessment

Malaria remains a major public health problem worldwide, including in Southeast Asia. Chemotherapeutic agents such as chloroquine (CQ) are effective, but problems with drug resistance and toxicity have necessitated a continuous search for new effective antimalarial agents. Here we report on a virtual screening of ∼300 diarylpentanoids and derivatives, in search of potential Plasmodium falciparum lactate dehydrogenase (PfLDH) inhibitors with acceptable drug-like properties. Several molecules with binding affinities comparable to CQ were chosen for in vitro validation of antimalarial efficacy. Among them, MS33A, MS33C and MS34C are the most promising against CQ-sensitive (3D7) with EC50 values of 1.6, 2.5 and 3.1 μM, respectively. Meanwhile, MS87 (EC50 of 1.85 μM) shown the most active against the CQ-resistant Gombak A strain, and MS33A and MS33C the most effective P. knowlesi inhibitors (EC50 of 3.6 and 5.1 μM, respectively). The in vitro cytotoxicity of selected diarylpentanoids (MS33A, MS33C, MS34C and MS87) was tested on Vero mammalian cells to evaluate parasite selectivity (SI), showing moderate to low cytotoxicity (CC50 > 82 μM). In addition, MS87 exhibited a high SI and the lowest resistance index (RI), suggesting that MS87 may exert effective parasite inhibition with low resistance potential in the CQ-resistant P. falciparum strain. Furthermore, the in vivo toxicity of the molecules on early embryonic development, the cardiovascular system, heart rate, motor activity and apoptosis were assessed in a zebrafish animal model. The overall results indicate the preliminary potential of diarylpentanoids, which need further investigation for their development as new antimalarial agents.

Exploration of cobalt zinc glycerate microspheres with catalytic activity for antibacterial applications

The overuse of antibiotics has caused rapid increase in the number of drug-resistant bacteria. Therefore, development of advanced biomaterials with effective antibacterial activity is in great demand. The use of metal ions in combination with organic matter (glycerol) for antibacterial activity is rarely reported. In this letter, we report for the synthesis and exploration of cobalt zinc glycerate (Co-Zn-G) microspheres with catalytic activity for antibacterial applications. The formation process of the Co-Zn-G microspheres is investigated by a solvothermal method. Due to the coordination bonds between metal ions and glycerol ligands, Co-Zn-G microspheres with improved lipophilicity are able to attach to and penetrate the bacterial membranes, resulting in enhanced antibacterial effects. In addition, the prepared Co-Zn-G microspheres have high peroxidase-like activity, which can produce a large amount of reactive oxygen species (ROS) to kill bacteria. Based on in vitro experiments, Co-Zn-G microspheres show low cytotoxicity and excellent antibacterial effects against bacteria such as S. aureus and E. coli. Thus, metal glycerate complexes provide new insights for the development of antibacterial agents with high potency and low resistance potential.

Protected yet unmanaged: insights into the ecological status of conservation priority stony reefs in Belgian waters based on the integrative use of remote sensing technologies

Stony reefs are ecologically important, providing irreplaceable ecosystem services. These fragile environments are recognised as conservation priorities by all relevant global and European policies. Bottom-contacting fisheries are an important source of anthropogenic disturbance to the seafloor’s physical and ecological integrity having immediate and destructive consequences on stony reefs and compromising ecological functions. This study, aimed to assess the ecological status (community composition and functions) of two stony reef areas -Northwest and Hinder Banks study sites -in Belgian waters using multiple remote sensing tools. Insights on the study sites’ geomorphological context and fishing patterns were gained using echo-sounding and publicly available satellite data. Video-based benthic community data were assessed against the exposure to fishing pressure using a trait-based approach linked to the biotas’ resistance and recovery potential. In the Northwest study site, between 2019 and 2022 there was a significant decline in the abundance of benthic species classified with low resistance and recovery potential to trawling. Conversely, there was a notable increase in species with moderate scores. During the same period, this site experienced an eight-fold increase in fishing effort and the hydroacoustic data revealed the presence of several trawl-marks in 2022. Similar changes in benthic communities were observed in the Hinder Banks too. Here, the abundance of species with low resistance and recovery potential was significantly lower in locations that were geomorphologically exposed to trawling compared to sheltered ones. Exposed locations had a higher abundance of opportunistic species, with moderate to high scores. The presence of several trawl marks on the seafloor was observed in the exposed locations, corresponding to fishing hotspots identified in the satellite data. Trawling activities marginally impacted richness and total abundance, but negatively altered benthic functional composition. The findings of this study provide scientific evidence of the detrimental impact of bottom-contacting fisheries on conservation priority biotopes and argues against the coexistence of such activities with Marine Protected Areas. The results of our investigation are of interest to environmental managers for the adequate implementation of environmental legislation in the face of rapid and widespread anthropogenic changes.

Self-assembled nanostructure of copper hydrogen phosphate with catalytic and antibacterial activity

The rapid development of antibiotic resistance poses a huge threat to human health. Copper-based materials is a promising alternative to the traditional antibiotics due to its high efficacy and low resistance potential for bacterial infections. In this work, three-dimensional flower-like copper hydrogen phosphate nanosheet assembled microspheres (CP-NSMSs) are synthesized through a hydrolysis-assisted synthetic method using fructose-1,6-diphosphate (FDP) as the organic phosphate source. The copper hydrogen phosphate nanosheets with high aspect ratio provide a large amount of sharp edges which could penetrate bacterial membranes, resulting in the death of bacteria. Furthermore, the as-prepared CP-NSMSs exhibit the high peroxidase-like activity producing a large amount of reactive oxygen species (ROS) to kill bacteria. Based on the in vitro bacterial growth experiments, our CP-NSMSs show an excellent sterilization effect against both Gram-positive and Gram-negative bacteria. Therefore, the CP-NSMSs synthesized using the FDP as an organic phosphate source is expected to be a promising antibacterial agent with minimum resistance potential.

Novel MoSSe/Bi2WO6 S-scheme heterojunction photocatalysts for significantly improved photoelectrochemical and photocatalytic performance

Two-dimensional MoSSe nanoplates demonstrate low internal resistance and outstanding reduction potential, while Bi2WO6 nanoparticles exhibit zero-dimensional appearance and high oxidation potential. Herein, novel MoSSe/Bi2WO6 step-scheme (S-scheme) heterojunction photocatalysts (MSSB) were prepared to combine the properties of those two materials. These catalysts were confirmed to have lower internal resistance (as low as 0.07 kΩ), and higher carriers’ separation efficiency due to the well-contacted two-dimensional/zero-dimensional structure. More importantly, the heterojunction catalysts displayed both good oxidation and reduction performance which have been confirmed by the conducted catalytic tests. With an optimized Bi2WO6 loading ratio, degradation rates (k) and photocurrent density of the MSSB2 sample were 2.09, and 8.31 times more than that of MoSSe, as well as 1.77, and 26.27 times more than that of Bi2WO6. Active species (superoxide radical •O2− and hydroxyl radical •OH) were detected by the electron spin resonance tool which could infer that a S-scheme heterojunction has already constructed between the Bi2WO6 and MoSSe. Driven by the MoSSe and band edge bending, the e– on the conduction band of Bi2WO6 readily slid toward MoSSe and recombines with the h+ on the valence band of MoSSe, while retaining the powerful e– and h+ with high redox potential on the CB of MoSSe and VB of Bi2WO6. This work further provided a novel strategy for developing S-scheme nano-heterojunction catalysts and revealed their prospects in photoelectrochemistry and photocatalysis.

The insight into effects of oxygen vacancy on the activation of peroxymonosulfate via MOF-derived magnetic CoFe2O4 for degrading organic contaminants

Herein, MOF-derived magnetic CoFe2O4 with oxygen vacancy was successfully synthesized to activate peroxymonosulfate (PMS) for the effective degradation of emerging organic contaminants. The introduction of oxygen vacancy not only increased the specific surface area of CoFe2O4, but also reduce the charge transfer resistance. The CoFe2O4 with oxygen vacancy showed low charge transfer resistance and oxidation potential. Benefitting from the existence of oxygen vacancy, the PMS could be activated quickly by CoFe2O4 to produce SO4•−. As expected, developed CoFe2O4/PMS oxidation system displayed the excellent degradation ability toward various typical organic pollutants, and the organic pollutant could be mineralized into CO2, H2O and other inorganic molecules. Interestingly, both redox couples of Fe3+/Fe2+ and Co3+/Co2+ played a critical role in the PMS activation process. The SO4•−, OH•, O2•− and 1O2 were major active species in the CoFe2O4/PMS system, which were responsible for the degradation of organic pollutants. Furthermore, proposed CoFe2O4/PMS oxidation system also presented a wide pH range of applicability. The existence of magnetic property was convenient for the recovery of catalyst. All in all, this study provided a promising catalyst for the activation of PMS, and obtained results injected some new insights into the research on advanced oxidation processes (AOPs).

Recombinant Actifensin and Defensin-d2 Induce Critical Changes in the Proteomes of Multidrug-Resistant Pseudomonas aeruginosa and Candida albicans.

ABSTRACTDrug-resistant strains of Pseudomonas aeruginosa and Candida albicans pose serious threats to human health because of their propensity to cause fatal infections. Defensin and defensin-like antimicrobial peptides (AMPs) are being explored as new lines of antimicrobials, due to their broad range of activity, low toxicity, and low pathogen resistance. Defensin-d2 and actifensin are AMPs from spinach and Actinomyces ruminicola, respectively, whose mechanisms of action are yet to be clearly elucidated. This study investigated the mechanisms of action of the recombinant AMPs through label-free quantitative proteomics. The data are available at PRIDE with accession number PXD034169. A total of 28 and 9 differentially expressed proteins (DEPs) were identified in the treated P. aeruginosa and C. albicans, respectively, with a 2-fold change threshold and P values of <0.05. Functional analysis revealed that the DEPs were involved in DNA replication and repair, translation, and membrane transport in P. aeruginosa, while they were related mainly to oxidative phosphorylation, RNA degradation, and energy metabolism in C. albicans. Protein-protein interactions showed that the DEPs formed linear or interdependent complexes with one another, indicative of functional interaction. Subcellular localization indicated that the majority of DEPs were cytoplasmic proteins in P. aeruginosa, while they were of nuclear or mitochondrial origin in C. albicans. These results show that recombinant defensin-d2 and actifensin can elicit complex multiple organism responses that cause cell death in P. aeruginosa and C. albicans.IMPORTANCE AMPs are considered essential alternatives to conventional antimicrobials because of their broad-spectrum efficacy and low potential for resistance by target cells. In this study, we established that the recombinant AMPs defensin-d2 and actifensin exert proteomic changes in P. aeruginosa and C. albicans within 1 h after treatment. We also found that the DEPs in peptide-treated P. aeruginosa are related to ion transport and homeostasis, molecular functions including nucleic and amino acid metabolism, and structural biogenesis and activity, while the DEPs in treated C. albicans are mainly involved in membrane synthesis and mitochondrial metabolism. Our results also highlight ATP synthase as a potential drug target for multidrug-resistant P. aeruginosa and C. albicans.

Improving the Therapeutic Index of Smp24, a Venom-Derived Antimicrobial Peptide: Increased Activity against Gram-Negative Bacteria.

Antimicrobial peptides (AMPs) are naturally occurring compounds which possess a rapid killing mechanism and low resistance potential. Consequently, they are being viewed as potential alternatives to traditional antibiotics. One of the major factors limiting further development of AMPs is off-target toxicity. Enhancements to antimicrobial peptides which can maximise antimicrobial activity whilst reducing mammalian cytotoxicity would make these peptides more attractive as future pharmaceuticals. We have previously characterised Smp24, an AMP derived from the venom of the scorpion Scorpio maurus palmatus. This study sought to better understand the relationship between the structure, function and bacterial selectivity of this peptide by performing single amino acid substitutions. The antimicrobial, haemolytic and cytotoxic activity of modified Smp24 peptides was determined. The results of these investigations were compared with the activity of native Smp24 to determine which modifications produced enhanced therapeutic indices. The structure–function relationship of Smp24 was investigated by performing N-terminal, mid-chain and C-terminal amino acid substitutions and determining the effect that they had on the antimicrobial and cytotoxic activity of the peptide. Increased charge at the N-, mid- and C-termini of the peptide resulted in increased antimicrobial activity. Increased hydrophobicity at the N-terminus resulted in reduced haemolysis and cytotoxicity. Reduced antimicrobial, haemolytic and cytotoxic activity was observed by increased hydrophobicity at the mid-chain. Functional improvements have been made to modified peptides when compared with native Smp24, which has produced peptides with enhanced therapeutic indices.

Synthesis and biological evaluation of tetrahydroisoquinoline-derived antibacterial compounds

Antibiotic resistance is one of the greatest threats to modern medicine. Drugs that were once routinely used to treat infections are being rendered ineffective, increasing the demand for novel antibiotics with low potential for resistance. Here we report the synthesis of 18 novel cationic tetrahydroisoquinoline-triazole compounds. Five of the developed molecules were active against S. aureus at a low MIC of 2–4 μg/mL. Hit compound 4b was also found to eliminate M. tuberculosis H37Rv at MIC of 6 μg/mL. This potent molecule was found to eliminate S. aureus effectively, with no resistance observed after thirty days of sequential passaging. These results identified compound 4b and its analogues as potential candidates for further drug development that could help tackle the threat of antibiotic resistance.

Lactoferricin-inspired peptide AMC-109 augments the effect of ciprofloxacin against Pseudomonas aeruginosa biofilm in chronic murine wounds

Chronic wounds are characterised by prolonged inflammation, low mitogenic activity, high protease/low inhibitor activity, microbiota changes and biofilm formation, combined with the aetiology of the original insult. One strategy to promote healing is to terminate the parasitism-like relationship between the biofilm-growing pathogen and host response. Antimicrobial peptide AMC-109 is a potential treatment with low resistance potential and broad-spectrum coverage with rapid bactericidal effect. We aimed to investigate whether adjunctive AMC-109 could augment the ciprofloxacin effect in a chronic Pseudomonas aeruginosa wound model. Third-degree burns were inflicted on 33 BALB/c mice. Pseudomonas aeruginosa embedded in seaweed alginate was injected sub-eschar to mimic biofilm. Mice were randomised to receive AMC-109, combined AMC-109 and ciprofloxacin, ciprofloxacin, or placebo for 5 days followed by sample collection. A lower bacterial load was seen in the double-treated group compared with either monotherapy group (AMC-109, p=0.0076; ciprofloxacin, p=0.0266). To evaluate the innate host response, cytokines and growth factors were quantified. The pro-inflammatory response was dampened in the double-treated mice compared with the mono-ciprofloxacin-treated group (p=0.0009). Lower mobilisation of neutrophils from the bone marrow was indicated by reduced G-CSF in all treatment groups compared with placebo. Improved tissue remodelling was indicated by the highest level of tissue inhibitor of metalloproteases and low metalloprotease level in the double-treated group. AMC-109 showed adjunctive antipseudomonal abilities augmenting the antimicrobial effect of ciprofloxacin in this wound model. The study indicates a potential role for AMC-109 in treating chronic wounds with complicating biofilm infections.

The role of new carbapenem combinations in the treatment of multidrug-resistant Gram-negative infections.

Multi-drug resistant (MDR) Gram-negative bacteria represent a growing threat, with an increasing prevalence of carbapenem-resistant Enterobacterales (CRE) infections, for which treatment options are limited. New treatment combinations composed of a β-lactam antibiotic plus a potent β-lactamase inhibitor (BLI) with anti-carbapenemase activity have been developed, including two carbapenem/BLI combinations that are commercially available—meropenem/vaborbactam (Vabomere® in the US, Vaborem® in Europe; Melinta Therapeutics) and imipenem/cilastatin/relebactam (Recarbrio®; Merck Sharp & Dohme), plus one other (meropenem/nacubactam) in early clinical development. This review provides a summary of the preclinical evidence supporting the use of carbapenem/BLI combinations and presents the clinical evidence across a range of MDR Gram-negative infections, with a focus on the use of meropenem/vaborbactam. All three BLIs have shown in vivo activity against Klebsiella pneumoniae carbapenemase and other class A carbapenemases. In 2019, meropenem/vaborbactam was listed in the WHO’s list of essential medicines, because of its activity against priority 1 antibiotic-resistant pathogens. Meropenem/vaborbactam has considerable in vitro and in vivo activity against CRE, and in vitro evidence showing a low potential for resistance at clinically relevant doses. In randomized trials, meropenem/vaborbactam was non-inferior to piperacillin/tazobactam in patients with complicated urinary tract infection and more effective than the best-available treatment in patients with serious CRE infections. Meropenem/vaborbactam is well tolerated and, based on clinical experience, demonstrated lower toxicity compared with the combination regimens that have previously been the standard of care. In conclusion, carbapenem/BLI combinations represent an important therapeutic strategy in patients with MDR Gram-negative infections.

Comparative study for the efficacy of Sofinox cream against Staphylococcus aureus with Fucidin cream, T-Bact ointment and screening for resistant mutants.

Objective: To determine the Minimum Inhibition Concentration of Sofinox cream, Fucidin cream, T Bact ointment against Staphylococcus aureus and to screen for the development of resistant mutants and Whole Genome Sequencing(WGS) of the strains used and the strains showing raised MIC following serial passages. Material and Methods: An in vitro study was conducted to determine the Minimum Inhibition Concentration of Sofinox cream, Fucidin cream, T Bact ointment against seven strains of Staphylococcus aureus (ATCC 25923, ATCC 43300, ATCC 700699, 2 clinical isolates of methicillin-sensitive S. aureus (MSSA) and 2 methicillin-resistant S. aureus (MRSA). We also screened the same strains for the development of resistant mutants of Staphylococcus aureus by sub MIC exposure to Sofinox cream, Fucidin cream and T Bact ointment up to 70 serial passage and their WGS. Results: The MIC values of the three topical antibiotics ranged between 16 µg to 64 µg for all the strains of Staphylococcal strains tested. The MIC value did not change for three strains of Staphylococcus aureus and a one-fold rise in MIC value occurred for four strains of the Staphylococcus aureus strains for Sofinox cream after 70 passages at sub MIC concentration. WGS analysis of the strains with Sofinox cream treatment, it was noted that 150 number significant genetic variations to MSSA (ATCC 25923) and 84 number for MRSA (ATCC 700699) and no significant changes with other strains. For two of the strains the MIC value remained the same, three strains showed the one-fold rise and two strains showed a four-fold rise in MIC value for Fucidin cream after 70 passages at sub MIC concentration. Through the WGS analysis of the strains, it was noted that 185 significant genetic variations to one of the clinical isolates of MSSA followed by 102 to MRSA standard strain ATCC700699, the strains showing a one-fold rise in MIC showed 95, 85 and 76 number of genetic variations respectively. All the strains of Staphylococcus aureus showed a rise in MIC for T Bact which ranged from one to four-fold rise. WGS analysis of the strains with T Bact ointment treatment, it was noted the variations ranging from 85 to 158 with a one-fold rise to a four-fold rise in MIC value. Conclusions: In the present study it was observed that Sofinox cream had low resistance potential in vitro compared to Fucidin cream whereas T bact ointment had more resistance potential when exposed to sub MIC concentration of the cream/ointment. Even the WGS analysis showed variations correlating with MIC values. Hence there is a less likely chance of development of resistant mutants with the topical use of Sofinox cream even up to 8 weeks.

Advances in Antimicrobial Peptides with an approach to molecular structure prediction

Antimicrobial peptides (AMP) are molecules involved in the innate immune system of almost all living organisms. They are potent agents with diverse structural and antimicrobial properties, which represent one of the most promising future drug candidate for combating infections and antimicrobial drug resistance. They have also a wide spectrum of activity against a large number of pathogenic microorganisms, multiple mechanisms of action and a low potential for resistance. Numerous AMPs have been isolated from natural sources and many others have been de novo designed and synthetically produced. This review provide insight into antimicrobials properties of AMPs, focusing in antibacterial molecules, that provides better understanding of versatile biological properties of such peptides. Also, provide a short insight into chemical modifications, characterization and the principal methods for protein structure prediction of AMPs.

Effects of dosage of warm mix asphalt additive on stiffness, cracking susceptibility, and moisture sensitivity characteristics

Warm mix asphalt (WMA) technology has the capability of lowering asphalt mixing and compacting temperature by 30 °C or more without compromising the performance of asphalt pavement. This results to a lower cooling rate that allows for long haul, and sufficient compaction time. The objective of this study is to evaluate the effectiveness of the common chemical additives on the properties of WMA mixtures through field and laboratory testing programs. Three dosages (0.3, 0.5, and 0.7% by weight of asphalt cement) were used without changing the job mix formula. Among the different additive dosage used, 0.5% had a better overall performance. For example, the moisture sensitivity test for the 0.5% WMA indicated the highest tensile strength ratio; subsequently, low moisture damage. All WMA mixtures had low rutting resistance potential and higher cracking resistance compared to conventional mix.

Potential Application of Silver Nanoparticles Encapsulated in Branched Amphiphilic Peptide Capsules to Circumvent Antibiotic Resistance in Methicillin-Resistant Staphylococcus Aureus: A Research Protocol

Introduction: Antibiotic resistance is a major global health concern as many fatalities occur each year due to severe infections associated with it, such as sepsis. This research protocol hopes to address the issue of antibiotic resistance in methicillin-resistant Staphylococcus aureus (MRSA) by using an alternative antibiotic therapy. Silver nanoparticles (AgNPs), which have antibiotic properties and low antibiotic resistance potential, will be administered in conjunction with stable and biocompatible branched amphiphilic peptide capsules (BAPCs). Surface functionalized ligands will be attached to the peptide capsules to target iron receptors essential to MRSA survival. By targeting its iron receptors, the bacteria will be unable to mutate in such a way that would attenuate its uptake of this antibiotic. Methods: Testing will begin in vitro on MRSA cultures to assess the minimum inhibitory concentration of the various AgNP treatment groups. Constraints determining the minimum inhibitory concentration include a minimum 3-hour delay in bactericidal effect from application, and a 95% eradication efficacy. Drug efficacy will be evaluated via ex vivo and in vivo mice experiments, with off-target toxicity effects measured via BAPC targeted immunohistochemistry, and both serological and organ-based tests. Repeated in vivo treatments will be performed against a control to measure the relative antibiotic resistance advantages this treatment proposes. As this protocol requires the use of mice, ethics approval from the Canadian Council on Animal Care will be obtained prior to experimentation. Results: It is expected that the AgNPs will be successfully encapsulated within the structurally-sound BAPCs and that the AgNPs will eradicate a significant amount of the MRSA present in the human body with minimal side effects. The in vitro, ex vivo and in vivo tests are likely to yield results that demonstrate that the most effective protocol in eradicating MRSA is to use AgNPs in BAPCs in conjunction with a vancomycin treatment. The proposal will likely satisfy the criteria for appropriate AgNP doses, which includes bactericidal effect in a time frame of hours, over 95% efficacy, and statistically significant reproducibility. Discussion: Successful BAPC mediated delivery of AgNPs prove the potential for targeted antibiotic application against multidrug bacteria with lower risk of antibiotic resistance compared to conventional antibiotics. This proof of concept protocol demonstrates the potential for applying rational design of BAPCs as a delivery vector. Certain limitations, including off-target toxicity and redundant targeting are issues to be cognizant of and controlled. Conclusion: This novel therapy can be considered as a preliminary step in overcoming antibiotic resistance. With appropriate modifications to the functional ligands attached to the BAPCs, the proposed drug mechanism could be applied to treat other bacterial strains.

Genomic characterization of Salmonella Uzaramo for human invasive infection.

Salmonella is composed of a wide variety of serovars, causing human self-limited gastrointestinal illnesses or invasive infections. Invasive non-typhoidal Salmonella (iNTS) is well documented, with high mortality for children and immunocompromised adults in sub-Saharan Africa and has recently been reported in Southeast Asia. However, iNTS in China remains unknown. In May 2019, a case of invasive infection caused by Salmonella enterica serovar Uzaramo (S. Uzaramo) was reported for the first time in China. Phylogenomic analysis was performed by genomic sequencing the available contextualized isolates, which separated the two Chinese strains into different sublineages. Both phenotypic and genomic characterization demonstrated that the S. Uzaramo isolates showed in general low antimicrobial resistance potential, except one isolated from lake-water in China. Additional comparative genomic analysis and Caenorhabditis elegans killing assays suggested a unique combination of virulence factors, including typhoid toxin and tcf fimbrial adhesin, which might play a role in the invasive infection. This study highlights that the transparency of global surveillance genomic data could accelerate understanding of virulence and antimicrobial resistance makeup of a previously unknown threat.

Tedizolid is a promising antimicrobial option for the treatment of Staphylococcus aureus infections in cystic fibrosis patients.

Tedizolid is a protein synthesis inhibitor in clinical use for the treatment of Gram-positive infections. Pulmonary MRSA infections are a growing problem in patients with cystic fibrosis (CF) and the efficacy of tedizolid-based therapy in CF pulmonary infections is unknown. To evaluate the in vitro and in vivo activity of tedizolid and predict the likelihood of tedizolid resistance selection in CF-background Staphylococcus aureus strains. A collection of 330 S. aureus strains (from adult and paediatric patients), either of normal or small colony variant (SCV) phenotypes, gathered at three CF centres in the USA was used. Tedizolid activity was assessed by broth microdilution, Etest and time-kill analysis. In vivo tedizolid efficacy was tested in a murine pneumonia model. Tedizolid in vitro mutants were obtained by 40 days of exposure and progressive passages. Whole genome sequencing of clinical S. aureus strains with reduced susceptibility to tedizolid was performed. MRSA strain MIC90s were tedizolid 0.12-0.25 mg/L and linezolid 1-2 mg/L; for MSSA strains, MIC90s were tedizolid 0.12 mg/L and linezolid 1-2 mg/L. Two strains, WIS 441 and Seattle 106, with tedizolid MICs of 2 mg/L and 1 mg/L, respectively, had MICs above the FDA tedizolid breakpoint (0.5 mg/L). Tedizolid at free serum concentrations exhibited a bacteriostatic effect. Mean bacterial burdens in lungs (log10 cfu/g) for WIS 423-infected mice were: control, 11.2±0.5; tedizolid-treated (10 mg/kg), 3.40±1.87; linezolid-treated (40 mg/kg), 4.51±2.1; and vancomycin-treated (30 mg/kg), 5.21±1.93. For WIS 441-infected mice the (log10 cfu/g) values were: control, 9.66±0.8; tedizolid-treated, 3.18±1.35; linezolid-treated 5.94±2.19; and vancomycin-treated, 4.35±1.7. These results suggest that tedizolid represents a promising therapeutic option for the treatment of CF-associated MRSA/MSSA infections, having potent in vivo activity and low resistance potential.

Nanosilver/poly (dl-lactic-co-glycolic acid) on titanium implant surfaces for the enhancement of antibacterial properties and osteoinductivity.

BackgroundDespite titanium (Ti) implants have been commonly used in the medical device field due to their superior biocompatibility, implant-associated bacterial infection remains a major clinical complication. Nanosilver, an effective antibacterial agent against a wide spectrum of bacterial strains, with a low-resistance potential, has attracted much interest too. Incorporation of nanosilver on Ti implants may be a promising approach to prevent biofilm formation.PurposeThe objective of the study was to investigate the antibacterial effects and osteoinductive properties of nanosilver/poly (dl-lactic-co-glycolic acid)-coated titanium (NSPTi).MethodsGram-positive methicillin-resistant Staphylococcus aureus (MRSA) and the Gram-negative opportunistic pathogen Pseudomonas aeruginosa (PAO-1) were used to evaluate the antibacterial activity of NSPTi implants through the analysis of bacterial colonization in vitro and in vivo. Furthermore, we examined the osteoinductive potential of NSPTi implants by investigating the proliferation and differentiation of MC3T3-E1 preosteoblast cells. In vivo, the osteoinductive properties of NSPTi implants were assessed by radiographic evaluation, H&E staining, and Masson’s trichrome staining.ResultsIn vitro, bacterial adhesion to the 2% NSPTi was significantly inhibited and <1% of adhered bacteria survived after 24 hours. In vitro, the average colony-forming units (CFU)/g ratios in the 2% NSPTi with 103 CFU MRSA and PAO-1 were 1.50±0.68 and 1.75±0.6, respectively. In the uncoated Ti groups, the ratios were 1.03±0.82×103 and 0.94±0.49×103, respectively. These results demonstrated that NSPTi implants had prominent antibacterial properties. Proliferation of MC3T3-E1 cells on the 2% NSPTi sample was 1.51, 1.78, and 2.22 times that on the uncoated Ti control after 3, 5, and 7 days’ incubation, respectively. Furthermore, NSPTi implants promoted the maturation and differentiation of MC3T3-E1 cells. In vivo, NSPTi accelerated the formation of new bone while suppressing bacterial survival.ConclusionNSPTi implants have simultaneous antibacterial and osteoinductive activities and therefore have the potential in clinical applications.