The Importance of Bactericidal Drugs: Future Directions in Infectious Disease

Metabolomics unveil key pathways underlying the synergistic activities of aztreonam and avibactam against multidrug-resistant Escherichia coli

PURPOSE

Aztreonam/avibactam is effective against serious infections caused by Gram-negative bacteria including Enterobacterales harboring metallo-β-lactamases. While the utility of this combination has been established in vitro and in clinical trials, the purpose of this study is to enhance our understanding of the underlying mechanism responsible for their activities through metabolomic profiling of a multidrug-resistant Escherichia coli clinical isolate.

METHODS

Metabolomic analyses of time-dependent changes in endogenous bacterial metabolites in a clinical isolate of a multidrug-resistant E. coli treated with aztreonam and avibactam were performed. E. coli metabolomes were compared at 15 min, 1 h and 24 h following treatments with either avibactam (4 mg/L), aztreonam (4 mg/L), or aztreonam (4 mg/L) + avibactam (4 mg/L).

RESULTS

Drug treatment affected 326 metabolites with magnitude changes of at least 2-fold, most of which are involved primarily in peptidoglycan biosynthesis, nucleotide metabolism, and lipid metabolism. The feedstocks for peptidoglycan synthesis were depleted by aztreonam/avibactam combination; a significant downstream increase in nucleotide metabolites and a release of lipids were observed at the three timepoints.

CONCLUSION

The findings indicate that the aztreonam/avibactam combination accelerates structural damage to the bacterial membrane structure and their actions were immediate and sustained compared to aztreonam or avibactam alone. By inhibiting the production of crucial cell wall precursors, the combination may have inflicted damages on bacterial DNA.

Novel antimony-based antimicrobial drug targets membranes of Gram-positive and Gram-negative bacterial pathogens

Antimicrobial resistance (AMR) poses a significant worldwide public health crisis that continues to threaten our ability to successfully treat bacterial infections. With the decline in effectiveness of conventional antimicrobial therapies and the lack of new antibiotic pipelines, there is a renewed interest in exploring the potential of metal-based antimicrobial compounds. Antimony-based compounds with a long history of use in medicine have re-emerged as potential antimicrobial agents. We previously synthesized a series of novel organoantimony(V) compounds complexed with cyanoximates with a strong potential of antimicrobial activity against several AMR bacterial and fungal pathogens. Here, five selected compounds were studied for their antibacterial efficacy against three important bacterial pathogens: Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus. Among five tested compounds, SbPh4ACO showed antimicrobial activity against all three bacterial strains with the MIC of 50-100 µg/mL. The minimum bactericidal concentration/MIC values were less than or equal to 4 indicating that the effects of SbPh4ACO are bactericidal. Moreover, ultra-thin electron microscopy revealed that SbPh4ACO treatment caused membrane disruption in all three strains, which was further validated by increased membrane permeability. We also showed that SbPh4ACO acted synergistically with the antibiotics, polymyxin B and cefoxitin used to treat AMR strains of P. aeruginosa and S. aureus, respectively, and that at synergistic MIC concentration 12.5 µg/mL, its cytotoxicity against the cell lines, Hela, McCoy, and A549 dropped below the threshold. Overall, the results highlight the antimicrobial potential of novel antimony-based compound, SbPh4ACO, and its use as a potentiator of other antibiotics against both Gram-positive and Gram-negative bacterial pathogens.

IMPORTANCE

Antibiotic resistance presents a critical global public health crisis that threatens our ability to combat bacterial infections. In light of the declining efficacy of traditional antibiotics, the use of alternative solutions, such as metal-based antimicrobial compounds, has gained renewed interest. Based on the previously synthesized innovative organoantimony(V) compounds, we selected and further characterized the antibacterial efficacy of five of them against three important Gram-positive and Gram-negative bacterial pathogens. Among these compounds, SbPh4ACO showed broad-spectrum bactericidal activity, with membrane-disrupting effects against all three pathogens. Furthermore, we revealed the synergistic potential of SbPh4ACO when combined with antibiotics, such as cefoxitin, at concentrations that exert no cytotoxic effects tested on three mammalian cell lines. This study offers the first report on the mechanisms of action of novel antimony-based antimicrobial and presents the therapeutic potential of SbPh4ACO in combating both Gram-positive and Gram-negative bacterial pathogens while enhancing the efficacy of existing antibiotics.

Shorter versus longer duration of antibiotic treatment in children with bacterial meningitis: a systematic review and meta-analysis

The optimal duration of antibiotic treatment for the most common bacterial meningitis etiologies in the pediatric population, namely Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis, is not well-established in the literature. Therefore, we aimed to perform an updated meta-analysis comparing shorter versus longer antibiotic treatment in children with meningitis. PubMed, EMBASE, and Cochrane databases were searched for randomized controlled trials (RCTs) that compared shorter (up to 7 days) versus longer (10 days or double the days of the equivalent short course) duration of antibiotic treatment in children with meningitis and reported the outcomes of treatment failure, death, neurologic sequelae, non-neurologic complications, hearing impairment, nosocomial infection, and relapse. Heterogeneity was examined with I2 statistics. RevMan 5.4.1 was used for statistical analysis and RoB-2 (Cochrane) for risk of bias assessment. Of 684 search results, 6 RCTs were included, with a cohort of 1333 children ages 3 weeks to 15.5 years, of whom 49.51% underwent a short antibiotic course. All RCTs included monotherapy with ceftriaxone, except one, which added vancomycin as well. No differences were found comparing the short and long duration of therapy concerning treatment failure, relapse, mortality, and neurologic complications at discharge and at follow-up.  Conclusion: Because no statistically significant differences were found between groups for the analyzed outcomes, the results of this meta-analysis support shorter therapy. However, generalizing these results to complicated meningitis and infections caused by other pathogens should be made with caution. (PROSPERO identifier: CRD42022369843). What is Known: • Current recommendations on the duration of antibiotic therapy for bacterial meningitis are mostly based on clinical practice. • Defining an optimal duration of antibiotic therapy is essential for antimicrobial stewardship achievement, improving patient outcomes, and minimizing adverse effects. What is New: • There are no differences between shorter versus longer antibiotic treatment duration in regard to treatment failure, relapse, mortality, neurologic complications, and hearing impairment at discharge and at follow-up.

Electrochemical DNA biosensors developed for the monitoring of biointeractions with drugs: a review

The interaction of drugs with DNA is important for the discovery of novel drug molecules and for understanding the therapeutic effects of drugs as well as the monitoring of side effects. For this reason, many studies have been carried out to investigate the interactions of drugs with nucleic acids. In recent years, a large number of studies have been performed to electrochemically detect drug-DNA interactions. The fast, sensitive, and accurate results of electrochemical techniques have resulted in a leading role for their implementation in this field. By means of electrochemical techniques, it is possible not only to demonstrate drug-DNA interactions but also to quantitatively analyze drugs. In this context, electrochemical biosensors for drug-DNA interactions have been examined under different headings including anticancer, antiviral, antibiotic, and central nervous system drugs as well as DNA-targeted drugs. An overview of the studies related to electrochemical DNA biosensors developed for the detection of drug-DNA interactions that were reported in the last two decades in the literature is presented herein along with their applications and they are discussed together with their future perspectives.

Antioxidant, Volatile Compounds; Antimicrobial, Anti-Inflammatory, and Dermatoprotective Properties of Cedrus atlantica (Endl.) Manetti Ex Carriere Essential Oil: In Vitro and In Silico Investigations

Cedrus atlantica (Endl.) Manetti ex Carriere is an endemic tree possessing valuable health benefits which has been widely used since time immemorial in international traditional pharmacopoeia. The aim of this exploratory investigation is to determine the volatile compounds of C. atlantica essential oils (CAEOs) and to examine their in vitro antimicrobial, antioxidant, anti-inflammatory, and dermatoprotective properties. In silico simulations, including molecular docking and pharmacokinetics absorption, distribution, metabolism, excretion, and toxicity (ADMET), and drug-likeness prediction were used to reveal the processes underlying in vitro biological properties. Gas chromatography-mass spectrophotometry (GC-MS) was used for the chemical screening of CAEO. The antioxidant activity of CAEO was investigated using four in vitro complementary techniques, including ABTS and DPPH radicals scavenging activity, ferric reductive power, and inhibition of lipid peroxidation (β-carotene test). Lipoxygenase (5-LOX) inhibition and tyrosinase inhibitory assays were used for testing the anti-inflammatory and dermatoprotective properties. GC-MS analysis indicated that the main components of CAEO are β-himachalene (28.99%), α-himachalene (14.43%), and longifolene (12.2%). An in vitro antimicrobial activity of CAEO was examined against eleven strains of Gram-positive bacteria (three strains), Gram-negative bacteria (four strains), and fungi (four strains). The results demonstrated high antibacterial and antifungal activity against ten of them (>15 mm zone of inhibition) using the disc-diffusion assay. The microdilution test showed that the lowest values of MIC and MBC were recorded with the Gram-positive bacteria in particular, which ranged from 0.0625 to 0.25 % v/v for MIC and from 0.5 to 0.125 % v/v for MBC. The MIC and MFC of the fungal strains ranged from 0.5 to 4.0% (MIC) and 0.5 to 8.0% v/v (MFC). According to the MBC/MIC and MFC/MIC ratios, CAEO has bactericidal and fungicidal activity. The results of the in vitro antioxidant assays revealed that CAEO possesses remarkable antioxidant activity. The inhibitory effects on 5-LOX and tyrosinase enzymes was also significant (p < 0.05). ADMET investigation suggests that the main compounds of CAEO possess favorable pharmacokinetic properties. These findings provide scientific validation of the traditional uses of this plant and suggest its potential application as natural drugs.

Structural basis for motilin and erythromycin recognition by motilin receptor

Motilin is an endogenous peptide hormone almost exclusively expressed in the human gastrointestinal (GI) tract. It activates the motilin receptor (MTLR), a class A G protein-coupled receptor (GPCR), and stimulates GI motility. To our knowledge, MTLR is the first GPCR reported to be activated by macrolide antibiotics, such as erythromycin. It has attracted extensive attention as a potential drug target for GI disorders. We report two structures of G_q-coupled human MTLR bound to motilin and erythromycin. Our structures reveal the recognition mechanism of both ligands and explain the specificity of motilin and ghrelin, a related gut peptide hormone, for their respective receptors. These structures also provide the basis for understanding the different recognition modes of erythromycin by MTLR and ribosome. These findings provide a framework for understanding the physiological regulation of MTLR and guiding drug design targeting MTLR for the treatment of GI motility disorders.

Evaluation of analogs of mutacin 1140 in systemic and cutaneous methicillin-resistant Staphylococcus aureus infection models in mice

Mutacin 1140 (Mu1140) is a potent antibiotic against Gram-positive bacteria, such as Staphylococcus aureus. The antibiotic is produced by the oral bacterium Streptococcus mutans and is a member of the epidermin family of type AI lantibiotics. The antibiotic exerts its inhibitory activity by binding to the cell wall precursor lipid II, blocking cell wall synthesis, and by disrupting bacterial membranes. In previous studies, the novel K2A and R13A analogs of Mu1140 have been identified to have superior pharmacokinetic properties compared to native Mu1140. In this study, the use of a combined formulation of the Mu1140 K2A and R13A analogs was shown to be more effective at treating MRSA bacteremia than the native Mu1140 or vancomycin. The analogs were also shown to be effective in treating an MRSA skin infection. The use of K2A and R13A analogs may provide a future alternative for treating serious Gram-positive bacterial infections. In a previous study, the Mu1140 analogs were shown to have significantly longer drug clearance times, leading to higher plasma concentrations over time. These properties warranted further testing to determine whether the analogs are effective for the treatment of systemic MRSA and acute skin infections. In this study, Mu1140 analogs were shown to be more effective than currently available treatments for systemic and skin MRSA infections. Further, the study clearly shows that the new analogs are superior to native Mu1140 for the treatment of a systemic MRSA infection. These findings support continued drug product development efforts using the K2A and R13A Mu1140 analogs, and that these analogs may ameliorate the outcome of serious bacterial infections.

Natural-Product-Directed Catalytic Stereoselective Synthesis of Functionalized Fused Borane Cluster-Oxazoles for the Discovery of Bactericidal Agents

The identification of an alternative chemical space in order to address the global challenge posed by emerging antimicrobial resistance is very much needed for the discovery of novel antimicrobial lead compounds. Boron clusters are currently being explored in drug discovery due to their unique steric and electronic properties. However, the challenges associated with the synthesis and derivatization techniques of these compounds have limited their utility in the rapid construction of a library of molecules for screening against various biological targets as an alternative molecular platform. Herein, we report a transition-metal-catalyzed regioselective direct B-H alkylation-annulation of the closo-dodecaborate anion with natural products such as menthol and camphor as the directing groups. This method allowed the rapid construction of a library of 1,2,3-trisubstituted clusters, which were evaluated in terms of their antibacterial activity against WHO priority pathogens. Several of the synthesized dodecaborate derivatives displayed medium- to high-level bactericidal activity against Gram-positive and Gram-negative bacteria.

Dihydropyrimidinones Against Multiresistant Bacteria

The increase in bacterial resistance to antimicrobials has led to high morbidity and mortality rates, posing a major public health problem, requiring the discovery of novel antimicrobial substances. The biological samples were identified as the Gram-negative bacilli Acinetobacter baumannii, Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, Morganella morgannii, Pseudomonas aeruginosa and Serratia marcescens and the Gram-positive cocci Enterococcus faecium, and Staphylococcus aureus, all of them resistant to at least three classes of antimicrobials. The antibacterial activity of the compounds was checked in vitro by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) by the broth microdilution method and plating in brain heart infusion (BHI) agar, respectively. The chemical characterization of the compounds was performed by measuring the melting point and gas chromatography coupled with mass spectrometry (GC–MS) on a Shimadzu GC–MS-QP system 2010SE. Synthetic compounds showed antimicrobial activity against Gram-positive cocci at MIC concentrations 0.16–80 μg/ml and Gram-negative bacilli at MIC concentrations 23.2–80 μg/ml. Enterococcus faecium and S. aureus had the best MIC values. The results of the cytotoxicity test indicated that the synthetic compounds showed no significant difference in three concentrations tested (5, 20, and 80 μg/ml), allowing cell viability not different from that assigned to the control, without the tested compounds. In this context, the development of DHPM derivatives brings an alternative and perspective on effectiveness of drugs as potential future antimicrobial agents.

Biochar for agronomy, animal farming, anaerobic digestion, composting, water treatment, soil remediation, construction, energy storage, and carbon sequestration: a review

In the context of climate change and the circular economy, biochar has recently found many applications in various sectors as a versatile and recycled material. Here, we review application of biochar-based for carbon sink, covering agronomy, animal farming, anaerobic digestion, composting, environmental remediation, construction, and energy storage. The ultimate storage reservoirs for biochar are soils, civil infrastructure, and landfills. Biochar-based fertilisers, which combine traditional fertilisers with biochar as a nutrient carrier, are promising in agronomy. The use of biochar as a feed additive for animals shows benefits in terms of animal growth, gut microbiota, reduced enteric methane production, egg yield, and endo-toxicant mitigation. Biochar enhances anaerobic digestion operations, primarily for biogas generation and upgrading, performance and sustainability, and the mitigation of inhibitory impurities. In composts, biochar controls the release of greenhouse gases and enhances microbial activity. Co-composted biochar improves soil properties and enhances crop productivity. Pristine and engineered biochar can also be employed for water and soil remediation to remove pollutants. In construction, biochar can be added to cement or asphalt, thus conferring structural and functional advantages. Incorporating biochar in biocomposites improves insulation, electromagnetic radiation protection and moisture control. Finally, synthesising biochar-based materials for energy storage applications requires additional functionalisation.

Biochar amendment to advance contaminant removal in anaerobic digestion of organic solid wastes: A review

Anaerobic digestion (AD) has been widely applied to convert organic solid wastes into biogas, a renewable energy, and digestate, a bio-fertilizer, to sustain waste management. Nevertheless, several vexing contaminants in OSWs restrict digestate application in agriculture. Biochar has been evidenced to effectively improve AD by promoting organic biodegradation and alleviating the accumulation of inhibitory substances (e.g. ammonia and volatile fatty acids). Furthermore, biochar could advance contaminant removal in AD given its highly porous, conductive and alkaline features. Thus, this review aims to highlight the role of biochar amendment to advance contaminant removal in AD of OSWs. Key contaminants, such as antibiotics, heavy metals, microplastics, polycyclic aromatic hydrocarbons, furfural and 5-hydroxy methyl furfural (5-HMF) that ubiquitously present in OSWs were demonstrated. The underlying mechanisms of biochar to amend the removal of these contaminants by AD were discussed. Furthermore, future perspectives to the development of biochar-assisted AD for OSWs treatment were provided.

Evaluation of Short-Chain Antimicrobial Peptides With Combined Antimicrobial and Anti-inflammatory Bioactivities for the Treatment of Zoonotic Skin Pathogens From Canines

The incidence of zoonotic Staphylococcus pseudintermedius and Microsporum canis infections is rapidly growing worldwide in the context of an increasing frequency of close contact between animals and humans, presenting challenges in both human and veterinary medicine. Moreover, the development of microbial resistance and emergence of recalcitrant biofilms, accompanied by the insufficiency of new antimicrobial agents, have become major obstacles in treating superficial skin infections caused by various microbes including S. pseudintermedius and M. canis. Over recent years, the prospects of antimicrobial peptides as emerging antimicrobials to combat microbial infections have been demonstrated. In our study, two novel short-chain peptides, namely, allomyrinasin and andricin B, produced by Allomyrina dichotoma and Andrias davidianus, were revealed to exhibit potent antimicrobial efficacy against clinical isolates of S. pseudintermedius and M. canis with remarkable and rapid fungicidal and bactericidal effects, while allomyrinasin exhibited inhibition of biofilm formation and eradication of mature biofilm. These peptides displayed synergistic activity when combined with amoxicillin and terbinafine against S. pseudintermedius and M. canis. Cytoplasmic leakage via cytomembrane permeabilization serves as a mechanism of action. Extremely low hemolytic activity and serum stability in vitro, as well as superior anti-infective efficacy in reducing bacterial counts and relieving the inflammatory response in vivo, were detected. The potent antibacterial, antifungal, and anti-inflammatory activities of allomyrinasin and andricin B might indicate promising anti-infective alternatives for the treatment of S. pseudintermedius and M. canis infections in the context of human and veterinary medicine.

Sulfonium-based liposome-encapsulated antibiotics deliver a synergistic antibacterial activity

The devastating antibacterial infections, coupled with their antibiotic resistance abilities, emphasize the need for effective antibacterial therapeutics. In this prospect, liposomal delivery systems have been employed in improving the efficacy of the antibacterial agents. The liposome-based antibiotics enhance the therapeutic potential of the new or existing antibiotics and reduce their adverse effects. The current study describes the development of sulfonium-based antibacterial lipids that demonstrate the delivery of existing antibiotics. The presence of cationic sulfonium moieties and inherent membrane targeting abilities of the lipids could help reduce the antibiotic resistance abilities of the bacteria and deliver the antibiotics to remove the infectious pathogens electively. The transmission electron microscopic images and dynamic light scattering analyses revealed the liposome formation abilities of the sulfonium-based amphiphilic compounds in the aqueous medium. The effectiveness of the compounds was tested against the Gram-negative and Gram-positive bacterial strains. The viability of the bacterial cells was remarkably reduced in the presence of the compounds. The sulfonium-based compounds with pyridinium moiety and long hydrocarbon chains showed the most potent antibacterial activities among the tested compounds. Mechanistic studies revealed the membrane-targeted bactericidal activities of the compounds. The potent compound also showed tetracycline and amoxicillin encapsulation and sustained release profiles in the physiologically relevant medium. The tetracycline and amoxicillin-encapsulated lipid showed much higher antibacterial activities than the free antibiotics at similar concentrations, emphasizing the usefulness of the synergistic effect of sulfonium-based lipid and the antibiotics, signifying that the sulfonium lipid penetrated the bacterial membrane and increased the cellular uptake of the antibiotics. The potent lipid also showed therapeutic potential, as it is less toxic to mammalian cells (like HeLa and HaCaT cells) at concentrations higher than their minimum inhibitory concentration values against S. aureus, E. coli, and MRSA. Hence, the sulfonium-based lipid exemplifies a promising framework for assimilating various warheads, and provides a potent antibacterial material.

Severe Form of Bacterial Meningitis After Spine Surgery: A Case Report and Review of the Literature

Meningitis after spine surgery is a rare complication. In this report, we aim to discuss the case of a male patient who developed this rare condition after undergoing cervical spine surgery with devastating outcomes. We also engage in a review of the relevant literature. A 17-year-old boy presented with post-traumatic cervical kyphotic deformity with signs of cord compression. He was operated in three stages, all conducted in a single sitting. There was an incidental cerebrospinal fluid (CSF) leak, which was primarily repaired. On the fourth postoperative day, the patient developed altered sensorium and seizures. Evaluations for clinical signs of meningitis such as neck rigidity and Kernig's sign were inconclusive. CSF analysis confirmed the diagnosis of meningitis. Thereafter, the patient developed hydrocephalus and intractable infection, for which multiple procedures were done. Finally, we succeeded in controlling the infection, but the patient developed a neurological deficit, which did not resolve even after 2.5 years of follow-up. The clinical signs and symptoms of meningitis after cervical spine surgery are not very clear or suggestive. A strong index of suspicion should be maintained for the early detection of this condition to prevent devastating complications that result from it.

Synthesis and design of Ag-Fe bimetallic nanoparticles as antimicrobial synergistic combination therapies against clinically relevant pathogens

The inappropriate use of antibiotics and the inadequate control of infections have led to the emergence of drug-resistant strains. In recent years, metallo-pharmaceutics and metallic nanoparticles have been proposed as potential alternative antimicrobials due to their broad-spectrum antimicrobial properties. Moreover, recent findings have shown that combinations of transition metal compounds can exhibit synergistic antimicrobial properties. Therefore, the synthesis and design of bimetallic nanoparticles is a field worth exploring to harness the interactions between groups of metals and organic complex structures found in different microbial targets, towards the development of more efficient combinatorial antimicrobials composed of synergistic metals. In this study, we present a green synthesis of Ag–Fe bimetallic nanoparticles using an aqueous extract from the leaves of Gardenia jasminoides. The characterization of the nanoparticles demonstrated that the synthesis methodology produces homogenously distributed core–shell Ag–Fe structures with spherical shapes and average diameter sizes of 13 nm (± 6.3 nm). The Ag–Fe bimetallic nanoparticles showed magnetic and antimicrobial properties; the latter were evaluated against six different, clinically relevant multi-drug-resistant microbial strains. The Ag–Fe bimetallic nanoparticles exhibited an antimicrobial (bactericidal) synergistic effect between the two metals composing the bimetallic nanoparticles compared to the effects of the mono-metallic nanoparticles against yeast and both Gram-positive and Gram-negative multidrug-resistant bacteria. Our results provide insight towards the design of bimetallic nanoparticles, synthesized through green chemistry methodologies, to develop synergistic combinatorial antimicrobials with possible applications in both industrial processes and the treatment of infections caused by clinically relevant drug-resistant strains.

Bioenergetic Inhibitors: Antibiotic Efficacy and Mechanisms of Action in Mycobacterium tuberculosis

Development of novel anti-tuberculosis combination regimens that increase efficacy and reduce treatment timelines will improve patient compliance, limit side-effects, reduce costs, and enhance cure rates. Such advancements would significantly improve the global TB burden and reduce drug resistance acquisition. Bioenergetics has received considerable attention in recent years as a fertile area for anti-tuberculosis drug discovery. Targeting the electron transport chain (ETC) and oxidative phosphorylation machinery promises not only to kill growing cells but also metabolically dormant bacilli that are inherently more drug tolerant. Over the last two decades, a broad array of drugs targeting various ETC components have been developed. Here, we provide a focused review of the current state of art of bioenergetic inhibitors of Mtb with an in-depth analysis of the metabolic and bioenergetic disruptions caused by specific target inhibition as well as their synergistic and antagonistic interactions with other drugs. This foundation is then used to explore the reigning theories on the mechanisms of antibiotic-induced cell death and we discuss how bioenergetic inhibitors in particular fail to be adequately described by these models. These discussions lead us to develop a clear roadmap for new lines of investigation to better understand the mechanisms of action of these drugs with complex mechanisms as well as how to leverage that knowledge for the development of novel, rationally-designed combination therapies to cure TB.

Antibacterial Activity of Fluorobenzoylthiosemicarbazides and Their Cyclic Analogues with 1,2,4-Triazole Scaffold

The development of drug-resistant bacteria is currently one of the major challenges in medicine. Therefore, the discovery of novel lead structures for the design of antibacterial drugs is urgently needed. In this structure-activity relationship study, a library of ortho-, meta-, and para-fluorobenzoylthiosemicarbazides, and their cyclic analogues with 1,2,4-triazole scaffold, was created and tested for antibacterial activity against Gram-positive bacteria strains. While all tested 1,2,4-triazoles were devoid of potent activity, the antibacterial response of the thiosemicarbazides was highly dependent on substitution pattern at the N4 aryl position. The optimum activity for these compounds was found for trifluoromethyl derivatives such as 15a, 15b, and 16b, which were active against both the reference strains panel, and pathogenic methicillin-sensitive and methicillin-resistant Staphylococcus aureus clinical isolates at minimal inhibitory concentrations (MICs) ranging from 7.82 to 31.25 μg/mL. Based on the binding affinities obtained from docking, the conclusion can be reached that fluorobenzoylthiosemicarbazides can be considered as potential allosteric d-alanyl-d-alanine ligase inhibitors.

The ecology of plasmid-coded antibiotic resistance: a basic framework for experimental research and modeling

Many antibiotic resistance genes are associated with plasmids. The ecological success of these mobile genetic elements within microbial communities depends on varying mechanisms to secure their own propagation, not only on environmental selection. Among the most important are the cost of plasmids and their ability to be transferred to new hosts through mechanisms such as conjugation. These are regulated by dynamic control systems of the conjugation machinery and genetic adaptations that plasmid-host pairs can acquire in coevolution. However, in complex communities, these processes and mechanisms are subject to a variety of interactions with other bacterial species and other plasmid types. This article summarizes basic plasmid properties and ecological principles particularly important for understanding the persistence of plasmid-coded antibiotic resistance in aquatic environments. Through selected examples, it further introduces to the features of different types of simulation models such as systems of ordinary differential equations and individual-based models, which are considered to be important tools to understand these complex systems. This ecological perspective aims to improve the way we study and understand the dynamics, diversity and persistence of plasmids and associated antibiotic resistance genes.

Reasons for antimicrobial treatment failures and predictive value of in-vitro susceptibility testing in veterinary practice: An overview

The choice of the most suitable antimicrobial agent for the treatment of an animal suffering from a bacterial infection is a complex issue. The results of bacteriological diagnostics and the in-vitro antimicrobial susceptibility testing (AST) provide guidance of potentially suitable antimicrobials. However, harmonized AST methods, veterinary-specific interpretive criteria and quality control ranges, which are essential to conduct AST in-vitro and to evaluate the corresponding results lege artis, are not available for all antimicrobial compounds, bacterial pathogens, animal species and sites of infection of veterinary relevance. Moreover, the clinical benefit of an antimicrobial agent (defined as its in vivo efficacy) is not exclusively dependent on the in-vitro susceptibility of the target pathogen. Apart from the right choice of an antibacterial drug with suitable pharmacokinetic properties and an appropriate pharmaceutical formulation, the success of treatment depends substantially on its adequate use. Even if this is ensured and in-vitro susceptibility confirmed, an insufficient improvement of clinical signs might be caused by biofilm-forming bacteria, persisters, or specific physicochemical conditions at the site of infection, such as pH value, oxygen partial pressure and perfusion rate. This review summarizes relevant aspects that have an impact on the predictive value of in-vitro AST and points out factors, potentially leading to an ineffective outcome of antibacterial treatment in veterinary practice. Knowing the reasons of inadequate beneficial effects can help to understand possible discrepancies between in-vitro susceptibility and in vivo efficacy and aid in undertaking strategies for an avoidance of treatment failures.

Antimicrobial Evaluation of Latex and TLC Fractions from the Leaves of Aloe adigratana Reynolds

Background

The highest prevalence and emergence of microbial infections coupled with the threat of antimicrobial resistance constitute a global concern, which entails searching for novel antimicrobial agents. Medicinal plants are among the major sources of medicines for novel drug discovery. Aloe adigratana is one of the endemic Aloe species in Ethiopia where the leaf latex of the plant is traditionally used for the treatment of various pathogenic conditions such as wound, dandruff, malaria, and diabetes. In spite of such claims, there was no scientific study done so far. The aim of the current study was, therefore, to evaluate the antimicrobial effect of leaf latex of A. adigratana and its thin layer chromatography (TLC) fractions.

Methods

Thin layer chromatography (TLC) separation was employed for isolation of bioactive compounds. Agar well diffusion and microdilution assay method were used to evaluate the antimicrobial actions of the leaf latex and TLC fractions against six bacterial strains and four Candida species of reference and clinical isolate microbial strains.

Results

Three major fractions, AA01, AA02, and AA03, were identified by TLC. Among the tested microbial strains, the reference strain of Staphylococcus aureus ATCC 29213 (MIC = 0.06 mg/mL) and clinical Candida krusei 242/18 (MIC = 0.14 mg/mL) exhibited higher susceptibility towards AA02, while reference strains of Klebsiella pneumoniae ATCC 700603 (MIC = 0.19 mg/mL) revealed the highest susceptibility towards AA01. The leaf latex displayed the highest activity against Staphylococcus aureus ATCC 29213 and clinical Candida krusei 242/18 with a MIC value of 0.19 mg/mL.

Conclusion

The leaf latex and TLC fractions were found to be active against the tested bacterial and Candida species. Therefore, this finding supports the traditional claim of Aloe adigratana and the need for characterization of the TLC fractions to provide as lead compounds for further comprehensive antibacterial and antifungal activities.

In vitro killing of canine strains of Staphylococcus pseudintermedius and Escherichia coli by cefazolin, cefovecin, doxycycline and pradofloxacin over a range of bacterial densities

Background

Bacterial densities likely fluctuate during infection and may exceed the bacterial density used in susceptibility testing. As such, investigation of bacterial killing by antibiotics over a range of varying bacterial densities may provide important differences between compounds and could impact drug selection for therapy.

Hypothesis/Objectives

To measure killing of clinical isolates of Staphylococcus pseudintermedius and Escherichia coli by cefazolin, cefovecin, doxycycline and pradofloxacin at clinically relevant (minimum inhibitory, mutant prevention, maximum serum and maximum tissue) drug concentrations against varying densities of bacteria.

Animals/Materials

Bacterial strains collected from dogs with urinary tract infections were studied.

Methods and materials

High bacterial densities ranging from 10⁶ to 10⁹ colony forming units (cfu)/mL were exposed to minimum inhibitory, mutant prevention, blood and tissue drug concentrations, and the percentages (log₁₀) of viable cells killed following 30 min, 1, 2, 4, 6, 12 and 24 h of drug exposure were quantified.

Results

Doxycycline exhibited bacteriostatic properties with less killing than the other three agents. For example, at a 10⁷ cfu/mL density of S. pseudintermedius, more cells were killed by pradofloxacin (P < 0.0001) and cefovecin (P = 0.0014) but not cefazolin when compared to doxycycline at the maximum serum drug concentration following 12 h of drug exposure.

Conclusions and clinical importance

Differences were seen between some drugs in the speed and extent of bacterial killing; this could be clinically important and may impact drug selection and length of therapy.

Background – Bacterial densities likely fluctuate during infection and may exceed the bacterial density used in susceptibility testing. As such, investigation of bacterial killing by antibiotics over a range of varying bacterial densities may provide important differences between compounds and could impact drug selection for therapy. Hypothesis – To measure killing of clinical isolates of Staphylococcus pseudintermedius and Escherichia coli by cefazolin, cefovecin, doxycycline and pradofloxacin at clinically relevant (minimum inhibitory, mutant prevention, maximum serum and maximum tissue) drug concentrations against varying densities of bacteria. Conclusions and clinical importance – Differences were seen between some drugs in the speed and extent of bacterial killing; this could be clinically important and may impact drug selection and length of therapy.

Mechanisms of Action for Antimicrobial Peptides With Antibacterial and Antibiofilm Functions

The antibiotic crisis has led to a pressing need for alternatives such as antimicrobial peptides (AMPs). Recent work has shown that these molecules have great potential not only as antimicrobials, but also as antibiofilm agents, immune modulators, anti-cancer agents and anti-inflammatories. A better understanding of the mechanism of action (MOA) of AMPs is an important part of the discovery of more potent and less toxic AMPs. Many models and techniques have been utilized to describe the MOA. This review will examine how biological assays and biophysical methods can be utilized in the context of the specific antibacterial and antibiofilm functions of AMPs.

Reactive oxygen species play a dominant role in all pathways of rapid quinolone-mediated killing

Background

Quinolones have been thought to rapidly kill bacteria in two ways: (i) quinolone-topoisomerase-DNA lesions stimulate the accumulation of toxic reactive oxygen species (ROS); and (ii) the lesions directly cause lethal DNA breaks. Traditional killing assays may have underestimated the ROS contribution by overlooking the possibility that ROS continue to accumulate and kill cells on drug-free agar after quinolone removal.

Methods

Quinolone-induced, ROS-mediated killing of Escherichia coli was measured by plating post-treatment samples on agar with/without anti-ROS agents.

Results

When E. coli cultures were treated with ciprofloxacin or moxifloxacin in the presence of chloramphenicol (to accentuate DNA-break-mediated killing), lethal activity, revealed by plating on quinolone-free agar, was inhibited by supplementing agar with ROS-mitigating agents. Moreover, norfloxacin-mediated lethality, observed with cells suspended in saline, was blocked by inhibitors of ROS accumulation and exacerbated by a katG catalase deficiency that impairs peroxide detoxification. Unlike WT cells, the katG mutant was killed by nalidixic acid or norfloxacin with chloramphenicol present and by nalidixic or oxolinic acid with cells suspended in saline. ROS accumulated after quinolone removal with cultures either co-treated with chloramphenicol or suspended in saline. Deficiencies in recA or recB reduced the protective effects of ROS-mitigating agents, supporting the idea that repair of quinolone-mediated DNA lesions suppresses the direct lethal effects of such lesions.

Conclusions

ROS are the dominant factor in all modes of quinolone-mediated lethality, as quinolone-mediated primary DNA lesions are insufficient to kill without triggering ROS accumulation. ROS-stimulating adjuvants may enhance the lethality of quinolones and perhaps other antimicrobials.

Evaluation of the Antimicrobial Peptide, RP557, for the Broad-Spectrum Treatment of Wound Pathogens and Biofilm

The relentless growth of multidrug resistance and generation of recalcitrant biofilm are major obstacles in treating wounds, particularly in austere military environments where broad-spectrum pathogen coverage is needed. Designed antimicrobial peptides (dAMPs) are constructed analogs of naturally occurring AMPs that provide the first line of defense in many organisms. RP557 is a dAMP resulting from iterative rational chemical structural analoging with endogenous AMPs, human cathelicidin LL-37 and Tachyplesin 1 and the synthetic D2A21 used as structural benchmarks. RP557 possesses broad spectrum activity against Gram-positive and Gram-negative bacteria and fungi, including recalcitrant biofilm with substantial selective killing over bacterial cells compared to mammalian cells. RP557 did not induce resistance following chronic passages of Pseudomonas aeruginosa and Staphylococcus aureus at subinhibitory concentrations, whereas concurrently run conventional antibiotics, gentamycin, and clindamycin, did. Furthermore, RP557 was able to subsequently eliminate the generated gentamycin resistant P. aeruginosa and clindamycin resistant S. aureus strains without requiring an increase in minimum inhibitory concentration (MIC) concentrations. RP557 was evaluated further in a MRSA murine wound abrasion infection model with a topical application of 0.2% RP557, completely eliminating infection. If these preclinical results are translated into the clinical setting, RP557 may become crucial for the empirical broad-spectrum treatment of wound pathogens, so that infections can be reduced to a preventable complication of combat-related injuries.

Association between vancomycin pharmacokinetic/pharmacodynamic parameters, patient characteristics, and mortality in patients with bacteremia caused by vancomycin-susceptible Enterococcus faecium: a single-center retrospective study

Background

Vancomycin is commonly used to treat Enterococcus faecium (E. faecium) bacteremia. However, there are very few studies on the association between the trough concentration, area under the curve from 0 to 24 h /minimum inhibitory concentration (AUC₂₄/MIC) ratio, and the therapeutic effect of vancomycin on E. faecium bacteremia. This study aimed to investigate the associations between vancomycin pharmacokinetic/pharmacodynamic parameters, patient characteristics, and mortality in patients with E. faecium bacteremia.

Methods

This retrospective study included patients with E. faecium bacteremia who received vancomycin between April 2012 and February 2018 at a single acute care hospital in Japan. Patients who received renal replacement therapy (hemodialysis or continuous hemodiafiltration), had an unmeasured serum vancomycin concentration, with unmeasured laboratory values, or received other antibiotics for treating E. faecium bacteremia were excluded from the study. The bivariate associations between 30-day all-cause mortality and patient characteristics were assessed.

Results

Among 87 patients diagnosed with E. faecium bacteremia, 45 were included in the final analysis. Of these, 12 (26.7%) died within 30 days of the diagnosis. The vancomycin trough concentration was higher in the 30-day all-cause mortality patients than in the survival patients (20.5 vs. 14.6 μg/mL; P = 0.022). There was no significant difference in the proportion of patients with a vancomycin AUC₂₄/MIC ≤389 between the groups. The 30-day all-cause mortality patients showed a higher Charlson Comorbidity Index (CCI) and Sequential Organ Failure Assessment score at the first measurement of the vancomycin trough concentration than the survival patients. The same finding was observed among patients with a high CCI score (≥5 points).

Conclusions

Whereas the vancomycin trough concentration and AUC₂₄/MIC ratio were not associated with mortality in patients with E. faecium bacteremia, disease severity was associated with mortality in these patients.

Behavioral profile alterations in zebrafish larvae exposed to environmentally relevant concentrations of eight priority pharmaceuticals

Although the effects of pharmaceuticals on aquatic organisms have been widely investigated during the last decades, toxic effects, especially delayed toxicity, during the developmental stage at environmental relevant concentrations were rarely known. In this study, a sensitive assay based on behavioral alterations was used for studying the delayed toxicity during the developmental stage on zebrafish embryos. Eight pharmaceuticals that were frequently detected with concentrations ranging from ng/l to μg/l were screened for this study. Behavioral alterations of zebrafish at 118 hpf (hours post fertilization) after exposing to eight single pharmaceuticals with concentrations in the ranges of environmental detected and their mixtures during embryonic development (2-50 h post fertilization, hpf) were observed. Multiple endpoints, including mortality, hatching rate, swimming speed and angular velocity were evaluated. Results showed that behavioral profile alterations in zebrafish larvae are promising for predicting delayed sublethal effects of chemicals. Delayed hatch was observed at 72 hpf following embryonic exposure to triclosan (1 μg/l) and carbamazepine (100 μg/l) up to 50 hpf. The zebrafish larval locomotor behavior following embryonic exposure to 0.1 μg/l triclosan and 1 μg/l caffeine in the early stages of development (2-50 hpf) was altered. Furthermore, the effects of the mixture of 8 pharmaceuticals each with the highest environmental concentration on larval behavior were observed during embryonic development. Generally, this study showed that the effects of pharmaceuticals singly or their mixtures in surface waters cannot be ignored.

Antimicrobial agents for preventing urinary tract infections in adults undergoing cystoscopy

BACKGROUND

Cystoscopy is commonly performed for diagnostic purposes to inspect the interior lining of the bladder. One disadvantage of cystoscopy is the risk of symptomatic urinary tract infection (UTI) due to pre-existing colonization or by introduction of bacteria at the time of the procedure. However, the incidence of symptomatic UTI following cystoscopy is low. Currently, there is no consensus on whether antimicrobial agents should be used to prevent symptomatic UTI for cystoscopy.

OBJECTIVES

To assess the effects of antimicrobial agents compared with placebo or no treatment for prevention of UTI in adults undergoing cystoscopy.

SEARCH METHODS

We comprehensively searched electronic databases of the Cochrane Library, PubMed, Embase, LILACS, and CINAHL. We searched the WHO ICTRP and ClinicalTrials.gov for ongoing trials. We used no language or date restrictions in the electronic searches. We searched the reference lists of identified articles and contacted authors for related information. The last search of the electronic databases was 4 February 2019.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) or quasi-RCTs that compared any prophylactic antibiotic versus placebo, no treatment, or other non-antibiotic prophylaxis in adults undergoing cystoscopy. There was no restriction on the dose, frequency, formulation, duration, or mode of administration of the antibiotics.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Our primary outcomes were systemic UTI, symptomatic UTI (composite of systemic and/or localized UTI), and serious adverse events. Secondary outcomes were minor adverse events, localized UTI, asymptomatic bacteriuria, and bacterial resistance. We assessed the quality of evidence using GRADE.

MAIN RESULTS

We included 20 RCTs and two quasi-RCTs with 7711 participants, all of which compared antibiotic prophylaxis with placebo or no treatment control. We found no studies comparing antibiotic prophylaxis with non-antibiotic prophylaxis.Primary outcomesSystemic UTI: antibiotic prophylaxis may have little or no effect on the risk of systemic UTI compared with placebo or no treatment (risk ratio (RR) 1.12, 95% confidence interval (CI) 0.38 to 3.32; 5 RCTs; 504 participants; low-quality evidence); this corresponds to two more people (95% CI 12 fewer to 46 more) per 1000 people developing a systemic UTI. We downgraded the quality of the evidence for study limitations and imprecision.Symptomatic UTI: antibiotic prophylaxis may reduce the risk of symptomatic UTI (RR 0.49, 95% CI 0.28 to 0.86; 11 RCTs; 5441 participants; low-quality evidence); this corresponds to 30 fewer people (95% CI 42 fewer to 8 fewer) per 1000 people developing a symptomatic UTI when provided with antibiotic prophylaxis. We downgraded the quality of the evidence for study limitations and potential publication bias.Serious adverse events: the studies reported no serious adverse events in either the intervention group or control group and no effect size could be calculated. Antibiotic prophylaxis may have little or no effect on serious adverse events (4 RCTs, 630 participants; very low-quality evidence), but we are very uncertain of this finding. We downgraded the quality of the evidence for study limitations and very serious imprecision.Secondary outcomesMinor adverse events: prophylactic antibiotics may have little or no effect on minor adverse events when compared with placebo or no treatment (RR 2.82, 95% CI 0.54 to 14.80; 4 RCTs; 630 participants; low-quality evidence). We downgraded the quality of the evidence for study limitations and imprecision.Localized UTI: prophylactic antibiotics may have little or no effect on the risk of localized UTI (RR 1.0, 95% CI 0.06 to 15.77; 1 RCT; 200 participants; very low-quality evidence), but we were very uncertain of this finding. We downgraded the quality of the evidence for study limitations and very serious imprecision.Bacterial resistance: prophylactic antibiotics may increase bacterial resistance (RR 1.73, 95% CI 1.04 to 2.87; 38 participants; 2 RCTs; very low-quality evidence), but we were uncertain of this finding. We downgraded the quality of the evidence for study limitations, indirectness, and imprecision.We were able to perform few secondary analyses; these did not suggest any subgroup effects.

AUTHORS' CONCLUSIONS

Antibiotic prophylaxis may reduce the risk of symptomatic UTI but not systemic UTIs. Serious and minor adverse events may not be increased with the use of antibiotic prophylaxis. The findings are informed by low- and very low-quality evidence ratings for all outcomes.

Differences in Antibiotic Resistance of MRSA Infections in Patients with Various Types of Otitis Media

OBJECTIVES

We investigated the epidemiological and antibiotic resistance differences in methicillin-resistant Staphylococcus aureus (MRSA) infections in patients with otitis media with effusion (OME), acute otitis media (AOM), chronic suppurative otitis media (CSOM), and chronic cholesteatomatous otitis media (CCOM).

MATERIALS AND METHODS

We conducted a retrospective study of patients with newly identified MRSA infections from January 2009 through January 2017. Overall, 3,522 patients from 10 tertiary referral hospitals were included in the study. An antibiotic sensitivity test was performed for each isolate.

RESULTS

MRSA infections in patients with CSOM and CCOM were more resistant to ciprofloxacin, clindamycin, erythromycin, gentamicin, levofloxacin, and tetracycline. Patients showed good susceptibility to rifampicin, trimethoprim/sulfamethoxazole (TMP/SMX), and vancomycin.

CONCLUSION

MRSA infections in various otitis media cases showed different resistance patterns. MRSA infections in patients with COM and CCOM were more resistant to antibiotics than those in patients with OME and AOM.

Biguanide Iridium(III) Complexes with Potent Antimicrobial Activity

We have synthesized novel organoiridium(III) antimicrobial complexes containing a chelated biguanide, including the antidiabetic drug metformin. These 16- and 18-electron complexes were characterized by NMR, ESI-MS, elemental analysis, and X-ray crystallography. Several of these complexes exhibit potent activity against Gram-negative bacteria and Gram-positive bacteria (including methicillin-resistant Staphylococcus aureus (MRSA)) and high antifungal potency toward C. albicans and C. neoformans, with minimum inhibitory concentrations (MICs) in the nanomolar range. Importantly, the complexes exhibit low cytotoxicity toward mammalian cells, indicating high selectivity. They are highly stable in broth medium, with a low tendency to generate resistance mutations. On coadministration, they can restore the activity of vancomycin against vancomycin-resistant Enterococci (VRE). Also the complexes can disrupt and eradicate bacteria in mature biofilms. Investigations of reactions with biomolecules suggest that these organometallic complexes deliver active biguanides into microorganisms, whereas the biguanides themselves are inactive when administered alone.

Alkynyl-containing phenylthiazoles: Systemically active antibacterial agents effective against methicillin-resistant Staphylococcus aureus (MRSA)

The promising activity of phenylthiazoles against multidrug-resistant bacterial pathogens, in particular MRSA, has been hampered by their limited systemic applicability, due to their rapid metabolism by hepatic microsomal enzymes, resulting in short half-lives. Here, we investigated a series of phenylthiazoles with alkynyl side-chains that were synthesized with the objective of improving stability to hepatic metabolism, extending the utility of phenylthiazoles from topical applications to treatment of a more invasive, systemic MRSA infections. The most promising compounds inhibited the growth of clinically-relevant isolates of MRSA in vitro at concentrations as low as 0.5 μg/mL, and exerted their antibacterial effect by interfering with bacterial cell wall synthesis via inhibition of undecaprenyl diphosphate synthase and undecaprenyl diphosphate phosphatase. We also identified two phenylthiazoles that successfully eradicated MRSA inside infected macrophages. In vivo PK analysis of compound 9 revealed promising stability to hepatic metabolism with a biological half-life of ∼4.5 h. In mice, compound 9 demonstrated comparable potency to vancomycin, and at a lower dose (20 mg/kg versus 50 mg/kg), in reducing the burden of MRSA in a systemic, deep-tissue infection, using the neutropenic mouse thigh-infection model. Compound 9 thus represents a new phenylthiazole lead for the treatment of MRSA infections that warrants further development.

The in vitro, in vivo antifungal activity and the action mode of Jelleine-I against Candida species

Recently, the mortality of life-threatening fungal infections increased dramatically. However, there are few antifungals existed. Antimicrobial peptides (AMPs) as promising antifungal candidates have attracted much attention. Here, we present a small antimicrobial peptide Jelleine-I that had potent in vitro and in vivo antifungal activity. Negligible hemolytic activity and in vivo toxicity were observed. Selectivity index (SI) of Jelleine-I is at least 4.6 times higher than amphotericin B. Jelleine-I could increase the production of cellular ROS and bind with genome DNA. This may contribute to its antifungal activity. Furthermore, drug resistance is not induced when the fungal cells were repeatedly treated by Jelleine-I. In conclusion, our results suggest that Jelleine-I may have the potential to be developed as a novel antifungal agent.

Bacterial sepsis in the neonate

Neonatal bacterial infections leading to sepsis occur frequently in the first few days or weeks of life. NPs must be able to recognize the early signs of sepsis and understand the need for rapid evaluation and treatment. This article discusses antibiotic treatments for various types and locations of bacterial infections and sepsis in the neonate.

Phagocytes, Antibiotics, and Self-Limiting Bacterial Infections

Most antibiotic use in humans is to reduce the magnitude and term of morbidity of acute, community-acquired infections in immune competent patients, rather than to save lives. Thanks to phagocytic leucocytes and other host defenses, the vast majority of these infections are self-limiting. Nevertheless, there has been a negligible amount of consideration of the contribution of phagocytosis and other host defenses in the research for, and the design of, antibiotic treatment regimens, which hyper-emphasizes antibiotics as if they were the sole mechanism responsible for the clearance of infections. Here, we critically review this approach and its limitations. With the aid of a heuristic mathematical model, we postulate that if the rate of phagocytosis is great enough, for acute, normally self-limiting infections, then (i) antibiotics with different pharmacodynamic properties would be similarly effective, (ii) low doses of antibiotics can be as effective as high doses, and (iii) neither phenotypic nor inherited antibiotic resistance generated during therapy are likely to lead to treatment failure.

Translational Pharmacometric Evaluation of Typical Antibiotic Broad-Spectrum Combination Therapies Against Staphylococcus Aureus Exploiting In Vitro Information

Broad‐spectrum antibiotic combination therapy is frequently applied due to increasing resistance development of infective pathogens. The objective of the present study was to evaluate two common empiric broad‐spectrum combination therapies consisting of either linezolid (LZD) or vancomycin (VAN) combined with meropenem (MER) against Staphylococcus aureus (S. aureus) as the most frequent causative pathogen of severe infections. A semimechanistic pharmacokinetic‐pharmacodynamic (PK‐PD) model mimicking a simplified bacterial life‐cycle of S. aureus was developed upon time‐kill curve data to describe the effects of LZD, VAN, and MER alone and in dual combinations. The PK‐PD model was successfully (i) evaluated with external data from two clinical S. aureus isolates and further drug combinations and (ii) challenged to predict common clinical PK‐PD indices and breakpoints. Finally, clinical trial simulations were performed that revealed that the combination of VAN‐MER might be favorable over LZD‐MER due to an unfavorable antagonistic interaction between LZD and MER.

Investigating the Antibacterial Activity of Biphenylthiazoles against Methicillin- and Vancomycin-Resistant Staphylococcus aureus (MRSA and VRSA)

Phenylthiazoles were reported previously as a new scaffold with antibacterial activity against an array of multidrug-resistant staphylococci. However, their promising antibacterial activity was hampered in large part by their short half-life due to excessive hepatic clearance. Close inspection of the structure-activity-relationships (SARs) of the phenylthiazoles revealed two important structural features necessary for antibacterial activity (a nitrogenous and a lipophilic component). Incorporating the nitrogenous part within a pyrimidine ring resulted in analogues with a prolonged half-life, while the biphenyl moiety revealed the most potent analogue 1b. In this study, advantageous moieties have been combined to generate a new hybrid scaffold of 5-pyrimidinylbiphenylthiazole with the objective of enhancing both anti-MRSA activity and drug-like properties. Among the 37 tested biphenylthiazoles, piperazinyl-containing derivatives 10, 30, and 36 were the most potent analogues with MIC values as low as 0.39 μg/mL. Additionally, 36 exhibited significant improvement in stability to hepatic metabolism.

Nanosuspensions in Nanobiomedicine

The tremendous success in developing new nanomaterials and fostering technological innovation arises from the focus on interdisciplinary research and collaboration between physical and medical scientists. The concept of nano-medicine is one of the most important and exciting ideas ever generated by the applications of nanoscience. One of the most challenging tasks in the pharmaceutical industry is the formulation of poorly soluble drugs. The implication of conventional techniques for improving the solubility has gained limited success. Nanoparticles facilitate formulation with improved solubility and efficacy mainly through nanosuspension approach. Techniques such as media milling, high-pressure homogenization, and use of microemulsion have been used for production of nanosuspensions for a novel delivery system. Moreover, they are manoeuvred to patient-acceptable dosage forms like tablets, capsules, and lyophilized powder products. Nanosuspension technology has also been studied for active and passive targeted drug delivery systems, which the chapter highlights on various formulational perspectives and applications as a biomedicine delivery system.

Synthesis and Complete Antimicrobial Characterization of CEOBACTER, an Ag-Based Nanocomposite

The antimicrobial activity of silver nanoparticles (AgNPs) is currently used as an alternative disinfectant with diverse applications, ranging from decontamination of aquatic environments to disinfection of medical devices and instrumentation. However, incorporation of AgNPs to the environment causes collateral damage that should be avoided. In this work, a novel Ag-based nanocomposite (CEOBACTER) was successfully synthetized. It showed excellent antimicrobial properties without the spread of AgNPs into the environment. The complete CEOBACTER antimicrobial characterization protocol is presented herein. It is straightforward and reproducible and could be considered for the systematic characterization of antimicrobial nanomaterials. CEOBACTER showed minimal bactericidal concentration of 3 μg/ml, bactericidal action time of 2 hours and re-use capacity of at least five times against E. coli cultures. The bactericidal mechanism is the release of Ag ions. CEOBACTER displays potent bactericidal properties, long lifetime, high stability and re-use capacity, and it does not dissolve in the solution. These characteristics point to its potential use as a bactericidal agent for decontamination of aqueous environments.