New antibiotics for bad bugs: where are we?

PharmaRedefine: A database server for repurposing drugs against pathogenic bacteria

Pathogenic bacteria represent a formidable threat to human health, necessitating substantial resources for prevention and treatment. With the escalating concern regarding antibiotic resistance, there is a pressing need for innovative approaches to combat these pathogens. Repurposing existing drugs offers a promising solution. Our present work hypothesizes that proteins harboring ligand-binding pockets with similar chemical environments may be able to bind the same drug. To facilitate this drug-repurposing strategy against pathogenic bacteria, we introduce an online server, PharmaRedefine. Leveraging a combination of sequence and structure alignment and protein pocket similarity analysis, this platform enables the prediction of potential targets in representative bacteria for specific FDA-approved drugs. This novel approach holds tremendous potential for drug repositioning that effectively combat infections caused by pathogenic bacteria. PharmaRedefine is freely available at http://guolab.mpu.edu.mo/pharmredefine.

Keeping up with the pathogens: improved antimicrobial resistance detection and prediction from Pseudomonas aeruginosa genomes

BACKGROUND

Antimicrobial resistance (AMR) is an intensifying threat that requires urgent mitigation to avoid a post-antibiotic era. Pseudomonas aeruginosa represents one of the greatest AMR concerns due to increasing multi- and pan-drug resistance rates. Shotgun sequencing is gaining traction for in silico AMR profiling due to its unambiguity and transferability; however, accurate and comprehensive AMR prediction from P. aeruginosa genomes remains an unsolved problem.

METHODS

We first curated the most comprehensive database yet of known P. aeruginosa AMR variants. Next, we performed comparative genomics and microbial genome-wide association study analysis across a Global isolate Dataset (n = 1877) with paired antimicrobial phenotype and genomic data to identify novel AMR variants. Finally, the performance of our P. aeruginosa AMR database, implemented in our AMR detection and prediction tool, ARDaP, was compared with three previously published in silico AMR gene detection or phenotype prediction tools-abritAMR, AMRFinderPlus, ResFinder-across both the Global Dataset and an analysis-naïve Validation Dataset (n = 102).

RESULTS

Our AMR database comprises 3639 mobile AMR genes and 728 chromosomal variants, including 75 previously unreported chromosomal AMR variants, 10 variants associated with unusual antimicrobial susceptibility, and 281 chromosomal variants that we show are unlikely to confer AMR. Our pipeline achieved a genotype-phenotype balanced accuracy (bACC) of 85% and 81% across 10 clinically relevant antibiotics when tested against the Global and Validation Datasets, respectively, vs. just 56% and 54% with abritAMR, 58% and 54% with AMRFinderPlus, and 60% and 53% with ResFinder. ARDaP's superior performance was predominantly due to the inclusion of chromosomal AMR variants, which are generally not identified with most AMR identification tools.

CONCLUSIONS

Our ARDaP software and associated AMR variant database provides an accurate tool for predicting AMR phenotypes in P. aeruginosa, far surpassing the performance of current tools. Implementation of ARDaP for routine AMR prediction from P. aeruginosa genomes and metagenomes will improve AMR identification, addressing a critical facet in combatting this treatment-refractory pathogen. However, knowledge gaps remain in our understanding of the P. aeruginosa resistome, particularly the basis of colistin AMR.

Integrating Artificial DNAzymes with Natural Enzymes on 2D MOF Hybrid Nanozymes for Enhanced Treatment of Bacteria-Infected Wounds

Removal of invasive bacteria is critical for proper wound healing. This task is challenging because these bacteria can trigger intense oxidative stress and gradually develop antibiotic resistance. Here, the use of a multienzyme-integrated nanocatalytic platform is reported for efficient bacterial clearance and mitigation of inflammatory responses, constructed by physically adsorbing natural superoxide dismutase (SOD), in situ reduction of gold nanoparticles (Au NPs), and incorporation of a DNAzyme on 2D NiCoCu metal-organic frameworks (DNAzyme/SOD/Au@NiCoCu MOFs, termed DSAM), which can adapt to infected wounds. O2 and H2O2 replenishment is achieved and alleviated the hypoxic microenvironment using the antioxidant properties of SOD. The H2O2 produced during the reaction is decomposed by peroxidase (POD)-like activity enhanced by Au NPs and DNAzyme, releasing highly toxic hydroxyl radicals (•OH) to kill the bacteria. In addition, it possesses glutathione peroxidase (GPx)-like activity, which depletes GSH and prevents •OH loss. Systematic antimicrobial tests are performed against bacteria using this multienzyme-integrated nanoplatform. A dual-mode strategy involving natural enzyme-enhanced antioxidant capacity and artificial enzyme-enhanced •OH release to develop an efficient and novel enzyme-integrated therapeutic platform is integrated.

Cephalosporin resistance, tolerance, and approaches to improve their activities

Cephalosporins comprise a β-lactam antibiotic class whose first members were discovered in 1945 from the fungus Cephalosporium acremonium. Their clinical use for Gram-negative bacterial infections is widespread due to their ability to traverse outer membranes through porins to gain access to the periplasm and disrupt peptidoglycan synthesis. More recent members of the cephalosporin class are administered as last resort treatments for complicated urinary tract infections, MRSA, and other multi-drug resistant pathogens, such as Neisseria gonorrhoeae. Unfortunately, there has been a global increase in cephalosporin-resistant strains, heteroresistance to this drug class has been a topic of increasing concern, and tolerance and persistence are recognized as potential causes of cephalosporin treatment failure. In this review, we summarize the cephalosporin antibiotic class from discovery to their mechanisms of action, and discuss the causes of cephalosporin treatment failure, which include resistance, tolerance, and phenomena when those qualities are exhibited by only small subpopulations of bacterial cultures (heteroresistance and persistence). Further, we discuss how recent efforts with cephalosporin conjugates and combination treatments aim to reinvigorate this antibiotic class.

A systematic review of peptide nucleic acids (PNAs) with antibacterial activities: Efficacy, potential and challenges

Peptide nucleic acids (PNAs) are synthetic molecules that are like DNA/RNA, but with different building blocks. PNAs target and bind to mRNAs and disrupt the function of a targeted gene, hence they have been studied as potential antibacterials. The aim of this systematic review was to provide an in-depth analysis of the current status of PNAs as antibacterial agents, define the characteristics of the effective PNA constructs, and address the gap in advancing PNAs to become clinically competent agents. Following the PRISMA model, four electronic databases were searched: Web of Science, PubMed, SciFinder and Scopus. A total of 627 articles published between 1994 and 2023 were found. After screening and a rigorous selection process using explicit inclusion and exclusion criteria, 65 scientific articles were selected, containing 656 minimum inhibitory concentration (MIC) data. The antibacterial activity of PNAs was assessed against 20 bacterial species. The most studied Gram-negative and Gram-positive bacteria were Escherichia coli (n=266) and Staphylococcus aureus (n=53), respectively. In addition, the effect of PNA design, including construct length, binding location, and carrier agents, on antibacterial activity was shown. Finally, antibacterial test models to assess the inhibitory effects of PNAs were examined, emphasising gaps and prospects. This systematic review provides a comprehensive assessment of the potential of PNAs as antibacterial agents and offers valuable insights for researchers and clinicians seeking novel therapeutic strategies in the context of increasing rates of antibiotic-resistant bacteria.

Clinical outcomes of intensive care unit patients infected with multidrug-resistant gram-negative bacteria treated with ceftazidime/avibactam and ceftolozane/tazobactam

In intensive care units (ICUs), infection rates range from 18 to 54%, which is five to ten times higher than those observed in other hospital units, with a mortality rate of 9% to 60%. In recent decades, the susceptibility pattern has changed and Gram-Negative Bacteria (GNB) have become a threat due to their high frequency of multidrug resistance associated with a scarcity of therapeutic options. However, the drugs Ceftolozane/Tazobactam (C/T) and Ceftazidime/Avibactam (C/A) are demonstrating good clinical and microbiological response in the treatment of severe nosocomial infections. Therefore, this study aims to evaluate the clinical outcome of patients with severe infections caused by Multidrug-Resistant (MDR) GNB treated with C/T and C/A. Our study evaluates a total of 131 patients who received treatment with C/T and C/A due to infections caused by MDR GNB within the period from 2018 to 2021. The main infections were urinary tract (46,6%) and respiratory (26,7%) infections. Pseudomonas aeruginosa was the prevailing agent in the sample evaluation (34.3%), followed by Klebsiella pneumoniae (30,1%). About 54,9% of patients showed a favorable response, with culture negativation in 66,4% of the samples, with no discrepancy in negativations when comparing ages: 67,7% in young and 66% in elderly patients. Among the patients, 62,6% received monotherapy with C/T and C/A with a better response observed with monotherapy compared to combination therapy (58,6% vs 41,4%). The overall mortality rate was 45%, with MDR GNB infections responsible for 33,9% of these deaths, and the others (66,1%) due to factors such as oncological, hematological, and degenerative neurological diseases. In regards to hematological aspect, 35,1% of patients showed changes, with 28,2% of them presenting anemia, 4,5% thrombocytopenia, and 2,5% thrombocytosis. Concerning the use of invasive devices, higher mortality was observed in patients on mechanical ventilation (52%). In this manner, it was possible to observe that therapy with C/T and C/A yielded a favorable clinical outcome in patients with severe infections caused by MDR GNB in the study. These drugs also demonstrated good tolerability regardless of age or the presence of preexisting comorbidities and were deemed safe when assessing adverse effects. Our data also demonstrate the importance of determining the mechanism of resistance to carbapenems so that these drugs can be used more effectively and rationally.

Combined substituent number utilized machine learning for the development of antimicrobial agent

The utilization of machine learning has a potential to improve the environment of the development of antimicrobial agents. For practical use of machine learning, it is important that the conversion of molecules information to an appropriate descriptor because too informative descriptor requires enormous computation time and experiments for gathering data, whereas a less informative descriptor has problems in validity. In this study, we utilized a descriptor only focused on substituent. The type and the position of substituents on the molecules that have a 4-quinolone structure (11,879 compounds) were converted to the combined substituent number (CSN). While the CSN does not include information on the detailed structure, physical properties, and quantum chemistry of molecules, the prediction model constructed by machine learning of CSN indicated a sufficient coefficient of determination (0.719 for the training dataset and 0.519 for the validation dataset). In addition, this CSN can easily construct the unknown molecules library which has a relatively consistent structure by recombination of substituents (32,079,318 compounds) and screening of them. The validity of the prediction model was also confirmed by growth inhibition experiments for E. coli using the model-suggested molecules and commercially available antimicrobial agents.

Novel terpyridines as Staphylococcus aureus gyrase inhibitors: efficient synthesis and antibacterial assessment via solvent-drop grinding

Aim: This study was designed to synthesize a novel series of terpyridines with potential antibacterial properties, targeting multidrug resistance. Materials & methods: Terpyridines (4a-h and 6a-c) were synthesized via a one-pot multicomponent reaction using 2,6-diacetylpyridines, benzaldehyde derivatives and malononitrile or ethyl 2-cyanoacetate. The reactions, conducted under grinding conditions with glacial acetic acid, produced high-yield compounds, confirmed by spectroscopic data. Results: The synthesized terpyridines exhibited potent antibacterial activity. Notably, compounds 4d and 4h demonstrated significant inhibition zones against Staphylococcus aureus and Bacillus subtilis, outperforming ciprofloxacin. Conclusion: Molecular docking studies highlighted compounds 4d, 4h and 6c as having strong binding affinity to DNA gyrase B, correlating with their robust antibacterial activity, suggesting their potential as effective agents against multidrug-resistant bacterial strains.

Integrated Computational and Experimental Framework for Inverse Screening of Candidate Antibacterial Nanomedicine

Nanomedicine is promising for disease prevention and treatment, but there are still many challenges that hinder its rapid development. A major challenge is to efficiently seek candidates with the desired therapeutic functions from tremendously available materials. Here, we report an integrated computational and experimental framework to seek alloy nanoparticles from the Materials Project library for antibacterial applications, aiming to learn the inverse screening concept from traditional medicine for nanomedicine. Because strong peroxidase-like catalytic activity and weak toxicity to normal cells are the desired material properties for antibacterial usage, computational screening implementing theoretical prediction models of catalytic activity and cytotoxicity is first conducted to select the candidates. Then, experimental screening based on scanning probe block copolymer lithography is used to verify and refine the computational screening results. Finally, the best candidate AuCu3 is synthesized in solution and its antibacterial performance over other nanoparticles against S. aureus and E. coli. is experimentally confirmed. The results show the power of inverse screening in accelerating the research and development of antibacterial nanomedicine, which may inspire similar strategies for other nanomedicines in the future.

Chlortetracycline Concentration Impact on Salmonella Typhimurium Sustainability in the Presence of Porcine Gastrointestinal Tract Bacteria Maintained in Continuous Culture

Concern exists that the continued use of antibiotics in animal feeds may lead to an increased prevalence of resistant bacteria within the host animal's gastrointestinal tract. To evaluate the effect of chlortetracycline on the persistence of Salmonella enterica serotype Typhimurium within a diverse population of porcine cecal bacteria, we cultured a mixed population of cecal bacteria without or with added chlortetracycline. When grown at a 24 h vessel turnover rate, chlortetracycline-susceptible S. Typhimurium exhibited more than 2.5 times faster (p < 0.05) disappearance rates than theoretically expected (0.301 log10 colony-forming unit/mL per day) but did not differ whether treated or not with 55 mg of chlortetracycline/L. Chlortetracycline-resistant S. Typhimurium was not recovered from any of these cultures. When the mixed cultures were inoculated with a chlortetracycline-resistant S. Typhimurium, rates of disappearance were nearly two times slower (p < 0.05) than those observed earlier with chlortetracycline-susceptible S. Typhimurium, and cultures persisted at >2 log10 colony-forming units/mL for up to 14 days of treatment with 110 mg of chlortetracycline/L. Under the conditions of this study, chlortetracycline-resistant S. Typhimurium was competitively enabled to persist longer within the mixed populations of porcine gut bacteria than chlortetracycline-susceptible S. Typhimurium, regardless of the presence or absence of added chlortetracycline.

Recent advances in nanoantibiotics against multidrug-resistant bacteria

Multidrug-resistant (MDR) bacteria-caused infections have been a major threat to human health. The abuse of conventional antibiotics accelerates the generation of MDR bacteria and makes the situation worse. The emergence of nanomaterials holds great promise for solving this tricky problem due to their multiple antibacterial mechanisms, tunable antibacterial spectra, and low probabilities of inducing drug resistance. In this review, we summarize the mechanism of the generation of drug resistance, and introduce the recently developed nanomaterials for dealing with MDR bacteria via various antibacterial mechanisms. Considering that biosafety and mass production are the major bottlenecks hurdling the commercialization of nanoantibiotics, we introduce the related development in these two aspects. We discuss urgent challenges in this field and future perspectives to promote the development and translation of nanoantibiotics as alternatives against MDR pathogens to traditional antibiotics-based approaches.

Phenotypic characterization and epidemiology of extended-spectrum β-lactamase-producing Enterobacteriaceae strains from urinary tract infections in Garoua, Cameroon

Background and objectives

The emergence of extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) is causing increased morbidity and mortality around the world as a result of therapeutic failures. ESBL-E are priority pathogens due to their multidrug resistance (MDR). In Northern Cameroon, ESBL-producing bacteria, particularly in urinary tract infections (UTIs), are being increasingly isolated. This study aimed to retrospectively determine the prevalence of multi-drug resistant ESBL strains isolated from UTIs in Northern Cameroon and to evaluate the effectiveness of the ATB UR Gallery of BioMérieux in diagnosing ESBL-E in clinical settings.

Methods

Standard microbiology protocols and statistical tools were utilized to identify ESBL-producing bacteria and characterize their phenotypic susceptibility and resistance profiles in the study population.

Results

Out of the 144 enterobacteria isolates successfully cultured, 59 (41%) were identified as MDR strains. The ATB UR EU gallery identified 33 (23%) multi-drug resistant ESBL-producing strains, while the double synergy test identified 35 strains without disc reconciliation and 38 strains after reconciliation. The most prevalent ESBL-E isolate was Escherichia coli, accounting for 77.1% of the isolates, followed by Klebsiella pneumoniae (20%) and Enterobacter aerogenes (2.9%). Additionally, the study revealed the emergence of Imipenem resistance (5.7%), a critical last-resort antibiotic. However, all ESBL strains were sensitive to Fosfomycin (FSF/FOS), demonstrating its potential as an effective therapeutic option. Moreover, 37% of the ESBL producers exhibited co-resistance to over 20 different antibiotics.

Conclusion

This study provides valuable insights into the prevalence and susceptibility patterns of ESBL-E associated with UTIs in Northern Cameroon. These insights emphasizes the importance of implementing appropriate treatment guidelines and antimicrobial stewardship measures to mitigate the spread and impact of MDR ESBL-producing strains on public health.

Evaluation of the synergistic effect of chitosan metal ions (Cu2+/Co2+) in combination with antibiotics to counteract the effects on antibiotic resistant bacteria

The effectiveness of antibiotics that save millions of lives is in danger due to the increasing rise of resistant bacteria around the world. We proposed chitosan-copper ions (CSNP-Cu²⁺) and chitosan-cobalt ion nanoparticles (CSNP-Co²⁺) as biodegradable nanoparticles loaded with metal ions synthesized via an ionic gelation method for treatment of antibiotic resistant bacteria. The nanoparticles were characterized using TEM, FT-IR, zeta potential and ICP-OES. The MIC was evaluated for the NPs in addition to evaluating the synergetic effect of the nanoparticles in combination with cefepime or penicillin for five different antibiotic resistant bacterial strains. In order to investigate the mode of action, MRSA, DSMZ 28766 and Escherichia coli E0157:H7 were selected for further evaluation of antibiotic resistant genes expression upon treatment with NPs. Finally, the cytotoxic activities were investigated using MCF7, HEPG2 and A549 and WI-38 cell lines. The results showed quasi spherical shape and mean particle size of 19.9 ± 5 nm, 21 ± 5 nm and 22.27 ± 5 for CSNP, CSNP-Cu²⁺ and CSNP-Co²⁺ respectively. FT-IR showed slight shifting of the hydroxyl and amine group's peaks of chitosan indicating the adsorption of metal ions. Both nanoparticles had antibacterial activity with MIC ranging between 125 and 62 μg ml^-1 for the used standard bacterial strains. Moreover, the combination of each of the synthesized NP with either cefepime or penicillin not only showed a synergetic effect as antibacterial activity of each NP or antibiotics alone, but also decreased the fold of antibiotic resistance genes expression. The NPs showed potent cytotoxic activities for MCF-7, HepG2 and A549 cancer cell lines with lower cytotoxic values for the WI-38 normal cell line. The NPs' antibacterial activity may be due to penetration and rupture of the cell membrane and the outer membrane of Gram negative and Gram positive bacteria causing bacterial cell death, in addition to, penetration into the bacterial genes and blocking gene expression that is vital to bacterial growth. The fabricated nanoparticles can be an effective, affordable and biodegradable solution to challenge antibiotic resistant bacteria.

Fish Skin Mucus Extracts: An Underexplored Source of Antimicrobial Agents

The slow discovery of new antibiotics combined with the alarming emergence of antibiotic-resistant bacteria underscores the need for alternative treatments. In this regard, fish skin mucus has been demonstrated to contain a diverse array of bioactive molecules with antimicrobial properties, including peptides, proteins, and other metabolites. This review aims to provide an overview of the antimicrobial molecules found in fish skin mucus and its reported in vitro antimicrobial capacity against bacteria, fungi, and viruses. Additionally, the different methods of mucus extraction, which can be grouped as aqueous, organic, and acidic extractions, are presented. Finally, omic techniques (genomics, transcriptomics, proteomics, metabolomics, and multiomics) are described as key tools for the identification and isolation of new antimicrobial compounds. Overall, this study provides valuable insight into the potential of fish skin mucus as a promising source for the discovery of new antimicrobial agents.

Discovery of New Siderophores from a Marine Streptomycetes sp. via Combined Metabolomics and Analysis of Iron-Chelating Activity

The marine-derived Streptomyces sp. FIMYZ-003 strain was found to produce novel siderophores with yields negatively correlated with the iron concentration in the medium. Mass spectrometry (MS)-based metabolomics coupled with metallophore assays identified two novel α-hydroxycarboxylate-type siderophores, fradiamines C and D (3 and 4), together with two related known siderophores, fradiamines A and B (1 and 2). Their chemical structures were elucidated by nuclear magnetic resonance (NMR) and MS experiments. The annotation of a putative fra biosynthetic gene cluster enabled us to propose the biosynthetic pathway of fradiamines A-D. Furthermore, the solution-phase iron-binding activity of fradiamines was evaluated using metabolomics, confirming them as general iron scavengers. Fradiamines A-D exhibited Fe(III) binding activity equivalent to that of deferoxamine B mesylate. Growth analysis of pathogenic microbes demonstrated that fradiamine C promoted the growth of Escherichia coli and Staphylococcus aureus, but fradiamines A, B, and D did not. The results indicate that fradiamine C may serve as a novel iron carrier applicable to antibiotic delivery strategies to treat and prevent foodborne pathogens.

Isolation and Characterization of a Novel Lytic Phage, vB_PseuP-SA22, and Its Efficacy against Carbapenem-Resistant Pseudomonas aeruginosa

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) poses a serious public health threat in multiple clinical settings. In this study, we detail the isolation of a lytic bacteriophage, vB_PseuP-SA22, from wastewater using a clinical strain of CRPA. Transmission electron microscopy (TEM) analysis identified that the phage had a podovirus morphology, which agreed with the results of whole genome sequencing. BLASTn search allowed us to classify vB_PseuP-SA22 into the genus Bruynoghevirus. The genome of vB_PseuP-SA22 consisted of 45,458 bp of double-stranded DNA, with a GC content of 52.5%. Of all the open reading frames (ORFs), only 26 (44.8%) were predicted to encode certain functional proteins, whereas the remaining 32 (55.2%) ORFs were annotated as sequences coding functionally uncharacterized hypothetical proteins. The genome lacked genes coding for toxins or markers of lysogenic phages, including integrases, repressors, recombinases, or excisionases. The phage produced round, halo plaques with a diameter of 1.5 ± 2.5 mm on the bacterial lawn. The TEM revealed that vB_PseuP-SA22 has an icosahedral head of 57.5 ± 4.5 nm in length and a short, non-contractile tail (19.5 ± 1.4 nm). The phage showed a latent period of 30 min, a burst size of 300 PFU/infected cells, and a broad host range. vB_PseuP-SA22 was found to be stable between 4–60 °C for 1 h, while the viability of the virus was reduced at temperatures above 60 °C. The phage showed stability at pH levels between 5 and 11. vB_PauP-SA22 reduced the number of live bacteria in P. aeruginosa biofilm by almost five logs. The overall results indicated that the isolated phage could be a candidate to control CRPA infections. However, experimental in vivo studies are essential to ensure the safety and efficacy of vB_PauP-SA22 before its use in humans.

6-Bromoindirubin-3'-oxime derivatives are highly active colistin adjuvants against Klebsiella pneumoniae

Multidrug resistant (MDR) bacterial infections have become increasingly common, leading clinicians to rely on last-resort antibiotics such as colistin. However, the utility of colistin is becoming increasingly compromised as a result of increasing polymyxin resistance. Recently we discovered that derivatives of the eukaryotic kinase inhibitor meridianin D abrogate colistin resistance in several Gram-negative species. A subsequent screen of three commercial kinase inhibitor libraries led to the identification of several scaffolds that potentiate colistin activity, including 6-bromoindirubin-3'-oxime, which potently suppresses colistin resistance in Klebsiella pneumoniae. Herein we report the activity of a library of 6-bromoindirubin-3'-oxime analogs and identify four derivatives that show equal or increased colistin potentiation activity compared to the parent compound.

Can Gram staining be a guiding tool for optimizing initial antimicrobial agents in bacterial infections?

The emergence of multidrug-resistant organisms poses a significant threat to global public health, making the optimization of antimicrobial use crucial. Antimicrobial therapy is often initiated in emergency rooms (ERs) and intensive care units (ICUs), where patients are at high risk of infection. Prompt antimicrobial selection is essential in these facilities, and point-of-care testing can guide the appropriate initial antimicrobial therapy. Gram staining, a quick and inexpensive method, was previously used for point-of-care testing by physicians in the 1980s but was discontinued in 1988 in the United States. However, in Japan, the clinical practice of Gram stain-based antimicrobial therapy by physicians has continued in a limited number of hospitals. Several studies undertaken in Japan have shown that Gram staining carried out by trained physicians can reduce the overuse of broad-spectrum antimicrobial agents in ERs and ICUs without worsening patients' outcomes. Gram stain-based antimicrobial therapy reduced unnecessary use of carbapenems in the ER. Furthermore, Gram staining has been shown to significantly reduce the overuse of broad-spectrum antimicrobials without worsening clinical cure and mortality for patients with ventilator-associated pneumonia in the ICU. The classic technique of Gram staining has regained its usefulness through persistent clinical practice in Japan. It is hoped that Japanese researchers in this field will demonstrate to the world the efficacy of the classic technique of Gram staining in addressing this critical problem. Gram staining carried out by trained physicians could serve as a valuable means of optimizing antimicrobial treatment in ERs and ICUs.

Differentiating methicillin resistant and susceptible Staphylococcus aureus from ocular infections using photoacoustic labeling

Introduction

Antibiotic resistance in bacterial species constitutes a growing problem in the clinical management of infections. Not only does it limit therapeutic options, but application of ineffective antibiotics allows resistant species to progress prior to prescribing more effective treatment to patients. Methicillin resistance in Staphylococcus aureus is a major problem in clinical infections as it is the most common hospital acquired infection.

Methods

We developed a photoacoustic flow cytometer using engineered bacteriophage as probes for rapid determination of methicillin resistance in Staphylococcus aureus with thirteen clinical samples obtained from keratitis patients. This method irradiates cells under flow with 532 nm laser light and selectively generates acoustic waves in labeled bacterial cells, thus enabling detection and enumeration of them. Staphylococcus aureus isolates were classified from culture isolation as either methicillin resistant or susceptible using cefoxitin disk diffusion testing. The photoacoustic method enumerates bacterial cells before and after treatment with antibiotics. Decreasing counts of bacteria after treatment indicate susceptible strains. We quantified the bacterial cells in the treated and untreated samples.

Results

Using k-means clustering on the data, we achieved 100% concordance with the classification of Staphylococcus aureus resistance using culture.

Discussion

Photoacoustics can be used to differentiate methicillin resistant and susceptible strains of bacteria from ocular infections. This method may be generalized to other bacterial species using appropriate bacteriophages and testing for resistance using other antibiotics.

Evolution and Emergence of Antibiotic Resistance in Given Ecosystems: Possible Strategies for Addressing the Challenge of Antibiotic Resistance

Antibiotics were once considered the magic bullet for all human infections. However, their success was short-lived, and today, microorganisms have become resistant to almost all known antimicrobials. The most recent decade of the 20th and the beginning of the 21st century have witnessed the emergence and spread of antibiotic resistance (ABR) in different pathogenic microorganisms worldwide. Therefore, this narrative review examined the history of antibiotics and the ecological roles of antibiotics, and their resistance. The evolution of bacterial antibiotic resistance in different environments, including aquatic and terrestrial ecosystems, and modern tools used for the identification were addressed. Finally, the review addressed the ecotoxicological impact of antibiotic-resistant bacteria and public health concerns and concluded with possible strategies for addressing the ABR challenge. The information provided in this review will enhance our understanding of ABR and its implications for human, animal, and environmental health. Understanding the environmental dimension will also strengthen the need to prevent pollution as the factors influencing ABR in this setting are more than just antibiotics but involve others like heavy metals and biocides, usually not considered when studying ABR.

Identification of potential inhibitors for LLM of Staphylococcus aureus: structure-based pharmacophore modeling, molecular dynamics, and binding free energy studies

Staphylococcus aureus causes various life-threatening diseases in humans and developed resistance to several antibiotics. Lipophilic membrane (LLM) protein regulates bacterial lysis rate and methicillin resistance level in S. aureus. To identify potential lead molecules, we performed a structure-based pharmacophore modeling by consideration of pharmacophore properties from LLM-tunicamycin complex. Further, virtual screening of ZINC database against the LLM was conducted and compounds were assessed for Lipinski and ADMET properties. Based on pharmacokinetic, and molecular docking, five potential inhibitors (ZINC000072380005, ZINC000257219974, ZINC000176045471, ZINC000035296288, and ZINC000008789934) were identified. Molecular dynamics simulation (MDS) of these five molecules was performed to evaluate the dynamics and stability of protein after binding of the ligands. Several MDS analysis like RMSD, RMSF, Rg, SASA, and PCA confirm that identified compounds exhibit higher binding affinity as compared to tunicamycin for LLM. The binding free energy analysis reveals that five compounds exhibit higher binding energy in the range of -218.76 to -159.52 kJ/mol, which is higher as compared to tunicamycin (-116.13 kJ/mol). Individual residue decomposition analysis concludes that Asn148, Asp151, Asp208, His271, and His272 of LLM play a significant role in the formation of lower energy LLM-inhibitor(s) complexes. These predicted molecules displayed pharmacological and structural properties and may be further used to develop novel antimicrobial compounds against S. aureus.Communicated by Ramaswamy H. Sarma.

The Anti-MRSA Activity of Phenylthiazoles: A Comprehensive Review

Antimicrobial resistance is an aggravating global issue therefore it has been under extensive research in an attempt to reduce the number of antibiotics that are constantly reported as obsolete jeopardizing the lives of millions worldwide. Thiazoles possess a reputation as one of the most diverse biologically active nuclei, and phenylthiazoles are no less exceptional with an assorted array of biological activities such as anthelmintic, insecticidal, antimicrobial, antibacterial, and antifungal activity. Recently phenyl thiazoles came under the spotlight as a scaffold having strong potential as an anti-MRSA lead compound. It is a prominent pharmacophore in designing and synthesizing new compounds with antibacterial activity against multidrug-resistant bacteria such as MRSA, which is categorized as a serious threat pathogen, that exhibited concomitant resistance to most of the first-line antibiotics. MRSA has been associated with soft tissue and skin infections resulting in high death rates, rapid dissemination, and loss of millions of dollars of additional health care costs. In this brief review, we have focused on the advances of phenylthiazole derivatives as potential anti-MRSA from 2014 to 2021. The review encompasses the effect on biological activity due to combining this molecule with various synthetic pharmacophores. The physicochemical aspects were correlated with the pharmacokinetic properties of the reviewed compounds to reach a structure-activity relationship profile. Lead optimization of phenyl thiazole derivatives has additionally been outlined where the lipophilicity of the compounds was balanced with the metabolic stability and oral solubility to aid the researchers in medicinal chemistry, design, and synthesizing effective anti- MRSA phenylthiazoles in the future.

Antimicrobial Activity Developed by Scorpion Venoms and Its Peptide Component

Microbial infections represent a problem of great importance at the public health level, with a high rate of morbidity-mortality worldwide. However, treating the different diseases generated by microorganisms requires a gradual increase in acquired resistance when applying or using them against various antibiotic therapies. Resistance is caused by various molecular mechanisms of microorganisms, thus reducing their effectiveness. Consequently, there is a need to search for new opportunities through natural sources with antimicrobial activity. One alternative is using peptides present in different scorpion venoms, specifically from the Buthidae family. Different peptides with biological activity in microorganisms have been characterized as preventing their growth or inhibiting their replication. Therefore, they represent an alternative to be used in the design and development of new-generation antimicrobial drugs in different types of microorganisms, such as bacteria, fungi, viruses, and parasites. Essential aspects for its disclosure, as shown in this review, are the studies carried out on different types of peptides in scorpion venoms with activity against pathogenic microorganisms, highlighting their high therapeutic potential.

Effect of Ciprofloxacin, Levofloxacin, and Ofloxacin on Pseudomonas aeruginosa: A case control study with time kill curve analysis

Background

Antibiotic resistance is closely related to therapy failure. Most antibiotic resistance is caused by delays in determining antibiotic agents, low administration doses, long periods between doses (inadequate pharmacokinetics) and single drug administration in infections caused by more than one pathogen. Treatment of Pseudomonas aeruginosa (P. aeruginosa) with ciprofloxacin, levofloxacin, and ofloxacin as monotherapy can lead to drug resistance, although combination therapy also does not provide a better outcome.

Objective

To analyze the time-kill curve for P. aeruginosa and Multidrug resistance (MDR) P. aeruginosa.

Methods

This research is a case control study using isolates of P. aeruginosa ATCC 27853, clinical isolates of P. aeruginosa and MDR P. aeruginosa. Exposure of ciprofloxacin, levofloxacin, and ofloxacin to isolates with 1MIC, 2MIC, and 4MIC were then cultured at 0, 2, 4, 6, 8, 24 h of testing, then counting the number of colonies that grew and then analyzed by time-kill curve and statistical tests. The statistical test used in this study was the ANOVA and Mann-Whitney test with p < 0.05.

Results

Ciprofloxacin and ofloxacin achieved bactericidal activity, especially at a concentration of 4MIC. Levofloxacin ultimately achieved bactericidal activity at all concentrations. Statistical analysis showed there were significant differences in the number of colonies p < 0.001 in the second, fourth, sixth, and eighth hour between the three isolates, p < 0.001 in the sixth and second 4 h between 1MIC and 4MIC, p = 0.012 in the second 4 h between levofloxacin and ofloxacin antibiotics.

Conclusion

Levofloxacin has shown to have better bactericidal activity than ciprofloxacin, and ciprofloxacin has almost the same bactericidal activity as ofloxacin in vitro tests seen from the time-kill curve.

•

Antibiotics for P. aeruginosa were effective in reducing colonies at 8 h.

•

A significant comparison for antibiotics on P. aeruginosa and MDR.

•

Levofloxacin is the most effective compared to ciprofloxacin and ofloxacin for P. aeruginosa.

A Comprehensive Review of Recent Advances in the Biological Activities of Quinazolines

Quinazoline heterocycles are critical in the development of medications. Quinazoline derivatives have been intensively researched, providing a wide range of compounds with diverse biological roles. The quinazoline nucleus has garnered a lot of attention in medical chemistry in recent years. It was assumed to be a pharmacophore component in the development of physiologically interesting drugs. This review is an attempt to increase the potential of quinazoline by highlighting a wide range of advancements demonstrated by numerous derivatives of the quinazoline moiety, as well as focusing on diverse pharmacological actions of the quinazoline moiety. This review compiles recent studies on the quinazoline moiety described in the literature by researchers.

An updated review on probiotics as an alternative of antibiotics in poultry - A review

Antibiotics used to be supplemented to animal feeds as growth promoter and as an effective strategy to reduce the burden of pathogenic bacteria present in the gastro-intestinal tract. However, in-feed antibiotics also kill bacteria that may be beneficial to the animal. Secondly, unrestricted use of antibiotics enhanced the antibiotic resistance in pathogenic bacteria. To overcome above problems, scientists are taking a great deal of measures to develop alternatives of antibiotics. There is convincing evidence that probiotics could replace in-feed antibiotics in poultry production. Because they have beneficial effects on growth performance, meat quality, bone health and eggshell quality in poultry. Better immune responses, healthier intestinal microflora and morphology which help the birds to resist against disease attack were also identified with the supplementation of probiotics. Probiotics establish cross-feeding between different bacterial strains of gut ecosystem and reduce the blood cholesterol level via bile salt hydrolase activity. The action mode of probiotics was also updated according to recently published literatures, i.e antimicrobial substances generation or toxin reduction. This comprehensive review of probiotics is aimed to highlight the beneficial effects of probiotics as a potential alternative strategy to replace the antibiotics in poultry.

Current Scenario of Pathogen Detection Techniques in Agro-Food Sector

Over the past-decade, agricultural products (such as vegetables and fruits) have been reported as the major vehicles for foodborne diseases, which are limiting food resources. The spread of infectious diseases due to foodborne pathogens poses a global threat to human health and the economy. The accurate and timely detection of infectious disease and of causative pathogens is crucial in the prevention and treatment of disease. Negligence in the detection of pathogenic substances can be catastrophic and lead to a pandemic. Despite the revolution in health diagnostics, much attention has been paid to the agro-food sector regarding the detection of food contaminants (such as pathogens). The conventional analytical techniques for pathogen detection are reliable and still in operation. However, laborious procedures and time-consuming detection via these approaches emphasize the need for simple, easy-to-use, and affordable detection techniques. The rapid detection of pathogens from food is essential to avoid the morbidity and mortality originating from the suboptimal nature of empiric pathogen treatment. This review critically discusses both the conventional and emerging bio-molecular approaches for pathogen detection in agro-food.

Carbapenems consumption and Klebsiella resistance in intensive care units in Egypt: A study to evaluate the effect of an antimicrobial stewardship program

Background

The high prevalence of carbapenem-resistant Klebsiella imposes optimizing antibiotic consumption. We aimed to evaluate the impact of antibiotic stewardship program on carbapenem consumption and the Klebsiella resistance.

Method

We retrospectively evaluated critically ill patients with isolated Klebsiella species from Elaraby hospital, Egypt during the period from April 2017 to January 2019. We collected data related to carbapenems consumption and Klebsiella clinical isolates with their antimicrobial susceptibility. Based on susceptibility, Klebsiella isolates were classified into sensitive, extended spectrum beta-lactamase (ESBL) producer, and carbapenem-resistant Klebsiella (CRK), respectively. Our primary outcome was the change in carbapenems consumption after implementing the program, while the secondary outcomes were the changes in the incidence of CRK.

Results

The study included 205 patients with isolated Klebsiella species during the study period. The antibiotic stewardship program started in March 2018. Out of the 205 patients, 61 patients (29.8%) represented the pre-intervention sample, and 144 patients (70.2%) represented the post-intervention sample. Applying the antibiotic stewardship program was associated with a significant decrease in the carbapenems consumption from 38.9 to 26.6 defined daily dose/1000 patient-days (p = 0.02). The incidence of CRK was decreased from 85.25% of total Klebsiella isolates to 48.6% (p < 0.001). Klebsiella species were more likely to be in a lower category of resistance after applying the program with an odds ratio of 6.3 (2.88-13.73) using ordinal logistic regression.

Conclusion

Applying the antibiotic stewardship program could reduce the unnecessary carbapenems use in the ICU with a subsequent decrease in the emergence of the Klebsiella-resistant strains.

The Immune System of Marine Organisms as Source for Drugs against Infectious Diseases

The high proliferation of microorganisms in aquatic environments has allowed their coevolution for billions of years with other living beings that also inhabit these niches. Among the different existing types of interaction, the eternal competition for supremacy between the susceptible species and their pathogens has selected, as part of the effector division of the immune system of the former ones, a vast and varied arsenal of efficient antimicrobial molecules, which is highly amplified by the broad biodiversity radiated, above any others, at the marine habitats. At present, the great recent scientific and technological advances already allow the massive discovery and exploitation of these defense compounds for therapeutic purposes against infectious diseases of our interest. Among them, antimicrobial peptides and antimicrobial metabolites stand out because of the wide dimensions of their structural diversities, mechanisms of action, and target pathogen ranges. This revision work contextualizes the research in this field and serves as a presentation and scope identification of the Special Issue from Marine Drugs journal “The Immune System of Marine Organisms as Source for Drugs against Infectious Diseases”.

Scaffold size-dependent effect on the enhanced uptake of antibiotics and other compounds by Escherichia coli and Pseudomonas aeruginosa

The outer membrane of Gram-negative bacteria functions as an impermeable barrier to foreign compounds. Thus, modulating membrane transport can contribute to improving susceptibility to antibiotics and efficiency of bioproduction reactions. In this study, the cellular uptake of hydrophobic and large-scaffold antibiotics and other compounds in Gram-negative bacteria was investigated by modulating the homolog expression of bamB encoding an outer membrane lipoprotein and tolC encoding an outer membrane efflux protein via gene deletion and gene silencing. The potential of deletion mutants for biotechnological applications, such as drug screening and bioproduction, was also demonstrated. Instead of being subjected to gene deletion, wild-type bacterial cells were treated with cell-penetrating peptide conjugates of a peptide nucleic acid (CPP-PNA) against bamB and tolC homologs as antisense agents. Results revealed that the single deletion of bamB and tolC in Escherichia coli increased the uptake of large- and small-scaffold hydrophobic compounds, respectively. A bamB-and-tolC double deletion mutant had a higher uptake efficiency for certain antibiotics and other compounds with high hydrophobicity than each single deletion mutant. The CPP-PNA treated E. coli and Pseudomonas aeruginosa cells showed high sensitivity to various antibiotics. Therefore, these gene deletion and silencing approaches can be utilized in therapeutic and biotechnological fields.

Tandem construction of biological relevant aliphatic 5-membered N-heterocycles

Nature often uses cascade reactions in a highly stereocontrolled manner for assembly structurally diverse nitrogen-containing heterocyclic scaffolds, i.e. secondary metabolites, important for medicinal chemistry and pharmacy. Five-membered nitrogen-containing heterocycles as standalone rings, as well as spiro and polycyclic systems are pharmacophores of drugs approved in various therapies, i.a. antibacterial or antiviral, antifungal, anticancer, antidiabetic, as they target many key enzymes. Furthermore, a large number of pyrrolidine derivatives are currently considered as drug candidates. Cascade transformations, also known as domino or tandem reactions, offer straightforward methods to build N-heterocyclic libraries of the great structural variety desired for drawing SAR conclusions. The tandem transformations are often atom economic and time-saving because they are performed as the one-pot, so no need for purification after each 'virtual' step and the limited necessity of protective groups are characteristic for these processes. Thus, the same results as in classical multistep synthesis can be achieved at markedly lower costs and shorter time, which is in line with modern green chemistry rules. Great advantage of cascade reactions is often reflected in their high regio- and stereoselectivities, enabling the preparing of the heterocyclic compound better fitted to the expected target in cells. This review reveals the biological relevance of N-heterocyclic scaffolds based on saturated 5-membered rings since we showed a number of examples of approved drugs together with the recent biologically attractive leading structures of drug candidates. Next, novel cascade synthetic procedures, taking into account the structure of the reactants and reaction mechanisms, enabling to obtain biological-relevant heterocyclic frameworks with good yields and relatively high stereoselectivity, were reviewed and compared. The review covers the advances of designing biological active N-heterocycles mainly from 2018 to 2021, whereas the synthetic part is focused on the last 7 years.

Molecular Mechanisms Associated with the Resistance of Rhizoctonia solani AG-4 Isolates to the Succinate Dehydrogenase Inhibitor Thifluzamide

Thifluzamide, a succinate dehydrogenase (SDH) inhibitor, possesses high activity against Rhizoctonia. In this study, 144 Rhizoctonia solani AG-4 (4HGI, 4HGII, and 4HGIII) isolates, the predominate pathogen associated with sugar beet seedling damping-off, were demonstrated to be sensitive to thifluzamide with a calculated mean median effective concentration of 0.0682 ± 0.0025 μg/ml. Thifluzamide-resistant isolates were generated using fungicide-amended media, resulting in four AG-4HGI isolates and eight AG-4HGII isolates with stable resistance and almost no loss in fitness. Evaluation of cross-resistance of the 12 thifluzamide-resistant isolates and their corresponding parental-sensitive isolates revealed a moderately positive correlation between thifluzamide resistance and the level of resistance to eight other fungicides from three groups, the exception being fludioxonil. An active efflux of fungicide through ATP-binding cassette and major facilitator superfamily transporters was found to be correlated to the resistance of R. solani AG-4HGII isolates to thifluzamide based on RNA-sequencing and quantitative reverse transcription-PCR analyses. Sequence analysis of sdhA, sdhB, sdhC, and sdhD revealed replacement of isoleucine by phenylalanine at position 61 in SDHC in 9 of the 12 generated thifluzamide-resistant isolates. No other mutations were found in any of the other genes. Collectively, the data indicate that the active efflux of fungicide and a point mutation in sdhC may contribute to the resistance of R. solani AG-4HGI and AG-4HGII isolates to thifluzamide in vitro. This is the first characterization of the potential molecular mechanism associated with the resistance of R. solani AG-4 isolates to thifluzamide and provides practical guidance for the use of this fungicide.

Anti-cancer and antimicrobial potential of five soil Streptomycetes: a metabolomics-based study

Lack of new anti-cancer and anti-infective agents directed the pharmaceutical research to natural products' discovery especially from actinomycetes as one of the major sources of bioactive compounds. Metabolomics- and dereplication-guided approach has been used successfully in chemical profiling of bioactive actinomycetes. We aimed to study the metabolomic profile of five bioactive actinomycetes to investigate the interesting metabolites responsible for their antimicrobial and anti-cancer activities. Three actinomycetes, namely, Streptomyces sp. SH8, SH10 and SH13, were found to exhibit broad spectrum of antimicrobial activities, whereas isolate SH4 showed the broadest antimicrobial activity against all tested strains. In addition, isolates SH8, SH10 and SH12 displayed potent cytotoxicity against the breast cancer cell line Michigan Cancer Foundation-7 (MCF-7), whereas isolates SH4 and SH12 exhibited potent anti-cancer activity against the hepatoma cell line hepatoma G2 (HepG2) compared with their weak inhibitory properties on the normal breast cells MCF-10A and normal liver cells transformed human liver epithelial-2 (THLE2), respectively. All bioactive isolates were molecularly identified as Streptomyces sp. via 16S rRNA gene sequencing. Our actinobacterial dereplication analysis revealed putative identification of several bioactive metabolites including tetracycline, oxytetracycline and a macrolide antibiotic, novamethymycin. Together, chemical profiling of bioactive Streptomycetes via dereplication and metabolomics helped in assigning their unique metabolites and predicting the bioactive compounds instigating their diverse bioactivities.

Inherent and Composite Hydrogels as Promising Materials to Limit Antimicrobial Resistance

Antibiotic resistance has increased significantly in the recent years, and has become a global problem for human health and the environment. As a result, several technologies for the controlling of health-care associated infections have been developed over the years. Thus, the most recent findings in hydrogel fabrication, particularly antimicrobial hydrogels, could offer valuable solutions for these biomedical challenges. In this review, we discuss the most promising strategies in the development of antimicrobial hydrogels and the application of hydrogels in the treatment of microbial infections. The latest advances in the development of inherently and composite antimicrobial hydrogels will be discussed, as well as hydrogels as carriers of antimicrobials, with a focus on antibiotics, metal nanoparticles, antimicrobial peptides, and biological extracts. The emergence of CRISR-Cas9 technology for removing the antimicrobial resistance has led the necessity of new and performant carriers for delivery of the CRISPR-Cas9 system. Different delivery systems, such as composite hydrogels and many types of nanoparticles, attracted a great deal of attention and will be also discussed in this review.

Molecular rationale for the impairment of the MexAB-OprM efflux pump by a single mutation in MexA

Efflux pumps of the Resistance-Nodulation-cell Division (RND) superfamily contribute to intrinsic and acquired resistance in Gram-negative pathogens by expelling chemically unrelated antibiotics with high efficiency. They are tripartite systems constituted by an inner-membrane-anchored transporter, an outer membrane factor protein, and a membrane fusion protein. Multimerization of the membrane fusion protein is an essential prerequisite for full functionality of these efflux pumps. In this work, we employed complementary computational techniques to investigate the stability of a dimeric unit of MexA (the membrane fusion protein of the MexAB-OprM RND efflux pump of Pseudomonas aeruginosa), and to provide a molecular rationale for the effect of the G72S substitution, which affects MexAB-OprM functionality by impairing the assembly of MexA. Our findings indicate that: i) dimers of this protein are stable in multiple µs-long molecular dynamics simulations; ii) the mutation drastically alters the conformational equilibrium of MexA, favouring a collapsed conformation that is unlikely to form dimers or higher order assemblies. Unveiling the mechanistic aspects underlying large conformational distortions induced by minor sequence changes is informative to efforts at interfering with the activity of this elusive bacterial weapon. In this respect, our work further confirms how molecular simulations can give important contribution and useful insights to characterize the mechanism of highly complex biological systems.

Antibacterial Activity of Pharmaceutical-Grade Rose Bengal: An Application of a Synthetic Dye in Antibacterial Therapies

Rose bengal has been used in the diagnosis of ophthalmic disorders and liver function, and has been studied for the treatment of solid tumor cancers. To date, the antibacterial activity of rose bengal has been sporadically reported; however, these data have been generated with a commercial grade of rose bengal, which contains major uncontrolled impurities generated by the manufacturing process (80-95% dye content). A high-purity form of rose bengal formulation (HP-RBf, >99.5% dye content) kills a battery of Gram-positive bacteria, including drug-resistant strains at low concentrations (0.01-3.13 μg/mL) under fluorescent, LED, and natural light in a few minutes. Significantly, HP-RBf effectively eradicates Gram-positive bacterial biofilms. The frequency that Gram-positive bacteria spontaneously developed resistance to HP-RB is extremely low (less than 1 × 10-13). Toxicity data obtained through our research programs indicate that HP-RB is feasible as an anti-infective drug for the treatment of skin and soft tissue infections (SSTIs) involving multidrug-resistant (MDR) microbial invasion of the skin, and for eradicating biofilms. This article summarizes the antibacterial activity of pharmaceutical-grade rose bengal, HP-RB, against Gram-positive bacteria, its cytotoxicity against skin cells under illumination conditions, and mechanistic insights into rose bengal's bactericidal activity under dark conditions.

Efficacy and safety of delafloxacin, ceftaroline, ceftobiprole, and tigecycline for the empiric treatment of acute bacterial skin and skin structure infections: A network meta-analysis of randomized controlled trials

Background

Method

Results

Conclusion

Prediction of Potential Drug Targets and Vaccine Candidates Against Antibiotic-Resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is one of the leading causes of nosocomial infections, characterized by increasing antibiotic resistance, severity and mortality. Therefore, numerous efforts have been made nowadays to identify new therapeutic targets. This study aimed to find potential drug targets and vaccine candidates in drug-resistant strains of P. aeruginosa. Extensive antibiotic-resistant and carbapenem-resistant strains of P. aeruginosa with complete genome were selected and ten common hypothetical proteins (HPs) containing more than 200 amino acids were obtained. The structural, functional and immunological predictions of these HPs were performed with the utility of bioinformatics approaches. Two common HPs (Gene ID: 2877781645 and 2877781936) among other investigated proteins were revealed as potential candidates for pharmaceutical and vaccine purposes based on structural and physicochemical properties, functional domains, subcellular localizations, signal peptides, toxicity, virulence factor, antigenicity, allergenicity and immunoinformatic predictions. The consequence of this predictive study will assist in novel drug and vaccine design through experimental investigations.

Benzimidazole Isosteres of Salicylanilides Are Highly Active Colistin Adjuvants

Multidrug-resistant bacterial infections have become a global threat. We recently disclosed that the known IKK-β inhibitor IMD-0354 and subsequent analogues abrogate colistin resistance in several Gram-negative strains. Herein, we report the activity of a second-generation library of IMD-0354 analogues incorporating a benzimidazole moiety as an amide isostere. We identified several analogues that show increased colistin potentiation activity against Gram-negative bacteria.

Polymyxin B-Triggered Assembly of Peptide Hydrogels for Localized and Sustained Release of Combined Antimicrobial Therapy

Repurposing old antibiotics into more effective and safer formulations is an emergent approach to tackle the growing threat of antimicrobial resistance. Herein, a peptide hydrogel is reported for the localized and sustained release of polymyxin B (PMB), a decade-old antibiotic with increasing clinical utility for treating multidrug-resistant Gram-negative bacterial infections. The hydrogel is assembled by additing PMB solution into a rationally designed peptide amphiphile (PA) solution and its mechanical properties can be adjusted through the addition of counterions, envisioning its application in diverse infection scenarios. Sustained release of PMB from the hydrogel over a 5-day period and prolonged antimicrobial activities against Gram-negative bacteria are observed. The localized release of active PMB from the hydrogel is shown to be effective in vivo for treating Pseudomonas aeruginosa infection in the Galleria mellonella burn wound infection model, dramatically reducing the mortality from 93% to 13%. Complementary antimicrobial activity against Gram-positive Staphylococcus aureus and enhanced antimicrobial effect against the Gram-negative Acinetobacter baumannii are observed when an additional antibiotic fusidic acid is incorporated into the hydrogen network. These results demonstrate the potential of the PMB-triggered PA hydrogel as a versatile platform for the localized and sustained delivery of combined antimicrobial therapies.

Novel 2,4-disubstituted quinazoline analogs as antibacterial agents with improved cytotoxicity profile: Optimization of the 2,4-substituents

The emergence of bacterial resistance has triggered a multitude of efforts to develop new antibacterial agents. There are many compounds in literature that were reported as potent antibacterial agents, however, they lacked the required safety to mammalian cells or no clear picture about their toxicity profile was presented. Inspired by discovered hit from our in-house library and by previously reported 2,4-diaminosubstituted quinazolines, we describe the design and synthesis of novel 2,4-disubstituted-thioquinazolines (3-13 and 36), 2-thio-4-amino substituted quinazolines (14-33) and 6-substituted 2,4-diamonsubstituted quinazolines (37-39). The synthesized compounds showed potent antibacterial activity against a panel of Gram-positive, efflux deficient E.coli and Mycobacterium smegmatis. The panel also involved resistant strains including methicillin-resistant Staphylococcus aureus, penicillin-resistant Streptococcus pneumoniae, vancomycin-resistant Enterococcus faecalis and vancomycin-resistant Enterococcus faecium, in addition to Mycobacterium smegmatis. The newly synthesized compounds revealed MIC values against the tested strains ranging from 1 to 64 µg/mL with a good safety profile. Most of the 2-thio-4-amino substituted-quinazolines showed significant antimycobacterial activity with the variations at position 2 and 4 offering additional antibacterial activity against the different strains. Compared to previously reported 2,4-diaminosubstituted quinazolines, the bioisosteric replacement of the 2-amino with sulfur offered a successful approach to keep the high antibacterial potency while substantially improving safety profile as indicated by the reduced activity on different cell lines and a lack of hemolytic activity.

Mechanism of Antimicrobial Peptides: Antimicrobial, Anti-Inflammatory and Antibiofilm Activities

Antimicrobial peptides (AMPs) are regarded as a new generation of antibiotics. Besides antimicrobial activity, AMPs also have antibiofilm, immune-regulatory, and other activities. Exploring the mechanism of action of AMPs may help in the modification and development of AMPs. Many studies were conducted on the mechanism of AMPs. The present review mainly summarizes the research status on the antimicrobial, anti-inflammatory, and antibiofilm properties of AMPs. This study not only describes the mechanism of cell wall action and membrane-targeting action but also includes the transmembrane mechanism of intracellular action and intracellular action targets. It also discusses the dual mechanism of action reported by a large number of investigations. Antibiofilm and anti-inflammatory mechanisms were described based on the formation of biofilms and inflammation. This study aims to provide a comprehensive review of the multiple activities and coordination of AMPs in vivo, and to fully understand AMPs to realize their therapeutic prospect.

Synergistic Activity of Capsaicin and Colistin Against Colistin-Resistant Acinetobacter baumannii: In Vitro/Vivo Efficacy and Mode of Action

Acinetobacter baumannii is an opportunistic pathogen predominantly associated with nosocomial infections. With emerging resistance against polymyxins, synergistic combinations of drugs are being investigated as a new therapeutic approach. Capsaicin is a common constituent of the human diet and is widely used in traditional alternative medicines. The present study evaluated the antibacterial activities of capsaicin in combination with colistin against three unrelated colistin-resistant Acinetobacter baumannii strains in vitro and in vivo, and then further studied their synergistic mechanisms. Using the checkerboard technique and time-kill assays, capsaicin and colistin showed a synergistic effect on colistin-resistant A. baumannii. A mouse bacteremia model confirmed the in vivo effects of capsaicin and colistin. Mechanistic studies shown that capsaicin can inhibit the biofilm formation of both colistin-resistant and non-resistant A. baumannii. In addition, capsaicin decreased the production of intracellular ATP and disrupted the outer membrane of A. baumannii. In summary, the synergy between these drugs may enable a lower concentration of colistin to be used to treat A. baumannii infection, thereby reducing the dose-dependent side effects. Hence, capsaicin–colistin combination therapy may offer a new treatment option for the control of A. baumannii infection.

Visible-Light-Driven Photocatalysis-Enhanced Nanozyme of TiO2 Nanotubes@MoS2 Nanoflowers for Efficient Wound Healing Infected with Multidrug-Resistant Bacteria

To enhance the catalytic activity of the nanozymes for efficient wound healing infected with multidrug-resistant bacteria, photo-based motivations have been suggested, but attention is mainly focused on the external stimulus of near-infrared light, while the inexhaustible visible one is promising but lack of study. Herein, an efficient visible light-stimulated peroxidase-like nanozyme system, TiO₂ nanotubes coated with MoS₂ nanoflowers (TiO₂ NTs@MoS₂ ), is discovered for efficient bacterial treatment. Based on the synergetic effects between the two components, the bandgap of the TiO₂ NTs can be narrowed from 3.2 to 2.97 eV due to the MoS₂ loading, which extended the light response of TiO₂ to visible-light range and enhanced the photocatalytic activity accordingly. Meanwhile, the peroxidase-like activity of MoS₂ can be significantly enhanced due to the combination with TiO₂ NTs in return. Especially, the peroxidase-like activity of the TiO₂ NTs@MoS₂ nanocomposite can be further improved under the sunlight irradiation, rendering much more hydroxyl radical (•OH) generation. Accordingly, the as-obtained TiO₂ NTs@MoS₂ shows an outstanding antibacterial effect against drug-resistance extended spectrum β-lactamases producing Escherichia coli and methicillin-resistant Staphylococcus aureus under the visible light. In vivo wound healing test further confirms the high antimicrobial efficiency and good biocompatibility of the synergistic antimicrobial system.

Occurrence, Antibiotic Resistance, Virulence Factors, and Genetic Diversity of Bacillus spp. from Public Hospital Environments in South Africa

This study aimed to assess the molecular dissemination of Bacillus species in public hospitals in South Africa. The study conducted over 3 months during 2017 involved representative samples obtained from three wards (general ward, intensive care unit, and pediatric unit) from four public hospitals denoted as A (Central), B (Tertiary), C (Regional), and D (District). Swabs collected from 11 distinct hospital surfaces were screened using selective media, biochemical testing, and molecular methods. Overall, 17% (135/777) isolates were identified with a prevalence of 24% (32/135) for central, 33% (45/135) for tertiary, 27% (36/135) for regional, and 16% (22/135) for district hospital. Bacillus species were further confirmed to belong to Bacillus cereus (129/135; 96%) and Bacillus subtilis (6/135; 4%). Prevalence was similar across the wards, averaging 33.3% (45/135). The highest prevalence of Bacillus isolates was found on the drip stands (11.8%), sink (11.8%), ward phone (11.5%), and nurses' tables (10.3%). Minimum inhibitory concentration analyses revealed high resistance to β-lactams, fluoroquinolones, and tetracyclines. The most common resistance genes detected were ermB (56%) and tetM (5%). Enterotoxin virulence genes hblA (77%) and hblD (88%) associated with the diarrheal syndrome were most detected; however, no ces genes (cereulide toxin) for emetic syndrome was found. The enterobacterial repetitive intergenic consensus PCR revealed considerable diversity at the different levels of health care, although the clonal spread of strains between the sites/wards within each specific hospital was revealed. The study highlighted the dissemination of drug-resistant Bacillus spp. in public hospital environments and calls for the design of optimal strategies to curb their spread.

Longitudinal study on the effects of growth-promoting and therapeutic antibiotics on the dynamics of chicken cloacal and litter microbiomes and resistomes

BACKGROUND

Therapeutic and growth-promoting antibiotics are frequently used in broiler production. Indirect evidence indicates that these practices are linked to the proliferation of antimicrobial resistance (AMR), the spread of antibiotic-resistant bacteria from food animals to humans, and the environment, but there is a lack of comprehensive experimental data supporting this. We investigated the effects of growth promotor (bacitracin) and therapeutic (enrofloxacin) antibiotic administration on AMR in broilers for the duration of a production cycle, using a holistic approach that integrated both culture-dependent and culture-independent methods. We specifically focused on pathogen-harboring families (Enterobacteriaceae, Enterococcaceae, and Staphylococcaceae).

RESULTS

Antibiotic-resistant bacteria and antibiotic resistance genes were ubiquitous in chicken cloaca and litter regardless of antibiotic administration. Environment (cloaca vs. litter) and growth stage were the primary drivers of variation in the microbiomes and resistomes, with increased bacterial diversity and a general decrease in abundance of the pathogen-harboring families with age. Bacitracin-fed groups had higher levels of bacitracin resistance genes and of vancomycin-resistant Enterococcaceae (total Enterococcaceae counts were not higher). Although metagenomic analyses classified 28-76% of the Enterococcaceae as the commensal human pathogens E. faecalis and E. faecium, culture-based analysis suggested that approximately 98% of the vancomycin-resistant Enterococcaceae were avian and not human-associated, suggesting differences in the taxonomic profiles of the resistant and non-resistant strains. Enrofloxacin treatments had varying effects, but generally facilitated increased relative abundance of multidrug-resistant Enterobacteriaceae strains, which were primarily E. coli. Metagenomic approaches revealed a diverse array of Staphylococcus spp., but the opportunistic pathogen S. aureus and methicillin resistance genes were not detected in culture-based or metagenomic analyses. Camphylobacteriaceae were significantly more abundant in the cloacal samples, especially in enrofloxacin-treated chickens, where a metagenome-assembled C. jejuni genome harboring fluoroquinolone and β-lactam resistance genes was identified.

CONCLUSIONS

Within a "farm-to-fork, one health" perspective, considering the evidence that bacitracin and enrofloxacin used in poultry production can select for resistance, we recommend their use be regulated. Furthermore, we suggest routine surveillance of ESBL E. coli, vancomycin-resistant E. faecalis and E. faecium, and fluoroquinolone-resistant C. jejuni strains considering their pathogenic nature and capacity to disseminate AMR to the environment. Video Abstract.

Potential role of new-generation antibiotics in acute bacterial skin and skin structure infections

PURPOSE OF REVIEW

To summarize the available results of primary analyses from high-quality randomized studies of either recently approved or possible future agents for the treatment of acute bacterial skin and skin structure infections (ABSSSI).

RECENT FINDINGS

In the last 2 decades, several novel agents have been approved for the treatment of ABSSSI, that are also active against methicillin-resistant Staphylococcus aureus (MRSA). In addition to already available agents, further molecules are in clinical development that could become available for treating ABSSSI in the forthcoming future.

SUMMARY

The current and future availability of several new-generation antibiotics will allow to modulate therapeutic choices not only on efficacy but also on other relevant factors such as the combination of the drug safety profile and the comorbidities of any given patient, the expected adherence to outpatient therapy, and the possibilities of early discharge or avoiding hospitalization by means of oral formulations, early switch from intravenous to oral therapy, or single-dose administration of long-acting intravenous agents. With the advent of new-generation antibiotics, all these factors are becoming increasingly essential for tailoring treatment to individual patients in line with the principles of personalized medicine, and for optimizing the use of healthcare resources.