Critical analysis of antibacterial agents in clinical development

Hospital and municipal wastewater as a source of carbapenem-resistant Acinetobacter baumannii and Pseudomonas aeruginosa in the environment: a review

The increase in the prevalence of carbapenem-resistant Gram-negative bacteria, in particular Acinetobacter baumannii (CRAB) and Pseudomonas aeruginosa (CRPA), poses a serious threat for public health worldwide. This article reviews the alarming data on the prevalence of infections caused by CRAB and CRPA pathogens and their presence in hospital and municipal wastewater, and it highlights the environmental impact of antibiotic resistance. The article describes the key role of antibiotic resistance genes (ARGs) in the acquisition of carbapenem resistance and sheds light on bacterial resistance mechanisms. The main emphasis was placed on the transfer of ARGs not only in the clinical setting, but also in the environment, including water, soil, and food. The aim of this review was to expand our understanding of the global health risks associated with CRAB and CRPA in hospital and municipal wastewater and to analyze the spread of these micropollutants in the environment. A review of the literature published in the last decade will direct research on carbapenem-resistant pathogens, support the implementation of effective preventive measures and interventions, and contribute to the development of improved strategies for managing this problem.

The Guardian of Vision: Intelligent Bacteriophage-Based Eyedrops for Clinical Multidrug-Resistant Ocular Surface Infections

Clinical multidrug-resistant Pseudomonas aeruginosa (MDR-PA) is the leading cause of refractory bacterial keratitis (BK). However, the reported BK treatment methods lack biosecurity and bioavailability, which usually causes irreversible visual impairment and even blindness. Herein, for BK caused by clinically isolated MDR-PA infection, armed phages are modularized with the type I photosensitizer (PS) ACR-DMT, and an intelligent phage eyedrop is developed for combined phagotherapy and photodynamic therapy (PDT). These eyedrops maximize the advantages of bacteriophages and ACR-DMT, enabling more robust and specific targeting killing of MDR-PA under low oxygen-dependence, penetrating and disrupting biofilms, and efficiently preventing biofilm reformation. Altering the biofilm and immune microenvironments alleviates inflammation noninvasively, promotes corneal healing without scar formation, protects ocular tissues, restores visual function, and prevents long-term discomfort and pain. This strategy exhibits strong scalability, enables at-home treatment of ocular surface infections with great patient compliance and a favorable prognosis, and has significant potential for clinical application.

Comparison of available methods to evaluate cefiderocol susceptibility in Acinetobacter spp

Recently, considerable uncertainty has arisen concerning the appropriate susceptibility testing for cefiderocol in gram-negative bacilli, particularly in the context of its application to Acinetobacter spp. The optimal method for assessing the susceptibility levels of Acinetobacter spp. to cefiderocol remains a subject of debate due to substantial disparities observed in the values obtained through various testing procedures. This study employed four minimum inhibitory concentration (MIC) methodologies and the disk diffusion to assess the susceptibility of twenty-seven carbapenem resistant (CR)-Acinetobacter strains to cefiderocol. The results from our study reveal significant variations in the minimum inhibitory concentration (MIC) values obtained with the different methods and in the level of agreement in interpretation categories between the different MIC methods and the disk diffusion test. Among the MIC methods, there was relatively more consistency in reporting the interpretation categories. For European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints, the categorical agreement (CA) for MIC methods ranged between 66.7 and 81.5%. On the other hand, the essential agreement (EA) values were as low as 18.5-29.6%. The CA between MIC methods and disk diffusion was 81.5%. These results emphasize the need for a reliable, accurate, and clinically validated methodology to effectively assess the susceptibility of Acinetobacter spp. to cefiderocol. The wide variability observed in our study highlights the importance of standardizing the susceptibility testing process for cefiderocol to ensure consistent and reliable results for clinical decision-making.

Sunlight-Driven Photothermally Boosted Photocatalytic Eradication of Superbugs Using a Plasmonic Gold Nanoparticle-Decorated WO3 Nanowire-Based Heterojunction

Superbug infections are currently one of the biggest global health problems in our society. Herein, we report the design of a plasmonic gold nanoparticle (GNP)-decorated WO3 nanowire-based heterojunction for the proficient usage of sunlight-based renewable energy to inactivate 100% superbugs via photothermally boosted photocatalytic action. Additionally, a synergistic photothermal and photocatalytic approach has been used for sunlight-driven complete eradication of carbapenem-resistant Enterobacteriaceae Escherichia coli (CRE E. coli) and methicillin-resistant Staphylococcus aureus (MRSA) superbugs. Interestingly, photocatalytic activity of methylene blue (MB) dye degradation in the presence of 670 nm near-infrared light shows that photothermally boosted photocatalytic performance is much superior to that of only a photocatalytic or photothermal process. The observed higher photocatalytic performance for the heterojunction is because the plasmonic GNP enhanced the absorption capability at 670 nm and increased the temperature of the photocatalyst surface, which reduces the activation energy of the degradation reaction. Similarly, sunlight-driven photocatalytic experiments show 100% degradation of MB after 60 min of sunlight irradiation. Moreover, sunlight-based photocatalytic inactivation of MRSA and CRE E. coli experiments show 100% inactivation after 60 min of light irradiation.

Antibiotic Alternatives: Multifunctional Ultra-Small Metal Nanoclusters for Bacterial Infectious Therapy Application

The prevalence of major bacterial infections has emerged as a significant menace to human health and life. Conventional treatment methods primarily rely on antibiotic therapy, but the overuse of these drugs has led to a decline in their efficacy. Moreover, bacteria have developed resistance towards antibiotics, giving rise to the emergence of superbugs. Consequently, there is an urgent need for novel antibacterial agents or alternative strategies to combat bacterial infections. Nanoantibiotics encompass a class of nano-antibacterial materials that possess inherent antimicrobial activity or can serve as carriers to enhance drug delivery efficiency and safety. In recent years, metal nanoclusters (M NCs) have gained prominence in the field of nanoantibiotics due to their ultra-small size (less than 3 nm) and distinctive electronic and optical properties, as well as their biosafety features. In this review, we discuss the recent progress of M NCs as a new generation of antibacterial agents. First, the main synthesis methods and characteristics of M NCs are presented. Then, we focus on reviewing various strategies for detecting and treating pathogenic bacterial infections using M NCs, summarizing the antibacterial effects of these nanoantibiotics on wound infections, biofilms, and oral infections. Finally, we propose a perspective on the remaining challenges and future developments of M NCs for bacterial infectious therapy.

Lacticaseibacillus rhamnosus CRL 2244 secreted metabolites display killing and antibiotic synergistic activity against multi-drug resistant pathogens

A growing increase in the number of serious infections caused by multidrug resistant bacteria (MDR) is challenging our society. Despite efforts to discover novel therapeutic options, few antibiotics targeting MDR have been approved by the Food and Drug Administration (FDA). Lactic acid bacteria have emerged as a promising therapeutic alternative due to their demonstrated ability to combat MDR pathogens in vitro. Our previous co-culture studies showed Lacticaseibacillus rhamnosus CRL 2244 as having a potent killing effect against carbapenem-resistant Acinetobacter baumannii (CRAB) strains. Here we report that cell-free conditioned media (CFCM) samples obtained from Lcb. rhamnosus CRL 2244 cultures incubated at different times display antimicrobial activity against 43 different pathogens, including CRAB, methicillin-resistant Staphylococcus aureus (MRSA) and carbapenemase Klebsiella pneumoniae (KPC)-positive strains. Furthermore, transwell and ultrafiltration analyses together with physical and chemical/biochemical tests showed that Lcb. rhamnosus CRL 2244 secretes a <3 kDa metabolite(s) whose antimicrobial activity is not significantly impaired by mild changes in pH, temperature and various enzymatic treatments. Furthermore, sensitivity and time-kill assays showed that the bactericidal activity of the Lcb. rhamnosus CRL 2244 metabolite(s) enhances the activity of some current FDA approved antibiotics. We hypothesize that this observation could be due to the effects of Lcb. rhamnosus CRL 2244 metabolite(s) on cell morphology and the enhanced transcriptional expression of genes coding for the phenylacetate (PAA) and histidine catabolic Hut pathways, metal acquisition and biofilm formation, all of which are associated with bacterial virulence. Interestingly, the extracellular presence of Lcb. rhamnosus CRL 2244 induced the transcription of the gene coding for the CidA/LgrA protein, which is involved in programmed cell death in some bacteria. Overall, the findings presented in this report underscore the promising potential of the compound(s) released by Lcb. rhamnosus CRL2244 as an alternative and/or complementary option to treat infections caused by A. baumannii as well as other MDR bacterial pathogens.

Antibiotic discovery with artificial intelligence for the treatment of Acinetobacter baumannii infections

Global challenges presented by multidrug-resistant Acinetobacter baumannii infections have stimulated the development of new treatment strategies. We reported that outer membrane protein W (OmpW) is a potential therapeutic target in A. baumannii. Here, a library of 11,648 natural compounds was subjected to a primary screening using quantitative structure-activity relationship (QSAR) models generated from a ChEMBL data set with >7,000 compounds with their reported minimal inhibitory concentration (MIC) values against A. baumannii followed by a structure-based virtual screening against OmpW. In silico pharmacokinetic evaluation was conducted to assess the drug-likeness of these compounds. The ten highest-ranking compounds were found to bind with an energy score ranging from -7.8 to -7.0 kcal/mol where most of them belonged to curcuminoids. To validate these findings, one lead compound exhibiting promising binding stability as well as favorable pharmacokinetics properties, namely demethoxycurcumin, was tested against a panel of A. baumannii strains to determine its antibacterial activity using microdilution and time-kill curve assays. To validate whether the compound binds to the selected target, an OmpW-deficient mutant was studied and compared with the wild type. Our results demonstrate that demethoxycurcumin in monotherapy and in combination with colistin is active against all A. baumannii strains. Finally, the compound was found to significantly reduce the A. baumannii interaction with host cells, suggesting its anti-virulence properties. Collectively, this study demonstrates machine learning as a promising strategy for the discovery of curcuminoids as antimicrobial agents for combating A. baumannii infections.

IMPORTANCE

Acinetobacter baumannii presents a severe global health threat, with alarming levels of antimicrobial resistance rates resulting in significant morbidity and mortality in the USA, ranging from 26% to 68%, as reported by the Centers for Disease Control and Prevention (CDC). To address this threat, novel strategies beyond traditional antibiotics are imperative. Computational approaches, such as QSAR models leverage molecular structures to predict biological effects, expediting drug discovery. We identified OmpW as a potential therapeutic target in A. baumannii and screened 11,648 natural compounds. We employed QSAR models from a ChEMBL bioactivity data set and conducted structure-based virtual screening against OmpW. Demethoxycurcumin, a lead compound, exhibited promising antibacterial activity against A. baumannii, including multidrug-resistant strains. Additionally, demethoxycurcumin demonstrated anti-virulence properties by reducing A. baumannii interaction with host cells. The findings highlight the potential of artificial intelligence in discovering curcuminoids as effective antimicrobial agents against A. baumannii infections, offering a promising strategy to address antibiotic resistance.

Refining and in-situ growth of polyaniline endows the cellulose fibers with electrical stimulation sterilization

Bacteria and virus infections have posed a great threat to public health and personnel safety. For realizing rapid sterilization of the bacteria and virus, electrical stimulation sterilization was adopted to endow cellulose fibers with instantaneous antibacterial and antiviral properties. In the proposed strategy, the fiber is fluffed by mechanical refining, and then by means of the hydrogen bond between hydroxyl and aniline, the polyaniline (PANI) directionally grows vertically along the fine fibers via in-situ oxidative polymerization. Benefiting from the conductive polyaniline nanorod arrays on the fiber stem, the paper made from PANI modified refined fibers (PANI/BCF/P) exhibited excellent antibacterial and antiviral activity, the inhibition rates against S. aureus, E. coli, and bacteriophage MS2 can up to 100 %, 100 %, and 99.89 %, respectively when a weak voltage (2.5 V) was applied within 20 min. This study provides a feasible path for plant fiber to achieve efficient antibacterial and antiviral activity with electrical stimulation, which is of great significance for the preparation of electroactive antibacterial and antiviral green health products.

In vitro activity of cefiderocol against carbapenemase-producing and meropenem-non-susceptible Gram-negative bacteria collected in the Japan Antimicrobial Resistant Bacterial Surveillance

OBJECTIVES

The treatment options available for infections caused by multidrug-resistant Gram-negative pathogens are often limited. Cefiderocol (CFDC) is a novel siderophore cephalosporin that exhibits activity against these pathogens. Several studies have reported the in vitro activity of CFDC against isolates from Europe, the United States, and China, but the activity against carbapenem-resistant bacteria with IMP-type carbapenemase has not been extensively studied. We, therefore, studied the in vitro activities of CFDC against carbapenem-resistant bacteria with available genomic backgrounds based on whole-genome sequencing (WGS) in Japan, where the IMP-type is the predominant carbapenemase produced by Gram-negative rods.

METHODS

We selected 603 isolates (528 Enterobacterales, 18 Pseudomonas aeruginosa, and 57 Acinetobacter spp.) from a collection of Gram-negative clinical isolates collected during a Japan Antimicrobial Resistance Bacterial Surveillance program and evaluated the antimicrobial activities of CFDC, ceftolozane/tazobactam (CTLZ/TAZ), imipenem-relebactam (IPM/REL), and ceftazidime/avibactam (CAZ/AVI) against carbapenemase-producing Enterobacterales, carbapenemase-non-producing meropenem-non-susceptible Enterobacterales, and carbapenemase-producing nonfermentative bacteria.

RESULTS

Among these, 97.7% of carbapenemase-producing Enterobacterales (99.2% of IMP-type carbapenemase-producing Enterobacterales), 100% of carbapenemase-producing P. aeruginosa, and 91.2% of carbapenemase-producing Acinetobacter spp. were susceptible to CFDC, showing better antimicrobial activity than the other antimicrobial agents evaluated in this study. CFDC was highly effective against class A-, B-, and D β-lactamase-harbouring isolates when compared to the other antimicrobial agents. In addition, the relationship between CFDC resistance and three genetic factors involved in resistance was discussed.

CONCLUSIONS

This is the first large-scale study to systematically demonstrate the efficacy of CFDC against IMP-type carbapenemase-producing strains with known genomic backgrounds.

Stenotrophomonas maltophilia virulence: a current view

Stenotrophomonas maltophilia is an opportunistic pathogen intrinsically resistant to multiple and broad-spectrum antibiotics. Although the bacterium is considered a low-virulence pathogen, it can cause various severe diseases and contributes significantly to the pathogenesis of multibacterial infections. During the COVID-19 pandemic, S. maltophilia has been recognized as one of the most common causative agents of respiratory co-infections and bacteremia in critically ill COVID-19 patients. The high ability to adapt to unfavorable environments and new habitat niches, as well as the sophisticated switching of metabolic pathways, are unique mechanisms that attract the attention of clinical researchers and experts studying the fundamental basis of virulence. In this review, we have summarized the current knowledge on the molecular aspects of S. maltophilia virulence and putative virulence factors, partially touched on interspecific bacterial interactions and iron uptake systems in the context of virulence, and have not addressed antibiotic resistance.

Characterization of β-lactamase and virulence genes in Pseudomonas aeruginosa isolated from clinical, environmental and poultry sources in Bangladesh

The emergence and spread of multidrug-resistant pathogens like Pseudomonas aeruginosa are major concerns for public health worldwide. This study aimed to assess the prevalence of P. aeruginosa in clinical, environmental, and poultry sources in Bangladesh, along with their antibiotic susceptibility and the profiling of β-lactamase and virulence genes using standard molecular and microbiology techniques. We collected 110 samples from five different locations, viz., BAU residential area (BAURA; n = 15), BAU Healthcare Center (BAUHCC; n = 20), BAU Veterinary Teaching Hospital (BAUVTH; n = 22), Poultry Market (PM; n = 30) and Mymensingh Medical College Hospital (MCCH; n = 23). After overnight enrichment in nutrient broth, 89 probable Pseudomonas isolates (80.90%) were screened through selective culture, gram-staining and biochemical tests. Using genus- and species-specific PCR, we confirmed 22 isolates (20.0%) as P. aeruginosa from these samples. Antibiogram profiling revealed that 100.0% P. aeruginosa isolates (n = 22) were multidrug-resistant isolates, showing resistance against Doripenem, Penicillin, Ceftazidime, Cefepime, and Imipenem. Furthermore, resistance to aztreonam was observed in 95.45% isolates. However, P. aeruginosa isolates showed a varying degree of sensitivity against Amikacin, Gentamicin, and Ciprofloxacin. The blaTEM gene was detected in 86.0% isolates, while blaCMY, blaSHV and blaOXA, were detected in 27.0%, 18.0% and 5.0% of the P. aeruginosa isolates, respectively. The algD gene was detected in 32.0% isolates, whereas lasB and exoA genes were identified in 9.0% and 5.0% P. aeruginosa isolates. However, none of the P. aeruginosa isolates harbored exoS gene. Hence, this study provides valuable and novel insights on the resistance and virulence of circulating P. aeruginosa within the clinical, environmental, and poultry environments of Bangladesh. These findings are crucial for understanding the emergence of β-lactamase resistance in P. aeruginosa, highlighting its usefulness in the treatment and control of P. aeruginosa infections in both human and animal populations.

Antibiotic class with potent in vivo activity targeting lipopolysaccharide synthesis in Gram-negative bacteria

Here, we describe the identification of an antibiotic class acting via LpxH, a clinically unexploited target in lipopolysaccharide synthesis. The lipopolysaccharide synthesis pathway is essential in most Gram-negative bacteria and there is no analogous pathway in humans. Based on a series of phenotypic screens, we identified a hit targeting this pathway that had activity on efflux-defective strains of Escherichia coli. We recognized common structural elements between this hit and a previously published inhibitor, also with activity against efflux-deficient bacteria. With the help of X-ray structures, this information was used to design inhibitors with activity on efflux-proficient, wild-type strains. Optimization of properties such as solubility, metabolic stability and serum protein binding resulted in compounds having potent in vivo efficacy against bloodstream infections caused by the critical Gram-negative pathogens E. coli and Klebsiella pneumoniae. Other favorable properties of the series include a lack of pre-existing resistance in clinical isolates, and no loss of activity against strains expressing extended-spectrum-β-lactamase, metallo-β-lactamase, or carbapenemase-resistance genes. Further development of this class of antibiotics could make an important contribution to the ongoing struggle against antibiotic resistance.

Anti-inflammatory and immunoregulatory effects of colistin sulphate on human PBMCs

In previous studies, CST has been identified as having an immunostimulatory effect on Caenorhabditis elegans and macrophage of rats. Here, we further investigated its immunomodulatory effects on human peripheral blood mononuclear cells (PBMCs). LPS-stimulated PBMCs inflammatory model was established. Flow cytometry was applied to measure phagocytosis of PBMCs. Cytokine mRNA and protein expression levels of LPS-stimulated PBMCs with or without CST were measured by qRT-PCR and ELISA. The transcriptomic profile of CST-treated PBMCs was investigated by RNA-sequencing. Gene Ontology (GO) and Kyoto Encylopedia of Genes and Genomes (KEGG) were applied to find potential signalling pathways. PBMCs showed a significant increase in phagocytic activity at 6 h after being incubated with CST at the concentration of 10 μg/mL. In the presence of LPS, CST maintained and promoted the expression of TNF-α and chemokine CCL24. The content of pro-inflammatory cytokines, such as IL-1β, IL-6 and IFN-γ, which were released from LPS-stimulated PBMCs, was reduced by CST at 6 h. Anti-inflammatory cytokines, such as IL-4, IL-13 and TGF-β1, were significantly increased by CST at 24 h. A total of 277 differentially expressed immune-related genes (DEIRGs) were detected and cytokine-cytokine receptor interaction was highly enriched. CST presented obvious anti-inflammatory and immunoregulatory effects in LPS-induced PBMCs inflammatory model not only by improving the ability of PBMCs to clear pathogens but also by decreasing pro-inflammatory cytokines and increasing anti-inflammatory cytokines. And the mechanism may be related to cytokine-cytokine receptor interaction.

Synthesis and Antimicrobial Activity Evaluation of Pyridine Derivatives Containing Imidazo[2,1-b][1,3,4]Thiadiazole Moiety

Four series of novel pyridine derivatives (17 a-i, 18 a-i, 19 a-e, and 20 a-e) were synthesized and their antimicrobial activities were evaluated. Of all the target compounds, almost half target compounds showed moderate or high antibacterial activity. The 4-F substituted compound 17 d (MIC=0.5 μg/mL) showed the highest antibacterial activity, its activity was twice the positive control compound gatifloxacin (MIC=1.0 μg/mL). For fungus ATCC 9763, the activities of compounds 17 a and 17 d are equivalent to the positive control compound fluconazole (MIC=8 μg/mL). Furthermore, compounds 17 a and 17 d showed little cytotoxicity to human LO2 cells, and did not show hemolysis even at ultra-high concentration (200 μM). The results indicate that these compounds are valuable for further development as antibacterial and antifungal agents.

Genomic Characterization of a Carbapenem-Resistant Raoultella planticola Strain Co-Harboring blaIMP-4 and blaSHV-12 Genes

Raoultella planticola is an emerging bacterial pathogen responsible for causing infections in both humans and animals. Unfortunately, sporadic reports of carbapenem-resistant R. planticola (CRRP) have been documented worldwide. Here we first reported the complete genome sequence of a CRRP isolate RP_3045 co-carrying blaIMP-4 and blaSHV-12, recovered from a patient in China, and its genetic relatedness to 82 R. planticola strains deposited in the NCBI GenBank database, sourced from humans, animals, and the environment. Whole-genome sequencing was performed using the Illumina NovaSeq 6000 and Oxford Nanopore MinION platforms. Phylogenetic analysis was also performed and visualized using a single nucleotide polymorphism (SNP)-based strategy. The complete genome of R. planticola strain RP_3045 was determined to be 6,312,961 bp in length, comprising five contigs that included one chromosome and four plasmids. RP_3045 was found to be multidrug-resistant and harbored several antimicrobial resistance genes, including both blaIMP-4 and blaSHV-12 genes located on a single plasmid. The most closely related strain was hkcpe63, recovered from humans in Hong Kong, China, in 2014, with 506 SNP differences. R. planticola strains were distributed globally and exhibited strong associations among isolates obtained from different sectors. This study provides evidence for the potential of R. planticola to disseminate carbapenem resistance across different sectors, highlighting the critical need for active and continuous surveillance of CRRP.

Sequence-structure-function characterization of the emerging tetracycline destructase family of antibiotic resistance enzymes

Tetracycline destructases (TDases) are flavin monooxygenases which can confer resistance to all generations of tetracycline antibiotics. The recent increase in the number and diversity of reported TDase sequences enables a deep investigation of the TDase sequence-structure-function landscape. Here, we evaluate the sequence determinants of TDase function through two complementary approaches: (1) constructing profile hidden Markov models to predict new TDases, and (2) using multiple sequence alignments to identify conserved positions important to protein function. Using the HMM-based approach we screened 50 high-scoring candidate sequences in Escherichia coli, leading to the discovery of 13 new TDases. The X-ray crystal structures of two new enzymes from Legionella species were determined, and the ability of anhydrotetracycline to inhibit their tetracycline-inactivating activity was confirmed. Using the MSA-based approach we identified 31 amino acid positions 100% conserved across all known TDase sequences. The roles of these positions were analyzed by alanine-scanning mutagenesis in two TDases, to study the impact on cell and in vitro activity, structure, and stability. These results expand the diversity of TDase sequences and provide valuable insights into the roles of important residues in TDases, and flavin monooxygenases more broadly.

Design, synthesis and antibacterial evaluation of low toxicity amphiphilic-cephalosporin derivatives

Global public health is facing a serious problem as a result of the rise in antibiotic resistance and the decline in the discovery of new antibiotics. In this study, two series of amphiphilic-cephalosporins were designed and synthesized, several of which showed good antibacterial activity against both Gram-positive and Gram-negative bacteria. Structure-activity relationships indicated that the length of the hydrophobic alkyl chain significantly affects the antibacterial activity against Gram-negative bacteria. The best compound 2d showed high activity against drug-susceptible Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) with MICs of 0.5 and 2-4 μg/mL, respectively. Furthermore, 2d remained active in complex mammalian body fluids and had a longer post-antibiotic effect (PAE) than vancomycin. Mechanism studies indicated that compound 2d lacks membrane-damaging properties and can target penicillin-binding proteins to disrupt bacterial cell wall structure, inhibit the metabolic activity and induce the accumulation of reactive oxygen species (ROS) in bacteria. Compound 2d showed minimal drug resistance and was nontoxic to HUVEC and HBZY-1 cells with CC50 > 128 μg/mL. These findings suggest that 2d is a promising drug candidate for treating bacterial infections.

Hetero-antagonism of avibactam and sulbactam with cefiderocol in carbapenem-resistant Acinetobacter spp

The emergence of Gram-negative bacteria resistant to multiple antibiotics, particularly carbapenem-resistant (CR) Acinetobacter strains, poses a significant threat globally. Despite efforts to develop new antimicrobial therapies, limited progress has been made, with only two drugs-cefiderocol and sulbactam-durlobactam-showing promise for CR-Acinetobacter infections. Cefiderocol, a siderophore cephalosporin, demonstrates promising efficacy in the treatment of Gram-negative infections. However, resistance to cefiderocol has been reported in A. baumannii. Combination therapies, such as cefiderocol with avibactam or sulbactam, show reduced MICs against cefiderocol-non-susceptible strains with in vivo efficacy, although the outcomes can be complex and species-specific. In the present work, the molecular characterization of spontaneous cefiderocol-resistant variants, a CRAB strain displaying antagonism with sulbactam and an A. lwoffii strain showing antagonism with avibactam, were studied. The results reveal intriguing insights into the underlying mechanisms, including mutations affecting efflux pumps, transcriptional regulators, and iron homeostasis genes. Moreover, gene expression analysis reveals significant alterations in outer membrane proteins, iron homeostasis, and β-lactamases, suggesting adaptive responses to selective pressure. Understanding these mechanisms is crucial for optimizing treatment strategies and preventing adverse clinical outcomes. This study highlights the importance of preemptively assessing drug synergies to navigate the challenges posed by antimicrobial resistance in CR-Acinetobacter infections.

AI-aided geometric design of anti-infection catheters

Bacteria can swim upstream in a narrow tube and pose a clinical threat of urinary tract infection to patients implanted with catheters. Coatings and structured surfaces have been proposed to repel bacteria, but no such approach thoroughly addresses the contamination problem in catheters. Here, on the basis of the physical mechanism of upstream swimming, we propose a novel geometric design, optimized by an artificial intelligence model. Using Escherichia coli, we demonstrate the anti-infection mechanism in microfluidic experiments and evaluate the effectiveness of the design in three-dimensionally printed prototype catheters under clinical flow rates. Our catheter design shows that one to two orders of magnitude improved suppression of bacterial contamination at the upstream end, potentially prolonging the in-dwelling time for catheter use and reducing the overall risk of catheter-associated urinary tract infection.

Discovery of novel tetrahydrobenzothiophene derivatives as MSBA inhibitors for antimicrobial agents

The incidence of infections caused by drug-resistant bacteria has been one of the most serious health threats in the past and is substantially increasing in an alarming rate. Therefore, the development of new antimicrobial agents to combat bacterial resistance effectively is urgent. This study focused on the design and synthesis of 40 novel tetrahydrobenzothiophene amide/sulfonamide derivatives and their antibacterial activities were evaluated. Compounds 2p, 6p, and 6 s exhibited significant inhibitory effects on the growth of bacteria. To assess their safety, the cytotoxicity of the compounds was assessed using human normal liver cells, revealing that compound 6p has lower cytotoxicity. A mouse wound healing experiment demonstrated that compound 6p effectively improved wound infection induced by trauma and accelerated the healing process. Compound 6p holds promise as a potential therapeutic agent for combating bacterial infections.

Treatment of MRSA Infection: Where are We?

Staphylococcus aureus is a leading cause of septicemia, endocarditis, pneumonia, skin and soft tissue infections, bone and joint infections, and hospital-acquired infections. In particular, methicillin-resistant Staphylococcus aureus (MRSA) is associated with high morbidity and mortality, and continues to be a major public health problem. The emergence of multidrug-resistant MRSA strains along with the wide consumption of antibiotics has made anti-MRSA treatment a huge challenge. Novel treatment strategies (e.g., novel antimicrobials and new administrations) against MRSA are urgently needed. In the past decade, pharmaceutical companies have invested more in the research and development (R&D) of new antimicrobials and strategies, spurred by favorable policies. All research articles were collected from authentic online databases, including Google Scholar, PubMed, Scopus, and Web of Science, by using different combinations of keywords, including 'anti-MRSA', 'antibiotic', 'antimicrobial', 'clinical trial', 'clinical phase', clinical studies', and 'pipeline'. The information extracted from articles was compared to information provided on the drug manufacturer's website and Clinical Trials.gov (https://clinicaltrials.gov/) to confirm the latest development phase of anti-MRSA agents. The present review focuses on the current development status of new anti-MRSA strategies concerning chemistry, pharmacological target(s), indications, route of administration, efficacy and safety, pharmacokinetics, and pharmacodynamics, and aims to discuss the challenges and opportunities in developing drugs for anti-MRSA infections.

Artificial intelligence and machine learning in clinical pharmacological research

BACKGROUND

Clinical pharmacology research has always involved computational analysis. With the abundance of drug-related data available, the integration of artificial intelligence (AI) and machine learning (ML) methods has emerged as a promising way to enhance clinical pharmacology research.

METHODS

Based on an accepted definition of clinical pharmacology as a field of research dealing with all aspects of drug-human interactions, the analysis included publications from institutes specializing in clinical pharmacology. Research topics and the most used machine learning methods in clinical pharmacology were retrieved from the PubMed database and summarized.

RESULTS

ML was identified in 674 publications attributed to clinical pharmacology research, with a significant increase in publication activity over the last decade. Notable research topics addressed by ML/AI included Covid-19-related clinical pharmacology research, clinical neuropharmacology, drug safety and risk assessment, clinical pharmacology related to cancer research, and antimicrobial and antiviral research unrelated to Covid-19. In terms of ML methods, neural networks, random forests, and support vector machines were frequently mentioned in the abstracts of the retrieved papers.

CONCLUSIONS

ML, and AI in general, is increasingly being used in various research areas within clinical pharmacology. This report presents specific examples of applications and highlights the most used ML methods.

A review of chemical signaling pathways in the quorum sensing circuit of Pseudomonas aeruginosa

Pseudomonas aeruginosa, an increasingly common competitive and biofilm organism in healthcare infection with sophisticated, interlinked and hierarchic quorum systems (Las, Rhl, PQS, and IQS), creates the greatest threats to the medical industry and has rendered prevailing chemotherapy medications ineffective. The rise of multidrug resistance has evolved into a concerning and potentially fatal occurrence for human life. P. aeruginosa biofilm development is assisted by exopolysaccharides, extracellular DNA, proteins, macromolecules, cellular signaling and interaction. Quorum sensing is a communication process between cells that involves autonomous inducers and regulators. Quorum-induced infectious agent biofilms and the synthesis of virulence factors have increased disease transmission, medication resistance, infection episodes, hospitalizations and mortality. Hence, quorum sensing may be a potential therapeutical target for bacterial illness, and developing quorum inhibitors as an anti-virulent tool could be a promising treatment strategy for existing antibiotics. Quorum quenching is a prevalent technique for treating infections caused by microbes because it diminishes microbial pathogenesis and increases microbe biofilm sensitivity to antibiotics, making it a potential candidate for drug development. This paper examines P. aeruginosa quorum sensing, the hierarchy of quorum sensing mechanism, quorum sensing inhibition and quorum sensing inhibitory agents as a drug development strategy to supplement traditional antibiotic strategies.

In vitro and in vivo antimicrobial potential of lithium complex against multi-drug resistant Acinetobacter baumannii

IMPORTANCE

Multi-drug resistance (MDR) by virtue of evolving resistance and virulence mechanisms among A. baumannii is a global concern which is responsible for lethal hospital-acquired infections. Therefore, it is crucial to develop new therapeutics against it. Metal complexes are compact structures with diverse mechanisms that the pathogens cannot evade easily which make them a strong drug candidate. In this study, we assessed the in vitro and in vivo efficacy of lithium complex {[Li(phen)2 sal]} against biofilm-forming MDR A. baumannii. The lithium complex displayed strong antimicrobial activity and reduced the pre-formed mature biofilm which is key barrier for antimicrobial action. Moreover, it employs oxidative stress as one of its mode of actions and causes cellular rupturing. Lithium complex was non-toxic and was significantly effective to overcome pneumonia in mice model. These results highlight the untapped potential of metal complexes that can be explored and utilized for combating notorious A. baumannii infections.

Synthesis and antimicrobial activity of aminoalkyl resveratrol derivatives inspired by cationic peptides

Antimicrobial resistance is a global concern, far from being resolved. The need of new drugs against new targets is imminent. In this work, we present a family of aminoalkyl resveratrol derivatives with antibacterial activity inspired by the properties of cationic amphipathic antimicrobial peptides. Surprisingly, the newly designed molecules display modest activity against aerobically growing bacteria but show surprisingly good antimicrobial activity against anaerobic bacteria (Gram-negative and Gram-positive) suggesting specificity towards this bacterial group. Preliminary studies into the action mechanism suggest that activity takes place at the membrane level, while no cross-resistance with traditional antibiotics is observed. Actually, some good synergistic relations with existing antibiotics were found against Gram-negative pathogens. However, some cytotoxicity was observed, despite their low haemolytic activity. Our results show the importance of the balance between positively charged moieties and hydrophobicity to improve antimicrobial activity, setting the stage for the design of new drugs based on these molecules.

A self-reported inhibitor of metallo-carbapenemases for reversing carbapenem resistance

Metallo-carbapenemases-mediated carbapenem-resistant Enterobacterales (CREs) has been acknowledged as "urgent threat" by the World Health Organization. The discovery of new strategies that block metallo-carbapenemases activity to reverse carbapenem resistance is an urgent need. In this study, a coumarin copper complex containing a PEG linker and glucose ligand, GluC-Cu, was used to reverse carbapenem resistance. Interestingly, it could effectively inhibit metallo-carbapenemases (NDM-1, IMP-1 and ImiS) with an IC50 value in the range of 0.23-1.21 μM, and simultaneously release the green fluorescence signal (GluC), therefore exhibiting self-reported inhibition performance. The inhibition mechanism of oxidizing Zn(II) thiolate site of NDM-1 from Cu2+ to Cu+ was verified by fluorescence assay, HR-MS, and XPS. Moreover, GluC-Cu in combination with meropenem showed excellent synergistic antibacterial effect to effectively combat E. coli expressing metallo-carbapenemases in vitro and in a mice infection model. This bifunctional metallo-carbapenemases inhibitor provides a novel chemical tool to overcome carbapenem resistance.

Photopolymerized keratin-PGLa hydrogels for antibiotic resistance reversal and enhancement of infectious wound healing

Infectious wounds have become serious challenges for both treatment and management in clinical practice, so development of new antibiotics has been considered an increasingly difficult task. Here, we report the design and synthesis of keratin 31 (K31)-peptide glycine-leucine-amide (PGLa) photopolymerized hydrogels to rescue the antibiotic activity of antibiotics for infectious wound healing promotion. K31-PGLa displayed an outstanding synergistic effect with commercial antibiotics against drug-resistant bacteria by down-regulating the synthesis genes of efflux pump. Furthermore, the photopolymerized K31-PGLa/PEGDA hydrogels effectively suppressed drug-resistant bacteria growth and enhanced skin wound closure in murine. This study provided a promising alternative strategy for infectious wound treatment.

Synthesis of peptidomimetics as antibiotic adjuvants for combination with aztreonam to combat MDR Pseudomonas aeruginosa

Pseudomonas aeruginosa is one of the multipledrug-resistant (MDR) Gram-negative pathogens with few drugs available for treatment. Antibiotic adjuvant approach provides an alternative and complementary strategy. In this study, the stereo-structure-activity relationship of monobactams against MDR Gram-negative organisms was extended. Meanwhile, a series of novel peptidemimetic derivatives as antibiotic adjuvants was synthesized and evaluated for their synergistic effects with aztreonam (AZT) against P. aeruginosa, using dipeptide PAβN as the lead. Among the analogues, compound 22j showed a significant synergistic effect against MDR P. aeruginosa in vitro and in vivo, presumably through the mechanism of affecting the permeability of outer membrane. Thus, we identified 22j as a novel peptidemimetic lead compound to potentiate the activity of AZT against MDR P. aeruginosa, which is worthy of further development as antibiotic adjuvant candidates.

Small-Molecule Antibiotic Drug Development: Need and Challenges

The need for new antibiotics is urgent. Antimicrobial resistance is rising, although currently, many more people die from drug-sensitive bacterial infections. The continued evolution of drug resistance is inevitable, fueled by pathogen population size and exposure to antibiotics. Additionally, opportunistic pathogens will always pose a threat to vulnerable patients whose immune systems cannot efficiently fight them even if they are sensitive to available antibiotics, according to clinical microbiology tests. These problems are intertwined and will worsen as human populations age, increase in density, and experience disruptions such as war, extreme weather events, or declines in standard of living. The development of appropriate drugs to treat all the world's bacterial infections should be a priority, and future success will likely require combinations of multiple approaches. However, the highest burden of bacterial infection is in Low- and Middle-Income Countries, where limited medical infrastructure is a major challenge. For effectively managing infections in these contexts, small-molecule-based treatments offer significant advantages. Unfortunately, support for ongoing small-molecule antibiotic discovery has recently suffered from significant challenges related both to the scientific difficulties in treating bacterial infections and to market barriers. Nevertheless, small-molecule antibiotics remain essential and irreplaceable tools for fighting infections, and efforts to develop novel and improved versions deserve ongoing investment. Here, we first describe the global historical context of antibiotic treatment and then highlight some of the challenges surrounding small-molecule development and potential solutions. Many of these challenges are likely to be common to all modalities of antibacterial treatment and should be addressed directly.

Evaluating the innovative potential of the global antibacterial pipeline

BACKGROUND

Resistance burden varies widely among WHO regions, and the potential impact of new antibiotics differs in addressing the WHO's critical priority pathogens' resistance challenge.

OBJECTIVES

To analyse the current global clinical pipeline in line with public and global health concerns and define innovation in antibacterial drug discovery.

SOURCES

Monitoring clinical pipelines since 2006, integrating peer-reviewed MEDLINE publications on clinical development of new antibacterial agents, supplemented with disclosed data from developers.

CONTENT

The current clinical pipeline is dominated by derivatives of established antibiotic classes, primarily β-lactamase inhibitor combinations in Phase 3 (six of ten which also include two beta-lactams without β-lactamase inhibitor). This pattern extends to Phase 1. Although incremental improvements in susceptibility rates among derivatives benefit patients in advanced health care systems within specific geographical regions, these concepts are not adequate for carbapenem-resistant strains of Enterobacterales (especially Klebsiella and Escherichia coli), Acinetobacter, and Pseudomonas. This limitation arises from the diverse distribution of resistance mechanisms across global regions. Innovation in this context refers to absence of cross-resistance because of class-specific resistance mechanisms. This can most likely be achieved by exploring new chemical classes and new targets/binding sites, and new mode of action. An initial glimpse of progress is evident as innovative agents progressed to Phase 1 clinical trials. However, an influx of more agents advancing to clinical development is essential given the inherent risks associated with novel chemistry and targets.

IMPLICATIONS

The limited innovation in the global clinical pipeline inadequately serves public and global health interests. The complexities of antibacterial drug discovery, from scientific challenges to financial constraints, underscore the need for collective researcher efforts and public support to drive innovation for patients globally.

Facile Synthesis of Self-Targeted Zn2+ -Gallic acid Nanoflowers for Specific Adhesion and Elimination of Gram-Positive Bacteria

Transition metal ions are served as disinfectant thousand years ago. However, the in vivo antibacterial application of metal ions is strongly restricted due to its high affinity with proteins and lack of appropriate bacterial targeting method. Herein, for the first time, Zn2+ -gallic acid nanoflowers (ZGNFs) are synthesized by a facile one-pot method without additional stabilizing agents. ZGNFs are stable in aqueous solution while can be easily decomposed in acidic environments. Besides, ZGNFs can specifically adhere onto Gram-positive bacteria, which is mediated by the interaction of quinone from ZGNFs and amino groups from teichoic acid of Gram-positive bacteria. ZGNFs exhibit high bactericidal effect toward various Gram-positive bacteria in multiple environments, which can be ascribed to the in situ Zn2+ release on bacterial surface. Transcriptome studies reveal that ZGNFs can disorder basic metabolic processes of Methicillin-resistant Staphylococcus aureus (MRSA). Moreover, in a MRSA-induced keratitis model, ZGNFs exhibit long-term retention in the infected corneal site and prominent MRSA elimination efficacy due to the self-targeting ability. This research not only reports an innovative method to prepare metal-polyphenol nanoparticles, but also provides a novel nanoplatform for targeted delivery of Zn2+ in combating Gram-positive bacterial infections.

Eugenol works synergistically with colistin against colistin-resistant Pseudomonas aeruginosa and Klebsiella pneumoniae isolates by enhancing membrane permeability

Colistin is a potent antibiotic for the treatment of carbapenem-resistant Gram-negative bacteria and is considered a last-resort drug. Unfortunately, the incidence of colistin-resistant bacteria isolated from patients is continuously growing due to clinical reuse of colistin. In this study, we found that the combination of colistin and eugenol has a significant synergistic antibacterial effect and reverses the sensitivity of colistin-resistant Pseudomonas aeruginosa and Klebsiella pneumoniae against colistin, as confirmed by checkerboard and time-kill assays. Crystal violet staining and scanning electron microscopy revealed colistin and eugenol's synergistic antibiofilm action. Concerning the synergy mechanism, the results revealed that the combination of eugenol and colistin increases membrane permeability and causes considerable membrane damage, further inhibiting bacteria synergistically. Meanwhile, up to 500 µg/mL of eugenol is non-toxic to RAW 264.7 cells, and the colistin/eugenol combination is also efficacious in vivo, as demonstrated by the Galleria mellonella infection model. Our findings indicate that the colistin/eugenol combination is a viable treatment option for colistin-resistant P. aeruginosa and K. pneumoniae clinical infections. IMPORTANCE Colistin is used as a last resort for severe infections caused by multidrug-resistant Gram-negative bacteria, however, colistin resistance is increasing. As a result, we investigated the synergistic effect of eugenol/colistin combination, and the results revealed significant antibacterial and antibiofilm action. Eugenol may help clinical colistin-resistant Pseudomonas aeruginosa and Klebsiella pneumoniae recover their susceptibility. These findings suggest that combining eugenol and colistin may be a viable treatment option for colistin-resistant pathogen clinical infections.

Design of novel water-soluble isoxazole-based antimicrobial agents and evaluation of their cytotoxicity and acute toxicity

Based on the readily available 3-organyl-5-(chloromethyl)isoxazoles, a number of previously unknown water-soluble conjugates of isoxazoles with thiourea, amino acids, some secondary and tertiary amines, and thioglycolic acid were synthesized. The bacteriostatic activity of aforementioned compounds has been studied against Enterococcus durans B-603, Bacillus subtilis B-407, Rhodococcus qingshengii Ac-2784D, and Escherichia coli B-1238 microorganisms (provided by All-Russian Collection of Microorganisms, VKM). The influence of the nature of the substituents in positions 3 and 5 of the isoxazole ring on the antimicrobial activity of the obtained compounds has been determined. It is found that the highest bacteriostatic effect is observed for compounds containing 4-methoxyphenyl or 5-nitrofuran-2-yl substituents in position 3 of the isoxazole ring as well as methylene group in position 5 bearing residues of l-proline or N-Ac-l-cysteine (5a-d, MIC 0.06-2.5 µg/ml). The leading compounds showed low cytotoxicity on normal human skin fibroblast cells (NAF1nor) and low acute toxicity on mice in comparison with the well-known isoxazole-containing antibiotic oxacillin.

Multiplex lateral flow test strip for detection of carbapenemase genes using barcoded tetrahedral DNA capture probe-based biosensing interface

Carbapenem-resistant Enterobacterales pose significant global health challenges due to their rapid spread and ability to hydrolyse various beta-lactam antibiotics. Rapid tests for these carbapenemase genes are crucial to ensure appropriate prescription administration and infection control. In this study, we developed a rapid visual nanodiagnostic platform for multiplexed detection of carbapenemase genes using a lateral flow strip. The nanodiagnostic strip was designed with separate barcoded DNA tetrahedrons for the blaKPC and blaNDM genes. These tetrahedrons were distributed on a nitrocellulose membrane at two different test lines as capture probes. When tested against a panel of carbapenemase genes, the tetrahedral probes captured single-stranded amplicons of asymmetric PCR via strand hybridisation. The amplicons acted as bridging elements, binding the DNA-modified gold nanoparticles to the test line of the strip, resulting in clear visual readouts specific to the blaKPC and blaNDM genes. By employing barcoded tetrahedrons and asymmetric PCR in conjunction with the lateral flow strip, a single diagnostic test enabled the detection of multiple carbapenemase genes. The test yielded results as low as 0.12 fM for blaKPC and 0.05 fM for blaNDM within 75 min. Furthermore, the strip effectively identified specific carbapenemase genes in clinical isolates using real-time PCR, antibody-based lateral flow systems for carbapenemase detection, and carbapenemase phenotype experiments. Thus, the strip develop has a high potential for testing blaKPC and blaNDM genes in practice.

Antibiotics in the clinical pipeline as of December 2022

The need for new antibacterial drugs to treat the increasing global prevalence of drug-resistant bacterial infections has clearly attracted global attention, with a range of existing and upcoming funding, policy, and legislative initiatives designed to revive antibacterial R&D. It is essential to assess whether these programs are having any real-world impact and this review continues our systematic analyses that began in 2011. Direct-acting antibacterials (47), non-traditional small molecule antibacterials (5), and β-lactam/β-lactamase inhibitor combinations (10) under clinical development as of December 2022 are described, as are the three antibacterial drugs launched since 2020. Encouragingly, the increased number of early-stage clinical candidates observed in the 2019 review increased in 2022, although the number of first-time drug approvals from 2020 to 2022 was disappointingly low. It will be critical to monitor how many Phase-I and -II candidates move into Phase-III and beyond in the next few years. There was also an enhanced presence of novel antibacterial pharmacophores in early-stage trials, and at least 18 of the 26 phase-I candidates were targeted to treat Gram-negative bacteria infections. Despite the promising early-stage antibacterial pipeline, it is essential to maintain funding for antibacterial R&D and to ensure that plans to address late-stage pipeline issues succeed.

Design of Protegrin-1 Analogs with Improved Antibacterial Selectivity

Protegrin-1 (PG-1) is a cationic β-hairpin pore-forming antimicrobial peptide having a membranolytic mechanism of action. It possesses in vitro a potent antimicrobial activity against a panel of clinically relevant MDR ESKAPE pathogens. However, its extremely high hemolytic activity and cytotoxicity toward mammalian cells prevent the further development of the protegrin-based antibiotic for systemic administration. In this study, we rationally modulated the PG-1 charge and hydrophobicity by substituting selected residues in the central β-sheet region of PG-1 to design its analogs, which retain a high antimicrobial activity but have a reduced toxicity toward mammalian cells. In this work, eight PG-1 analogs with single amino acid substitutions and five analogs with double substitutions were obtained. These analogs were produced as thioredoxin fusions in Escherichia coli. It was shown that a significant reduction in hemolytic activity without any loss of antimicrobial activity could be achieved by a single amino acid substitution, V16R in the C-terminal β-strand, which is responsible for the PG-1 oligomerization. As the result, a selective analog with a ≥30-fold improved therapeutic index was obtained. FTIR spectroscopy analysis of analog, [V16R], revealed that the peptide is unable to form oligomeric structures in a membrane-mimicking environment, in contrast to wild-type PG-1. Analog [V16R] showed a reasonable efficacy in septicemia infection mice model as a systemic antibiotic and could be considered as a promising lead for further drug design.

Induced Heteroresistance in Carbapenem-Resistant Acinetobacter baumannii (CRAB) via Exposure to Human Pleural Fluid (HPF) and Its Impact on Cefiderocol Susceptibility

Infections caused by Carbapenem-resistant Acinetobacter baumannii (CRAB) isolates, such as hospital-acquired pneumonia (HAP), bacteremia, and skin and soft tissue infections, among others, are particularly challenging to treat. Cefiderocol, a chlorocatechol-substituted siderophore antibiotic, was approved by the U.S. Food and Drug Administration (FDA) in 2019 and prescribed for the treatment of CRAB infections. Despite the initial positive treatment outcomes with this antimicrobial, recent studies reported a higher-than-average all-cause mortality rate in patients treated with cefiderocol compared to the best available therapy. The cause(s) behind these outcomes remains unconfirmed. A plausible hypothesis is heteroresistance, a phenotype characterized by the survival of a small proportion of cells in a population that is seemingly isogenic. Recent results have demonstrated that the addition of human fluids to CRAB cultures leads to cefiderocol heteroresistance. Here, we describe the molecular and phenotypic analyses of CRAB heteroresistant bacterial subpopulations to better understand the nature of the less-than-expected successful outcomes after cefiderocol treatment. Isolation of heteroresistant variants of the CRAB strain AMA40 was carried out in cultures supplemented with cefiderocol and human pleural fluid (HPF). Two AMA40 variants, AMA40 IHC1 and IHC2, were resistant to cefiderocol. To identify mutations and gene expression changes associated with cefiderocol heteroresistance, we subjected these variants to whole genome sequencing and global transcriptional analysis. We then assessed the impact of these mutations on the pharmacodynamic activity of cefiderocol via susceptibility testing, EDTA and boronic acid inhibition analysis, biofilm formation, and static time-kill assays. Heteroresistant variants AMA40 IHC1 and AMA40 IHC2 have 53 chromosomal mutations, of which 40 are common to both strains. None of the mutations occurred in genes associated with high affinity iron-uptake systems or β-lactam resistance. However, transcriptional analyses demonstrated significant modifications in levels of expression of genes associated with iron-uptake systems or β-lactam resistance. The blaNDM-1 and blaADC-2, as well as various iron-uptake system genes, were expressed at higher levels than the parental strain. On the other hand, the carO and ompA genes' expression was reduced. One of the mutations common to both heteroresistant strains was mapped within ppiA, a gene associated with iron homeostasis in other species. Static time-kill assays demonstrated that supplementing cation-adjusted Mueller-Hinton broth with human serum albumin (HAS), the main protein component of HPF, considerably reduced cefiderocol killing activity for all three strains tested. Notably, collateral resistance to amikacin was observed in both variants. We conclude that exposing CRAB to fluids with high HSA concentrations facilitates the rise of heteroresistance associated with point mutations and transcriptional upregulation of genes coding for β-lactamases and biofilm formation. The findings from this study hold significant implications for understanding the emergence of CRAB resistance mechanisms against cefiderocol treatment. This understanding is vital for the development of treatment guidelines that can effectively address the challenges posed by CRAB infections.

Treating urinary tract infections in the era of antibiotic resistance

INTRODUCTION

Urinary tract infections (UTIs) are associated with 25-40% of antibiotics consumed in primary care and are, therefore, driving antibiotic resistance. The worldwide increase in antibiotic resistance especially in Escherichia coli has complicated the treatment choices for UTIs and absence of effective oral antibiotics may lead to increasing need for more effective treatments.

AREAS COVERED

In this review we focus on the importance of the correct diagnosis of UTI as based on proof of urinary pathogens in the urine and discuss diagnostic measures including microscopy, dipstick, and culture. Antibiotic treatment can often await diagnostic measures with pain relief such as ibuprofen. The risk of an uncomplicated UTI leading to pyelonephritis is low (1-2%) and presence of bacteria in the bladder leaves some time for the immune system to react. Three antibiotics are recommended as based on their activity, and low propensity to select for resistance, i.e. nitrofurantoin, fosfomycin, and pivmecillinam, and in general, 3-5 days of treatment will suffice.

EXPERT OPINION

Understanding the usual benign course of uUTIs can help reduce antibiotic treatment in many cases, e.g. starting treatment by pain relief and awaiting the course of infection without antibiotics. Better rapid tests in primary care are urgently needed to enforce such policies.

Single-cell microfluidics enabled dynamic evaluation of drug combinations on antibiotic resistance bacteria

The rapid spread of antibiotic resistance has become a significant threat to global health, yet the development of new antibiotics is outpaced by emerging new resistance. To treat multidrug-resistant bacteria and prolong the lifetime of existing antibiotics, a productive strategy is to use combinations of antibiotics and/or adjuvants. However, evaluating drug combinations is primarily based on end-point checkerboard measurements, which provide limited information to study the mechanism of action and the discrepancies in the clinical outcomes. Here, single-cell microfluidics is used for rapid evaluation of the efficacy and mode of action of antibiotic combinations within 3 h. Focusing on multidrug-resistant Acinetobacter baumannii, the combination between berberine hydrochloride (BBH, as an adjuvant) and carbapenems (meropenem, MEM) or β-lactam antibiotic is evaluated. Real-time tracking of individual cells to programmable delivered antibiotics reveals multiple phenotypes (i.e., susceptible, resistant, and persistent cells) with fidelity. Our study discovers that BBH facilitates the accumulation of antibiotics within cells, indicating synergistic effects (FICI = 0.5). For example, the combination of 256 mg/L BBH and 16 mg/L MEM has a similar killing effect (i.e., the inhibition rates >90%) as the MIC of MEM (64 mg/L). Importantly, the synergistic effect of a combination can diminish if the bacteria are pre-stressed with any single drug. Such information is vital for understanding the underlying mechanisms of combinational treatments. Overall, our platform provides a promising approach to evaluate the dynamic and heterogenous response of a bacterial population to antibiotics, which will facilitate new drug discovery and reduce emerging antibiotic resistance.

A novel strategy to characterize the pattern of β-lactam antibiotic-induced drug resistance in Acinetobacter baumannii

Carbapenem-resistant Acinetobacter baumannii (CRAb) is an urgent public health threat, according to the CDC. This pathogen has few treatment options and causes severe nosocomial infections with > 50% fatality rate. Although previous studies have examined the proteome of CRAb, there have been no focused analyses of dynamic changes to β-lactamase expression that may occur due to drug exposure. Here, we present our initial proteomic study of variation in β-lactamase expression that occurs in CRAb with different β-lactam antibiotics. Briefly, drug resistance to Ab (ATCC 19606) was induced by the administration of various classes of β-lactam antibiotics, and the cell-free supernatant was isolated, concentrated, separated by SDS-PAGE, digested with trypsin, and identified by label-free LC-MS-based quantitative proteomics. Thirteen proteins were identified and evaluated using a 1789 sequence database of Ab β-lactamases from UniProt, the majority of which were Class C β-lactamases (≥ 80%). Importantly, different antibiotics, even those of the same class (e.g. penicillin and amoxicillin), induced non-equivalent responses comprising various isoforms of Class C and D serine-β-lactamases, resulting in unique resistomes. These results open the door to a new approach of analyzing and studying the problem of multi-drug resistance in bacteria that rely strongly on β-lactamase expression.

Antimicrobial activity of the Flo peptide produced in Scenedesmus acutus and Nannochloropsis oculata

The continuous increase of bacterial pathogen resistance to conventional antibiotics has challenged the research community to develop new antimicrobial strategies. Antimicrobial peptides (AMP) are a promising alternative to combat multidrug-resistant strains compared to conventional antibiotics because of their biocompatibility. In the present study, the Flo peptide, an AMP from the Moringa oleifera tree, was expressed in the chloroplast of the microalgae Nannochloropsis oculata and Scenedesmus acutus. The transgene insertion was verified by PCR amplification, and the homoplasmy was corroborated in spectinomycin-resistant lines. The identification and quantification of the peptide were performed using ELISA. The antimicrobial activity was studied against the Gram-negative Escherichia coli (ATCC 25,922) and Klebsiella pneumoniae (ATCC 700,603). The inflammatory response of the total soluble proteins of transplastomic N. oculata was assessed by measuring secretion of the cytokines IL-6, IL-10, and alpha-tumor necrosis (TNF-α), and cytotoxicity was assessed. These results provide a potential strategy to produce the Flo peptide in microalgae with antibacterial activities.

Scope and Limitations of Exploiting the Ability of the Chemosensitizer NV716 to Enhance the Activity of Tetracycline Derivatives against Pseudomonas aeruginosa

The spread of antibiotic resistance is an urgent threat to global health that requires new therapeutic approaches. Treatments for pathogenic Gram-negative bacteria are particularly challenging to identify due to the robust OM permeability barrier in these organisms. One strategy is to use antibiotic adjuvants, a class of drugs that have no significant antibacterial activity on their own but can act synergistically with certain antibiotics. Previous studies described the discovery and development of polyaminoisoprenyl molecules as antibiotic adjuvants with an OM effect. In particular, the compound NV716 has been shown to sensitize Pseudomonas aeruginosa to tetracycline antibiotics such as doxycycline. Here, we sought to explore the disruption of OM to sensitize P. aeruginosa to otherwise inactive antimicrobials using a series of tetracycline derivatives in the presence of NV716. We found that OM disruption expands the hydrophobicity threshold consistent with antibacterial activity to include hydrophobic molecules, thereby altering permeation rules in Gram-negative bacteria.

In vitro activities of omadacycline, eravacycline, cefiderocol, apramycin, and comparator antibiotics against Acinetobacter baumannii causing bloodstream infections in Greece, 2020-2021: a multicenter study

Resistance of Acinetobacter baumannii to multiple clinically important antimicrobials has increased to very high rates in Greece, rendering most of them obsolete. The aim of this study was to determine the molecular epidemiology and susceptibilities of A. baumannii isolates collected from different hospitals across Greece. Single-patient A. baumannii strains isolated from blood cultures (n = 271), from 19 hospitals, in a 6-month period (November 2020-April 2021) were subjected to minimum inhibitory concentration determination and molecular testing for carbapenemase, 16S rRNA methyltransferase and mcr gene detection and epidemiological evaluation. 98.9% of all isolates produced carbapenemase OXA-23. The vast majority (91.8%) of OXA-23 producers harbored the armA and were assigned mainly (94.3%) to sequence group G1, corresponding to IC II. Apramycin (EBL-1003) was the most active agent inhibiting 100% of the isolates at ≤16 mg/L, followed by cefiderocol which was active against at least 86% of them. Minocycline, colistin and ampicillin-sulbactam exhibited only sparse activity (S <19%), while eravacycline was 8- and 2-fold more active than minocycline and tigecycline respectively, by comparison of their MIC₅₀/₉₀ values. OXA-23-ArmA producing A. baumannii of international clone II appears to be the prevailing epidemiological type of this organism in Greece. Cefiderocol could provide a useful alternative for difficult to treat Gram-negative infections, while apramycin (EBL-1003), the structurally unique aminoglycoside currently in clinical development, may represent a highly promising agent against multi-drug resistant A. baumanni infections, due to its high susceptibility rates and low toxicity.

Flexible free-standing antibacterial nanoporous Ag ribbon

The biomedical field has the potential to significantly benefit from the use of flexible free-standing Ag nanostructures due to their outstanding mechanical and antibacterial properties. However, the intricate process of synthesizing these nanostructures, as well as the potential toxicity of nanostructured Ag, pose significant challenges. This study used a facile etching method to synthesize the free-standing nanoporous Ag (NP-Ag) ribbons with a homogeneous and bicontinuous three-dimensional ligament structure. The free-standing NP-Ag ribbons demonstrated stable mechanical performance and excellent flexibility when subjected to various deformation states on artificial fingers. Additionally, the NP-Ag ribbons exhibited remarkable antibacterial capacity with rates of 99.81 ± 0.14% against Escherichia coli, 96.11 ± 1.49% against Staphylococcus aureus, and 95.37 ± 1.24% against methicillin-resistant Staphylococcus aureus. The antibacterial mechanism of NP-Ag is attributed to the rapid release of Ag ions (Ag⁺) in 24 h, causing damage to the bacterial membrane. Moreover, the in vivo results demonstrate that the NP-Ag ribbons provide rapid antibacterial efficacy and are biosafe due to the long-term stable Ag⁺ release of NP-Ag. The development of these free-standing flexible NP-Ag ribbons offers a new avenue for wearable antibacterial applications.

The Lytic Activity of Bacteriophage ZCSE9 against Salmonella enterica and Its Synergistic Effects with Kanamycin

Salmonella, the causative agent of several diseases in humans and animals, including salmonellosis, septicemia, typhoid fever, and fowl typhoid, poses a serious threat to global public health and food safety. Globally, reports of therapeutic failures are increasing because of the increase in bacterial antibiotic resistance. Thus, this work highlights the combined phage–antibiotic therapy as a promising approach to combating bacterial resistance. In this manner, the phage ZCSE9 was isolated, and the morphology, host infectivity, killing curve, combination with kanamycin, and genome analysis of this phage were all examined. Morphologically, phage ZCSE9 is a siphovirus with a relatively broad host range. In addition, the phage can tolerate high temperatures until 80 °C with one log reduction and a basic environment (pH 11) without a significant decline. Furthermore, the phage prevents bacterial growth in the planktonic state, according to the results of the time-killing curve. Moreover, using the phage at MOI 0.1 with kanamycin against five different Salmonella serotypes reduces the required antibiotics to inhibit the growth of the bacteria. Comparative genomics and phylogenetic analysis suggested that phage ZCSE9, along with its close relatives Salmonella phages vB_SenS_AG11 and wksl3, belongs to the genus Jerseyvirus. In conclusion, phage ZCSE9 and kanamycin form a robust heterologous antibacterial combination that enhances the effectiveness of a phage-only approach for combating Salmonella.

Visible-UVC upconversion polymer films for prevention of microbial infection

Bacterial infections caused by the growth and reproduction of pathogenic bacteria on wounds are one of the main reasons that hinder wound healing. Antibacterial wound dressings protect wounds from bacterial infections. Herein, we developed a polymeric antibacterial composite film using polyvinyl alcohol (PVA) and sodium alginate (SA) as the substrate. The film used praseodymium-doped yttrium orthosilicate (Y₂SiO₅: Pr³⁺, YSO-Pr) to convert visible light into short-wavelength ultraviolet light (UVC) to kill bacteria. The YSO-Pr/PVA/SA showed upconversion luminescence in photoluminescence spectrometry tests, and the emitted UVC inhibited Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria in antibacterial tests. In vivo animal tests showed that YSO-Pr/PVA/SA is effective and safe for inhibiting bacteria in real wounds. The in vitro cytotoxicity test further confirmed the good biocompatibility of the antibacterial film. In addition, YSO-Pr/PVA/SA exhibited sufficient tensile strength. Overall, this study demonstrates the potential of upconversion materials for use in medical dressings.

WO3 Nanowire-Attached Reduced Graphene Oxide-Based 1D-2D Heterostructures for Near-Infrared Light-Driven Synergistic Photocatalytic and Photothermal Inactivation of Multidrug-Resistant Superbugs

The rapid emergence of superbugs which are resistant to existing antibiotics is becoming a huge global threat to public health, which demands the discovery of next-generation antibacterial agents for combating superbugs. Herein, we report the design of a two-dimensional (2D) reduced graphene oxide (r-GO) and one-dimensional (1D) WO₃ nanowire-based photothermal-photocatalytic heterostructure for combating multiantibiotic-resistant Salmonella DT104, carbapenem-resistant Enterobacteriaceae Escherichia coli, and methicillin-resistant Staphylococcus aureus superbugs. In the presence of near-infrared (NIR) light, due to the generation of electrons and holes, the WO₃-based heterostructure generates reactive oxygen species by photocatalytic reaction from water and oxygen, which kills superbugs. To enhance the photocatalytic superbug killing efficiency, r-GO has been used for suppressing the recombination of the photoinduced electron-hole pairs. Reported data show that NIR light-driven synergistic photocatalytic-photothermal processes can be used for 100% degradation of methylene blue using a heterostructure-based catalyst, and the photodegradation rate for the heterostructure is much better than the literature data for different types of WO₃/GO-based nanocomposites. Experimentally, time-dependent antibacterial efficiency data reveals that the heterostructure can destroy 100% superbugs within 30 min of light exposure via a synergistic photothermal and photocatalytic mechanism, whereas the WO₃ nanowire can kill around 35% superbugs only via photocatalytic action only and r-GO can kill 25% superbugs via photothermal action even after 30 min of exposure to light. Systematic time-dependent microscopy and spectroscopy studies reveal that the excellent antisuperbug activities for heterostructures are due to membrane damage, ATP, and DNA/RNA breakage. For possible real-life applications, sun light-based superbug inactivation shows 100% inactivation possible within 250 min of light exposure using 12 mg/mL heterostructures. The reported sun light-driven killing of superbugs provides a simple and versatile platform to combat drug-resistant superbugs.

Performance of Ceftazidime-Avibactam 30/20-μg and 10/4-μg Disks for Susceptibility Testing of Enterobacterales and Pseudomonas aeruginosa

Ceftazidime-avibactam, a new β-lactam-β-lactamase inhibitor combination, is active against multidrug-resistant Enterobacterales and Pseudomonas aeruginosa isolates and has became available for clinical use in China in the latter half of 2019. In this study, we evaluated the performance of the disk diffusion test with ceftazidime-avibactam 10/4-μg and 30/20-μg disks, compared with the reference broth microdilution method, with a collection of 467 Enterobacterales and 182 P. aeruginosa nonduplicate clinical isolates. The results of antimicrobial susceptibility testing indicated that the categorical agreement (CA) of ceftazidime-avibactam 10/4-μg disk testing for all tested Enterobacterales isolates was 99.8%, with 0.5% very major errors (VMEs) and no major error (ME). The CA of ceftazidime-avibactam 10/4-μg disk testing for all tested P. aeruginosa isolates was 87.9%, with 15.5% MEs and no VME. The CA of ceftazidime-avibactam 30/20-μg disk testing for all tested Enterobacterales isolates was 99.4%, with 1.5% VMEs and no ME. The CA of ceftazidime-avibactam 30/20-μg disk testing for all tested P. aeruginosa isolates was 91.8%, with 2.5% VMEs and 9.9% MEs. Overall, ceftazidime-avibactam 10/4-μg disk testing showed superior performance and was more suitable for assessment of the susceptibility of Enterobacterales and P. aeruginosa isolates. IMPORTANCE Multidrug-resistant Enterobacterales and P. aeruginosa strains have become a global public threat, with the emergence and prevalence of plasmid-mediated extended-spectrum β-lactamases (ESBLs), AmpC cephalosporinases, and carbapenemases disseminated worldwide. Ceftazidime-avibactam, which is commercially available, has shown excellent in vitro activity against multidrug-resistant and carbapenem-resistant Enterobacterales and P. aeruginosa isolates. Moreover, ceftazidime-avibactam has shown promise in treating infections caused by multidrug-resistant and carbapenem-resistant isolates. The disk diffusion test for ceftazidime-avibactam is the most common antimicrobial susceptibility testing method in most laboratories in China. The accurate detection of ceftazidime-avibactam susceptibility is of great significance for the rational clinical application of drugs. Here, we evaluated the performance of the ceftazidime-avibactam 10/4-μg and 30/20-μg disk diffusion tests, compared with the reference broth microdilution method, with clinical Enterobacterales and P. aeruginosa isolates.

Geographic patterns of Acinetobacter baumannii and carbapenem resistance in the Asia-Pacific Region: results from the Antimicrobial Testing Leadership and Surveillance (ATLAS) program, 2012-2019

OBJECTIVES

This study aimed to investigate the geographic distribution of carbapenem-resistant Acinetobacter baumannii (CR-AB) isolates in the Asia-Pacific region.

METHODS

We collected A. baumannii isolates using the Antimicrobial Testing Leadership and Surveillance program from 2012 to 2019. The minimum inhibitory concentrations (MICs) of the isolates were determined using the broth microdilution method. The major carbapenemase genes were identified using multiplex polymerase chain reaction assays for the isolates collected between 2012 and 2014. CR-AB was defined as isolates with meropenem MICs ≥8 mg/l.

RESULTS

In total, 2674 A. baumannii isolates were collected from 13 countries, of which 1918 (71.7%) were CR-AB. The carbapenem resistance rates among A. baumannii isolates were as low as 2.8% and 6.5% in Japan and Australia, respectively, but as high as 88% and 87.2% in South Korea and India, respectively. Of the 232 CR-AB isolates that underwent carbapenemase gene screening, 224 (96.6%) harbored at least one carbapenemase gene. A total of 226 carbapenemase genes were detected, with bla_OXA-23 (94.7%, 214/226) being the most dominant, followed by bla_OXA-72 (2.7%, 6/226), bla_OXA-58 (2.2%, 5/226), and bla_NDM-1 (0.4%, 1/226). CR-AB isolates had >80% resistance to amikacin, ampicillin/sulbactam, cefepime, ceftazidime, ciprofloxacin, levofloxacin, and piperacillin/tazobactam. The rates of CR-AB resistance to minocycline and colistin were 7.2% (31/429) and 1.7% (23/1368). For cefoperazone/sulbactam and tigecycline, 50.2% (527/1049) and 93.3% (1789/1918) of CR-AB isolates had an MIC ≤16 mg/l and ≤2 mg/l, respectively.

CONCLUSION

The prevalence of carbapenem resistance in A. baumannii showed significant differences among countries in the Asia-Pacific region, and the treatment options were limited.

Gold(I) selenium N-heterocyclic carbene complexes as potent antibacterial agents against multidrug-resistant gram-negative bacteria via inhibiting thioredoxin reductase

Multidrug-resistant (MDR) Gram-negative bacteria have become a global threat to human life and health, and novel antibiotics are urgently needed. The thioredoxin (Trx) system can be used as an antibacterial target to combat MDR bacteria. Here, we found that two active gold(I) selenium N-heterocyclic carbene complexes H7 and H8 show more promising antibacterial effects against MDR bacteria than auranofin. Both H7 and H8 irreversibly inhibit the bacterial TrxR activity via targeting the redox-active motif, abolishing the capacity of TrxR to quench reactive oxygen species (ROS) and finally leading to oxidative stress. The increased cellular superoxide radical levels impact a variety of functions necessary for bacterial survival, such as cellular redox balance, cell membrane integrity, amino acid metabolism, and lipid peroxidation. In vivo data present much better antibacterial activity of H7 and H8 than auranofin, promoting the wound healing and prolonging the survival time of Carbapenem-resistant Acinetobacter baumannii (CRAB) induced peritonitis. Most notably in this study, we revealed the influence of gold(I) complexes on both the Trx system and the cellular metabolic states to better understand their killing mechanism and to support further antibacterial drug design.