Why new antibiotics are not obviously useful now

Enrofloxacin‑silver composite nano-emulsion as a scalable synergetic antibacterial platform for accelerating infected wound healing

The colonization of bacterial pathogens is a major concern in wound infection and becoming a notable medical issue. Enrofloxacin (ENR) can be applied to treat skin infections, while poor water solubility and bioavailability limit its clinical application. Nanostructured lipid carriers (NLCs) enhance the solubility and bioavailability of drugs by encapsulating them, making them effective for the topical treatment of skin wound infections. Additionally, to enhance treatment efficacy and further improve wound healing, silver nanoparticles (AgNPs) were attached to the aforementioned matrix, which also improved its colloidal stability and reduced toxicity. Herein, a scalable poly (vinyl alcohol) modified NLCs-based antibacterial platform was fabricated by high-pressure homogenization method, to co-load ENR and AgNPs for treating the bacterial-infected wounds. The growth of common wound bacterial pathogens (Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa) was synergistically inhibited by released ENR and Ag+ from the poly (vinyl alcohol) modified enrofloxacin‑silver composite nano-emulsion (ENR@PVA-NLCs/AgNPs). In the in vivo wound model, the Staphylococcus aureus-infected wound in rat almost completely disappeared after treatment with ENR@PVA-NLCs/AgNPs, and no suppuration symptom was observed. Importantly, this nanoplatform had negligible side effects in vivo. Taken together, the above results strongly demonstrate the promising potential of ENR@PVA-NLCs/AgNPs as a synergistic therapeutic agent for clinical wound infections.

Multifunctional SEBS/AgNWs Nanocomposite Films with Antimicrobial, Antioxidant, and Anti-Inflammatory Properties Promote Infected Wound Healing

Wound healing is a complex biological process that can trigger inflammation and oxidative stress and impair myofibrillogenesis and angiogenesis. Several advanced wound-dressing nanocomposite materials have been designed to address these issues. Here, we designed a new multifunctional styrene-ethylene-butylene-styrene/silver nanowire (SEBS/AgNWs)-based nanocomposite film with antimicrobial, antioxidant, and anti-inflammatory properties to promote wound healing. The porous morphological structure of SEBS/AgNWs enhances their antimicrobial, antioxidant, and anti-inflammatory properties. SEBS/AgNWs significantly inhibited the growth of Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, and Escherichia coli strains, effectively wiping out ABTS•+, DPPH•, hydrogen peroxide (H2O2), and hydroxyl (•OH) radicals, showing their effective ROS-scavenging properties. It further showed significant antioxidant properties by increasing the levels of enzyme-like catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH), while decreasing malonaldehyde (MDA) levels. Additionally, SEBS/AgNWs reduced the expression of interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α), while increasing levels of transforming growth factor- β (TGF-β), vascular endothelial growth factor-A (VEGF), and CD31 in wound healing. This suggests that applying a multifunctional nanoplatform based on SEBS/AgNWs could enhance wound healing and improve patient outcomes in wound care management.

Antibacterial and cytotoxic potency of thermophilic Streptomyces werraensis MI-S.24-3 isolated from an Egyptian extreme environment

The need for novel and active antibiotics specially from actinomycetes is essential due to new and drug-resistant pathogens. In this study, 87 actinomycetes were isolated, and 18 strains among them characterized as thermophilic actinomycetes. Further fractionation and preliminary antibacterial activities indicated that one strain, coded as MI-S.24-3, showed good antibacterial activity. Based on the phenotypic, genomic, phylogenetic, and biochemical analyses, MI-S.24-3 was identified as Streptomyces werraensis. Results demonstrated that the ethyl acetate active fraction showed maximum antibacterial activity against Staphylococcus aureus and Escherichia coli with MIC (12.7 ± 0.1 and 18.3 ± 0.2 mg/mL), and MBC (96.5 ± 1.4 and 91.5 ± 0.7 mg/mL), respectively, with determination of time kill kinetics assay. The active fraction showed moderate-to-weak cytotoxic effects against human lung carcinoma (A549 cells), breast cancer cell line (MCF-7), and human cervical carcinoma (HELA cells) with a IC₅₀ of (23.8 ± 1.2, 54 ± 1.8, 96.4 ± 3.2 μg/mL, respectively). Active components were characterised by different chemically volatile, ester, and lactone compounds, determined by GC-MS coupled with daughter ions of (GC-MS/MS). Notably, erucic acid and reynosin identified compounds are rare metabolites produced by Streptomyces werraensis. Our findings demonstrated that the MI-S.24-3 strain could be a potential source for active compounds of biomedical and pharmaceutical interest.

The Persister Character of Clinical Isolates of Staphylococcus aureus Contributes to Faster Evolution to Resistance and Higher Survival in THP-1 Monocytes: A Study With Moxifloxacin

Staphylococcus aureus may cause relapsing infections. We previously showed that S. aureus SH1000 surviving intracellularly to bactericidal antibiotics are persisters. Here, we used 54 non-duplicate clinical isolates to assess links between persistence, resistance evolution, and intracellular survival, using moxifloxacin throughout as test bactericidal antibiotic. The relative persister fraction (RPF: percentage of inoculum surviving to 100× MIC moxifloxacin in stationary phase culture for each isolate relative to ATCC 25923) was determined to categorize isolates with low (≤10) or high (>10) RPF. Evolution to resistance (moxifloxacin MIC ≥ 0.5 mg/L) was triggered by serial passages at 0.5× MIC (with daily concentration readjustments). Intracellular moxifloxacin maximal efficacy (E_max) was determined by 24 h concentration-response experiments [pharmacodynamic model (Hill-Langmuir)] with infected THP-1 monocytes exposed to moxifloxacin (0.01 to 100× MIC) after phagocytosis. Division of intracellular survivors was followed by green fluorescence protein dilution (FACS). Most (30/36) moxifloxacin-susceptible isolates showed low RPF but all moxifloxacin-resistant (n = 18) isolates harbored high RPF. Evolution to resistance of susceptible isolates was faster for those with high vs. low RPF (with SOS response and topoisomerase-encoding genes overexpression). Intracellularly, moxifloxacin E_max was decreased (less negative) for isolates with high vs. low RPF, independently from resistance. Moxifloxacin intracellular survivors were non-dividing. The data demonstrate and quantitate persisters in clinical isolates of S. aureus, and show that this phenotype accelerates resistance evolution and is associated with intracellular survival in spite of high antibiotic concentrations. Isolates with high RPF may represent a possible cause of treatment failure not directly related to resistance in patients receiving active antibiotics.

Culturing the human microbiota and culturomics

The gut microbiota has an important role in the maintenance of human health and in disease pathogenesis. This importance was realized through the advent of omics technologies and their application to improve our knowledge of the gut microbial ecosystem. In particular, the use of metagenomics has revealed the diversity of the gut microbiota, but it has also highlighted that the majority of bacteria in the gut remain uncultured. Culturomics was developed to culture and identify unknown bacteria that inhabit the human gut as a part of the rebirth of culture techniques in microbiology. Consisting of multiple culture conditions combined with the rapid identification of bacteria, the culturomic approach has enabled the culture of hundreds of new microorganisms that are associated with humans, providing exciting new perspectives on host-bacteria relationships. In this Review, we discuss why and how culturomics was developed. We describe how culturomics has extended our understanding of bacterial diversity and then explore how culturomics can be applied to the study of the human microbiota and the potential implications for human health.

An Update on Clinical Burden, Diagnostic Tools, and Therapeutic Options of Staphylococcus aureus

Staphylococcus aureus is an important pathogen responsible for a variety of diseases ranging from mild skin and soft tissue infections, food poisoning to highly serious diseases such as osteomyelitis, endocarditis, and toxic shock syndrome. Proper diagnosis of pathogen and virulence factors is important for providing timely intervention in the therapy. Owing to the invasive nature of infections and the limited treatment options due to rampant spread of antibiotic-resistant strains, the trend for development of vaccines and antibody therapy is increasing at rapid rate than development of new antibiotics. In this article, we have discussed elaborately about the host-pathogen interactions, clinical burden due to S aureus infections, status of diagnostic tools, and treatment options in terms of prophylaxis and therapy.