Mitoxantrone targets both host and bacteria to overcome vancomycin resistance in Enterococcus faecalis

Light-activated nanoclusters with tunable ROS for wound infection treatment

Infected wounds pose a significant clinical challenge due to bacterial resistance, recurrent infections, and impaired healing. Reactive oxygen species (ROS)-based strategies have shown promise in eradicating bacterial infections. However, the excess ROS in the infection site after treatments may cause irreversible damage to healthy tissues. To address this issue, we developed bovine serum albumin-iridium oxide nanoclusters (BSA-IrOx NCs) which enable photo-regulated ROS generation and scavenging using near infrared (NIR) laser. Upon NIR laser irradiation, BSA-IrOx NCs exhibit enhanced photodynamic therapy, destroying biofilms and killing bacteria. When the NIR laser is off, the nanoclusters' antioxidant enzyme-like activities prevent inflammation and repair damaged tissue through ROS clearance. Transcriptomic and metabolomic analyses revealed that BSA-IrOx NCs inhibit bacterial nitric oxide synthase, blocking bacterial growth and biofilm formation. Furthermore, the nanoclusters repair impaired skin by strengthening cell junctions and reducing mitochondrial damage in a fibroblast model. In vivo studies using rat infected wound models confirmed the efficacy of BSA-IrOx NCs. This study presents a promising strategy for treating biofilm-induced infected wounds by regulating the ROS microenvironment, addressing the challenges associated with current ROS-based antibacterial approaches.

Bosutinib Stimulates Macrophage Survival, Phagocytosis, and Intracellular Killing of Bacteria

Host-acting compounds are emerging as potential alternatives to combating antibiotic resistance. Here, we show that bosutinib, an FDA-approved chemotherapeutic for treating chronic myelogenous leukemia, does not possess any antibiotic activity but enhances macrophage responses to bacterial infection. In vitro, bosutinib stimulates murine and human macrophages to kill bacteria more effectively. In a murine wound infection with vancomycin-resistant Enterococcus faecalis, a single intraperitoneal bosutinib injection or multiple topical applications on the wound reduce the bacterial load by approximately 10-fold, which is abolished by macrophage depletion. Mechanistically, bosutinib stimulates macrophage phagocytosis of bacteria by upregulating surface expression of bacterial uptake markers Dectin-1 and CD14 and promoting actin remodeling. Bosutinib also stimulates bacterial killing by elevating the intracellular levels of reactive oxygen species. Moreover, bosutinib drives NF-κB activation, which protects infected macrophages from dying. Other Src kinase inhibitors such as DMAT and tirbanibulin also upregulate expression of bacterial uptake markers in macrophages and enhance intracellular bacterial killing. Finally, cotreatment with bosutinib and mitoxantrone, another chemotherapeutic in clinical use, results in an additive effect on bacterial clearance in vitro and in vivo. These results show that bosutinib stimulates macrophage clearance of bacterial infections through multiple mechanisms and could be used to boost the host innate immunity to combat drug-resistant bacterial infections.

Antibiotic resistance: a global crisis, problems and solutions

Healthy state is priority in today's world which can be achieved using effective medicines. But due to overuse and misuse of antibiotics, a menace of resistance has increased in pathogenic microbes. World Health Organization (WHO) has announced ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) as the top priority pathogens as these have developed resistance against certain antibiotics. To combat such a global issue, it is utmost important to identify novel therapeutic strategies/agents as an alternate to such antibiotics. To name certain antibiotic adjuvants including: inhibitors of beta-lactamase, efflux pumps and permeabilizers for outer membrane can potentially solve the antibiotic resistance problems. In this regard, inhibitors of lytic domain of lytic transglycosylases provide a novel way to not only act as an alternate to antibiotics but also capable of restoring the efficiency of previously resistant antibiotics. Further, use of bacteriophages is another promising strategy to deal with antibiotic resistant pathogens. Taking in consideration the alternatives of antibiotics, a green synthesis nanoparticle-based therapy exemplifies a good option to combat microbial resistance. As horizontal gene transfer (HGT) in bacteria facilitates the evolution of new resistance strains, therefore identifying the mechanism of resistance and development of inhibitors against it can be a novel approach to combat such problems. In our perspective, host-directed therapy (HDT) represents another promising strategy in combating antimicrobial resistance (AMR). This approach involves targeting specific factors within host cells that pathogens rely on for their survival, either through replication or persistence. As many new drugs are under clinical trials it is advisable that more clinical data and antimicrobial stewardship programs should be conducted to fully assess the clinical efficacy and safety of new therapeutic agents.

Characterization of microbial contamination in agricultural soil: A public health perspective

Soil is widely recognized as a reservoir of microbial contaminants including antibiotic resistance genes (ARGs) and human bacterial pathogens (HBPs), which are major public health concerns. Although the risks associated with soil safety in different soil habitats have been studied, the results are not comprehensive. In this study, dryland soils used for vegetable, corn, and soybean planting, and submerged soils used for rice planting and crab farming were collected and subjected to metagenomic sequencing to characterize HBPs, ARGs, and virulence factor genes (VFGs). The results showed that submerged soils had a higher abundance of HBP than dryland soils. In addition, the submerged soil microbiome acquired significantly higher levels of high-risk ARGs than the dryland soil microbiome and these ARGs were mainly assigned to bacA, sul1, and aadA genes submerged. Network analysis revealed that 11 HBPs, including Yersinia enterocolitica, Vibrio cholerae, Escherichia coli, and Leptospira interrogans, were high-risk because of their close association with ARGs, VFGs, and mobile genetic elements (MGEs). Procrustes and network analyses showed that HBPs and ARGs were more closely linked in submerged soil. This study confirms that submerged field has higher ecological environment risk and human health risk than dryland soil.

Repurposing Anthracycline Drugs as Potential Antibiotic Candidates and Potentiators to Tackle Multidrug-Resistant Pathogens

The escalating mortality rate resulting from multidrug-resistant (MDR) bacteria has intensified the urgency for innovative antimicrobial agents. Currently, the antimicrobial activity of compounds is usually assessed by testing the minimum inhibitory concentration (MIC) on a standardized laboratory medium. However, such screening conditions differ from the in vivo environment, making it easy to overlook some antibacterial agents that are active in vivo but less active in vitro. Herein, by using tissue medium RPMI, we uncover that anthracyclines, especially mitoxantrone (MX), exhibit improved bacteriostatic and bactericidal effects against various MDR bacteria in host-like media. Transcriptome results reveal that LPS modification-related genes of bacterial membrane surfaces and metabolic genes are significantly down-regulated in RPMI media. Mechanistic studies demonstrate that MX leads to more substantial membrane damage, increased ROS production, and DNA damage in host-mimicking conditions. Furthermore, we demonstrate that MX and colistin exhibit strong synergistic effects against mcr-positive strains in host-mimicking media by disrupting iron homeostasis. In an experimental murine infection model, MX monotreatment demonstrates therapeutic efficacy in reducing bacterial burdens. Overall, our work suggests that mimicking the host condition is an effective strategy to identify new antimicrobial agents and highlights the therapeutic potential of anthracycline drugs in combating MDR pathogens.

Enterococci facilitate polymicrobial infections

Enterococci are ubiquitous members of the gut microbiota in human beings and animals and are among the most important nosocomial organisms. Due to their opportunistic pathogenicity, enterococci are referred to as pathobionts and play decisive roles in a diverse array of polymicrobial infections. Enterococci can promote the colonization, pathogenesis, and persistence of various pathogens, compromise the efficacy of drugs, and pose a severe threat to public health. Most current treatments tend to focus on the sole pathogenic bacteria, with insufficient attention to the driving role of enterococci. In this review, we summarize the characteristics of enterococci in infections, the factors facilitating their outgrowth, as well as the sites and types of enterococci-associated polymicrobial infections. We present an overview of the underlying mechanisms of enterococci-mediated pathogenesis in polymicrobial infections. Furthermore, we discuss alternative strategies and potential intervention approaches to restrict such infections, shedding light on the discovery and development of new therapies against polymicrobial infections.

In Silico and In Vitro Identification of 1,8-Dihydroxy-4,5-dinitroanthraquinone as a New Antibacterial Agent against Staphylococcus aureus and Enterococcus faecalis

Increasing rates of bacterial resistance to antibiotics are a growing concern worldwide. The search for potential new antibiotics has included several natural products such as anthraquinones. However, comparatively less attention has been given to anthraquinones that exhibit functional groups that are uncommon in nature. In this work, 114 anthraquinones were evaluated using in silico methods to identify inhibitors of the enzyme phosphopantetheine adenylyltransferase (PPAT) of Staphylococcus aureus, Enterococcus faecalis, and Escherichia coli. Virtual screenings based on molecular docking and the pharmacophore model, molecular dynamics simulations, and free energy calculations pointed to 1,8-dihydroxy-4,5-dinitroanthraquinone (DHDNA) as the most promising inhibitor. In addition, these analyses highlighted the contribution of the nitro group to the affinity of this anthraquinone for the nucleotide-binding site of PPAT. Furthermore, DHDNA was active in vitro towards Gram-positive bacteria with minimum inhibitory concentration (MIC) values of 31.25 µg/mL for S. aureus and 62.5 µg/mL for E. faecalis against both antibiotic-resistant isolates and reference strains but was ineffective against E. coli. Experiments on kill-time kinetics indicated that, at the tested concentrations, DHDNA produced bacteriostatic effects on both Gram-positive bacteria. Overall, our results present DHDNA as a potential PPAT inhibitor, showing antibacterial activity against antibiotic-resistant isolates of S. aureus and E. faecalis, findings that point to nitro groups as key to explaining these results.