Tailored liposomal nanotraps for the treatment of Streptococcal infections

Nanomaterial-based drug delivery systems in overcoming bacterial resistance: Current review

Antimicrobial resistance is one of the most serious contemporary global health concerns, threatening the effectiveness of existing antibiotics and resulting in morbidity, mortality, and economic burdens. This review examines the contribution of nanomaterial-based drug delivery systems to solving the problems associated with bacterial resistance and provides a thorough overview of their mechanisms of action, efficiency, and perspectives for the future. Owing to their unique physicochemical properties, nanomaterials reveal new ways of passing through the traditional mechanisms of bacterial defence connected to the permeability barrier of membranes, efflux pumps, and biofilm formation. This review addresses the different types of nanomaterials, including metallic nanoparticles, liposomes, and polymeric nanoparticles, in terms of their antimicrobial properties and modes of action. More emphasis has been placed on the critical discussion of recent studies on such active systems. Both in vitro and in vivo models are discussed, with particular attention paid to multidrug-resistant bacteria. This review begins by reviewing the urgency for antimicrobial resistance (AMR) by citing recent statistics, which indicate that the number of deaths and reasons for financial losses continue to increase. A background is then provided on the limitations of existing antibiotic therapies and the pressing need to develop innovative approaches. Nanomaterial-based drug delivery systems have been proposed as promising solutions because of their potential to improve drug solubility, stability, and targeted delivery, although side effects can also be mitigated. In addition to established knowledge, this review also covers ongoing debates on the continuous risks associated with the use of nanomaterials, such as toxicity and environmental impact. This discussion emphasizes the optimization of nanomaterial design to target specific bacteria, and rigorous clinical trials to establish safety and efficacy in humans. It concludes with reflections on the future directions of nanomaterial-based drug delivery systems in fighting AMR, underlining the need for an interdisciplinary approach, along with continuous research efforts to translate these promising technologies into clinical practice. As the fight against bacterial resistance reaches its peak, nanomaterials may be the key to developing next-generation antimicrobial therapies.

Pneumolysin-responsive liposomal platform for selective treatment of Streptococcus pneumoniae

The bacterium Streptococcus pneumoniae has become a leading cause of meningitis, sepsis, and bacterial pneumonia worldwide, with increased prevalence of antibiotic-resistant serotypes serving to exacerbate the issue. The main factor responsible for colonization and immune response escape in pneumococcal infections is the secreted molecule pneumolysin, which is a subset within a family of related toxins that form transmembrane pores in biological membranes through cholesterol recognition and binding. The conserved activity and structure of pneumolysin between all observed S. pneumoniae serotypes, along with its requirement for pathogenicity, has made this molecule an attractive target for vaccination, diagnostic, and sequestration platforms, but not yet as a facilitative agent for therapeutic treatment. Consequently, the present work aimed to examine the impact of liposomal cholesterol content for pneumolysin-induced release of the encapsulated antimicrobial peptide nisin. It was determined that a cholesterol content above 45 mol% was necessary to facilitate interactions with both purified pneumolysin toxin and S. pneumoniae culture, demonstrated through enhanced nisin release and a reduction in hemolytic rates upon exposure of the toxin with cholesterol-rich vesicles. Antibacterial testing highlighted the ability of the developed platform to elicit a potent and specific bactericidal response in vitro against cultured S. pneumoniae when compared to a control strain, Staphylococcus epidermidis. It further improved viability of a fibroblast cell line upon S. pneumoniae challenge, outperforming free nisin via the synergistic impact of simultaneous bacterial clearance and pneumolysin neutralization. These findings collectively indicate that cholesterol-rich liposomes hold promise as a selective treatment platform against pneumococcal infections.

Cholesterol dependent cytolysins and the brain: Revealing a potential therapeutic avenue for bacterial meningitis

Bacterial meningitis is a catastrophic nervous system disorder with high mortality and wide range of morbidities. Some of the meningitis-causing bacteria occupy cholesterol dependent cytolysins (CDCs) to increase their pathogenicity and arrange immune-evasion strategy. Studies have observed that the relationship between CDCs and pathogenicity in these meningitides is complex and involves interactions between CDC, blood-brain barrier (BBB), glial cells and neurons. In BBB, these CDCs acts on capillary endothelium, tight junction (TJ) proteins and neurovascular unit (NVU). CDCs also observed to elicit intriguing effects on brain inflammation which involves microglia and astrocyte activations, along with neuronal damage as the end-point of pathological pathways in bacterial meningitis. As some studies mentioned potential advantage of CDC-targeted therapeutic mechanisms to combat CNS infections, it might be a fruitful avenue to deepen our understanding of CDC as a candidate for adjuvant therapy to combat bacterial meningitis.

Engineered Liposomes Protect Immortalized Immune Cells from Cytolysins Secreted by Group A and Group G Streptococci

The increasing antibiotic resistance of bacterial pathogens fosters the development of alternative, non-antibiotic treatments. Antivirulence therapy, which is neither bacteriostatic nor bactericidal, acts by depriving bacterial pathogens of their virulence factors. To establish a successful infection, many bacterial pathogens secrete exotoxins/cytolysins that perforate the host cell plasma membrane. Recently developed liposomal nanotraps, mimicking the outer layer of the targeted cell membranes, serve as decoys for exotoxins, thus diverting them from attacking host cells. In this study, we develop a liposomal nanotrap formulation that is capable of protecting immortalized immune cells from the whole palette of cytolysins secreted by Streptococcus pyogenes and Streptococcus dysgalactiae subsp. equisimilis—important human pathogens that can cause life-threatening bacteremia. We show that the mixture of cholesterol-containing liposomes with liposomes composed exclusively of phospholipids is protective against the combined action of all streptococcal exotoxins. Our findings pave the way for further development of liposomal antivirulence therapy in order to provide more efficient treatment of bacterial infections, including those caused by antibiotic resistant pathogens.