Combinational therapy with antibiotics and antibiotic-loaded adipose-derived stem cells reduce abscess formation in implant-related infection in rats

Prevention and potential remedies for antibiotic resistance: current research and future prospects

The increasing threat of antibiotic resistance and shrinking treatment options for infections have pushed mankind into a difficult position. The looming threat of the return of the pre-antibiotic era has caused a sense of urgency to protect and conserve the potency of antibiotic therapy. One of the perverse effects of antibiotic resistance is the dissemination of its causative agents from non-clinically important strains to clinically important strains and vice versa. The popular saying "Prevention is better than cure" is appropriate for tackling antibiotic resistance. On the one hand, new and effective antibiotics are required; on the other hand, better measures for the use of antibiotics, along with increased awareness in the general public related to antibiotic use, are essential. Awareness, especially of appropriate antibiotic use, antibiotic resistance, its dissemination, and potential threats, can help greatly in controlling the use and abuse of antibiotics, and the containment of antibiotic resistance. Antibiotic drugs' effectiveness can be enhanced by producing novel antibiotic analogs or adding adjuvants to current antibiotics. Combinatorial therapy of antibiotics has proven successful in treating multidrug-resistant (MDR) bacterial infections. This review aims to highlight the current global situation of antibiotic resistance and discuss the methods used to monitor, prevent, inhibit, or reverse bacterial resistance mechanisms in the fight against antibiotic resistance.

Adipose-derived stem cells and antibiotics: A novel synergistic approach for treating implant-related osteomyelitis

Implant-related osteomyelitis poses a significant challenge in orthopedic practice, particularly due to the increasing prevalence of antibiotic-resistant infections and biofilm-associated complications. This article focused on exploring the potential of combination therapy with adipose-derived stem cells (ADSCs) and antibiotics to overcome these challenges, thereby enhancing treatment efficacy. A systematic synthesis of the results of recent in vivo studies, predominantly those using rat models, was performed. Studies that evaluated the effectiveness of ADSCs combined with antibiotics against common pathogens in implant-related osteomyelitis, particularly Staphylococcus aureus and methicillin-resistant Staphylococcus epidermidis, were selected. A significant reduction in symptoms such as swelling, abscess formation, and bacterial burden in the ADSCs + antibiotic-treated group was observed in all studies. In addition, microcomputed tomography revealed reduced osteolysis, indicating enhanced bone preservation. Furthermore, histological examination revealed improved tissue structure and altered immune response, signifying the dual role of ADSCs in enhancing antibiotic action and modulating the immune system. This review highlights the promising role of the concurrent use of ADSCs and antibiotics in the treatment of implant-related osteomyelitis. This novel therapeutic strategy has the potential to revolutionize the management of complex orthopedic infections, especially those resistant to conventional treatments. However, further research is required to translate the results of animal studies into clinical applications and to develop optimized treatment protocols for human use.

Potential antibacterial activity and healing effect of topical administration of bone marrow and adipose mesenchymal stem cells encapsulated in collagen-fibrin hydrogel scaffold on full-thickness burn wound infection caused by Pseudomonas aeruginosa

Burns injuries are prone to hospital-acquired infections, and Pseudomonas aeruginosa is one of the most common causes of mortality and morbidity in patients with burn injuries. Thus, this study aimed to analyze the effects of topical treatment with bone marrow (BM-MSC) and adipose mesenchymal stem cells (AD-MSC) encapsulated in collagen and fibrin scaffolds in a Balb/c model of burn wound infection. Extraction of stem cells from adipose and bone marrow tissue of rats was performed and cells were characterized using standard methods. Then, collagen, fibrin and collagen-fibrin scaffolds were constructed and the extracted cells were encapsulated in all three scaffolds. Then, 3rd degree burn was induced in mice and 1.5 × 108 (CFU/ml) of P. aeruginosa was introduced to the burn wound. Subsequently, after 24 h of inducing wound infection, encapsulated MSCs were introduced as dressings to burn wound infection and microbial load as well as rate of wound infection healing was measured. The results of this study showed that the use of BM-MSC and AD-MSC encapsulated in collagen-fibrin scaffold reduced the bacteria load down to 54 and 21 CFU/gr, respectively (P < 0.05). Moreover, BM-MSC and AD-MSC encapsulated in collagen-fibrin showed 80% and 75% wound healing, respectively (P < 0.05). Also, we found no significant between cell origin and healing. Encapsulation of MSCs into collagen-fibrin scaffolds could be effective not only against P. aeruginosa infection, but also healing and regeneration of burn wound.

Development of a novel circular mRNA vaccine of six protein combinations against Staphylococcus aureus

Staphylococcus aureus is an extraordinarily versatile pathogen, which is currently the most common cause of nosocomial and community infections. Considering that increased antibiotic resistance may hasten the spread of S. aureus, developing an effective vaccine can possibly aid in its control. The RNA vaccine coding immunodominance epitopes from bacteria provide a potential method to induce T and B cell immune responses by translating them into cells. Furthermore, using bioinformatics to create circular RNA vaccines can ensure that the translation of the vaccine is potent and durable. In this study, 7 cytotoxic T lymphocyte (CTL) epitopes, 4 helper T lymphocyte (HTL) epitopes, and 15 B cell epitopes from 6 proteins that are closely associated with the S. aureus virulence and invasion and critical to natural immune responses were mapped. To verify their interactions, all epitopes were docked with the corresponding MHC alleles. The final vaccine was composed of 26 epitopes and the adjuvant β-defencin, and a disulfide bond was also introduced to improve its stability. After the prediction of structure and characteristics, the developed vaccine was docked with TLR2 and TLR4, which induce immunological responses in S. aureus infection. According to the molecular dynamic simulation, the vaccine might interact strongly with TLRs. Meanwhile, it performed well in immunological simulation and population coverage prediction. Finally, the vaccine was converted into a circular RNA using a series of helper sequences to aid in vaccine circulation translation. Hopefully, this proposed structure will be proven to serve a viable vaccine against S. aureus.Communicated by Ramaswamy H. Sarma.

Combined adipose-derived mesenchymal stem cell and antibiotic therapy can effectively treat periprosthetic joint infection in rats

Periprosthetic joint infection (PJI) is characterized by biofilm infection, which is difficult to alleviate while preserving implant integrity. Furthermore, long-term antibiotic therapy may increase the prevalence of drug-resistant bacterial strains, necessitating a non-antibacterial approach. Adipose-derived stem cells (ADSCs) exert antibacterial effects; however, their efficacy in PJI remains unclear. This study investigates the efficacy of combined intravenous ADSCs and antibiotic therapy in comparison to antibiotic monotherapy in a methicillin-sensitive Staphylococcus aureus (MSSA)-infected PJI rat model. The rats were randomly assigned and equally divided into 3 groups: no-treatment group, antibiotic group, ADSCs with antibiotic group. The ADSCs with antibiotic group exhibited the fastest recovery from weight loss, with lower bacterial counts (p = 0.013 vs. no-treatment group; p = 0.024 vs. antibiotic group) and less bone density loss around the implants (p = 0.015 vs. no-treatment group; p = 0.025 vs. antibiotic group). The modified Rissing score was used to evaluate localized infection on postoperative day 14 and was the lowest in the ADSCs with antibiotic group; however, no significant difference was observed between the antibiotic group and ADSCs with antibiotic group (p < 0.001 vs. no-treatment group; p = 0.359 vs. antibiotic group). Histological analysis revealed a clear, thin, and continuous bony envelope, a homogeneous bone marrow, and a defined, normal interface in the ADSCs with antibiotic group. Moreover, the expression of cathelicidin expression was significantly higher (p = 0.002 vs. no-treatment group; p = 0.049 vs. antibiotic group), whereas that of tumor necrosis factor (TNF)-α and interleukin(IL)-6 was lower in the ADSCs with antibiotic group than in the no-treatment group (TNF-α, p = 0.010 vs. no-treatment group; IL-6, p = 0.010 vs. no-treatment group). Thus, the combined intravenous ADSCs and antibiotic therapy induced a stronger antibacterial effect than antibiotic monotherapy in a MSSA-infected PJI rat model. This strong antibacterial effect may be related to the increased cathelicidin expression and decreased inflammatory cytokine expression at the site of infection.

The resistance mechanisms of bacteria against ciprofloxacin and new approaches for enhancing the efficacy of this antibiotic

For around three decades, the fluoroquinolone (FQ) antibiotic ciprofloxacin has been used to treat a range of diseases, including chronic otorrhea, endocarditis, lower respiratory tract, gastrointestinal, skin and soft tissue, and urinary tract infections. Ciprofloxacin's main mode of action is to stop DNA replication by blocking the A subunit of DNA gyrase and having an extra impact on the substances in cell walls. Available in intravenous and oral formulations, ciprofloxacin reaches therapeutic concentrations in the majority of tissues and bodily fluids with a low possibility for side effects. Despite the outstanding qualities of this antibiotic, Salmonella typhi, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa have all shown an increase in ciprofloxacin resistance over time. The rise of infections that are resistant to ciprofloxacin shows that new pharmacological synergisms and derivatives are required. To this end, ciprofloxacin may be more effective against the biofilm community of microorganisms and multi-drug resistant isolates when combined with a variety of antibacterial agents, such as antibiotics from various classes, nanoparticles, natural products, bacteriophages, and photodynamic therapy. This review focuses on the resistance mechanisms of bacteria against ciprofloxacin and new approaches for enhancing its efficacy.

Surface configuration of microarc oxidized Ti with regionally loaded chitosan hydrogel containing ciprofloxacin for improving biological performance

The bacterial colonization and poor osseointegration of Ti implants significantly compromise their applications in load-bearing bone repair and replacement. To endorse the Ti with both excellent bioactivity and antibacterial ability, we developed a microarc oxidation coating that was modified uniformly by hydroxyapatite (HA) nanodots arrays and loaded regionally with chitosan hydrogel containing ciprofloxacin. The bonding between the HA nanodots covered coating and the chitosan hydrogel is further enhanced via silanization and chemical grafting of glutaraldehyde. Benefiting from the regionally loaded structure of the chitosan hydrogel, the chitosan hydrogel unloaded area can promote the cell adhesion and proliferation with excellent bioactivity, though relatively low OD value of cck8 has been observed at the beginning of the cell culturing. Whereas, the OD value of cck8 rises with the prolongation of the cell culturing time due to the degradation of the regionally loaded chitosan hydrogel. With the help of the laden ciprofloxacin in chitosan hydrogels, the sample effectively sterilizes the bacterial with a bacteriostatic ring. Therefore, regional loading of chitosan hydrogel containing ciprofloxacin on the modified microarc oxidation coating is a good approach to endorse Ti with both excellent bioactivity and antibacterial ability.

Cell-based carrier for targeted hitchhiking delivery

Drug delivery systems aim at improving drug transport efficiency and therapeutic efficacy by rational design, and current research on conventional delivery systems brings new developments for disease treatment. Recently, studies on cell-based drug delivery systems are rapidly emerging, which shows great advantages in comparison to conventional drug delivery system. The system uses cells as carriers to delivery conventional drugs or nanomedicines and shows good biocompatibility and enhanced targeting efficiency, beneficial from self component and its physiological function. The construction methodology of cell-based carrier determines the effect on the physiological functions of transporting cell and affects its clinical application. There are different strategies to prepare cell-based carrier, such as direct internalization or surface conjugation of drugs or drug loaded materials. Thus, it is necessary to fully understand the advantages and disadvantages of different strategies for constructing cell-based carrier and then to seek the appropriate construction methodology for achieving better therapeutic results based on disease characterization. We here summarize the application of different types of cell-based carriers reported in recent years and further discuss their applications in disease therapy and the dilemmas faced in clinical translation. We hope that this summary can accelerate the process of clinical translation by promoting the technology development of cell-based carrier.

A biodegradable Fe/Zn-3Cu composite with requisite properties for orthopedic applications

Zinc (Zn)-based metals and alloys are emerging as promising biodegradable implant materials due to their inherent biodegradability and good biocompatibility. However, this class of materials exhibits low mechanical strength and a slow degradation rate, which hinders their clinical application. Here we report the development of a new biodegradable Fe/Zn-3Cu composite fabricated by infiltration casting of a Zn-3Cu alloy into an Fe foam followed by hot-rolling. Our results indicate that the hot-rolled (HR) Fe/Zn-3Cu composite exhibited an α-Zn matrix phase, a secondary CuZn₅ phase, and an α-Fe phase. The HR Fe/Zn-3Cu composite exhibited an ultimate tensile strength of 269 MPa, a tensile yield strength of 210 MPa, and an elongation of 27%. The HR Fe/Zn-3Cu composite showed a degradation rate of 228 µm/year after immersion in Hanks' solution for 30 d The diluted extract of the HR Fe/Zn-3Cu composite exhibited a higher cell viability than that of the HR Zn-3Cu alloy in relation to MC3T3-E1 and MG-63 cells. Furthermore, the HR Fe/Zn-3Cu composite showed significantly better antibacterial ability than that of the HR Zn-3Cu alloy in relation to S. aureus. Overall, the HR Fe/Zn-3Cu composite can be anticipated to be a promising biodegradable implant material for bone-fixation applications. STATEMENT OF SIGNIFICANCE: This work reports a new biodegradable Fe/Zn-3Cu composite fabricated by infiltration casting and followed by hot-rolling for biodegradable bone-fixation application. Our findings demonstrated that the hot-rolled (HR) Fe/Zn-3Cu composite exhibited an ultimate tensile strength of 269.1 MPa, a tensile yield strength of 210.3 MPa, and an elongation of 26.7%. HR Fe/Zn-3Cu composite showed a degradation rate of 227.6 µm/a, higher than HR Zn-3Cu alloy after immersion in Hanks' solution for 30 d The diluted extracts of the HR Fe/Zn-3Cu composite exhibited a higher cell viability than HR Zn-3Cu alloy toward MC3T3-E1 cells. Furthermore, the HR Fe/Zn-3Cu composite showed significantly better antibacterial ability than the HR Zn-3Cu alloy toward S. aureus.

Bone marrow mesenchymal stem cells offer an immune-privileged niche to Cutibacterium acnes in case of implant-associated osteomyelitis

Considered as some of the most devastating complications, Cutibacterium acnes (C. acnes)-related osteomyelitis are among the hardest infections to diagnose and treat. Mesenchymal stem cells (MSCs) secrete number of immunomodulatory and antimicrobial soluble factors, making them an attractive treatment for bacterial infection. In this study, we examined MSCs/C. acnes interaction and analyzed the subsequent MSCs and bacteria's behaviors. Human bone marrow-derived MSCs were infected by C. acnes clinical strain harvested from non-infected bone site. Following 3 h of interaction, around 4% of bacteria were found in the intracellular compartment. Infected MSCs increased the secretion of prostaglandin E2 and indolamine 2,3 dioxygenase immunomodulatory mediators. Viable intracellular bacteria analyzed by infrared spectroscopy and atomic force microscopy revealed deep modifications in the wall features. In comparison with unchallenged bacteria, the viable intracellular bacteria showed (i) an increase in biofilm formation on orthopaedical-based materials, (ii) an increase in the invasiveness of osteoblasts and (iii) persistence in macrophage, suggesting the acquisition of virulence factors. Overall, these results showed a direct impact of C. acnes on bone marrow-derived MSCs, suggesting that blocking the C. acnes/MSCs interactions may represent an important new approach to manage chronic osteomyelitis infections. STATEMENT OF SIGNIFICANCE: The interaction of bone commensal C. acnes with bone marrow mesenchymal stem cells induces modifications in C. acnes wall characteristics. These bacteria increased (i) the biofilm formation on orthopaedical-based materials, (ii) the invasiveness of bone forming cells and (iii) the resistance to macrophage clearance through the modification of the wall nano-features and/or the increase in catalase production.

Technology for Repairing Osteomyelitic Bone Defects Using Autologous Mesenchymal Stromal Cells on a Collagen Matrix in Experiment

The aim of the study was to develop a technology for repairing an osteomyelitic bone defect using autologous adipose tissue mesenchymal stromal cells (MSCs) bound to a collagen matrix and to test the efficacy of this technique.

Staphylococcus aureus Vaccine Research and Development: The Past, Present and Future, Including Novel Therapeutic Strategies

Staphylococcus aureus is one of the most important human pathogens worldwide. Its high antibiotic resistance profile reinforces the need for new interventions like vaccines in addition to new antibiotics. Vaccine development efforts against S. aureus have failed so far however, the findings from these human clinical and non-clinical studies provide potential insight for such failures. Currently, research is focusing on identifying novel vaccine formulations able to elicit potent humoral and cellular immune responses. Translational science studies are attempting to discover correlates of protection using animal models as well as in vitro and ex vivo models assessing efficacy of vaccine candidates. Several new vaccine candidates are being tested in human clinical trials in a variety of target populations. In addition to vaccines, bacteriophages, monoclonal antibodies, centyrins and new classes of antibiotics are being developed. Some of these have been tested in humans with encouraging results. The complexity of the diseases and the range of the target populations affected by this pathogen will require a multipronged approach using different interventions, which will be discussed in this review.

Microfluidic Tools for Enhanced Characterization of Therapeutic Stem Cells and Prediction of Their Potential Antimicrobial Secretome

Antibiotic resistance is creating enormous attention on the development of new antibiotic-free therapy strategies for bacterial diseases. Mesenchymal stromal stem cells (MSCs) are the most promising candidates in current clinical trials and included in several cell-therapy protocols. Together with the well-known immunomodulatory and regenerative potential of the MSC secretome, these cells have shown direct and indirect anti-bacterial effects. However, the low reproducibility and standardization of MSCs from different sources are the current limitations prior to the purification of cell-free secreted antimicrobial peptides and exosomes. In order to improve MSC characterization, novel label-free functional tests, evaluating the biophysical properties of the cells, will be advantageous for their cell profiling, population sorting, and quality control. We discuss the potential of emerging microfluidic technologies providing new insights into density, shape, and size of live cells, starting from heterogeneous or 3D cultured samples. The prospective application of these technologies to studying MSC populations may contribute to developing new biopharmaceutical strategies with a view to naturally overcoming bacterial defense mechanisms.

Antibacterial Titanium Implants Biofunctionalized by Plasma Electrolytic Oxidation with Silver, Zinc, and Copper: A Systematic Review

Patients receiving orthopedic implants are at risk of implant-associated infections (IAI). A growing number of antibiotic-resistant bacteria threaten to hamper the treatment of IAI. The focus has, therefore, shifted towards the development of implants with intrinsic antibacterial activity to prevent the occurrence of infection. The use of Ag, Cu, and Zn has gained momentum as these elements display strong antibacterial behavior and target a wide spectrum of bacteria. In order to incorporate these elements into the surface of titanium-based bone implants, plasma electrolytic oxidation (PEO) has been widely investigated as a single-step process that can biofunctionalize these (highly porous) implant surfaces. Here, we present a systematic review of the studies published between 2009 until 2020 on the biomaterial properties, antibacterial behavior, and biocompatibility of titanium implants biofunctionalized by PEO using Ag, Cu, and Zn. We observed that 100% of surfaces bearing Ag (Ag-surfaces), 93% of surfaces bearing Cu (Cu-surfaces), 73% of surfaces bearing Zn (Zn-surfaces), and 100% of surfaces combining Ag, Cu, and Zn resulted in a significant (i.e., >50%) reduction of bacterial load, while 13% of Ag-surfaces, 10% of Cu-surfaces, and none of Zn or combined Ag, Cu, and Zn surfaces reported cytotoxicity against osteoblasts, stem cells, and immune cells. A majority of the studies investigated the antibacterial activity against S. aureus. Important areas for future research include the biofunctionalization of additively manufactured porous implants and surfaces combining Ag, Cu, and Zn. Furthermore, the antibacterial activity of such implants should be determined in assays focused on prevention, rather than the treatment of IAIs. These implants should be tested using appropriate in vivo bone infection models capable of assessing whether titanium implants biofunctionalized by PEO with Ag, Cu, and Zn can contribute to protect patients against IAI.

Nanoconjugates-Based Stem Cell Therapy for the Management of COVID-19

A potential ability of stem cells (SCs) is to regenerate and repair tissues in the human body by providing great prospects for therapeutic applications in the field of medicine. Currently, SC therapy is used in various conditions like diabetes, neurodegenerative disorders, etc. but faces some limitations like patient biocompatibility and chances of cross-infection. SCs are further modulated with nanoconjugates to overcome such challenges and will offer an advantage in the treatment of COVID-19. This pandemic requires design and development of proper treatment to save the life of human beings. Advancements in SC-based nanoconjugated therapy will open new avenues and create a significant impact in the development of futuristic nanomedicine. It may also emerge as a potential therapy for the management of infection in patients suffering from SARS-CoV-2 and related diseases such as pneumonia and virus-induced lung injuries.

Graphical abstract