Rat Model Of Infection Research Articles

Cytomegalovirus infection of the fetal brain: intake of aspirin during pregnancy blunts neurodevelopmental pathogenesis in the offspring

BackgroundCongenital cytomegalovirus (CMV) infections represent one leading cause of human neurodevelopmental disorders. Despite their high prevalence and severity, no satisfactory therapy is available and pathophysiology remains elusive. The pathogenic involvement of immune processes occurring in infected developing brains has been increasingly documented. Here, we have used our previously validated rat model of CMV infection of the fetal brain in utero to test whether the maternal administration of four different drugs with immunomodulatory properties would have an impact on the detrimental postnatal outcome of CMV infection.MethodsCMV infection of the rat fetal brain was done intracerebroventricularly. Each of the drugs, including acetylsalicylic acid (aspirin, ASA), a classical inhibitor of cyclooxygenases Cox-1 and Cox-2, the two key rate-limiting enzymes of the arachidonic acid-to-prostaglandins (PG) synthesis pathway, was administered to pregnant dams until delivery. ASA was selected for subsequent analyses based on the improvement in postnatal survival. A combination of qRT-PCR, mass spectrometry-based targeted lipidomics, immunohistochemistry experiments, monitoring of neurologic phenotypes and electrophysiological recordings was used to assess the impact of ASA in CMV-infected samples and pups. The postnatal consequences of CMV infection were also analyzed in rats knocked-out (KO) for Cox-1.ResultsIncreased PGE2 levels and increased proportions of Cox-1+ and Cox-2+ microglia were detected in CMV-infected developing brains. Maternal intake of ASA led to decreased proportion of Cox-1+ fetal, but not neonatal, microglia, while leaving the proportions of Cox-2+ microglia unchanged. Maternal intake of ASA also improved the key postnatal in vivo phenotypes caused by CMV infection and dramatically prevented against the spontaneous epileptiform activity recorded in neocortical slices from CMV-infected pups. In contrast with maternal intake of ASA, Cox-1 KO pups displayed no improvement in the in vivo phenotypes after CMV infection. However, as with ASA administration, the spontaneous epileptiform activity was dramatically inhibited in neocortical slices from CMV-infected, Cox-1 KO pups.ConclusionOverall, our data indicate that, in the context of CMV infection of the fetal brain, maternal intake of ASA during pregnancy improved CMV-related neurodevelopmental alterations in the offspring, likely via both Cox-1 dependent and Cox-1 independent mechanisms, and provide proof-of-principle for the use of ASA against the detrimental outcomes of congenital CMV infections.

Cronobacter sakazakii lysozyme inhibitor LprI mediated by HmsP and c-di-GMP is essential for biofilm formation and virulence.

Cronobacter sakazakii poses a significant threat, particularly to neonates and infants. Despite its strong pathogenicity, understanding of C. sakazakii biofilms and their role in infections remains limited. This study investigates the roles of HmsP and c-di-GMP in biofilm formation and identifies key genetic and proteomic elements involved. Gene knockout experiments reveal that HmsP and c-di-GMP are linked to biofilm formation in C. sakazakii. Comparative proteomic profiling identifies the lysozyme inhibitor protein LprI, which is downregulated in hmsP knockouts and upregulated in c-di-GMP knockouts, as a potential biofilm formation factor. Further investigation of the lprI knockout strain shows significantly reduced biofilm formation and decreased virulence in a rat infection model. Additionally, LprI is demonstrated to bind extracellular DNA, suggesting a role in anchoring C. sakazakii within the biofilm matrix. These findings enhance our understanding of the molecular mechanisms underlying biofilm formation and virulence in C. sakazakii, offering potential targets for therapeutic intervention and food production settings.IMPORTANCECronobacter sakazakii is a bacterium that poses a severe threat to neonates and infants. This research elucidates the role of the lysozyme inhibitor LprI, modulated by HmsP and c-di-GMP, and uncovers a key factor in biofilm formation and virulence. The findings offer crucial insights into the molecular interactions that enable C. sakazakii to form resilient biofilms and persist in hostile environments, such as those found in food production facilities. These insights not only enhance our understanding of C. sakazakii pathogenesis but also identify potential targets for novel therapeutic interventions to prevent or mitigate infections. This work is particularly relevant to public health and the food industry, where controlling C. sakazakii contamination in powdered infant formula is vital for safeguarding vulnerable populations.

Mapping Staphylococcus aureus at Early and Late Stages of Infection in a Clinically Representative Hip Prosthetic Joint Infection Rat Model.

Prosthetic joint infection (PJI) continues to be a devastating complication following total joint replacement surgeries where Staphylococcus aureus is the main offending organism. To improve our understanding of the disease pathogenesis, a histological analysis of infected peri-implant tissue in a hip PJI rat model was utilized to assess S. aureus spread and tissue reaction at early and late stages of infection. Sprague-Dawley rats were used and received a left cemented hip hemiarthroplasty using a 3D-printed titanium femoral stem. The rats received an intra-articular injection of S. aureus Xen36. These infected rats were sacrificed either at 3 days post-infection (early-stage infection) or at 13-days post-infection (late-stage infection). The femoral and acetabular tissues of all animals were harvested at euthanasia. Histological analysis for the harvested tissue was performed using immunohistochemistry, hematoxylin and eosin, as well as Masson's trichrome stains. Histological examination revealed significant quantitative and qualitative differences in peri-implant tissue response to infection at early and late stages. This hip PJI rat model identified clear histologic differences between early and late stages of S. aureus infection and how quickly bacterial infiltration could occur. These findings can provide insight into why certain surgical strategies like debridement and antibiotics may be associated with high failure rates.

Potent neutralizing human monoclonal antibodies protect from Rift Valley fever encephalitis.

Rift Valley fever (RVF) is an emerging arboviral disease affecting both humans and livestock. In humans, RVF displays a spectrum of clinical manifestations, including encephalitis. To date, there are no FDA-approved vaccines or therapeutics for human use, although several are in preclinical development. Few small-animal models of RVF encephalitis exist, further complicating countermeasure assessment. Human mAbs RVFV-140, RVFV-268, and RVFV-379 are recombinant potently neutralizing antibodies that prevent infection by binding the RVFV surface glycoproteins. Previous studies showed that both RVFV-268 and RVFV-140 improve survival in a lethal mouse model of disease, and RVFV-268 has prevented vertical transmission in a pregnant rat model of infection. Despite these successes, evaluation of mAbs in the context of brain disease has been limited. This is the first study to our knowledge to assess neutralizing antibodies for prevention of RVF neurologic disease using a rat model. Administration of RVFV-140, RVFV-268, or RVFV-379 24 hours prior to aerosol exposure to the virulent ZH501 strain of RVFV resulted in substantially enhanced survival and lack of neurological signs of disease. These results using a stringent and highly lethal aerosol infection model support the potential use of human mAbs to prevent the development of RVF encephalitis.

Inhalable tobramycin EEG powder formulation for treating Pseudomonas aeruginosa-induced lung infection

Pulmonary delivery of antibiotics is an effective strategy in treating bacterial lung infection for cystic fibrosis patients, by achieving high local drug concentrations and reducing overall systemic exposure compared to systemic administration. However, the inherent anatomical lung defense mechanisms, formulation characteristics, and drug-device combination determine the treatment efficacy of the aerosol delivery approach. In this study, we prepared a new tobramycin (Tobi) dry powder aerosol using excipient enhanced growth (EEG) technology and evaluated the in vitro and in vivo aerosol performance. We further established a Pseudomonas aeruginosa-induced lung infection rat model using an in-house designed novel liquid aerosolizer device. Notably, novel liquid aerosolizer yields comparable lung infection profiles despite administering 3-times lower P. aeruginosa CFU per rat in comparison to the conventional intratracheal administration. Dry powder insufflator (e.g. Penn-Century DP-4) to administer small powder masses to experimental animals is no longer commercially available. To address this gap, we developed a novel rat air-jet dry powder insufflator (Rat AJ DPI) that can emit 68–70 % of the loaded mass for 2 mg and 5 mg of Tobi-EEG powder formulations, achieving a high rat lung deposition efficiency of 79 % and 86 %, respectively. Rat AJ DPI can achieve homogenous distribution of Tobi EEG powder formulations at both loaded mass (2 mg and 5 mg) over all five lung lobes in rats. We then demonstrated that Tobi EEG formulation delivered by Rat AJ DPI can significantly decrease CFU counts in both trachea and lung lobes at 2 mg (p < 0.05) and 5 mg (p < 0.001) loaded mass compared to the untreated P. aeruginosa-infected group. Tobi EEG powder formulation delivered by the novel Rat AJ DPI showed excellent efficiencies in substantially reducing the P. aeruginosa-induced lung infection in rats.

Enhanced antibiofilm potential of low-intensity pulsed ultrasound combined with 0.35% povidone-iodine in a rat model of periprosthetic joint infection.

Although low-intensity pulsed ultrasound (LIPUS) combined with disinfectants has been shown to effectively eliminate portions of biofilm in vitro, its efficacy in vivo remains uncertain. Our objective was to assess the antibiofilm potential and safety of LIPUS combined with 0.35% povidone-iodine (PI) in a rat debridement, antibiotics, and implant retention (DAIR) model of periprosthetic joint infection (PJI). A total of 56 male Sprague-Dawley rats were established in acute PJI models by intra-articular injection of bacteria. The rats were divided into four groups: a Control group, a 0.35% PI group, a LIPUS and saline group, and a LIPUS and 0.35% PI group. All rats underwent DAIR, except for Control, which underwent a sham procedure. General status, serum biochemical markers, weightbearing analysis, radiographs, micro-CT analysis, scanning electron microscopy of the prostheses, microbiological analysis, macroscope, and histopathology evaluation were performed 14 days after DAIR. The group with LIPUS and 0.35% PI exhibited decreased levels of serum biochemical markers, improved weightbearing scores, reduced reactive bone changes, absence of viable bacteria, and decreased inflammation compared to the Control group. Despite the greater antibiofilm activity observed in the PI group compared to the LIPUS and saline group, none of the monotherapies were successful in preventing reactive bone changes or eliminating the infection. In the rat model of PJI treated with DAIR, LIPUS combined with 0.35% PI demonstrated stronger antibiofilm potential than monotherapy, without impairing any local soft-tissue.

PH‑responsive nanozyme cascade catalysis: A strategy of BiVO4 application for modulation of pathological wound microenvironment

Persistent inflammation and bacterial infection commonly occur during the wound healing process, necessitating urgent development of effective strategies for treating drug-resistant bacterial infections. In this study, bismuth vanadate (BiVO4) was successfully synthesized as an antibacterial agent that promotes wound healing. Through In vitro antibacterial experiments, it was observed that the prepared BiVO4 exhibited excellent performance in catalyzing H2O2 to produce hydroxyl radicals (OH) at a lower concentration (0.2 mg mL−1), resulting in significant antibacterial effects against Gram-negative Extended-Spectrum β-Lactamases-Producing Escherichia coli (ESBL-E. coli) strains. Furthermore, biosafety tests, cell scratch experiments, and ESBL-E. coli infected wound rat model experiments demonstrated high biocompatibility of BiVO4 with a cell survival rate exceeding 85 %. Additionally, BiVO4 promoted the production of vascular endothelial growth factors and fibroblasts migration while contributing to collagen production, effectively facilitating immune reconstruction at the wound site. By integrating peroxidase (POD)-like under acidic conditions (pH 4) and catalase (CAT)-like catalytic activities at under neutral conditions (pH 7), BiVO4 exhibited the ability to activate free radical sterilization and accelerate wound healing by activating O2. Therefore, our findings provide evidence for a dual enzyme regulatory mechanism involving antibacterial properties and promotion of wound tissue reconstruction for potential application in both antibacterial treatment and wound healing.

Targeted treatment for biofilm-based infections using PEGylated tobramycin

Chronic infections often involve biofilm-based bacteria, in which the biofilm results in significant resistance against antimicrobial agents and prevents eradication of the infection. The physicochemical barrier presented by the biofilm matrix is a major impediment to the delivery of many antibiotics. Previously, PEGylation has been shown to improve antibiotic penetration into biofilms in vitro. In these studies, PEGylating tobramycin was investigated both in vitro and in vivo. Two distinct PEGylated tobramycin molecules were synthesized (mPEG-SA-Tob and mPEG-AA-Tob). Then, in a P. aeruginosa biofilm in vitro model, we found that mPEG-SA-Tob can operate as a prodrug and showed 7 times more effectiveness than tobramycin (MIC80: 14 μM vs.100 μM). This improved biofilm eradication is attributable to the fact that mPEG-SA-Tob can aid tobramycin to penetrate through the biofilm and overcome the alginate-mediated antibiotic resistance. Finally, we used an in vivo biofilm-based chronic pulmonary infection rat model to confirm the therapeutic impact of mPEG-SA-Tob on biofilm-based chronic lung infection. mPEG-SA-Tob has a better therapeutic impact than tobramycin in that it cannot only stop P. aeruginosa from multiplying in the lungs but can also reduce inflammation caused by infections and prevent a recurrence infection. Overall, our findings show that PEGylated tobramycin is an effective treatment for biofilm-based chronic lung infections.

Chitosan aerogel loaded with biogenic palladium nanoparticles CH/Pd NPs exert antibacterial activity and wound addressing application in vitro and in vivo against bacterial skin infections

Bacterial skin infections that infect wounds and burns are considered one of the most serious medical problems that lead to delay wound healing, toxicity and even death. Therefore, there is an urgent need to develop an effective pharmaceutical material that promotes the treating of skin bacterial infections. Within this, we aimed in this study to synthesis and assess the effectiveness of novel chitosan/palladium nanoparticles (CH/Pd NPs) aerogel composites in treating bacterial skin infections and wound healing. Green method was employed for synthesis of Pd NPs using Allium sativum (A. sativum) extract, while crosslinking process and freeze-drying cycle were utilized for preparation of CH/Pd NPs aerogel composites. The prepared Pd NPs and CH/Pd NPs aerogel composite were thoroughly characterized using UV–vis, FTIR, XRD and SEM. The GC–MS analysis revealed that the main components in the A. sativum were diallyl disulfide (55.88 %) and diallyl trisulfide (24.34 %) which were among the four identified components. Additionally, the total phenols and flavonoids contents were 61.3 mg GAE/100 g and 18.8 mg QE/100 g, respectively. The swelling capacity of CH/Pd NPs aerogel microspheres reach 400 % with blood compatibility and slightly hemolysis ratio about 0.4 %. In vitro, the antibacterial studies demonstrated that loading Pd NPs with CH aerogel microspheres enhanced their effectiveness against MDR bacteria with complete inhibition for all bacterial strains growth. The CH/Pd NPs aerogel microspheres exhibited a significant inhibitory effect on biofilm formation. The biofilm inhibition percentage was found to be 87 % against the biofilm of S. aureus and 80 % against the biofilm of P. aeruginosa. In vivo infection model in rats, CH and CH/Pd NPs aerogel films stimulated skin tissue formation and healing wounds completely in 6 days with highly reduced in MDR and biofilm producing bacterial count. Finally, CH/Pd NPs aerogel composites represent a promising therapeutic strategy for the effective and enhanced healing of infected wounds.

Functional and structural basis of human parainfluenza virus type 3 neutralization with human monoclonal antibodies.

Human parainfluenza virus type 3 (hPIV3) is a respiratory pathogen that can cause severe disease in older people and infants. Currently, vaccines against hPIV3 are in clinical trials but none have been approved yet. The haemagglutinin-neuraminidase (HN) and fusion (F) surface glycoproteins of hPIV3 are major antigenic determinants. Here we describe naturally occurring potently neutralizing human antibodies directed against both surface glycoproteins of hPIV3. We isolated seven neutralizing HN-reactive antibodies and a pre-fusion conformation F-reactive antibody from human memory B cells. One HN-binding monoclonal antibody (mAb), designated PIV3-23, exhibited functional attributes including haemagglutination and neuraminidase inhibition. We also delineated the structural basis of neutralization for two HN and one F mAbs. MAbs that neutralized hPIV3 in vitro protected against infection and disease in vivo in a cotton rat model of hPIV3 infection, suggesting correlates of protection for hPIV3 and the potential clinical utility of these mAbs.

SrTiO3 Nanotube-Based "Pneumatic Nanocannon" for On-Demand Delivery of Antibacterial and Sustained Osseointegration Enhancement.

Infection and aseptic loosening caused by bacteria and poor osseointegration remain serious challenges for orthopedic implants. The advanced surface modification of implants is an effective strategy for addressing these challenges. This study presents a "pneumatic nanocannon" coating for titanium orthopedic implants to achieve on-demand release of antibacterial and sustained release of osteogenic agents. SrTiO3 nanotubes (SrNT) were constructed on the surface of Ti implants as "cannon barrel," the "cannonball" (antibiotic) and "propellant" (NH4HCO3) were codeposited into SrNT with assistance of mussel-inspired copolymerization of dopamine and subsequently sealed by a layer of polydopamine. The encapsulated NH4HCO3 within the nanotubes could be thermally decomposed into gases under near-infrared irradiation, propelling the on-demand delivery of antibiotics. This coating demonstrated significant efficacy in eliminating typical pathogenic bacteria both in planktonic and biofilm forms. Additionally, this coating exhibited a continuous release of strontium ions, which significantly enhanced the osteogenic differentiation of preosteoblasts. In an implant-associated infection rat model, this coating demonstrated substantial antibacterial efficiency (>99%) and significant promotion of osseointegration, along with alleviated postoperative inflammation. This pneumatic nanocannon coating presents a promising approach to achieving on-demand infection inhibition and sustained osseointegration enhancement for titanium orthopedic implants.

A hydrogel dressing loaded with tea tree oil nanoemulsion accelerates methicillin-resistant Staphylococcus aureus-infected wound healing

Drug-resistant bacterial infections can easily lead to delayed wound healing and pose a serious threat to patients' health. Therefore, it was imperative to develop wound dressings to solve this problem. Herein, we developed a hydrogel based on laponite and polyacrylamide (PAAG/LAP) and loaded with tea tree oil nano-emulsion (nanoTTO) by a simple one-step mixing method via the principle of photopolymerization and its potential use and safety for MRSA-infected skin wounds. The evaluation showed that the PAAG/LAP/nanoTTO30 % hydrogel exhibited excellent compressive resistance (∼85 kPa), good biocompatibility, and great antibacterial properties against MRSA in vitro and in vivo (over 90 %). Cell migration results showed that the relative wound area ratio of the PAAG/LAP/nanoTTO30 % hydrogel treatment group (∼55.18 %) was significantly lower than that of the control group (∼68.89 %). The results of the in vivo infection rat model showed that compared with other control groups, the PAAG/LAP/nanoTTO30 % hydrogel treatment group had the lowest relative wound area ratio (8.78 %) within 12 days. Moreover, the results showed the PAAG/LAP/nanoTTO30 % hydrogel could promote MRSA-infected wound healing by directly killing bacteria and promoting angiogenesis. In conclusion, our study provided an antibacterial hydrogel dressing that does not require loading antibiotics for wounds infected by drug-resistant bacteria, expecting to achieve infected wound healing.

Cu-MOF loaded chitosan based freeze-dried highly porous dressings with anti-biofilm and pro-angiogenic activities accelerated Pseudomonas aeruginosa infected wounds healing in rats

Metal–organic frameworks (MOFs)-based therapy opens a new area for antibiotic-drug free infections treatment. In the present study, chitosan membranes (CS) loaded with two concentrations of copper-MOF 10 mg/20 ml (Cu-MOF10/CS) & 20 mg/20 ml (Cu-MOF20/CS) were prepared by a simple lyophilization procedure. FTIR spectra of Cu-MOF10/CS and Cu-MOF20/CS dressings confirmed absence of any undesirable chemical changes after loading Cu-MOF. The SEM images of the synthesized materials (CS, Cu-MOF10/CS & Cu-MOF20/CS) showed interconnected porous structures. Cytocompatibility of the materials was confirmed by fibroblasts cells culturing and the materials were hemocompatible, with blood clotting index <5 %. Cu-MOF20/CS showed comparatively higher effective antibacterial activity against the tested strains; E. coli (149.2 %), P. aeruginosa (165 %) S. aureus (117.8 %) and MRSA (142 %) as compared to Amikacin, CS and Cu-MOF10/CS membranes. Similarly, Cu-MOF20/CS dressing significantly eradicated the biofilms; P. aeruginosa (37 %) and MRSA (52 %) respectively. In full thickness infected wound rat model, on day 23, Cu-MOF10/CS and Cu-MOF20/CS promoted wound healing up to 87.7 % and 82 % respectively. H&E staining of wounded tissues treated with Cu-MOF10/CS & Cu-MOF20/CS demonstrated enhanced neovascularization and re-epithelization along-with reduced inflammation, while trichrome staining exhibited increased collagen deposition. Overall, this study declares Cu-MOFs loaded chitosan dressings a multifunctional platform for the healing of infected wounds.

A glucan-particle based tularemia subunit vaccine induces T-cell immunity and affords partial protection in an inhalation rat infection model.

Tularemia is a zoonotic disease caused by the facultative intracellular gram-negative bacterium Francisella tularensis. F. tularensis has a very low infection dose by the aerosol route which can result in an acute, and potentially lethal, infection in humans. Consequently, it is classified as a Category A bioterrorism agent by the US Centers for Disease Control (CDC) and is a pathogen of concern for the International Biodefence community. There are currently no licenced tularemia vaccines. In this study we report on the continued assessment of a tularemia subunit vaccine utilising β-glucan particles (GPs) as a vaccine delivery platform for immunogenic F. tularensis antigens. Using a Fischer 344 rat infection model, we demonstrate that a GP based vaccine comprising the F. tularensis lipopolysaccharide antigen together with the protein antigen FTT0814 provided partial protection of F344 rats against an aerosol challenge with a high virulence strain of F. tularensis, SCHU S4. Inclusion of imiquimod as an adjuvant failed to enhance protective efficacy. Moreover, the level of protection afforded was dependant on the challenge dose. Immunological characterisation of this vaccine demonstrated that it induced strong antibody immunoglobulin responses to both polysaccharide and protein antigens. Furthermore, we demonstrate that the FTT0814 component of the GP vaccine primed CD4+ and CD8+ T-cells from immunised F344 rats to express interferon-γ, and CD4+ cells to express interleukin-17, in an antigen specific manner. These data demonstrate the development potential of this tularemia subunit vaccine and builds on a body of work highlighting GPs as a promising vaccine platform for difficult to treat pathogens including those of concern to the bio-defence community.

Formulation and evaluation of azithromycin-loaded silver nanoparticles for the treatment of infected wounds

Infected wounds pose a significant challenge in healthcare, requiring innovative therapeutic strategies. Therefore, there is a critical need for innovative pharmaceutical materials to improve wound healing and combat bacterial growth. This study examined the efficacy of azithromycin-loaded silver nanoparticles (AZM-AgNPs) in treating infected wounds. AgNPs synthesized using a green method with Quinoa seed extract were loaded with AZM. Characterization techniques, including X-ray Powder Diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and Uv-Vis analysis were utilized. The agar diffusion assay and determination of the MIC were used to assess the initial antibacterial impact of the formulations on both MRSA and E. coli. In addition, the antimicrobial, wound-healing effects and histological changes following treatment with the AZM-AgNPs were assessed using an infected rat model. The nanoparticles had size of 24.9 ± 15.2 nm for AgNPs and 34.7 ± 9.7 nm for AZM-AgNPs. The Langmuir model accurately characterized the adsorption of AZM onto the AgNP surface, indicating a maximum loading capacity of 162.73 mg/g. AZM-AgNPs exhibited superior antibacterial properties in vivo and in vitro compared to controls. Using the agar diffusion technique, AZM-AgNPs showed enhanced zones of inhibition against E. coli and MRSA, which was coupled with decreased MIC levels. In addition, in vivo studies showed that AZM-AgNP treated rats had the best outcome characterized by improved healing process, lower bacterial counts and superior epithelialization, compared to the control group. In conclusion, AZM-AgNPs can be synthesized using a green method with Quinoa seed with successful loading of azithromycin onto silver nanoparticles. In vitro and in vivo studies suggest the promising use of AZM-AgNPs as an effective therapeutic agent for infected wounds.

Synthesis and evaluation of a novel vancomycin-infused, biomimetic bone graft using a rat model of spinal implant-associated infection

BackgroundPostoperative infection is a complication of spinal fusion surgery resulting in increased patient morbidity. Strategies including intraoperative application of powdered vancomycin have been proposed to reduce the incidence of infection; however, such antimicrobial effects are short-lived. MethodsInstrumentation of the L4–L5 vertebrae was performed mimicking pedicle screw and rod fixation in 30 rats. Titanium instrumentation inoculated with either PBS or 1×105 CFU bioluminescent MRSA, along with biomimetic bone grafts infused with varying concentrations of vancomycin and 125 µg of rhBMP-2 (BioMim-rhBMP-2-VCM) were implanted prior to closure. Infection was quantified during the six-week postoperative period using bioluminescent imaging. Arthrodesis was evaluated using micro-CT. ResultsInfected animals receiving a bone graft infused with low-dose (0.18 mg/g) or high-dose vancomycin (0.89 mg/g) both exhibited significantly lower bioluminescent signal over the six-week postoperative period than control animals inoculated with MRSA and implanted with bone grafts lacking vancomycin (p=.019 and p=.007, respectively). Both low and high-dose vancomycin-infused grafts also resulted in a statistically significant reduction in average bioluminescence when compared to control animals (p=.027 and p=.047, respectively), independent of time. MicroCT analysis of animals from each group revealed pseudoarthrosis only in the control group, suggesting a correlation between infection and pseudoarthrosis. MRSA-inoculated control animals also had significantly less bone volume formation on micro-CT than the PBS-inoculated control cohort (p<.001), the MRSA+low-dose vancomycin-infused bone graft cohort (p<.001), and the MRSA+high-dose vancomycin-infused bone graft cohort (p<.001). ConclusionBioMim-rhBMP-2-VCM presents a novel tissue engineering approach to simultaneously promoting arthrodesis and antimicrobial prophylaxis in spinal fusion. Despite mixed evidence of potential osteotoxicity of vancomycin reported in literature, BioMim-rhBMP-2-VCM preserved arthrodesis and osteogenesis with increasing vancomycin loading doses due to the graft's osteoinductive composition.

409 Evaluation of a Novel Vancomycin-Infused, Biomimetic Bone Graft in a Rat model of Spinal Implant-Associated Infection

INTRODUCTION: Postoperative infection is a complication of spinal fusion surgery resulting in increased patient morbidity. Strategies including intraoperative application of powdered vancomycin have been proposed to reduce the incidence of infection, however such antimicrobial effects are short-lived. METHODS: Instrumentation of the L4-L5 vertebrae was performed mimicking pedicle screw and rod fixation in 30 rats. Titanium inoculated with PBS or 1x105 CFU bioluminescent MRSA and biomimetic bone grafts infused with varying concentrations of vancomycin were inserted before closure. Infection was quantified during the six-week postoperative period using IVIS bioluminescent imaging. Arthrodesis was evaluated using micro-CT. Histological analysis was utilized to evaluate fusion and leukocyte infiltration. RESULTS: Infected animals receiving a bone graft infused with high-dose vancomycin (0.89 mg/g) exhibited significantly lower bioluminescent signal over the six-week postoperative infection period (p = 0.032) than control animals inoculated with MRSA and implanted with bone grafts lacking vancomycin. Both high and low-dose (0.18 mg/g) vancomycin-infused grafts resulted in a statistically significant reduction in average bioluminescence when compared to control animals (p = 0.018 and p = 0.027, respectively), independent of time. MicroCT analysis of animals from each group revealed pseudoarthrosis only in the control group, suggesting a correlation between infection and pseudoarthrosis. Histology revealed the formation of fusion masses in all animals receiving vancomycin infused-bone grafts regardless of MRSA inoculation, with clearance of infection indicated by lack of abscess formation. MRSA-inoculated control animals receiving no vancomycin within the bone graft demonstrated significant abscess formation and lack of fusion mass. CONCLUSIONS: The novel vancomycin-infused, biomimetic bone graft effectively mitigated implant-associated infection while promoting fusion in a rat model of instrumented lumbar fusion.

Study on the therapeutic mechanism of HJ granules in a rat model of urinary tract infection caused by Escherichia coli

Ethnopharmacological relevanceUrinary tract infections (UTIs) are globally prevalent infectious diseases, predominantly caused by uropathogenic Escherichia coli (UPEC). The misuse of antibiotics has led to the emergence of several drug-resistant strains. Traditional Chinese Medicine (TCM) has its own advantages in the treatment of UTIs. HJ granules is a herbal formula used for the treatment of UTIs. However, its mechanism of action is not clear. Aim of the studyThe aim of this study was to investigate the therapeutic efficacy and mechanism of action of HJ granules in a rat model of UTI caused by Escherichia coli (E coli) CFT073. Materials and methodsSD rats were selected to establish a rat UTI model by injecting UPEC strain CFT073 into the bladder using the transurethral placement method. HJ granules were administered to rats after modelling and the efficacy of HJ granule was investigated by measuring urinary decanalogue, inflammatory factors in bladder tissue and pathological changes in the bladder after 3d of administration. Expression of sonic hedgehog (SHH), NOD-like receptor thermoprotein domain 3 (NLRP3), apoptosis-associated speck-like protein (ASC) and activation of cysteinyl aspartate specific proteinase-1 (caspase-1) were detected by western blotting and immunofluorescence staining in rat bladder tissue. NLRP3, ASC and caspase-1, a cysteine-containing aspartic protein, were expressed and activated. ResultsThe results showed that infection of rats with UPEC resulted in increased pH and erythrocytes in bladder irrigation fluid; increased expression of IL-1β, IL-6 and SHH and decreased expression of IL-10 in bladder tissue; and significant upregulation of the expression of both SHH and NLRP3 inflammasom and significant activation of NLRP3 inflammasom. HJ granules significantly increased the concentration of IL-10 in the bladder, inhibited the expression of SHH and NLRP3 inflammasom in bladder tissue, and suppressed the activation of NLRP3 inflammasom, thereby reducing inflammatory lesions in bladder tissue. ConclusionHJ granules may improve bladder injury and treat UTIs by inhibiting the expression and activation of NLRP3 inflammasom.

Enhancing antibacterial activity against multi-drug resistant wound bacteria: Incorporating multiple nanoparticles into chitosan-based nanofibrous dressings for effective wound regeneration

Wound infection continues to pose a significant challenge in the field of wound healing. Multi-drug resistant bacteria (MDR) make it even more complicated. Therefore, there is a pressing need to fabricate wound dressings with enhanced antimicrobial activity, particularly against MDR strains. In this study, we aimed to incorporate three antimicrobial nanoparticles into a chitosan-based nanofibrous mat (CS) and assess their antimicrobial activity against MDR bacteria. We fabricated CS mats incorporated with silver nanoparticles (CS-nAg), CuO nanoparticles (CS-nCuO), ZnO nanoparticles (CS-nZnO), a combination of Ag and CuO nanoparticles (CS-nAC), and a combination of Ag, CuO, and ZnO nanoparticles (CS-nACZ). The antimicrobial activity of these mats against MDR clinical isolates of four common wound bacteria including Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, and Acinetobacter baumannii were investigated. Each strain was tested using 10 isolates. According to in-vitro study, mats incorporated with a single type of nanoparticle demonstrated antimicrobial activity against certain isolates of P. aeruginosa, S. aureus, and E. coli. However, the antimicrobial activity was enhanced when multiple types of nanoparticles were combined (CS-nAC and CS-nACZ). Notably, CS-nACZ was the only mat that demonstrated antimicrobial activity against A. baumannii. In addition to its superior antimicrobial activity, CS-nACZ did not exhibit cytotoxicity towards fibroblasts. In an animal study using an infected wound rat model, the CS-nACZ mat demonstrated superior antimicrobial activity and excellent wound regeneration ability. These results suggest that the use of multiple nanoparticles in CS based wound dressing can lead to enhanced antimicrobial effects and effective wound regeneration.

Possibilities of local effect the healing of small bowel sutures in a rat model of acute intra-abdominal infection

Aims: Investigate the regeneration of the small bowel suture line regeneration after suturing with a material with antioxidant properties. Methodology: 7 intact rats, 63 with simulated intra-abdominal infection (IAI). A laparotomy was performed in 12 h after simulating. The small bowel was cut and sutured in 56 rats (2 groups of 28) after an abdominal lavage. Standard Kapron was used in the control group (CG). Kapron impregnated with a 5% solution of ethylmethylhydroxypyridine succinate was used in the research group (RG). Sections of the small bowel were collected from a total of 21 rats (7 intact rats, 7 rats with intra-abdominal infection (IAI) models, and 7 rats at different time points (1, 3, 5, and 7 days) post suturing) for subsequent histological examination. The preparations were stained with hematoxylin-eosin and by Mikel Calvo. The R/B coefficient (R/BC) was determined. The experiment's time duration was 7.5 days in December 2022. Results: R/BC increased (p&lt;0.05) in the connective tissue fibers of the small bowel submucosal base in 12 h after the simulating of IAI. R/BC increased (p&lt;0.05) in both groups in 1 day after suturing. R/BC increased in CG, decreased (p&lt;0.05) in RG in 3 days. Fibrin was found between the ligature’s fibers in RG. R/BC decreased (p&lt;0.05) in both groups in 5 days, indicators were smaller (p&lt;0.01) in RG. Fibrin was found between the ligature’s fibers in CG, granulation tissue was in RG. R/BC decreased in both groups in 7 days, but indicators were smaller in RG (p&lt;0.01). Unfilled areas in the granulation tissue between the ligature fibers were in CG. Conclusion: 1. The use of ligatures impregnated with the 5% ethylmethylhydroxypyridine succinate solution for suturing the small bowel in rats with intra-abdominal infection models is associated with the significant decrease in the activity of local proteins oxidation and the significant acceleration of local regeneration processes. 2. The creation of a suture material with antioxidant properties may be a promising direction for the prevention of suture leakage