Burn Wound Infection Research Articles

Adhesive, Stretchable, and Photothermal Antibacterial Hydrogel Dressings for Wound Healing of Infected Skin Burn at Joints.

Dressings for infectious skin burn wounds at joints should have therapeutic functions as well as high tissue-adhesion, stretching, and self-healing properties. This makes it difficult for most hydrogel dressings to simultaneously meet the above-mentioned requirements. In this study, poly(vinyl alcohol), anhydrous sodium borax, epigallocatechin gallate, and copper chloride were used to prepare a hydrogel dressing (PBEC) for the infected burn wound healing at joints. The PBEC hydrogel can adhere to a variety of substrates, has a stretching capacity, and quickly self-healing after being damaged. Additionally, the PBEC hydrogel has the properties of reactive oxygen species scavenging, photothermal sterilization, hemostatic ability, and biocompatibility. Finally, the hydrogel could accelerate the process of wound healing in vivo, especially with the assistance of near-infrared radiation. Therefore, the hydrogel dressing shows great potential for clinical application in the healing of infected burn wounds at joints.

Phylogenetic evaluation and genotypic identification of burn-related Pseudomonas aeruginosa strains isolated from post-burn human infections during hospitalization.

Cutaneous burn trauma, compromise of dermal layers and immune defense system is a physical and fiscal burden on healthcare systems. Burn-wound infections are a serious complication of thermal-injury and contribute significantly to care burden. After burn-induced trauma, sepsis by Pseudomonas aeruginosa impairs patient recovery and contributes to mortality and morbidity. Past studies show positive correlation between detection of Pseudomonas species and healing-impaired traumatic wounds. P. aeruginosa is a resilient opportunistic human pathogen and a nosocomial agent involved in pathology of healing-impaired wounds, especially in burn-patients. Expansive array of virulence determinants have resulted in gentamicin- and silver-resistant P. aeruginosa outbreaks. Knowledge of molecular dynamics and phylogeny of P. aeruginosa associated with burn-wounds is limited. Therefore, we conducted whole-genome sequencing for genotyping and phylogenetic analysis of P. aeruginosa burn-associated strains (n=19) isolated from 7 burn cases during hospitalization. Comparison of genetic features in P. aeruginosa strains in the core genome and mobilome detected genetic variations within some clonal infections overtime. Genetic variations were observed among different burn cases, with some features identified in severe lung infections. Polyclonal infections were also observed, with differing genotypes and virulence potentials, highlighting the importance of reasoned sampling of isolates for clinical testing.

Evaluation of the Cytotoxicity Effects of Bacteriophage VbɸPA-1 on the Virulent Pseudomonas aeruginosa, A375 Human Skin Melanoma Epithelial, and HFSF PI3 Human Skin Fibroblast Cells

Background: Gram-negative bacteria are the most common infectious bacteria and are life-threatening in burn patients. Phage therapy studies can help the hospital community eliminate these bacterial pathogens. Objectives: This study aimed to evaluate the effects of the isolated bacteriophages from hospital wastewater against Gram-negative pathogenic bacteria and investigate their cytotoxicity on two human skin cell lines. Methods: The bacterial strains were isolated from burn wound infections. Bacteriophages were isolated from the hospital wastewater treatment plant in Isfahan, Iran. Transmission electron microscopy, spot tests, and restriction enzyme digestion were considered for phage identification. Finally, the lactate dehydrogenase (LDH) and tetrazolium-based MTT assays were used to realize the cytotoxicity impacts of the isolated phages. The statistical analysis of cell viability was performed using a two-way analysis of variance (ANOVA). Results: The results showed that among the isolated strains, P. aeruginosa strain NEG_RA1300 (GenBank accession number: MW845642) was sensitive to the isolated phage VbɸPA-1. The TEM results showed a possible viral taxonomy of VbɸPA-1 based on its morphology, which belonged to the Myoviridae (T4-like phages). The MTT and LDH experiments showed no cytotoxicity of VbɸPA-1 on two tested cell lines. Conclusions: Based on the results, the inhibitory effect of isolated phage on P. aeruginosa isolated from burn wounds with no toxic effect on cell lines was very significant. This phage can also be an acceptable selection against burn wound infections.

Development of a Bentonite Nanoparticle-Based Transdermal Drug Delivery System for Burn Wound Infection Prevention

Development of a Bentonite Nanoparticle-Based Transdermal Drug Delivery System for Burn Wound Infection Prevention

Engineered Multifunctional Artificial Dermis for Infected Burn Wound Healing

AbstractBurn wound healing is a dynamic and interconnected process, with the complex status of the extracellular matrix (ECM) potentially leading to bacterial infections, drug resistance, or even fatality. However, it remains a grand challenge to assemble a skin‐like material showing similar biological properties as healthy ECM to accelerate burn healing. In this study, the ECM composition is closely mimicked and adaptive multifunctional artificial dermis is developed by leveraging Ag─S bonds, supramolecular interactions among recombinant proteins, Ag+, and hyaluronic acid (HA). The artificial dermis exhibits long‐lasting broad‐spectrum antibacterial activity, achieved though controlled Ag+ release via Ag─S bonds, supramolecular interactions, and recombinant protein‐guided multi‐level assembly, reaching a steady plateau of 83.7% in the later stage. It is found that inflammation is reduced by downregulating IL‐6 and TGF‐β expression. Furthermore, the epidermal growth factor (EGF) within the recombinant proteins stimulates Col1α, ELN, and CD31 upregulation, facilitating ECM remodeling. These adaptive multifunctional artificial dermis effectively address wound infections, accelerate collagen deposition, promote re‐epithelialization, and enhance angiogenesis in infected wounds, highlighting their potential to revolutionize burn wound treatment and offering a promising avenue to holistic care.

Drug loaded marine polysaccharides-based hydrogel dressings for treating skin burns

Marine polysaccharide-based biomaterials possess a range of excellent functions and properties, such as antiviral, antioxidant, immune regulation, and promoting cell migration, and are widely used in modern medicine. In this study, a marine polysaccharide-based composite hydrogel was synthesized using carboxymethyl chitosan and oxidized fucoidan as matrix, and loads therapeutic drugs for the treatment of burn wounds infected with bacteria. The composite hydrogels can slowly release drugs at the wound site, providing a long-lasting therapeutic effect including antibacterial, antioxidant, and analgesic, in this way to facilitate the restoring of infected burn wounds by inhibiting bacterial infections, promoting cell migration, facilitating collagen regeneration, and restoring the abnormal alteration of factors such as IL-1β and CD86.

Nanoemulsion is an effective antimicrobial for methicillin-resistant Staphylococcus aureus in infected swine skin burn wounds.

The findings of this study are focused on therapeutic applications of nanotechnology. In the current study, we demonstrated that a nanoemulsion formulation could effectively kill methicillin-resistant Staphylococcus aureus (MRSA) infection in porcine skin burn wounds. Infection of MRSA in burn wound is a common threat to public health and is usually difficult to treat due to limited therapies available. NB-201 was effective in significantly alleviating inflammation in the treated wounds and promoting wound healing. Therefore, the finding of this study has a great potential to make this formulation a novel antimicrobial agent against MRSA.

Antibacterial and Healing Efficacy of Mangiferin-Loaded Silver Nanoparticle and Chitosan-Alginate Membrane Dressings

Mangiferin, a bioactive constituent of Mangifera indica (family Anacardiaceae), has an impressive therapeutic profile, having antioxidant, anti-inflammatory, analgesic, antibacterial, and immunomodulatory properties capable of possessing wound healing potential. Our investigation aims to isolate and characterize mangiferin, green synthesis of silver nanoparticles (Ag-NPs) and production of chitosan alginate (Cs/Alg) film dressing loaded with mangiferin Ag-NPs and assess antibacterial and wound-healing properties against infected excision and burn wounds. The isolated mangiferin was authenticated by estimating melting point, thin layer chromatography (TLC), fourier-transform infrared spectroscopy (FTIR), and high-performance liquid chromatography (HPLC). Ag-NPs were green synthesized and characterized by UV-visible, particle size, zeta potential (ZP), entrapment efficiency (%EE), scanning electron microscope (SEM), transmission electron microscope (TEM), and stability study. Chitosan alginate membrane dressing was prepared by incorporating mangiferin Ag-NPs, and film thickness, pH, film weight, water intake capacity, and in-vitro drug release parameters were estimated. Among the four mangiferin Ag-NP batches, MN3 formed stable polydispersity spherical Ag-NPs with smaller particle size and high %EE. Mangiferin-loaded Cs/Alg film MN-CM4 showed significantly higher (p < 0.001) drug content, wettability, release profile, and favorable pH changes. The mangiferin Ag-NPs embedded Cs/Alg film dressing showed a significantly high antimicrobial effect against the gram-positive bacterial strain of S. aureus, commonly found in wounds. MN3 and MN-CM4 treatment showed the shortest epithelialization period and enhanced wound closure. The hydroxyproline content has significantly (p < 0.001) increased, and myeloperoxidase content was reduced by MN3 and MN-CM4 treatment. MN-CM4 treatment showed complete re-epithelialization reduced inflammatory cells with thicker and denser collagen fiber deposition. The effectiveness of the Cs/Alg film of mangiferin Ag-NPs dressing has a synergistic effect on promoting speedy wound healing. The Cs/Alg film of mangiferin Ag-NPs showed rapid wound healing against infected and burned wounds, enhanced collagen synthesis, and anti-inflammatory and antibacterial efficacy.

Bacteriophage therapy reduces Staphylococcus aureus in a porcine and human ex vivo burn wound infection model.

Burn wounds are a major burden, with high mortality rates due to infections. Staphylococcus aureus is a major causative agent of burn wound infections, which can be difficult to treat because of antibiotic resistance and biofilm formation. An alternative to antibiotics is the use of bacteriophages, viruses that infect and kill bacteria. We investigated the efficacy of bacteriophage therapy for burn wound infections, in both a porcine and a newly developed human ex vivo skin model. In both models, the efficacy of a reference antibiotic treatment (fusidic acid) and bacteriophage treatment was determined for a single treatment, successive treatment, and prophylaxis. Both models showed a reduction in bacterial load after a single bacteriophage treatment. Increasing the frequency of bacteriophage treatments increased bacteriophage efficacy in the human ex vivo skin model, but not in the porcine model. In both models, prophylaxis with bacteriophages increased treatment efficacy. In all cases, bacteriophage treatment outperformed fusidic acid treatment. Both models allowed investigation of bacteriophage-bacteria dynamics in burn wounds. Overall, bacteriophage treatment outperformed antibiotic control underlining the potential of bacteriophage therapy for the treatment of burn wound infections, especially when used prophylactically.

Prospects for the application of cell therapy in combustiology

Currently, one of the urgent problems in the field of surgery and traumatology is burn injury. A significant part of the victims has deep and extensive burns, the treatment of which is the most difficult problem of modern combustiology. In this aspect, one of the main problems faced by surgeons in combustiology is the lack of donor material and an increased risk of complications of burn wounds. In this regard, the most promising direction in kombustiology is the application of cell engineering methods, including the use of fibroblasts and stem cells. Fibroblasts have a number of advantages, such as efficiency, safety and accessibility. Stem cells are also a common method of cell therapy, they have great potential in regenerative processes. Mesenchymal stem cells (MSCs), which have a pronounced regenerative and immunosuppressive effect, are also used in kombustiology. In the treatment of infected burn wounds, phage therapy, which provides lysis of infectious pathogens, showed a positive result. In addition to fighting pathogens, bacteriophages, like MSCs, have an immunosuppressive effect, thereby reducing the risk of transplant rejection.

Spreadable thermosensitive nanocomposite hydrogel dressing with ultrasound-responsive bactericidal/repair-promoting regulation and cascade antioxidantion for infected burn wound repair

Treating severe burn wounds poses significant challenges, including considerable cell loss, excessive inflammation, and a high susceptibility to bacterial infections. Ideal burn dressings should exhibit excellent antibacterial properties, anti-inflammatory effects, and promote cell proliferation. Additionally, they need facilitate painless dressing changes and be user-friendly. Herein, we synthesized a thermosensitive hydrogel by crosslinking poly (N-isopropylacrylamide-co-allyloxybenzaldehyde) (PNA) and amino-terminated Pluronic F127 (APF) through a Schiff base reaction. It exhibited reversible gel-sol transition and spreadability. By incorporating piezoelectric gold nanoparticle-modified barium titanate (Au@BaTiO3) and cascade antioxidant MOF-818, a nanocomposite hydrogel dressing with diverse bioactive functionalities was developed. Results demonstrated that the nanocomposite hydrogel possessed gel-sol transition properties, maintained a stable gel state within a broad temperature range, and desirable self-healing property. Au@BaTiO3 exhibited good piezoelectric properties and ROS generation upon ultrasound stimulation, while MOF-818 displayed highly efficient cascade nanozyme activity. The combination of Au@BaTiO3 and MOF-818 promoted fibroblast proliferation and migration, reduced intracellular ROS levels, and induced anti-inflammatory polarization of macrophages under ultrasound stimulation. In vitro and in vivo antibacterial results disclosed that the nanocomposite hydrogel had excellent antibacterial activity under high-intensity ultrasound stimulation. When applied to infected burn wounds, the nanocomposite hydrogel can rapidly sterilize the wound upon initial high-intensity ultrasound, and then reduce inflammation and promote M2 macrophage polarization by the following low-intensity ultrasound stimulation, and thus accelerating the healing by improving granulation tissue formation, angiogenesis, and collagen deposition.

Identification of fungal agents isolated from burn lesions using mycological and molecular methods in patients admitted to Velayat burn hospital in Rasht city during 2022-2023.

Fungal burn wound infections (FBWIs) are one of the most disastrous complications in burn patients. The present study investigated the incidence and the species distribution of fungal agents isolated from burn lesions and reviewed the feautures, underlying conditions, and outcomes of patients. The wounds were swabbed and cultured on Sabouraud Dextrose Agar with chloramphenicol medium. Fungal identification was performed using internal transcribed spacer (ITS) and beta-tubulin sequencing. A total of 380 swab specimens were obtained. Of these, 101 patients (26.75 %) were positive in culture. Among the 101 positive cases, most isolates were from males (n= 68, 67.33%) and most of them were over 30 years old. Flame (n=38, 37.63%) was the predominant cause of burns, and previous history of ICU admission (n=35, 34.66%), presence of central venous catheter (n=25, 24.75%), and diabetes mellitus (n=17, 16.83%) were the main underlying conditions. Candida parapsilosis complex (n=36, 35.64%), and Pichia kudriavzevii (C. krusei) (n=8, 7.92%) represent the most commonly isolated species Also, 2 out of 101 patients (2%) died. In the present study, non-albicans Candida species were much higher frequent than C. albicans with most cases associated with Candida parapsilosis complex.

Inter-Species Competition of Mono- or Dual Species Biofilms- of MDR-Staphylococcus aureus and Pseudomonas aeruginosa Promotes the Killing Efficacy of Phage or Phage Cocktail

Pseudomonas aeruginosa and Staphylococcus aureus are opportunistic bacteria frequently linked to burn wound infections. These bacteria can grow as biofilms, which increases their level of drug resistance to current antibiotics. The purpose of the present study is to analyze the effect of biofilm formation, phage and phage cocktail action on single species and dual species biofilms I, e the coexistence of Gram positive (S. aureus) and Gram negative (P. aeruginosa). To this scenario, we employed multi-drug resistant bacteria (P. aeruginosa and S. aureus at 109 CFU/µL) biofilm as single and in combination of both Gram-positive and Gram-negative bacterial biofilms of 24 h grown with respective phage (109 PFU/µL) and phage cocktail (109 PFU/µL) at 4 h of incubation under static conditions. The bacteriolytic activity of phages vB_SAnS_SADP1 and vB_PAnP_PADP4 on 24-h-old biofilms of P. aeruginosa (0.761 ± 0.031) and S. aureus (0.856 ± 0.055), both alone and in combination (0.67 ± 0.02), was the focus of this investigation. The structural organization of biofilms in single- or dual-species combinations under in vitro conditions was validated by scanning and confocal laser scanning microscopy investigations. After 24 h of incubation, single-species biofilms are denser and more resilient whereas dual species biofilms are more loosely associated. Loose association of dual-species biofilm under scanning electron microscopic images at the same conditions, indicated the interspecies -competition of the Gram-positive and Gram-negative bacteria and dual-species biofilms (0.67 ± 0.02) have weak associations and are readily impacted by phage and a phage cocktail (0.16 ± 0.02). Dual-species biofilms were more readily impacted in in vitro settings.

Biofilm-associated Multi-drug Resistant Bacteria Among Burn Wound Infections: A Cross-sectional Study

Biofilm-associated Multi-drug Resistant Bacteria Among Burn Wound Infections: A Cross-sectional Study

ANTIMICROBIAL WOUND DRESSINGS FOR FULL-THICKNESS INFECTED BURN WOUNDS.

Infection of wounds delays healing, increases treatment costs, and leads to major complications. Current methods to manage such infections include antibiotic ointments and antimicrobial wound dressings, both of which have significant drawbacks, including frequent reapplication and contribution to antimicrobial resistance. In this work, we developed wound dressings fabricated with a medical-grade polyurethane coating composed of natural plant secondary metabolites, cinnamaldehyde, and alpha-terpineol. Our wound dressings are easy to change and do not adhere to the wound bed. They kill gram-positive and -negative microbes in infected wounds due to the Food and Drug Administration-approved for human consumption components. The wound dressings were fabricated by dip coating. Antimicrobial efficacy was determined by quantifying the bacteria colonies after a 24 h of immersion. Wound healing and bacterial reduction were assessed in an in vivo full-thickness porcine burn model. Our antimicrobial wound dressings showed a > 5-log reduction (99.999%) of different gram-positive and gram-negative bacteria, while maintaining absorbency. In the in vivo porcine burn model, our wound dressings were superior to bacitracin in decreasing bacterial burden during daily changes, without interfering with wound healing. Additionally, the dressings had a significantly lower adhesion to the wound bed. Our antimicrobial wound dressings reduced the burden of clinically relevant bacteria more than commercial antimicrobial wound dressings. In an in vivo infected burn wound model, our coatings performed as well or better than bacitracin. We anticipate that our wound dressings would be useful for the treatment of various types of acute and chronic wounds.

Associated bacterial and fungal infections in burn wounds: Common factors, distribution in etiology, age groups, bacterial and fungal strands – Evaluation of a single burn center experience of 20 years

IntroductionBurn intensive care unit (BICU) patients suffer from reduced immunological competence. Often bacterial and fungal infections occur as single or associated infection of the burn site. However, common factors in associated infections are discussed controversially. In this study we evaluated factors common in associated occurrence of bacterial and fungal infection in the burn population. Patients and methodsIn total 213 patients, admitted to the ICU of Cologne Merheim Clinical Center between 1988 and 2011, with associated infections were included in this study. Exclusion criteria were no bacterial, or no fungal infection, or incomplete data. Data evaluated were sex, age, type of burn injury, total body surface area (TBSA), abbreviated burn severity index (ABSI) score, 3rd degree burn, inhalation injury, length of BICU stay, antibiotic therapy, bacterial strand, fungal strand, incidence of bacteria and fungus infection, single or associated occurrence and bacteria species associated with fungus species. Statistical analysis comprised of univariate, Chi-square and Fischer Exact test, multivariate analysis, positive and negative predictive value, logistic regression analysis with the Nagelkerke, Cox/ Snell R-square. Results196 patients were included into the study, 147 male and 49 female. Total mean age was 47 years, in the fire burn group 47 years, in scalding 53 years, in electrical burn 29 years and in chemical burn 62 years. 123 male and 45 female were combusted, 15 male and 3 female scalded, 9 male had an electrical burn and 1 female a chemical burn. The mean TBSA in fire burns was 41 %, in scalding 42 %, in electrical burns 46 %, and in chemical burn 16 %. The mean ABSI in fire burn and scalding was 9, in electrical burn 8 and in chemical burn 7. The 3rd degree burns were 16 % in fire burn and 13 % in scalding and electrical burn and 0 % in chemical burn. The length of BICU stay was 49 days for fire burn, 47 days for scalding, 58 days in electrical burn and 21 days in chemical burn patients.The gram-positive bacterial strands most often found were Staphylococcus strands, gram negative Pseudomonas and Acinetobacter strands. Candida albicans was the most often present fungal strand. There was no difference in incidence between gram positive and gram-negative bacteria. In patients suffering from fire burns the most common bacteria were Staphylococcus and Pseudomonas, in scalding Acinetobacter, and in chemical burns Staphylococcus. In electrical burns no predominant bacterial strand was found. The associated occurrence of Staphylococcus and Candida albicans and Pseudomonas and Candida albicans was predominant. In patients with fire burn, 48% showed an associated infection, in scalding 21%, in electrical burn 33% and in chemical burn 100%.Combusted patients had the highest incidence of associated infection in age group 80–89 years, in scalding 40–49, 50–59 and 70–79 years, in electrical burn 20–29 years and in chemical burn 60–69 years. Most common factors of associated infections were higher age, high TBSA with 3rd degree burns and bacterial infections. Interestingly inhalation injury was highly inversely correlated to associated infection. ConclusionThe associated occurrence of bacterial and fungal wound infection is highest in burn patients with infections with Staphylococcus or Pseudomonas, the incidence is mainly found in fire burn and electrical burns. The use of oxygen in inhalation injury might prevent associated bacterial and fungal infections.

Amino Acid-Conjugated Polymer-Silver Bromide Nanocomposites for Eradicating Polymicrobial Biofilms and Treating Burn Wound Infections.

The rise in antimicrobial resistance, the increasing occurrence of bacterial, and fungal infections, and the challenges posed by polymicrobial biofilms necessitate the exploration of innovative therapeutic strategies. Silver-based antimicrobials have garnered attention for their broad-spectrum activity and multimodal mechanisms of action. However, their effectiveness against single-species or polymicrobial biofilms remains limited. In this study, we present the fabrication of polymer-silver bromide nanocomposites using amino acid conjugated polymers (ACPs) through a green and water-based in situ technique. The nanocomposite architecture facilitated prolonged and controlled release of the active components. Remarkably, the nanocomposites exhibited broad-spectrum activity against multidrug-resistant (MDR) human pathogenic bacteria (MIC = 2-16 μg/mL) and fungi (MIC = 1-8 μg/mL), while displaying no detectable toxicity to human erythrocytes (HC50 > 1024 μg/mL). In contrast to existing antimicrobials and silver-based therapies, the nanocomposite effectively eradicated bacterial, fungal, and polymicrobial biofilms, and prevented the development of microbial resistance due to their membrane-active properties. Furthermore, the lead polymer-silver bromide nanocomposite demonstrated a 99% reduction in the drug-resistant Pseudomonas aeruginosa burden in a murine model of burn wound infection, along with excellent in vivo biocompatibility.

Epidemiological pattern and genomic insights into multidrug-resistant ST491 Acinetobacter baumannii BD20 isolated from an infected wound in Bangladesh: Concerning co-occurrence of three classes of beta lactamase genes

ObjectiveMultidrug-resistant (MDR) Acinetobacter baumannii is a major issue within healthcare facilities in Bangladesh due to its frequent association with hospital-acquired infections. In this study we report on a carbapenem-resistant draft genome sequence of an A. baumannii BD20 sample isolated from an infected wound in Bangladesh. MethodsA. baumannii BD20 was isolated from an infected burn wound. Whole-genome sequencing was carried out and annotated using PGAP and Prokka. Sequence type, antimicrobial resistance genes, virulence factor genes, and metal resistance genes were investigated. Core genome multilocus sequence typing–based phylogenomic analysis between A. baumannii BD20 and 213 A. baumannii strains retrieved from the NCBI GenBank database was performed using the BacWGSTdb 2.0 server. ResultsA. baumannii BD20 (MLST 491) was resistant to all the antibiotics tested, except for colistin and polymyxin B. Along with many other antibiotic resistance genes, the isolate harbored three classes of beta lactamase–producing genes: blaGES-11 (class A), blaOXA-69 (class D), blaADC-10 (class C), and blaADC-11 (class C). Additionally, the strain carried several virulence genes and metal resistance determinants, which may contribute to its increased virulence. Core genome MLST–based phylogenomic analysis revealed that A. baumannii BD20 was closely related to another ST491 strain isolated from Singapore. ConclusionsThe findings of this study underscore the growing challenge of MDR A. baumannii, emphasizing the need for vigilant surveillance and infection-control measures in healthcare settings in order to address these emerging threats effectively.

Inside-out, antimicrobial resistance mediated by efflux pumps in clinical strains of Acinetobacter baumannii isolated from burn wound infections.

Acinetobacter baumannii belongs to the ESKAPE group. It is classified as a critical priority group by the World Health Organization and a global concern on account of its capacity to acquire and develop resistance mechanisms to multiple antibiotics. Data from the United States indicates 500 deaths annually. Resistance mechanisms of this bacterium include enzymatic pathways such as ß-lactamases, carbapenemases, and aminoglycoside-modifying enzymes, decreased permeability, and overexpression of efflux pumps. A. baumannii has been demonstrated to possess efflux pumps, which are classified as members of the MATE family, RND and MFS superfamilies, and SMR transporters. The aim of our work was to assess the distribution of efflux pumps and their regulatory gene expression in clinical strains of A. baumannii isolated from burned patients. METHODS: From the Clinical Microbiology Laboratory at the Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra collection in Mexico, 199 strains were selected. Antibiotics susceptibilities were performed by broth microdilutions to determine minimal inhibitory concentrations. Phenotypic assays with efflux pump inhibitors were conducted using carbonyl cyanide 3-chlorophenylhydrazone (CCCP) and phenylalanine-arginine ß-naphthylamide (PAßN) in conjunction with amikacin, ceftazidime, imipenem, meropenem and levofloxacin. A search was conducted for structural genes that are linked to efflux pumps, and the relative expression of the adeR, adeS, and adeL genes was analyzed. RESULTS: Among a total of 199 strains, 186 exhibited multidrug resistance (MDR). Fluoroquinolones demonstrated the highest resistance rates, while minocycline and amikacin displayed comparatively reduced resistance rates (1.5 and 28.1, respectively). The efflux activity of fluorquinolones exhibited the highest phenotypic detection (from 85 to 100%), while IMP demonstrated the lowest activity of 27% with PAßN and 43.3% with CCCP. Overexpression was observed in adeS and adeL, with adeR exhibiting overexpression. Concluding that clinical strains of A. baumannii fromour institution exhibited efflux pumps as one of the resistance mechanisms.

Development of novel antimicrobials with engineered endolysin LysECD7-SMAP to combat Gram-negative bacterial infections

BackgroundAmong the non-traditional antibacterial agents in development, only a few targets critical Gram-negative bacteria such as carbapenem-resistant Pseudomonas aeruginosa, Acinetobacter baumannii or cephalosporin-resistant Enterobacteriaceae. Endolysins and their genetically modified versions meet the World Health Organization criteria for innovation, have a novel mode of antibacterial action, no known bacterial cross-resistance, and are being intensively studied for application against Gram-negative pathogens.MethodsThe study presents a multidisciplinary approach, including genetic engineering of LysECD7-SMAP and production of recombinant endolysin, its analysis by crystal structure solution following molecular dynamics simulations and evaluation of antibacterial properties. Two types of antimicrobial dosage forms were formulated, resulting in lyophilized powder for injection and hydroxyethylcellulose gel for topical administration. Their efficacy was estimated in the treatment of sepsis, and pneumonia models in BALB/c mice, diabetes-associated wound infection in the leptin receptor-deficient db/db mice and infected burn wounds in rats.ResultsIn this work, we investigate the application strategies of the engineered endolysin LysECD7-SMAP and its dosage forms evaluated in preclinical studies. The catalytic domain of the enzyme shares the conserved structure of endopeptidases containing a putative antimicrobial peptide at the C-terminus of polypeptide chain. The activity of endolysins has been demonstrated against a range of pathogens, such as Klebsiella pneumoniae, A. baumannii, P. aeruginosa, Staphylococcus haemolyticus, Achromobacter spp, Burkholderia cepacia complex and Haemophylus influenzae, including those with multidrug resistance. The efficacy of candidate dosage forms has been confirmed in in vivo studies. Some aspects of the interaction of LysECD7-SMAP with cell wall molecular targets are also discussed.ConclusionsOur studies demonstrate the potential of LysECD7-SMAP therapeutics for the systemic or topical treatment of infectious diseases caused by susceptible Gram-negative bacterial species and are critical to proceed LysECD7-SMAP-based antimicrobials trials to advanced stages.