Infection control in the burn unit

A Nomogram of Predicting Healthcare-Associated Infections in Burned Children

BACKGROUND

Healthcare-associated infections (HAIs) are a common clinical concern associated with adverse prognosis and mortality in burned children. This study aimed to construct a predictive nomogram of the risk of HAIs in burned children.

METHODS

Children admitted to the burn unit of Wuhan Third Hospital between 2020 and 2022 were included. The univariate and multivariate logistic regression analyses were adopted to ascertain predictors of HAIs. A nomogram was developed to predict the HAI risk of each patient, with receiver operating characteristic curves and calibration curves being generated to assess its predictive ability. Furthermore, decision and impact curves were used to assess the clinical utility.

RESULTS

Of 1122 burned children, 61 (5.5%) patients experienced HAIs. The multivariate analysis indicated that total burn surface area, length of stay, surgery, central venous catheter use and urinary catheter use were the independent risk factors of HAIs. Using these variables, we developed a predictive nomogram of the occurrence of HAIs in burned children, and the internal validation results demonstrated good discrimination and calibration of the nomogram. The area under the curve values of the nomogram was 0.926 (95% CI, 0.896-0.957). The calibration curve showed high consistency between the actual and predicted HAIs. The decision and impact curve indicated that the nomogram was of good clinical utility and more credible net clinical benefits in predicting HAIs.

CONCLUSIONS

The present study constructed a nomogram for predicting the risk of HAIs in burned children. This nomogram may strengthen the effective screening of patients at high risk of HAIs.

Multi-state evaluation of Candida infections in burn patients

BACKGROUND

Burn patients are at high risk of developing secondary invasive fungal infections due to their compromised skin barrier, extensive use of antibiotics, and immunosuppression.

OBJECTIVES

We investigated demographic characteristics and clinical factors associated with Candida infections in intensive care unit (ICU) burn patients, and the in vitro antifungal susceptibility of species of isolates.

METHODS

A total of 353 burn patients admitted to three major ICUs of burn centers in Iran were evaluated between 2021 and 2023. Patients were considered as colonisation and candidemia. Demographic characteristics, burn-related factors, and clinical conditions were compared among the groups. Furthermore, we identified fungi at the species level and performed antifungal susceptibility testing according to CLSI guidelines.

RESULTS

Overall, 46.2% of patients were colonised with a Candida species, leading to candidemia in 15.3%. The most frequently isolated species from candidemia and burn wound colonisation were Candida parapsilosis (37.0%) and Candida albicans (31.9%), respectively. Risk factors linked to candidemia included larger total body surface area (TBSA) (>50%), older patients, indwelling catheters, diabetes, and an extended ICU stay. Mortality rate was higher among candidemia patients (82.5%) compared to colonised patients (7.3%). The resistance rate of the strains isolated from candidemia to fluconazole and voriconazole was 28% and 18.2%, respectively.

CONCLUSION

We found that a higher percentage of TBSA burn injuries, longer hospital stays, and catheterization are important predictors of candidemia. The mortality rate was significantly higher in people infected with non-albicans Candida species. Prevention and treatment strategies for candidemia should be based on updated, regional epidemiological data.

Antimicrobial, Anti-inflammatory, and Wound Healing Properties of Myrtus communis Leaf Methanolic Extract Ointment on Burn Wound Infection Induced by Methicillin-Resistant Staphylococcus aureus in Rats

Materials and Methods

In a research experiment, 48 male Wistar rats were anesthetized and second-degree burns were induced on their backs. The rats' wounds were then uniformly inoculated with MRSA. Various treatments were applied to the burn wounds daily, including Myrtus ointment, silver nanoparticles, silver nanoparticles-Myrtus ointment, silver sulfadiazine-Myrtus ointment, silver sulfadiazine 1%, mupirocin ointment, and a positive control. The study measured the antimicrobial effects, wound area, percentage of wound healing, antioxidant capacities, malondialdehyde, and nitric oxide concentrations in the serum of the rats. Data analysis was performed using GraphPad software, with one-way ANOVA and Tukey's tests used to determine the statistical significance of the results.

Results

Rats treated with Myrtus ointment, silver nanoparticles-Myrtus ointment, and mupirocin had reduced bacterial growth compared to the positive control group, nanoparticle ointment, and silver sulfadiazine (P < 0.05). The wound area of the Myrtus ointment group decreased significantly on the seventh and fourteenth days, as well as the level of MDA and nitric oxide, compared to the other groups. In Myrtus and silver sulfadiazine-Myrtus ointment increased the thickness of the epidermis and dermis compared to the other groups.

Conclusion

Based on the anti-inflammatory, antimicrobial, and wound healing properties of Myrtus, with further studies, an ointment of this plant may be used as a main or complementary treatment for burn wound infections caused by MRSA.

Impacts of intelligent monitoring technology installation and additional modalities on hand hygiene compliance in a burn center: A quasi-experimental longitudinal trial

BACKGROUND

The increasing development of intelligent technologies for hand hygiene (HH) compliance audit has the potential to create an alternative to direct observation (DO), which is still considered the gold standard but has disadvantages such as lack of standardized monitoring practices, Hawthorne effect, insufficient sample size, and time/resource consumption. We aimed to share our preliminary results on the impacts of intelligent monitoring technology installation (IMTI) and additional modalities on healthcare workers' (HCWs') HH compliance in a Burn Center, according to the "5 Moments of HH" concept defined by the World Health Organization (WHO).

METHODS

A quasi-experimental longitudinal trial was conducted over eleven months.The first phase of the three-stage study evaluated basic HH compliances obtained by DO. The system-defined HH performances, which IMTI recorded, were assessed in the second phase. Finally, the effect of IMTI and additional modalities was determined in the third stage.

RESULTS

15202 HH events were performed by 41 HCWs, and a total of 20095 HH opportunities were observed. Four hundred fifty-five opportunities were in the preinstallation phase, and 19640 were during the total post-installation period. IMTIdefined performance rates in both Phase 2 (71.2%) and Phase 3 (80.5%) were generally considerably higher than HH compliances obtained from DO (58.5%). Nurses, physical therapy /anesthesia technicians, and housekeeping personnel showed significant increases, which was insignificant in physicians in phase 2. Meanwhile, a sustained increase was observed regarding IMTI and additional modalities of HH compliance of all HCWs in Phase 3.

CONCLUSION

IMTI has significantly increased HH performance rates. Furthermore, combining the IMTI with additional modalities as components of a multimodal strategy recommended by WHO appears to affect the sustainability of the increasing trend of HCWs' HH compliance.

Surviving Sepsis After Burn Campaign

INTRODUCTION

The Surviving Sepsis Campaign was developed to improve outcomes for all patients with sepsis. Despite sepsis being the primary cause of death after thermal injury, burns have always been excluded from the Surviving Sepsis efforts. To improve sepsis outcomes in burn patients, an international group of burn experts developed the Surviving Sepsis After Burn Campaign (SSABC) as a testable guideline to improve burn sepsis outcomes.

METHODS

The International Society for Burn Injuries (ISBI) reached out to regional or national burn organizations to recommend members to participate in the program. Two members of the ISBI developed specific "patient/population, intervention, comparison and outcome" (PICO) questions that paralleled the 2021 Surviving Sepsis Campaign [1]. SSABC participants were asked to search the current literature and rate its quality for each topic. At the Congress of the ISBI, in Guadalajara, Mexico, August 28, 2022, a majority of the participants met to create "statements" based on the literature. The "summary statements" were then sent to all members for comment with the hope of developing an 80% consensus. After four reviews, a consensus statement for each topic was created or "no consensus" was reported.

RESULTS

The committee developed sixty statements within fourteen topics that provide guidance for the early treatment of sepsis in burn patients. These statements should be used to improve the care of sepsis in burn patients. The statements should not be considered as "static" comments but should rather be used as guidelines for future testing of the best treatments for sepsis in burn patients. They should be updated on a regular basis.

CONCLUSION

Members of the burn community from the around the world have developed the Surviving Sepsis After Burn Campaign guidelines with the goal of improving the outcome of sepsis in burn patients.

Infections in Burn Patients

Infections are the leading cause of mortality in burn patients who survive their initial resuscitation. Burn injury leads to immunosuppression and a dysregulated inflammatory response which can have a prolonged impact. Early surgical excision along with support of the multidisciplinary burn team has improved mortality in burn patients. The authors review diagnostic and therapeutic challenges as well as strategies for management of burn related infections.

Changes in Burn Wound Microbiology Profile Over 14 Years of an Adult Tertiary Burn Center

Burn wound colonization can progress to invasive infection. During 14 years of this study, the burn center was relocated to a center with improved infrastructure. This study investigates the association that infrastructure, geography, and time may have on colonization. Data were collected from October 2004 to August 2018, and relocation took place in June 2010, defining the two study periods. Admission swabs were within 48 hours. Unique isolates and resistance data were analyzed and compared statistically between the two study periods. In total, 2001 patients with 24,226 wound swabs were included. Median age was 45.4 (IQR 30.2-61.6), length of stay was 11 days (IQR 6-21), and %TBSA was 5.5 (IQR 2.5-11). Staph. aureus (33.7/100 patients) and Pseudomonas spp. (13.1/100 patients) were the most prevalent bacterial growths. After admission, the prevalence of methicillin resistant Staph. aureus, Coliform spp., and Aci. baumanni was greater in the first site, and Candida spp. colonization was higher in the second study period site. The prevalence of patients affected by multi-drug-resistant organisms was lower in the second study site (13.5/100 patients vs 16.6/100 patients; P < .05). There are differences in burn wound colonization across time, within the same region. Candida spp. growth has been shown to be increased over time and represents an added challenge. Awareness facilitates effective empirical antimicrobial therapies and protocols locally.

Biofilms: Formation, Research Models, Potential Targets, and Methods for Prevention and Treatment

Due to the continuous rise in biofilm-related infections, biofilms seriously threaten human health. The formation of biofilms makes conventional antibiotics ineffective and dampens immune clearance. Therefore, it is important to understand the mechanisms of biofilm formation and develop novel strategies to treat biofilms more effectively. This review article begins with an introduction to biofilm formation in various clinical scenarios and their corresponding therapy. Established biofilm models used in research are then summarized. The potential targets which may assist in the development of new strategies for combating biofilms are further discussed. The novel technologies developed recently for the prevention and treatment of biofilms including antimicrobial surface coatings, physical removal of biofilms, development of new antimicrobial molecules, and delivery of antimicrobial agents are subsequently presented. Finally, directions for future studies are pointed out.

Infections in Burn Patients: A Retrospective View over Seven Years

Backgroundand objectives: Burn patients represent a challenging cohort because the injuries entail a vulnerability to colonisation by microorganisms. The ensuing infections can lead to serious complications and, in many cases, to the death of the burn patient. Surgical intervention and wound dressings, as well as antibiotic treatment, are crucial for optimising the treatment of the patient. Materialand Methods: In this retrospective analysis, we analysed the treatment course, antibiotic therapy, and general complications of 252 burn patients with second- or third-degree burns over a time span of 7 years. Results: Patients who developed infections tended to have, on average, a higher total body surface area (TBSA), higher abbreviated burn severity index (ABSI) scores, and longer hospital stays. Patients who were admitted to the burn unit after 2006 had significantly shorter stays in the burn unit. TBSA and ABSI scores were lower in the patient cohort admitted after 2006. Patients exhibiting a TBSA greater than 30% had significantly longer hospital stays and antibiotic treatment periods. TBSA and ABSI scores were significantly higher in patients who died. The results of binary logistic regression indicate that a higher ABSI score increases the odds ratio of developing an infection. Bacteria number had no significant effect on the odds of patient death but positively influenced the odds ratio of developing an infection. TBSA was negatively associated with the risk of developing an infection and was an insignificant predictor of mortality. Conclusions: To gauge the optimal treatment for a burn patient, it is crucial for practitioners to correctly select, dose, and time antibiotics for the patient. Monitoring bacterial colonisation is vital to nip rising infection in the bud and ensure the correct antibiotic selection. This will help prevent the development of multi-resistant bacteria.

Epidemiology of bloodstream infections and surface swab cultures in burn patients

Aim

For infection control in burn patients, it is essential to understand the epidemiology of bloodstream infection (BSI) and the local microbiological situation. There are few studies on blood and swab culture results among burn patients in Japan. The purpose of this study was to investigate the epidemiology of BSI and swab cultures in burn patients.

Methods

Data from 355 burn patients over 13 years from 2008 were analyzed retrospectively. Bloodstream infection was defined as the isolation of bacteria or fungi from two or more blood cultures. The characteristics of burn patients and microorganisms detected from various cultures were analyzed.

Results

The mortality rate among burn patients with BSI was 37.8%, which was more than twice that among burn patients without BSI. The univariate analysis showed that inhalation injury, total burn surface area (TBSA), and mortality were associated with BSI. The multivariate logistic analysis indicated that TBSA was an independent risk factor for BSI. The most frequently isolated organism from blood and swab cultures were Candida species and Pseudomonas aeruginosa, respectively. Seventy‐five percent of the microorganisms isolated from blood were detected previously in swab cultures performed within 1 week from blood cultures.

Conclusions

The prognosis of burn patients with BSI was poor, and TBSA was an independent risk factor for BSI. The predominant organisms isolated from blood and swab cultures were Candida species and P. aeruginosa, respectively. Surveillance wound swab cultures could be utilized for monitoring the local microbiological situation in burn patients.

Preparation of Silver Ion Antimicrobial Dressings and Prevention and Treatment of Central Venous Catheter-Related Infection on Burn Wounds of Critically Burned Patients

To further understand the characteristics of Ag+ antimicrobial dressings and its application value in the prevention and treatment of infections in burn patients, in the study, the Ag+ gel dressings were prepared and their physical and chemical characteristics were analyzed, and relationship between the gel dressing and central venous catheter (CVC)-related infections was further explored. The results showed that silver nitrate was made into nano silver particles, and its structure was clearly visible under microscope, and nano silver was further applied to preparation of Ag+ antibacterial dressings. Fibrocytes were clearly visible in Ag+ gel dressing and arranged uniformly, which indicated that Ag+ gel dressing had good compatibility with biological materials and had no obvious toxicity. Further clinical trials showed that Ag+ gel dressing can effectively reduce CVC-related infections. From 1 to 4 weeks of the experiment, the bacterial infection rate in burn wounds and blood of the treatment group (TG), which applied Ag+ gel dressing, was lower than the control group (P < 0.05). During the treatment, the burn healing rate of the TG was also greatly higher than the control group (P < 0.05). In addition, the burn wound exudate in the TG was greatly less than the control group (P < 0.05). In summary, the Ag+ gel dressing prepared has good biological and physical and chemical properties, which have bright prospects in the prevention and treatment of burn wounds and CVC-related infections. This study provides an experimental basis for clinical application of Ag+ gel dressing.

Molecular study of metallo-β-lactamases and integrons in Acinetobacter baumannii isolates from burn patients

BACKGROUND

Productions of metallo-β-lactamases enzymes are the most common mechanism of antibiotic resistance to all beta-lactam classes (except monobactams) in Acinetobacter baumannii. MBLs are usually associated with gene cassettes of integrons and spread easily among bacteria. The current study was performed to detect the genes encoding MBLs and integron structures in A. baumannii isolates from burn patients.

METHODS

This study was performed on 106 non-duplicate A. baumannii isolates from burn patients referred to Shahid Motahari Hospital in Tehran. Antibiotic susceptibility of A. baumannii isolates was performed using disk diffusion and broth microdilution method in accordance with the CLSI guidelines. The presence of class 1 integron and associated gene cassettes as well as MBLs-encoding genes including bla_VIM, and bla_IMP were investigated using PCR and sequencing techniques.

RESULTS

In this cross-sectional study all (100%) of the A. baumannii isolates examined were multidrug resistant. All isolates were sensitive to colistin and simultaneously all were resistant to imipenem. PCR assays showed the presence of bla_VIM and bla_IMP genes in 102 (96.2%) and 62 (58.5%) isolates of A. baumannii respectively. In addition, 62 (58.5%) of the A. baumannii isolates carried integron class 1, of which 49 (79.0%) were identified with at least one gene cassette. Three types of integron class 1 gene cassettes were identified including: arr2, cmlA5, qacE1 (2300 bp); arr-2, ereC, aadA1, cmlA7, qacE1 (4800 bp); and aac(3)-Ic, cmlA5 (2250 bp).

CONCLUSION

A high prevalence of MBLs genes, especially bla_VIM, was identified in the studied MDR A. baumannii isolates. In addition, most of the strains carried class 1 integrons. Furthermore, the gene cassettes arrays of integrons including cmlA5 and cmlA7 were detected, for the first time, in A. baumannii strains in Iran.

Anti-flagellin IgY antibodies protect against Pseudomonas aeruginosa infection in both acute pneumonia and burn wound murine models in a non-type-specific mode

Pseudomonas aeruginosa (PA) is one of the most dominant causes of nosocomial infections in burn patients. Increasing emergence of antibiotic-resistant strains highlights the need for novel antimicrobial agents. Flagellin, the main component protein of flagellum, is determined as the major antigen interacting with anti-P. aeruginosa IgY antibodies. The current study was aimed to evaluate the antibacterial potency of IgY antibodies raised against recombinant type A, and B flagellins. The immunogenicity and specificity of IgY antibodies were confirmed through indirect ELISA and western blot analysis, respectively. Anti-flagellin IgYs reduced the motility, biofilm formation and invasion potency of both strains. The cell surface hydrophobicity (CSH) of bacteria was increased upon IgY treatment, and in vitro opsonophagocytosis assay confirmed the high protective potency of specific antibodies via polymorphonuclear leukocyte (PMN)-augmented bacterial cell killing. The protective efficacy of IgYs was also studied in both acute pneumonia and burn wound murine models. Anti-flagellin B-IgY induced 100 % and 40 % protection against laboratory, and hospital strains in burn wound model, respectively. Protection in acute pneumonia against all strains was 100 %. Anti-flagellin A-IgY failed to protect mice in burn wound model, but provided 100 % protection against all strains in acute pneumonia challenge. In vitro, ex vivo and in vivo experiments confirmed the dose-dependent and non-type specific essence of anti-flagellin IgY antibodies, providing the benefit of covering all strain types in a dose dependent manner. Our findings provide evidence that anti-flagellin IgY antibodies qualify as novel economical therapeutic option against PA infection.

Burn Center Referral Practice Evaluation and Treatment Outcomes Comparison Among Verified, Nonverified Burn Centers, and Nonburn Centers: A Statewide Perspective

The American Burn Association (ABA) has developed comprehensive referral criteria to determine which burn-injured patient should be transferred to burn centers. This was a retrospective analysis of burn injuries using Illinois inpatient and outpatient hospital data from 2010 to 2015. Multivariable logistic and linear regression models were developed to evaluate ABA burn center referral criteria adherence and to compare treatment outcomes among those treated in verified burn center (VB), nonverified burn center (NVB), and other facilities (OF). In this study, 66% of those treated in facilities without specialized burn teams met the ABA referral criteria. Patients who were older than the age of 40 years, lived farther from burn units, and were originally treated in level I trauma center without burn units were less likely to be transferred to burn centers. Those transported and treated in burn centers had overall better treatment outcomes including fewer infection complications (VB vs OF: adjusted odds ratio [aOR]: 0.5, 95% confidence interval [CI]: 0.4-0.6; NVB vs OF: aOR: 0.5, 95% CI: 0.4-0.6), fewer patients requiring additional care in skilled nursing/rehabilitation facilities (VB vs OF: aOR: 0.5, 95% CI: 0.4-0.6; NVB vs OF: aOR: 0.7, 95% CI: 0.6-0.9), shorter length of hospitalization (VB vs OF: β: -0.4, P < .001; NVB vs OF: β: -0.8, P < .001), and comparable in-hospital mortality (VB vs OF: aOR: 1.3, 95% CI: 0.97-1.7; NVB vs OF: aOR: 1.01, 95% CI: 0.7-1.5). While verified and unverified burn centers demonstrated better treatment outcomes, the data demonstrated a need to understand the barriers of adhering to ABA criteria and an improved regional burn center referral guidelines education.

Association of TLR4 gene polymorphisms with sepsis after a burn injury: findings of the functional role of rs2737190 SNP

Sepsis is a life-threatening organ dysfunction condition caused by a dysregulated response to an infection that is common among patients with moderate to severe burn injury. Previously, genomic variants in Toll-like receptor 4 (TLR4), a key innate immunity receptor, have been associated with sepsis and infection susceptibility. In this study, the association of six TLR4 SNPs with sepsis after burn injury was tested in the Mexican mestizo population. We found that the rs2737190 polymorphism is associated with sepsis after burn trauma. Interestingly, the G allele and GG genotype were associated with a lower risk of developing sepsis. Since the rs2737190 SNP is in the promoter region of the TLR4 gene, we analyzed the possibility that this polymorphism regulates the TLR4 pathway. We cultured peripheral blood mononuclear cells from different genotype carriers and found, after stimulation with LPS, that carriers of the GG genotype showed a higher expression of TLR4, IL6, and TNFα than AA genotype carriers. The results suggest that the GG genotype produces an increase in the TLR4 expression, and therefore an improvement in the immune response. We conclude that the rs2737190 polymorphism may become a useful marker for genetic studies of sepsis in patients after a burn injury.

Burn Unit Design-The Missing Link for Quality and Safety

The relationship between infrastructure, technology, model of care, and human resources influences patient outcomes and safety, staff productivity and satisfaction, retention of personnel, and treatment and social costs. This concept underpins the need for evidence-based design and has been widely adopted to inform hospital infrastructure planning. The aim of this review is to establish evidence-based, universally applicable key features of a burn unit that support function in a comprehensive patient-centered model of care. A literature search in medical, architectural, and engineering databases was conducted. Burn associations' guidelines and relevant articles published in English, between 1990 and 2020, were included, and the available evidence is summarized in the review. Few studies have been published on burn unit design in the past 30 years. Most of them focus on the role of design in infection control and prevention and consist primarily of descriptive or observational reports, opportunistic historical cohort studies, and reviews. The evidence available in the literature is not sufficient to create a definitive infrastructure guideline to inform burn unit design, and there are considerable difficulties in creating evidence that will be widely applicable. In the absence of a strong evidence base, consensus guidelines on burn unit infrastructure should be developed, to help healthcare providers, architects, and engineers make informed decisions, when designing new or renovated facilities.

Nanoparticle-functionalized dressings for the treatment of third-degree skin burns - histopathological and immunohistochemical study

Skin burns are one of the most common injuries associated with increased morbidity and mortality, especially in the children and the elderlies. Severe burns, especially, result in a systemic immune and inflammatory response, which may reflect in multiple organ insufficiency, and a fast and effective local restorative process is essential for functionality recovering, as well as for interrupting the generalized systemic response. We have aimed here to assess the effect of different wound dressings in what it regards the morphology and clinical restoration after a skin burn. On a rat animal model, we have evaluated the macroscopic and histopathological features of controlled third degree skin burns in control animals versus treatments with local dressings of silver sulfadiazine (SDA) cream, simple gel (G), gel + silver nanoparticles (AgNPs) (G+NPS), gel + exosomes (G+EXO) and gel + AgNPs + exosomes (Gel+NPS+EXO), at 14 days and, respectively, 21 days after the lesion. Tissue fragments were harvested and processed for histopathology and immunohistochemistry. Immunofluorescence was utilized to evaluate the maturity of underlaying granulation tissue based on double stainings for smooth muscle actin (SMA) and cluster of differentiation 31 (CD31). Our study showed variability in what it regards the vessel density and immunoexpression of SMA between the treatments, and image analysis revealed that most SMA reduction and blood vessel density reduction in the maturing granulation tissue occurred for the G+NPS and G+NPS+EXO treatments. A complete re-epithelization was also observed for the G+NPS+EXO treatment. Overall, our results show that improved topic treatments promote faster re-epithelization and reparation of the dermis after skin burn lesions, providing thus an avenue for new treatments that aim both local recuperation and systemic infection prevention.

Synergistic effect of fennel essential oil and hydrogen peroxide on bacterial biofilm

Introduction

Staphylococcal biofilm formation significantly challenges wound management. The causes of difficult-to-treat wounds are not only methicillin-resistant staphylococci, but also methicillin-sensitive strains with different patterns of resistance. Bacterial biofilm significantly limits the access and activity of antimicrobials used in dermatological infections.

Aim

To evaluate the synergistic effect of fennel essential oil (FEO) and H₂O₂ on biofilm formation by Staphylococcus aureus (MSSA and MRSA) reference strains.

Material and methods

Minimum inhibitory concentration (MIC) values were determined for FEO and H₂O₂ against S. aureus reference strains by the broth microdilution method. The combined effects of the FEO and H₂O₂ were calculated and expressed in terms of a fractional inhibitory concentration index (FICI) using the checkerboard method. The FEO composition was analyzed by the GC-MS method. The data were analysed by one-way ANOVA.

Results

Decreased MIC values for FEO combined with H₂O₂ were observed in comparison to FEO itself. The combinations of FEO and H₂O₂ determined synergistic effects on all S. aureus reference strains. Subinhibitory concentration of FEO alone and in combination with 0.5 MIC of H₂O₂ significantly decreased the production of biofilm biomass in S. aureus strains and reduced the metabolic activity of attached cells.

Conclusions

Combination of fennel essential oil containing nearly 80% trans-anethole and H₂O₂ represents a potential for further basic and applied research on wound management.

Outcomes in Burn-Injured Patients Who Develop Sepsis

This study examines health outcomes in burn patients with sepsis. We hypothesized that burn patients with sepsis would have an increased odds risk for in-hospital death and longer intensive care unit (ICU) stays. This was a retrospective cohort of consecutive patients admitted to the burn ICU with total BSA (TBSA) ≥10% and/or inhalation injury between January 2008 and March 2015. Overall 407 burn patients were included; the case-rate for sepsis was 39.1% (n = 159); 20.1% (n = 82) patients were septic and 18.9% (n = 77) patients experienced septic shock. Patients with septic shock had the highest mortality rate (13.31% no sepsis vs 3.7% sepsis vs 49.4% septic shock, P < .01). Median 28-day ICU-free days was higher in patients without sepsis (23 days [Interquartile range (IQR) 14-27] no sepsis vs 0 days [IQR 0-10] sepsis vs 0 days [IQR 0-0] septic shock, P < .01). Sepsis (with or without shock) increased odds of in-hospital death (odds ratio 7.04, 95% confidence interval 1.93-25.7) in reference to the no sepsis group. With each incremental Sequential Organ Failure Assessment (SOFA) score or 10% TBSA increase, the odds risk for in-hospital death increased by 56 and 75%, respectively. Our study characterized outcomes in patients with sepsis after severe burn injury. The odds risk for in-hospital death was greater in patients with sepsis, increasing burn severity according to TBSA and SOFA score.

Innovations in Infection Prevention and Treatment

Background: Patients with large, acute burn injuries are a major challenge for clinicians. The loss of skin barrier protection against micro-organisms combined with the induced immunosuppression after burn injury makes this population especially vulnerable to infection. For burn-injured patients who survive immediate management considerations and burn resuscitation after acute injury, sepsis remains the primary cause of death. The purpose of this article is to describe current strategies and innovations in burn sepsis prevention and management. Methods: This work reviews the current understanding of the systemic inflammatory response to burn injury and burn sepsis as well as current strategies in insolation and infection prevention, newer burn unit design strategies in the context of infection prevention, and novel therapies being considered in topical antimicrobial wound care management. Results: A review of burn sepsis is key to understanding current paradigms and innovation in burn management and prevention. Key management principles begin from the time of injury and persist throughout the patient's hospital course. This includes use of personal protective equipment, burn unit design considerations, and knowledge of critical care principles such as central venous catheter management strategies. Innovations on wound dressing types, forms, and use have been key to better controlling burn wound sepsis and improving wound healing. Products incorporating nanotechnology, novel anions, oxygen, and even light have been key to introducing previously unconsidered methods to fight or prevent infection. Conclusion: Understanding the pathophysiology and source identification of sepsis from burn wounds has been a key contributor in developing innovative prevention and therapeutic strategies in burn management. The emergence of drug-resistant pathogens and the difficulty of systemic antibiotic agents to reach poorly vascularized wounds have further reinforced the need to anticipate management strategies moving forward. A proactive, multidisciplinary approach is necessary to minimize the morbidity and mortality associated with infection control.

Multi-Drug-Resistant Organisms in Burn Infections

Background: Infection is the most frequent complication after severe burns and remains the predominant cause of death. Burn patients may require multiple courses of antibiotics, lengthy hospitalizations, and invasive procedures that place burn patients at especially high risk for infections with multi-drug-resistant organisms (MDROs). Methods: The published literature on MDROs in burn patients was reviewed to develop a strategy for managing these infections. Results: Within a burn unit meticulous infection prevention and control measures and effective antimicrobial stewardship can limit MDRO propagation and decrease the antibiotic pressure driving the selection of MDROs from less resistant strains. Several new antimicrobial agents have been developed offering potential therapeutic options, but familiarity with their benefits and limitations is required for safe utilization. Successful management of MDRO burn infections is supported by a multifactorial approach. Novel non-antibiotic therapeutics may help combat MDRO infections and outbreaks. Conclusions: Multi-drug-resistant organisms are being identified with increasing frequency in burn patients. Effective sensitivity testing is essential to identify MDROs and to direct appropriate antibiotic choices for patient treatment.

Three Year Study of Infection Profile and Antimicrobial Resistance Pattern from Burn Patients in Southwest Iran

Introduction

Burn wound infections, as one of the most important risk factors, cause serious complications in burns. Hence, the focus of medical care should be preventing infections and resistant isolates. The current study investigates the prevalence of infectious agents and antimicrobial resistance patterns during three years.

Materials and Methods

A total of 960 isolates were collected from different sample kinds cultured for 615 burn patients who were hospitalized during January 2016 to December 2018 in Amir-Al-Momenin Burn Center. The type of microorganism and their antibiotic resistance patterns were identified by microbiological tests and the standard disk-diffusion method according to the introduced standard techniques.

Results

Incidence of positive growth was seen more in males than in females. Most of the burns encountered were due to flame injuries (35.4%). Based on the diversity of bacterial isolates, Pseudomonas aeruginosa was the most frequent pathogen (49.9%), followed by Klebsiella sp. (9.7%), Acinetobacter sp. (7.2%) and Staphylococcus aureus (6.5%). The trend of resistance of meropenem was declining in P. aeruginosa isolates. Klebsiella sp. as the second most prevalent agent showed a high level of resistance to the studied antibiotics. The antibiogram results for S. aureus isolates showed an increasing trend in MRSA isolates.

Conclusion

By evaluating the infectious agent, it was found that although frequencies of microorganisms and resistant isolates were a little high, performing a multidisciplinary approach controls the trend during the study period. These achievements have been gained due to a strict politicized infection control and stewardship program in the appointed burn center.

Cost-drivers of medical expenses in burn care management

BACKGROUND

Profound differences exist in the cost of burn care globally, thus we aim to investigate the affected factors and to delineate a strategy to improve the cost-effectiveness of burn management.

METHODS

A retrospective analysis of 66 patients suffering from acute burns was conducted from 2013 to 2015. The average age was 26.7 years old and TBSA was 42.1% (±25.9%). We compared the relationship between cost and clinical characteristics.

RESULTS

The estimated cost of acute burn care with the following formula (10,000 TWD) = -19.80 + (2.67 × percentage of TBSA) + (124.29 × status of inhalation injury) + (147.63 × status of bacteremia) + (130.32 × status of respiratory tract infection).

CONCLUSION

The majority of the cost were associated with the use of antibiotics and burns care. Consequently, it is crucial to prevent nosocomial infection in order to promote healthcare quality and reduce in-hospital costs.

New Nanotechnologies for the Treatment and Repair of Skin Burns Infections

Burn wounds are highly debilitating injuries, with significant morbidity and mortality rates worldwide. In association with the damage of the skin integrity, the risk of infection is increased, posing an obstacle to healing and potentially leading to sepsis. Another limitation against healing is associated with antibiotic resistance mainly due to the use of systemic antibiotics for the treatment of localized infections. Nanotechnology has been successful in finding strategies to incorporate antibiotics in nanoparticles for the treatment of local wounds, thereby avoiding the systemic exposure to the drug. This review focuses on the most recent advances on the use of nanoparticles in wound dressing formulations and in tissue engineering for the treatment of burn wound infections.

Variability in Management of Patients With SJS/TEN: A Survey of Burn Unit Directors

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are rare, type IV hypersensitivity reactions of the skin and mucosa. These reactions (SJS/TEN) are frequently managed in burn units; however, no standardized guidelines exist for the treatment and management of SJS/TEN. To gain insight into current SJS/TEN management practices, a survey on admission, diagnosis, and management, was conducted across accredited burn units in the United States. A 28-item question survey on SJS/TEN management, diagnosis, and treatment practices was distributed among medical directors and co-directors of American Burn Association-verified burn centers. Responses were collected over a 6-week period. In total, 31 (48% response rate) burn unit medical directors/co-directors participated in the survey. The majority of responders indicate that acceptance to their burn unit is based on clinical suspicion of SJS/TEN (74%), and biopsy or dermatological evaluation is not required (67 and 87%, respectively). More than half (61%) of the burn units have their own SJS/TEN protocol in place. No consensus was observed on different treatment aspects, such as infection control, systemic treatment, and wound care. Most directors reported their burn units to consult ophthalmology (77%) and dermatology (54%) for the management of patients with SJS/TEN. Large variability in procedures of admission, treatment, and management of SJS/TEN was identified across burn centers. This study demonstrates the urgent need for SJS/TEN standardized guidelines in the United States.

The relation between positive screening results and MRSA infections in burn patients

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) is a key pathogen in burn patients. Several factors put them at increased risk of MRSA infection: partial loss of the skin barrier, the immune-compromising effects of burns, prolonged hospital stays, and invasive procedures. This study aims to find the relation between MRSA screening swab cultures taken within 48 h of admission, weekly surveillance cultures, and MRSA infection secondary to colonization.

METHODS

The data of all burns patients admitted to the referral centre for burns from 2012 to 2016 were reviewed. MRSA cultures taken at admission and on weekly surveillance screening, including nasal, perianal, and wound swabs, were reviewed. To determine associations between MRSA colonization and infection rates, both MRSA-positive and MRSA-negative swab cultures were included in the analysis. Several risk factors were considered: age, gender, ethnicity, %TBSA, BAUX index, inhalational injury, ICU admission and days, need for ventilator support and days, length of stay (LOS) in hospital, and complications. Univariate and multiple logistic regression analyses were used to predict correlations between positive swab cultures and risk factors.

RESULTS

Data from 396 patients were reviewed. The median age at admission for the burn patients was 46 (IQR: 31-59) years. On admission, 2.5% of patients were MRSA positive, whereas 17.9% were found to be MRSA positive on weekly surveillance screening. At surveillance, 60.6% developed an infection secondary to MRSA colonization. An MRSA infection was not identified for any patient who did not have at least one positive admission or surveillance swab. A statistically significant association was found between any positive swab and MRSA infection (P < 0.001). The median number of complications reported in the MRSA-positive group was 2 (IQR: 1-3) versus 0 (IQR: 0-1) in the MRSA-negative group and the median length of hospital stay in the MRSA-positive group was 34.5 (IQR: 20.25-56.25) days versus 7 (IQR: 3-16) days in the MRSA-negative group (P < 0.001).

CONCLUSION

Nosocomial MRSA colonization rates are high, and patients incurring infections experience a greater than average LOS in hospital and complications. Over 60% of patients who had a positive swab culture at surveillance developed an infection, whereas, no patient with a negative MRSA swab status developed an infection. Hence, pragmatic prevention strategies have to be implemented.

Antibiofilm Potential of Silver Sulfadiazine-Loaded Nanoparticle Formulations: A Study on the Effect of DNase-I on Microbial Biofilm and Wound Healing Activity

Biofilm resistance is one of the severe complications associated with chronic wound infections, which impose extreme microbial tolerance against antibiotic therapy. Interestingly, deoxyribonuclease-I (DNase-I) has been empirically proved to be efficacious in improving the antibiotic susceptibility against biofilm-associated infections. DNase-I hydrolyzes the extracellular DNA, a key component of the biofilm responsible for the cell adhesion and strength. Moreover, silver sulfadiazine, a frontline therapy in burn wound infections, exhibits delayed wound healing due to fibroblast toxicity. In this study, a chitosan gel loaded with solid lipid nanoparticles of silver sulfadiazine (SSD-SLNs) and supplemented with DNase-I has been developed to reduce the fibroblast cytotoxicity and overcome the biofilm-imposed resistance. The extensive optimization using the Box-Behnken design (BBD) resulted in the formation of SSD-SLNs with a smooth surface as confirmed by scanning electron microscopy and controlled release (83%) for up to 24 h. The compatibility between the SSD and other formulation excipients was confirmed by Fourier transform infrared, differential scanning calorimetry, and powder X-ray diffraction studies. Developed SSD-SLNs in combination with DNase-I inhibited around 96.8% of biofilm of Pseudomonas aeruginosa as compared to SSD with DNase-I (82.9%). In line with our hypothesis, SSD-SLNs were found to be less toxic (cell viability 90.3 ± 3.8% at 100 μg/mL) in comparison with SSD (Cell viability 76.9 ± 4.2%) against human dermal fibroblast cell line. Eventually, the results of the in vivo wound healing study showed complete wound healing after 21 days' treatment with SSD-SLNs along with DNase-I, whereas marketed formulations SSD and SSD-LSNs showed incomplete healing after 21 days. Data in hand suggest that the combination of SSD-SLNs with DNase-I is an effective treatment strategy against the biofilm-associated wound infections and accelerates wound healing.

MRSA colonization and acquisition in the burn unit: A systematic review and meta-analysis

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most commonly encountered bacteria in the burn unit. In order to investigate the magnitude of this challenge, we assessed the prevalence of MRSA colonization on admission and the incidence of MRSA acquisition within burn units.

METHODS

We searched PubMed and EMBASE for studies reporting MRSA colonization among patients admitted in burn units.

RESULTS

We identified 16 articles that fulfilled our inclusion criteria and found an overall pooled prevalence of MRSA colonization upon the first 72 h of admission (colonization on admission) to the burn unit of 4.1% (95% CI: 2.7%-5.7%). MRSA acquisition in studies without a decolonization protocol was 21.2% (95% CI: 13.2%-30.5%) with a statistically significant downward trend over the years. Studies that implemented a decolonization protocol yielded a MRSA acquisition incidence rate of 4.5% (95% CI: 0.9%-10.6%). MRSA acquisition was higher among patients that have had inhalation injury (OR 3.96, 95% CI: 2.51-6.23), flame burns (OR 1.85, 95% CI: 1.25-2.73), or ICU admission (OR 3.12, 95% CI: 2.18-4.47).

CONCLUSION

Our study yielded that among burn victims, MRSA colonization prevalence on admission is not negligible and the risk of becoming MRSA colonized during hospitalization is higher when no decolonization protocols are implemented. Flame burns, admission to ICU, and inhalation injury were found to be associated with MRSA acquisition.

Epidemiology, Bacteriological Profile, and Antibiotic Sensitivity Pattern of Burn Wounds in the Burn Unit of a Tertiary Care Hospital

INTRODUCTION

 Burn wounds are commonly infected by organisms which delay wound healing. Therefore, it is necessary to evaluate the flora obtained from wounds of burn patients in order to determine the most effective treatment. The aim of this study was to determine the frequencies of various bacteria isolated from burn wounds and to determine their antimicrobial susceptibility.  Materials and methods: This descriptive cross-sectional study was conducted from January 2018 to November 2018 which included consecutive samples of burn wounds from patients admitted to the burn ward of a tertiary care hospital. Bacteria and their antimicrobial susceptibility were determined by swab cultures and sensitivity tests by standard aseptic techniques. Data were analysed via the Statistical Package for Social Sciences (SPSS), v23.0 (IBM SPSS Statistics, Armonk, NY). Chi-square tests were applied between qualitative variables, while the Kruskal-Wallis test was applied to compare the means of asymmetrical data. Bacterial isolates and their susceptibility pattern were represented as frequencies and pie charts.

RESULTS

 A total of 178 samples were obtained from 109 patients from burn wounds. One hundred and twenty-two wounds (68.5%) showed growth and 56 (31.4%) showed no growth after 24 hours of incubation. Positive cultures were significantly more frequent in wounds of greater than one-week duration (p < 0.002). Out of 158 bacterial isolates, the most common isolate was Pseudomonas aeruginosa - 41 specimens (24.91%), followed by Staphylococcus aureus - 38 specimens (24.05%), Acinetobacter - 27 (17.09%), Klebsiella - 24 (15.19%), Escherichia coli - 13 (8.23%), Proteus - 7 (4.43%), other coliforms - 6 (3.8%), Enterococcus - 1 (0.63%), and Enterobacter - 1 (0.63%). Drug resistance to penicillin G, ampicillin, Augmentin, ceftazidime, cefotaxime, ceftriaxone, meropenem, and piperacillin+tazobactam was exceptionally high.

CONCLUSION

 The most common bacterial isolates are Pseudomonas aeruginosa and Staphylococcus aureus. Piperacillin+tazobactam against Pseudomonas aeruginosa and vancomycin and linezolid against Staphylococcus aureus are highly effective and can be used as empirical therapies.

Candidemia in major burn patients and its possible risk factors: A 6-year period retrospective study at a burn ICU

OBJECTIVE

The aims of this study were to evaluate the epidemiological and clinical characteristics of candidemia in a typical burn ICU, and to determine the risk factors associated with candidemia among major burn patients.

METHOD

This retrospective observational study of candidemia from 2012 to 2017 in a burn ICU was conducted in the Department of Burn, Southwest hospital, Chongqing, China.

RESULTS

The study included 410 major burn patients (≥40% total body surface area), 39 (9.51%) of which were diagnosed with candidemia. The annual incidences of candidemia varied from 6.06% to 17.54%, and increased gradually in the 6 years. Candida parapsilosis was the dominant pathogen (28.21% strains). The overall resistance rate of Candida spp. to fluconazole was 35.89%. Candidemia cases most frequently occurred in the 2nd (30.77%) and 3rd (23.08%) weeks after burn, and intravascular catheters were the most common sources of bloodstream Candida infections (31.58%). The crude mortality of candidemia was 23.08%, and the mortality attributable to candidemia was 14.99%. Risk factors of candidemia included inhalation injury, renal dysfunction with replacement therapy, severe gastrointestinal complications, T-cell lymphopenia and prior Candida colonization.

CONCLUSION

Candidemia has a high incidence and mortality in major burn patients. The changes in etiology and drug sensitivity may make new challenges for the management of candidemia in burn ICUs.

Infection Prevention: Unique Aspects of Burn Units

BACKGROUND

Infection is a common complication of burn injury caused by the loss of skin (the primary defense against micro-organisms) as well as burn-induced immunosuppression. Essentially, survival after burn injury is determined by whether wound healing or infection predominates. The purpose of this article is to describe how burn unit structure and design may impact the incidence of infection after burn injury.

METHODS

This article describes the special considerations for burn unit structure and design based on burn pathophysiology, including burn-related immunosuppression and wound treatment. Particular emphasis is placed on how burn unit design should consider the immunosuppressed state of the burn patient.

RESULTS

Because many of the factors that promote wound healing also promote infection, burn unit design must prioritize infection prevention, including segregation and containment, environment layout and function, room cleaning, and isolation. Burn centers should have dedicated facilities with separation of patients, specialized room environment/equipment, and cleaning and wound care disinfection capabilities, with particular attention paid to surfaces, ventilation, temperature control, and patient movement to the operating room, radiology, and therapy.

CONCLUSIONS

Because of the high infection potential associated with burn injury, burn units require meticulous attention to design and function to minimize patient infection risk.

Acinetobacter - the trojan horse of infection control?

BACKGROUND

Five cases of multi-resistant Acinetobacter baumanii (MRA) producing OXA-23 and OXA-51 occurred in a regional burn intensive care unit (BICU). Three were repatriated from other parts of the world (Dubai and Mumbai) and colonized on admission. Despite optimal precautions, two patients acquired MRA. Both had been nursed in the same room.

METHODS

Multi-disciplinary outbreak investigation of MRA in a regional BICU.

FINDINGS

The mechanism of transfer for the first case is thought to have been contaminated air from theatre activity releasing MRA bacteria into the communal corridor. No MRA patients went to theatre between the first and second acquired cases. The mechanism of transfer for the second case is thought to have been via a shower unit that was decontaminated inadequately between patients.

CONCLUSION

In an outbreak where contact precautions and environmental cleaning are optimal, it is important to give careful consideration to other mechanisms of spread. If there is a failure to do this, it is likely that the true causes of transmission will not be addressed and the problem will recur. It is recommended that burn theatres within burn facilities should be designed to operate at negative pressure; this is the opposite of normal operating theatre ventilation. Where showers are used, both the shower head and the hose should be changed after a patient with a resistant organism. The role of non-contact disinfection (e.g. hydrogen peroxide dispersal) should be reconsidered, and constant vigilance should be given to any 'trojan horse' item in the room.

Common hydrotherapy practices and the prevalence of burn wound bacterial colonisation at the University Teaching Hospital in Lusaka, Zambia

BACKGROUND

In many parts of the world, hydrotherapy plays an important role in the management of patients with wounds including burns. Different centers practice hydrotherapy differently. At the University Teaching Hospital in Lusaka, Zambia, burn patients use a common bathtub for cleaning their wounds which theoretically increases the risk of cross-infection, an important source of morbidity and mortality. There is currently no evidence that hydrotherapy as practiced at our institution leads to cross infection among patients with burns.

OBJECTIVE

The objective was to determine if our hydrotherapy practice and water plays a role in cross-infection and what organisms cause this infection.

METHODS

This was a prospective analytical study. Patients meeting the selection criteria were recruited. Swabs from the burn wounds were collected on admission (day 0), day 4 and day 7. Weekly swabs of the bathtub were also collected, after the tub had been cleaned and declared ready for the next patient. Weekly water samples were also collected. Selected results, for Staphylococcus aureus and Klebsiella pneumoniae, were subjected to further analysis and PCR. Results were analyzed using statistics software, SPSS version 23.

RESULTS

In this study, there were 96 participants of which 51 (53.1%) were males and 45 (46.9%) were females. Age distribution ranged from 5months to 91 years. The modal age range was 1 to 2 years. The modal burn percentage was 6%-10%, followed by 11%-15%. Hot water was the cause of burns in 65.6%. S. aureus and K. pneumoniae were the most common organisms isolated. Others were enteric organisms. In terms of readily available antibiotics, there was more sensitivity to Amikacin and Chloramphenicol than Ciprofloxacin (our commonly used antibiotic). The bathtub also had S. aureus and K. pneumoniae, besides enteric organisms. Sixty five point four percent (65.4%) of the Klebsiella were ESBL (Extended Spectrum Beta Lactamase) producers. The tub had samples that were both ESBL producers as well as widely resistant Klebsiella by other means. No growth was obtained from the water samples. Seventy-two point nine percent (72.9%) of the patients were discharged, 19.8% died, while 7.3% left against medical advice.

CONCLUSION

Hydrotherapy as currently practiced at the University Teaching Hospital does contribute significantly to cross-infection among burn patients with widely resistant organisms. The main ones are S. aureus and K. pneumoniae. Switching care to a shower mechanism might help eliminate this problem as the study demonstrates that no bacteria were found in the water samples.

After standard dosage of piperacillin plasma concentrations of drug are subtherapeutic in burn patients

Infections are a major problem in patients with burn diseases. Mortality is high despite antibiotic therapy as studies are controversial concerning drug underdosing. The aims of this prospective, observational study were to monitor plasma concentrations of piperacillin during standard piperacillin/tazobactam treatment in 20 burn patients and 16 controls from the intensive care unit (ICU) and to optimize doses by in silico analyses. Piperacillin/tazobactam (4/0.5 g, tid) was administered over 0.5 h. Blood samples were taken at 1, 4, and 7.5 h after the end of the infusion. Free piperacillin plasma concentrations were determined. Pharmacokinetic parameters and in silico analysis results were calculated using the freeware TDMx. The primary target was defined as percentage of the day (fT_>1xMIC; fT_>4xMIC) when piperacillin concentrations exceeded 1xMIC/4xMIC (minimum inhibitory concentration), considering a MIC breakpoint of 16 mg/L for Pseudomonas aeruginosa. In an off-label approach, two burn patients were treated with 8/1 g piperacillin/tazobactam, 3 h qid. fT_>1xMIC (55 ± 22% vs. 77 ± 24%) and fT_>4xMIC (17 ± 11% vs. 30 ± 11%) were lower in burn than in ICU patients after 4/0.5 g, 0.5 h, tid. In silico analyses indicated that fT_>1xMIC (93 ± 12% burn, 97 ± 4% ICU) and fT_>4xMIC (62 ± 23% burn, 84 ± 19% ICU) values increase by raising the piperacillin dosage to 8/1 g qid and prolonging the infusion time to 3 h. Off-label treatment results were similar to in silico data for burn patients (84%fT_>1xMIC and 47%fT_>4xMIC). Standard dosage regimens for piperacillin/tazobactam resulted in subtherapeutic piperacillin concentrations in burn and ICU patients. Dose adjustments via in silico analyses can help to optimize antibiotic therapy and to predict respective concentrations in vivo. Trial registration: NCT03335137, registered 07.11.2017, retrospectively.

Development of a High-Throughput ex-Vivo Burn Wound Model Using Porcine Skin, and Its Application to Evaluate New Approaches to Control Wound Infection

Biofilm formation in wounds is considered a major barrier to successful treatment, and has been associated with the transition of wounds to a chronic non-healing state. Here, we present a novel laboratory model of wound biofilm formation using ex-vivo porcine skin and a custom burn wound array device. The model supports high-throughput studies of biofilm formation and is compatible with a range of established methods for monitoring bacterial growth, biofilm formation, and gene expression. We demonstrate the use of this model by evaluating the potential for bacteriophage to control biofilm formation by Staphylococcus aureus, and for population density dependant expression of S. aureus virulence factors (regulated by the Accessory Gene Regulator, agr) to signal clinically relevant wound infection. Enumeration of colony forming units and metabolic activity using the XTT assay, confirmed growth of bacteria in wounds and showed a significant reduction in viable cells after phage treatment. Confocal laser scanning microscopy confirmed the growth of biofilms in wounds, and showed phage treatment could significantly reduce the formation of these communities. Evaluation of agr activity by qRT-PCR showed an increase in activity during growth in wound models for most strains. Activation of a prototype infection-responsive dressing designed to provide a visual signal of wound infection, was related to increased agr activity. In all assays, excellent reproducibility was observed between replicates using this model.

A Proof-of-Concept Study of the Efficacy of Systemically Administered Polymyxins in Mouse Burn Wound Infection Caused by Multidrug-Resistant Gram-Negative Pathogens

The efficacy of subcutaneously administered polymyxins against burn wound infections caused by Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae was examined in a murine infection model. Subcutaneously administered colistin and polymyxin B (30 mg/kg thrice daily) achieved a ≥2-log10 reduction in the bacterial load for P. aeruginosa and A. baumannii infections, whereas wound infections by K. pneumoniae were less responsive (<1-log10 reduction). This study highlights the potential therapeutic benefits of parenteral polymyxins for treating burn wound infections.

Evolution of carbapenem resistance in Acinetobacter baumannii during a prolonged infection

Acinetobacter baumannii is a common causative agent of hospital-acquired infections and a leading cause of infection in burns patients. Carbapenem-resistant A. baumannii is considered a major public-health threat and has been identified by the World Health Organization as the top priority organism requiring new antimicrobials. The most common mechanism for carbapenem resistance in A. baumannii is via horizontal acquisition of carbapenemase genes. In this study, we sampled 20 A. baumannii isolates from a patient with extensive burns, and characterized the evolution of carbapenem resistance over a 45 day period via Illumina and Oxford Nanopore sequencing. All isolates were multidrug resistant, carrying two genomic islands that harboured several antibiotic-resistance genes. Most isolates were genetically identical and represented a single founder genotype. We identified three novel non-synonymous substitutions associated with meropenem resistance: F136L and G288S in AdeB (part of the AdeABC efflux pump) associated with an increase in meropenem MIC to ≥8 µg ml⁻¹; and A515V in FtsI (PBP3, a penicillin-binding protein) associated with a further increase in MIC to 32 µg ml⁻¹. Structural modelling of AdeB and FtsI showed that these mutations affected their drug-binding sites and revealed mechanisms for meropenem resistance. Notably, one of the adeB mutations arose prior to meropenem therapy but following ciprofloxacin therapy, suggesting exposure to one drug whose resistance is mediated by the efflux pump can induce collateral resistance to other drugs to which the bacterium has not yet been exposed.

Local Burn Injury Promotes Defects in the Epidermal Lipid and Antimicrobial Peptide Barriers in Human Autograft Skin and Burn Margin: Implications for Burn Wound Healing and Graft Survival

Burn injury increases the risk of morbidity and mortality by promoting severe hemodynamic shock and risk for local or systemic infection. Graft failure due to poor wound healing or infection remains a significant problem for burn subjects. The mechanisms by which local burn injury compromises the epithelial antimicrobial barrier function in the burn margin, containing the elements necessary for healing of the burn site, and in distal unburned skin, which serves as potential donor tissue, are largely unknown. The objective of this study was to establish defects in epidermal barrier function in human donor skin and burn margin, to identify potential mechanisms that may lead to graft failure and/or impaired burn wound healing. In this study, we established that epidermal lipids and respective lipid synthesis enzymes were significantly reduced in both donor skin and burn margin. We further identified diverse changes in the gene expression and protein production of several candidate skin antimicrobial peptides (AMPs) in both donor skin and burn margin. These results also parallel changes in cutaneous AMP activity against common burn wound pathogens, aberrant production of epidermal proteases known to regulate barrier permeability and AMP activity, and greater production of proinflammatory cytokines known to be induced by AMPs. These findings suggest that impaired epidermal lipid and AMP regulation could contribute to graft failure and infectious complications in subjects with burn or other traumatic injury.

Isolation and characterization of HepP: a virulence-related Pseudomonas aeruginosa heparinase

Background

Pseudomonas aeruginosa is an opportunistic pathogen that causes serious infections in immunocompromised hosts including severely burned patients. In burn patients, P. aeruginosa infection often leads to septic shock and death. Despite numerous studies, the influence of severe thermal injuries on the pathogenesis of P. aeruginosa during systemic infection is not known. Through RNA-seq analysis, we recently showed that the growth of P. aeruginosa strain UCBPP-PA14 (PA14) in whole blood obtained from severely burned patients significantly altered the expression of the PA14 transcriptome when compared with its growth in blood from healthy volunteers. The expression of PA14_23430 and the adjacent gene, PA14_23420, was enhanced by seven- to eightfold under these conditions.

Results

Quantitative real-time PCR analysis confirmed the enhancement of expression of both PA14_23420 and PA14_23430 by growth of PA14 in blood from severely burned patients. Computer analysis revealed that PA14_23430 (hepP) encodes a potential heparinase while PA14_23420 (zbdP) codes for a putative zinc-binding dehydrogenase. This analysis further suggested that the two genes form an operon with zbdP first. Presence of the operon was confirmed by RT-PCR experiments.

We characterized hepP and its protein product HepP. hepP was cloned from PA14 by PCR and overexpressed in E. coli. The recombinant protein (rHepP) was purified using nickel column chromatography. Heparinase assays using commercially available heparinase as a positive control, revealed that rHepP exhibits heparinase activity. Mutation of hepP resulted in delay of pellicle formation at the air-liquid interface by PA14 under static growth conditions. Biofilm formation by PA14ΔhepP was also significantly reduced. In the Caenorhabditis elegans model of slow killing, mutation of hepP resulted in a significantly lower rate of killing than that of the parent strain PA14.

Conclusions

Changes within the blood of severely burned patients significantly induced expression of hepP in PA14. The heparinase encoded by hepP is a potential virulence factor for PA14 as HepP influences pellicle formation as well as biofilm development by PA14 and the protein is required for full virulence in the C. elegans model of slow killing.

Electronic supplementary material

The online version of this article (10.1186/s12866-017-1141-0) contains supplementary material, which is available to authorized users.

Risk Factors for Healthcare-Associated Infections in Adult Burn Patients

OBJECTIVE Burn patients are particularly vulnerable to infection, and an estimated half of all burn deaths are due to infections. This study explored risk factors for healthcare-associated infections (HAIs) in adult burn patients. DESIGN Retrospective cohort study. SETTING Tertiary-care burn center. PATIENTS Adults (≥18 years old) admitted with burn injury for at least 2 days between 2004 and 2013. METHODS HAIs were determined in real-time by infection preventionists using Centers for Disease Control and Prevention criteria. Multivariable Cox proportional hazards regression was used to estimate the direct effect of each risk factor on time to HAI, with inverse probability of censor weights to address potentially informative censoring. Effect measure modification by burn size was also assessed. RESULTS Overall, 4,426 patients met inclusion criteria, and 349 (7.9%) patients had at least 1 HAI within 60 days of admission. Compared to 6 times as likely to acquire an HAI (HR, 6.38; 95% CI, 3.64-11.17); and patients with >20% TBSA were >10 times as likely to acquire an HAI (HR, 10.33; 95% CI, 5.74-18.60). Patients with inhalational injury were 1.5 times as likely to acquire an HAI (HR, 1.61; 95% CI, 1.17-2.22). The effect of inhalational injury (P=.09) appeared to be larger among patients with ≤20% TBSA. CONCLUSIONS Larger burns and inhalational injury were associated with increased incidence of HAIs. Future research should use these risk factors to identify potential interventions. Infect Control Hosp Epidemiol 2017;38:1441-1448.

Burn Serum Increases Staphylococcus aureus Biofilm Formation via Oxidative Stress

Staphylococcus aureus is a common pathogen isolated from burn patients that can form biofilms on burn wounds and implanted deep vein catheters, which often leads to refractory infections or even biofilm-related sepsis. As biofilm formation is usually regulated by environmental conditions, we hypothesized that serum composition may be altered after burn injury, potentially affecting the ability of infecting bacteria to form biofilms. As predicted, we observed that serum from burn-injured rats increases biofilm formation by S. aureus and also induces bacterial aggregation and adherence to human fibronectin and fibrinogen. Analysis of potential regulatory factors revealed that exposure to burn serum decreases expression of the quorum-sensing agr system and increases mRNA levels of some biofilm inducers such as sarA and icaA. In addition, we also observed that burn serum imposes oxidative stress and increases expression of key oxidoreductase genes (sodA, sodM, katA, and ahpC) in S. aureus. Importantly, the ability of burn serum to enhance biofilm formation and bacterial cell aggregation can be abrogated by treatment with an antioxidant. Taken together, these findings indicate that burn serum increases S. aureus biofilm formation via elevated oxidative stress, and may lead to novel strategies to control biofilm formation and infection in burn patients.