The effect of granulocyte colony-stimulating factor (G-CSF) upon burn-induced defective neutrophil chemotaxis

Severe thermal injury results in impairment of granulocyte production and function. The ability to improve the functional capacity of neutrophils could contribute to a reduced morbidity and mortality from sepsis following thermal injury. Previous studies from this laboratory have shown that rhG-CSF increases the number of femoral marrow granulocyte progenitor cells and circulating neutrophils as well as the survival rate following burn wound infection. The studies reported here examine the effect of in-vivo administration of rhG-CSF on neutrophil chemotaxis following a burn injury and also following superimposed Pseudomonas burn wound sepsis in mice. Casein-elicited peritoneal neutrophils were harvested 72 hours after burn injury and 24 hours after infection. Chemotaxis was assessed using microchemotaxis chambers and 10(-5) M fMet-Phe as a chemoattractant. The number of neutrophils that migrated into the filter was used as an index of directed chemotaxis. Burn injury resulted in depressed chemotaxis compared with sham or sham/G-CSF-treated animals (p less than 0.05). Administration of rhG-CSF to burned animals resulted in a level of neutrophil chemotaxis comparable with that in control animals. The presence of a burn wound infection caused no further impairment of chemotaxis. Administration of rhG-CSF to animals with a burn wound infection resulted in improved chemotaxis compared with sham, burned, and burned/infected animals. The beneficial effect of G-CSF following burn wound infections from this and previous studies appears to be a combination of expanded numbers of myeloid elements and preservation of their function.     

Additive effects of thermal injury and infection on the small bowel

Thermal injury is associated with functional alterations of multiple organ systems, including the gastrointestinal tract. To study the effects of ongoing infection after thermal injury on bowel mass, composition, and blood flow, male Wistar rats were randomized to receive either 30% scald burn, 30% scald burn with Pseudomonas aeruginosa wound inoculation, sham burn, or sham burn with pair feeding to burned and infected animals. On days 3 and 7 after injury, intestinal blood flow was measured with 51Cr-labeled microspheres, and intestinal mass and composition were analyzed. Burned and infected animals demonstrated a chronic loss of small bowel mass not seen in burned animals without infection by day 7 after injury. Compositional alterations of the small bowels of burned and infected animals included protein wasting similar to but occurring earlier than that seen with anorexia alone and significantly decreased deoxyribonucleic acid and ribonucleic acid content, whereas tissue water content remained unchanged. These chronic intestinal alterations in the burned and infected group could not be explained by ongoing ischemia because intestinal blood flow in these animals was not significantly altered at either time point, implying mediation by other pathophysiologic mechanisms.     

Effect of thermal injury with Pseudomonas aeruginosa infection on pulmonary and systemic bacterial clearance

BACKGROUND: Despite improvements in burn wound care, infections, particularly pneumonia, remain a major hurdle to recovery from thermal injury. After burns, a variety of systemic immune and inflammatory changes contribute to the risk of infection. Clinically, infection coupled with burn injury seems to adversely affect susceptibility to subsequent infection. METHODS: Using a mouse model of 10% total body surface area, full-thickness, third-degree burns with quantitative bacterial cultures of multiple tissues, the effect of graded intratracheal and intraperitoneal infections with Pseudomonas aeruginosa on the development of infection was assessed. RESULTS: P. aeruginosa infection of blood and lung were demonstrated in burned mice 4 hours after they received 1 to 7.2x10(5) P. aeruginosa intratracheally but not in unburned control mice. Disseminated infection from endogenous bacterial species (Proteus, Enterococcus, Streptococcus) involving the lungs, liver, blood, and subeschar space was observed in mice that received both burns and infection with P. aeruginosa (intraperitoneally and intratracheally) but not with infection or burn alone (p<0.01). After burns, pulmonary bacterial clearance was delayed in association with both pulmonary infection (7.2x10(5) P. aeruginosa intratracheally) and intraperitoneal infection (10(7) P. aeruginosa intraperitoneally). Histologically, diffuse pneumonitis was observed in mice that received burns and infection but not in mice with either infection or burns alone. CONCLUSION: Small thermal injuries coupled with transient infection of the lungs or peritoneum delay the clearance of bacteria from the lungs and contribute to infection of the lungs, liver, burn site, and blood by endogenous organisms. These studies support the synergy of relatively small thermal injuries with infectious exposures in the pathogenesis of pneumonia and systemic infections after burns.     

Fever as a predictor of infection in burned children

Although children with burns often develop fevers, we have found no reports characterizing the course and duration of these fevers. To evaluate the predictive value of fever as an indicator of infection in burned children, we reviewed the hospital charts of all 223 children admitted to a regional burn center in the years 1979 through 1982. The highest temperature reading for each 8-hour period of the child's hospitalization was recorded. The highest mean temperature in burned children occurred at 38 to 96 hours after the burn injury; the peak temperatures appeared at the same time, regardless of whether the child had an infection. All of the 23 children with infections (100%) and 145 of the 200 without infections (73%) had a recorded temperature reading of 38.2 degrees C or higher within 2 weeks after their burn injury. When children less than 4 years, or children with more than 20% total body surface area burns were considered alone, the presence of a temperature greater than 38.2 degrees C was not significant in differentiating those with infections. Fever is not a specific predictor of infection in burned children; in children less than 4 years of age and in children with more than 20% burns, fever has no predictive value for the presence of infection. The physical examination is a reliable source of information about wound infection, sepsis, or other childhood infections, and should be the primary tool used in making the diagnosis of infection in burned children.     

Investigation and assessment of neutrophil dysfunction early after severe burn injury

BackgroundExtensive burn injury results in a complex immune response that is associated with mortality and prognosis. Studies on acquired immune and the development of sepsis in burn patients have been reported. However, one of the main cells in innate immune, neutrophil dysfunction in the burn shock stage has not been thoroughly characterized.MethodsNeutrophil chemotaxis, expression of neutrophil surface markers (P2X1 receptor, [P2RX1]), degranulation (myeloperoxidase [MPO], heparin-binding protein [HBP], matrix metalloproteinase-9 [MMP-9] and neutrophil elastase [NE]), oxidative burst capacity, neutrophil extracellular trap (NET) generation, phagocytosis and apoptosis were measured in 18 patients with major burns (≥30% total body surface area [TBSA]) within 48 h after burn injury. In addition, circulating neutrophils and vascular permeability in mice model with 30% TBSA third-degree burns were also observed and investigated.ResultsNeutrophil functions were reduced considerably in burn shock stage, which was characterized by decreased chemotaxis, phagocytosis and abnormal bactericidal function. Increased release of heparin-binding protein (HBP) and the expression of P2RX1 on the neutrophil surface are related to fluid leakage and decreased chemotaxis during burn shock stage, respectively. The combination of HBP concentration in plasma and P2RX1 expression on neutrophils gives a better prediction of neutrophil dysfunction in burn-injured patients.ConclusionNeutrophil dysfunction plays a key role in the development of burn injury. Targeting the restoration of neutrophil function may be a feasible therapeutic intervention to help reduce fluid loss during shock and the severity of subsequent infection.     

Recombinant human growth hormone modulates Th1 and Th2 cytokine response in burned mice.

OBJECTIVE: To determine whether growth hormone (GH) influences the production of type 1 T-helper (Th1) and type 2 T-helper (Th2) cytokine responses after burn. SUMMARY BACKGROUND DATA: GH has been shown to influence immunoregulation. The authors previously reported improved mortality in burned mice treated with GH after infection with herpesvirus. Other work has shown that impaired immunity after burn was characterized by conversion of Th cell populations from Th1 cells to Th2 cells, suggesting an increased susceptibility of patients with burns to infection. METHODS: The production of Th1 and Th2 cytokine from isolated splenic lymphocytes taken from GH-treated burned mice was measured. RESULTS: At 1 and 11 days after burn, Th1 cytokine production by splenic lymphocytes from burned mice treated with GH was greater than in mice receiving saline. In fact, Th1 cytokine production was greater than that of nonburned mice. In addition, the production of Th2 cytokines was decreased. CONCLUSIONS: Results suggest that the Th1/Th2 response is altered after burn, and this can be reversed with GH. GH, therefore, may improve resistance to infection in patients with burns.     

Burn Wound Infections: Current Status

Pseudomonas aeruginosa . Even so, effective topical antimicrobial chemotherapy and early burn wound excision have significantly reduced the overall occurrence of invasive burn wound infections. Individual patients, usually those with extensive burns in whom wound closure is difficult to achieve, may still develop a variety of bacterial and nonbacterial burn wound infections. Consequently, the entirety of the burn wound must be examined on a daily basis by the attending surgeon. Any change in wound appearance, with or without associated clinical changes, should be evaluated by biopsy. Quantitative cultures of the biopsy sample may identify predominant organisms but are not useful for making the diagnosis of invasive burn wound infection. Histologic examination of the biopsy specimen, which permits staging the invasive process, is the only reliable means of differentiating wound colonization from invasive infection. Identification of the histologic changes characteristic of bacterial, fungal, and viral infections facilitates the selection of appropriate therapy. A diagnosis of invasive burn wound infection necessitates change of both local and systemic therapy and, in the case of bacterial and fungal infections, prompt surgical removal of the infected tissue. Even after the wounds of extensively burned patients have healed or been grafted, burn wound impetigo, commonly caused by Staphylococcus aureus , may occur in the form of multifocal, small superficial abscesses that require surgical débridement. Current techniques of burn wound care have significantly reduced the incidence of invasive burn wound infection, altered the organisms causing the infections that do occur, increased the interval between injury and the onset of infection, reduced the mortality associated with infection, decreased the overall incidence of infection in burn patients, and increased burn patient survival.     

Effect of aspiration pneumonia-induced sepsis on post-burn cardiac inflammation and function in mice

INTRODUCTION: Numerous studies have found that burn injury alters immune function, predisposing the subject to infectious complications. We developed a mouse model of burn injury complicated by either gram-positive or gram-negative infection and hypothesized that post-burn infection would exacerbate the myocardial cytokine responses and contractile dysfunction characteristic of either sepsis alone or burn alone. METHODS: Adult C57 BL6 mice were given burn injury over 40% of the total body surface area and conventional fluid resuscitation (lactated Ringer's solution, 4 mL/kg/% burn) followed on day 7 by intratracheal administration of 1 x 10(5) cfu of either Streptococcus pneumoniae or Klebsiella pneumoniae or saline. Mice received fluid resuscitation (2 mL of lactated Ringer's intraperitoneally) again after bacterial challenge. Cardiomyocyte cytokine secretion and the contractile function of isolated hearts (Langendorff perfusion) were examined in vitro 24 h after bacterial challenge. RESULTS: Infectious challenge seven days after burn injury exaggerated the inflammatory cytokine responses over those observed with either burn alone or gram-positive or gram-negative infection alone (tumor necrosis factor-alpha: sham, 72 +/- 9 pg/mL; burn alone, 176 +/- 6 pg/mL, Klebsiella pneumoniae alone, 337 +/- 8 pg/mL; Streptococcus pneumoniae alone, 184 +/- 2 pg/mL; burn + Klebsiella, 476 +/- 14 pg/mL; burn + Streptococcus, 351 +/- 6 pg/mL). Myocardial contractile depression was evident in the burn alone, infection alone, and burn plus infection groups, regardless of the organism selected to produce pneumonia-related sepsis. CONCLUSIONS: Gram-negative or gram-positive infection exacerbated the myocardial inflammation seen with burn alone or infection alone. The availability of a mouse model of burn injury complicated by pneumonia-related sepsis will allow use of genetically engineered mice to examine further the mechanisms by which burn injury increases susceptibility to infection.     

Chronic ethanol exposure before injury produces greater immune dysfunction after thermal injury in rats

Chronic alcoholics constitute a small but significant subgroup of burned patients. The effects of chronic alcohol exposure on immune function in burned patients has not to our knowledge been studied. This study was designed to determine the effect of chronic alcohol exposure before burn injury on immune function after injury in rats. Immune function assessed by in vivo chemotaxis and responsiveness of non-adherent splenocytes to both a T-cell mitogen, concanavalin A, and a B-cell mitogen, lipopolysaccharide, was measured at 4 days after a 20% BSA full-thickness burn injury and/or gavage of 2.4 gm/kg/day of ethanol for 14 days. Chronic ethanol ingestion before burn injury produced significant suppression in chemotaxis and response to lipopolysaccharide but not in response to concanavalin A. These results suggest that chronic alcohol exposure before injury can contribute to further impaired immune function after injury, and may lead to increased susceptibility to infection and increased mortality.     

Sodium butyrate inhibits the production of HMGB1 and attenuates severe burn plus delayed resuscitation-induced intestine injury via the p38 signaling pathway

BackgroundInflammatory response triggered by high mobility group box-1 (HMGB1) protein and oxidative stress play critical roles in the intestinal injury after severe burn. Sodium butyrate, a histone deacetylase inhibitor, has potential anti-inflammatory properties, inhibiting the expression of inflammatory mediators such as HMGB1 in diverse diseases. This study was designed to investigate the effects of sodium butyrate on severe burn plus delayed resuscitation-induced intestine injury, intestinal expressions of HMGB1 and intracellular adhesion molecule-1 (ICAM-1), oxidative stress, and signal transduction pathway changes in rats.Materials and methodsFifty-six Sprague-Dawley rats were divided into 3 groups randomly: (1) sham group, animals underwent sham burn; (2) burn group, rats subjected to full-thickness burns of 30% total body surface area (TBSA) and received 2 ml/kg/TBSA lactated Ringer solution for resuscitation at 6, 12, and 36 h after burn injury; (3) burn plus sodium butyrate (burn + SB) group, animals received burn injury and lactated Ringer solution with sodium butyrate inside for resuscitation in the same manner. Diamine oxidase (DAO) concentration in plasma was measured by enzyme-linked immunosorbent assay. Intestinal fatty acid binding protein (I-FABP) and ICAM-1 expressions in the intestine were analyzed by immunohistochemical method. HMGB1 and p38 mitogen-activated protein kinase (MAPK) expressions in the intestine tissues were examined by Western blot. The intestinal concentration of malondialdehyde (MDA) was also determined.ResultsIntestinal HMGB1 expression was significantly increased in burn group compared with sham group. Sodium butyrate administration significantly inhibited the HMGB1 expression in the intestine, decreased the DAO concentration in plasma, reduced the intestinal I-FABP expression, and improved the intestinal histologic changes induced by burn injury plus delayed resuscitation. Sodium butyrate treatment also markedly reduced the increase of intestinal ICAM-1 expression and MDA content, and inhibited p38 MAPK activity in the intestine of severely burned rats with delayed resuscitation.ConclusionsSodium butyrate inhibits HMGB1 expression which could be attributed to p38 MAPK signal transduction pathway and decreases intestinal inflammatory responses and oxidative stress, thus attenuates burn plus delayed resuscitation-induced intestine injury.     

Injury induces deficient interleukin-12 production, but interleukin-12 therapy after injury restores resistance to infection

OBJECTIVE: To assess at serial intervals the production of interleukin-12 (IL-12) by monocytes/macrophages from the peripheral blood of injured patients and control subjects, and using a mouse model to confirm human findings and explore the effectiveness of low-dose IL-12 therapy in restoring resistance to infection after injury. SUMMARY BACKGROUND DATA: Serious injury is associated with loss of function of the T helper 1 lymphocyte phenotype, but little is known about IL-12 production in injured patients. The authors previously reported that early, moderate-dose IL-12 therapy in a mouse model of burn injury restored resistance to a later infectious challenge (cecal ligation and puncture, CLP). However, the efficacy of clinically relevant low-dose IL-12 therapy carried out to or beyond the time of septic challenge remains to be tested. METHODS: Peripheral blood mononuclear cells (PBMCs) and adherent cells were obtained from 27 patients with major burns or traumatic injury and 18 healthy persons and were studied at serial intervals for IL-12 production stimulated by bacterial lipopolysacharide (LPS). PBMCs from 18 of the same patients were studied for IL-10 production as well. IL-12 production by adherent cells from the spleens of burn or sham burn mice was studied at serial intervals after injury to confirm the human findings. Low-dose IL-12 or vehicle was given every other day to groups of burn and sham burn mice, which were then challenged with CLP on day 10, and survival was determined. Finally, spleens were harvested from burn or sham burn animals receiving low-dose IL-12 or vehicle after CLP. After splenic cellularity was determined by hemocytometer, splenocytes were cultured and production of tumor necrosis factor-alpha, interferon-gamma, and IL-10 were assessed by immunoassay. RESULTS: Adherent cells from patients' PBMCs produced significantly less IL-12 than normal PBMCs after injury, reaching a nadir 8 to 14 days after injury. Stimulation of whole PBMCs by LPS indicated that at 8 to 14 days after injury, IL-12 production by PBMCs was significantly lower and IL-10 production was significantly higher than that of PBMCs from healthy persons. Low-dose IL-12 therapy significantly increased survival after CLP. Splenocytes from burn mice treated with IL-12 had significantly increased production of TNF-alpha and IF-beta, both before and after CLP, when compared with vehicle-treated burn animals. IL-10 production by bum splenocytes remained high after IL-12 treatment. Splenic cellularity increased after IL-12 treatment in burn mice. CONCLUSION: The capacity to produce IL-12 by adherent cells of the monocyte/macrophage lineage is significantly reduced after serious injury in humans and in a mouse burn model. In humans, there is a reciprocal relation between diminished IL-12 production and increased IL-10 production at approximately 1 week after injury. Low-dose IL-12 therapy in the mouse burn model markedly increased survival after a septic challenge, even when treatment was carried beyond the onset of sepsis. Low-dose IL-12 treatment in the mouse increased production of proinflammatory mediators important in host defense and at the same time maintained or increased production of IL-10, an important antiinflammatory cytokine.     

Monocyte chemoattractant protein-1 (MCP-1) and macrophage infiltration into the skin after burn injury in aged mice

Clinical observations and laboratory studies have shown a delay in dermal wound healing in aged subjects. Since macrophages play a key role in wound healing, we investigated age related differences in MCP-1 production and monocyte recruitment to the wound following burn injury using a murine model. The present study shows that there is an increase in MCP-1 levels in the burned-normal skin interface at 1-day post burn in both young and aged burned mice compared to sham injured mice. However, the levels of MCP-1 in aged burned mice (133.16+/-36.55pg/mg protein) were approximately half the levels of young burned mice (286.15+/-45.36pg/mg protein, P<0.05). Additionally, at 4 days post burn, MCP-1 levels in aged mice (290.73+/-101.98) reached the same levels as in young mice (243.97+/-36.71). There was no difference in macrophage accumulation into the wound between young and aged at either time point. These data demonstrate that the difference in dermal MCP-1 levels between the young and aged is not associated with a difference in macrophage infiltration to the wound following burn injury, suggesting that the lower MCP-1 content in the aged is possibly affecting other phases of wound healing in the aged.     

Efficacy of locally delivered polyclonal immunoglobulin against Pseudomonas aeruginosa infection in a murine burn wound model.

The leading cause of morbidity and mortality in severe burn wound patients is infection. Treatment of burn wound infection is complicated by the emergence of antibiotic resistant organisms. A potential therapeutic alternative to antibiotic drugs is the local administration of polyclonal antibodies, termed passive local immunotherapy (PLI), directly to the burned tissue. A mouse burn wound infection model to simulate full thickness burn wound infection was used to evaluate the efficacy of passive local immunotherapy as a viable prophylactic or therapeutic agent. Pooled human immunoglobulins (IgG), delivered locally to the site of infection, are shown to be more effective at preventing fatal burn wound sepsis than treatment by intravenous infusion of IgG. A single 10 mg dose of human IgG administered locally to the burned, infected tissue site, either 24 hours prior to bacterial challenge, or within 3 hours after bacterial challenge, enhanced animal survival significantly (P < 0.001 and P < 0.05 respectively) compared to control animals. In addition, reduced levels of bacteria were found in local and systemic tissues of IgG-treated mice compared to control mice (P < 0.05). These data support the local use of polyclonal immunoglobulin preparations as an efficacious and cost effective means to prevent and treat burn wound infections.     

Cachectin/TNF production in experimental burns and Pseudomonas infection

Burn injury and infection result in significant losses of lean tissue. The cytokine cachectin/tumor necrosis factor has been implicated in this process but is not uniformly detected during infection. We sought to determine the relationship between body composition changes and in vivo hepatic levels of pretranslational message for cachectin (messenger RNA) in a burn and infection rodent model. Adult Wistar rats were grouped as follows: (1) freely fed, (2) 30% burn, (3) 30% burn with Pseudomonas aeruginosa infection, (4) pair fed, and (5) 30% burn and infection with recombinant cachectin. Compared with controls or animals only burned, burned and infected rats had a 100% increase in hepatic cachectin messenger RNA content, lost carcass protein, and exhibited muscle loss with sparing of liver mass. Tissue production of cachectin as well as other cytokines may be sufficient to mediate several body composition changes observed in response to injury and infection.     

Incidence of systemic fungal infection and related mortality following severe burns

Advancements in burn care therapy have extended survival of seriously burned patients, exposing burn patients to increased risk of infectious complications, notably fungal infections. We performed a 12-year review of autopsied patients with severe burns for the presence of fungal infection at the US Army Institute of Surgical Research Burn Center between February 1991 and November 2003. The primary goal was to identify the relationship between fungal element noted in autopsy and mortality, and to determine contributing factors that increase a patient's susceptibility to fungal infection. A total of 228 deaths (6.1%) resulted from the 3751 admissions of which 97 underwent autopsy. Fungal elements were identified on histopathology in 44% (43 of 97) of autopsied patients with an attributable mortality of 33% (14 of 43). Aspergillus and Candida were the most frequently recovered fungi, but Aspergillus was recovered in 13 of the 14 cases with fungus identified as an attributable cause of death. The most common sites of infections with attributable mortality were wounds (86%) and the pulmonary system (14%). Total body surface area (TBSA) burn and length of stay (survival after burn) were identified as contributing factors for the incidence of fungal element in autopsy on ROC curve analysis. More severely injured patients with greater %TBSA burn injury and full-thickness burns require a longer recovery period resulting in a longer hospital stay. The propensity for fungal infection increases the longer the wound is present. Therefore, the development of products to close the wound more rapidly, improvement in topical antifungal therapy with mold activity for treating wounds, and implementation of appropriate systemic antifungal therapy may improve outcome for severely injured burn victims susceptible to fungal infections.     

Successful prevention of secondary burn progression using infliximab hydrogel: A murine model

IntroductionBurn injury remains a serious cause of morbidity and mortality worldwide. Severity of burns is determined by the percentage of burned area compared to the body surface area, age of patient, and by the depth of skin and soft tissue involvement; these factors determine management as well as prospective outcomes. The pathophysiology of partial- to full-thickness burn conversion remains poorly understood and is associated with a worse overall prognosis. Recent studies have demonstrated that an altered inflammatory response may play a significant role in this conversion and therefore a reduction in early inflammation is crucial to ultimately decreasing burn severity and morbidity. We hypothesize that the application of a microcapillary gelatin–alginate hydrogel loaded with anti-TNF-α (infliximab) monoclonal antibodies to a partial-thickness burn will reduce inflammation within partially burned skin and prevent further progression to a full-thickness burn.MethodsAssembly of the microfluidic hydrogels is achieved by embedding microfibers within a hydrogel scaffold composed of a gelatin–alginate blend, which is then soaked in a solution containing anti-TNF-α antibodies for drug loading. 12 young (2–4 months) and 12 old (>16 months) mice were given partial thickness burns. The treatment cohort received the anti-TNF-α infused hydrogel with an occlusive dressing and the control cohort only received an occlusive dressing. Mice were euthanized at post-burn day 3 and skin samples were taken. Burn depth was evaluated using Vimentin immunostaining.ResultsAll mice in the treatment cohort demonstrated decreased conversion of burn from partial to full thickness injury (old = p < 0.01, young = p < 0.001) as compared to the control group. Old mice had greater depth of burn than young mice (p < 0.001). There were greater eosinophils in the treatment cohort for both young and old mice, but it did not reach statistical significance.ConclusionThe application of a novel microcapillary gelatin–alginate hydrogel infused with anti-TNF-α antibody to partial thickness burns in mice showed reduction in partial to full thickness burn secondary progression as compared to controls using this murine model; this promising finding might help decrease the high morbidity and mortality associated with burn injuries.     

The implementation of an infection control bundle within a Total Care Burns Unit

AimTo evaluate the impact of the implementation of a best practice infection prevention and control bundle on healthcare associated burn wound infections in a paediatric burns unit.BackgroundBurn patients are vulnerable to infection. For this patient population, infection is associated with increased morbidity and mortality, thereby representing a significant challenge for burns clinicians who care for them.MethodsAn interrupted time series was used to compare healthcare associated burn wound infections in paediatric burn patients before and after implementation of an infection prevention and control bundle. Prospective surveillance of healthcare associated burn wound infections was conducted from 2012 to 2014. Other potential healthcare associated infection rates were also reviewed over the study period, including urinary tract infections, pneumonia, upper respiratory tract infections and sepsis. An infection prevention and control bundle developed in collaboration between the paediatric burn unit and infection control clinicians was implemented in 2013 in addition to previous standard practice.ResultsDuring the study period a total of 626 patients were admitted to the paediatric burns unit. Healthcare associated burn wound infections reduced from 34 in 2012 to 0 in 2014 following the implementation of the infection prevention and control bundle. Pneumonia and sepsis also reduced to 0 in 2013 and 2014, however one upper respiratory tract infection occurred in 2013 and urinary tract infections persisted in 2013.ConclusionThe implementation of an infection prevention and control bundle was effective in reducing healthcare associated burn wound infections, pneumonia and sepsis within our paediatric burns unit. Urinary tract infections remain a challenge for future improvement.     

The cGAS-STING pathway connects mitochondrial damage to inflammation in burn-induced acute lung injury in rat

ObjectiveDamage associated molecular patterns (DAMPs) are pathological mediators linking local tissue damage to systemic inflammation in various diseases. Some DAMPs, such as mitochondrial DNA (mtDNA), can be recognized by the cytoplasmic cGAS protein to trigger the activation of the stimulator of interferon genes (STING)-dependent innate immune pathway responsible for infection or sterile inflammation. The objective of our study was to evaluate the association between circulating mtDNA and cGAS-STING pathway activation in mediating inflammation following burn injury.Methods48 adult Sprague-Dawley male rats were divided into eight groups (Sham, 2, 4, 8, 12, 24, 48, 72 h after burn injury). The animals underwent 40% total body surface area scald injury to produce a full-thickness burn. Plasma samples were collected via cardiac puncture under deep anesthesia. Tissues were harvested and placed in formalin, followed by paraffin embedment. Total plasma DNA was isolated followed by measurement of mtDNA using quantitative polymerase chain reaction. Haemotoxylin-Eosin stain and Western blot was used for lung histology and protein assays, respectively. Statistical analyses were performed using ANOVA and student’s t-test and represented as mean ± s.d.ResultsPlasma mtDNA trended upward at early time-points following burn injury with peak levels at 8 h after burn when compared to the control group (345 ± 83.4 copies/μl vs. 239 ± 43.1 copies/μl, p = 0.07) and followed a bell-shaped distribution. Lung slices from burned rats showed acute injury marked by increased inflammatory infiltrate, with the maximum changes seen at 24 h, accompanied with significant upregulation of neutrophil elastase (p = 0.04). Compared with sham animals, cGAS and STING protein levels in lung tissue were up-regulated at 4 and 8 h after burn (p = 0.03 and p < 0.001, respectively).ConclusionActivation of the cGAS-STING pathway by increased plasma mtDNA is an important pathway driving neutrophil infiltration in burn-induced acute lung injury in rats. A further understanding of the STING-mediated immunopathology in lung and other susceptible organs may be important for the development of novel therapies for burn injury.     

Opiate analgesics contribute to the development of post-injury immunosuppression

BACKGROUND: Immune dysfunction and post-injury infections are complications associated with thermal injury. Opiates, the analgesic of choice for the treatment of post-burn pain, can also induce similar immune complications. However, the impact of therapeutic opiates on post-burn immune dysfunction is unknown. MATERIALS AND METHODS: C57BL/6 mice were subjected to a small 6.25% total body surface area (TBSA) burn or sham procedure. The mice were left untreated or treated with morphine sulfate by subcutaneous implantation of an Alzet pump that administered morphine sulfate at a rate of 2 mg/kg body weight/day. Plasma, splenocytes and splenic macrophages were isolated for in vitro analysis 1, 4, or 7 days later. RESULTS: Neither burn injury nor morphine treatment alone significantly altered splenic T-cell proliferation at 1, 4, or 7 days post-injury/treatment. In contrast, morphine treatment of injured mice suppressed splenic T-cell proliferation at 4 and 7 days post-injury/treatment. The suppressed proliferation of T-cells correlated with increased levels of the nitric oxide and an immunosuppressive Th-2 type phenotype. In contrast morphine treatment did not accentuate the suppressed T-cell proliferative responses associated with larger injuries covering 12.5% and 25% TBSA. Splenic macrophage function was unaffected with the exception that LPS-induced nitric oxide production was elevated in the injured mice treated with morphine. CONCLUSIONS: These findings demonstrate that those mice treated with a clinically relevant dose of morphine sulfate after an "immunologically insignificant" burn displayed immunosuppression and a Th-2 cytokine profile. Thus, the therapeutic administration of exogenous opiates appears to contribute to the development of post-burn immune dysfunction.     

Postburn immune suppression: an inflammatory response to the burn wound?

In an effort to elucidate the causes of immune suppression which follows severe burn injury, we studied the immunologic effects of subcutaneous implantation of burned skin, as well as implantation of other materials, in mice. Ten days following the implantation, splenic lymphocyte proliferation and lymphocyte surface expression of activation antigens (IL-2R and Ia) were analyzed following a 3-day culture period. In addition, peritoneal neutrophils were analyzed for oxidative burst activity using flow cytometry and a dye which reacts with intracellular hydrogen peroxide. Implantation of a 2 x 2 cm section of burned/unburned skin as well as implantation of a similar-sized piece of cotton gauze or collagen sheet resulted in subsequent suppression of both lymphocyte activation proliferation and neutrophil oxidative burst activity. An intense local inflammatory response to the burn wound may play a role leading to the profound systemic immune suppression which follows severe burn injury.