Prevention of Staphylococcus aureus burn wound colonization by nasal mupirocin

BACKGROUND: There are two important routes for the transmission of Staphylococcus aureus to the burn wound. In the endogenous route, patients naturally carrying S. aureus colonize their own wounds, whereas in the exogenous route burn wounds are cross-infected from other sources. In this study we evaluated the effect of blocking the endogenous route on S. aureus burn wound colonization by mupirocin application in the nose of patients at the time of admission. METHODS: From September 2000 to January 2002 all patients with burns admitted to a single dedicated Burn Centre received nasal mupirocin upon admission. This period was compared to two control periods (C1: July 1999 to July 2000 and C2: January 2002 to January 2003) for S. aureus burn wound colonization. The colonization risk was analysed, adjusting for confounding, with Cox proportional hazard regression. RESULTS: A total of 98 patients did not have S. aureus burn wound colonization at the time of admission and were, thus, considered at risk for S. aureus acquisition during their stay. As compared to C1, the relative risk of acquiring S. aureus in their wound was 0.48 (95% CI: 0.24-0.97) in the mupirocin period and 0.55 (95% CI: 0.28-1.1) during the C2 period. S. aureus nasal/pharyngeal colonization was a significant independent risk factor for wound colonization (RR: 2.3; 95% CI: 1.2-4.2). CONCLUSION: Nasal mupirocin may contribute to risk reduction of S. aureus wound colonization in patients with burns.     

Effects of granulocyte colony-stimulating factor on bacterial translocation due to burn wound sepsis

The presence of certain defects in both cellular and humoral immunity after thermal injury has been established. Likewise, the translocation of enteric bacteria to the mesenteric lymph nodes and to distant organs has also been observed following serious thermal injury. The effects of granulocyte colony-stimulating factor (G-CSF) on bacterial translocation, the small bowel mucosa, and cecal bacterial content were investigated in a rat model of burn wound sepsis in which albino Wistar rats were scalded over 30% of their bodies, after which the lesions were infected by 1×10⁸ colony-forming units (cfu)Pseudomonas aeruginosa. The control group was treated with 5% dextrose solution subcutaneously starting 2 days preburn, while the treatment group received 100μg/kg human G-CSF subcutaneously. On the 4th day post burn all animals were killed to examine the bowel and culture of the mesenteric lymph nodes (MLN), livers, and spleens. No significant differences were observed between the groups regarding the cecal bacterial content and small bowel; however, a difference was seen in the ratio of translocation in the MLN liver and spleen and quantitative MLN cultures. Based on these findings, G-CSF was thus found to be significantly effective in reducing bacterial translocation due to burn wound sepsis.     

Probiotic fortified diet reduces bacterial colonization and translocation in a long-term neonatal rabbit model

Background

Probiotic fortified diet reduces bacterial colonization and translocation in a short-term neonatal rabbit model when continuously challenged with pathogen. The purpose of this study was to determine if live probiotic diet could remain effective at decreasing colonization/translocation of pathogens in a long-term neonatal rabbit model without ill effects of the probiotic outside the gastrointestinal (GI) tract.

Methods

Rabbit pups were born via cesarean delivery 1 day preterm and assigned to 2 diets: a newly formulated diet (controls) vs the same diet fortified with the live probiotic Lactoccocus lactis. Enterobacter cloacae was added to both preparations before each feed. Pups were gavage fed twice daily, and weights were recorded. Rabbits were sacrificed on day 7, and organs were harvested and cultured for target organism growth.

Results

The probiotic fortified diet resulted in a significant decrease in Enterobacter translocation to the liver and decreased colonization in the stomach and lungs. There was no evidence of Lactococccus translocation or colonization outside of the GI tract.

Conclusion

This probiotic fortified diet was effective at decreasing pathogenic bacteria colonization and translocation in a long-term neonatal model. The addition of L lactis to the diet resulted in appropriate growth without any colonization or translocation of the probiotic outside of the GI tract.     

An in vitro biofilm model to examine the effect of antibiotic ointments on biofilms produced by burn wound bacterial isolates

Purpose

Topical treatment of burn wounds is essential as reduced blood supply in the burned tissues restricts the effect of systemic antibiotics. On the burn surface, microorganisms exist within a complex structure termed a biofilm, which enhances bacterial resistance to antimicrobial agents significantly. Since bacteria differ in their ability to develop biofilms, the susceptibility of these biofilms to topically applied antibiotics varies, making it essential to identify which topical antibiotics efficiently disrupt or prevent biofilms produced by these pathogens. Yet, a simple in vitro assay to compare the susceptibility of biofilms produced by burn wound isolates to different topical antibiotics has not been reported.

Methods

Biofilms were developed by inoculating cellulose disks on agar plates with burn wound isolates and incubating for 24 h. The biofilms were then covered for 24 h with untreated gauze or gauze coated with antibiotic ointment and remaining microorganisms were quantified and visualized microscopically.

Results

Mupirocin and triple antibiotic ointments significantly reduced biofilms produced by the Staphylococcus aureus and Pseudomonas aeruginosa burn wound isolates tested, as did gentamicin ointment, with the exception of one P. aeruginosa clinical isolate.

Conclusions

The described assay is a practical and reproducible approach to identify topical antibiotics most effective in eliminating biofilms produced by burn wound isolates.     

Formula fortified with live probiotic culture reduces pulmonary and gastrointestinal bacterial colonization and translocation in a newborn animal model

Background/Purpose

Acidified diets are protective against intestinal bacterial colonization and translocation. Probiotic diets are designed to modulate the intestinal flora to enhance mucosal immunity. This study was designed to determine if formula acidified with live probiotic decreases bacterial gut colonization and translocation, and is equally tolerated as other acidified diets.

Methods

One hundred twenty-eight rabbit pups delivered via cesarean section [cesarean delivery, cesarean birth, abdominal delivery] were randomly assigned to 4 feeding groups: NAN Nestle (control, pH 7.0), NAN acidified with citric acid (pH 4.55), biologically acidified Pelargon (pH 4.55), and NAN with live Lactococcus lactis culture (pH 4.2). Pups were gavage fed every 12 hours with Enterobacter cloacae challenges of 10 colony-forming units/mL per feed and killed on day of life 3. Lungs, liver, spleen, mesenteric lymph nodes (MLNs), stomach, and cecum were cultured and quantitatively analyzed for target organism growth. Results were analyzed using χ² tests.

Results

NAN with live probiotic culture, when compared with Pelargon, acidified NAN, and NAN, significantly reduced the incidence of Enterobacter pulmonary colonization (P < .01), bacterial translocation (liver, P < .025; spleen and MLN, P < .05), and gastric and intestinal colonization (P < .001 for both).

Conclusion

Probiotic-fortified formula provides superior protection against pulmonary and gastrointestinal bacterial colonization and translocation compared with neutral and acidified formulas, and is equally tolerated.     

Effect of rifampin onStaphylococcus aureus colonization in children on chronic peritoneal dialysis

The efficacy of rifampin in eliminatingStaphylococcus aureus colonization was evaluated in a pediatric peritoneal dialysis population. Six children with documented nasal colonization were treated for 7 days with rifampin and cloxacillin. Although antimicrobial therapy eliminated nasal carriage in all patients, recolonization occurred in 66%. Exit site colonization proved difficult to eradicate with negative cultures documented in only 3 of 5 children after rifampin/cloxacillin therapy. AlthoughS. aureus carriage is a risk factor forS. aureus infections, efforts to eradicate carriage with rifampin are hindered by rapid recolonization.     

Gold and gold-palladium coated polypropylene grafts in a S. epidermidis wound infection model

The pig is a common large animal for experimental settings in many fields of surgery. In experimental surgery, there is a need for different narcotic procedures depending on the complexity of the surgical investigation. Narcotic procedures have to be safe, easy to handle, and should not influence the experimental results. We hereby present important aspects of handling and narcotic procedures for pigs. The aim of this publication is to supply an introduction for young surgical investigators who are planning or already have started investigations using pigs as an experimental animal. This publication is based on our institutional experience of narcotic and surgical procedures in more than 400 cases.     

严重烧伤后肠粘液成分变化与肠源性感染的关系

为探讨烧伤后回肠粘膜的病理变化,肠粘液及其中 IgA 成分的变化及这些变化与肠源性感染的关系,我们利用小鼠制作 TBsA 25%Ⅲ度烧伤模型,分别于伤后0.5、1、6、12、24小时观察;①小肠末端的病理病变;②测定小肠粘液层厚度及粘液中蛋白、己糖、唾液酸的含量;③检测粘液 IgA 血清 IgA及粘膜固有层中分泌 IgA 浆细胞数;④各时相小肠系膜淋巴结的细菌培养。结果表明:伤后小肠出现病理改变。粘液成分有变化,粘液中 IgA 含量持续下降且与肠源性感染发生关系密切。     

A novel human ex-vivo burn model and the local cooling effect of a bacterial nanocellulose-based wound dressing

BackgroundBurn wound progression is a significant problem as burns initially thought to be superficial can actually become full thickness over time. Cooling is an efficient method to reduce burn wound conversion. However, if the cooling agent is below room temperature, depending on the wound size the patient is at risk of hypothermia. Additionally, tissue perfusion is reduced leading to an aggravation of burn wound progression. We investigated if wound dressings based on non-pre-cooled bacterial nanocellulose (BNC) with a high water content cool a burn just by evaporation and reduce the intradermal damages in the skin.Material and methodsIn a human ex-vivo model, skin explants underwent contact burns using a 100 °C hot steel block. The burned areas were divided into two groups of which one was cooled with a BNC-based wound dressing. Intradermal temperature probes measured temperature in cooled and uncooled burn sites over 24 h. For histological assessments of the burned areas biopsies were taken at different time points. High mobility group box-1 (HMBG1) staining served as marker for cell vitality and necrosis in the different skin layers.ResultsIntradermal temperature measurement showed that application of the BNC-based wound dressing reduced temperature significantly in burned skin. This cooling effect resulted in a maximum temperature difference of 6.4 ± 1.9 °C and a significant mean reduction of the area under the curve in the first hour after burn of 62% (p < 0.0001). The histological results showed less necrosis and less dermal-epidermal separation in the cooled areas. The HMGB1 staining revealed more vital cells in the cooled group than in the uncooled group.ConclusionBased on our results, BNC-based wound dressings cool a burn. Intradermal temperature as well as thermal damage of the tissue was reduced. The tested BNC-based wound dressing can be used without pre-cooling to cool a burn as well as to reduce the burn BNC-based wound progression through its evaporation cooling effect.     

The effect of gases in the intraperitoneal space on cytokine response and bacterial translocation in a rat model

Background: The aim of this study was to examine cytokine response and bacterial translocation after exposure of the intraperitoneal space to carbon dioxide (CO2), helium (He), and air (Air) in a rat model. Methods: For this study, 120 Sprague-Dawley rats underwent anesthesia only (Control), 10 mmHg pneumoperitoneum (PP), or abdominal wall lift (AWL). The rats were divided into five groups according to experimental procedure: Control, PP-CO2, AWL-CO2, AWL-He, and AWL-Air. At 0, 3, 6, and 24 h after the procedures, the levels of interleukin 1b (IL-1b) and interleukin 6 (IL-6) in both plasma and peritoneal lavage fluid (PLF) were measured, and the translocation of bacteria to the mesenteric lymph nodes was evaluated. Results: The plasma IL-1b and IL-6 levels in the PP-CO2, AWL-CO2, and AWL-He groups were significantly lower than those in AWL-Air group at 6 h (p <0.05). The PLF IL-1b (at 3, 6, and 24 h) and IL-6 (at 6 h) levels in the AWL-CO2 group were significantly lower than those in the AWL-Air group (p <0.05). There were no significant differences in IL-1b and IL-6 responses among the PP-CO2, AWL-CO2, and AWL-He groups. The AWL-CO2 and PP-CO2 groups had lower incidences of bacterial translocation than did the AWL-Air group (p <0.05). Conclusions: The results from this study suggest that the gas in the intraperitoneal space, but not the increased intra-abdominal pressure, causes the alterations in host cytokine response and bacterial translocation. Carbon dioxide may play a primary role in the reduced immune response associated with laparoscopic surgery.     

Influence of topical steroids on bacterial proliferation in the burn wound.

Topical application of steroids has been shown experimentally to prevent dermal ischemia and maintain capillary perfusion in the “zone of stasis” of the burn wound. This apparent advance would be nullified if such treatment increased susceptibility to bacterial proliferation. In the model studied, susceptibility to bacterial invasion and proliferation was not increased by topical application of steroid. Addition of vitamin A to the treatment regimen exerted no effect on bacterial levels.     

The effects of ketamine and propofol on bacterial translocation in rats after burn injury

BACKGROUND: Bacterial translocation (BT) occurs after thermal injury and may result from an ischemic intestinal insult. The aim of the study was to investigate the effects of ketamine and propofol as anesthetic agents on BT in an animal model of burn injury. METHODS: Sixty male Wistar Albino rats were randomly assigned to six groups of 10 rats each. Anesthesia was induced and maintained with ketamine in groups 1, 2 and 3 and with propofol in groups 4, 5 and 6 during 6 h. Groups 2, 3, 5 and 6 received 30% total body surface area (TBSA) third-degree burns. Groups 1 and 4 had no burn injury. Then, they were allowed to recover from the anesthesia at the end of 6 h. Mean arterial pressure (MAP) was monitored continuously and maintained within 10% of baseline (before burn injury) levels in all animals. Animals in groups 3 and 6 had a laparotomy to obtain a tissue sample from the terminal ileum for determination of intestinal lipid peroxidation by-product malondialdehyde (MDA) before (baseline) and 6 and 24 h after burn injury (ABI). So these animals were not included in the BT studies. At postburn 24 h, animals in groups 1, 2 and 4, 5 were sacrified and samples were taken from the mesenteric lymph nodes (MLN), liver and spleen for bacteriologic cultures. RESULTS: The incidence of BT was found to be significantly higher in group 2 than in all the other groups. Bacterial translocation incidence of group 5 was not significantly different from that of groups 4 and 1. Group 5 was associated with a significantly reduced number of enteric organisms per gram of tissue compared to group 2. Baseline MDA contents of groups 3 and 6 were similar. Ileal MDA levels were increased in group 3, but there were no significant changes in group 6 at 6 and 24 h ABI compared to baseline. CONCLUSION: Our results suggest that propofol as an anesthetic agent may prevent BT by scavenging reactive oxygen species and inhibiting lipid peroxidation in an animal model of burn injury.     

严重烧伤后肠粘液成分变化与肠源性感染的关系

为探讨烧伤后回肠粘膜的病理变化,肠粘液及其中ＩｇＡ成分的变化及这些变化与肠源性感染的关系,我们利用小鼠制作ＴＢｓＡ２５％Ⅲ度烧伤模型,分别于伤后０．５、１、６、１２、２４小时观察;①小肠末端的病理病变;②测定小肠粘液层厚度及粘液中蛋白、己糖、唾液酸的含量;③检测粘液ＩｇＡ血清ＩｇＡ及粘膜固有层中分泌ＩｇＡ浆细胞数;④各时相小肠系膜淋巴结的细菌培养。结果表明：伤后小肠出现病理改变,粘液成分有变化,粘液中ＩｇＡ含量持续下降且与肠源性感染发生关系密切。     

Examination of the effects of kefir on healing factors in a mice burn model infected with E.coli,S.aureus and P.aeruginosa using qRT-PCR

Burn areas are susceptible to bacterial growth and infections, particularly in cases with lengthy periods of hospital stay. Burn wound healing, which involves various molecular and cellular mechanisms, continues to be a significant problem. Growth factors and cytokines play an active and vital role in wound healing. In the present study, the effects of kefir on wound healing in a 2nd-degree mouse burn model infected with e.coli, s.aureus and p.aeruginosa were investigated in vitro. In order to clarify the effects of kefir in the wound healing process, the macroscopic changes in kefir-applied scar tissue as well as wound depth and width were examined and IL-1α, IL-1β, IL-6, IL-8, IL-10 and TNF-α, VEGF, TGF-β protein levels were determined using the qRT-PCR method. The findings of the present study show that kefir has a positive impact on the factors playing a role in wound healing and accelerates the healing process.     

Tracking of green fluorescent protein labeled Escherichia coli confirms bacterial translocation in blind loop rat

BACKGROUND: Previous investigators have documented small intestinal mucosal injury in blind loop rats. However, the definitive evidence of intestinal bacterial translocation in blind loop animals has been lacking. The purpose of this study was to confirm bacterial translocation in blind loop rats and to evaluate the preventive effect of glutamine on bacterial translocation caused by blind loops. MATERIALS AND METHODS: Escherichia coli TG1 labeled with green fluorescent protein was used to track bacterial translocation by gavage to rats. Six groups (n = 10) of rats were studied: unoperated control rats; rats with self-emptying blind loop; rats with self-filling blind loop; unoperated control rats treated with glutamine, 400 mg/d; rats with self-emptying blind loop treated with glutamine, 400 mg/d; rats with self-filling blind loop treated with glutamine, 400 mg/d. Representative tissue specimens of the mesenteric lymph nodes, liver, spleen, and kidney were aseptically harvested for bacteria culture. RESULTS: Bacteria were detected in extraintestinal organs of rats with self-emptying blind loop, self-filling blind loop, and self-filling blind loop treated with glutamine. By fluorescence microscope and XbaI restriction digestion analysis, we elucidated that the bacteria isolated from extraintestinal organs were the same bacteria we gavaged to the rats. CONCLUSION: We confirmed bacterial translocation in self-filling blind loop and self-emptying blind loop rats. In addition, we also showed that glutamine prevents bacterial translocation in self-emptying blind loop rats.     

不同厚度异体皮制备的微粒皮混合自体微粒皮移植对创面愈合的影响

目的　观察不同厚度异体皮制备的微粒皮混合自体微粒皮移植于大鼠背部全层皮肤缺损后对创面愈合的影响。　方法　制作大鼠全层皮肤缺损创面模型。以移植面积扩张比为 5∶1的自体微粒皮为对照组 ( 10只 ) ,两种不同厚度异体皮制备的微粒皮与同样扩张比的自体微粒皮混合移植为实验组 ,其中实验 1组异体微粒皮厚度为 0 .3mm(10只 ) ,实验 2组 0 .6mm(6只 )。比较移植后 2、3、4周 3组大鼠创面愈合率、收缩率及组织学差异。　结果　创面愈合率 :移植后 2周实验 1组大鼠( 94 .5 8± 3.99) %和实验 2组 ( 95 .2 8± 1.93) %均高于对照组 ( 88.2 8± 6 .85 ) % (P <0.0 5 ),移植后 3周实验 2组 ( 94 .5 5± 3.4 7) %高于实验 1组 ( 89.5 1± 4 70 ) %及对照组 ( 88.5 1± 5 .5 9) % (P <0.0 5),移植后 4周 3组比较 ,差异无显著性意义 (P >0 0 5 )。创面收缩率 :实验 1组大鼠与对照组比较 ,差异无显著性意义 (P >0.0 5),实验 2组各时相点均低于实验 1组及对照组 (P <0.0 5)。组织学检查 :移植后 2周实验组大鼠有明显的淋巴细胞灶性浸润 ,移植后 4周 3组之间比较 ,差异无显著性意义 ( P>0.0 5 )。结论　适量的异体微粒皮混合自体微粒皮移植 ,可以促进创面愈合 ;混合移植等量异体微粒皮时增加其真皮厚度 ,能够减     

Endocarditis in burn patients: clinical and diagnostic considerations

BACKGROUND: Burned patients are at high risk for invasive procedures, bacteremia, and other infectious complications. Previous publications describe high incidence, delayed diagnosis, and high mortality for endocarditis in burned patients, but do not address use of contemporary diagnostic criteria. Further analysis of the clinical presentation and diagnosis may aid in the earlier recognition and decreased mortality of endocarditis in burned patients. METHODS: At a 40 bed burn center, during the period from 1 January 2003 to 1 August 2006, blood culture, electronic inpatient, echocardiographic, and autopsy records were reviewed for cases of endocarditis and persistent bacteremia (blood culture positivity for the same organism separated by 24h). In addition, we reviewed cases of burn-related bacterial endocarditis published in the English language. We compared the clinical and diagnostic aspects of our identified cases with those in the published literature. RESULTS: There were 90 episodes of persistent bacteremia or fungemia in 56 of 1250 patients admitted during the study period. Echocardiography was performed on 19, identifying 4 cases of endocarditis. One additional case of endocarditis was identified post-mortem. Time until echocardiography ranged from 6 to 176 days after onset of bacteremia. Case patient age ranged from 31 to 64 years, and total burn surface area ranged from 34 to 80%. Endocarditis occurred in 0.4% of burn unit admissions and in 8.9% of these patients with persistent bacteremia. Sites involved included the mitral valve (3), tricuspid valve (2), aortic valve (1), and pulmonic valve (1). Pathogens included Staphylococcus aureus, Pseudomonas aeruginosa, and one case of Enterococcus faecium. Diagnostic clues were minimal. Case mortality was 100%. A literature review revealed 17 publications describing confirmed bacterial endocarditis in burned patients. These cases revealed a predilection for infection by S. aureus and P. aeruginosa, a relative paucity of diagnostic clues prior to death, and a trend towards ante-mortem diagnosis and increased survival with use of diagnostic echocardiography. CONCLUSIONS: The incidence and mortality of endocarditis in burned patients remain high. Clinical clues for endocarditis in this cohort are minimal and diagnosis may be delayed. For burned patients with persistent bacteremia, especially S. aureus or P. aeruginosa of unknown source, the diagnosis of endocarditis should be entertained and early echocardiography considered.     

Comparison of pathogens and antibiotic resistance of burn patients in the burn ICU or in the common burn ward

Background

This study aims to compare pathogens and their antibiotic resistances of burn patients from burn intensive care unit (ICU) or common burn ward. Of 2395 clinical samples from 63 patients in burn ICU, pathogens were detected in 1621 samples, in which 1203 strains (74.2%) were Gram negative bacteria, 248 strains (15.3%) were Gram positive bacteria, 170 strains (10.5%) were fungi. Top-4 microorganisms isolated from patients in burn ICU were Bauman's Acinetobacter (557, 34.4%), Pseudomonas aeruginosa (287.17.7%), Staphylococcus aureus (199, 12.3%) and Klebsiella pneumoniae (171, 10.5%). Of 512 clinical samples from 235 patients in common burn units, pathogens were detected in 373 samples, in which 189 (50.6%) strains were Gram negative bacteria, 150 strains (40.2%) were Gram positive bacteria, 34 strains (9.2%) were fungi. Top-4 microorganisms isolated from patients in common burn units were S. aureus (103, 27.6%), P. aeruginosa (46, 12.3%), K. pneumoniae (38, 10.2%) and Escherichia coli (32, 8.6%). Antibiotic resistance rates of pathogens isolated from clinical samples of burn patients from ICU was significantly higher than those from common units.

Conclusions

Pathogens and their antibiotic resistances are significantly different between burn ICU and common burn units. This finding has great implication for infection control in burn patients.     

Novel biodegradable composite wound dressings with controlled release of antibiotics: results in a guinea pig burn model

Approximately 70% of all people with severe burns die from related infections despite advances in treatment regimens and the best efforts of nurses and doctors. Silver ion-eluting wound dressings are available for overcoming this problem. However, there are reports of deleterious effects of such dressings due to cellular toxicity that delays the healing process, and the dressing changes needed 1-2 times a day are uncomfortable for the patient and time consuming for the stuff. An alternative concept in wound dressing design that combines the advantages of occlusive dressings with biodegradability and intrinsic topical antibiotic treatment is described herewith. The new composite structure presented in this article is based on a polyglyconate mesh and a porous poly-(dl-lactic-co-glycolic acid) matrix loaded with gentamicin developed to provide controlled release of antibiotics for three weeks. In vivo evaluation of the dressing material in contaminated deep second degree burn wounds in guinea pigs (n = 20) demonstrated its ability to accelerate epithelialization by 40% compared to an unloaded format of the material and a conventional dressing material. Wound contraction was reduced significantly, and a better quality scar tissue was formed. The current dressing material exhibits promising results, does not require frequent bandage changes, and offers a potentially valuable and economic approach to treating the life-threatening complication of burn-related infections.