Role of a microbial factor, necrotic tissue and a foreign body in the development of wound suppuration

The effect of microorganisms, necrotic tissues and a foreign body on the development of festering process in rat wounds was studied. It was found that the presence of necrotic tissues is the necessary and sufficient condition for a clinical manifestation of infection in rat wounds. Additional infection of the wounds and introduction of a foreign body did not appreciably change the clinical picture. A model is suggested of a festering wound in rats without artificial infecting. In the festering wound, one could observe the replacement of the gram-positive coccal microflora by the gram-negative one. Meanwhile the gram-positive coccal microflora was predominant in the non-festering wound. The level of potential biochemical indicators of infection in the blood of animals with festering wounds was higher than in the blood of those with non-festering wounds. The morphology, and the content of microbial cells, the content of nucleic acids, and total proteolytic activity in festering wound tissues were examined over time.     

Prevention of burn wound conversion by allogeneic keratinocytes cultured on acellular xenodermis

Deep dermal burns frequently tend to convert into full-thickness skin loss. We found that this wound deepening may be prevented by recombined human/pig skin (RHPS), consisting of human allogeneic keratinocytes cultured on acellular pig dermis. RHPS has skin-like consistency and therefore optimal adhesiveness to the wound. It can be easily removed from the dish and transferred to the recipient. The wound bed has to be prepared by tangential excision or deep dermabrasion to the level of capillary bleeding. RHPS has to be applied ‘upside-down’, with the epidermal layer facing the wound, to avoid the dermal matrix forming a barrier to the nutrients for the keratinocytes. In our practice, more than 70% of early excised or deeply dermabraded wounds grafted with RHPS healed in the course of one week after keratinocyte transplantation. This revised version was published online in July 2006 with corrections to the Cover Date.     

The capacities of autoleukocyte-labelled scintigraphy in the detection of foci of inflammation and suppuration

The diagnostics of occult inflammation foci up to day remains the major and complicated problem in almost each clinical discipline. Whole-body scintigraphy and SPECT studies with 99mTc-autoleucocytes show silent foci of inflammation and infection. 68 patients (24 females and 44 males) aged 14-59 years with non-localized inflammatory diseases were evaluated. Each patient underwent routine clinical and laboratory investigation. But because of the inadequacy of other diagnostic procedures, the Tc-99m-WBC scans may be of great clinical importance. For the determining of the SPECT of thorax were performed using Tc-99m-HMPAO (hexametylpropilenaminoxime) labeled autoleucocytes. In 1, 3 and 24 hours post injection inflammatory foci were seen as the areas of pathogenic activity. In 24 patients the circumscribed activity seen in relation to heart convincingly demonstrated endo- and/or myocarditis. 16 patients showed acute inflammation in postoperative wound, empyema of pleura and mediastinitis as the consequences of cardiosurgery. In 16 patients whole-body scanning and SPECT of the head revealed chronic infection in nasopharynx and accessory nasal sinuses dental infection and the rest 7 patients had abdominal and pelvic inflammatory diseases, such as ulcerative colitis, intraabdominal and retroperitoneal septic foci, tubo-ovarial inflammatory disease. The data demonstrated that Tc-99m-leucocytes imaging is a highly sensitive and specific for the detection of inflammatory diseases of different localization.     

Wet wound healing

Wound treatment in a flexible transparent chamber attached to the perimeter of the wound and containing a liquid has been extensively tested in preclinical experiments in pigs and found to offer several advantages. It protects the wound; the liquid medium or saline in the chamber provides in vivo tissue culture-like conditions; and antibiotics, analgesics, and various molecules can be delivered to the wound through the chamber. The wound chamber causes no injury to the wound itself or to the surrounding intact skin. Topical delivery of, for instance, antibiotics can provide very high concentrations at the wound site and with a favorable direction of the concentration gradient. A series of 28 wounds in 20 patients were treated with a wound chamber containing saline and antibiotics. Most patients had significant comorbidity and had not responded to conservative or surgical management with débridement and delayed primary closure or skin grafts. Six wounds had foreign bodies present; four of these were joint prostheses. Seven patients were on corticosteroids for rheumatoid arthritis, lupus, or chronic obstructive pulmonary disease, and four patients had diabetes. Most patients were treated with the wound chamber in preparation for a delayed skin graft or flap procedure, but one was treated with a wound chamber until the wound healed. Twenty-five of the wounds (89 percent) healed, and five wounds (18 percent) required additional conservative management after the initial chamber treatment and grafting procedure. Of the three wounds that did not heal, one healed after additional chamber treatment, one had a skin graft that did not take, and one required reamputation at a higher level. Antibiotic delivery was less than one intravenous dose daily, which avoided the potential for systemic absorption to toxic levels. Antibiotics such as vancomycin and gentamicin could be used in concentrations of up to 10,000 times the minimal inhibitory concentration. Forty-eight hours after application, 20 percent or more of the original antibiotic concentration was present in the wound chamber fluid. In conclusion, the wound chamber provides a safe, powerful tool in the treatment of difficult infected wounds.     

Surgical wound sepsis

With the help of a surgical nurse and using data-processing techniques, a prospective clinical study was conducted to determine the wound infection rate in two hospitals in Calgary. The overall sepsis rate was 5.2% and the clean wound rate 3.5%. The latter is the more meaningful figure as it allows for comparison between hospitals, specialties and individuals and is a good guide for hospital morbidity reviews. The groundwork for succeeding wound infection is laid in the operating theatre, and it is believed that wound infection would be reduced more by attention to Halsted''s principles than by more rigid aseptic techniques. It is estimated that wound sepsis costs the Province of Alberta 1.5 million dollars per year for hospitalization alone. This amounts to roughly $1 per person per year. The annual cost of a prospective study such as the present one is approximately $7000. This is equivalent to the cost of hospitalizing 24 patients with infected wounds for one week (at $300 per week). One dividend of a prospective study is an associated reduction in infection rate. This reduction more than pays for the cost of the program.     

Innate defense regulator Peptide 1018 in wound healing and wound infection

Innate defense regulators (IDRs) are synthetic immunomodulatory versions of natural host defense peptides (HDP). IDRs mediate protection against bacterial challenge in the absence of direct antimicrobial activity, representing a novel approach to anti-infective and anti-inflammatory therapy. Previously, we reported that IDR-1018 selectively induced chemokine responses and suppressed pro-inflammatory responses. As there has been an increasing appreciation for the ability of HDPs to modulate complex immune processes, including wound healing, we characterized the wound healing activities of IDR-1018 in vitro. Further, we investigated the efficacy of IDR-1018 in diabetic and non-diabetic wound healing models. In all experiments, IDR-1018 was compared to the human HDP LL-37 and HDP-derived wound healing peptide HB-107. IDR-1018 was significantly less cytotoxic in vitro as compared to either LL-37 or HB-107. Furthermore, administration of IDR-1018 resulted in a dose-dependent increase in fibroblast cellular respiration. In vivo, IDR-1018 demonstrated significantly accelerated wound healing in S. aureus infected porcine and non-diabetic but not in diabetic murine wounds. However, no significant differences in bacterial colonization were observed. Our investigation demonstrates that in addition to previously reported immunomodulatory activities IDR-1018 promotes wound healing independent of direct antibacterial activity. Interestingly, these effects were not observed in diabetic wounds. It is anticipated that the wound healing activities of IDR-1018 can be attributed to modulation of host immune pathways that are suppressed in diabetic wounds and provide further evidence of the multiple immunomodulatory activities of IDR-1018.     

A novel titanium wound chamber for the study of wound infections in pigs

In the face of emerging multidrug-resistant microbes, reliable animal models are needed to study potential new therapies in infected wounds. To this end, we implanted screw-top titanium chambers subdermally in full-thickness wounds on both flanks (n = 6 per flank) of 2 Goettinger minipigs. After 1 wk, chambers were inoculated with Staphylococcus aureus, Pseudomonas aeruginosa, or vehicle only. Throughout the study, wound fluid was harvested for quantitative bacterial cultures to monitor infection. Animals were followed for 4 wk, after which tissue biopsies were taken for histologic analysis and quantitative bacterial counts. The implanted titanium chambers were well tolerated by the pigs throughout the study. After inoculation of the chambers, wound infection was established and maintained for 14 d. Despite infection, no systemic effects were noted. Cross-contamination was negligible, compared with the vehicle-only control. After tissue ingrowth, each chamber creates a closed system that allows harvest of exudate or application of substances without loss of material from the chamber. Because 12 chambers are implanted in each pig, researchers have the opportunity to compare multiple treatment options (for example, antibiotics, antimicrobial peptides, gene therapy) in the same animal, with no interindividual variation. We conclude that the use of titanium chambers in pigs provides a reliable and reproducible in vivo model to investigate wound healing, wound infection, and treatment options.     

Cytophotometric study of blood neutrophil and wound exudate myeloperoxidase in experimental wound healing

Changes in the activity of blood neutrophil and wound exudate myeloperoxidase (MP) have been studied cytophotometrically on the models of aseptic and infected experimental wounds in 220 male Wistar rats on the 1st-10th, 12th and 15th day after wounding. It has been established that changes in MP activity reflect the nature and stages of the pathological process and the animals' reaction to it. MP activity is significantly higher in animals with infected wounds, which indicates the intensity and duration of the inflammatory process and is of prognostic value.