Alice N. Neely

American Burn Association consensus conference to define sepsis and infection in burns.

Because of their extensive wounds, burn patients are chronically exposed to inflammatory mediators. Thus, burn patients, by definition, already have “systemic inflammatory response syndrome.” Current definitions for sepsis and infection have many criteria (fever, tachycardia, tachypnea, leukocytosis) that are routinely found in patients with extensive burns, making these current definitions less applicable to the burn population. Experts in burn care and research, all members of the American Burn Association, were asked to review the literature and prepare a potential definition on one topic related to sepsis or infection in burn patients. On January 20, 2007, the participants met in Tucson, Arizona to develop consensus for these definitions. After review of the definitions, a summary of the proceedings was prepared. The goal of the consensus conference was to develop and publish standardized definitions for sepsis and infection-related diagnoses in the burn population. Standardized definitions will improve the capability of performing more meaningful multicenter trials among burn centers.

Role of Motility and Flagellin Glycosylation in the Pathogenesis of Pseudomonas aeruginosa Burn Wound Infections

ABSTRACT In this study, we tested the contribution of flagellar motility, flagellin structure, and its glycosylation in Pseudomonas aeruginosa using genetically defined flagellar mutants. All mutants and their parent strains were tested in a burned-mouse model of infection. Motility and glycosylation of the flagellum appear to be important determinants of flagellar-mediated virulence in this model. This is the first report where genetically defined flagellar variants of P. aeruginosa were tested in the burned-mouse model of infection.

A Survey of Gram-negative Bacteria Survival on Hospital Fabrics and Plastics

One critical factor for the transmission of microorganisms from person to person or from the environment to a person (patient or health care worker) is the ability of the microbe to survive on an environmental surface. The purpose of this study was to determine the length of survival of various gram-negative bacteria on fabrics and plastics commonly used in hospitals. Seven materials were tested: smooth cotton (clothing), cotton terry (towels), 60% cotton-40% polyester blend (scrub suits and lab coats), polyester (drapes), 75% nylon-25% spandex (pressure garments), polyvinyl (splash aprons), and polyurethane (keyboard covers). The following bacteria were tested: Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Serratia marcescens, Proteus mirabilis, Acinetobacter species, and Enterobacter species. Swatches of the materials were inoculated with defined amounts of bacteria and assayed at regular intervals. Survival was dependent on the bacterium, its inoculum size, and the material tested. At 102 microorganisms per swatch, bacteria survived from less than 1 hour to 8 days. At 10(4) to 10(5) bacteria per swatch, survival ranged from 2 hours to more than 60 days. These findings emphasize the need for careful disinfection and conscientious contact control procedures in areas that serve immunosuppressed individuals, such as patients with burn injuries.

Survival of Some Medically Important Fungi on Hospital Fabrics and Plastics

ABSTRACT Tests of the survival of Candida spp.,Aspergillus spp., a Fusariumsp., a Mucor sp., and aPaecilomyces sp. on hospital fabrics and plastics indicated that viability was variable, with most fungi surviving at least 1 day but many living for weeks. These findings reinforce the need for appropriate disinfection and conscientious contact control precautions.

Gelatinase activity in keloids and hypertrophic scars.

Keloids and hypertrophic scars are characterized by excessive deposition of collagen, which may result from insufficient protein degradation. Little is known about the levels of two gelatinases, matrix metalloproteinase‐2 (72 kD type IV collagenase) and matrix metalloproteinase‐9 (matrix metalloproteinase‐9; 92 kD type IV collagenase) in these abnormal scars. The purpose of this study was to determine levels of these proteinases in tissue from hypertrophic scars, keloids, and donor skin. Ten hypertrophic scar samples, 9 keloid samples, and 10 donor skin samples were frozen, pulverized, homogenized, clarified by centrifugation, and analyzed for matrix metalloproteinases by quantitative zymography. Identity of matrix metalloproteinases was determined using a conditioned media reference standard, molecular weight ladders, and Western blotting. Levels of matrix metalloproteinase‐9 activity were very low or undetectable in all samples. However, matrix metalloproteinase‐2 activity was significantly elevated in keloids and hypertrophic scars vs. donor samples: 2.6 and 3.9‐fold increases for latent matrix metalloproteinase‐2, 7.8 and 6.9‐fold increases for active matrix metalloproteinase‐2, respectively. We conclude that little matrix metalloproteinase‐9 activity (the gelatinase involved in early tissue repair) is present in keloids and hypertrophic scars, while matrix metalloproteinase‐2 activity (the gelatinase involved in prolonged tissue remodeling) is present in donor skin and is significantly increased in hypertrophic scars and keloids.

PcrV Immunization Enhances Survival of Burned Pseudomonas aeruginosa-Infected Mice

ABSTRACT Burned Pseudomonas aeruginosa-infected mice immunized against PcrV, a type III virulence system translocating protein, showed significantly enhanced survival compared to controls. Survival was non-O serotype specific and correlated with a reduced systemic microbial load. Infection with a high-level toxin A-producing strain required supplemental antitoxin treatment to enhance survival.

Intranasal immunization with heterologously expressed polysaccharide protects against multiple Pseudomonas aeruginosa infections

Surface-expressed bacterial polysaccharides are often immunodominant, protective antigens. However, these antigens are chemically and serologically highly heterogeneous, and conjugation to protein carriers is often necessary to enhance their immunogenicity. Here we show the efficacy of intranasal immunization of mice with attenuated Salmonella enterica serovar Typhimurium expressing the O antigen portion of Pseudomonas aeruginosa lipopolysaccharide. P. aeruginosa is an ideal model system because it can cause a myriad of localized and systemic infections. In particular, this bacterium is a leading cause of hospital-acquired pneumonia and is responsible for infections after burns and after eye injury. In addition, there are mouse models of infection that mimic the clinical manifestations of P. aeruginosa infections. Immunized mice were highly protected against infection, with long-lasting immunity to acute P. aeruginosa pneumonia, whereas mice immunized with Salmonella containing only the cloning vector or PBS were not. Prophylactic and therapeutic administration of sera from vaccinated animals protected naive mice. Intranasal vaccination also provided complete protection from infections after burns and reduced pathology after corneal abrasions. These results indicate that intranasal delivery of heterologously expressed polysaccharide antigens provides protection at distinct sites of infection. This approach for the expression and delivery of polysaccharide antigens as recombinant immunogens could be easily adapted to develop vaccines for many infectious agents, without the need for complicated purification and conjugation procedures.

Are topical antimicrobials effective against bacteria that are highly resistant to systemic antibiotics

An increasing number of bacteria are resistant to multiple systemic antibiotics. The purpose of this study was to determine if topical antimicrobials are still effective against multi-drug resistant organisms (MDROs). MDROs, including Acinetobacter, Pseudomonas, Klebsiella, Staphylococcus, and Enterococcus, were collected from four burn hospitals. The sensitivity of 47 MDROs to 11 commonly used topical agents (mafenide acetate, nystatin, mafenide + nystatin, silver nitrate, Dakin’s, polymyxin B, neomycin, polymyxin + neomycin, silver sulfadiazine, bacitracin, silver sulfadiazine + bacitracin) was tested using the agar well diffusion assay and compared with the sensitivity of 27 non-MDROs of similar genera. Overall 88% of the tests of the non-MDROs showed susceptibility to the topicals compared with 80% for the MDROs (P < .05). Specific findings included: all of the gram-positive non-MDROs were sensitive to bacitracin compared with only 67% of the MDROs (P < .05); 74% of the non-MDROs were sensitive to neomycin vs 26% of the MDROs (P < .01). Even for the susceptible isolates, the zones of inhibition were smaller for the MDROs than for the non-MDROs (P < .002), indicating decreased susceptibility of the MDROs. Specifically, while the MDRO Acinetobacter were sensitive to most of the topicals, the zones of inhibition for silvadene, silvadene + bacitracin, neomycin, and neomycin + polymyxin were significantly smaller (P < .001) for the Acinetobacter MDROs than the non-MDROs. Although many topicals are still effective against some MDROs, MDROs are more resistant to topicals than are non-MDROs. Some treatment assumptions based historically on the efficacy of topical antimicrobial agents against non-MDROs need to be re-evaluated for MDROs.

Circulating levels of tumour necrosis factor, interleukin 6 and proteolytic activity in a murine model of burn and infection

Cytokines and proteinases have both been implicated as mediators in the inflammatory response associated with trauma and sepsis. Using a burned-infected mouse model, it was previously found that mortality is proportional to the amount of proteolytic activity (PA) in the circulation. However, little is known about circulating cytokine levels in hosts that are both burned and infected. With this mouse model, both tumour necrosis factor (TNF) and interleukin 6 (IL-6) were upregulated by a burn and by an infection. Burn plus infection produced an additive effect on each cytokine, but IL-6 levels correlated better with mortality. Treating mice with the proteinase inhibitor aprotinin immediately preburn and infectious challenge significantly decreased IL-6, PA and mortality. This may be a clinically relevant model for studying mediators in burned and/or septic hosts.

Gelatinase activities in wounds of healing-impaired mice versus wounds of non-healing-impaired mice.

The gelatinases, matrix metalloproteinase-2 and -9 (MMP-2 and MMP-9), have been implicated in different aspects of wound repair. However, little is known about MMP-2 and MMP-9 activity in animal models of impaired wound healing. We sought to compare serial gelatinase activities for 25 days after full-thickness excisional wounds in genetically diabetic healing-impaired mice and their nondiabetic non-healing-impaired littermates. Wound samples were frozen, homogenized, clarified by centrifugation, and analyzed on zymography gels, and MMP bands were quantitated relative to a conditioned media standard from HT-1080 cells. Gelatinase activity in both diabetic mice and nondiabetic mice increased after the mice were wounded. However, levels of latent gelatinases peaked earlier in the diabetic wounds, and there was more active MMP-2 and MMP-9 in the wounds of the diabetic mice than in the wounds of the nondiabetic mice. Because the higher gelatinase activity in the wounds of the diabetic mice was similar to the higher levels of gelatinase reported in difficult-to-heal wounds such as ulcers and burns, this diabetic mouse model may be useful for studies of these proteinases and their inhibitors in impaired wound healing.