Michael J. Schurr

Nonoperative management of blunt hepatic trauma is the treatment of choice for hemodynamically stable patients. Results of a prospective trial.

BackgroundA number of retrospective studies recently have been published concerning nonoperative management of minor liver injuries, with cumulative success rates greater than 95%. However, no prospective analysis that involves a large number of higher grade injuries has been reported. The current study was conducted to evaluate the safety of nonoperative management of blunt hepatic trauma in hemodynamically stable patients regardless of injury severity. MethodsOver a 22-month period, patients with blunt hepatic injury were evaluated prospectively. Unstable patients underwent laparotomies, and stable patients had abdominal computed tomography (CT) scans. Those with nonhepatic operative indications underwent exploration, and the remainder were managed nonoperatively in the trauma intensive care unit. This group was compared with a hemodynamically matched operated cohort of blunt hepatic trauma patients (control subjects) who had been prospectively analyzed. ResultsOne hundred thirty-six patients had blunt hepatic trauma. Twenty-four (18%) underwent emergent exploration. Of the remaining 112 patients, 12 (11%) failed observation and underwent celiotomy–5 were liver-related failures (5%) and 7 were nonliver related (6%). Liver related failure rates for CT grades I through V were 20%, 3%, 3%, 0%, and 12%, respectively, and rates according to hemoperitoneum were 2% for minimal, 6% for moderate, and 7% for large. The remaining 100 patients were successfully treated without operation–30% had minor injuries (grades I–II) and 70% had major (grades III–V) injuries. There were no differences in admission characteristics between nonoperative success or failures, except admission systolic blood pressure (127 vs. 104; p < 0.04). Comparing the nonoperative group to the control group, there were no differences in admission hemodynamics or hospital length of stay, but nonoperative patients had significantly fewer blood transfusions (1.9 vs. 4.0 units; p < 0.02) and fewer abdominal complications (3% vs. 11%; p < 0.04).

Space flight alters bacterial gene expression and virulence and reveals a role for global regulator Hfq

A comprehensive analysis of both the molecular genetic and phenotypic responses of any organism to the space flight environment has never been accomplished because of significant technological and logistical hurdles. Moreover, the effects of space flight on microbial pathogenicity and associated infectious disease risks have not been studied. The bacterial pathogen Salmonella typhimurium was grown aboard Space Shuttle mission STS-115 and compared with identical ground control cultures. Global microarray and proteomic analyses revealed that 167 transcripts and 73 proteins changed expression with the conserved RNA-binding protein Hfq identified as a likely global regulator involved in the response to this environment. Hfq involvement was confirmed with a ground-based microgravity culture model. Space flight samples exhibited enhanced virulence in a murine infection model and extracellular matrix accumulation consistent with a biofilm. Strategies to target Hfq and related regulators could potentially decrease infectious disease risks during space flight missions and provide novel therapeutic options on Earth.

Surfaces modified with nanometer-thick silver-impregnated polymeric films that kill bacteria but support growth of mammalian cells.

Silver is widely used as a biocidal agent in ointments and wound dressings. However, it has also been associated with tissue toxicity and impaired healing. In vitro characterization has also revealed that typical loadings of silver employed in ointments and dressings (approximately 100 microg/cm(2)) lead to cytotoxicity. In this paper, we report the results of an initial study that sought to determine if localization of carefully controlled loadings of silver nanoparticles within molecularly thin films immobilized on surfaces can lead to antimicrobial activity without inducing cytotoxicity. Polymeric thin films of poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) were prepared by layer-by-layer deposition and loaded with approximately 0.4 microg/cm(2) to approximately 23.6 microg/cm(2) of silver nanoparticles. Bacterial killing efficiencies of the silver-loaded films were investigated against Staphylococcus epidermidis, a gram-positive bacterium, and it was determined that as little as approximately 0.4 microg/cm(2) of silver in the polymeric films caused a reduction of 6log(10)CFU/mL (99.9999%) bacteria in suspensions incubated in contact with the films (water-borne assays). Significantly, whereas the antibacterial films containing high loadings of silver were found to be toxic to a murine fibroblast cell line (NIH-3T3), the polymeric films containing approximately 0.4 microg/cm(2) of silver were not toxic and allowed attachment, and growth of the mammalian cells. Thus, the results of this study go beyond prior reports by identifying silver-impregnated, polymeric thin films that are compatible with in vitro mammalian cell culture yet exhibit antibacterial activity. These results support the hypothesis that localization of carefully controlled loadings of silver nanoparticles within molecularly thin polymeric films can lead to antimicrobial activity without cytotoxicity. More broadly, this strategy of modifying surfaces with minimal loadings of bioactive molecules indicates the basis of approaches that may permit management of microbial burden in wound beds without impairment of wound healing.

Anaerobic killing of mucoid Pseudomonas aeruginosa by acidified nitrite derivatives under cystic fibrosis airway conditions

Mucoid, mucA mutant Pseudomonas aeruginosa cause chronic lung infections in cystic fibrosis (CF) patients and are refractory to phagocytosis and antibiotics. Here we show that mucoid bacteria perish during anaerobic exposure to 15 mM nitrite (NO2) at pH 6.5, which mimics CF airway mucus. Killing required a pH lower than 7, implicating formation of nitrous acid (HNO2) and NO, that adds NO equivalents to cellular molecules. Eighty-seven percent of CF isolates possessed mucA mutations and were killed by HNO2 (3-log reduction in 4 days). Furthermore, antibiotic-resistant strains determined were also equally sensitive to HNO2. More importantly, HNO2 killed mucoid bacteria (a) in anaerobic biofilms; (b) in vitro in ultrasupernatants of airway secretions derived from explanted CF patient lungs; and (c) in mouse lungs in vivo in a pH-dependent fashion, with no organisms remaining after daily exposure to HNO2 for 16 days. HNO2 at these levels of acidity and NO2 also had no adverse effects on cultured human airway epithelia in vitro. In summary, selective killing by HNO2 may provide novel insights into the important clinical goal of eradicating mucoid P. aeruginosa from the CF airways.

Mechanisms of bacterial pathogenicity

Pathogenic bacteria utilise a number of mechanisms to cause disease in human hosts. Bacterial pathogens express a wide range of molecules that bind host cell targets to facilitate a variety of different host responses. The molecular strategies used by bacteria to interact with the host can be unique to specific pathogens or conserved across several different species. A key to fighting bacterial disease is the identification and characterisation of all these different strategies. The availability of complete genome sequences for several bacterial pathogens coupled with bioinformatics will lead to significant advances toward this goal.

A549 Lung Epithelial Cells Grown as Three-Dimensional Aggregates: Alternative Tissue Culture Model for Pseudomonas aeruginosa Pathogenesis

ABSTRACT A three-dimensional (3-D) lung aggregate model was developed from A549 human lung epithelial cells by using a rotating-wall vessel bioreactor to study the interactions between Pseudomonas aeruginosa and lung epithelial cells. The suitability of the 3-D aggregates as an infection model was examined by immunohistochemistry, adherence and invasion assays, scanning electron microscopy, and cytokine and mucoglycoprotein production. Immunohistochemical characterization of the 3-D A549 aggregates showed increased expression of epithelial cell-specific markers and decreased expression of cancer-specific markers compared to their monolayer counterparts. Immunohistochemistry of junctional markers on A549 3-D cells revealed that these cells formed tight junctions and polarity, in contrast to the cells grown as monolayers. Additionally, the 3-D aggregates stained positively for the production of mucoglycoprotein while the monolayers showed no indication of staining. Moreover, mucin-specific antibodies to MUC1 and MUC5A bound with greater affinity to 3-D aggregates than to the monolayers. P. aeruginosa attached to and penetrated A549 monolayers significantly more than the same cells grown as 3-D aggregates. Scanning electron microscopy of A549 cells grown as monolayers and 3-D aggregates infected with P. aeruginosa showed that monolayers detached from the surface of the culture plate postinfection, in contrast to the 3-D aggregates, which remained attached to the microcarrier beads. In response to infection, proinflammatory cytokine levels were elevated for the 3-D A549 aggregates compared to monolayer controls. These findings suggest that A549 lung cells grown as 3-D aggregates may represent a more physiologically relevant model to examine the interactions between P. aeruginosa and the lung epithelium during infection.

Pseudomonas aeruginosa hypoxic or anaerobic biofilm infections within cystic fibrosis airways

The airways of patients afflicted with cystic fibrosis (CF) are colonized by many pathogens, the most predominant of which is the Gram-negative bacterium Pseudomonas aeruginosa. In the thick CF airway mucus, P. aeruginosa forms antibiotic- and phagocyte-resistant structures known as biofilms, which enable the survival and growth of the organism. P. aeruginosa can undergo dramatic genetic, physiological and morphological changes in this milieu. Chronic infection leads to a considerably reduced oxygen tension, and it is believed that some bacteria grow anaerobically, especially during late-stage disease. In this article, factors that enable long-term survival of P. aeruginosa and two novel drug targets (the rhl quorum-sensing circuit and the anti-sigma factor, MucA) are discussed. Mutants lacking these factors might be uniquely susceptible to nitrogen oxide, specifically the nitrite anion (NO(2)(-)), in the treatment of P. aeruginosa airway infections in CF.

National Burn Repository 2005: a ten-year review.

In the early 1990s, the American Burn Association (ABA) started its first burn registry development initiatives. The impetus for the registry development software originated from several directions, including the following: (1) the recognition that national registries were widespread and of proven benefit; (2) growing demands from accrediting institutions, payers, and patient advocacy groups for objective and verifiable data regarding patient costs, treatments, and outcomes; and (3) the shift toward “evidence-based” medicine and the ongoing analysis of treatment effectiveness. The ABA has issued three calls for burn registry data for its National Burn Repository (NBR): 1994, 2002, and 2005. In 1994, 28 burn centers contributed data for more than 6,400 patients treated from 1991 to 1993. The ABA announced its second call for data in 2001 and distributed the published results of more than 54,000 acute burn admissions treated from 1974 to 2002 at the Association’s 2002 Annual Meeting. The third ABA call for data was issued in the Fall of 2005. The results are detailed in this report, which provides a summary of more than a quarter million acute burn admissions from 1995 to 2005, representing 70 hospitals from 30 states plus the District of Columbia. Statistics are presented in chart and table format to illustrate such key factors as patient age, burn size group, types of injuries, mortality rates, and average hospital charges by etiology and length of hospital stay. The data presented herein should help stimulate quality improvement programs in burn care, as burn centers compare their performance with the national data and as research is expanded using the NBR. The NBR will be published annually and, with continued refinements to the registry software, should become of increasing importance to clinicians, payers, researchers, and the public.

Pseudomonas aeruginosa biofilm infections in cystic fibrosis: insights into pathogenic processes and treatment strategies

Importance of the field: CF airway mucus can be infected by opportunistic microorganisms, notably Pseudomonas aeruginosa. Once organisms are established as biofilms, even the most potent antibiotics have little effect on their viability, especially during late-stage chronic infections. Better understanding of the mechanisms used by P. aeruginosa to circumvent host defenses and therapeutic intervention strategies is critical for advancing novel treatment strategies. Areas covered in this review: Inflammatory injury in CF lung, role of neutrophils in pathogenesis, P. aeruginosa biofilms, mucoidy and its relationship with poor airway oxygenation, mechanisms by which P. aeruginosa biofilms in the CF airway can be killed. What the reader will gain: An understanding of the processes that P. aeruginosa undergoes during CF airway disease and clues to better treat such infections in future. Take home message: The course of CF airway disease is a process involving host and microbial factors that often dictate frequency of pulmonary exacerbations, thus affecting the overall course. In the past decade significant discoveries have been made regarding the pathogenic processes used by P. aeruginosa to bypass the immune system. Many new and exciting features of P. aeruginosa now illuminate weaknesses in the organism that may render it susceptible to inexpensive compounds that force its own destruction.

Media ion composition controls regulatory and virulence response of Salmonella in spaceflight.

The spaceflight environment is relevant to conditions encountered by pathogens during the course of infection and induces novel changes in microbial pathogenesis not observed using conventional methods. It is unclear how microbial cells sense spaceflight-associated changes to their growth environment and orchestrate corresponding changes in molecular and physiological phenotypes relevant to the infection process. Here we report that spaceflight-induced increases in Salmonella virulence are regulated by media ion composition, and that phosphate ion is sufficient to alter related pathogenesis responses in a spaceflight analogue model. Using whole genome microarray and proteomic analyses from two independent Space Shuttle missions, we identified evolutionarily conserved molecular pathways in Salmonella that respond to spaceflight under all media compositions tested. Identification of conserved regulatory paradigms opens new avenues to control microbial responses during the infection process and holds promise to provide an improved understanding of human health and disease on Earth.