Characterization of the local and systemic temporal changes to the lipid mediator and cytokine cascades following osteotomy and polytrauma

Polytrauma (PT) inducesglobal changes to inflammatory signaling, contributing to delayed fracturehealing. In a rat model of PT encompassing burn, blunt trauma, and osteotomy, we characterized the local and systemic temporal changes to the lipid mediator(LM) cascade, circulating white blood cells (WBCs), and local levels of growthfactors (GF)s and cytokines. Male rats received either a non-critical 3mmfemoral osteotomy (OST) or PT trauma procedures and were survived for 6, 24,48, 72, 96, 168, or 240hrs and blood, plasma, and fractured femurs werecollected. Whole femurs were homogenized to extract LMs, protein, and RNA, while blood and plasma were used for WBC and LM analysis, respectively. At the fracture site, prostaglandin (PG) E2 was significantly higher in OST at 24 and 72hrs, levels of PGF2α were higher in OST at 24hrs, while resolvin (Rv) D1 was higher in PTat 6hrs post injury. There were no differences in the expression ofcyclooxygenase-2 (COX-2), or lipoxygenase-5 (LOX-5) and LOX-15. In plasma, there were no significant differences in PG levels at any time. Plasma RvE1 was elevated in PT immediately following injury while maresin 1 (MaR1) was significantly lower in PT at 168hrs. Total WBCs and lymphocytes (103cells/uL) were lower in PT overall and significantly so at 72 and 96hrs, respectively. Additionally, the percent of neutrophils in PT was significantlyelevated and percent lymphocytes was decreased at 48 and 168hrs compared toOST. Protein analysis of the fracture site found early elevation of cytokines(IL-1β, IL-13, IL-6) and GFs in PT at 48 and 72hrs. These results indicate thatchanges to circulating LM and WBCs may provide predictive measures of non-unionand therapeutic targets to improve fracture healing.

Soluble factors from biofilms of wound pathogens modulate human bone marrow-derived stromal cell differentiation, migration, angiogenesis, and cytokine secretion

Background

Chronic, non-healing wounds are often characterized by the persistence of bacteria within biofilms - aggregations of cells encased within a self-produced polysaccharide matrix. Biofilm bacteria exhibit unique characteristics from planktonic, or culture-grown, bacterial phenotype, including diminished responses to antimicrobial therapy and persistence against host immune responses. Mesenchymal stromal cells (MSCs) are host cells characterized by their multifunctional ability to undergo differentiation into multiple cell types and modulation of host-immune responses by secreting factors that promote wound healing. While these characteristics make MSCs an attractive therapeutic for wounds, these pro-healing activities may be differentially influenced in the context of an infection (i.e., biofilm related infections) within chronic wounds. Herein, we evaluated the effect of soluble factors derived from biofilms of clinical isolates of Staphylococcus aureus and Pseudomonas aeruginosa on the viability, differentiation, and paracrine activity of human MSCs to evaluate the influence of biofilms on MSC activity in vitro.

Results

Exposure of MSCs to biofilm-conditioned medias of S. aureus and P. aeruginosa resulted in reductions in cell viability, in part due to activation of apoptosis. Similarly, exposure to soluble factors from biofilms was also observed to diminish the migration ability of cells and to hinder multi-lineage differentiation of MSCs. In contrast to these findings, exposure of MSCs to soluble factors from biofilms resulted in significant increases in the release of paracrine factors involved in inflammation and wound healing.

Conclusions

Collectively, these findings demonstrate that factors produced by biofilms can negatively impact the intrinsic properties of MSCs, in particular limiting the migratory and differentiation capacity of MSCs. Consequently, these studies suggest use/application of stem-cell therapies in the context of infection may have a limited therapeutic effect.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-015-0412-x) contains supplementary material, which is available to authorized users.

Human plasma enhances the expression of Staphylococcal microbial surface components recognizing adhesive matrix molecules promoting biofilm formation and increases antimicrobial tolerance In Vitro

Background

Microbial biofilms have been associated with the development of chronic human infections and represent a clinical challenge given their increased antimicrobial tolerance. Staphylococcus aureus is a major human pathogen causing a diverse range of diseases, of which biofilms are often involved. Staphylococcal attachment and the formation of biofilms have been shown to be facilitated by host factors that accumulate on surfaces. To better understand how host factors enhance staphylococcal biofilm formation, we evaluated the effect of whole human plasma on biofilm formation in clinical isolates of S. aureus and the expression of seven microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) known to be involved in biofilm formation by quantitative real-time PCR. We also evaluated whether plasma augmented changes in S. aureus biofilm morphology and antimicrobial resistance.

Results

Exposure of clinical isolates of S. aureus to human plasma (10%) within media, and to a lesser extent when coated onto plates, significantly enhanced biofilm formation in all of the clinical isolates tested. Compared to biofilms grown under non-supplemented conditions, plasma-augmented biofilms displayed significant changes in both the biofilm phenotype and cell morphology as determined by confocal scanning laser microscopy (CLSM) and scanning electron microscopy (SEM), respectively. Exposure of bacteria to plasma resulted in a significant fold-increase in MSCRAMM expression in both a time and isolate-dependent manner. Additionally, plasma-augmented biofilms displayed an increased tolerance to vancomycin compared to biofilms grown in non-supplemented media.

Conclusions

Collectively, these studies support previous findings demonstrating a role for host factors in biofilm formation and provide further insight into how plasma, a preferred growth medium for staphylococcal biofilm formation enhances as well as augments other intrinsic properties of S. aureus biofilms. Consequently, these findings indicate that incorporation of host factors may be necessary to better replicate in vivo conditions and for the best utility of a clinical biofilm assay to evaluate the process of biofilm formation and treatments.

Effects of local delivery of D-amino acids from biofilm-dispersive scaffolds on infection in contaminated rat segmental defects

Infectious complications of open fractures continue to be a significant factor contributing to non-osseous union and extremity amputation. The persistence of bacteria within biofilms despite meticulous debridement and antibiotic therapy is believed to be a major cause of chronic infection. Considering the difficulties in treating biofilm-associated infections, the use of biofilm dispersal agents as a therapeutic strategy for the prevention of biofilm-associated infections has gained considerable interest. In this study, we investigated whether local delivery of D-Amino Acids (D-AAs), a biofilm dispersal agent, protects scaffolds from contamination and reduces microbial burden within contaminated rat segmental defects in vivo. In vitro testing on biofilms of clinical isolates of Staphylococcus aureus demonstrated that D-Met, D-Phe, D-Pro, and D-Trp were highly effective at dispersing and preventing biofilm formation individually, and the effect was enhanced for an equimolar mixture of D-AAs. Incorporation of D-AAs into polyurethane scaffolds as a mixture (1:1:1 D-Met:D-Pro:D-Trp) significantly reduced bacterial contamination on the scaffold surface in vitro and within bone when implanted into contaminated femoral segmental defects. Our results underscore the potential of local delivery of d-AAs for reducing bacterial contamination by targeting bacteria within biofilms, which may represent a treatment strategy for improving healing outcomes associated with open fractures.

Staphylococcus aureus biofilms decrease osteoblast viability, inhibits osteogenic differentiation, and increases bone resorption in vitro

Background

Osteomyelitis is a severe and often debilitating disease characterized by inflammatory destruction of bone. Despite treatment, chronic infection often develops which is associated with increased rates of treatment failure, delayed osseous-union, and extremity amputation. Within affected bone, bacteria exist as biofilms, however the impact of biofilms on osteoblasts during disease are unknown. Herein, we evaluated the effect of S. aureus biofilms on osteoblast viability, osteogenic potential, and the expression of the pro-osteoclast factor, receptor activator of NF-kB ligand (RANK-L).

Methods

Osteoblasts were exposed to biofilm conditioned media (BCM) from clinical wound isolates of Staphylococcus aureus under normal growth and osteogenic conditions to assess cellular viability and osteoblast differentiation, respectively. Cell viability was evaluated using a live/dead assay and by quantifying total cellular DNA at days 0, 1, 3, 5, and 7. Apoptosis following treatment with BCM was measured by flow-cytometry using the annexin V-FITC/PI apoptosis kit. Osteogenic differentiation was assessed by measuring alkaline phosphatase activity and intracellular accumulation of calcium and osteocalcin for up to 21 days following exposure to BCM. Expression of genes involved in osteogenic differentiation and osteoclast regulation, were also evaluated by quantitative real-time PCR.

Results

BCM from clinical strains of S. aureus reduced osteoblast viability which was accompanied by an increase in apoptosis. Osteogenic differentiation was significantly inhibited following treatment with BCM as indicated by decreased alkaline phosphatase activity, decreased intracellular accumulation of calcium and inorganic phosphate, as well as reduced expression of transcription factors and genes involved in bone mineralization in viable cells. Importantly, exposure of osteoblasts to BCM resulted in up-regulated expression of RANK-L and increase in the RANK-L/OPG ratio compared to the untreated controls.

Conclusions

Together these studies suggest that soluble factors produced by S. aureus biofilms may contribute to bone loss during chronic osteomyelitis simultaneously by: (1) reducing osteoblast viability and osteogenic potential thereby limiting new bone growth and (2) promoting bone resorption through increased expression of RANK-L by osteoblasts. To our knowledge these are the first studies to demonstrate the impact of staphylococcal biofilms on osteoblast function, and provide an enhanced understanding of the pathogenic role of staphylococcal biofilms during osteomyelitis.

Biofilm formation by clinical isolates and the implications in chronic infections

Background

Biofilm formation is a major virulence factor contributing to the chronicity of infections. To date few studies have evaluated biofilm formation in infecting isolates of patients including both Gram-positive and Gram-negative multidrug-resistant (MDR) species in the context of numerous types of infectious syndromes. Herein, we investigated the biofilm forming capacity in a large collection of single patient infecting isolates and compared the relationship between biofilm formation to various strain characteristics.

Methods

The biofilm-forming capacity of 205 randomly sampled clinical isolates from patients, collected from various anatomical sites, admitted for treatment at Brooke Army Medical Center (BAMC) from 2004–2011, including methicillin-resistant/methicillin susceptible Staphylococcus aureus (MRSA/MSSA) (n=23), Acinetobacter baumannii (n=53), Pseudomonas aeruginosa (n=36), Klebsiella pneumoniae (n=54), and Escherichia coli (n=39), were evaluated for biofilm formation using the high-throughput microtiter plate assay and scanning electron microscopy (SEM). Relationships between biofilm formation to clonal type, site of isolate collection, and MDR phenotype were evaluated. Furthermore, in patients with relapsing infections, serial strains were assessed for their ability to form biofilms in vitro.

Results

Of the 205 clinical isolates tested, 126 strains (61.4%) were observed to form biofilms in vitro at levels greater than or equal to the Staphylococcus epidermidis, positive biofilm producing strain, with P. aeruginosa and S. aureus having the greatest number of biofilm producing strains. Biofilm formation was significantly associated with specific clonal types, the site of isolate collection, and strains positive for biofilm formation were more frequently observed to be MDR. In patients with relapsing infections, the majority of serial isolates recovered from these individuals were observed to be strong biofilm producers in vitro.

Conclusions

This study is the first to evaluate biofilm formation in a large collection of infecting clinical isolates representing diverse types of infections. Our results demonstrate: (1) biofilm formation is a heterogeneous property amongst clinical strains which is associated with certain clonal types, (2) biofilm forming strains are more frequently isolated from non-fluid tissues, in particular bone and soft tissues, (3) MDR pathogens are more often biofilm formers, and (4) strains from patients with persistent infections are positive for biofilm formation.

Upper aerodigestive tract and lung tumors after liver transplantation

BACKGROUND

The purpose of this study was to analyze the incidence, clinical characteristics, treatment, and outcome of upper aerodigestive (UAD) and lung de novo tumors after ortothopic liver transplantation (OLT).

PATIENTS AND METHODS

Between April 1986 and June 2002, we performed 851 OLT in 753 patients. We excluded pediatric, partial, and hepatorenal transplants and recipients who died within 2 months after OLT. Thus, we analyzed the incidence and outcome of these tumors in 605 patients after OLT.

RESULTS

We found 21 (3.5%) tumors in 20 (3.3%) recipients: 14 were UAD tumors (three in floor of the mouth, two in tonsil, one in tongue, one in pharynx, three in larynx, and four in esophagus) and seven were lung tumors. Nineteen patients were men and one was a woman, with a mean age at transplantation of 47.7+/-8.6 years. Mean time from OLT to tumor diagnosis was 61.7+/-35.1 years. As risk factors, 70% were heavy smokers, 75% were heavy drinkers, and 70% developed acute rejection. The incidence of these tumors was significantly higher in transplanted patients for alcoholic cirrhosis compared to the nonalcoholic cirrhosis (8.1% vs 0.8%; P<.0001). After surgical excision in 65% of patients, 1-, 2-, and 3-year patient survival were 47.6%, 37.0%, and 19.7%, respectively.

CONCLUSION

There is a significantly higher incidence of these tumors in male heavy drinkers and/or smokers who underwent OLT for alcoholic cirrhosis; in spite of aggressive surgical treatment, the prognosis is poor.