Case Report: A Child With Omental Infarction.

BACKGROUND: Omental infarction (OI) is a rare cause of acute abdominal pain, which is benign and self-limited. It is diagnosed by imaging. The etiology of OI is either idiopathic or secondary and due to torsion, trauma, hypercoagulability, vasculitis, or pancreatitis. CASE REPORT: Here, we present a case of OI in a child with acute severe right upper quadrant pain. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Correct diagnosis of OI via imaging can prevent unnecessary surgery.

Interactions of the streptococcal C5a peptidase with human fibronectin.

Group B Streptococci (GBS) is a leading cause of sepsis and meningitis in neonates and immunocompromised adults in western countries. GBS do not bind to fibronectin (Fn) in solution, but will bind to Fn adsorbed onto a solid surface. The reason for the specificity of this binding is unknown. Single molecule force spectroscopy was used to test the hypothesis that GBS, through streptococcal C5a peptidase (ScpB) molecules present on the surface of the bacteria, binds to a motif created by the juxtaposition of multiple adjacent Fn molecules. Atomic force microscopy (AFM) topographical images of adsorbed Fn deposited from various Fn coating concentrations were used to determine the Fn surface concentration. ScpB was tethered to an AFM tip with all surface modifications characterized by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. At the lowest Fn coverages the probability of observing a ScpB-Fn binding event increased linearly with Fn surface coverage. As an Fn monolayer was reached the probability of a ScpB-Fn binding event occurring increased markedly ( approximately 50 fold), with a concomitant increase in the rupture force from 17 pN to 33 pN. These results are consistent with the hypothesis that ScpB binds to a motif created by the juxtaposition of multiple Fn molecules.

Parental responses to involvement in rounds on a pediatric inpatient unit at a teaching hospital: a qualitative study.

PURPOSE: In pediatric teaching hospitals, medical decisions are traditionally made by the attending and resident physicians during rounds that do not include parents. This structure limits the ability of the medical team to provide "family-centered care" and the attending physician to model communication skills. The authors thus set out to identify how parents responded to participation in interdisciplinary teaching rounds conducted in a large tertiary care children's teaching hospital. METHOD: A qualitative descriptive study was conducted using data from semistructured interviews of parents who had participated in rounds on the inpatient medical unit of a large academic children's hospital. From December 2004 to April 2005, 18 parents were interviewed after their participation in rounds. Questions assessed their experiences, expectations, preferred communication styles, and suggestions for improvement. Transcripts of the interviews were analyzed using qualitative content analysis. RESULTS: Being able to communicate, understand the plan, and participate with the team in decision making about their child's care were the most frequently cited outcomes of importance to parents. All 18 participants described the overall experience as positive, and 17 of 18 described themselves as "comfortable" with inclusion in rounds. Use of lay terminology and inclusion of nurses in rounds were preferred. CONCLUSIONS: Including parents on ward rounds at a teaching hospital was viewed positively by parents. Specific themes of particular importance to parents were identified. Further study is needed to assess the impact of inclusion of parents on rounds on patient outcomes and the resident experience.

Structure and reactivity of adsorbed fibronectin films on mica.

Understanding the interactions of adsorbed fibronectin (Fn) with other biomolecules is important for many biomedical applications. Fn is found in almost all body fluids, in the extracellular matrix, and plays a fundamental role in many biological processes. This study found that the structure (conformation, orientation) and reactivity of Fn adsorbed onto mica is dependent on the Fn surface concentration. Atomic force microscopy and x-ray photoelectron spectroscopy were used to determine the surface coverage of adsorbed Fn from isolated molecules at low surface coverage to full monolayers at high surface coverage. Both methods showed that the thickness of Fn film continued to increase after the mica surface was completely covered, consistent with Fn adsorbed in a more upright conformation at the highest surface-Fn concentrations. Time-of-flight secondary ion mass spectrometry showed that relative intensities of both sulfur-containing (cystine, methionine) and hydrophobic (glycine, leucine/isoleucine) amino acids varied with changing Fn surface coverage, indicating that the conformation of adsorbed Fn depended on surface coverage. Single-molecule force spectroscopy with collagen-related peptides immobilized onto the atomic force microscope tip showed that the specific interaction force between the peptide and Fn increases with increasing Fn surface coverage.

Atomic force microscopy and surface plasmon resonance investigation of fibronectin interactions with group B streptococci.

The interactions of fibronectin (Fn) with group B streptococci (GBS) were investigated using the atomic force microscope (AFM) and surface plasmon resonance (SPR) biosensing. Submonolayer amounts of Fn were immobilized onto the AFM tip by two different methods, using either a sulfosuccinimidyl-4-(N-maleimidomethyl) cycholhexane-1-carboxylate (SMCC) linker or a pyridyldithio poly(ethylene glycol) succinimidylpropionate (NHS-PEG-PDP) linker. Each step of both immobilization methods was characterized using x-ray photoelectron spectroscopy. Time-of-flight secondary ion mass spectrometry experiments indicated both methods produced Fn immobilized in a similar conformation. AFM force-distance curves from live GBS plated onto polystyrene exhibited several types of interactions between the Fn functionalized AFM tip and the surface of capsule-deficient GBS (no interactions, interactions with the cell wall, Fn unfolding, large specific unbinding events, and small specific unbinding events). From analysis of the force-distance curves that exhibited only a single specific unbinding event, the work of adhesion and rupture force for the SMCC immobilized Fn tips (11,131 pN nm and 213 pN) were larger than the corresponding values for the NHS-PEG-PDP immobilized Fn tips (8115 pN nm and 189 pN). The unbinding event occurred at distances approximately 100 nm further from the surface with the NHS-PEG-PDP immobilized Fn tip compared to SMCC immobilized Fn tip. The SPR experiments of soluble Fn with adsorbed serine protease C5a peptidase (Scp), the surface protein on GBS that binds Fn, showed that both low (millimolar) and high binding (nanomolar) affinity interactions were present. However, the low binding affinity interactions dominated the adsorption process and, with increasing Fn solution concentration, the amount of Scp bound to Fn via the high binding affinity interaction decreased. These data confirm that Scp binds only to adsorbed Fn at the Fn concentrations typically present in blood plasma.

High-affinity interaction between fibronectin and the group B streptococcal C5a peptidase is unaffected by a naturally occurring four-amino-acid deletion that eliminates peptidase activity.

The streptococcal C5a peptidase (ScpB) of group B streptococci (GBS) is found in virtually all clinical GBS isolates and is required for mucosal colonization in a neonatal mouse model. ScpB inhibits neutrophil chemotaxis by enzymatically cleaving the complement component C5a. We previously identified a second function of ScpB as a fibronectin (Fn) adhesin using phage display. However, phage display can identify low-affinity interactions. We therefore measured the affinity of both full-length recombinant ScpB (FL-ScpB) and the 110-amino-acid phage display fragment (Scp-PDF) for immobilized Fn using surface plasmon resonance. The affinity for Fn was very high for both FL-ScpB (equilibrium dissociation constant [KD] = 4.0 nM) and Scp-PDF (KD = 4.4 nM) and is consistent with a biologically significant role for the adhesin activity of ScpB. We also studied the Fn adhesin activity of a common natural variant of ScpB (ScpBDelta) that contains a 4-amino-acid deletion that eliminates peptidase activity. The integrity of scpB is otherwise maintained, suggesting that the Fn adhesin activity of ScpB may be responsible for its conservation in these strains. The affinities of both FL-ScpBDelta (KD = 2.4 nM) and ScpBDelta-PDF (KD = 1.4 nM) for Fn are unaffected by the deletion. Complementation in trans by both scpB and scpBDelta corrected the Fn-binding defect of an scpB deletion mutant GBS strain to an identical degree. The high affinity of ScpB for Fn and the maintenance of this affinity in ScpBDelta support our hypothesis that the Fn adhesin activity of scpB plays a role in virulence.

Use of glnQ as a counterselectable marker for creation of allelic exchange mutations in group B streptococci.

Efficient allelic exchange mutagenesis in group B streptococci (GBS) has been hampered by the lack of a counterselectable marker system. Growth inhibition of GBS by the glutamine analog gamma-glutamyl hydrazide requires glnQ. We have used this phenomenon to create a counterselectable marker system for efficient selection of allelic exchange mutants in GBS.

Identification of novel adhesins from Group B streptococci by use of phage display reveals that C5a peptidase mediates fibronectin binding.

Group B streptococci (GBS) are a major cause of pneumonia, sepsis, and meningitis in newborns and infants. GBS initiate infection of the lung by colonizing mucosal surfaces of the respiratory tract; adherence of the bacteria to host cells is presumed to be the initial step in and prerequisite for successful colonization (G. S. Tamura, J. M. Kuypers, S. Smith, H. Raff, and C. E. Rubens, Infect. Immun. 62:2450-2458, 1994). We have performed a genome-wide screen to identify novel genes of GBS that mediate adherence to fibronectin. A shotgun phage display library was constructed from chromosomal DNA of a serotype Ia GBS strain and affinity selected on immobilized fibronectin. DNA sequence analysis of different clones identified 19 genes with homology to known bacterial adhesin genes, virulence genes, genes involved in transport or metabolic processes, and genes with yet-unknown function. One of the isolated phagemid clones showed significant homology to the gene (scpB) for the GBS C5a peptidase, a surface-associated serine protease that specifically cleaves the complement component C5a, a chemotaxin for polymorphonuclear leukocytes. In this work we have demonstrated that affinity-purified recombinant ScpB and a peptide ScpB fragment (ScpB-PDF), similar to the peptide identified in the phagemid, bound fibronectin in a concentration-dependent manner. Adherence assays to fibronectin were performed, comparing an isogenic scpB mutant to the wild-type strain. Approximately 50% less binding was observed with the mutant than with the wild-type strain. The mutant phenotype could be fully restored by in trans complementation of the mutant with the cloned wild-type scpB gene, providing further evidence for the role of ScpB in fibronectin adherence. Our results suggest that C5a peptidase is a bifunctional protein, which enzymatically cleaves C5a and mediates adherence to fibronectin. Since binding of fibronectin has been implicated in attachment and invasion of eukaryotic cells by streptococci, our results may imply a second important role for this surface protein in the pathogenesis of GBS infections.

A glutamine transport gene, glnQ, is required for fibronectin adherence and virulence of group B streptococci.

Group B streptococci (GBS) are a leading cause of neonatal sepsis and meningitis. GBS adhere to fibronectin when it is attached to a solid phase. We isolated a Tn917 transposon mutant, COH1-GT1, which shows decreased adherence to fibronectin. COH1-GT1 also shows decreased adherence to and invasion of respiratory epithelial cells in vitro and decreased virulence in vivo. COH1-GT1 contains a Tn917 insertion in a homolog of glnQ, a gene from Escherichia coli which is required for glutamine transport and codes for a cytoplasmic ATP-binding cassette protein. To confirm that the decreased fibronectin adherence of COH1-GT1 was due to the mutation in glnQ, we constructed COH1-GT2, a strain with a nonpolar site-directed mutation in glnQ. COH1-GT2 showed decreased binding to fibronectin. We also demonstrated that complementation of glnQ in trans restored fibronectin adherence to COH1-GT1. COH1-GT1 shows decreased uptake of radiolabeled glutamine and is resistant to the toxic glutamine analog gamma-L-glutamylhydrazide, demonstrating that the glnQ gene is required for glutamine transport in GBS. glnQ lacks a signal sequence and is a cytoplasmic protein in E. coli and thus is unlikely to act as a fibronectin adhesin. glnQ is transcribed in an operon with a putative glutamine permease gene, glnP, which has a novel predicted structure containing three distinct domains linked in a single gene. The first two domains are putative glutamine binding domains with homology to the E. coli periplasmic glutamine binding gene glnH. The third is a putative permease domain with homology to the E. coli glutamine permease gene glnP. RT-PCR analysis demonstrated that glnP and glnQ are contained within a single transcript. Transcription of scpB, encoding the only known fibronectin-binding adhesin of GBS, is unaffected. We speculate that glnQ may regulate expression of fibronectin adhesins by affecting cytoplasmic glutamine levels and that regulation may be posttranscriptional.