IL-1-dependent electrophysiological changes and cardiac neural remodeling in a mouse model of Kawasaki disease vasculitis.

Kawasaki disease (KD) is the leading cause of acquired heart disease in children. In addition to coronary artery abnormalities, aneurysms and myocarditis, acute KD is also associated with echocardiogram (ECG) abnormalities in 40-80% of patients. Here, we show that these ECG changes are recapitulated in the Lactobacillus casei cell wall extract (LCWE)-induced KD vasculitis mouse model. LCWE-injected mice developed elevated heart rate and decreased R wave amplitude, with significant differences in prolonged ventricular repolarization. LCWE-injected mice developed cardiac ganglion inflammation, that may affect the impulse-conducting system in the myocardium. Furthermore, serum nerve growth factor (NGF) was significantly elevated in LCWE-injected mice, similar to children with KD vasculitis, associated with increased neural remodeling of the myocardium. ECG abnormalities were prevented by blocking interleukin (IL)-1 signaling with anakinra, and the increase in serum NGF and cardiac neural remodeling were similarly blocked in Il1r1-/- mice and in wild-type mice treated with anakinra. Thus, similar to clinical KD, the LCWE-induced KD vasculitis mouse model also exhibits electrophysiological abnormalities and cardiac neuronal remodeling, and these changes can be prevented by blocking IL-1 signaling. These data support the acceleration of anti-IL-1 therapy trials to benefit KD patients.

IL-1 receptor antagonist, anakinra, prevents myocardial dysfunction in a mouse model of Kawasaki disease vasculitis and myocarditis.

Kawasaki disease (KD) vasculitis is an acute febrile illness of childhood characterized by systemic vasculitis of unknown origin, and is the most common cause of acquired heart disease among children in the United States. While  histological evidence of myocarditis can be found in all patients with acute KD, only a minority of patients are clinically symptomatic and a subset demonstrate echocardiographic evidence of impaired myocardial function, as well as increased left ventricular mass, presumed to be due to myocardial edema and inflammation. Up to a third of KD patients fail to respond to first-line therapy with intravenous immunoglobulin (IVIG), and the use of interleukin (IL)-1 receptor antagonist (IL-1Ra, anakinra) is currently being investigated as an alternative therapeutic approach to treat IVIG-resistant patients. In this study, we sought to investigate the effect of IL-1Ra on myocardial dysfunction and its relation to myocarditis development during KD vasculitis. We used the Lactobacillus casei cell-wall extract (LCWE)-induced murine model of KD vasculitis and investigated the effect of IL-1Ra pretreatment on myocardial dysfunction during KD vasculitis by performing histological, magnetic resonance imaging (MRI) and echocardiographic evaluations. IL-1Ra pretreatment significantly reduced KD-induced myocardial inflammation and N-terminal pro B-type natriuretic peptide (NT-proBNP) release. Both MRI and echocardiographic studies on LCWE-injected KD mice demonstrated that IL-1Ra pretreatment results in an improved ejection fraction and a normalized left ventricular function. These findings further support the potential beneficial effects of IL-1Ra therapy in preventing the cardiovascular complications in acute KD patients, including the myocarditis and myocardial dysfunction associated with acute KD.

Sonothrombolysis: the contribution of stable and inertial cavitation to clot lysis.

Microbubble-mediated sonothrombolysis (STL) is a remarkable approach to vascular occlusion therapy. However, STL remains a complex process with multiple interactions between clot, ultrasound (US), microbubbles (MB) and thrombolytic drug. The aim of this study was to evaluate the ability of combining US and MB to degrade fibrin and, more specifically, to assess the roles of both stable (SC) and inertial (IC) cavitation. Human blood clots containing radiolabeled fibrin were exposed to different combinations of recombinant tissue plasminogen activator (rtPA), US (1 MHz) and phospholipid MB. Three acoustic pressures were tested: 200, 350 and 1,300 kPa (peak-negative pressure). Clot lysis was assessed by diameter loss and release of radioactive fibrin degradation products. The combination rtPA + US + MB clearly revealed that IC (1,300 kPa) was able to enhance fibrin degradation significantly (66.3 ± 1.8%) compared with rtPA alone (51.7 ± 2.0%, p < 0.001). However, SC failed to enhance fibrin degradation at an acoustic pressure of 200 kPa. At 350 kPa, a synergistic effect between rtPA and US + MB was observed with an absolute increase of 6% compared to rtPA alone (p < 0.001). Conversely, without rtPA, the combination of US + MB was unable to degrade the fibrin network (0.3 ± 0.1%, p > 0.05 vs. control), but induced a distinct loss of red blood cells throughout the entire thickness of the clot, implying that MB were able to penetrate and cavitate inside the clot.

Ultrasound contrast agents for ultrasound molecular imaging.

Ultrasound is a real-time imaging technique which is widely used in many clinical applications for its capacity to provide anatomic information with high spatial and temporal resolution. The advent of ultrasound contrast agents in combination with contrast-specific imaging modes has given access to perfusion assessments at an organ level, leading to an improved diagnostic accuracy. More recently, the development of biologically-targeted ultrasound contrast agents has expanded the role of ultrasound even further into molecular imaging applications. Ultrasound molecular imaging can be used to visualize the expression of intravascular markers, and to assess their local presence over time and/or during therapeutic treatment. Major applications are in the field of inflammation and neoangiogenesis due to the strictly intravascular presence of microbubbles. Various technologies have been investigated for attaching the targeting moiety to the shell from simple biotin-avidin constructs to more elaborated insertion within the shell through attachment to PEG residues. This important improvement has allowed a clinical translation of initial pre-clinical investigations, opening the way for an early detection and an accurate characterization of lesions in patients. The combination of anatomic, functional and molecular information/data provided by contrast ultrasound is a powerful tool which is still in its infancy due to the lack of agents suitable for clinical use. The advantages of ultrasound techniques combined with the molecular signature of lesions will represent a significant advance in imaging in the field of personalized medicine.

The role of pattern recognition receptors in intestinal inflammation.

Recognition of microorganisms by pattern-recognition receptors (PRRs) is the primary component of innate immunity that is responsible for the maintenance of host-microbial interactions in intestinal mucosa. Dysregulation in host-commensal interactions has been implicated as the central pathogenesis of inflammatory bowel disease (IBD), which predisposes to developing colorectal cancer. Recent animal studies have begun to outline some unique physiology and pathology involving each PRR signaling in the intestine. The major roles played by PRRs in the gut appear to be the regulation of the number and the composition of commensal bacteria, epithelial proliferation, and mucosal permeability in response to epithelial injury. In addition, PRR signaling in lamina propria immune cells may be involved in induction of inflammation in response to invasion of pathogens. Because some PRR-deficient mice have shown variable susceptibility to colitis, the outcome of intestinal inflammation may be modified depending on PRR signaling in epithelial cells, immune cells, and the composition of commensal flora. Through recent findings in animal models of IBD, this review will discuss how abnormal PRR signaling may contribute to the pathogenesis of inflammation and inflammation-associated tumorigenesis in the intestine.

Perfusion quantification in contrast-enhanced ultrasound (CEUS)--ready for research projects and routine clinical use.

With contrast-enhanced ultrasound (CEUS) now established as a valuable imaging modality for many applications, a more specific demand has recently emerged for quantifying perfusion and using measured parameters as objective indicators for various disease states. However, CEUS perfusion quantification remains challenging and is not well integrated in daily clinical practice. The development of VueBox™ alleviates existing limitations and enables quantification in a standardized way. VueBox™ operates as an off-line software application, after dynamic contrast-enhanced ultrasound (DCE-US) is performed. It enables linearization of DICOM clips, assessment of perfusion using patented curve-fitting models, and generation of parametric images by synthesizing perfusion information at the pixel level using color coding. VueBox™ is compatible with most of the available ultrasound platforms (nonlinear contrast-enabled), has the ability to process both bolus and disruption-replenishment kinetics loops, allows analysis results and their context to be saved, and generates analysis reports automatically. Specific features have been added to VueBox™, such as fully automatic in-plane motion compensation and an easy-to-use clip editor. Processing time has been reduced as a result of parallel programming optimized for multi-core processors. A long list of perfusion parameters is available for each of the two administration modes to address all possible demands currently reported in the literature for diagnosis or treatment monitoring. In conclusion, VueBox™ is a valid and robust quantification tool to be used for standardizing perfusion quantification and to improve the reproducibility of results across centers.

Nonlinear contrast imaging with an array-based micro-ultrasound system.

The main goal of this study was to determine the optimal strategy for a real-time nonlinear contrast mode for small-animal imaging at high frequencies, on a new array-based micro-ultrasound system. Previously reported contrast imaging at frequencies above 15 MHz has primarily relied on subtraction schemes involving B-mode image data. These approaches provide insufficient contrast to tissue ratios under many imaging conditions. In this work, pulse inversion, amplitude modulation and combinations of these were systematically investigated for the detection of nonlinear fundamental and subharmonic signal components to maximize contrast-to-tissue ratio (CTR) in the 18-24 MHz range. From in vitro and in vivo measurements, nonlinear fundamental detection with amplitude modulation provided optimal results, allowing an improvement in CTR of 13 dB compared with fundamental imaging. Based on this detection scheme, in vivo parametric images of murine kidneys were generated using sequences of nonlinear contrast images after intravenous bolus injections of microbubble suspensions. Initial parametric images of peak enhancement (PE), wash-in rate (WiR) and rise time (RT) are presented. The parametric images are indicative of blood perfusion kinetics, which, in the context of preclinical imaging with small animals, are anticipated to provide valuable insights into the progression of human disease models, where blood perfusion plays a critical role in either the diagnosis or treatment of the disease.

Toll-like receptor-4 is expressed by macrophages in murine and human lipid-rich atherosclerotic plaques and upregulated by oxidized LDL.

BACKGROUND: Inflammation is implicated in atherogenesis and plaque disruption. Toll-like receptor 2 (TLR-2) and TLR-4, a human homologue of drosophila Toll, play an important role in the innate and inflammatory signaling responses to microbial agents. To investigate a potential role of these receptors in atherosclerosis, we assessed the expression of TLR-2 and TLR-4 in murine and human atherosclerotic plaques. METHODS AND RESULTS: Aortic root lesions of high-fat diet-fed apoE-deficient mice (n=5) and human coronary atherosclerotic plaques (n=9) obtained at autopsy were examined for TLR-4 and TLR-2 expression by immunohistochemistry. Aortic atherosclerotic lesions in all apoE-deficient mice expressed TLR-4, whereas aortic tissue obtained from control C57BL/6J mice showed no TLR-4 expression. All 5 lipid-rich human plaques expressed TRL-4, whereas the 4 fibrous plaques and 4 normal human arteries showed no or minimal expression. Serial sections and double immunostaining showed TLR-4 colocalizing with macrophages both in murine atherosclerotic lesions and at the shoulder region of human coronary artery plaques. In contrast to TLR-4, none of the plaques expressed TLR-2. Furthermore, basal TLR-4 mRNA expression by human monocyte-derived macrophages was upregulated by ox-LDL in vitro. CONCLUSIONS: Our study demonstrates that TLR-4 is preferentially expressed by macrophages in murine and human lipid-rich atherosclerotic lesions, where it may play a role to enhance and sustain the innate immune and inflammatory responses. Moreover, upregulation of TLR-4 in macrophages by oxidized LDL suggests that TLR-4 may provide a potential pathophysiological link between lipids and infection/inflammation and atherosclerosis.

Cooperation of Toll-like receptor 2 and 6 for cellular activation by soluble tuberculosis factor and Borrelia burgdorferi outer surface protein A lipoprotein: role of Toll-interacting protein and IL-1 receptor signaling molecules in Toll-like receptor 2 signaling.

Toll-like receptor 2 (TLR2) and TLR4 play important roles in innate immune responses to various microbial agents. We have previously shown that human dermal endothelial cells (HMEC) express TLR4, but very little TLR2, and respond to LPS, but not to Mycobacterium tuberculosis 19-kDa lipoprotein, unless transfected with TLR2. Here we report that HMEC are unresponsive to several additional biologically relevant TLR2 ligands, including, phenol-soluble modulin (PSM), a complex of three small secreted polypeptides from the skin commensal Staphylococcus epidermidis, soluble tuberculosis factor (STF), and Borrelia burgdorferi outer surface protein A lipoprotein (OspA-L). Expression of TLR2 renders HMEC responsive to all these ligands. We further characterized the signaling pathway in response to STF, OspA-L, and PSM in TLR2-transfected HMEC. The TLR2 signaling pathway for NF-kappaB trans-activation shares the IL-1R signaling molecules. Dominant negative constructs of TLR2 or TLR6 inhibit the responses of STF and OspA-L as well as PSM in TLR2-transfected HMEC, supporting the concept of functional cooperation between TLR2 and TLR6 for all these TLR2 ligands. Moreover, we show that Toll-interacting protein (Tollip) coimmunoprecipitates with TLR2 and TLR4 using HEK 293 cells, and overexpression of Tollip inhibits NF-kappaB activation in response to TLR2 and TLR4 signaling. Collectively, these findings suggest that there is functional interaction between TLR2 and TLR6 in the cellular response to STF and OspA-L in addition to S. epidermidis (PSM) Ags, and that engagement of TLR2 triggers a signaling cascade, which shares the IL-1R signaling molecules, similar to the TLR4-LPS signaling cascade. Our data also suggest that Tollip may be an important constituent of both the TLR2 and TLR4 signaling pathways.

Decreased expression of Toll-like receptor-4 and MD-2 correlates with intestinal epithelial cell protection against dysregulated proinflammatory gene expression in response to bacterial lipopolysaccharide.

The lumenal surface of the colonic epithelium is continually exposed to Gram-negative commensal bacteria and LPS. Recognition of LPS by Toll-like receptor (TLR)-4 results in proinflammatory gene expression in diverse cell types. Normally, however, commensal bacteria and their components do not elicit an inflammatory response from intestinal epithelial cells (IEC). The aim of this study is to understand the molecular mechanisms by which IEC limit chronic activation in the presence of LPS. Three IEC lines (Caco-2, T84, HT-29) were tested for their ability to activate an NF-kappaB reporter gene in response to purified, protein-free LPS. No IEC line responded to LPS, whereas human dermal microvessel endothelial cells (HMEC) did respond to LPS. IEC responded vigorously to IL-1beta in this assay, demonstrating that the IL-1 receptor signaling pathway shared by TLRs was intact. To determine the reason for LPS hyporesponsiveness in IEC, we examined the expression of TLR4 and MD-2, a critical coreceptor for TLR4 signaling. IEC expressed low levels of TLR4 compared with HMEC and none expressed MD-2. To determine whether the low level of TLR4 expression or absent MD-2 was responsible for the LPS signaling defect in IEC, the TLR4 or MD-2 gene was transiently expressed in IEC lines. Transient transfection of either gene individually was not sufficient to restore LPS signaling, but cotransfection of TLR4 and MD-2 in IEC led to synergistic activation of NF-kappaB and IL-8 reporter genes in response to LPS. We conclude that IEC limit dysregulated LPS signaling by down-regulating expression of MD-2 and TLR4. The remainder of the intracellular LPS signaling pathway is functionally intact.

Bacterial lipopolysaccharide and IFN-gamma induce Toll-like receptor 2 and Toll-like receptor 4 expression in human endothelial cells: role of NF-kappa B activation.

Toll-like receptor (TLR) 4 has been identified as the primary receptor for enteric LPS, whereas TLR2 has been implicated as the receptor for Gram-positive and fungal cell wall components and for bacterial, mycobacterial, and spirochetal lipoproteins. Vascular endothelial cell (EC) activation or injury by microbial cell wall components such as LPS is of critical importance in the development of sepsis and septic shock. We have previously shown that EC express predominantly TLR4, and have very little TLR2. These cells respond vigorously to LPS via TLR4, but are unresponsive to lipoproteins and other TLR2 ligands. Here we show that LPS, TNF-alpha, or IFN-gamma induce TLR2 expression in both human dermal microvessel EC and HUVEC. Furthermore, LPS and IFN-gamma act synergistically to induce TLR2 expression in EC, and LPS-induced TLR2 expression is NF-kappaB dependent. LPS and IFN-gamma also up-regulate TLR4 mRNA expression in EC. These data indicate that TLR2 and TLR4 expression in ECs is regulated by inflammatory molecules such as LPS, TNF-alpha, or IFN-gamma. TLR2 and TLR4 molecules may render EC responsive to TLR2 ligands and may help to explain the synergy between LPS and lipoproteins, and between LPS and IFN-gamma, in inducing shock associated with Gram-negative sepsis.

Bacterial lipopolysaccharide activates HIV long terminal repeat through Toll-like receptor 4.

In HIV-infected patients, concurrent infections with bacteria and viruses are known to induce HIV replication as assessed by increases in plasma HIV RNA levels. In the present study, we determined the cell surface receptor and molecular mechanisms of enterobacterial LPS-induced HIV transcription. Human dermal microvessel endothelial cells (HMEC) were transfected with an HIV-long terminal repeat (LTR)-luciferase construct and subsequently stimulated with purified bacterial LPS. Our studies demonstrate that human Toll-like receptor 4 (TLR4) mediates LPS-induced NF-kappaB and HIV-LTR activation in HMEC through IL-1 signaling molecules, namely myeloid differentiation protein, IL-1R-associated kinase, TNFR-associated factor, and NF-kappaB-inducing kinase. Cotransfection of HMEC with HIV-LTR-luciferase and TLR4 cDNA from LPS-hyporesponsive C3H/HeJ mice abrogates LPS-induced HIV transcription as does the use of dominant-negative mutants of the IL-1 signaling molecules. Transfection of HMEC with an HIV-LTR-mutant that lacks the NF-kappaB binding site or pretreatment of cells with chemical inhibitors of the NF-kappaB pathway also blocked LPS-induced HIV-LTR transactivation. These data support the conclusion that TLR4 mediates enterobacterial LPS-induced HIV transcription via IL-1 signaling molecules and NF-kappaB activation plays an important role in HIV-LTR transactivation.

Influence of bubble size distribution on the echogenicity of ultrasound contrast agents: a study of SonoVue.

RATIONALE AND OBJECTIVES: To study the relative contributions of different bubble size classes to SonoVue's echogenicity in fundamental acoustic imaging modes. SonoVue is a contrast agent, previously known as BR1, with a bubble size distribution extending from approximately 0.7 to 10 microm. METHODS: A model for the acoustic response of SonoVue was determined and validated for a set of experimental data. This model was used to simulate the acoustic response of a standard batch of SonoVue as the sum of responses of non-overlapping bubble size classes. RESULTS: The simulation was first validated for a standard SonoVue bubble size distribution. When this distribution was considered as five size classes with equal numbers of bubbles, it was found that bubbles smaller than 2 microm accounted for 60% of the total number but contained only 5% of the total gas volume. The simulation results indicated marked differences in the acoustic contributions from these classes, with 80% of the acoustic efficacy provided by bubbles 3 to 9 microm in diameter. The study also compared bubble distributions in number, surface, and volume, with the distribution computed in terms of acoustic efficacy. CONCLUSIONS: This study shows why bubble volume is a much better indicator of SonoVue's efficacy than is bubble count. A low threshold in diameter was found for SonoVue microbubbles at approximately 2 microm, under which size bubbles do not contribute appreciably to the echogenicity at medical ultrasound frequencies.

Bacterial lipopolysaccharide activates NF-kappaB through toll-like receptor 4 (TLR-4) in cultured human dermal endothelial cells. Differential expression of TLR-4 and TLR-2 in endothelial cells.

A missense mutation in the cytoplasmic domain of the Toll-like receptor-4 (TLR-4) has been identified as the defect responsible for lipopolysaccharide (LPS) hyporesponsiveness in C3H/HeJ mice. TLR-4 and TLR-2 have recently been implicated in LPS signaling in studies where these receptors were overexpressed in LPS non-responsive 293 human embryonic kidney cells. However, the signaling role of TLR-4 or TLR-2 in human cells with natural LPS response remains largely undefined. Here we show that human dermal microvessel endothelial cells (HMEC) and human umbilical vein endothelial cells express predominantly TLR-4 but very weak TLR-2 and respond vigorously to LPS but not to Mycobacterium tuberculosis 19-kDa lipoprotein. Transient transfection of non-signaling mutant forms of TLR-4 and anti-TLR-4 monoclonal antibody inhibited LPS-induced NF-kappaB activation in HMEC, while a monoclonal antibody against TLR-2 was ineffective. In contrast to LPS responsiveness, the ability of HMEC to respond to 19-kDa lipoprotein correlated with the expression of TLR-2. Transfection of TLR-2 into HMEC conferred responsiveness to 19-kDa lipoprotein. These data indicate that TLR-4 is the LPS signaling receptor in HMEC and that human endothelial cells (EC) express predominantly TLR-4 and weak TLR-2, which may explain why they do not respond to 19-kDa lipoprotein. The differential expression of TLRs on human EC may have important implications in the participation of vascular EC in innate immune defense mechanisms against various infectious pathogens, which may use different TLRs to signal.

Bacterial lipopolysaccharide activates nuclear factor-kappaB through interleukin-1 signaling mediators in cultured human dermal endothelial cells and mononuclear phagocytes.

Bacterial lipopolysaccharide (LPS)-mediated immune responses, including activation of monocytes, macrophages, and endothelial cells, play an important role in the pathogenesis of Gram-negative bacteria-induced sepsis syndrome. Activation of NF-kappaB is thought to be required for cytokine release from LPS-responsive cells, a critical step for endotoxic effects. Here we investigated the role and involvement of interleukin-1 (IL-1) and tumor necrosis factor (TNF-alpha) signal transducer molecules in LPS signaling in human dermal microvessel endothelial cells (HDMEC) and THP-1 monocytic cells. LPS stimulation of HDMEC and THP-1 cells initiated an IL-1 receptor-like NF-kappaB signaling cascade. In transient cotransfection experiments, dominant negative mutants of the IL-1 signaling pathway, including MyD88, IRAK, IRAK2, and TRAF6 inhibited both IL-1- and LPS-induced NF-kappaB-luciferase activity. LPS-induced NF-kappaB activation was not inhibited by a dominant negative mutant of TRAF2 that is involved in TNF signaling. LPS-induced activation of NF-kappaB-responsive reporter gene was not inhibited by IL-1 receptor antagonist. TLR2 and TLR4 were expressed on the cell surface of HDMEC and THP-1 cells. These findings suggest that a signal transduction molecule in the LPS receptor complex may belong to the IL-1 receptor/toll-like receptor (TLR) super family, and the LPS signaling cascade uses an analogous molecular framework for signaling as IL-1 in mononuclear phagocytes and endothelial cells.

Clinical characteristics and outcome of children with pneumonia attributable to penicillin-susceptible and penicillin-nonsusceptible Streptococcus pneumoniae.

OBJECTIVE: To compare the clinical characteristics, treatment, and outcome of pediatric patients with pneumonia attributable to isolates of Streptococcus pneumoniae that were either susceptible or nonsusceptible to penicillin. DESIGN: Multicenter, retrospective study. SETTING: Eight children's hospitals in the United States. PARTICIPANTS: Two hundred fifty-four children with pneumococcal pneumonia identified from patients enrolled in the United States Pediatric Multicenter Pneumococcal Surveillance Study during the 3-year period from September 1, 1993 to August 31, 1996. OUTCOME MEASURES: Demographic and clinical variables including necessity for and duration of hospitalization, frequency of chest tube placement, antimicrobial therapy, susceptibility of isolates, and clinical outcome. RESULTS: There were 257 episodes of pneumococcal pneumonia that occurred in 254 patients. Of the 257 isolates, 22 (9%) were intermediate and 14 (6%) were resistant to penicillin; 7 (3%) were intermediate to ceftriaxone and 5 (2%) were resistant to ceftriaxone. There were no differences noted in the clinical presentation of the patients with susceptible versus nonsusceptible isolates. Twenty-nine percent of the patients had a pleural effusion. The 189 (74%) hospitalized patients were more likely to have an underlying illness, multiple lung lobe involvement, and the presence of a pleural effusion than nonhospitalized patients. Fifty-two of 72 hospitalized patients with pleural effusions had a chest tube placed, and 27 subsequently underwent a decortication drainage procedure. Eighty percent of the patients treated as outpatients and 48% of the inpatients received a parenteral second or third generation cephalosporin followed by a course of an oral antimicrobial agent. Two hundred forty-eight of the patients (97.6%) had a good response to therapy. Six patients died; however, only 1 of the deaths was related to the pneumococcal infection. CONCLUSION: The clinical presentation and outcome of therapy did not differ significantly between patients with penicillin-susceptible versus those with nonsusceptible isolates of S pneumoniae. Hospitalized patients were more likely to have underlying illnesses, multiple lobe involvement, and the presence of pleural effusions than patients who did not require hospitalization. In otherwise normal patients with pneumonia attributable to penicillin-resistant pneumococcal isolates, therapy with standard beta-lactam agents is effective.

Pediatric pneumococcal bone and joint infections. The Pediatric Multicenter Pneumococcal Surveillance Study Group (PMPSSG).

OBJECTIVE: To describe the clinical and microbiological characteristics of infants and children with bone and joint infections caused by penicillin-susceptible and penicillin-nonsusceptible strains of Streptococcus pneumoniae. DESIGN: Multicenter, prospective patient accrual; retrospective chart review of identified patients. SETTING: Eight children's hospitals in the United States. PARTICIPANTS: Forty-two children with bone and/or joint infections prospectively enrolled in the United States Pediatric Multicenter Pneumococcal Surveillance Study from September 1, 1993 to August 31, 1996. OUTCOME MEASURES: Data were collected on multiple variables, including age, gender, race, days of symptoms before and during hospitalization, antibiotic and surgical therapy, laboratory and imaging studies. RESULTS: Of the 42 children enrolled (21 bone, 21 joint infections), 14 had isolates that were not susceptible to penicillin. Eight of 16 (50%) strains isolated from children who received antibiotics within 4 weeks before hospitalization were not susceptible to penicillin, compared with 4 of 15 (27%) strains isolated from children without previous antibiotic exposure. Clinical response to therapy was similar between children infected by penicillin-susceptible strains compared with those infected by penicillin-nonsusceptible strains, including duration of hospitalization (9.1 days vs 11.2 days), days of intravenous antibiotic therapy (25.3 days vs 24.6 days), days of fever (3.6 days vs 3.1 days), and sequelae (14% vs 7%). The most commonly prescribed single agents for parenteral therapy in definitive treatment were ceftriaxone (36%), penicillin (15%), and clindamycin (15%). Oral therapy followed parenteral therapy in 56% of children. The mean (+/- standard deviation) duration of total antibiotic therapy in children with osteomyelitis was 57.5 +/- 48.6 days (range, 23-196 days) and 29.2 +/- 11.8 days (range, 12-67 days) for arthritis. Late sequelae (long-term destructive changes of the bone or joint) were documented in 5 (12%) children, 4 with osteomyelitis, and 1 with arthritis. Sequelae occurred in 30% of children with long bone osteomyelitis associated with infection in the adjacent joint. The age of children with sequelae was younger than those without sequelae (6.4 months vs 18.6 months). CONCLUSIONS: The demographic characteristics and anatomic sites of infection in our patients were similar to previously published series collected from single institutions before the emergence of significant antibiotic resistance in S pneumoniae. Our analysis suggests that children infected by penicillin-nonsusceptible strains have a similar clinical response to therapy when compared with children infected by penicillin-susceptible strains.

Three-year multicenter surveillance of pneumococcal meningitis in children: clinical characteristics, and outcome related to penicillin susceptibility and dexamethasone use.

OBJECTIVES: To evaluate the antibiotic susceptibility of Streptococcus pneumoniae isolates obtained from the blood and cerebrospinal fluid of children with meningitis. To describe and compare the clinical and microbiological characteristics, treatment, and outcome of children with meningitis caused by S pneumoniae based on antimicrobial susceptibility of isolates and the administration of dexamethasone. DESIGN AND PATIENTS: Children with pneumococcal meningitis were identified from among a group of patients with systemic infections caused by S pneumoniae who were enrolled prospectively in the United States Pediatric Multicenter Pneumococcal Surveillance Study at eight children's hospitals in the United States. From September 1, 1993 to August 31, 1996, 180 children with 181 episodes of pneumococcal meningitis were identified and data were collected by retrospective chart review. OUTCOME: Clinical and laboratory characteristics were assessed. All pneumococcal isolates were serotyped and antibiotic susceptibilities for penicillin and ceftriaxone were determined. Clinical presentation, hospital course, and outcome parameters at discharge were compared between children infected with penicillin-susceptible isolates and those with nonsusceptible isolates and for children who did and did not receive dexamethasone. RESULTS: Fourteen (7.7%) of 180 children died; none of the fatalities were because of a documented failure of treatment caused by a resistant strain. Only 1 child, who had mastoiditis and a lymphangioma, experienced a bacteriologic failure with a penicillin-resistant (minimum inhibitory concentration = 2 microgram/mL) organism. Of the 166 surviving children, 41 (25%) developed neurologic sequelae (motor deficits) and 48 (32%) of 151 children had unilateral (n = 26) or bilateral (n = 22) moderate to severe hearing loss at discharge. Overall, 12.7% and 6.6% of the pneumococcal isolates were intermediate and resistant to penicillin and 4.4% and 2.8% were intermediate and resistant to ceftriaxone, respectively. Clinical presentation, cerebrospinal fluid indices on admission, and hospital course, morbidity, and mortality rates were similar for patients infected with penicillin- or ceftriaxone-susceptible versus nonsusceptible organisms. However, the relatively small numbers of nonsusceptible isolates and the inclusion of vancomycin in the treatment regimen for the majority of the patients limit the power of this study to detect significant differences in outcome between patients infected with susceptible and nonsusceptible isolates. Nonetheless, our results show that the nonsusceptible organisms do not seem to be intrinsically more virulent. Forty children (22%) received dexamethasone (>/=8 doses) initiated before or within 1 hour after the first dose of antibiotics. The incidence of any moderate or severe hearing loss was significantly higher in the dexamethasone group (46%) compared with children not receiving any dexamethasone (23%). The incidence of any neurologic deficits, including hearing loss, also was significantly higher in the dexamethasone group (55% vs 33%). However, children in the dexamethasone group more frequently required intubation and mechanical ventilation and had lower initial concentration of glucose in the cerebrospinal fluid than children who did not receive any dexamethasone. When we controlled for the confounding factor, severity of illness (intubation), the incidence of any deafness and of any neurologic sequelae, including deafness, were no longer significantly different between children who did or did not receive dexamethasone. CONCLUSIONS: Children with pneumococcal meningitis caused by penicillin- or ceftriaxone-nonsusceptible organisms and those infected by susceptible strains had similar clinical presentation and outcome. The use of dexamethasone was not associated with a beneficial effect in this retrospective and nonrandomized study. (ABSTRACT TRUNCATED)

Endotoxin-induced migration of monocytes and PECAM-1 phosphorylation are abrogated by PAF receptor antagonists.

The trafficking of monocytes across the endothelial lining of the blood vessel increases in response to bacterial infection at sites of inflammation. However, the molecular events involved in the diapedesis of monocytes in response to endotoxin are not completely understood. Our studies revealed that signaling by lipopolysaccharide (LPS) in human umbilical vein endothelial cells (HUVEC) resulted in a threefold increase in the transendothelial migration of monocyte-like HL-60 cells and a sevenfold increase in the phosphorylation of platelet endothelial cell adhesion molecule-1 (PECAM-1). The transmigration induced by LPS was inhibited by an antibody to PECAM-1. Both the phosphorylation of PECAM-1 and transendothelial migration of monocytes were inhibited by a platelet-activating factor (PAF) receptor antagonist, indicating the autocrine effect of PAF in these events. Treatment of HUVEC with LPS caused a fourfold increase in PAF receptor mRNA expression that was completely blocked by the PAF receptor antagonist. We conclude that PAF, generated by HUVEC in response to LPS or gram-negative bacterial infection, acts in an autocrine manner, causing PECAM-1 phosphorylation and thus the transendothelial migration of monocytes.

Three-year multicenter surveillance of systemic pneumococcal infections in children.

OBJECTIVE: To track antibiotic susceptibility of Streptococcus pneumoniae isolates obtained from children with systemic infections and determine outcome of treatment. DESIGN: A 3-year (September 1993 through August 1996) prospective surveillance study of all invasive pneumococcal infections in children. PATIENTS: Infants and children cared for at eight children's hospitals in the United States with culture-proven systemic pneumococcal infection. RESULTS: One thousand two hundred ninety-one episodes of systemic pneumococcal infection were identified in 1255 children. An underlying illness was present in the children for 27% of the episodes. The proportion of isolates that were nonsusceptible to penicillin or ceftriaxone increased annually and nearly doubled throughout the 3-year period; for the last year the percentages of isolates nonsusceptible to penicillin and ceftriaxone were 21% and 9.3%, respectively. There was no difference in mortality between patients with penicillin-susceptible or nonsusceptible isolates. Only 1 of 742 patients with bacteremia had a repeat blood culture that was positive > 1 day after therapy was started. All 24 normal children with bacteremia attributable to isolates resistant to penicillin had resolution of their infection; the most common treatment regimen was a single dose of ceftriaxone followed by an oral antibiotic. CONCLUSIONS: The percentage of pneumococcal isolates nonsusceptible to penicillin and ceftriaxone increased yearly among strains recovered from children with systemic infection. Because empiric antibiotic therapy already has changed for suspected pneumococcal infections, antibiotic resistance has not been associated with increased mortality. Careful monitoring of antibiotic susceptibility and outcome of therapy is necessary to continually reassess current recommendations for treatment.