Pulmonary matrix metalloproteinase-9 activity in mechanically ventilated children with respiratory syncytial virus.

Respiratory syncytial virus (RSV) infection is a potent stimulus for airway epithelial expression of matrix metalloproteinase (MMP)-9. MMP-9 activity in vivo is a predictor of disease severity in children with RSV-induced respiratory failure. Human airway epithelial cells were infected with RSV A2 strain and analysed for MMP-9 and tissue inhibitor of metalloproteinase (TIMP)-1 (a natural inhibitor of MMP-9) release. In addition, endotracheal samples from children with RSV-RF and controls (non-RSV pneumonia and nonlung disease controls) were analysed for MMP-9, TIMP-1, human neutrophil elastase and myeloperoxidase activity. RSV infection of airway epithelia was sufficient to rapidly induce MMP-9 transcription and protein release. Pulmonary MMP-9 activity peaked at 48 h in infants with RSV-induced respiratory failure. In the RSV group, MMP-9 activity and MMP-9/TIMP-1 ratio imbalance predicted higher oxygen requirement and worse paediatric risk of mortality scores. The highest levels of human neutrophil elastase and myeloperoxidase activity were measured in the RSV cohort; however, unlike MMP-9, these neutrophil markers failed to predict disease severity. These results support the hypothesis that RSV is a potent stimulus for MMP-9 expression and release from human airway epithelium, and that MMP-9 is an important biomarker of disease severity in mechanically ventilated children with RSV lung infection.

Matrix metalloproteinase activity in pediatric acute lung injury.

Pediatric Acute Lung Injury (ALI) is associated with a high mortality and morbidity, and dysregulation of matrix metalloproteinases (MMPs) may play an important role in the pathogenesis and evolution of ALI. Here we examined MMP expression and activity in pediatric ALI compared with controls. MMP-8, -9, and to a lesser extent, MMP-2, -3, -11 and -12 were identified at higher levels in lung secretions of pediatric ALI patients compared with controls. Tissue Inhibitor of Matrix metalloproteinase-1 (TIMP-1), a natural inhibitor of MMPs was detected in most ALI samples, but MMP-9:TIMP-1 ratios were high relative to controls. In subjects who remained intubated for >or=10 days, MMP-9 activity decreased, with > 80% found in the latent form. In contrast, almost all MMP-8 detected at later disease course was constitutively active. Discriminating MMP-9:TIMP-1 ratios were found in those who had a prolonged ALI course. These results identify a specific repertoire of MMP isoforms in the lung secretions of pediatric ALI patients, and demonstrate inverse changes in MMPs -8 and -9 with protracted disease.

Is hyperglycemia really harmful? A critical appraisal of "Persistent hyperglycemia in critically ill children" by Faustino and Apkon (J Pediatr 2005; 146:30-34).

OBJECTIVE: To review the findings and to discuss the implications of hyperglycemia in critically ill children. DESIGN: A critical appraisal of an article with literature review. FINDINGS: In this single-center, retrospective cohort study, the authors report that the prevalence of hyperglycemia ranged from 16.7% to 75%, depending on the cutoff values (120 mg/dL, 150 mg/dL, and 200 mg/dL), among nondiabetic children admitted to a pediatric intensive care unit. Hyperglycemia correlated with an increased in-hospital mortality rate (relative risk, 2.5; 95% confidence interval, 1.26-4.93 for maximum glucose within 24 hrs, >150 mg/dL; and relative risk, 5.68; 95% confidence interval, 1.38-23.47 for highest glucose within 10 days, >120 mg/dL), as well as a longer length of stay in the pediatric intensive care unit. This finding is in concordance with other adult and pediatric studies. However, without adjustment for severity of illness, the study does not distinguish cause and effect, nor does it address the role of strict glucose control in this group of patients. CONCLUSIONS: This study adds to the growing body of knowledge that associates the timing, intensity, duration, and variability of glycemia with outcomes in critically ill children. However, its limitations restrict drawing causal relationships and prevents insights regarding therapy.

Matrix Metalloproteinase-9 Mediates RSV Infection in Vitro and in Vivo.

Respiratory Syncytial Virus (RSV) is an important human pathogen associated with substantial morbidity and mortality. The present study tested the hypothesis that RSV infection would increase matrix metalloproteinase (MMP)-9 expression, and that MMP-9 inhibition would decrease RSV replication both in vitro and in vivo. RSV A2 infection of human bronchial epithelial cells increased MMP-9 mRNA and protein release. Cells transfected with siRNA against MMP-9 following RSV infection had lower viral titers. In RSV infected wild-type (WT) mice, MMP-9, airway resistance and viral load peaked at day 2 post infection, and remained elevated on days 4 and 7. RSV infected MMP-9 knockout (KO) mice had decreased lung inflammation. On days 2 and 4 post inoculation, the RSV burden was lower in the MMP-9 KO mice compared to WT controls. In conclusion, our studies demonstrate that RSV infection is a potent stimulus of MMP-9 expression both in vitro and in vivo. Reduction of MMP-9 (via siRNA knockdown, and in MMP-9 KO mice) resulted in decreased viral replication. Our findings suggest MMP-9 is a potential therapeutic target for RSV disease.

Chromobacterium Violaceum Sepsis: Rethinking Conventional Therapy to Improve Outcome.

BACKGROUND: Chromobacterium violaceum (C. violaceum) is a facultative anaerobic gram-negative bacterium found in soil and water, especially in tropical and subtropical areas. Although infection in humans is rare, it is associated with significant morbidity. The bacterium is known for its resistance to multiple antimicrobials, and the possibility of relapse and reinfection. Presence of bacteremia, disseminated infection, and ineffective antimicrobial agents are predictors of mortality. CASE REPORT: We report the case of a previously healthy 11-year-old male with C. violaceum sepsis who was exposed to stagnant water. He presented with severe septic shock and developed multi-organ system failure. Initial presumptive diagnosis was staphylococcal infection secondary to presence of skin abscesses resulting in antibiotic coverage with vancomycin, clindamycin, nafcillin and ceftriaxone. He also had multiple lung and liver abscesses. Once C. violaceum was identified, he received meropenem and ciprofloxacin, and was later discharged on ertapenem and trimethoprim-sulfamethoxazole (TMP-SMX) to complete a total of six months of antibiotics. He was diagnosed with chronic granulomatous disease (CGD) and is currently on prophylactic TMP-SMX and itraconazole. He has not had any relapses since his initial presentation. CONCLUSIONS: This case highlights the importance of considering C. violaceum as a relevant human pathogen, and considering it early in temperate regions, particularly in cases of fulminant sepsis associated with multi-organ abscesses. Once C. violaceum is identified, appropriate antimicrobial therapy should be started promptly, and sufficient duration of treatment is necessary for successful therapy.

Early elevation of matrix metalloproteinase-8 and -9 in pediatric ARDS is associated with an increased risk of prolonged mechanical ventilation.

BACKGROUND: Matrix metalloproteinases (MMP) -8 and -9 may play key roles in the modulation of neutrophilic lung inflammation seen in pediatric Acute Respiratory Distress Syndrome (ARDS). We aimed to perform a comprehensive analysis of MMP-8 and MMP-9 activity in tracheal aspirates of pediatric ARDS patients compared with non-ARDS controls, testing whether increased MMP-8 and -9 activities were associated with clinical outcomes. METHODS: Tracheal aspirates were collected from 33 pediatric ARDS patients and 21 non-ARDS controls at 48 hours of intubation, and serially for those who remained intubated greater than five days. MMPs, tissue inhibitor of metalloproteinases (TIMPs), human neutrophil elastase (HNE) and myeloperoxidase (MPO) activity were measured by ELISA, and correlated with clinical indicators of disease severity such as PRISM (Pediatric Risk of Mortality) scores, oxygen index (OI), multi-organ system failure (MOSF) and clinical outcome measures including length of intubation, ventilator-free days (VFDs) and mortality in the Pediatric Intensive Care Unit (PICU). RESULTS: Active MMP-9 was elevated early in pediatric ARDS subjects compared to non-ARDS controls. Higher MMP-8 and active MMP-9 levels at 48 hours correlated with a longer course of mechanical ventilation (r = 0.41, p = 0.018 and r = 0.75, p<0.001; respectively) and fewer number of VFDs (r = -0.43, p = 0.013 and r = -0.76, p<0.001; respectively), independent of age, gender and severity of illness. Patients with the highest number of ventilator days had the highest levels of active MMP-9. MMP-9 and to a lesser extent MMP-8 activities in tracheal aspirates from ARDS subjects were sensitive to blockade by small molecule inhibitors. CONCLUSIONS: Higher MMP-8 and active MMP-9 levels at 48 hours of disease onset are associated with a longer duration of mechanical ventilation and fewer ventilator-free days among pediatric patients with ARDS. Together, these results identify early biomarkers predictive of disease course and potential therapeutic targets for this life threatening disease.