2009 pandemic influenza A (H1N1) in critically ill children in Cincinnati, Ohio.

OBJECTIVE: To compare the clinical features, management, and outcome of critically ill children with H1N1 to children with seasonal influenza from the previous three influenza seasons. DESIGN: The overall number of hospitalizations and the proportion cared for in the pediatric intensive care unit during the H1N1 epidemic period and the three previous influenza seasons (2007-2009) were determined. Medical records of patients admitted to the pediatric intensive care unit with H1N1 and seasonal influenza infection were reviewed. SETTING: Cincinnati Children's Hospital Medical Center, a large, 523-bed hospital located in Cincinnati. PATIENTS: Hospitalized children with laboratory-confirmed seasonal or H1N1 infection. MEASUREMENTS: Study variables included demographic data (age, gender), clinical factors (weight, Pediatric Risk of Mortality III scores, presenting signs and symptoms, comorbid conditions), management (length of mechanical ventilation, other treatments, including high-frequency oscillatory ventilatory support, inhaled nitric oxide, or extracorporeal membrane oxygenation), and outcome (overall and pediatric intensive care unit length of stay and mortality). MAIN RESULTS: Overall, 312 children were hospitalized with H1N1 and 222 with seasonal influenza from the three previous seasons. Children with H1N1 infection were significantly less likely to require pediatric intensive care unit care compared to children with seasonal influenza infection (14% vs. 24%, p = .02). Compared to children with seasonal influenza, children in the pediatric intensive care unit with H1N1 were older (median age in months 107 vs. 68, p = .05) and significantly more likely to have comorbid conditions (64% vs. 40%, p = .03), especially respiratory conditions. While there were no significant differences in severity of illness by Pediatric Risk of Mortality III scores or pediatric intensive care unit length of stay, children with H1N1 were significantly less likely to have acute respiratory failure (p = .04) or die compared to children with seasonal influenza infection (p = .03). CONCLUSIONS: In contrast to other studies, we found that critically ill children with H1N1 had a significantly lower morbidity and mortality compared to children with seasonal influenza.

Zinc supplementation alters airway inflammation and airway hyperresponsiveness to a common allergen.

BACKGROUND: Zinc supplementation can modulate immunity through inhibition of NF-κB, a transcription factor that controls many immune response genes. Thus, we sought to examine the mechanism by which zinc supplementation tempers the response to a common allergen and determine its effect on allergic airway inflammation. METHODS: Mice were injected with zinc gluconate prior to German cockroach (GC) feces (frass) exposure and airway inflammation was assessed. Primary bone marrow-derived neutrophils and DMSO-differentiated HL-60 cells were used to assess the role of zinc gluconate on tumor necrosis factor (TNF)α expression. NF-κB:DNA binding and IKK activity were assessed by EMSA and in vitro kinase assay. Protein levels of A20, RIP1 and TRAF6 were assessed by Western blot analysis. Establishment of allergic airway inflammation with GC frass was followed by administration of zinc gluconate. Airway hyperresponsiveness, serum IgE levels, eosinophilia and Th2 cytokine production were assessed. RESULTS: Administration of zinc gluconate prior to allergen exposure resulted in significantly decreased neutrophil infiltration and TNFα cytokine release into the airways. This correlated with decreased NF-κB activity in the whole lung. Treatment with zinc gluconate significantly decreased GC frass-mediated TNFα production from bone-marrow derived neutrophils and HL-60 cells. We confirmed zinc-mediated decreases in NF-κB:DNA binding and IKK activity in HL-60 cells. A20, a natural inhibitor of NF-κB and a zinc-fingered protein, is a potential target of zinc. Zinc treatment did not alter A20 levels in the short term, but resulted in the degradation of RIP1, an important upstream activator of IKK. TRAF6 protein levels were unaffected. To determine the application for zinc as a therapeutic for asthma, we administered zinc following the establishment of allergic airway inflammation in a murine model. Zinc supplementation decreased airway hyperresponsiveness and serum IgE levels, but had no effect on Th2 cytokine expression. CONCLUSIONS: This report suggests that the mechanism by which zinc supplementation alters NF-κB activity is via the alteration of A20 activity. In addition, this study provides evidence that supplementation of zinc to asthmatics may alter airway reactivity and serum IgE levels, suggesting zinc supplementation as a potential treatment for asthmatics.

Staphylococcus aureus aconitase inactivation unexpectedly inhibits post-exponential-phase growth and enhances stationary-phase survival.

Staphylococcus aureus preferentially catabolizes glucose, generating pyruvate, which is subsequently oxidized to acetate under aerobic growth conditions. Catabolite repression of the tricarboxylic acid (TCA) cycle results in the accumulation of acetate. TCA cycle derepression coincides with exit from the exponential growth phase, the onset of acetate catabolism, and the maximal expression of secreted virulence factors. These data suggest that carbon and energy for post-exponential-phase growth and virulence factor production are derived from the catabolism of acetate mediated by the TCA cycle. To test this hypothesis, the aconitase gene was genetically inactivated in a human isolate of S. aureus, and the effects on physiology, morphology, virulence factor production, virulence for mice, and stationary-phase survival were examined. TCA cycle inactivation prevented the post-exponential growth phase catabolism of acetate, resulting in premature entry into the stationary phase. This phenotype was accompanied by a significant reduction in the production of several virulence factors and alteration in host-pathogen interaction. Unexpectedly, aconitase inactivation enhanced stationary-phase survival relative to the wild-type strain. Aconitase is an iron-sulfur cluster-containing enzyme that is highly susceptible to oxidative inactivation. We speculate that reversible loss of the iron-sulfur cluster in wild-type organisms is a survival strategy used to circumvent oxidative stress induced during host-pathogen interactions. Taken together, these data demonstrate the importance of the TCA cycle in the life cycle of this medically important pathogen.