Ventilator-associated pneumonias in children (I)–diagnostic criteria, etiology and pathogenesis

Department of Pediatrics and Medical Genetics, Medical University, Plovdiv.
Folia medica 08/2012; 54(1):5-11.
Source: PubMed


Ventilator-associated pneumonias have been estimated to be the second most common nosocomial infections among children treated in intensive care units. They occur in mechanically ventilated patients through intubation tube or tracheostomy, the inflammation usually involving the lung parenchyma. The ventilator-associated pneumonia is associated with a longer antibiotic treatment, greater duration of mechanical ventilation (MV) and higher mortality rates in children. The condition is also associated with a higher cost of the treatment. This paper reviews and comments in detail the criteria formulated by the National Nosocomial Infection Surveillance (NNSI) and the Centers for Disease Control and Prevention (CDC) for diagnosis of ventilator-associated pneumonias in children. The disease etiology is associated with the typical causes of nosocomial infections in this age: P. aeruginosa, E. coli and K. pneumoniae. The pathogenesis of the condition is inadequately studied but the aspiration of gastric contents and immune deficiency are proven risk factors. Two mechanisms have a major role in the development of the disease--micro-aspiration of gastric contents and colonization of the lower airways with pathogens.

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    • "are gram-negative bacteria and important opportunistic pathogens causing life-threatening nosocomial infections [1,2]. Typical clinical presentations of Klebsiella pneumonia are nosocomial respiratory tract infections, urinary tract infections, infections of the bloodstream and premature infant intensive care unit infections [1,3-6]. Multidrug resistant Klebsiella pneumonia strains are becoming an increasingly relevant medical problem worldwide with limited clinical treatment options [7-11]. "
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    ABSTRACT: Klebsiella pneumoniae is a leading cause of severe hospital-acquired respiratory tract infections and death but little is known regarding the modulation of respiratory dendritic cell (DC) subsets. Plasmacytoid DC (pDC) are specialized type 1 interferon producing cells and considered to be classical mediators of antiviral immunity. By using multiparameter flow cytometry analysis we have analysed the modulation of respiratory DC subsets after intratracheal Klebsiella pneumonia infection. Data indicate that pDCs and MoDC were markedly elevated in the post acute pneumonia phase when compared to mock-infected controls. Analysis of draining mediastinal lymph nodes revealed a rapid increase of activated CD103+ DC, CD11b+ DC and MoDC within 48 h post infection. Lung pDC identification during bacterial pneumonia was confirmed by extended phenotyping for 120G8, mPDCA-1 and Siglec-H expression and by demonstration of high Interferon-alpha producing capacity after cell sorting. Cytokine expression analysis of ex vivo-sorted respiratory DC subpopulations from infected animals revealed elevated Interferon-alpha in pDC, elevated IFN-gamma, IL-4 and IL-13 in CD103+ DC and IL-19 and IL-12p35 in CD11b+ DC subsets in comparison to CD11c+ MHC-class IIlow cells indicating distinct functional roles. Antigen-specific naive CD4+ T cell stimulatory capacity of purified respiratory DC subsets was analysed in a model system with purified ovalbumin T cell receptor transgenic naive CD4+ responder T cells and respiratory DC subsets, pulsed with ovalbumin and matured with Klebsiella pneumoniae lysate. CD103+ DC and CD11b+ DC subsets represented the most potent naive CD4+ T helper cell activators. These results provide novel insight into the activation of respiratory DC subsets during Klebsiella pneumonia infection. The detection of increased respiratory pDC numbers in bacterial pneumonia may indicate possible novel pDC functions with respect to lung repair and regeneration.
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