Secondary Infection In Patients Hospitalized With Influenza A(H1N1)pdm09Virus Infection In Mainland China

ObjectiveTo analyze secondary infection fraction and the most common isolated pathogens inhospitalized patients for influenza A(H1N1)pdm09virus infection. To evaluate its effecton mortality and explore possible predictors for secondary infection in hospitalizedpatients for influenza A(H1N1)pdm09virus infection. To assess the effect of treatmentstrategy (mainly corticosteroid) on secondary infection.MethodsData collected during the previously reported retrospective case cohort study duringSeptember1,2009to December31,2009was further analyzed focusing on secondaryinfection. Kaplan-Meier and multi-variable logistic-regression analysis were used toassess the effect of secondary infection on mortality and explore independent predictorsfor it. ROC curve was used to evaluate the accuracy of the predictors. The associationbetween treatment strategies (mainly including corticosteroid administration and invasivemechanical ventilation) and secondary infection was evaluated using multivariablelogistic regression models.Results354(10.2%) of the3486hospitalized patients for influenza A(H1N1)pdm09virusinfection enrolled were complicated by secondary bacterial or fungal infection. A.baumanmii was the most common isolate in sputum or bronchial aspirates, accountingfor130of354(37%) positive patients. Other commonly isolated organisms in sputum orbronchial aspirates were P. aeruginosa (53/354,15%), S. maltophilia (46/354,13.0%), K.pneumonia (37/354，10.5%), and S. aureus (32/354,9.0%). Secondary infectionsignificantly increased the mortality of hospitalized patients with influenzaA(H1N1)pdm09virus infection (OR=2.75;95%CI,1.525.00; P <0.001). Lymphocytes <800cells/mm3and PaO2/FiO2200on admission have some predictivevalue for secondary infection. Corticosteroid therapy (OR=2.85;95%CI,1.69-4.82; P<0.001) and invasive mechanical ventilation (OR=7.92;95%CI,5.09-12.33); P <0.001) significantly increase the risk of secondary infection. Underlying diseases havecertain effects on the type of secondary bacterial infection.ConclusionsA. baumanmii, P. aeruginosa, P. aeruginosa, K. pneumonia and S. aureus were themost common isolated pathogens in hospitalized patients with influenza A(H1N1)pdm09virus infection. Secondary infection is one of the important reasons for the increasedmortality of hospitalized patients with influenza A(H1N1)pdm09virus infection.Lymphocytes <800cells/mm3and PaO2/FiO2200on admission might predictsecondary infection and have certain value in guiding the prophylactic administration ofantibiotics. Corticosteroid significantly increases the risk of secondary infection, whichshould not be used unless a randomized, double-blind clinical trial provides data that theyare beneficial for the treatment of acute lung injury from viral pneumonia.