Haemophilus influenzae responds to glucocorticoids used in asthma therapy by modulation of biofilm formation and antibiotic resistance

摘要

AbstractGlucocorticosteroids are used as a main treatment to reduce airway inflammation in people with asthma who suffer from neutrophilic airway inflammation, a condition frequently associated with Haemophilus influenzae colonization. Here we show that glucocorticosteroids have a direct influence on the behavior of H. influenzae that may account for associated difficulties with therapy. Using a mouse model of infection, we show that corticosteroid treatment promotes H. influenzae persistence. Transcriptomic analysis of bacteria either isolated from infected mouse airway or grown in laboratory medium identified a number of genes encoding regulatory factors whose expression responded to the presence of glucocorticosteroids. Importantly, a number of these corticosteroid-responsive genes also showed elevated expression in H. influenzae within sputum from asthma patients undergoing steroid treatment. Addition of corticosteroid to H. influenzae led to alteration in biofilm formation and enhanced resistance to azithromycin, and promoted azithromycin resistance in an animal model of respiratory infection. Taken together, these data strongly suggest that H. influenzae can respond directly to corticosteroid treatment in the airway potentially influencing biofilm formation, persistence and the efficacy of antibiotic treatment.SynopsisTranscriptional and phenotypic analyses show a direct effect of glucocorticosteroids on the behavior of Haemophilus influenzae increasing bacterial persistence and antimicrobial resistance during respiratory infection.The glucocorticosteroid beclomethasone promotes H. influenzae persistence without influencing the host inflammatory response in a mouse model of acute infection.Beclomethasone induces specific alteration in the expression of H. influenzae genes implicated in biofilm formation, host colonization and survival in vivo.Examination of sputum samples from asthma patients undertaking steroid treatment showed many of the same alterations in H. influenzae gene expression as those induced by beclomethasone.Mutation analysis and transcriptome profiling identified the alternate sigma factor RpoE as an element in the glucocortico-steroid response.Mutation of rpoE or addition of glucocorticosteroid to H. influenzae led to alteration in biofilm formation and enhanced resistance to antibiotics in models of respiratory infection.