Antibiotic use during influenza infection augments lung eosinophils that impair lung immunity against secondary bacterial pneumonia
Ontology highlight
ABSTRACT: A leading cause of morbidity and mortality during influenza infection is the development of a secondary bacterial pneumonia, which is appropriately treated with antibiotics. In the absence of a bacterial superinfection, prescribing antibiotics is not indicated but has nevertheless become a common clinical practice for those presenting with a respiratory viral illness. We found that antibiotic use during an antecedent influenza infection impaired the lung innate immunologic defenses toward a secondary challenge with methicillin-resistantStaphylococcus aureus(MRSA). The antibiotics perturbed the gut microbiome causing a fungal dysbiosis that drives an increase in lung eosinophils. We also demonstrate eosinophils, through the release of major basic protein, impair macrophage ability to clear MRSA. Moreover, we provide clinical evidence that eosinophils positively correlate with antibiotic use and worsened outcomes in patients hospitalized for viral infections. Altogether, our work establishes a counterproductive effect of antibiotic treatment during influenza infection that have negative immunologic consequences in the lungs thereby increasing the risk of developing a secondary bacterial infection.
Project description:A leading cause of morbidity and mortality during influenza infection is the development of a secondary bacterial pneumonia, which is appropriately treated with antibiotics. In the absence of a bacterial superinfection, prescribing antibiotics is not indicated but has nevertheless become a common clinical practice for those presenting with a respiratory viral illness. We found that antibiotic use during an antecedent influenza infection impaired the lung innate immunologic defenses toward a secondary challenge with methicillin-resistantStaphylococcus aureus(MRSA). The antibiotics perturbed the gut microbiome causing a fungal dysbiosis that drives an increase in lung eosinophils. We also demonstrate eosinophils, through the release of major basic protein, impair macrophage ability to clear MRSA. Moreover, we provide clinical evidence that eosinophils positively correlate with antibiotic use and worsened outcomes in patients hospitalized for viral infections. Altogether, our work establishes a counterproductive effect of antibiotic treatment during influenza infection that have negative immunologic consequences in the lungs thereby increasing the risk of developing a secondary bacterial infection.
Project description:Secondary bacterial infections (SBIs) exacerbate influenza-associated disease and mortality. Antimicrobial agents can reduce the severity of SBIs, but many have limited efficacy or cause adverse effects. Thus, new treatment strategies are needed. Kinetic models describing the infection process can help determine optimal therapeutic targets, the time scale on which a drug will be most effective, and how infection dynamics will change under therapy. To understand how different therapies perturb the dynamics of influenza infection and bacterial coinfection and to quantify the benefit of increasing a drug’s efficacy or targeting a different infection process, I analyzed data from mice treated with an antiviral, an antibiotic, or an immune modulatory agent with kinetic models. The results suggest that antivirals targeting the viral life cycle are most efficacious in the first 2 days of infection, potentially because of an improved immune response, and that increasing the clearance of infected cells is important for treatment later in the infection. For a coinfection, immunotherapy could control low bacterial loads with as little as 20 % efficacy, but more effective drugs would be necessary for high bacterial loads. Antibiotics targeting bacterial replication and administered 10 h after infection would require 100 % efficacy, which could be reduced to 40 % with prophylaxis. Combining immunotherapy with antibiotics could substantially increase treatment success. Taken together, the results suggest when and why some therapies fail, determine the efficacy needed for successful treatment, identify potential immune effects, and show how the regulation of underlying mechanisms can be used to design new therapeutic strategies.
Model is encoded by Ruby and submitted to BioModels by Ahmad Zyoud
Project description:Influenza-induced respiratory failure is substantially worsened by secondary bacterial infections such as methicillin-resistant Staphylococcus aureus (MRSA). The bidirectional interaction between the influenza-injured lung microenvironment and MRSA is poorly understood. By conditioning MRSA ex vivo in bronchoalveolar lavage (BAL) fluid collected from mice at various timepoints of influenza infection, we found that influenza-injured lung microenvironment induces MRSA to increase cytotoxin expression while decreasing metabolic pathways. This overall increase in MRSA virulence was dependent upon SaeRS, a bacterial two-component system. Once expressed by MRSA, these influenza-induced toxins (such as Hla and LukAB) interact with host heparan sulfate (HS) fragments shed into the airspace. Highly-sulfated HS fragments augmented Hla- and LukAB-toxicity in vitro and in vivo. Our findings indicate that post-influenza MRSA pneumonia is shaped by bidirectional host-pathogen interactions: host injury triggers changes in bacterial expression of toxins, the activity of which are then shaped by host-derived HS fragments.
Project description:Influenza infection is substantially worsened by the onset of secondary pneumonia caused by bacteria such as methicillin-resistant Staphylococcus aureus (MRSA). The bidirectional interaction between the influenza-injured lung microenvironment and MRSA is poorly understood. By conditioning MRSA ex vivo in bronchoalveolar lavage fluid collected from mice at various timepoints of influenza infection, we found that the influenza-injured lung microenvironment dynamically induces MRSA to increase cytotoxin expression while decreasing metabolic pathways. LukAB, a SaeRS two-component system dependent cytotoxin, is particularly important to the severity of post-influenza MRSA pneumonia. LukAB’s activity is likely shaped by the post-influenza lung microenvironment, as LukAB binds to (and is activated by) heparan sulfate (HS) oligosaccharide sequences shed from the epithelial glycocalyx after influenza. Our findings indicate that post-influenza MRSA pneumonia is shaped by bidirectional host-pathogen interactions: host injury triggers changes in bacterial expression of toxins, the activity of which may be shaped by host-derived HS fragments.
Project description:Influenza is the common respiratory problem that infects between 5-20% of the US population and results in 30,000 deaths annually. A primary cause of the influenza-associated death is due to secondary bacterial pneumonia. In this study, we investigated the role of STAT2 signaling during influenza and influenza-bacterial super-infection in mice. Herein, we demonstrate that STAT2 signaling is required for viral control, regulation of inflammation, and limiting mortality during influenza single infection. Surprisingly, despite this deficiency in anti-viral immunity, we found increased bacterial control and survival in STAT2 deficient mice during influenza-MRSA super-infection compared to controls. This protection in the absence of STAT2 was associated with accumulation of dual phenotype M1/M2 macrophages, which were required for control of bacterial infection. Together, these results suggest that the STAT2 signaling is involved in suppressing macrophage activation and bacterial control during influenza-bacterial super-infection.
Project description:Methicillin-resistant Staphylococcus aureus (MRSA) is a major threat to human health. Rather than depend on creating new antibiotics (to which bacteria will eventually become resistant), we are employing antibiotic adjuvants that potentiate existing antibiotics. Based on our previous work, loratadine, the FDA-approvide antihistamine, effectively potentiates cell-wall active antibiotics in multiple strains of MRSA. Furthermore, loratadine and oxacillin helped disrupt preformed biofilms and stop them from initially forming in vitro. To gain biological insight into how this potentiation and biofilm inhibition occurs, we used RNA-seq on treated MRSA 43300 cultures to examine antibiotic adjuvant affects transcritome-wide.
Project description:Influenza infections result in a significant number of severe illnesses annually, many of which are complicated by secondary bacterial super-infection. Primary influenza infection has been shown to increase susceptibility to secondary methicillin-resistant Staphylococcus aureus (MRSA) infection by altering the host immune response, leading to significant immunopathology. Type III interferons (IFNs), or IFNλs, have gained traction as potential antiviral therapeutics due to their restriction of viral replication without damaging inflammation. The role of IFNλ in regulating epithelial biology in super-infection has recently been established; however, the impact of IFNλ on immune cells is less defined. In this study, we infected wild-type and IFNLR1-/- mice with influenza A/PR/8/34 followed by S. aureus USA300. We demonstrated that global IFNLR1-/- mice have enhanced bacterial clearance through increased uptake by phagocytes, which was shown to be cell-intrinsic specifically in myeloid cells in mixed bone marrow chimeras. We also showed that depletion of IFNLR1 on CX3CR1 expressing myeloid immune cells, but not neutrophils, was sufficient to significantly reduce bacterial burden compared to mice with intact IFNLR1. These findings provide insight into how IFNλ in an influenza-infected lung impedes bacterial clearance during super-infection and show a direct cell intrinsic role for IFNλ signaling on myeloid cells.
Project description:Antibiotic resistance genes expressed in the upper respiratory tract of patients infected with influenza viruses were associated with the microbial community and microbial activities. Interactions between the host systemic responses to influenza infection and ARG expression highlight the importance of antibiotic resistance in viral-bacterial co-infection.
Project description:Antibiotic resistance genes expressed in the upper respiratory tract of patients infected with influenza viruses were associated with the microbial community and microbial activities. Interactions between the host systemic responses to influenza infection and ARG expression highlight the importance of antibiotic resistance in viral-bacterial co-infection.
Project description:Antibiotic resistance genes expressed in the upper respiratory tract of patients infected with influenza viruses were associated with the microbial community and microbial activities. Interactions between the host systemic responses to influenza infection and ARG expression highlight the importance of antibiotic resistance in viral-bacterial co-infection.