Project description:Carbapenem-resistantKlebsiella pneumoniae(CR-Kp) is significant threat to public health worldwide. The primary reservoir for CR-Kp is the intestinal tract, where the bacterium is usually present at low density, but can bloom following antibiotic treatment, mostly in hospital settings. The impact of disturbances in the intestinal environment on the fitness, survival, expansion, and drug susceptibility of this pathogen is not well-understood. Nevertheless, gaining such knowledge could lead to innovative intervention strategies for addressing colonization and infection. Here, we adopted anin vivomodel to examine the transcriptional adaptation of a CR-Kp clinical isolate to immune activation in the intestine. We report that as early as 6 hours following host treatment with anti-CD3 antibody, CR-Kp underwent rapid transcriptional changes including downregulation of genes involved in sugar utilization and amino acid biosynthesis, and upregulation of genes involved in amino acid uptake and catabolism, antibiotic resistance, and stress response. In agreement with these findings, the concentration of oxidative species and amino acids was increased in the mouse intestine following treatment. Genes encoding for proteins containing the domain of unknown function (DUF) 1471 were particularly upregulated, however their deletion did not impair CR-Kp fitness in vivoupon immune activation. Transcription factor enrichment analysis identified the global regulator cAMP-Receptor Protein CRP as a potential orchestrator of the observed transcriptional signature. In keeping with the recognized role of CRP in regulating utilization of alternative carbon sources, CRP deletion in CR-Kp resulted in strongly impaired gut colonization, but this effect was not amplified by immune activation. Thus, following intestinal colonization, which occurs in a CRP-dependent manner, CR-Kp can rapidly respond to immune cues by implementing a well-defined and complex transcriptional program whose direct relevance towards bacterial fitness remains cryptic. Further analyses utilizing this model may identify key factors to tackle the intestinal stage of CR-Kp colonization.
Project description:Antibiotic use can lead to expansion of multi-drug resistant pathobionts within the gut microbiome that can cause life-threatening infections. Selective alternatives to conventional antibiotics are in dire need. Here, we describe a Klebsiella PhageBank that enables the rapid design of antimicrobial bacteriophage cocktails to treat multi-drug resistant Klebsiella pneumoniae. Using a transposon library in carbapenem-resistant K. pneumoniae, we identified host factors required for phage infection in major Klebsiella phage families. Leveraging the diversity of the PhageBank and experimental evolution strategies, we formulated combinations of phages that minimize the occurrence of phage resistance in vitro. Optimized bacteriophage cocktails selectively suppressed the burden of multi-drug resistant K. pneumoniae in the mouse gut microbiome and drove bacterial populations to lose key virulence factors that act as phage receptors. Further, phage-mediated diversification of bacterial populations in the gut enabled co-evolution of phage variants with higher virulence and a broader host range. Altogether, the Klebsiella PhageBank represents a roadmap for both phage researchers and clinicians to enable phage therapy against a critical multidrug-resistant human pathogen.
Project description:Klebsiella pneumoniae (KP) are extracellular Gram-negative bacteria that cause infections in lower respiratory and urinary tract, and bloodstream. STAT1 is a master transcription factor that acts to maintain T-cell quiescence under homeostatic conditions. Although STAT1 helps defend against systemic spread of acute KP intrapulmonary infection, whether STAT1 regulation of T-cell homeostasis impacts pulmonary host defense during acute bacterial infection and injury is less clear. Using a clinical KP respiratory isolate and a pneumonia mouse model, we found STAT1-deficiency led to an early neutrophil-dominant transcriptional profile and neutrophil-recruitment in the lung preceding widespread bacterial dissemination and lung injury development. Yet, myeloid cell STAT1 was dispensable for control of KP proliferation and dissemination, as myeloid cell-specific STAT1-deficient (LysMCre/WT;Stat1fl/fl) mice showed similar bacterial burden in lung, liver, and kidney as WT littermates. Surprisingly, IL-17 producing CD4+ T-cells infiltrated Stat1-/- mice lungs early during KP infection. Increase in Th17-cells in the lung was not due to preexisting immunity against KP and were consistent with circulating rather than tissue-resident CD4+ T-cells. However, blocking global IL17 signaling with anti-IL17-RC administration led to increased proliferation and dissemination of KP, suggesting IL17 provided by other innate immune cells is essential in defense against KP. Contrastingly, depletion of CD4+ T-cells reduced Stat1-/- mice lung bacterial burden indicating early CD4+ T-cell activation in the setting of global STAT1-deficiency is pathogenic. Altogether, our findings suggest STAT1 employs myeloid cell-extrinsic mechanisms to regulate neutrophil responses and provide protection against invasive KP by restricting non-specific CD4+ T-cell activation and immunopathology in the lung.
Project description:Genome-wide identification of RNA polymerase (RNAP) binding sites were performed in Klebsiella pneumoniae MGH 78578 (KP). Anti-RNAP is used to capture the RNAP in KP. ChIP-chip was performed on tiling array specifically made for KP.
Project description:Genome-wide identification of RNA polymerase (RNAP) binding sites were performed in Klebsiella pneumoniae MGH 78578 (KP). Anti-RNAP is used to capture the RNAP in KP. ChIP-chip was performed on tiling array specifically made for KP. Comparison ChIP by anti-RNAP antibody vs ChIP by normal mouse IgG (control, mock IP)
Project description:Infections associated with antimicrobial-resistant bacteria now represent a significant threat to human health using conventional therapy, necessitating the development of alternate and more effective antibacterial compounds. Silver nanoparticles (Ag NPs) have been proposed as potential antimicrobial agents to combat infections. A complete understanding of their antimicrobial activity is required before these molecules can be used in therapy. Lysozyme coated Ag NPs were synthesized and characterized by TEMEDS, XRD, UV-vis, FTIR spectroscopy, zeta potential, and oxidative potential assay. Biochemical assays and deep level transcriptional analysis using RNA sequencing were used to decipher how Ag NPs exert their antibacterial action against multi-drug resistant Klebsiella pneumoniae MGH78578. RNAseq data revealed that Ag NPs induced a triclosan-like bactericidal mechanism responsible for the inhibition of the type II fatty acid biosynthesis. Additionally, released AgC generated oxidative stress both extra and intracellularly in K. pneumoniae. The data showed that triclosan-like activity and oxidative stress cumulatively underpinned the antibacterial activity of Ag NPs. This result was confirmed by the analysis of the bactericidal effect of Ag NPs against the isogenic K. pneumoniae MGH78578 1soxS mutant, which exhibits a compromised oxidative stress response compared to the wild type. Silver nanoparticles induce a triclosan like antibacterial action mechanism in multi-drug resistant K. pneumoniae. This study extends our understanding of anti-Klebsiella mechanisms associated with exposure to Ag NPs. This allowed us to model how bacteria might develop resistance against silver nanoparticles, should the latter be used in therapy.