Item Details

title

MECHANISMS OF KLEBSIELLA PNEUMONIAE GASTROINTESTINAL COLONIZATION

author

Bray, Andrew Scott

abstract

Klebsiella pneumoniae is considered a pathobiont, as it is capable of long term asymptomatic gastrointestinal (GI) colonization in healthy individuals but can cause potentially life-threatening illness in immunocompromised patients. However, GI colonization with an intact microbiome has been long neglected in the study of this pathobiont, presenting a gap in our understanding of the pathogenic life-cycle of K. pneumoniae. The work herein utilizes our novel murine model of K. pneumoniae GI colonization with an intact microbiome. Using a technique that mimics the natural route of infection, we were able to establish asymptomatic GI colonization of K. pneumoniae without the use of antibiotics. We first utilized this murine model to interrogate a mutant of K. pneumoniae that is resistant to colistin, an antibiotic of last resort used in treatment of infections caused by multi-drug resistant (MDR) strains. We demonstrated that deleting the gene encoding the small regulatory protein MgrB (MgrB-) results in colistin resistance, but is also associated with reduced colonization burden in the gut. However, MgrB- K. pneumoniae displayed a higher environmental survival rate that correlated with an increase in transmission efficiency. We next sought to identify factors of K. pneumoniae that allow it to overcome microbiota mediated colonization resistance (CR). Leveraging our murine model and an insertional transposon mutagenesis screen (INSeq), we identified 470 genes that were considered critical for gut colonization. We validated that the antimicrobial type VI secretion system (T6SS), identified in our screen, is a mediator of K. pneumoniae GI colonization. A metagenomics screen of fecal samples from K. pneumoniae colonized mice identified Betaproteobacteria species as potential prey for its T6SS. Additionally, we identified the novel direct regulation of the T6SS of K. pneumoniae via three transcriptional regulators that respond to environmental cues in the gut. Our results suggest that K. pneumoniae uses specific environmental cues in the gut as a signals to modulate the expression of its T6SS, allowing it to reduce the burden of commensals and promoting niche occupancy. Together, this work elucidates key mechanisms of K. pneumoniae GI colonization and transmission, two clinically relevant steps of the pathogens life cycle.

subject

Antibiotic resistance

Bacterial pathogenesis

Klebsiella pneumoniae

Microbiology

Microbiome

Transmission

contributor

Zafar, Muhammad A. (advisor)

Tamayo, Rita (committee member)

Grayson, Jason (committee member)

Haas, Karen (committee member)

Westcott, Marlena (committee member)

date

2024-02-13T09:36:09Z (accessioned)

2025-02-12T09:30:08Z (available)

2024 (issued)

degree

Microbiology & Immunology (discipline)

embargo

2025-02-12 (terms)

identifier

http://hdl.handle.net/10339/102915 (uri)

language

en (iso)

publisher

Wake Forest University

type

Dissertation