The present disclosure provides binding proteins (e.g., antibodies or antigen binding fragments thereof) that specifically bind to Klebsiella pneumoniae O1 and induce opsonophagocytic killing of Klebsiella (e.g., Klebsiella pneumoniae). The present disclosure also provides methods of reducing Klebsiella (e.g., Klebsiella pneumoniae) or treating or preventing Klebsiella (e.g., Klebsiella pneumoniae) infection in a subject comprising administering the Klebsiella pneumoniae O1 binding proteins, (e.g., antibodies or antigen-binding fragments thereof) to the subject.
