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Volume 31, Number 7—July 2025
Dispatch
Multisystemic Disease and Septicemia Caused by Presumptive Burkholderia pseudomallei in American Quarter Horse, Florida, USA
Figure 3

Figure 3. Immunohistochemical examination of tissues from American quarter horse with multisystemic disease and septicemia caused by presumptive Burkholderia pseudomallei, Florida, USA. Photomicrographs show immunohistochemistry for monoclonal antibodies 3A2 (A), 4C7 (B), 4C4 (C), and 5B4 (D) of the submandibular lymph node. A) Intra-phagocytic bacilli demonstrated strong immunoreactivity to 3A2 monoclonal antibody to B. pseudomallei lipopolysaccharides (LPS) O-Ag B/B2 (black arrows). Original magnification ×100. B) Intra-phagocytic bacilli were diffusely immunonegative for 4C7 monoclonal antibody to B. pseudomallei LPS O-ag serotype A. Original magnification ×40. C) Intra-phagocytic bacilli demonstrated weak multifocal immunoreactivity to 4C4 monoclonal antibody to B. pseudomallei capsular polysaccharides (black arrows). Original magnification ×100. D) Intra-phagocytic bacilli demonstrated strong immunoreactivity to 5B4 monoclonal antibody to B. pseudomallei LPS O-Ag B/B2 (black arrows). Original magnification ×100. Bacilli were immunonegative to 3D11 (not shown) monoclonal antibody to Bm LPS O-Ag.