Incidental Splenic Granuloma Due to Burkholderia pseudomallei: A Case of Asymptomatic Latent Melioidosis?

Abstract

Abstract. We report a rare case of an asymptomatic latent melioidosis lesion in a posttraumatic splenectomy specimen from a diabetic patient. The 2-cm yellowish, lobulated lesion was found in the splenic parenchyma well away from the traumatized areas. Microscopically, it consisted of a central area of necrosis and exudate surrounded by macrophages, epithelioid cells, lymphocytes, and occasional multinucleated giant cells. Burkholderia bacilli were detected by a novel in situ hybridization (ISH) assay, and confirmed by polymerase chain reaction and sequencing to be Burkholderia pseudomallei. As melioidosis was not suspected initially, bacterial culture was not done but electron microscopy showed morphologically viable and dividing bacilli in the lesion. Moreover, the surgical wound became infected with B. pseudomallei several days post-surgery. After treatment with ceftazidime and trimethoprim/sulfamethoxazole, the wound infection cleared. We believe this could be a unique case of asymptomatic latent melioidosis in the spleen. In endemic countries, chronic granulomas should be investigated for B. pseudomallei infection, and if available, ISH may be helpful for diagnosis.

Multinucleated Giant Cell Formation as a Portal to Chronic Bacterial Infections

“…The transient re-activation of persister bacteria would shut down the cytoprotection and manipulation exhibited by Bpm and cause the MNGC to undergo cell death, creating foci of necrosis and inflammation, like the ones seen at the center of the mature granuloma-like lesions of chronic melioidosis patients. As previously stated, MNGCs have been found in the granuloma-like structures of chronic infections but mostly on the perimeter of the central necrotic core that houses most of the bacteria [4,37]. This is consistent with granuloma structure in M. tuberculosis infection where MNGCs are scattered throughout the periphery of the epithelioid cells, foamy macrophages, and lymphocytes.…”

Splenic granuloma: Melioidosis or Tuberculosis?

“…The surgical specimen biopsy showed typical granuloma which could not be differentiated from TB based on histopathology. [ 5 ] Chronic melioidosis may appear as granulomas on imaging and histopathology and can mimic other granulomatous diseases. This reiterates the importance of culture-based diagnosis.…”

Multinucleated Giant Cell Formation as a Portal to Chronic Bacterial Infections

“…As previously stated, MNGCs have been found in the granuloma-like structures of chronic Bpm infections but mostly on the perimeter of the central necrotic core that houses most of the bacteria [ 4 , 44 ]. This is consistent with the granuloma structure in M. tuberculosis infection where MNGCs are scattered throughout the periphery of the epithelioid cells, foamy macrophages, and lymphocytes.…”