Background: Pseudonocardia spp. are an aerobic actinomycetes which have not been reported as the causing organism in human infection. We reported the first case of human infection due to Pseudonocardia oroxyli causing suppurative sialadenitis in a patient with idiopathic thrombocytopenic purpura (ITP) and splenectomised with prolonged corticosteroid use.
Methods: Case report: A 57-year-old Thai female was admitted to a university hospital with a palpable painful mass in right submandibular gland for a week. She was diagnosed of ITP for 40 years and was splenectomised 30 year ago. Therefore, the disease has been controlled by prednisolone 2.5 mg/day. Six years ago, she was admitted due to fever and painful mass in right submandibular gland with purulent discharge from Wharton's duct. Sialolisthesis was found in the duct by sialography. Amoxicillin/clavulanate was prescribed for 2 months with nearly complete recovery, consequently, she lost to follow up. A week prior to this admission, the painful mass and purulent discharge from right Wharton's duct recurred with low-graded fever. Pus was collected for stain and culture which Gram stain shown Gram positive beaded-like filamentous branching bacteria while modified acid-fast and acid-fast stain were negative. Subsequently, Nocardia sp. was identified from aerobic culture whereas anaerobic cultured was negative. Pseudonocardia oroxyli was identified by 16 s rDNA sequencing from bacterial colony. Amoxicillin/clavulanate was prescribed according to the susceptibility test. Surgical removal of right submandibular gland was performed which shown yellowish stone in dilated salivary duct. The histopathology of submandibular gland demonstrated clumps of Gram positive filamentous branching bacteria in the dilated duct which also negative on modified acid-fast stain.
Results: The patient was successfully treated with amoxicillin/clavulanate for 6 months without recurrent infection after discontinued antibiotic for 6 months.
Conclusion: Discussion: Pseudonocardia sp. has not been reported as the causing organism of human infection before. It has been isolated from various habitats such as tree bark and coastal sediment which there was no contact history in the patient. From the conventional method that isolated Nocardia spp. which negative on modified acid-fast stain should be aware of Pseudonocardia oroxyli. The 16 s rDNA sequencing is necessary for identification the organism.
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