• Yingmiao Zhang, Yan Jiang, Yu Zhan, Hui Wang, Tian Qin, and Zhongxin Lu.
• Department of Medical Laboratory, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
• Medicine (Baltimore). 2022 Dec 2; 101 (48): e32108e32108.

BackgroundMicrococcus yunnanensis (M. yunnanensis) is an endophytic actinomycete that was originally isolated from the roots of Polyspora axillaris in 2009, and no human infections caused by this organism have yet been reported. We report the first case of community-acquired pneumonia caused by M. yunnanensis and propose that M. yunnanensis should be considered as an emerging pathogen in medical practice. A 30-year-old woman was admitted to our hospital with fever, paroxysmal dry cough with sputum, and pharyngalgia. Laboratory tests revealed an increase in several inflammatory indicators, and a computerized tomography scan of the chest showed scattered infection foci in both lungs. Bronchoalveolar lavage fluid was collected via bronchoscopy for microbial culture and pathological examination.MethodsThe isolate from bronchoalveolar lavage fluid was identified as M. yunnanensis by 16S rRNA gene sequencing. The patient was diagnosed with community-acquired pneumonia based on the diagnostic criteria.ResultsThe patient was treated with intravenous amoxicillin/clavulanate potassium, levofloxacin hydrochloride tablets, and compound methoxyphenamine capsules on the day after admission. After 3 days of treatment, the patient's physiological conditions and inflammatory indicators normalized, and 6-month follow-up showed no abnormalities.ConclusionAlthough the pathogenicity of M. yunnanensis is unclear, the present case indicates an emerging pathogen in medical practice. MALDI-TOF MS has a limited ability to identify novel or rare pathogenic species, and 16S rRNA gene sequencing is of great value in some circumstance.Copyright © 2022 the Author(s). Published by Wolters Kluwer Health, Inc.

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