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Introduction: Although non-tuberculous mycobacterium (NTM) infection accounts for only a small proportion of fever of unknown origin (FUO) cases, it has become a more common etiology in recent years. Therefore, we reviewed FUO patients with underlying NTM infection to better understand its clinical features. Methodology: The medical records of patients presenting with FUO and diagnosed with NTM infection admitted to Peking Union Medical College Hospital between January 2016 and June 2021 were reviewed. The clinical information of patients whose follow-up data were available were summarized. Specimens submitted for pathogenic identification were processed by mycobacterial culture, acid-fast staining, and mycobacterial nucleic acid detection. IBM SPSS Statistics v22.0 (SPSS, Inc., Chicago, IL, USA) was used for data analysis. Results: Fifty-five FUO patients were diagnosed with NTM infection (55/785; 7.0% of FUO cases). Patients were mostly middle-aged men and had a relatively long disease course. Seven, 29, and 54 patients had previously no respondence to glucocorticoids, immunosuppressants, and multiple antibiotics, respectively; their inflammatory indexes were significantly increased; and there was no obvious risk of immunosuppression in this group, who were likely to be T.SPOT-TB negative (33/41; 80.5%). The most commonly identified NTM was Mycobacterium intracellulare followed by Mycobacterium chelonae/abscessus, Mycobacterium kansasii, and Mycobacterium avium. Conclusions: Microbiological investigations including culture, acid-fast staining, NTM nucleic acid examination, and next-generation sequencing were performed to confirm the diagnosis of NTM in FUO patients. FUO patients should screen for NTM infections so that this important etiology can be recognized, targeted treatments administered early, and outcomes improved. [ABSTRACT FROM AUTHOR]

Introduction: Q fever is a worldwide zoonosis caused by Coxiella burnetii. Atypical presentations of Q fever can cause diagnostic difficulty or be misdiagnosed. Here we compared the clinical and diagnostic features of Q fever endocarditis and endocarditis caused by other bacteria to identify features of Q fever endocarditis that might facilitate early diagnosis. Methodology: This was a retrospective case-control study of eight cases of Q fever endocarditis diagnosed between 2000 and 2018 at Peking Union Medical College Hospital in China and 24 age- and gender-matched patients diagnosed with bacterial endocarditis over the same period. Clinical and laboratory data were collected and compared between groups. Results: The median time interval between symptoms and diagnosis was significantly longer in the case group than the control group (8.0 months (IQR 7.0-16.0) vs. 4.0 months (IQR 1.0-7.0); p = 0.002). Patients in case group had significantly lower white blood cell counts (5.8 ± 2.4 × 109/L vs. 10.0 ± 3.4 × 109/L; p = 0.003), percentage of neutrophil (62.4 ± 14.7% vs. 79.1 ± 9.2%; p = 0.014), high-sensitivity C-creative protein levels (21.1 mg/L (IQR 18.5-32.8) vs. 45.3 mg/L (IQR 32.9-54.3); p = 0.038), and platelet counts (133 ± 73 vs. 229 ± 65; p = 0.001) but higher levels of rheumatoid factor (104.3 U/L (IQR 99.0-132.8) vs. 10.2 U/L (IQR 6.9-32.5); p = 0.011) than controls. Elevated creatinine (50.0% vs. 12.5%; p = 0.047) and liver enzymes (50.0% vs. 0%; p = 0.002) were more common in cases than controls. Q fever endocarditis was less frequently diagnosed than controls before cardiac surgery (62.5% vs. 100%; p = 0.011), with negative blood cultures in all cases. Conclusions: The diagnosis of Q fever endocarditis can easily be delayed compared to other causes of infectious endocarditis. Patients with chronic fever and new valve dysfunction require careful assessment, especially when presenting with negative blood cultures and high rheumatoid factor levels. Clinical and laboratory evaluation of these patients should include routine serological testing for C. burnetii. [ABSTRACT FROM AUTHOR]