Early Diagnosis of Streptococcus cristatus in Blood Culture-Negative Infective Endocarditis by Capture-Based Metagenomic Next-Generation Sequencing: A Case Report

Dong WangHui WangDan ZhangXinsheng Yan^*

• Department of Clinical Laboratory, Wuhan Asia General Hospital, Wuhan Asia General Hospital Affiliated to Wuhan University of Science and Technology, Wuhan University of Science and Technology, Wuhan, China

Background: Infective endocarditis (IE) is a life-threatening infectious cardiac condition characterized by therapeutic complexity and high mortality rates, for which precise pathogen identification is critical to guide accurate treatment. Although this disease is frequently caused by commensal microorganisms of the oral flora, including Streptococcus cristatus (S. cristatus); however, S. cristatus is not a common pathogen associated with IE.Case presentation: A 59-year-old male patient was admitted to our intensive care unit due to chest tightness and shortness of breath persisting for 10 days, with symptoms worsening over the last 6 hours, including dyspnea and an inability to lie down. After the patient was admitted to the hospital for comprehensive examinations, a preliminary 2 clinical diagnosis of IE, aortic valve vegetation formation, acute non-ST-segment elevation myocardial infarction, and heart failure was established. The patient had negative preoperative blood culture results and received empiric therapy with moxifloxacin combined with piperacillin-tazobactam for infection control, subsequently undergoing cardiac surgery. Intraoperatively obtained valve vegetations were sent for pathological testing, tissue bacterial culture, and capture-based mNGS (metagenomic next-generation sequencing) testing. The capture-based mNGS results for the vegetation was returned as S. cristatus within 24 hours, with 250,119 sequences detected and 54.56% coverage, which facilitated the rapid identification of the pathogenic microorganism of IE in the early stage. The tissue culture result of the vegetation was returned on the 5th day of delivery, confirming the presence of S. cristatus. The patient was successfully discharged after comprehensive treatment and returned to the hospital 3 weeks postdischarge for a follow-up examination, which suggested a good recovery.Conclusions: This case highlights a rare instance of S. cristatus endocarditis, which was ultimately confirmed at an early stage through capture-based mNGS performed on valvular vegetation. This suggests that for postoperative patients with persistent infection and blood culture-negative IE, valvular capture-based mNGS serves as a rapid and efficient diagnostic tool to expedite pathogen identification and guide targeted antimicrobial therapy.