D107-18 A Rare Case of Legionella Longbeachae Endocarditis

Abstract Introduction Legionella longbeachae is a gram-negative bacillus that rarely causes clinical disease, but when it does, it is most often associated with lung infections. Extrapulmonary manifestations are rare. Here, we present a case of Legionnaires disease from Legionella longbeachae complicated by endocarditis of the mitral valve. Case Description A 53-year-old woman with type 1 diabetes status post failed pancreas transplant and 9 months post kidney transplant on prednisone 5 mg and tacrolimus 4 mg daily was admitted with one week of nausea, vomiting, and diarrhea. Labs were notable for hyponatremia to 120 mEq/L and oliguric acute kidney injury of the transplanted kidney. She was intubated for hypoxemia with initial P/F of 183 mmHg and initiated on two vasopressors for septic shock. Chest CT showed large bilateral consolidative opacities with scattered nodules. Meropenem and azithromycin were started empirically for suspected pneumonia. However, initial infectious workup, including blood cultures, bronchoalveolar lavage lower respiratory tract PCR, and urine antigen testing were negative for all pathogens. Lumbar puncture was done due to encephalopathy and was unremarkable. Her hypoxemia and shock improved marginally on empiric antibiotics. Serum microbial cell-free DNA sequencing first returned positive for Legionella longbeachae, followed by bronchoalveolar lavage culture on Buffered Charcoal Yeast Extract (BCYE). Azithromycin was transitioned to levofloxacin based on sequencing with rapid improvement of her P/F to 690 mmHg. She was subsequently weaned off pressors. Her course was complicated by a 0.4 cm acute cerebellar stroke concerning for septic embolic origin, so transesophageal echocardiography was obtained. It showed a 0.5 cm vegetation on the anterior mitral annulus. She was extubated on hospital day 11, transferred out of the ICU, and discharged to acute inpatient rehabilitation with plans to complete 6 months of levofloxacin. Discussion Diagnosis of Legionella longbeachae infection is challenging and requires a high pretest suspicion due to a lack of available point of care lab tests. Urine antigen testing and standard lower respiratory tract PCR tests primarily identify Legionella pneumophila, but not other Legionella species. This case demonstrates the importance of pursuing dedicated Legionella cultures on BCYE when clinical suspicion is high despite negative initial testing. Additionally, Legionella longbeachae usually causes pulmonary infections, but its ability to cause extrapulmonary manifestations, including endocarditis, should not be overlooked. This case highlights the usefulness of metagenomic sequencing in immunocompromised patients with rare manifestations of infection. One must recognize the limitations of diagnostic testing, especially when results contradict the clinical picture. This abstract is funded by: None