Proteus mirabilis infective endocarditis is a rare disease with only 17 reported cases. It is typically associated with urinary tract infections (UTIs), staghorn calculi, and/or asymptomatic bacteriuria. We present a case of a 73-year-old male who presented with positive blood cultures for Proteus mirabilis but with a negative urinalysis and urine culture. He presented with acute renal failure and required hemodialysis. TTE was remarkable for a 30% ejection fraction, and no vegetations were visualized. TEE demonstrated a small vegetation on the left aortic valve. The initial urine culture remained negative throughout his hospitalization. He was treated with IV antibiotics and discharged without hemodialysis.

Lactococcus lactis infections are rarely reported in the medical literature. L. lactis is a commonly used fermenting agent which may be difficult to identify with common microbiology identification processes. This factor may contribute to its lack of recognition in medical journals. We report a case of an immunosuppressed 80-year-old female with L. lactis bacteremia, subsequently, found to have aortic valve vegetation, who responded clinically to a six-week duration of ceftriaxone therapy. Afterward, a brief updated literature review is presented on L. lactis infections.