DOI: https://doi.org/10.36347/sjmcr.2025.v13i06.003

Pages: 1314-1316

Lactococcus lactis, recognized for its role in dairy culture, is commonly regarded as non-pathogenic and is extensively used in the production of various fermented dairy products. However, rarely documented as a human pathogen, we present a case of bacterial endocarditis attributed to Lactococcus lactis subsp. lactis in patient with a cyanotic congenital heart disease. The case involves a 21-year-old patient with a medical history of NYHA stage II dyspnea, admitted with exacerbated dyspnea, arthralgia, and prolonged fever. Clinical examination revealed significant findings, including a holosystolic murmur, transthoracic echocardiogram showed Atrioventricular discordance and ventriculoarterial discordance with double outlet right ventricle and presence of a vegetation responsible for severe pulmonary insufficiency. Positive anaerobic blood cultures identified Gram-positive cocci with catalase-negative properties and alpha-hemolysis on blood agar, subsequently confirmed as Lactococcus lactis through MALDI-TOF MS analysis. The isolate was sensitive to ampicillin, ceftriaxone, clindamycin, erythromycin, vancomycin, gentamycine and fluoroquinolone. Despite its usual classification as nonpathogenic, this case emphasizes Lactococcus lactis's potential to cause systemic infections, particularly noteworthy considering exposure to raw or fermented milk products that can increase susceptibility in individuals with compromised immune systems. Further investigations are essential to discern specific virulence factors associated with Lactococcus lactis, while highlighting the value of MALDI-TOF in rapide and precise identification, aiding in early therapeutic interventions and judicious antibiotic use.