2022 Volume 71 Issue 4 Pages 725-730
Lactococcus lactis is the most used species in the health food industry, including probiotics. A 74-year-old man presented to our hospital with decreased consciousness. He was hospitalized on suspicion of bacterial pneumonia and congestive heart failure. Blood cultures prepared on admission showed gram-positive chained cocci after 16 h. On hospitalization day 3, the blood cultures showed α-Streptococcus-like colonies positive for bile esculin (BE) and negative for catalase. Moreover, no aggregation was observed in the Lancefield classification test. Therefore, Enterococcus was speculated temporarily as the causative pathogen. On hospitalization day 4, this pathogen was identified using an automatic analyzer as L. lactis subsp lactis, which was consistent with the results of matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). On hospitalization day 27, the patient’s condition improved after the administration of ABPC/SBT and CTRX; consequently, he was discharged from the hospital. L. lactis is BE-positive and can be easily mistaken for Enterococcus. Therefore, for its accurate identification, it is necessary to use an automatic analyzer and MALDI-TOF MS. In this case, the patient had hypoplasia of the spleen and had a history of daily intake of dairy products. It was considered that L. lactis translocated into the bloodstream through an unknown mechanism, resulting in the development of sepsis.
