Clinical characteristics and antibiotic susceptibility of Lactobacillus bacteremia: A retrospective analysis

Lactobacillus bacteremia (LB) is an uncommon cause of infection in immunocompetent individuals, owing to its low pathogenicity. However, bacteremia has been reported in immunocompromised patients. In Japan, clinical data on the characteristics and antimicrobial susceptibility of LB remain limited. Hence, a retrospective analysis was conducted at our institution to address this gap.

Patients in whom Lactobacillus spp. were identified from blood cultures at the Aichi Medical University Hospital between April 2018 and March 2025 were included in our study. Clinical characteristics and antimicrobial susceptibility profiles of the isolates were retrospectively analyzed.

A total of 17 patients (13 men and 4 women) were included in the study and all patients received antibiotic treatment. The most common bacterial species detected was Lacticaseibacillus paracasei (47.1 %). All isolates exhibited 100.0 % susceptibility to ampicillin. Risk factors were present in 82.4 % of patients, and concomitant polymicrobial infections occurred in 70.6 % of the cohort. Candida spp. were the most frequently identified organisms in polymicrobial infections (33.3 %). Six patients (35.3 %) died within 30 days after bacteremia diagnosis, with a median time to death of 26.5 days (range, 2.0-1468.0 days).

The detection rate of L. paracasei in this study was higher than that reported in countries outside of Asia. High susceptibility to penicillin was maintained, suggesting that penicillin remains to be an appropriate choice for both empirical and definitive therapy in Japan.