Alistipes Bacteremia in Older Patients with Digestive and Cancer Comorbidities, Japan, 2016-2023.

The clinical characteristics of Alistipes bacteremia remain insufficiently understood. We retrospectively analyzed 13 cases of Alistipes bacteremia at a tertiary care center in Japan. Of the 13 patients, 7 were male and 6 female; 10 were >65 years of age. Of 9 patients with comorbidities, 7 had solid tumors or hematological malignancies and 11 had gastrointestinal symptoms. Isolates identified were Alistipes finegoldii in 4 cases, A. onderdonkii in 4, A. putredinis in 3, A. indistinctus in 2, and A. ihumii in 1. Ten strains exhibited low MICs against β-lactam/β-lactamase inhibitors and metronidazole. We observed high MICs against penicillin, ceftriaxone, and minocycline. Several strains harbored antimicrobial resistance genes, including adeF, tet(Q), cfxA3, cfxA4, and ermG. Twelve patients received β-lactam/β-lactamase inhibitors; 2 patients with solid tumors experienced septic shock and died. Alistipes bacteria can translocate from the gastrointestinal tract into the bloodstream, particularly in cases of inflammation, obstruction, or perforation, leading to severe infections.