Bacteraemia and obstructive pyelonephritis caused by Bifidobacterium breve in an elderly woman: a case report and literature review

Abstract

Bifidobacterium spp. are non-spore-forming Gram-positive anaerobes that are indigenous to the human gastrointestinal tract and vagina. They are believed to be non-pathogenic organisms for humans and thus are widely used as probiotics. An 83-year-old woman taking cephalexin for 4 days was diagnosed with obstructive pyelonephritis. Y-branched Gram-positive rods were found in both anaerobic and aerobic blood culture bottles, and in an anaerobic urine culture. Bifidobacterium breve was finally identified. Ceftriaxone and metronidazole were administered to the patient, and she was discharged after intermittent catheterization for dysuria. Urinary tract infection caused by Bifidobacterium spp. is believed to be rare, but it can develop in patients with underlying urological conditions. Recognition of the characteristic morphology and conducting anaerobic urine culture may help in identifying more cases of Bifidobacterium urinary tract infections.

Keywords: Bifidobacterium; Bifidobacterium breve; pyelonephritis; urinary tract infection.

Fig. 1.

Gram-positive rods at 1,000 x magnification from a blood culture bottle sample (Arrow: Y-branched form).

Fig. 2.

Grey and smooth colonies on the ABHK agar plates after 48 h incubation. na, not applicable; F, female; M, male; nd, no data; MALDI-TOF-MS, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry; UTIs, urinary tract infections; BBG-01, Bifidobacterium breve strain Yakult; CTRX, ceftriaxione; ABPC/SBT, ampicillin–sulbactam; CLDM, clindamycin; PCG, penicillin G; CPFX, ciplofloxacin; CTX, cefotaxime; CMZ, cefmetazole; CEZ, cefazolin; VCM, vancomycin; MEPM, meropenem; LZD, linezolid; PIPC/TAZ, piperacillin–tazobactam; MNZ, metronidazole. *Positive bottles are not described in the reference.