What does this research mean for the field?

Bifidobacterium, a common commensal gut bacterium, can cause opportunistic bacteremia and septic shock in severely immunocompromised adults, likely through bacterial translocation. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

This case presents a rare instance of septic shock caused by Bifidobacterium bacteremia in an adult with HIV/AIDS.

May 20, 2026

A50-09 When Good Bugs Go Bad: Septic Shock Secondary to Bifidobacterium Bacteremia in an Adult Patient

Key Points

This case presents a rare instance of septic shock caused by Bifidobacterium bacteremia in an adult with HIV/AIDS.
Reported a case of a 36-year-old male with septic shock due to Bifidobacterium bacteremia.
Utilized blood cultures and imaging to identify the source of infection.
Administered a 14-day course of appropriate antibiotics following identification.
Blood cultures confirmed Bifidobacterium bacteremia alongside MRSA pneumonia.
Completion of antibiotic treatment led to the resolution of septic shock and recovery.
Prior cases of Bifidobacterium bacteremia are exceedingly rare in immunocompromised adults.

Abstract

Abstract Introduction The Bifidobacterium genus comprises gram-positive anaerobic bacteria that typically contain more than 50% guanine and cytosine nucleotides in their DNA.1 Members of this genus are some of the first bacteria to colonize the infant gastrointestinal tract and can comprise up to 90% of the total bacterial population.2 As the intestinal microbiome becomes more heterogeneous over time, bifidobacterium species continue to play a commensal role and have even been proposed as a probiotic, added to several foods and supplements. 3 In rare cases, these commensal bacteria can result in opportunistic infections, as we present in this case of septic shock secondary to Bifidobacterium bacteremia. Case Report A 36-year-old male with a past medical history of HIV/AIDS (non-compliant with ART, CD4 20, HIV RNA 1.3 million) was admitted to the ICU with septic shock after being found down for an unknown duration. He was intubated for acute hypoxic respiratory failure and airway protection. Initial chest x-ray showed bilateral patchy opacifications, which was indicative of community-acquired pneumonia as the source of sepsis. The tracheal aspirate grew methicillin-resistant Staphylococcus aureus. Hospitalization was complicated by abdominal distention and persistent fevers; computed tomography of the abdomen with contrast revealed inflammation and a small amount of free air, which were managed non-operatively. Blood cultures were positive for Bifidobacterium. Vancomycin was transitioned to linezolid, completing a 14-day course of antibiotic coverage for Bifidobacterium and MRSA pneumonia with resolution of shock. Discussion Opportunistic infections secondary to Bifidobacterium are exceedingly rare. Even in infants, whose microbiomes are nearly entirely Bifidobacterium, the incidence of bacteremia secondary to Bifidobacterium breve was found to be two percent in a retrospective study of 298 infants in a NICU. 4 The incidence drops precipitously in adults, with only intermittent case reports being described in literature, and typically found in immunocompromised patients. However, even this is rarely observed, as evidenced by a cohort study of hematopoietic cell transplant recipients, which found zero cases of bacteremia among 3,796 patients over a 10-year period. 5 His history of HIV, CD4 count less than 20, and abdominal imaging consistent with colonic inflammation make bacterial translocation the likely source of his bacteremia. Bifidobacterium remains rare and challenging to identify due to the limitations of rapid identification methods; however, should be considered in immunocompromised patients with septic shock. History of probiotic exposure and abdominal physical examination changes may serve as a nidus for translocation. This abstract is funded by: none

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