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April 13, 2022

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Probiotics: Might Not Be Safe for All?

Reviewed by Terri Stillwell, MD

With studies exploring the role the microbiome plays in health, the benefits of probiotics have been analyzed in various scenarios, from antibiotic-associated diarrhea to necrotizing enterocolitis. In a recent study, published in Infection Control & Hospital Epidemiology, the authors offer a cautionary tale of probiotic use in immune-compromised patients.

In a retrospective case series, the authors investigated a cluster of Lactobacillus bacteremia in pediatric hematopoietic cell transplant (HCT) recipients and its potential relation to probiotic use. Starting in July 2018, probiotic use was approved for HCT patients who had gut graft-vs-host disease (gGVHD), C. difficile infection, or colonization with multidrug-resistant organisms. From August to November 2019, six patients were identified as having Lactobacillus bacteremia, an increased incidence from years past, prompting an investigation.

During the 4-month time period, 34 hospitalized HCT patients received at least one day of probiotics; of those patients, six (17.6%) were subsequently bacteremic with Lactobacillus. In those who developed bacteremia, they were a median of +41 (range, 6-103) days post-transplant; three patients had MDRO colonization, two patients had both MDRO colonization and gGVHD, and one had no indication for probiotic use.

Using multilocus sequence typing, relatedness between patient blood isolates and probiotic isolates was evaluated. Five patient isolates were available for analysis. Of those, three patient isolates were found to be identical to isolates from the probiotics being used. One patient isolate was only one allele different from a probiotic isolate and, therefore, considered related.

This study showed a seemingly causal relationship between a cluster of Lactobacillus bacteremias and Lactobacillus isolates from probiotics used at the time of infection.  While the mechanism of infection could not be determined, the authors speculated infections were likely due to disruption of mucosal barriers or potential cross-contamination of central venous catheters. Additional studies would be needed to gain a better understanding of the relative risk of bacteremia with probiotic use. Until then, probiotic use in immune-compromised patients should be done cautiously, weighing patient risks and benefits.

(Gilliam et al. Infect Control Hosp Epidemiol. Published online Feb. 28, 2022.)

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