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Stuivenberg et al. Microbiome Res Rep 2025;4:11 https://dx.doi.org/10.20517/mrr.2024.22 Page 13 of 18

such as inflammation, but were not performed in atherosclerosis patients. Therefore, while these strains
show promise in managing some of the factors associated with atherosclerosis, they must be tested in an
appropriate cohort. As such, our current suggestions will focus on how to design new studies to identify and
assess useful probiotic strains to treat atherosclerosis.

Finding new strains
In an ideal situation, performing in vitro experiments before any human or animal studies would assist in
identifying beneficial strains with specific target activities related to atherosclerosis. However, as we have
mentioned, studies often rely on commercially available strains rather than those recognized for their
specific traits.

We believe that the identification of strains relevant to atherosclerosis, or any other disease should follow a
series of simple steps. First, strains should be sequenced to identify useful genes harbored within their
genetic content. The utility of these genes should then be proven by demonstrating the activity in vitro (e.g.,
reduction in uremic toxins or serum cholesterol). Strains with sufficient activity can then be assessed using
relevant cell culture and animal models. The final step would then be to perform a well-designed clinical
trial in an appropriate population of humans (i.e., individuals with a certain disease or condition). Certainly,
this concise set of steps represents a more appropriate selection process than choosing bacterial strains
based solely on availability. However, it is crucial to highlight that this method of strain selection overlooks
the essential need to assess each strain for stability and safety before introducing it to a group of at-risk
individuals (i.e., atherosclerosis patients). The discussion on how to conduct these evaluations on probiotic
strains is omitted here as it has been comprehensively addressed elsewhere [110-113] .

HOW SHOULD STRAINS BE ASSESSED CLINICALLY?
When evaluating strains in clinical settings, researchers should utilize randomized, double-blind placebo-
controlled studies to reduce bias. Trials should ideally be carried out in target populations, in this case,
atherosclerosis patients, alongside standard treatments to avoid interfering with patients’ medical care. To
date, only a handful of clinical trials have investigated how probiotics directly influence atherosclerosis
patients, with most of the research being conducted in mouse or rat models. While these studies
demonstrate the feasibility of the approach, they do not provide concrete evidence to support the
widespread adoption of a specific strain or product.

After identifying beneficial strains with proven clinical efficacy against atherosclerosis, the challenge of
determining how to assess the results of various strains emerges. Should the focus be on probiotics that
alleviate inflammation or promote cholesterol clearance? Is a combination of strains more effective than one
alone? The answer is not straightforward, and in fact, the existence of a “one-size-fits-all” probiotic for
atherosclerosis is unlikely. Individuals respond differently to the physiological challenges of atherosclerosis,
as demonstrated by the existence of a protected phenotype [Figure 1], and thus, patients may also have
similar responses to treatment wherein one patient might benefit more from a cholesterol-reducing
probiotic while another might respond better to that with anti-inflammatory action. By assembling a diverse
range of strains with various activities against atherosclerosis symptoms and risk factors, this potential issue
could be overcome.

CONCLUSIONS
This review focused on highlighting the potential for probiotics to protect against both the traditional and
non-traditional risk factors of atherosclerosis. Probiotics show promise as therapies for atherosclerosis, with
the possibility of plaque stabilization and a reduced risk of cardiovascular events. The microbial