Survey and Systematic Literature Review of Probiotics Stocked in Academic Medical Centers within the United States

The term probiotic can be used to describe microorganisms that have the potential to provide beneficial health effects to the host.1,2 Although there are thousands of commercially available probiotics, there is much debate as to what beneficial effects they might provide and which specific organisms may be most beneficial for particular uses.1-5 Microorganisms that are commonly used in probiotic preparations include the bacterial genera Lactobacillus, Bifidobacterium, Escherichia, Enterococcus, or Bacillus and the fungal genus Saccharomyces.2,5 Different probiotic species and strains can have substantially different effects on the host. Several species and strain-specific factors play a role in determining what, if any, effects a probiotic may have. To exert a beneficial effect, a probiotic must first be able to colonize the gastrointestinal (GI) tract. The initial step that is required for GI colonization by probiotics is adhesion to GI mucosa.6 Although not fully understood, current evidence suggests that the adhesive characteristics of probiotics may be due to differences in large surface proteins expressed and their interaction with mucus-binding proteins.6 However, this is not a characteristic that is shared among all probiotic species and strains.5,6 Probiotics that are able to colonize the GI tract effectively are then able to also resist colonization of potentially harmful bacteria, and they may have additional properties that make them beneficial to the host.5 For example, Lactobacillus can produce antimicrobial compounds, known as bacteriocins, which may inhibit a wide range of pathogens such as Bacillus, Staphylococcus, and Enterococcus species. Additionally, a specific strain of Lactobacillus acidophilus (La-14) produces a bacteriocin that has shown some inhibitory action against different variations of Listeria innocua and Listeria monocytogenes.3 Due to the variation in probiotic species and strains, the effectiveness of probiotics for preventing or treating different conditions can also vary substantially.3-5 With this in mind, it is important to recognize that there is no “generic equivalency” between probiotic species and strains. For example, one Lactobacillus acidophilus strain cannot be assumed to be equivalent to another Lactobacillus acidophilus strain in terms of its effectiveness in a human host. Therefore, it is important for clinicians to use or recommend specific commercially available probiotics, or a combination of probiotics, that have specifically been shown to have beneficial effects in clinical trials. Anecdotally, it has been noted that many practitioners consider probiotics in generic terms and may not recognize the important differences between different probiotic products. Similarly, many health care facilities stock a probiotic, but they will substitute one commercial probiotic for another based on cost or availability and without regard for the evidence that may or may not exist for the specific probiotics. To address this issue, a survey of academic medical centers in the United States was first conducted to determine which specific commercial probiotics were being stocked most commonly throughout the country. Using this survey data, a systematic literature review was conducted to determine whether those specific probiotics were supported by clinical research. This analysis will determine whether academic medical centers are currently using commercial probiotics that are specifically supported by a reliable evidence base.