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Probiotics for the Prevention of Clostridium difficile–Associated Diarrhea: A Systematic Review and Meta-analysis

Bradley C. Johnston, PhD; Stephanie S.Y. Ma, MD; Joshua Z. Goldenberg, BSc; Kristian Thorlund, PhD; Per O. Vandvik, MD, PhD; Mark Loeb, MD; and Gordon H. Guyatt, MD
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This article was published at www.annals.org on 13 November 2012.

From The Hospital for Sick Children Research Institute, Toronto, Ontario, Canada; Bastyr University, Kenmore, Washington; McMaster University, Hamilton, Ontario, Canada; and Innlandet Hospital Trust, Gjøvik, Norway.

Acknowledgment: The authors thank Jane Saxton for conducting the literature search.

Grant Support: Dr. Johnston was supported in part by a postdoctoral fellowship from the SickKids Foundation. Mr. Goldenberg is supported by grants BUCSR-Y2-005 and BUCSR-Y2-019 from the Bastyr Center for Student Research.

Potential Conflicts of Interest: Dr. Johnston: Grants/grants pending (money to institution): Biocodex. Mr. Goldenberg: Grant: Bastyr Center for Student Research; Support for travel to meetings for the study or other purposes: Bastyr Center for Student Research. Disclosures can also be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M12-1183.

Requests for Single Reprints: Bradley C. Johnston, PhD, The Hospital for Sick Children Research Institute, Room 2420, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada; e-mail, bradley.johnston@sickkids.ca.

Current Author Addresses: Dr. Johnston: The Hospital for Sick Children Research Institute, Room 2420, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada.

Dr. Ma: Division of Plastic and Reconstructive Surgery, McMaster University, Health Sciences Center 4E9, 1200 Main Street West, Hamilton, Ontario L8N 3Z5, Canada.

Mr. Goldenberg: Bastyr University, 14500 Juanita Drive NE, Kenmore, WA 98028-4966.

Drs. Thorlund and Guyatt: Department of Clinical Epidemiology and Biostatistics, McMaster University, Health Sciences Centre 3N48, 1200 Main Street West, Hamilton, Ontario L8N 3Z5, Canada.

Dr. Vandvik: Department of Medicine, Innlandet Hospital Trust–Division Gjøvik, Kyrre Greppsgt 13, 2819 Gjøvik, Norway.

Dr. Loeb: Division of Infectious Diseases, McMaster University, Michael G. DeGroote Center for Learning, Room 3200, 1200 Main Street West, Hamilton, Ontario L8S 4K1, Canada.

Author Contributions: Conception and design: B.C. Johnston, G.H. Guyatt.

Analysis and interpretation of the data: B.C. Johnston, S.S.Y. Ma, J.Z. Goldenberg, K. Thorlund, P.O. Vandvik, M. Loeb, G.H. Guyatt.

Drafting of the article: B.C. Johnston, S.S.Y. Ma, J.Z. Goldenberg.

Critical revision of the article for important intellectual content: B.C. Johnston, K. Thorlund, P.O. Vandvik, M. Loeb, G.H. Guyatt.

Final approval of the article: B.C. Johnston, S.S.Y. Ma, K. Thorlund, P.O. Vandvik, M. Loeb, G.H. Guyatt.

Provision of study materials or patients: B.C. Johnston.

Statistical expertise: B.C. Johnston, K. Thorlund, P.O. Vandvik.

Administrative, technical, or logistic support: B.C. Johnston.

Collection and assembly of data: B.C. Johnston, S.S.Y. Ma, J.Z. Goldenberg, P.O. Vandvik.

Ann Intern Med. 2012;157(12):878-888. doi:10.7326/0003-4819-157-12-201212180-00563
Text Size: A A A

Background: Antibiotic treatment may disturb the resistance of gastrointestinal flora to colonization. This may result in complications, the most serious of which is Clostridium difficile–associated diarrhea (CDAD).

Purpose: To assess the efficacy and safety of probiotics for the prevention of CDAD in adults and children receiving antibiotics.

Data Sources: Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, CINAHL, Allied and Complementary Medicine Database, Web of Science, and 12 gray-literature sources.

Study Selection: Randomized, controlled trials including adult or pediatric patients receiving antibiotics that compared any strain or dose of a specified probiotic with placebo or with no treatment control and reported the incidence of CDAD.

Data Extraction: Two reviewers independently screened potentially eligible articles; extracted data on populations, interventions, and outcomes; and assessed risk of bias. The Grading of Recommendations Assessment, Development and Evaluation guidelines were used to independently rate overall confidence in effect estimates for each outcome.

Data Synthesis: Twenty trials including 3818 participants met the eligibility criteria. Probiotics reduced the incidence of CDAD by 66% (pooled relative risk, 0.34 [95% CI, 0.24 to 0.49]; I2 = 0%). In a population with a 5% incidence of antibiotic-associated CDAD (median control group risk), probiotic prophylaxis would prevent 33 episodes (CI, 25 to 38 episodes) per 1000 persons. Of probiotic-treated patients, 9.3% experienced adverse events, compared with 12.6% of control patients (relative risk, 0.82 [CI, 0.65 to 1.05]; I2 = 17%).

Limitations: In 13 trials, data on CDAD were missing for 5% to 45% of patients. The results were robust to worst-plausible assumptions regarding event rates in studies with missing outcome data.

Conclusion: Moderate-quality evidence suggests that probiotic prophylaxis results in a large reduction in CDAD without an increase in clinically important adverse events.

Primary Funding Source: None.


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Figure 1.

Summary of evidence search and selection.

AMED = Allied and Complementary Medicine Database; CD = Clostridium difficile; CDAD = Clostridium difficile–associated diarrhea; CENTRAL = Cochrane Central Register of Controlled Trials; RCT = randomized, controlled trial.

* Sources were BIOSIS Previews, Canadian Agency for Drugs and Technology in Health, Dissertation Abstracts, Google Scholar, British Society of Gastroenterology Annual General Meeting, McGill University Technology Assessment Unit, Inflammatory Bowel Disease/Functional Bowel Disease register, the Turning Research Into Practice database, HighWire, clinical trial registries industry contact, and bibliographies.

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Appendix Figure.

Risk of bias of included trials.

* Miller and colleagues reported on 2 studies; the dosage of probiotic used was 3 times greater than in the study above.

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Figure 2.

Probiotics for the prevention of Clostridium difficile–associated diarrhea.

M–H = Mantel–Haenszel.

* Miller and colleagues reported on 2 studies; the dosage of probiotic used was 3 times greater than in the study above.

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Figure 3.

Risk for adverse effects with probiotics.

M–H = Mantel–Haenszel.

* Miller and colleagues reported on 2 studies; the dosage of probiotic used was 3 times greater than in the study above.

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Figure 4.

Effect of probiotics on prevention of Clostridium difficile–associated diarrhea among subgroups.

CFU = colony-forming units.

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Probiotics for the Prevention of Clostridium difficile-Associated Diarrhea
Posted on December 26, 2012
Steven Oscherwitz, MD, CIC
Infectious Disease. Phoenix, AZ.
Conflict of Interest: None Declared

           “Probiotics” are profitable for their sellers.  The risks of these products are not stressed by their manufacturers, and they are unregulated by the FDA.  Dr. Johnston and colleagues make no mention of antibiotic resistance issues associated, and do not mention cases in which probiotics have been linked to fungemia and bacterial sepsis.

Probiotic organisms can easily enter the bloodstream from the bowel in compromised patients.1  I have treated four cases of septic shock with Saccharomyces (from pills) and Lactobacillus (from Kefir) in recent months.  I suspect that such cases are under-reported.  The fact that immunosuppressed patients were excluded from more than half of the studies reviewed is not clear in the study summary or Conclusion, and casual readers may give such patients probiotics, not realizing the danger.

Additionally, probiotic Lactobacillus strains can acquire vancomycin resistance during digestive transit in mice,2  even in the absence of antibiotic pressure.  Acquisition and retransfer of resistance genes should be addressed in the safety evaluation of probiotics.

Having our patients continue to spend money on unregulated, ineffective and possibly harmful products is certainly undesirable.  The Bastyr Center supporting this study states on its website under FAQs that “Just because a supplement is natural does not guarantee that it is safe for everyone to take.” 3  (The Bastyr dispensaries certainly stand to benefit if everyone does take them, however).

It is not “natural” to have a colon full of a single or a few types of microbes.  Our colon flora is highly complex, and consists of a multiplicity of different species contributing to keep us healthy. Judicious use of fecal transplantation and avoidance of antibiotics would seem to be a safer strategy than taking unregulated pills.  Few probiotic trials have been adequately powered to show reduction in antibiotic associated diarrhea or C. difficile colitis.  The Mayo Clinic web site4 continues to list the unclear scientific evidence for use for probiotic supplements, showing Grade C ratings for all indications except vaginosis, which seems appropriate at this time.



                            Steven Oscherwitz MD, CIC

                             Infectious Disease         Phoenix, AZ




Recovery of Uncommon Bacteria from Blood: Association with Neoplastic Disease

CLINICAL MICROBIOLOGY REVIEWS, July 1995, p. 336–356 Vol. 8, No. 3


  1. Mater DD, Langella P, Corthier G, Flores MJ.

A probiotic Lactobacillus strain can acquire vancomycin resistance during digestive transit in mice.

J Mol Microbiol Biotechnol. 2008;14(1-3):123-7.


Unité d'Ecologie et de Physiologie du Système Digestif, Institut National de la Recherche Agronomique, Jouy-en-Josas, France.


      3.  http://www.bastyrcenter.org/content/category/7/120/114/


      4.  http://www.mayoclinic.com/health/lactobacillus/NS_patient-acidophilus








Revised comments on probiotics meta-analysis
Posted on January 2, 2013
David Louis Keller
Providence Medical Institute
Conflict of Interest: None Declared

As a primary-care physician, I recognize the need for evidence-based measures to reduce the likelihood of Clostridium Difficile-associated diarrhea [CDAD] in patients taking antibiotics. The review by Johnston and colleagues (1) presents a strong case for prophylaxis with probiotics, so I decided to select a probiotic to use in my practice from the list of those tested in trials which were included in the meta-analysis. The study by Gao and colleagues (2) had the heaviest weighting in the meta-analysis, at 23%. with the next heaviest weighted study at 16.1% and the rest of the studies weighted in single digits. The relative risk for CDAD was the second-lowest at 0.22, with the narrowest confidence interval of all the studies (0.11 - 0.46). Gao included patients taking penicillins, cephalosporins and clindamycin for various indications, which is applicable to my practice. Finally, the “proprietary blend” of probiotics studied by Gao (“Bio-K Plus”) is available for purchase on Amazon.com at a price of about $4.30 per day (3) for the most effective dose studied (2 capsules per day). However, I noticed that the study by Gao was funded entirely by the manufacturer of Bio-K Plus (4) and conducted at a hospital in mainland China. This raises the question of how much weight should be given to a study of a commercial product funded by the manufacturer and conducted in a country still working to overcome a history of Lysenkoism and other authoritarian distortions of the scientific method. If the meta-analysis is recalculated with Gao’s study deleted, do the results still favor the use of probiotics?

(1) Bradley C. Johnston, Stephanie S.Y. Ma, Joshua Z. Goldenberg, Kristian Thorlund, Per O. Vandvik, Mark Loeb, Gordon H. Guyatt; Probiotics for the Prevention of Clostridium difficile–Associated DiarrheaA Systematic Review and Meta-analysis. Annals of Internal Medicine. 2012 Dec;157(12):878-888.

(2) Gao XW, Mubasher M, Fang CY, Reifer C, Miller LE. Dose-response efficacy of a proprietary probiotic formula of Lactobacillus acidophilus CL1285 andLactobacillus casei LBC80R for antibiotic-associated diarrhea and Clostridiumdifficile-associated diarrhea prophylaxis in adult patients. Am J Gastroenterol. 2010 Jul;105(7):1636-41. doi: 10.1038/ajg.2010.11. Epub 2010 Feb 9. PubMed PMID: 20145608.

(3) Amazon.com website, accessed on 1/1/2013. ASIN: B005HJMGCE. UPC: 626608001500. Item model number: .BKPS-55US. URL: http://www.amazon.com/gp/product/B005HJMGCE/ref=olp_product_details?ie=UTF8&me=&seller=(4) ClinicalTrials.gov website, National Institutes of Health. Accessed on 1/1/2013. URL: http://www.clinicaltrials.gov/ct2/show/NCT00958308

Probiotic safety and risk of bias associated with industry-funded trials
Posted on March 8, 2013
Bradley C. Johnston, PhD, Joshua Z. Goldenberg, BSc, Gordon H.Guyatt,MD
Hospital for Sick Children
Conflict of Interest: None Declared

Authors’ Response: Bradley C. Johnston; Joshua Z. Goldenberg; Gordon H. Guyatt


Title: Probiotic safety and risk of bias associated with industry-funded trials

Dr. Keller notes that the trial by Gao and colleagues was industry funded, conducted in China and as a result potentially at risk of bias [1].  Post-hoc we removed the study by Gao and colleagues and the pooled estimate remained highly significant (RR 0.39; 95% CI 0.26 to 0.59).  We included 20 randomized trials and after further removing the 11 industry funded trials from our pooled analysis the results remain robust, demonstrating a large risk reduction in favor of probiotics (RR 0.29; 95% CI 0.15 to 0.53).

Turning to Dr. Oscherwitz's concerns, our findings that probiotics did not increase the risk of adverse events has been corroborated by a systematic review of the safety of probiotics that included both randomized and non-randomized studies (387 studies including 24,615 total participants) [2].

The case reports in the literature of fungemia and bacterial sepsis associated with probiotics predominately involve preterm neonates, severely debilitated or immuno-compromised patients [2]. We therefore stated that our results indicate “…short-term probiotic use in persons who are not immunodeficient or severely debilitated does not result in important side effects[3]. 

Although there has been evidence of antibiotic resistance occurring with bacterial-based probiotics, including the transfer of this resistance to the local gut micobiome [4], we are unaware of any documented, and important, clinical consequences associated with this possibility.   The risks associated with bacterial resistance appear to not be an issue with yeast-based probiotics.  If probiotics are incorporated into clinical practice, an active surveillance system to gather data about potential adverse events would provide further risk estimates.

Studies in animal models, children and adults demonstrate that probiotics temporarily colonize the intestines for 3 to 7 days [5, 6]. If probiotic agents were to become established in the gut, there is potential for reducing the complexity of the intestinal microbiota, which may displace some beneficial organisms.  We are, however, not aware of any evidence suggesting this phenomenon occurs.

We agree with Dr. Oscherwitz’s suggestion that few probiotic trials have been adequately powered. This is why we conducted a systematic review and meta-analysis.

In summary, evidence was consistent across subgroup analyses (see Figure 4) and sensitivity analyses regarding missing participant data, warranting moderate confidence in a large relative risk reduction (66%) in C. difficile associated diarrhea in patients receiving antibiotics [3].  If restricted to non-immunocompromised individuals, the risk of important adverse events, if it exists at all, is very small.

Word count: 397 (maximum 400)


Bradley C. Johnston

Joshua Z. Goldenberg

Gordon H. Guyatt


1.            1. Gao XW, Mubasher M, Fang CY, Reifer C, Miller LE. Dose-response efficacy of a proprietary probiotic formula of Lactobacillus acidophilus CL1285 and Lactobacillus casei LBC80R for antibiotic-associated diarrhea and Clostridium difficile-associated diarrhea prophylaxis in adult patients. Am J Gastroenterol, 2010. 105(7): p. 1636-41.

2.            2. Hempel S, Newberry S, Ruelaz A, Wang Z, Miles JN, Suttorp MJ, Johnsen B, Shanman R, Slusser W, Fu N, Smith A, Roth B, Polak J, Motala A, Perry T, Shekelle PG. Safety of probiotics used to reduce risk and prevent or treat disease. Evid Rep Technol Assess (Full Rep), 2011(200): p. 1-645.

3.            3. Johnston BC, Ma SSY, Goldenberg JZ, Thorlund K, Vandvik P, Loeb M, Guyatt GH. Probiotics for the prevention of Clostridium difficile-associated diarrhea: a systematic review and meta-analysis. Ann Intern Med, 2012. 157(12): p. 878-88.


4.            4. Rosander A, Connolly E, Roos S. Removal of antibiotic resistance gene-carrying plasmids from Lactobacillus reuteri ATCC 55730 and characterization of the resulting daughter strain, L. reuteri DSM 17938. Appl Environ Microbiol. 2008;Oct;74(19):6032-40.


5.           5. Blehaut H, Massot J, Elmer GW, Levy RH. Disposition kinetics of Saccharomyces bououlardii in man and rat. Biopharm Drug Dispos. 1989 Jul-Aug;10(4):353-64.


6.          6. Marini A, Clerici-Bagozzi D, Maglia T, Casetta P, Negretti F. Microbiological and immunological observations in the stools of preterm neonates orally treated with probiotic products. Note III: treatment with Lactobacillus GG. Dev Physiopathy Clin 1997; 7:87-94.



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