Wageningen Academic P u b l i s h e r s
Beneficial Microbes, 2015; 6(6): 823-828
http://www.wageningenacademic.com/doi/pdf/10.3920/BM2015.0065 - Thursday, September 21, 2017 11:17:30 AM - Göteborgs Universitet IP Address:130.241.16.16
Immunosuppression and probiotics: are they effective and safe? V. Stadlbauer Medical University of Graz, Department of Gastroenterology and Hematology, Auenbruggerplatz, 8010 Graz, Austria; [email protected] Received: 18 May 2015 / Accepted: 27 June 2015 © 2015 Wageningen Academic Publishers
REVIEW ARTICLE Abstract This opinion statement discusses indications, efficacy and safety of probiotics in immunosuppressed patients. The best evidence available is for the prophylaxis of infections in patients after liver transplantation and for patients with liver cirrhosis. For other organ transplantations and for bone marrow transplantation the efficacy of probiotic interventions has not been proven yet, but in these patient groups safety is a concern. Also in critically ill patients, the data on efficacy are inconclusive and safety is a concern. In HIV patients and patients after major surgery, probiotic bacteria seem to be safe since there are no associations with increased risks of side effects. Keywords: immunosuppression, probiotic, medical use
1. Introduction This opinion statement aims to give an overview of the current literature on indications and safety of probiotics in patients after organ transplantation and with other immunocompromised conditions. Probiotics are defined as ‘live micro-organisms which, when administered in adequate amounts, confer a health benefit on the host’ by the WHO (FAO/WHO, 2001; Hill et al., 2014). Prebiotics are non-digestible fibres that induce growth and/or activity of probiotic bacteria (Gibson and Roberfroid, 1995), while synbiotics refer to a mixture of probiotics and prebiotics (Schrezenmeir and de Vrese, 2001). In the last few years, mainly due to the development of highly efficient sequencing and analysis techniques, the interest, number, and quality of publications on the gut microbiome and probiotic therapy has increased. Probiotics are currently in routine use for prophylaxis and therapy of different diseases – such as antibiotic-associated diarrhoea, infectious childhood diarrhoea, ulcerative colitis, pouchitis or atopic eczema associated with cow’s milk allergy (Floch, 2014). For other diseases, such as metabolic syndrome, type 2 diabetes mellitus, prophylaxis of infections, or allergies, probiotics have been studied in patients but these data are not yet sufficient for routine use
(Iqbal et al., 2014). Furthermore, it is important to keep in mind that each strain exerts specific effects. Stig Bengmark, a pioneer in probiotic research, stated that the genetic difference between one probiotic bacterium and the other is larger than the difference between a man and a goldfish.(Rijkers et al., 2011). Some mechanisms are widespread among probiotic genera, others can be frequently found among most strains of a probiotic species, while some may be rare and are only be observed in a few strains of a given species (Hill et al., 2014). The success or failure of one strain cannot be extrapolated to other strains. As an example, Enterococcus faecium can be a commensal, a pathogen that can cause severe problem due to resistance to antibiotics, or – in the case of strain W54 – a valuable probiotic that inhibits Clostridium difficile toxin (Steyer and Pfeifer, 2012). Furthermore, it has been discussed whether multispecies probiotics are more effective than single species preparations. Current literature suggests that multispecies preparations are more effective due to better survival of the gastro-duodenal passage or greater ability to find a biological niche (Chapman et al., 2011; Hell et al., 2013). However, an important question still remaining is whether the effects of multispecies preparations are additive or synergistic.
ISSN 1876-2833 print, ISSN 1876-2891 online, DOI 10.3920/BM2015.0065823
http://www.wageningenacademic.com/doi/pdf/10.3920/BM2015.0065 - Thursday, September 21, 2017 11:17:30 AM - Göteborgs Universitet IP Address:130.241.16.16
V. Stadlbauer
Generally, probiotics are considered as safe, since many strains have a long tradition in food processing. However, there are also reports of severe side effects, such as infections or even sepsis due to probiotic use (Van den Nieuwboer et al., 2015). Therefore, the question arises whether probiotics are safe in patients with immunosuppressive therapy or with an immunocompromising disease. In a meta-analysis of 57 studies in adults with immunosuppression (HIV, organ transplantation, malignant diseases, critical illness, diseases with immunocompromising effects, and patients with diseases treated with immunosuppressive drugs, such as rheumatoid arthritis, inflammatory bowel disease) the incidence of adverse events according to the Common Terminology Criteria for Adverse Events (CTCAE) was studied. In this meta-analysis, the risk for the development of side effects was not found to be increased by probiotic treatment. However, 22% of the studies did not report side effects at all (Van den Nieuwboer et al., 2015).
2. Solid organ transplantation Preventing postoperative infections is the main indication for probiotics after solid organ transplantation. This is based on the hypothesis that the operation itself can lead
Dybiosis
Pathobiont expansion
Reduced diversity
to a massive proinflammatory stimulus that increases gut permeability. Increased gut permeability together with dysbiosis may lead to increased translocation of bacterial products across the gut barrier into the circulation. Bacterial translocation is an important pathogenic factor for the observed increased risk of infections after liver transplantation. Probiotics may be able to improve gut permeability, restore eubiosis and/or impact directly on immune function (Figure 1) (Rayes et al., 2002b). This problem is most evident in liver transplantation since, besides any trauma resulting from the operation, the underlying liver disease can also lead to increased gut permeability and increased bacterial translocation after transplantation (Leber et al., 2012; Xie et al., 2011). Randomised, double blind, placebo-controlled studies conducted at the Charité in Berlin, Germany have shown that a probiotic or synbiotic compared to placebo or enteral nutrition can drastically reduce the rate of infections after liver transplantation, from 48% to an incredibly low 3% (Rayes et al., 2002a,b, 2005). Interestingly, the strongest effect of probiotics to prevent infections after liver transplantation has been seen for urinary tract infections. The authors interpret this as a proof for their hypothesis
Eubiosis
Probiotics
1
Level microbiota
2
Level intestinal barrier
3
Level immune function
Loss of beneficial microbes
Impaired barrier
Normal barrier
Normal tight junction
Leaky and inflamed
Immune activation and inflammation Macrophage
Cytokines
T cells
Dendritic cells
Figure 1. Hypothesis on the pathogenesis of infections due to increased gut permeability and dysbiosis. Dysbiosis and increased permeability lead to increased bacterial translocation into the circulation. This results in inadequate activation of the innate immune system and an increased risk of infections. Probiotics can decrease gut permeability, restore eubiosis, and prevent translocation of bacterial products. 824
Beneficial Microbes 6(6)
http://www.wageningenacademic.com/doi/pdf/10.3920/BM2015.0065 - Thursday, September 21, 2017 11:17:30 AM - Göteborgs Universitet IP Address:130.241.16.16
Immunsuppression and probiotics
that probiotics exert their effects not only locally in the gut but are also able to improve the function of the innate and adaptive immune system via different yet not completely elucidated mechanisms. In the three studies from Charité, different probiotic preparations were used: the first two studies tested Lactobacillus plantarum 299, whereas the 2005 study used a synbiotic formulation (Synbiotic 2000) consisting of four lactic acid producing strains Pedicoccus pentasacceus, Leoconostoc mesenteroides, Lactobacillus paracasei subsp. paracasei and L. plantarum in addition to beta-glucan, inulin, pectin and resistant starch as prebiotic components. Results from a trial from Japan in living donor liver transplantation recipients have confirmed these results. In this trial, the rate of postoperative infections was shown to be reduced from 24% to 4% by a synbiotic formulation (Bifidobacterium breve, Lactobacillus casei, and galactooligosaccharide) (Eguchi et al., 2011).
could positively influence GVHD and in fact this has been already confirmed in an animal model (Gerbitz et al., 2004). This hypothesis is further reinforced by the fact that children who consume more yoghurt or other foods containing pro- or prebiotics after stem cell transplantation, have fewer complications after transplantation (Tavil et al., 2012). To date however, no human intervention studies with pre- or probiotics have been published (Van der Meij et al., 2013). Similar to thoracic organ transplantation patients, safety of probiotics is a concern in GVHD. The literature cites one case of sepsis with Lactobacillus acidophilus after autologous stem cell transplantation, however, it should be noted that the patient consumed 6-8 portions daily of a commercially available probiotic yoghurt (Mehta et al., 2013).
A possible further mechanism of action can be found from L. casei DN-114001 supplementation in children after liver transplantation which was shown to decrease the activity of enzymes associated with mucosal damage (Pawlowska et al., 2007). This confirms the animal experiments that showed a protective effect of probiotics on gut permeability and gut microbiome composition after liver transplantation, especially in malnourished animals (Ren et al., 2011). Further animal experiments have shown that probiotics could also protect the liver from damage during an episode of acute rejection; this may be explained by an increase of regulatory T cells and tumour-growth factor beta (Xie et al., 2014).
Patients with HIV infection
Little information is available on the efficacy and safety of probiotic in patients after thoracic organ transplantation. One available report concerns an HIV positive patient after lung transplantation, who developed a pleura empyema with positive cultures for Lactobacillus rhamnosus after having received L. rhamnosus GG as a prophylactic treatment for C. difficile-associated diarrhoea. After this incident, researchers from the University of Pittsburgh reviewed 814 cases of heart and/or lung transplantation who were treated with L. rhamnosus, and found that in eight cases, further infections were caused by lactobacilli. Subsequently, this centre stopped the use of probiotics in patients after thoracic organ transplantation (Luong et al., 2010). At the moment, no human data on probiotics in patients after renal or pancreas transplantation are available.
3. Bone marrow/stem cell transplantation Graft-versus-host-disease (GVHD) can hamper the success of bone marrow or stem cell transplantation. One mechanism of GVHD is the translocation of lipopolysaccharides from the gut. It has been hypothesised that the modulation of the gut microbiome by probiotics Beneficial Microbes 6(6)
4. Other forms of immunosuppression
In HIV, the gut suffers from a reduction of CD4-positive T cells and dendritic cells. This leads to an inflammatory reaction, dysbiosis, increased permeability, and increased translocation of bacterial products (Marchetti et al., 2013). Since probiotics can decrease gut permeability and intestinal inflammation, interventional studies in HIV have been performed (Hummelen et al., 2010). For instance, administration of L. rhamnosus GR-1 has led to an increase in CD4 positive T cells and a decrease in febrile episodes, however, the effect was weaker than anticipated. As reviewed by Van den Nieuwboer et al. (2015), the safety profile of the probiotic intervention in HIV is good, as no side effects have been noted even with high doses. However, the number of studies and the number of tested strains in this setting is limited.
Critically ill patients Critically ill patients are exceptionally prone to infections (e.g. ventilator associated pneumonia) due to the massive inflammatory reaction, the need for parenteral nutrition, and mechanical ventilation. The short-term use of probiotics or synbiotics in some studies has resulted in an improvement of infection rates, complication rates, and different surrogate parameters of gut permeability and immune function. In one study, a decrease in mortality was also found. However, there are also several negative studies that do not show any beneficial effect of probiotic treatment (Jacobi et al., 2011; Madsen, 2008). Furthermore, major safety concerns in the critically ill have arisen from a study in severe acute pancreatitis patients that showed higher mortality due to an increased rate of small bowel ischemia (Besselink et al., 2008).
825
V. Stadlbauer
http://www.wageningenacademic.com/doi/pdf/10.3920/BM2015.0065 - Thursday, September 21, 2017 11:17:30 AM - Göteborgs Universitet IP Address:130.241.16.16
Major surgery During major surgery, the surgical trauma causes a systemic inflammatory reaction that leads to translocation of bacterial products via increased gut permeability and thereby increases the risk of postoperative infections (Figure 1). Several studies with different probiotic strains have been conducted, some with very good results and some showing no effect. Possible explanations for this are the use of different probiotic strains or the heterogeneity of patients after major surgery, where several factors, which cannot be controlled in studies, play a role: postoperative nutrition, operation technique, and differences in health care structure (Bengmark, 2012). Most studies do not report any severe side effects, however, once again, the amount of studies and the number of tested strains are limited. One exception seems to be Saccharomyces boulardii. At least 30 cases of fungemia after the use of S. boulardii have been described. Some patients had major surgery; most of them were also critically ill and had foreign bodies such as central venous catheters or artificial joints that increase the risk of infections (Didari et al., 2014). S. bourlardii is not normally found in the human gut microbiome, therefore it follows that this yeast can cross the gut barrier more easily, especially in immunocompromised subjects.
Liver cirrhosis The incidence of liver cirrhosis is increasing. In the Western world, liver cirrhosis is already the 10th most common cause of death. In liver cirrhosis, dysbiosis and increased gut permeability contribute to the development of further complications, such as hepatic encephalopathy and infections, due to the increased translocation of bacterial products. Since the gut microbiome plays a key role in this hypothesis, strategies to modulate the gut microbiome are of great interest. Probiotics can exert direct (stimulation of tight junctions and modulation of mucin production) or indirect (microbiome composition and immunomodulation) effects on the gut-liver axis. In liver cirrhosis, probiotics have been used to improve liver function, to prevent or treat hepatic encephalopathy, and to prevent infections. Studies aimed at improvement of liver function have shown promising results, however large studies are lacking (Lo et al., 2014). Probiotics have also been used successfully to treat or prevent hepatic encephalopathy (Iwasa and Takei, in press; McGee et al., 2011), however due to small sample sizes and different study designs no recommendations have been made so far in international guidelines.
826
The increased risk of infections in liver cirrhosis is a major problem which leads to high mortality rates. Probiotics may have a positive effect on neutrophil phagocytic capacity, but this has to be proven in larger studies (Stadlbauer et al., 2008). So far no severe side effects of probiotic therapy in liver cirrhosis have been published, which is also in accordance with the personal experience of the author. Therefore, the probiotic strains that have been currently tested and published in literature seem to be safe in this patient group despite impaired innate immunity.
5. Summary and practical considerations The use of probiotics in immunocompromised adults has to be considered carefully. It should be emphasised once more that it is not possible to extrapolate safety information of one or more probiotic strains to all available probiotic strains. Safety as well as efficacy must be evaluated separately for each strain or combination of strains. From the current available literature, probiotic treatment of patients after liver transplantation and patients with liver cirrhosis has not resulted in any safety concerns. Specific strains have been shown to be effective in preventing infections after liver transplantation and for therapy or prevention of hepatic encephalopathy. So far in HIV patients no safety concerns have emerged, but the data are limited. It is difficult to declare safety of probiotics after major surgery, since the data are limited and there is at least some concern using organisms not physiologically present in the human intestine. In critically ill patients, after heart, lung, or bone marrow/stem cell transplantation, while there is insufficient evidence for efficacy, safety is a major concern. Therefore, the risks and benefits have to be considered very carefully. Ideally the safety and efficacy of probiotics should be studied in clinical trials. In conclusion, the use of probiotics in immunocompromised adults is possible. However, sufficient information on the strains used (such as sensibility to antibiotics) is mandatory and in case of unexpected infections, the probiotic strains should be considered as a cause. Furthermore, studies with probiotics need to include more safety aspects such as surveillance cultures of body fluids.
Acknowledgements Winclove Probiotics provided the graphic design for Figure 1. Jessica Younes edited the manuscript.
References Bengmark, S., 2012. Pro- and synbiotics to prevent sepsis in major surgery and severe emergencies. Nutrients 4: 91-111.
Beneficial Microbes 6(6)
http://www.wageningenacademic.com/doi/pdf/10.3920/BM2015.0065 - Thursday, September 21, 2017 11:17:30 AM - Göteborgs Universitet IP Address:130.241.16.16
Immunsuppression and probiotics
Besselink, M.G., Van Santvoort, H.C., Buskens, E., Boermeester, M.A., van Goor, H., Timmerman, H.M., Nieuwenhuijs, V.B., Bollen, T.L., Van Ramshorst, B., Witteman, B.J., Rosman, C., Ploeg, R.J., Brink, M.A., Schaapherder, A.F., Dejong, C.H., Wahab, P.J., Van Laarhoven, C.J., Van der Harst, E., Van Eijck, C.H., Cuesta, M.A., Akkermans, L.M., Gooszen, H.G. and Dutch Acute Pancreatitis Study, G., 2008. Probiotic prophylaxis in predicted severe acute pancreatitis: a randomised, double-blind, placebo-controlled trial. The Lancet 371: 651-659. Chapman, C.M., Gibson, G.R. and Rowland, I., 2011. Health benefits of probiotics: are mixtures more effective than single strains? European Journal of Nutrition 50: 1-17. Didari, T., Solki, S., Mozaffari, S., Nikfar, S. and Abdollahi, M., 2014. A systematic review of the safety of probiotics. Expert Opinion on Drug Safety 13: 227-239. Eguchi, S., Takatsuki, M., Hidaka, M., Soyama, A., Ichikawa, T. and Kanematsu, T., 2011. Perioperative synbiotic treatment to prevent infectious complications in patients after elective living donor liver
Leber, B., Spindelboeck, W. and Stadlbauer, V., 2012. Infectious complications of acute and chronic liver disease. Seminars in Respiratory and Critical Care Medicine 33: 80-95. Lo, R.S., Austin, A.S. and Freeman, J.G., 2014. Is there a role for probiotics in liver disease? Scientific World Journal 2014: 874768. Luong, M.L., Sareyyupoglu, B., Nguyen, M.H., Silveira, F.P., Shields, R.K., Potoski, B.A., Pasculle, W.A., Clancy, C.J. and Toyoda, Y., 2010. Lactobacillus probiotic use in cardiothoracic transplant recipients: a link to invasive Lactobacillus infection? Transplant Infectious Disease 12: 561-564. Madsen, K., 2008. Probiotics in critically ill patients. Journal of Clinical Gastroenterology 42 Suppl. 3 Part 1: S116-S118. Marchetti, G., Tincati, C. and Silvestri, G., 2013. Microbial translocation in the pathogenesis of HIV infection and AIDS. Clinical Microbiology Reviews 26: 2-18. McGee, R.G., Bakens, A., Wiley, K., Riordan, S.M. and Webster, A.C., 2011. Probiotics for patients with hepatic encephalopathy. Cochrane Database of Systematic Reviews: CD008716.
transplantation: a prospective randomized study. American Journal of Surgery 201: 498-502. Food and Agriculture Organization of the United Nations/World Health Organization (FAO/WHO), 2001. Evaluation of health and nutritional properties of powder milk and live lactic acid bacteria. Available at: http://tinyurl.com/8bccc3r. Floch, M.H., 2014. Recommendations for probiotic use in humans – a 2014 update. Pharmaceuticals 7: 999-1007. Gerbitz, A., Schultz, M., Wilke, A., Linde, H.J., Scholmerich, J., Andreesen, R. and Holler, E., 2004. Probiotic effects on experimental graft-versus-host disease: let them eat yogurt. Blood 103: 4365-4367. Gibson, G.R. and Roberfroid, M.B., 1995. Dietary modulation of the human colonic microbiota: introducing the concept of prebiotics. Journal of Nutrition 125: 1401-1412. Hell, M., Bernhofer, C., Stalzer, P., Kern, J.M. and Claassen, E., 2013. Probiotics in Clostridium difficile infection: reviewing the need for a multistrain probiotic. Beneficial Microbes 4: 39-51. Hill, C., Guarner, F., Reid, G., Gibson, G.R., Merenstein, D.J., Pot, B., Morelli, L., Canani, R.B., Flint, H.J., Salminen, S., Calder, P.C. and Sanders, M.E., 2014. Expert consensus document. The International Scientific Association for Probiotics and Prebiotics consensus
Mehta, A., Rangarajan, S. and Borate, U., 2013. A cautionary tale for probiotic use in hematopoietic SCT patients – Lactobacillus acidophilus sepsis in a patient with mantle cell lymphoma undergoing hematopoietic SCT. Bone Marrow Transplantation 48: 461-462. Pawlowska, J., Klewicka, E., Czubkowski, P., Motyl, I., Jankowska, I., Libudzisz, Z., Teisseyre, M., Gliwicz, D. and Cukrowska, B., 2007. Effect of Lactobacillus casei DN-114001 application on the activity of fecal enzymes in children after liver transplantation. Transplantation Proceedings 39: 3219-3221. Rayes, N., Seehofer, D., Hansen, S., Boucsein, K., Muller, A.R., Serke, S., Bengmark, S. and Neuhaus, P., 2002a. Early enteral supply of Lactobacillus and fiber versus selective bowel decontamination: a controlled trial in liver transplant recipients. Transplantation 74: 123-127. Rayes, N., Seehofer, D., Muller, A.R., Hansen, S., Bengmark, S. and Neuhaus, P., 2002b. [Influence of probiotics and fibre on the incidence of bacterial infections following major abdominal surgery – results of a prospective trial]. Zeitschrift fuer Gastroenterologie 40: 869-876 [in German]. Rayes, N., Seehofer, D., Theruvath, T., Schiller, R.A., Langrehr,
statement on the scope and appropriate use of the term probiotic. Nature Reviews Gastroenterology and Hepatology 11: 506-514. Hummelen, R., Vos, A.P., Van’t Land, B., Van Norren, K. and Reid, G., 2010. Altered host-microbe interaction in HIV: a target for intervention with pro- and prebiotics. International Reviews of Immunology 29: 485-513. Iqbal, M.Z., Qadir, M.I., Hussain, T., Janbaz, K.H., Khan, Y.H. and Ahmad, B., 2014. Review: probiotics and their beneficial effects against various diseases. Pakistan Journal of Pharmaceutical Sciences 27: 405-415. Iwasa, M. and Takei, Y., in press. Pathophysiology and management of hepatic encephalopathy 2014 update: ammonia toxicity and hyponatremia. Hepatology Research. DOI: http://dx.doi. org/10.1111/hepr.12495. Jacobi, C.A., Schulz, C. and Malfertheiner, P., 2011. Treating critically ill patients with probiotics: Bbeneficial or dangerous? Gut Pathogens 3: 2.
J.M., Jonas, S., Bengmark, S. and Neuhaus, P., 2005. Supply of pre- and probiotics reduces bacterial infection rates after liver transplantation – a randomized, double-blind trial. American Journal of Transplantation 5: 125-130. Ren, Z.G., Liu, H., Jiang, J.W., Jiang, L., Chen, H., Xie, H.Y., Zhou, L. and Zheng, S.S., 2011. Protective effect of probiotics on intestinal barrier function in malnourished rats after liver transplantation. Hepatobiliary and Pancreatic Diseases International 10: 489-496. Rijkers, G.T., De Vos, W.M., Brummer, R.J., Morelli, L., Corthier, G. and Marteau, P., 2011. Health benefits and health claims of probiotics: bridging science and marketing. British Journal of Nutrition 106: 1291-1296. Schrezenmeir, J. and De Vrese, M., 2001. Probiotics, prebiotics, and synbiotics – approaching a definition. American Journal of Clinical Nutrition 73: 361S-364S.
Beneficial Microbes 6(6)
827
http://www.wageningenacademic.com/doi/pdf/10.3920/BM2015.0065 - Thursday, September 21, 2017 11:17:30 AM - Göteborgs Universitet IP Address:130.241.16.16
V. Stadlbauer
Stadlbauer, V., Mookerjee, R.P., Hodges, S., Wright, G.A., Davies, N.A. and Jalan, R., 2008. Effect of probiotic treatment on deranged neutrophil function and cytokine responses in patients with compensated alcoholic cirrhosis. Journal of Hepatology 48: 945-951. Steyer, G.E. and Pfeifer, J., 2012. Multispezies Probiotika und Antibiotika. Review zur klinischen Evidenz bei der Prävention Antibiotika-Assoziierter Diarrhoe (AAD) und Clostridium difficileInfektionen (CDI). OM & Ernährung 141: 38-41 [in German]. Tavil, B., Koksal, E., Yalcin, S.S. and Uckan, D., 2012. Pretransplant nutritional habits and clinical outcome in children undergoing hematopoietic stem cell transplant. Experimental and Clinical Transplantation 10: 55-61. Van den Nieuwboer, M., Brummer, R.J., Guarner, F., Morelli, L., Cabana, M. and Claasen, E., 2015. The administration of probiotics and synbiotics in immune compromised adults: is it safe? Beneficial Microbes 6: 3-17.
828
Van der Meij, B.S., De Graaf, P., Wierdsma, N.J., Langius, J.A., Janssen, J.J., Van Leeuwen, P.A. and Visser, O.J., 2013. Nutritional support in patients with GVHD of the digestive tract: state of the art. Bone Marrow Transplantation 48: 474-482. Xie, Y., Chen, H., Zhu, B., Qin, N., Chen, Y., Li, Z., Deng, M., Jiang, H., Xu, X., Yang, J., Ruan, B. and Li, L., 2014. Effect of intestinal microbiota alteration on hepatic damage in rats with acute rejection after liver transplantation. Microbial Ecology 68: 871-880. Xie, Y.R., Liu, S.L., Liu, X., Luo, Z.B., Zhu, B., Li, Z.F., Li, L.J., He, Y., Jiang, L., Li, H. and Ruan, B., 2011. Intestinal microbiota and innate immunity-related gene alteration in cirrhotic rats with liver transplantation. Transplantation Proceedings 43: 3973-3979.
Beneficial Microbes 6(6)
Beneficial Microbes, 2015; 6(6): 823-828
http://www.wageningenacademic.com/doi/pdf/10.3920/BM2015.0065 - Thursday, September 21, 2017 11:17:30 AM - Göteborgs Universitet IP Address:130.241.16.16
Immunosuppression and probiotics: are they effective and safe? V. Stadlbauer Medical University of Graz, Department of Gastroenterology and Hematology, Auenbruggerplatz, 8010 Graz, Austria; [email protected] Received: 18 May 2015 / Accepted: 27 June 2015 © 2015 Wageningen Academic Publishers
REVIEW ARTICLE Abstract This opinion statement discusses indications, efficacy and safety of probiotics in immunosuppressed patients. The best evidence available is for the prophylaxis of infections in patients after liver transplantation and for patients with liver cirrhosis. For other organ transplantations and for bone marrow transplantation the efficacy of probiotic interventions has not been proven yet, but in these patient groups safety is a concern. Also in critically ill patients, the data on efficacy are inconclusive and safety is a concern. In HIV patients and patients after major surgery, probiotic bacteria seem to be safe since there are no associations with increased risks of side effects. Keywords: immunosuppression, probiotic, medical use
1. Introduction This opinion statement aims to give an overview of the current literature on indications and safety of probiotics in patients after organ transplantation and with other immunocompromised conditions. Probiotics are defined as ‘live micro-organisms which, when administered in adequate amounts, confer a health benefit on the host’ by the WHO (FAO/WHO, 2001; Hill et al., 2014). Prebiotics are non-digestible fibres that induce growth and/or activity of probiotic bacteria (Gibson and Roberfroid, 1995), while synbiotics refer to a mixture of probiotics and prebiotics (Schrezenmeir and de Vrese, 2001). In the last few years, mainly due to the development of highly efficient sequencing and analysis techniques, the interest, number, and quality of publications on the gut microbiome and probiotic therapy has increased. Probiotics are currently in routine use for prophylaxis and therapy of different diseases – such as antibiotic-associated diarrhoea, infectious childhood diarrhoea, ulcerative colitis, pouchitis or atopic eczema associated with cow’s milk allergy (Floch, 2014). For other diseases, such as metabolic syndrome, type 2 diabetes mellitus, prophylaxis of infections, or allergies, probiotics have been studied in patients but these data are not yet sufficient for routine use
(Iqbal et al., 2014). Furthermore, it is important to keep in mind that each strain exerts specific effects. Stig Bengmark, a pioneer in probiotic research, stated that the genetic difference between one probiotic bacterium and the other is larger than the difference between a man and a goldfish.(Rijkers et al., 2011). Some mechanisms are widespread among probiotic genera, others can be frequently found among most strains of a probiotic species, while some may be rare and are only be observed in a few strains of a given species (Hill et al., 2014). The success or failure of one strain cannot be extrapolated to other strains. As an example, Enterococcus faecium can be a commensal, a pathogen that can cause severe problem due to resistance to antibiotics, or – in the case of strain W54 – a valuable probiotic that inhibits Clostridium difficile toxin (Steyer and Pfeifer, 2012). Furthermore, it has been discussed whether multispecies probiotics are more effective than single species preparations. Current literature suggests that multispecies preparations are more effective due to better survival of the gastro-duodenal passage or greater ability to find a biological niche (Chapman et al., 2011; Hell et al., 2013). However, an important question still remaining is whether the effects of multispecies preparations are additive or synergistic.
ISSN 1876-2833 print, ISSN 1876-2891 online, DOI 10.3920/BM2015.0065823
http://www.wageningenacademic.com/doi/pdf/10.3920/BM2015.0065 - Thursday, September 21, 2017 11:17:30 AM - Göteborgs Universitet IP Address:130.241.16.16
V. Stadlbauer
Generally, probiotics are considered as safe, since many strains have a long tradition in food processing. However, there are also reports of severe side effects, such as infections or even sepsis due to probiotic use (Van den Nieuwboer et al., 2015). Therefore, the question arises whether probiotics are safe in patients with immunosuppressive therapy or with an immunocompromising disease. In a meta-analysis of 57 studies in adults with immunosuppression (HIV, organ transplantation, malignant diseases, critical illness, diseases with immunocompromising effects, and patients with diseases treated with immunosuppressive drugs, such as rheumatoid arthritis, inflammatory bowel disease) the incidence of adverse events according to the Common Terminology Criteria for Adverse Events (CTCAE) was studied. In this meta-analysis, the risk for the development of side effects was not found to be increased by probiotic treatment. However, 22% of the studies did not report side effects at all (Van den Nieuwboer et al., 2015).
2. Solid organ transplantation Preventing postoperative infections is the main indication for probiotics after solid organ transplantation. This is based on the hypothesis that the operation itself can lead
Dybiosis
Pathobiont expansion
Reduced diversity
to a massive proinflammatory stimulus that increases gut permeability. Increased gut permeability together with dysbiosis may lead to increased translocation of bacterial products across the gut barrier into the circulation. Bacterial translocation is an important pathogenic factor for the observed increased risk of infections after liver transplantation. Probiotics may be able to improve gut permeability, restore eubiosis and/or impact directly on immune function (Figure 1) (Rayes et al., 2002b). This problem is most evident in liver transplantation since, besides any trauma resulting from the operation, the underlying liver disease can also lead to increased gut permeability and increased bacterial translocation after transplantation (Leber et al., 2012; Xie et al., 2011). Randomised, double blind, placebo-controlled studies conducted at the Charité in Berlin, Germany have shown that a probiotic or synbiotic compared to placebo or enteral nutrition can drastically reduce the rate of infections after liver transplantation, from 48% to an incredibly low 3% (Rayes et al., 2002a,b, 2005). Interestingly, the strongest effect of probiotics to prevent infections after liver transplantation has been seen for urinary tract infections. The authors interpret this as a proof for their hypothesis
Eubiosis
Probiotics
1
Level microbiota
2
Level intestinal barrier
3
Level immune function
Loss of beneficial microbes
Impaired barrier
Normal barrier
Normal tight junction
Leaky and inflamed
Immune activation and inflammation Macrophage
Cytokines
T cells
Dendritic cells
Figure 1. Hypothesis on the pathogenesis of infections due to increased gut permeability and dysbiosis. Dysbiosis and increased permeability lead to increased bacterial translocation into the circulation. This results in inadequate activation of the innate immune system and an increased risk of infections. Probiotics can decrease gut permeability, restore eubiosis, and prevent translocation of bacterial products. 824
Beneficial Microbes 6(6)
http://www.wageningenacademic.com/doi/pdf/10.3920/BM2015.0065 - Thursday, September 21, 2017 11:17:30 AM - Göteborgs Universitet IP Address:130.241.16.16
Immunsuppression and probiotics
that probiotics exert their effects not only locally in the gut but are also able to improve the function of the innate and adaptive immune system via different yet not completely elucidated mechanisms. In the three studies from Charité, different probiotic preparations were used: the first two studies tested Lactobacillus plantarum 299, whereas the 2005 study used a synbiotic formulation (Synbiotic 2000) consisting of four lactic acid producing strains Pedicoccus pentasacceus, Leoconostoc mesenteroides, Lactobacillus paracasei subsp. paracasei and L. plantarum in addition to beta-glucan, inulin, pectin and resistant starch as prebiotic components. Results from a trial from Japan in living donor liver transplantation recipients have confirmed these results. In this trial, the rate of postoperative infections was shown to be reduced from 24% to 4% by a synbiotic formulation (Bifidobacterium breve, Lactobacillus casei, and galactooligosaccharide) (Eguchi et al., 2011).
could positively influence GVHD and in fact this has been already confirmed in an animal model (Gerbitz et al., 2004). This hypothesis is further reinforced by the fact that children who consume more yoghurt or other foods containing pro- or prebiotics after stem cell transplantation, have fewer complications after transplantation (Tavil et al., 2012). To date however, no human intervention studies with pre- or probiotics have been published (Van der Meij et al., 2013). Similar to thoracic organ transplantation patients, safety of probiotics is a concern in GVHD. The literature cites one case of sepsis with Lactobacillus acidophilus after autologous stem cell transplantation, however, it should be noted that the patient consumed 6-8 portions daily of a commercially available probiotic yoghurt (Mehta et al., 2013).
A possible further mechanism of action can be found from L. casei DN-114001 supplementation in children after liver transplantation which was shown to decrease the activity of enzymes associated with mucosal damage (Pawlowska et al., 2007). This confirms the animal experiments that showed a protective effect of probiotics on gut permeability and gut microbiome composition after liver transplantation, especially in malnourished animals (Ren et al., 2011). Further animal experiments have shown that probiotics could also protect the liver from damage during an episode of acute rejection; this may be explained by an increase of regulatory T cells and tumour-growth factor beta (Xie et al., 2014).
Patients with HIV infection
Little information is available on the efficacy and safety of probiotic in patients after thoracic organ transplantation. One available report concerns an HIV positive patient after lung transplantation, who developed a pleura empyema with positive cultures for Lactobacillus rhamnosus after having received L. rhamnosus GG as a prophylactic treatment for C. difficile-associated diarrhoea. After this incident, researchers from the University of Pittsburgh reviewed 814 cases of heart and/or lung transplantation who were treated with L. rhamnosus, and found that in eight cases, further infections were caused by lactobacilli. Subsequently, this centre stopped the use of probiotics in patients after thoracic organ transplantation (Luong et al., 2010). At the moment, no human data on probiotics in patients after renal or pancreas transplantation are available.
3. Bone marrow/stem cell transplantation Graft-versus-host-disease (GVHD) can hamper the success of bone marrow or stem cell transplantation. One mechanism of GVHD is the translocation of lipopolysaccharides from the gut. It has been hypothesised that the modulation of the gut microbiome by probiotics Beneficial Microbes 6(6)
4. Other forms of immunosuppression
In HIV, the gut suffers from a reduction of CD4-positive T cells and dendritic cells. This leads to an inflammatory reaction, dysbiosis, increased permeability, and increased translocation of bacterial products (Marchetti et al., 2013). Since probiotics can decrease gut permeability and intestinal inflammation, interventional studies in HIV have been performed (Hummelen et al., 2010). For instance, administration of L. rhamnosus GR-1 has led to an increase in CD4 positive T cells and a decrease in febrile episodes, however, the effect was weaker than anticipated. As reviewed by Van den Nieuwboer et al. (2015), the safety profile of the probiotic intervention in HIV is good, as no side effects have been noted even with high doses. However, the number of studies and the number of tested strains in this setting is limited.
Critically ill patients Critically ill patients are exceptionally prone to infections (e.g. ventilator associated pneumonia) due to the massive inflammatory reaction, the need for parenteral nutrition, and mechanical ventilation. The short-term use of probiotics or synbiotics in some studies has resulted in an improvement of infection rates, complication rates, and different surrogate parameters of gut permeability and immune function. In one study, a decrease in mortality was also found. However, there are also several negative studies that do not show any beneficial effect of probiotic treatment (Jacobi et al., 2011; Madsen, 2008). Furthermore, major safety concerns in the critically ill have arisen from a study in severe acute pancreatitis patients that showed higher mortality due to an increased rate of small bowel ischemia (Besselink et al., 2008).
825
V. Stadlbauer
http://www.wageningenacademic.com/doi/pdf/10.3920/BM2015.0065 - Thursday, September 21, 2017 11:17:30 AM - Göteborgs Universitet IP Address:130.241.16.16
Major surgery During major surgery, the surgical trauma causes a systemic inflammatory reaction that leads to translocation of bacterial products via increased gut permeability and thereby increases the risk of postoperative infections (Figure 1). Several studies with different probiotic strains have been conducted, some with very good results and some showing no effect. Possible explanations for this are the use of different probiotic strains or the heterogeneity of patients after major surgery, where several factors, which cannot be controlled in studies, play a role: postoperative nutrition, operation technique, and differences in health care structure (Bengmark, 2012). Most studies do not report any severe side effects, however, once again, the amount of studies and the number of tested strains are limited. One exception seems to be Saccharomyces boulardii. At least 30 cases of fungemia after the use of S. boulardii have been described. Some patients had major surgery; most of them were also critically ill and had foreign bodies such as central venous catheters or artificial joints that increase the risk of infections (Didari et al., 2014). S. bourlardii is not normally found in the human gut microbiome, therefore it follows that this yeast can cross the gut barrier more easily, especially in immunocompromised subjects.
Liver cirrhosis The incidence of liver cirrhosis is increasing. In the Western world, liver cirrhosis is already the 10th most common cause of death. In liver cirrhosis, dysbiosis and increased gut permeability contribute to the development of further complications, such as hepatic encephalopathy and infections, due to the increased translocation of bacterial products. Since the gut microbiome plays a key role in this hypothesis, strategies to modulate the gut microbiome are of great interest. Probiotics can exert direct (stimulation of tight junctions and modulation of mucin production) or indirect (microbiome composition and immunomodulation) effects on the gut-liver axis. In liver cirrhosis, probiotics have been used to improve liver function, to prevent or treat hepatic encephalopathy, and to prevent infections. Studies aimed at improvement of liver function have shown promising results, however large studies are lacking (Lo et al., 2014). Probiotics have also been used successfully to treat or prevent hepatic encephalopathy (Iwasa and Takei, in press; McGee et al., 2011), however due to small sample sizes and different study designs no recommendations have been made so far in international guidelines.
826
The increased risk of infections in liver cirrhosis is a major problem which leads to high mortality rates. Probiotics may have a positive effect on neutrophil phagocytic capacity, but this has to be proven in larger studies (Stadlbauer et al., 2008). So far no severe side effects of probiotic therapy in liver cirrhosis have been published, which is also in accordance with the personal experience of the author. Therefore, the probiotic strains that have been currently tested and published in literature seem to be safe in this patient group despite impaired innate immunity.
5. Summary and practical considerations The use of probiotics in immunocompromised adults has to be considered carefully. It should be emphasised once more that it is not possible to extrapolate safety information of one or more probiotic strains to all available probiotic strains. Safety as well as efficacy must be evaluated separately for each strain or combination of strains. From the current available literature, probiotic treatment of patients after liver transplantation and patients with liver cirrhosis has not resulted in any safety concerns. Specific strains have been shown to be effective in preventing infections after liver transplantation and for therapy or prevention of hepatic encephalopathy. So far in HIV patients no safety concerns have emerged, but the data are limited. It is difficult to declare safety of probiotics after major surgery, since the data are limited and there is at least some concern using organisms not physiologically present in the human intestine. In critically ill patients, after heart, lung, or bone marrow/stem cell transplantation, while there is insufficient evidence for efficacy, safety is a major concern. Therefore, the risks and benefits have to be considered very carefully. Ideally the safety and efficacy of probiotics should be studied in clinical trials. In conclusion, the use of probiotics in immunocompromised adults is possible. However, sufficient information on the strains used (such as sensibility to antibiotics) is mandatory and in case of unexpected infections, the probiotic strains should be considered as a cause. Furthermore, studies with probiotics need to include more safety aspects such as surveillance cultures of body fluids.
Acknowledgements Winclove Probiotics provided the graphic design for Figure 1. Jessica Younes edited the manuscript.
References Bengmark, S., 2012. Pro- and synbiotics to prevent sepsis in major surgery and severe emergencies. Nutrients 4: 91-111.
Beneficial Microbes 6(6)
http://www.wageningenacademic.com/doi/pdf/10.3920/BM2015.0065 - Thursday, September 21, 2017 11:17:30 AM - Göteborgs Universitet IP Address:130.241.16.16
Immunsuppression and probiotics
Besselink, M.G., Van Santvoort, H.C., Buskens, E., Boermeester, M.A., van Goor, H., Timmerman, H.M., Nieuwenhuijs, V.B., Bollen, T.L., Van Ramshorst, B., Witteman, B.J., Rosman, C., Ploeg, R.J., Brink, M.A., Schaapherder, A.F., Dejong, C.H., Wahab, P.J., Van Laarhoven, C.J., Van der Harst, E., Van Eijck, C.H., Cuesta, M.A., Akkermans, L.M., Gooszen, H.G. and Dutch Acute Pancreatitis Study, G., 2008. Probiotic prophylaxis in predicted severe acute pancreatitis: a randomised, double-blind, placebo-controlled trial. The Lancet 371: 651-659. Chapman, C.M., Gibson, G.R. and Rowland, I., 2011. Health benefits of probiotics: are mixtures more effective than single strains? European Journal of Nutrition 50: 1-17. Didari, T., Solki, S., Mozaffari, S., Nikfar, S. and Abdollahi, M., 2014. A systematic review of the safety of probiotics. Expert Opinion on Drug Safety 13: 227-239. Eguchi, S., Takatsuki, M., Hidaka, M., Soyama, A., Ichikawa, T. and Kanematsu, T., 2011. Perioperative synbiotic treatment to prevent infectious complications in patients after elective living donor liver
Leber, B., Spindelboeck, W. and Stadlbauer, V., 2012. Infectious complications of acute and chronic liver disease. Seminars in Respiratory and Critical Care Medicine 33: 80-95. Lo, R.S., Austin, A.S. and Freeman, J.G., 2014. Is there a role for probiotics in liver disease? Scientific World Journal 2014: 874768. Luong, M.L., Sareyyupoglu, B., Nguyen, M.H., Silveira, F.P., Shields, R.K., Potoski, B.A., Pasculle, W.A., Clancy, C.J. and Toyoda, Y., 2010. Lactobacillus probiotic use in cardiothoracic transplant recipients: a link to invasive Lactobacillus infection? Transplant Infectious Disease 12: 561-564. Madsen, K., 2008. Probiotics in critically ill patients. Journal of Clinical Gastroenterology 42 Suppl. 3 Part 1: S116-S118. Marchetti, G., Tincati, C. and Silvestri, G., 2013. Microbial translocation in the pathogenesis of HIV infection and AIDS. Clinical Microbiology Reviews 26: 2-18. McGee, R.G., Bakens, A., Wiley, K., Riordan, S.M. and Webster, A.C., 2011. Probiotics for patients with hepatic encephalopathy. Cochrane Database of Systematic Reviews: CD008716.
transplantation: a prospective randomized study. American Journal of Surgery 201: 498-502. Food and Agriculture Organization of the United Nations/World Health Organization (FAO/WHO), 2001. Evaluation of health and nutritional properties of powder milk and live lactic acid bacteria. Available at: http://tinyurl.com/8bccc3r. Floch, M.H., 2014. Recommendations for probiotic use in humans – a 2014 update. Pharmaceuticals 7: 999-1007. Gerbitz, A., Schultz, M., Wilke, A., Linde, H.J., Scholmerich, J., Andreesen, R. and Holler, E., 2004. Probiotic effects on experimental graft-versus-host disease: let them eat yogurt. Blood 103: 4365-4367. Gibson, G.R. and Roberfroid, M.B., 1995. Dietary modulation of the human colonic microbiota: introducing the concept of prebiotics. Journal of Nutrition 125: 1401-1412. Hell, M., Bernhofer, C., Stalzer, P., Kern, J.M. and Claassen, E., 2013. Probiotics in Clostridium difficile infection: reviewing the need for a multistrain probiotic. Beneficial Microbes 4: 39-51. Hill, C., Guarner, F., Reid, G., Gibson, G.R., Merenstein, D.J., Pot, B., Morelli, L., Canani, R.B., Flint, H.J., Salminen, S., Calder, P.C. and Sanders, M.E., 2014. Expert consensus document. The International Scientific Association for Probiotics and Prebiotics consensus
Mehta, A., Rangarajan, S. and Borate, U., 2013. A cautionary tale for probiotic use in hematopoietic SCT patients – Lactobacillus acidophilus sepsis in a patient with mantle cell lymphoma undergoing hematopoietic SCT. Bone Marrow Transplantation 48: 461-462. Pawlowska, J., Klewicka, E., Czubkowski, P., Motyl, I., Jankowska, I., Libudzisz, Z., Teisseyre, M., Gliwicz, D. and Cukrowska, B., 2007. Effect of Lactobacillus casei DN-114001 application on the activity of fecal enzymes in children after liver transplantation. Transplantation Proceedings 39: 3219-3221. Rayes, N., Seehofer, D., Hansen, S., Boucsein, K., Muller, A.R., Serke, S., Bengmark, S. and Neuhaus, P., 2002a. Early enteral supply of Lactobacillus and fiber versus selective bowel decontamination: a controlled trial in liver transplant recipients. Transplantation 74: 123-127. Rayes, N., Seehofer, D., Muller, A.R., Hansen, S., Bengmark, S. and Neuhaus, P., 2002b. [Influence of probiotics and fibre on the incidence of bacterial infections following major abdominal surgery – results of a prospective trial]. Zeitschrift fuer Gastroenterologie 40: 869-876 [in German]. Rayes, N., Seehofer, D., Theruvath, T., Schiller, R.A., Langrehr,
statement on the scope and appropriate use of the term probiotic. Nature Reviews Gastroenterology and Hepatology 11: 506-514. Hummelen, R., Vos, A.P., Van’t Land, B., Van Norren, K. and Reid, G., 2010. Altered host-microbe interaction in HIV: a target for intervention with pro- and prebiotics. International Reviews of Immunology 29: 485-513. Iqbal, M.Z., Qadir, M.I., Hussain, T., Janbaz, K.H., Khan, Y.H. and Ahmad, B., 2014. Review: probiotics and their beneficial effects against various diseases. Pakistan Journal of Pharmaceutical Sciences 27: 405-415. Iwasa, M. and Takei, Y., in press. Pathophysiology and management of hepatic encephalopathy 2014 update: ammonia toxicity and hyponatremia. Hepatology Research. DOI: http://dx.doi. org/10.1111/hepr.12495. Jacobi, C.A., Schulz, C. and Malfertheiner, P., 2011. Treating critically ill patients with probiotics: Bbeneficial or dangerous? Gut Pathogens 3: 2.
J.M., Jonas, S., Bengmark, S. and Neuhaus, P., 2005. Supply of pre- and probiotics reduces bacterial infection rates after liver transplantation – a randomized, double-blind trial. American Journal of Transplantation 5: 125-130. Ren, Z.G., Liu, H., Jiang, J.W., Jiang, L., Chen, H., Xie, H.Y., Zhou, L. and Zheng, S.S., 2011. Protective effect of probiotics on intestinal barrier function in malnourished rats after liver transplantation. Hepatobiliary and Pancreatic Diseases International 10: 489-496. Rijkers, G.T., De Vos, W.M., Brummer, R.J., Morelli, L., Corthier, G. and Marteau, P., 2011. Health benefits and health claims of probiotics: bridging science and marketing. British Journal of Nutrition 106: 1291-1296. Schrezenmeir, J. and De Vrese, M., 2001. Probiotics, prebiotics, and synbiotics – approaching a definition. American Journal of Clinical Nutrition 73: 361S-364S.
Beneficial Microbes 6(6)
827
http://www.wageningenacademic.com/doi/pdf/10.3920/BM2015.0065 - Thursday, September 21, 2017 11:17:30 AM - Göteborgs Universitet IP Address:130.241.16.16
V. Stadlbauer
Stadlbauer, V., Mookerjee, R.P., Hodges, S., Wright, G.A., Davies, N.A. and Jalan, R., 2008. Effect of probiotic treatment on deranged neutrophil function and cytokine responses in patients with compensated alcoholic cirrhosis. Journal of Hepatology 48: 945-951. Steyer, G.E. and Pfeifer, J., 2012. Multispezies Probiotika und Antibiotika. Review zur klinischen Evidenz bei der Prävention Antibiotika-Assoziierter Diarrhoe (AAD) und Clostridium difficileInfektionen (CDI). OM & Ernährung 141: 38-41 [in German]. Tavil, B., Koksal, E., Yalcin, S.S. and Uckan, D., 2012. Pretransplant nutritional habits and clinical outcome in children undergoing hematopoietic stem cell transplant. Experimental and Clinical Transplantation 10: 55-61. Van den Nieuwboer, M., Brummer, R.J., Guarner, F., Morelli, L., Cabana, M. and Claasen, E., 2015. The administration of probiotics and synbiotics in immune compromised adults: is it safe? Beneficial Microbes 6: 3-17.
828
Van der Meij, B.S., De Graaf, P., Wierdsma, N.J., Langius, J.A., Janssen, J.J., Van Leeuwen, P.A. and Visser, O.J., 2013. Nutritional support in patients with GVHD of the digestive tract: state of the art. Bone Marrow Transplantation 48: 474-482. Xie, Y., Chen, H., Zhu, B., Qin, N., Chen, Y., Li, Z., Deng, M., Jiang, H., Xu, X., Yang, J., Ruan, B. and Li, L., 2014. Effect of intestinal microbiota alteration on hepatic damage in rats with acute rejection after liver transplantation. Microbial Ecology 68: 871-880. Xie, Y.R., Liu, S.L., Liu, X., Luo, Z.B., Zhu, B., Li, Z.F., Li, L.J., He, Y., Jiang, L., Li, H. and Ruan, B., 2011. Intestinal microbiota and innate immunity-related gene alteration in cirrhotic rats with liver transplantation. Transplantation Proceedings 43: 3973-3979.
Beneficial Microbes 6(6)
