The high success rate of FMT to patients with recurrent C. difficile infection makes this an attractive treatment and raises hopes that microbial transplants could be effective also for other indications. However, the potential adverse effects of this line of treatment remains to be determined in large scale and the findings should be contrasted with a control group. The main objective of this study was to determine the long‐term safety of FMT in the treatment of C. difficile infection and also evaluate the effect of FMT on GI symptoms and general well‐being and to contrast the results to a group of patients successfully treated with antibiotics.

A recent systematic review emphasised that there is not enough consistency in the long‐term follow‐up of adverse events after FMT. 17 In previous studies, the duration of the follow‐up period has ranged from 3 weeks to 8 years. 19 - 24 However, the study with the longest follow‐up period only had 12 patients. 21 Moreover, the previous studies have not concentrated on the GI symptoms or compared the recovery of the patients to a control group. There is some evidence of the safety of the procedure itself, but the long‐term safety to the patients’ health has not been well described. The majority of the studies reported little or no adverse effects during the follow‐up period. Some of these included reports of new medical conditions after FMT (four patients) 25 such as peripheral neuropathy, Sjögren's disease, idiopathic thrombocytopenic purpura, and rheumatoid arthritis. In these long‐term follow‐up studies, the treatment efficiency has been very good with primary cure rates ranging from 88.2% to 100%.

The long‐term implications of FMT treatment or how it compares to the long‐term recovery of patients treated with antibiotics has so far not been fully addressed. Despite rigorous testing of the donor's stool and blood, there still remains a potential risk of transmitting agents that do not cause immediate infection, but may complicate the patient's treatment in the future. For example, contracting multidrug‐resistant, Gram‐negative bacteria or developing or aggravating autoimmune diseases have been a cause of concern. 15 Moreover, because of the possible systemic effects of the transplanted microbiota, conditions such as metabolic syndrome, neuro‐psychiatric conditions, autoimmune and atopic diseases are sometimes used as reasons for excluding donors, 15 - 18 although the basis for these potential adverse effects is controversial. Therefore, long‐term analysis of this patient group and comparison to controls is vital for understanding of the long‐term implications of FMT treatment.

Faecal microbiota transplantation (FMT) is proven to be a highly effective treatment for patients suffering from recurrent Clostridium difficile infections unresponsive to antibiotic treatments, with a success rate of 81%‐94%. 1 - 4 In addition, the FMT has been rising hopes as a new treatment avenue for other diseases such as irritable bowel syndrome and more systematic conditions such as metabolic syndrome. 5 , 6 Regardless of the high interest towards FMT treatment, there are still some concerns regarding the risk of transmission of other diseases to patients via the microbiome. Moreover, longitudinal follow‐up of the patient's GI symptoms and general wellbeing is lacking. The short‐term safety of the FMT treatment to patients with recurrent C. difficile infection has been clearly demonstrated. A systematic review of 536 patients treated with FMT, reported no transmission of infective agents or severe adverse effects. Since the majority of these patients were followed up for less than 1 year, these results cannot be directly extrapolated to long‐term effects. 7 Several case reports have reported short‐term adverse effects such as mild fever, abdominal pain, diarrhoea, exhaust, flatulence, fatigue, diverticulitis, bacteraemia, norovirus gastroenteritis, cytomegalovirus infection and activation of ulcerative colitis. 8 - 14

The patients were treated with vancomycin or metronidazole until a reduction in symptoms occurred. This treatment was discontinued on average 36 hours before the transplantation and the patients performed a bowel cleansing prior the FMT. The procedure was determined as successful if a resolution of symptoms occurred or C. difficile culture and toxin measurements were negative. Two patients received FMT for the second time, 6 or 9 months after their first FMT. One patient mistakenly continued to using antibiotics after the FMT, and another patient received antibiotics for an unrelated infection. In both cases the C. difficile infection recurred after the use of antibiotics, and was resolved by the second FMT, after which the follow‐up data were collected.

The patients in the FMT group were all referred to HUS Infectious Diseases Clinic for C. difficile infection that was refractive to standard therapy. Exclusion criteria for FMT included any contraindication for colonoscopy and inadequate mental status or dementia. The screening of the donor and the faecal transplantation process has been previously described. 1 , 26 Stool was donated by either the patient's relatives, individuals in intimate physical contact with the patient such as their spouse or universal donors. In line with a recent consensus report, 27 the donors were suitable if they had not had antimicrobial treatment in 6 months, did not have any intestinal symptoms, obesity, high risk of sexual behaviour or history of cancer or other severe disease. Donor blood samples tests also included total blood count, C‐reactive protein, creatinine and liver enzymes. In case of universal donors, the stool was frozen according the protocol described by Satokari and colleagues. 26

All together 130 patients (55 patients in the FMT group and 75 patients in the antibiotic, AB‐group) were sent a 45‐item questionnaire collecting information about the patient demographics, their physical and mental health, allergies, infections, gastroenterological conditions such as IBD and IBS, diabetes, autoimmune diseases, neurological disorders, mental wellbeing and malignancies (for the English translated questionnaire see Data S1 ). The selected questions were taken from validated Rome III questionnaire. The use of medication, antibiotics as well as the patients’ willingness to FMT treatment in the future was recorded. The filled questionnaire was returned by 84 patients (64.6%) of which 45 were successfully treated with FMT and 39 with antibiotics. The information for the questionnaires was completed by reviewing patients’ medical records and interviewing patients when necessary.

In both groups, the patients had had at least two episodes of C. difficile infection, one initial and one recurrent infection in during a 6‐month period. Our routine is to use FMT after three relapses of C. difficile infection, but we have done FMT for a few patients after the second relapse due to the very severe previous C. difficile infection episodes. In both groups, the primary infection was treated either with metronidazole or vancomycin or with both medicines depending on diseases severity. In the antibiotic group, the recurrent infections were treated with either metronidazole or vancomycin until either resolution of symptoms or a negative C. difficile toxin laboratory test. FMT treatment was available throughout the follow‐up period independent of availability of family donors.

This study was a retrospective comparative observational follow‐up study on patients who were successfully treated for recurrent C. difficile infection in the Hospital District of Helsinki and Uusimaa (HUS) area in 2007‐2014. The study had the ethical approval of HUS (Dnro 48/2013) and all patients provided an informed consent. The treatment group received FMT for recurrent C. difficile infection and the control group patients were treated with antibiotics. FMT‐group patients contained some subjects whom had previously had a serious, life threatening infection and to prevent further recurrent C. difficile infection episodes they were given the FMT treatment. The patients were not selected to a certain treatment group based on the previous GI‐tract complications. The controls were selected from the infectious diseases register of Helsinki and Uusimaa hospital district to match patients in the FMT group in age, sex and number of infection episodes.

The number of patients reporting their rate of recovery in both groups. The FMT treated patients reported significantly more often to be recovered from the Clostridium difficile infection within 24 hours or 2‐3 days. The antibiotic treated patients reported significantly more often that the recover from the infection took longer than a week. Significant changes indicated with an asterisk

We also wanted to estimate if there were differences in the recovery rates between the treatment groups by asking the patients how well they recovered from the given treatment. The recovery of the FMT treated patients was significantly faster than that recorded by the antibiotic treated patients (Figure 6 ). In the FMT group, 77.8% of the patients reported to have been cleared from all symptoms of C. difficile infection within 3 days or less, whereas only 23.1% of the AB treated patients reported the same ( P = 8.95*10 −9 ).

The willingness for a patient to undergo FMT treatment has been discussed previously and we aimed to retrospectively address the patients’ views on the treatment and willingness to undergo FMT treatment in the future. In this cohort 97.6% of the FMT treated patients would prefer FMT as their initial treatment instead of antibiotics ( P = 1.21*10 −5 , Figure 5 ) in the future. This preference was also detected in the AB group, where 60% of the patients would also want FMT as the initial treatment. In this same group of patients 33.3% would be willing to try it if antibiotics gave no results, and only 6.7% would accept solely antibiotic treatment.

Enteric infections and antibiotics use have been linked to increased risk of developing functional gastrointestinal disorders also effecting the upper intestinal tract. 30 We aimed to study if there were alterations in the incidence of these symptoms in our patient cohort. Here, the patients treated with antibiotics were experiencing statistically significantly more symptoms of the upper intestinal tract than the FMT treated patients (prevalence AB = 51.3%, FMT = 31.1%, P = .045, Figure 4 ). The most frequently recorded symptom in both groups was pain in the upper GIT, where the prevalence was 25.6% in the AB group and 11.1% in the FMT group ( P = .06). In addition, there was a significant difference in the recorded experience of feeling bothersome fullness after a meal between the study groups (FMT = 4.4%, AB = 18.0%, P = .05). We also surveyed the intensity of upper intestinal tract symptoms and recorded that 5 patients in the FMT group reported decreased symptoms, compared to 1 in the AB group. However, the majority of patients in both groups reported no change in symptoms, although the difference between FMT and antibiotic treated patients was significant (FMT = 75.6%, AB = 64.1%, P = .04, Figure S1 ).

It has been estimated that 25% of the patients with previous C. difficile infection suffer from IBS like symptoms after the infection has been cleared. 29 Therefore, we aimed to investigate whether there are differences in the incidence of functional gastrointestinal disorders, specifically symptoms associated with irritable bowel syndrome and symptoms of dyspepsia between the FMT and AB treated patients. The subjects in the AB group recorded more frequently that their bowel function had become worse and more irregular after clearing the infection as compared to FMT treated patients (FMT = 11.1%, AB = 35.9%, P = .034). In contrast, the subjects in FMT group most often recorded that their bowel function had become better and more regular after the treatment (FMT = 53.3%, AB = 25.6%, P = .016, Figure 1 ). Moreover, we noted that a lower proportion of the patients treated with FMT (77.8%) experienced gastrointestinal symptoms related to IBS, whereas 92.3% of antibiotic treated patients recorded these symptoms with borderline statistical significance (Figure 2 , P = .06). The experience of individual gastrointestinal symptoms did not differ between the treatment groups ( P > .05, Figure 2 ). The most commonly experienced symptom in both groups was flatulence (FMT = 55.6%, AB = 69.2%). Other common intestinal symptoms in the FMT group were urgency to defecate (53.3%) and loose stools (51.1%). In the AB treated group other common GI symptoms included abdominal pain (56.4%), bloating (53.9%) and loose stools (51.3%).

There were no statistical differences the incidence of more severe disease conditions between the groups. We concentrated in the prevalence of IBD, diabetes, diseases of the nervous system, autoimmune diseases, incidence of gastrointestinal polyps and cancer between the study groups and found that there were no statistical differences in the prevalence of new cases between the groups. In more detail; in this cohort, there were 14 new or worsened cases of nervous system related diseases. The most reported conditions were migraine (8 cases, FMT = 4 and AB = 4) and dementia (6 cases, FMT = 3, AB = 3). There were four cases of new autoimmune diseases, two cases of autoimmune thyroiditis (FMT = 1, AB = 1) and in the AB group one case of psoriasis and one case of rheumatoid arthritis. In patients who were diagnosed with diabetes, there was no change in the symptoms and only one new case of diabetes was diagnosed in the antibiotics group during the follow‐up period. There were no new cases of polyps, cancer or IBD in either of the patient groups after the treatment.

The potential incidence of new allergies has also been speculated due to the drastic modifications in the intestinal microbiota introduced by the condition. We found that there was no statistical difference in the occurrence of allergies before or after the treatment between the groups, although twice as many patients in the AB‐group developed new allergies during the follow‐up period compared to the FMT group. Majority (6/9) of the new allergies wassensitivities to food components and the patients reported that the allergy symptoms effected their GI function. There were four reported new allergies in the FMT group, which included sensitivity to chemicals, birch pollen and new food allergies. There was one recorded case of coeliac disease prior to the treatment of patients with recurrent C. difficile infection (FMT group) and there were no cases in the AB group. There were no new reported cases of coeliac disease after the treatment.

As the long‐term effects of FMT have not been previously validated, our aim was to determine both the intestinal and extra‐intestinal symptoms that are potentially associated with FMT treatment and to compare the symptom prevalence between patients treated with either antibiotics or FMT (Table 2 ). First, the potential increase in body weight after FMT treatment has been speculated. We found no statistical difference in the starting body weight or change in the patients’ weight between the groups. On average 80% of the patients gained weight after the treatment (average weight gain 1.9 kg), however, the range of weight gain/loss varied in both groups.

The number of episodes before a successful treatment was reviewed from the patient registry as a positive C. difficile culture or toxin test. Positive results that were 14 days or further apart were regarded as separate episodes. The follow‐up period was calculated from the last negative C. difficile culture or toxin test or the day of receiving FMT until the date we received the last questionnaires from the patients. There were two patients in the FMT group who consumed antibiotics shortly after the FMT. Both of these patients relapsed and were then treated successfully with a second FMT. The first mistakenly continued to using the prophylactic vancomycin treatment after first FMT treatment (the patient and recovery previously described 28 ) and the other patient received antibiotics for an unrelated infection. There were three patients whom were initially selected for the antibiotics group, but it was later found that they had received a FMT in a private health‐centre. Therefore, these patients were moved into the FMT group, but as the date of the FMT was not known, their follow‐up periods could not be estimated. In addition, there were 26 patients in the FMT group and 28 in the AB group who received antibiotics during the follow‐up period for unrelated indication. Two patients in the FMT group and seven in the control group could not estimate the number of antibiotic treatments received in the follow‐up period. For those who could make an estimation, the average number of antibiotic treatments was 3.0 (range 1‐10) in the FMT group and 3.3 (range 1‐10) in the control group. The antibiotics were consumed on average 15.7 months after the treatment (range 3‐48 months). These antibiotic treatments did not make the patients more susceptible to another C. difficile infection episode.

The recovery of 84 patients suffering from recurrent Clostrium difficile infection was followed on average for 3.8 years. The range of the follow‐up period was very similar in both study groups as well as the number of episodes before the treatment, making the treatment groups comparable. All patients were successfully treated with either FMT (n = 45) or antibiotics (AB, n = 39). The groups were age and gender matched although in both groups the majority of patients were female (77.8% FMT group and 79.5% AB). The demographics of the study population can be seen in Table 1 .

4 DISCUSSION

We present here the first controlled long‐term follow‐up study of FMT treated patients compared with antibiotic therapy, focusing on the safety aspects of these treatments. The long‐term safety of FMT has been under a lot of discussion, and several studies have pointed out the need for longer follow‐up times where adverse effects are actively sought.17, 25, 31 Especially the development of extra‐intestinal conditions, such as autoimmune diseases or weight gain, has been an issue of concern. Our study confirms that FMT is an effective and safe treatment for recurrent C. difficile infection also in long term. FMT did not affect the patients weight or increase the risk of severe diseases such as cancer, autoimmune diseases or allergies compared to patients treated only with antibiotics. Furthermore, our results suggest that FMT has some favourable effects for the GI symptoms compared to the antibiotic treatment and also the clearance of GI symptoms after the infection was faster in patients receiving FMT. Although, this treatment suffers from prejudice against faeces and the need of endoscopy, which both could decrease the patient's adherence to the treatment. We found that the majority of patients both in the antibiotic and FMT groups would prefer FMT treatment over the antibiotics for recurrent C. difficile infection.

The recently published European consensus conference indicates the history of chronic, systemic autoimmune disorders with GI involvement and the history of, or high risk for, GI cancer or polyposis as some of the key issues in selecting potential donors.7 We have selected our donors in accordance with this recommendation. None of our patients developed cancer during the follow‐up period and autoimmune disease appeared in only few new patients equally in both groups. Unbalanced gut microbial population, so called dysbiosis, may also increase the risk for allergies31 and antibiotic treatment taken by all study participants would result into considerable changes to their intestinal microbial composition. The incidence of allergies before or after the treatment between the groups were not different, although twice as many patients in the antibiotic group developed new allergies during the follow‐up period compared to those receiving the FMT. The limitation of this study is that the study population could have been even lager and the follow‐up period longer to better highlight differences in, eg, cancer or neurological disease development. Although FMT is a curative therapy for recurrent C. difficile infection and seems to be a very safe treatment, we stand for the implementation of national registry data collections to further investigate the long‐term health implications. Taken together, during the long‐term follow‐up there was no difference in the incidence of any severe diseases between the FMT or antibiotic treated patients.

Higher prevalence of functional gastrointestinal disorders in patients with C. difficile infection has been shown,32 however how these numbers are related to the treatment avenue has not been addressed in detail. In this study, we showed that patients in the FMT group recorded that their bowel function had become significantly better and more regular after the treatment compared to those who received the traditional antimicrobial therapy. In addition, they also reported less symptoms of functional gastrointestinal disorders than the AB group patients. Previously it has been shown that a quarter of C. difficile infection patients without prior irritable bowel syndrome (IBS) diagnosis develop post‐infectious IBS (PI‐IBS) during 6 months after clearing the infection.29 Faecal microbiota diversity has been found to be reduced in PI‐IBS, which has been shown to inversely correlate with lamina propria lymphocytes, immunological markers and psychological scores suggesting a possible link between dysbiosis, inflammation and stress in PI‐IBS.33, 34 The reason for this has been hypothesised and some risk factors for PI‐IBS in patients with C. difficile infection have been found including anxiety and age under 60 years.29, 35 Interestingly, in this cohort one‐third of the FMT treated patients showed improved mental status. Thereby, the risk of newly developed mental problems after FMT seems low with carefully selected and screened donors. There is some evidence that gut microbiota can influence cognition and behaviour, and that modifications of the microbiota can induce depressive‐like behaviours. Vice versa, changes in behaviour can also alter gut microbiota composition.36

The use of broad‐spectrum antibiotics, particularly macrolides or tetracyclines, has been speculated to be associated with IBS development in this patient group, linking the C. difficile infection treatment and symptom development.37 Aroniadis and colleagues recently showed in a small study that abdominal symptoms such as pain and tenderness improved after FMT.20 Our study, evaluating more thoroughly the different GI symptoms showed that patients receiving FMT had significantly less symptoms of functional GI‐disorders when compared to the patients treated with antibiotics. This all suggests that restoration of the microbiota ecosystem could be more beneficial to the host than antibiotic treatment alone.

A recent study showed that patients with C. difficile infection have higher prevalence of upper intestinal tract symptoms than controls.32 Interestingly, we found a significant difference in the recorded functional dyspepsia‐like symptoms including pain in the upper GI‐tract and feeling of fullness between the FMT treated and antibiotic treated subjects. The number of C. difficile infection patients without GI symptoms was more frequent after FMT than after receiving only antibiotics, which along with significantly better bowel function, might be one reason for the higher mental well‐being in FMT patients compared to the AB‐group. These findings suggest that the re‐establishment of the patient's intestinal microbiota as opposed to decreasing of the microbial diversity may play a protective role in the development of upper GI symptoms in patients with C. difficile infection after treatment.

The intestinal microbiota of patients with C. difficile infection has been shown to be greatly impoverished due to both the condition and the antimicrobial treatments attempted for treatment.2, 28 We recently showed that the intestinal microbiota composition of a C. difficile infection patient could be relatively permanently altered with FMT to resemble that of their own donor, and that this shift in the microbial composition lasted throughout the 1‐year follow‐up period.28 Building on these findings, the results of this retrospective trial suggest that the FMT treatment is not only safe for the patient, but also more beneficial to the patient as compared to AB treatment. This success could lie in the re‐establishment of the microbial ecosystem to resemble that of a healthy gut rather than only successfully removing the pathogen. Therefore, on the bases of the presented results as well as the past literature the current recommendation to use FMT therapy only after three recurrences of C. difficile infection, could be revised. The safety of the FMT, both short‐ and long term as well as reduced GI symptoms in the FMT group suggest that FMT treatment could be considered earlier as a treatment option.