28 Role of antibiotics and probiotics in the
management of inflammatory bowel disease
PHILIPPE MARTEAU AND FERGUS SHANAHAN
Introduction
An infectious cause or contribution to the primary pathogenesis of inflammatory bowel disease (IBD) has not been demonstrated, ahhough many studies have followed that track [1]. However, the deleterious role of some microorganisms from the endogenous flora is also now well estabhshed in the majority of models of colitis or enteritis [1-4]. Antibiotics have a weU-estabHshed role in the management of compli- cations of IBD such as abscess and pouchitis.
Whether antibiotics are of use as a primary therapy for either Crohn's disease (CD) or ulcerative colitis (UC) is less clear. An alternative way of influencing intestinal ecology is the use of probiotics or pre- biotics. Probiotics are defined as living non-patho- genic microorganisms which, when ingested, exert a positive influence on host health or physiology [5, 6].
Prebiotics have been defined as non-digestible food ingredient that beneficially affects the host by selec- tively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, that have the potential to improve host health [7]. As some animal studies have shown that probiotics or prebiotics may help in preventing or curing experi- mental colitis, clinical trials have begun in IBD.
This chapter focuses on the use of metronidazole and ciprofloxacin in CD and pouchitis. In addition, existing data on the use of other antimicrobial agents and on the potential for probiotics in IBD is reviewed.
Background - rationale for
tlierapeutic manipulation of enteric flora in IBD
Although the etiology is unclear, considerable advances have been made in understanding the
pathogenesis of CD and UC. This involves an inter- action between three contributory cofactors: host susceptibility, mucosal immunity and the resident enteric bacterial flora. Experimental models suggest that the inflammatory response in IBD is the result of abnormal immunologic reactivity to normal flora in a genetically susceptibile host, rather than an appro- priate immune response to an abnormal or patho- genic flora [2-4]. Although a specific pathogenic infection has not been implicated that could account for most cases of IBD, heterogeneity may exist and enteric infections might also act as cofactors influencing mucosal immune development and/or have an impact on the timing or clinical onset and phenotype of IBD.
The mucosal immune system senses and interprets the local microenvironment; under normal circum- stances it exhibits a restrained response to commen- sal flora (tolerance) which is coupled with the capa- city to react effectively to episodic challenge from pathogenic bacteria (immunity). This requires exqui- sitely precise regulation. In susceptible individuals, IBD may arise due to a breakdown in immunologic tolerance to the normal enteric bacteria [1, 2]. The pattern of the pathologic immunoinflammatory response is determined by the profile of mucosal cytokines generated which is, in part, genetically regulated and probably influenced by previous immunologic experience including types and timing of exposure to childhood mucosal infections. CD is associated with type 1 helper T cell (Thl) cytokines, such as interferon-y, tumor necrosis factor (TNF)-oc, and interleukin-(IL)-12, although there is some evi- dence that the profile of mucosal cytokines in early lesions may differ from that of chronic lesions [1, 8, 9]. Ulcerative colitis, in contrast, does not fit easily into the T h l / T h 2 paradigm; it does not represent a Thl response and appears, at least in established disease, to be a modified Th2 response associated with cytokines such as IL-5 and IL-10 [8-10].
Stephan R. Targan, Fergus Shanahan andLoren C. Karp (eds.), Inflammatory Bowel Disease: From Bench to Bedside, 2nd Edition, 573-585.
© 2003 Kluwer Academic Publishers. Printed in Great Britain
Most currently available drug therapies for either CD or UC suppress or modulate the host immune and inflammatory response at both systemic and mucosal levels [11]. Until recently, little attention has been directed toward modifying the enteric microenvironment. A striking example of the impor- tance of controlling environmental influences on IBD is the adverse effect of smoking on the clinical course of CD [12]. In addition, the impact of envir- onmental infections on the mucosal immuno- inflammatory response is dramatically illustrated by the apparent capacity of helminthic infections to switch mucosal cytokine production in patients with CD from a Th 1 profile toward a Th2 [13]. Indeed, one of the suggested reasons for the increase in preva- lence of CD within developed countries within recent decades is reduced exposure to helminthic and other parasitic infections [14].
For patients with established disease, therapeutic modification of the resident bacterial flora with antibiotics or probiotics has recently attracted considerable scientific and clinical research interest and off'ers another opportunity to influence the mucosal cytokine milieu. However, modification of the enteric flora is not a simple exercise - the flora within the human intestine are complex and dynamic with 400-500 bacterial species accounting for 1-2 kg of intestinal content and a collective metabolism tantamount to that of a virtual organ the neglected organ [15, 16]. While antibiotics may appear an obvious method for modifying the flora, they are too non-specific, pose a risk of overgrowth with patho- gens such as Clostridium difficile, and the potential for development of antibiotic resistance. Probiotics offer the advantage of more measured and controlled
manipulation of the flora in IBD and they have properties beyond a simple antimicrobial effect [4-6, 17-18]. In addition, probiotics offer the prospect of genetically modified organisms designed for delivery of important biological molecules including IL-10, vaccines and other biologically important molecules [18-20].
The rationale for therapeutic modification of the enteric flora in patients with established IBD is based on two main lines of evidence. First, is the beneficial conditioning influence of the commensal bacterial flora on intestinal structure and function under normal circumstances. Second is a body of evidence implicating the enteric flora in driving the mucosal inflammatory response in susceptible individuals (Table 1) [21-38].
Epithelial cells have been described as sensors of pathogenic infection, and cytokine signaling by the epithelium has been well described in the context of enteric pathogenic infections [39]. However, bidirec- tional dialog between the host and the normal flora is also evident [22, 40]. Indeed, evidence for influence of the enteric flora on mucosal integrity is well illustrated in germfree animals, where there is reduced epithelial turnover, vascularity, luminal enzyme activity, mucosal-associated lymphoid tissue and thickness of bowel wall. In addition, there are alterations in peristalsis and immune function [23].
Thus, the flora exchange regulatory signals not only with the epithelium but with the subepithelial cells within the intestine [4, 41, 42]. Evidence implicating the resident bacterial flora as an essential cofactor driving the inflammatory process in IBD is based on observational yet persuasive data from human stu- dies and direct experimental results using animal
Table 1. Rationale for therapeutic manipulation of enteric flora in IBD
Observational and experimental lines of evidence
Conditioning effects of resident flora on mucosal structure and function including epithelial turnover, blood flow, peristalsis, immune development and function
Lesions in IBD occur in areas of highest bacterial exposure Clinical response to diversion of fecal stream, relapse on restoration Experimental induction of inflammation by exposure to fecal material Immunologic reactivity to flora in patients with IBD (loss of tolerance) Attenuation of inflammation in animal models of IBD when germfree Experimental transfer of colitis with T cells reactive to bacterial antigens Influence of antibiotics and probiotics in experimental animals and in pouchitis
References 4,16,21-23
24,25 26,27 28-33 34,35 36 37,38
*References are representative, not comprehensive.
models (Table 1). Perhaps the most persuasive argument is the transfer of enterocolitis using T cells that are reactive to enteric bacteria in an animal model of IBD [36].
In summary, although the lessons of Helicobacter pylori and peptic ulcer disease are sobering, and a search for a specific infectious etiology for IBD will continue [4, 8, 43], the bulk of evidence suggests that IBD is not a simple struggle between microbe and humans but rather a more complex interplay amongst genes, commensals and immune cells.
There is a sound rationale for therapeutic alteration of the enteric flora and, as discussed below, the evidence for its efficacy as an adjunct to existing therapies is promising.
Metronidazole
Metronidazole is a nitroimidazole compound that has a clinically useful antimicrobial spectrum against anaerobes, particularly gut anaerobes, as well as certain intestinal protozoan infections. Metronida- zole is a prodrug which has no antimicrobial proper- ties until it is activated by bacterial enzymes [44]. The size of the bacterial flora in the colon and the proportion of anaerobes in comparison with the small bowel may account for differences in efficacy of metronidazole in colonic and small bowel CD.
The actual mode of action of metronidazole in CD is uncertain and may not be limited to its antimicro- bial activity [4, 44] as metronidazole also has i m m u n o m o d u l a t o r y effects and tissue-healing properties [46].
A role for metronidazole in CD was first suggested by Ursing and Kamme in 1975 [47]. Since then, its clinical usefulness in CD has been the subject of few well-designed studies but much debate. Metronida- zole has some beneficial effect in ileocolonic CD. As discussed later, this has been shown in randomized controlled trials. Metronidazole has also been shown to be effective in perineal CD, although a rando- mized controlled study proving the efficacy in this setting has not been performed. Metronidazole is not effective in isolated small bowel CD but decreases the risk of recurrence of ileal lesions after ileocolonic resection for CD. Open studies and two randomized controlled trials have shown that it is not effective in UC when used alone or as an adjunct to cortico- steroids [48-50]. The results of the randomized trials are summarized in Table 2.
Ileocolonic Crohn's disease
Blichfeldt et al. [51] evaluated metronidazole as adjunctive therapy (patients were allowed to use prednisone or salazosulfapyridine) compared to placebo in a double-blind, crossover study. They found no overall benefit of metronidazole except in the subset of six patients with colitis only, in which there was considerable improvement. The Coopera- tive Crohn's Disease Study in Sweden [52] compared metronidazole, 800 mg/day, as primary therapy to sulfasalazine, 3 g/day. Although this was a double- blind, crossover study, there was no placebo control.
The authors found metronidazole and sulfasalazine to be equally effective therapy. Small bowel disease alone did not benefit, as only two subjects of 12 in this subset on metronidazole improved. Of note, in this trial, just over half the patients responded to either therapy and only 25% of metronidazole patients achieved quiescent disease. Ambrose et al.
[53] compared metronidazole alone, metronidazole plus cotrimoxazole, cotrimoxazole alone and placebo in a randomized trial of 1 month involving 72 patients. No difference of response was observed between the four groups. In a 16-week randomized, placebo-controlled trial by Sutherland etal. [54], two different doses of metronidazole were compared with placebo in patients with active CD. By the end of the trial there was no difference in attaining remission in either of the metronidazole groups compared to placebo (27% for both metronidazole groups versus 25% for placebo). However, more individual patients on metronidazole showed some improvement in their Crohn's Disease Activity Index (CDAI) com- pared with patients using placebo. Prantera et al. [55]
compared, in a 12-week randomized trial, the effi- cacy of a combination of metronidazole (250 mg four times daily) plus ciprofloxacin (500 mg twice daily) vs methylprednisolone (0.7-1 mg/kg followed by tapering) in 41 patients with active CD. Clinical remission was observed in 45.5%) of the patients receiving the antibiotics vs 63% in the steroid group (n.s.). There were more side-effects in the antibiotic group (27.3%) vs 10.6%). The authors concluded that, despite the high incidence of adverse events, this combination of antibiotics could be an alternative to steroids in the treatment of acute CD for the patients who tolerate the drugs.
Rutgeerts et al. performed two randomized
controlled trails demonstrating that metronidazole
and ornidazole are significantly eff'ective in the
prevention of postoperative recurrence of CD after
ileal resection [56, 57]. In the first trial, 60 patients
Table 2. Randomized controlled trials with nitrolmldazole compounds in Crohn's disease
Indication No Treatment and design Dose of IVIZ and duration Results (nitroimidazole-control) Ref.
Active CD Active CD Active CD
Active CD
21 78 72
105
IVIZ vs placebo crossover MZ vs salazopyrin crossover
MZ vs cotrimoxazole vs both vs placebo
MZ vs placebo
1 g/day, 1 month 0.8 g/day, 4 months 0.8 g/day, 4 weeks
10 or 20 mg/kg per day, 16 weeks
n.s.; MZ effective for colonic CD n.s.
n.s.
Remission: 27% vs 25% n.s.;
the mean decrease of CDAI was 51 52 53
54
Active CD 41
Prevention of 60 postoperative
recurrence
Prevention of postoperative recurrence Pouchitis
71
13
MZ -I- ciprofloxacin vs methylprednisolone MZ vs placebo
Ornidazole vs placebo
MZ vs placebo, crossover
1 g/d of MZ and ciprofloxacin, 12 weeks 20 mg/kg per day,
3 months
1 g/day, 12 months
1.2 g/day, 2 weeks
greater in MZ treated patients.
Greater effect of MZ in patients with colonic involvement
Remission 45.5% vs 63% (n.s.) 55
Severe endoscopic relapse; 56 at 3 months: clinical relapse:
4% vs 25%; at 1 year (p = 0.02, n.s. after 1 year
Severe endoscopic relapse; 57 at 3 months: 41 %vs 74%*;
at 12 months: 62% vs 94% (n.s.)
Significative decrease in the 63 number of bowel movements;
endoscopy: n.s.
CD, Crohn's disease; CDAI, Crohn's Disease Activity Index; MZ, metronidazole.
* p < 0 . 0 5
who underwent curative ileal resection and primary anastomosis were randomized within 1 week of surgery and received either metronidazole 20 mg/kg daily or placebo for 3 months [56]. At 12 weeks, severe ileal lesions could be detected at endoscopy in 13% of the patients in the metronidazole group vs 43% of the patients in the placebo group (p = 0.02).
The clinical recurrence was lower in the metronida- zole group at 1 year (4% vs 25%) but not later. Side- effects related to metronidazole occurred in 57%) of the patients. This trial showed that metronidazole can significantly decrease the recurrence of severe lesions but that tolerance did not allow long-term treatments, and this may be the reason why the therapeutic benefit over placebo vanished after a few months. In a second trial, Rutgeerts et al. [57] used ornidazole 1 g/day for 1 year, which was expected to be better tolerated than metronidazole. In an interim analysis (71 patients included), they reported that the risk of severe endoscopic recurrence was signifi- cantly decreased in the ornidazole group (Table 2).
Perineal disease
The efficacy of metronidazole in perineal CD has been assessed only in open series of patients. Bern- stein et al. [58] and subsequently Brandt et al. [59]
reported a decrease in symptoms in 19 patients out of 21 and an improvement of the anoperineal lesions in 18; the efficacy often needs a long delay as 15 improvements were observed after 2 months and three after 4 months. Thirteen patients relapsed when they subsequently tried to stop metronidazole. In this series, side-effects were reported in 50% of the patients, which occurred after a mean delay of 6 months of treatment. Jakobovits et al. [60] treated eight patients with anal fistula and reported a remission in four after a mean delay of 9 weeks;
however, all patients complained of side-effects.
McKee etal. [61] reported a sustained improvement
in seven patients out of 32, a short-term improve-
ment in 22, no effect in two, and side-effects leading
to early withdrawal of the drug in one patient.
Pouchitis
Metronidazole is recognized as an eflfective treat- ment for active chronic pouchitis [62]. This is, how- ever, still based only on open studies and only one randomized controlled trial [63]. In the randomized controlled trial, 13 patients who had undergone restorative proctocolectomy for U C and who suffered from pouchitis were studied. The study followed a cross-over design. Patients were rando- mized to receive either metronidazole 400 mg three times daily or placebo for 2 weeks. They then stopped the drug for a 1-week washout period and, if pouchitis was still present or recurred, received the other treatment for another 2 weeks. The primary efficacy criterion was stool frequency. Metronidazole reduced stool frequency by a mean of three bowel m o v e m e n t s / d a y while placebo had no effect (/?<0.05). However, metronidazole did not signifi- cantly change the endoscopic score for mucosal inflammation, the histological grade of inflamma- tion, the general score of well-being, or the appear- ance of blood in stools. In large open series, response to metronidazole was 54-78% [64, 65]. Nygaard etal [66] treated 11 patients with chronic pouchitis with low doses of metronidazole in enemas. The dose was 80 mg in 50 ml twice daily for acute treatment but lower doses (40 mg/day) were used for long-term treatments. The tolerance was good, and allowed long-term treatments. Clinical symptoms improved in all patients although endoscopic lesions were not changed. Three patients with chronic pouchitis remained well for 6 months, 3 years and 4 years t a k i n g 40 mg m e t r o n i d a z o l e / d a y while the symptoms recurred after cessation of therapy.
Toxicity
Side-effects of nitroimidazole drugs are frequent and often limit their long-term use. They include nausea, metallic taste, glossitis, urticaria, vaginal and u r e t h r a l b u r n i n g , d a r k u r i n e , n e u t r o p e n i a , disulfiram-like reaction in case of alcohol intake and peripheral neuropathy [44, 67]. The neuropathy occurs in up to 50% of the patients treated for 6 months. It usually resolves after treatment cessation but may persist for years [67]. Metronidazole is mutagenic for some bacteria and carcinogenic in mice after long-term use [68]. Although some authors reported cases of cancers in young subjects who had been treated with metronidazole [69], epidemiologic studies found no increase in the inci-
dence of cancers after 7 years of follow-up [70]. The use of metronidazole in pregnant women for 7-10 days has been shown to be safe but the safety of longer treatments is unknown [71].
Ciprofloxacin
Ciprofloxacin is a quinolone and is effective against enteric pathogens and most Gram-negative Entero- b a c t e r i a c e a e . Q u i n o l o n e s also seem to have i m m u n o m o d u l a t o r y p r o p e r t i e s such as the inhibition of IL-1 production by macrophages [72].
Efficacy in IBD
Several trials including three randomized controlled studies suggested that ciprofloxacin may have a mild clinical efficacy in CD, but this has not been proven against placebo [55, 73, 74]. Prantera et al. reported that the efficacy of a combination of metronidazole and ciprofloxacin to induce remission of CD was about 45%) vs 63% for steroids [55]. Colombel et al.
compared the efficacy of ciprofloxacin (1 g/day) and mesalazine (4 g/day) for 6 weeks in a randomized controlled trial including 40 patients with mild to moderate episodes of CD [74]. Remission was observed in 56%o of the patients treated with cipro- floxacin vs 55% in the control group (n.s.). Addition- ally, the mean C-reactive protein level at the end of the trial was lower in the group receiving ciproflox- acin (9 ± 11 vs 17 ± 17).
Open series suggested that ciprofloxacin is effec- tive in the treatment of anoperineal lesions of CD. In a report, six out of eight patients with fistulas improved when they received ciprofloxacin for 3-12 months [73]. Solomon et al. treated 14 patients with severe anoperineal lesions due to CD using a combi- nation of ciprofloxacin (1-1.5 g/day) and metronida- zole [75]. At 12 weeks, three patients were completely healed and nine had improved. Greenbloom et al.
[76] also used a combination of ciprofloxacin and metronidazole in 72 patients with active CD. Treat- ment was continued for a mean of 10 weeks, and 76%) of the patients showed clinical response. In a retro- spective study, Prantera et al. [77] evaluated that ciprofloxacin had been helpful in 69%) of their patients with active CD.
Turunen et al. [78] performed a double-blind
randomized controlled trial in 83 patients with acute
moderate to severe UC who were considered to be
poor responders to conventional therapy. Patients
were treated with prednisone (with decreasing dose) plus mesalazine plus either ciprofloxacin (500-750 mg twice a day) or placebo for 6 months. Both treatments were equally effective during the first 3 months; however, after 6 months treatment failure was less frequent in the ciprofloxacin group (21% vs 44%, p = 0.02), although endoscopic and histologic findings were not different. It is at present difficult to draw firm conclusions on the efficacy of cipro- floxacin in UC from this single study, and the study design has been criticized, especially because of the associated treatments [79]. Confirmatory studies are needed.
Hurst et al. [64] reported that eight out of 11 patients with pouchitis who had not tolerated or responded to metronidazole responded to cipro- floxacin. In an open trial, Gionchetti et al. [80]
treated 18 patients suffering from refractory pouchi- tis with rifaximin (a broad-spectrum non-absorbable antibiotic) plus ciproffoxacin for 15 days; 16/18 either improved (n = 10) or went into remission (n = 6).
Side-effects
Ciprofloxacin appears to be safe for short-term or long-term use in IBD patients [81]. The most common side-effects include nausea, vomiting and skin reactions. Tendinitis and rupture, usually of the Achilles tendon, are very rare, but clinicians should be aware that steroids are predisposing factors [81].
All new quinolones including ciproffoxacin are contraindicated for use in pregnant women, based
on the arthropathogenicity of these medications observed in immature animals [82].
Antimycobacterial therapy
Based on the sporadic finding of mycobacteria, especially Mycobacterium paratuberculosis, in tissue from patients with CD, several authors have tried various antituberculous drugs to treat patients. There have been anecdotal reports of remissions of CD after antimycobacterial therapy [83-85]; however, the randomized controlled trials and open studies have yielded less convincing results (Table 3).
Elliott et al. [86] performed a double-blind placebo-controlled study evaluating sulfadoxine, 1.5 g, plus pyrimethamine, 75 mg, once weekly in patients with steroid-resistant active CD. Sulfadox- ine was chosen because this group of investigators had isolated a sulfadoxine-sensitive Mycobacterium kansaii species from tissue from a patient with CD.
There was no diff'erence in outcome between therapy with this antibiotic regimen versus placebo. Shaffer et al. [87] evaluated rifampin, 10 mg/kg per day, plus ethambutol, 15 mg/kg per day, as primary therapy for CD in a double-blind, placebo-controlled cross- over study. They found no significant diff'erence between rifampin plus ethambutol therapy com- pared to placebo in terms of clinical status and CDAI levels. Twenty-seven patients were enrolled but only 14 completed the study. Ten of the 14 patients completing the trial had relapses, five of whom were on active drug. Three of the four patients who with- drew from the trial because they required surgery
Table 3. Randomized placebo-controlled trials with antimycobacterial therapy in Crohn's disease
Drugs
Sulfadoxine + pyrimethamine Rifampicin + ethambuthol (crossover) Rifabutin
Clofazimin
Rifampicin + ethambuthol + isoniazid
Rifampicin + ethambuthol + clofazimin + dapsone Clarithromycin (crossover)
Clarithromycin + ethambuthol
No. of patients
51 27 24 49 130 40 15 31
Duration of treatment
12 months 12 months 6 months 12 months 24 months 9 months 3 months 3 months
Remission (antibiotic vs placebo)
No effect No effect No effect No effect No effect 72 % vs 33 %*
71.4%vs12.5%*
No effect
Ref.
86 87 94 88 89,90 91 96 97
*p<0.05
were using active drug. Afdhal et al. [88] reported that clofazimin (which is bactericidal against Myco- bacterium leprae, Mycobacterium avium and Myco- bacterium ulcerans) in a dose of 100 mg/day for 8 months was not more effective than the placebo. In the largest trial [89, 90], 130 subjects were rando- mized double-blind to receive for up to 2 years either rifampicin, isoniazid, and ethambutol or identical placebos. The effect of the treatment on the course of the disease was assessed in a number of ways including the Harvey-Bradshaw index, the number of episodes of surgery required, radiological change, the total steroid dosage during the study, and the number of days of which prednisone was above 10 mg. Efficacy was evaluated after 2 years, and more recently after 5 years in 81% of the patients. No benefit was observed in the treated group. During the study period, 17 patients in the antituberculous group had experienced adverse events (vs three in the placebo group), and the treatment had to be stopped because of adverse events in nine. Two subsequent randomized controlled trials have been more opti- mistic but remain preliminary. Prantera et al. [91]
treated, for 9 months, 40 corticodependent patients with active CD with rifampicin, ethambutol, clofazi- min and dapsone or placebos. After 9 months of treatment, 4/19 patients treated with the antibiotics vs 11 /17 in the placebo group still needed corticos- teroids (p = 0.03); eight patients had anemia related to dapsone therapy, and two of them had to stop the treatment because of this adverse event. Borgaonkar et al. performed a meta-analysis of the trials using antituberculous agents to treat CD [92], and calcu- lated that the pooled odds ratio for maintenance of remission in treatment vs control for all studies was 1.1 (n.s.). However, they considered that the studies could be divided into two subgroups based upon the method by which corticosteroids were used to induce remission. The studies by Afdhal et al. [88] and by Prantera et al. [91] used corticosteroids with subse- quent tapering while the other did not. Pooling of these two trials yielded an odds ratio for mainte- nance of remission in treatment vs control of 3.37 (95% confidence interval 1.38-8.24). The authors concluded that this regimen might be effective.
Mycobacterium paratuberculosis is generally resis- tant to standard antituberculous drugs, and infec- tions are difficult to eradicate. This may explain the absence of efficacy of usual antituberculous agents in CD and stimulated pursuit of drugs active against this microorganism, especially rifabutin, clarithro- mycin, and azithromycin [93]. Rifabutin alone was
compared to placebo by Basilisco et al. [94] in 24 subjects treated for 6 months; the study was inter- rupted because of the occurrence of allergies, but no difference in efficacy was observed between the two groups. Gui etal. [95] performed an open study in 52 patients with severe CD who received clarithromycin or azithromycin together with rifabutin for a mean of 18 months. A reduction of CDAI at 6 and 24 months and of C-reactive protein was observed, and only two out of 19 patients who were steroid-dependent at the beginning of the study continued to require steroids.
Graham et al. [96] treated in a crossover study 15 patients with CD with 1 g/day clarithromycin or placebo for 3 months. They reported that remission could be achieved by about 40%o of the patients with severe disease [96]. However, more recently, the same group reported that a combination of clarithromycin and ethambutol for 3 months was not more effective than placebo in 31 patients followed 1 year [97].
Other antibiotics
Moss et al. [98] evaluated in an open fashion the effects of five antibiotics (ampicillin, tetracyclin, clindamycin, cephalotin, and erythromycin) in 44 patients with CD. Criteria used for patient selection or for antibiotic selection were unclear. The authors reported that, by 6 months, 41 of 44 patients sig- nificantly improved. Of 35 patients evaluated radio- graphically, 15 patients showed either no improve- ment or deteriorated. Savidge [99] reported on the use of trimethoprim-sulfamethoxazole in treating eight patients with active UC in an open fashion.
Two patients failed therapy, five patients achieved complete clinical remission (all within 1 week), and one patient had some improvement. The treatment duration was from 2 to 26 weeks. Ambrose et al. [53]
reported on four groups of patients with acutely active CD randomized to either placebo therapy, trimethoprim-sulfamethoxazole plus placebo, metronidazole plus placebo, or trimethoprim-sulfa- methoxazole plus metronidazole. This study sug- gested no benefit of any antibiotic combination compared to placebo. Saverymuttu et al. [100]
reported a randomized trial comparing predniso-
lone, 0.5 mg/kg per day, plus a normal diet to an
elemental diet plus framycetin, colistin, and nystatin
(three non-absorbable antibiotics) in 32 patients with
apparently active CD. The premise of the study was
that intestinal decontamination lowers the antigenic
load and improves disease activity. There was a
similar rate of improvement in both groups based on radiolabeled fecal leukocyte excretion and changes in C D A I . However, statistical analysis was not included in this report. To provide intestinal decon- tamination, Burke et al. [101] treated patients with active UC with 7 days of oral tobramycin adjunc- tively to corticosteroids and sulfasalazine. Com- pared with placebo, the group receiving tobramycin had a greater remission rate. The concurrent use of the standard therapies, however, precludes a clear conclusion as to what effect the tobramycin had.
Dickinson et al. [102] reported a double-blind, placebo-controlled study of 7 days with oral vanco- mycin in acute exacerbation of idiopathic colitis. The rationale for using vancomycin was to eradicate Clostridium difficile, which had been implicated as an exacerbating factor in some patients with idio- pathic colitis, and to treat the overgrowth of Gram- positive flora in the bowels of UC patients. Forty patients (33 with UC and seven with CD) requiring hospitalization were randomized to vancomycin, 500 mg every 6 hours, or placebo. There was no signifi- cant difference in the outcome between vancomycin- and placebo-treated patients. Interestingly, no patients had C difficile cultured from their stool.
This report showed that vancomycin was of no benefit and that C difficile is not an important factor in most patients with exacerbation of idiopathic colitis. Other studies have also found that only four of 44 patients with UC [103] and two of 169 patients with IBD (neither of whom had active disease [104]) were found to have C difficile toxin in their stool.
Dapsone, which is used to treat leprosy, was used in six patients with active CD. Within 3 months, four of six patients achieved complete remission [105].
Prantera et al. [106] treated a patient with a 12-year history of Crohn's ileocolitis, during a flare of Crohn's proctitis, with dapsone, 75 mg/day. The proctitis was dramatically improved within 2 weeks, and complete remission was achieved, including healing of all known intestinal disease, during 12 months of therapy. The same author later performed a case study of five patients treated with dapsone;
two improved and one went into remission [107]. He later performed a randomized controlled study with four antimycobacterial drugs including dapsone [91], and reported that it was effective (see above).
Rifaximin
Gionchetti et al. [108] performed a 10-day double- blind controlled trial comparing the efficacy of rifax- imin and placebo in 28 patients with severe refrac- tory UC; 64% of the patients receiving rifaximin improved vs 42% in the control group (n.s.). Rifax- imin resulted in a significant reduction in stool frequency, rectal bleeding, and endoscopic score compared to placebo. This therapeutic response was surprisingly high, even in the control group, if one considers that the patients had severe colitis. Further studies are thus needed to confirm this report. In another study the same authors reported that a combination of rifaximin plus ciprofloxacin was helpful in subjects with refractory pouchitis [80].
In a 5-day randomized controlled study, Casellas etal. compared the eflPicacy of amoxicillin-clavulanic acid, methylprednisolone or a combination of both in 30 patients with active UC [ 109]. The release of IL- 8 by the inflamed intestinal mucosa was decreased by the antibiotic.
Probiotics
Rationale
Probiotics are live microbial food ingredients that alter the enteric microflora and have a beneficial effect on health [5, 6]. They include bacteria such as lactobacilli, bifidobacteria, Escherichia coli, etc., or yeast such as Saccharomyces [110]. The effects can be either direct effects due to the expression in vivo of intrinsic metabolic properties of the microorganism or to some part of its architecture, or indirect effects due to modifications of the endogenous flora or of the immune system [110]. The tolerance is usually excel- lent, although several cases of infection have been published [110-113]. Although the mechanisms involved in many effects are often not understood, the survival of the strains in the gastrointestinal tract, and in some cases its adhesion to the mucosa, seem important pharmacokinetic factors [114, 115].
Several studies have shown interesting effects of probiotics in animals models of IBD [4, 19, 37, 116-
118]. Intracolonic administration of Lactobacillus reuteri R2LC to rats with acetic acid-induced colitis significantly decreased the disease while Lactobacil- lus HLC was ineffective [116]. Administration of L.
reuteri R2LC and L. plantarum DSM 9843 to rats
with methotrexate-induced enterocolitis reduced
intestinal permeability, bacterial translocation and
plasma endotoxin levels compared with rats with enterocolitis and no treatment [117]. A strain of L.
salivarius (ssp salivarius UCC118) diminished the rate of progression from inflammation through dys- plasia to colon cancer in the IL-10-deficient model, when compared to non-probiotic-fed animals [118].
Clinical trials
Many of the clinical trials using probiotics in IBD have been published only in preliminary abstract form, but information is rapidly increasing.
Ulcerative colitis
McCann et al. [119] were the first to suggest, from their experience in open treatment of 10 subjects, that long-term administration of Escherichia coli strain Nissle 1917, and other bacterial strains includ- ing Lactobacillus acidophilus, and Bifidobacterium bifidum may help maintaining remission in UC. Two randomized controlled trials were then performed comparing the efficacy of this strain to mesalazine for the maintenance of remission in UC [120, 121].
Kruis etal. [120] included, in a 12-week double-blind double dummy study, 120 patients with inactive UC.
Half of them received 1.5 g/day of mesalazine, and the other half received 200 mg/day of mutaflor (Ardeypharm GmbH, Herdecke, Germany) which contains 25 x 10^ viable E. coli bacteria per 100 mg.
After 12 weeks, 11.3% of the subjects receiving mesalazine and 16% of those receiving E. coli had relapsed, and this diflFerence was not significant.
Rembacken et al. published a second trial in which E. coli strain Nissle 1917 was also compared to mesalazine in 116 patients with active UC [121].
Patients with active colitis were randomized to receive 2.4 g/day of mesalazine or 200 mg/day of mutaflor in enteric capsules, which release the E. coli in the terminal ileum. All patients were also given a 1-week course of oral gentamicin 240 mg/day to suppress their native E. coli flora, and either rectal or oral steroids according to the extent of their disease. Remission was attained in 75% of the patients in the mesalazine group vs 68%o in the E. coli group (difference n.s.). When remission was reached, the steroids were tapered and stopped over 4 months, and the dose of mesalazine was reduced to 1.2 g/day.
Relapse occurred in 73%) of the patients in the mesalazine group vs 67% in the E. coli group (differ- ence U.S.). These two trials demonstrate that the tolerance was good, but can only suggest that E. coli
strain Nissle 1917 may be helpful in UC. Indeed, none of the trials compared this strain to placebo, the statistical power of the first study was low, as the follow-up was short, and as the efficacy of the mesalazine second study was rather low. Ishikawa et al. [122] gave to 21 subjects suffering from UC 100 ml/day of fermented milk for 1 year. Eleven received B. bifidum YIT 4007, B. breve YIT 4065, and L.
acidophilus YIT 0168 in the milk and the other 10 did not. They reported that the probiotic mixture was well tolerated and that there were less relapses in the group receiving (27%o) than in the control group (90%). The bifidobacteria were recovered from the feces of the subjects.
Pouchitis
Pouchitis has been shown to be associated with reduced counts of bifidobacteria and lactobacilli, suggesting that it may result from an imbalance of the endogenous flora [123]. Gionchetti et al. per- formed a randomized double-blind study comparing the effect of a probiotic mixture: V S L # 3 and placebo to prevent recurrence of chronic relapsing pouchitis [38]. Eligible patients had chronic relapsing pouchitis defined as at least three relapses per year. When they entered the study they were in remission, and no other treatment was allowed. Remission had been induced by 1 month of antibiotic treatment with ciprofloxacin and rifabutin. V S L # 3 (CSL, Milan, Italy) contains 300 billion viable lyophilized bacteria per gram of four strains of lactobacilli (L. casei, L.
plantarum, L. acidophilus, L. delbrueckii subsp. bul- garicus), three strains of bifidobacteria (B. longum, B.
breve, B. infantis), and one strain of Streptococcus salivarius subsp. thermophilus. The treatment (6 g/
day) was given for 9 months. Forty patients entered the study. A relapse occurred in 15% of the subjects in the V S L # 3 group vs 100%o in the placebo group (/?<0.001). No side-eff'ects were observed. The mechanism of this therapeutic effect is not yet estab- lished; however, the authors showed that the fecal concentration of lactobacilli, bifidobacteria and streptococci increased in the V S L # 3 group and, in another study, that continuous treatment with V S L # 3 increases the tissue levels of IL-10 in patients with chronic pouchitis [124]. The same authors studied the effect of V S L # 3 to prevent pouchitis.
Forty patients who had colectomy and ileo-pouch-
anal anastomosis for UC were randomized to receive
either V S L # 3 (3 g/day) or placebo immediately after
ileostomy closure and for 1 year. Pouchitis occurred
in 10%o of the patients in the V S L # 3 group vs 40% of
those in the placebo group (p < 0.01). Friedman et al.
treated 10 patients with pouchitis with a mixture of Lactobacillus rhamnosus strain G G and fructro- oligosaccharides for 1 month and reported that this short term treatment was effective in all cases [125].
Crohn's disease
Several trials suggested that Saccharomyces boular- dii, a probiotic yeast [6, 126] has some efficacy in the treatment of CD [127, 128]. Plein and Hotz [127]
performed a pilot double-blind controlled study testing the efficacy of S. boulardii on symptoms of CD. Twenty patients with active moderate CD were randomized to receive for 7 weeks, together with the standard treatment, either S. boulardii or a placebo.
A significant reduction in the frequency of bowel movements and in disease activity was observed in the group receiving S. boulardii but not in the placebo group. Guslandi et ai [128] treated 32 patients with CD in clinical remission either with 1 g/day of S.
boulardii plus mesalazine 2 g/day or mesalazine 3 g/
day in a double-blind randomized study. A clinical relapse was observed less frequently in the group who received the probiotic (1/16 at 1 year) than in the mesalazine group (6/16,/;<0.05). In an open study a
10-day administration of Lactobacillus GG to 14 children with active or inactive CD resulted in an increase in IgA-secreting cells to p-lactoglobulin and casein, which indicates an interaction between the probiotic and the local immune system [129]. The lactobacillus did not influence the disease activity;
however, the study group was too small and the study duration was too short to assess accurately a clinical effect [129].
Campieri et al. compared the efficacy of a combi- nation of rifaximin 1.8 g/day for 3 months followed by V S L # 3 probiotic therapy vs mesalazine 4 g/day in the prevention of postoperative recurrence of CD [130]. Forty patients were randomized; after 1 year 20% of the patients treated with the probiotic had a severe endoscopic relapse vs 40% of the patients treated with mesalazine.
Malchow treated in a double-blind controlled pilot study 28 subjects suffering from CD of the colon with E. coli strain Nissle 1917 or placebo [131]. The probiotic was well tolerated, and the rate of relapse was lower in the probiotic group (33%) than in the placebo group (63%).
Conclusion
The notion that IBD might have an infectious etiol- ogy has recurred over the years. Part of the appeal in finding an infectious agent is that simple and possibly curative therapy could be offered to patients. How- ever, convincing evidence for a role for viruses, bacteria, or mycobacteria in the etiopathogenesis of these diseases is lacking. There are no convincing data supporting the use of antimicrobial agents as primary therapy in IBD. An exception may be metronidazole in CD. Despite the lack of rando- mized, controlled trials of metronidazole for perineal CD, the open data available and general clinical experience are convincing. The role of metronidazole in other clinical forms of CD is less clear. Well- designed studies have been sparse, and many trials have been inadequately powered or methodologi- cally flawed. The first trials with probiotics are encouraging but much work is required before they can be recommended for routine use. The properties of the constituents of probiotic preparations need clarification and mechanistic studies are needed.
Most importantly, for both probiotic and antibiotic strategies, the most urgent requirement is an improved understanding of the normal flora and its interaction with the host in health and disease.
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