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Are probiotics useful in Helicobacter pylori eradication?

Helicobacter pylori (H. pylori) is considered an etiologic factor for the development of peptic ulcer disease, gastric adenocarcinoma, and MALT lymphoma. Therapeutic schemes to eradicate the bacteria are based on double antibiotic therapy and proton pump inhibitor. Despite many therapeutic improvements in H. pylori eradication treatment, it is still associated with high infection rate also in developed countries. Bacterial resistance and adverse events occurrence are among most frequent causes for anti- H. pylori treatment failure. Several studies have reported that certain probiotic strains can exhibit inhibitory activity against H. pylori bacteria. In addition, some probiotic strains can reduce the occurrence of side effects due to antibiotic therapy and consequently increase the H. pylori eradication rate. The results of the prospective double-blind placebo-controlled studies suggest that specific probiotics, such as S. boulardii and L. johnsonni La1 probably can diminish the bacterial load, but not completely eradicate the H. pylori bacteria. Furthermore, it seems that supplementation with S. boulardii is a useful concomitant therapy in the standard H. pylori eradication treatment protocol and most probably increases eradication rate. L. reuteri is equally effective, but more positive studies are needed. Finally, probiotic strains, such as S. boulardii, L. reuteri and L. GG, decrease gastrointestinal antibiotic associated adverse effects.


HELICOBACTER PYLORI
Helicobacter pylori (H. pylori) is a Gram-negative micro-organism. From the original discovery of genus Helicobacter, more than 20 species have now been formally defined [1] . The gastric mucosa is well protected against bacterial infection. After ingestion H. pylori must survive the bactericidal activity of the gastric lumen and enter the mucus layer. H. pylori is highly adapted to special conditions in the stomach. It possess flagella, which enable colonization of the gastric epithelium [2] . Moreover, the bacteria produce enzyme urease, which hydrolyzes urea into carbon dioxide and ammonia and elevates pH in the surroundings of the bacteria. The enzyme activity is highest at low pH [3] . The H. pylori bacteria usually causes chronic infection due to a complex balance between host factors and virulence bacterial factors. Among several bacterial factors one of the main factors, which drive Th17 inflammation, represents the secreted peptidyl prolyl cis, transisomerase [4] . In the colonization and chronic infection the adherence of the bacteria to the gastric epithelium is also very important. Lipopolysaccharide is a ) of H. pylori lipopolysaccharide are also expressed in the epithelial cells of gastric mucosa, therefore they probably play an important role in adherence to gastric cells [5] . Around 5% of the H. pylori genome encodes outer membrane proteins (OMP). OMP are adhesins on the surface of the bacteria, which promote binding to the epithelial cells in the stomach. The major OMP is the blood group antigen-binding adhesion A (BabA), which mediates the binding of H. pylori to the fucosylated Le b blood group antigen. It also mediates binding to salivary mucin MUC5B, a proline-rich glycoprotein, and to the glycoprotein gp-340 [6] . The second most important OMP is the sialic acid-binding adhesion (SabA) [7] . SabA mediates the binding of the bacteria to the sialyldimeric-Le x , to salivary mucin MUC5B, and to salivary glycoproteins like MUC7 and zinc-glycoprotein [8] . In gastric colonisation are also involved other OMPs like AlpA, AlpB, HopZ and HomB. Tight binding of bacteria to gastric epithelial cells is enabled therefore also with BabA2 and Saba adhesins. The H. pylori is very closely associated with extracellular MUC5AC and epithelial cells that produce MUC5AC, therefore MUC5AC plays a role in the adherence of H. pylori to the gastric mucosa. The important receptor for bacteria is the Le b structure present in the normal gastric tissue and MUC5AC is the most important carrier of Le b , with the attachment being made through BabA [9] . H. pylori infection is still one of the most common bacterial infections all over the world. H. pylori infection is very common in Eastern Europe, Africa and most Asian countries [10] . In developed parts of the world the prevalence has lowered and is below 10% in children and below 30% in adults [11] . Twenty percent of infected individuals develop symptomatic gastritis, gastric or duodenal ulcer, gastric adenocarcinoma, and non-Hodgkin's gastric lymphoma [12] . H. pylori is also associated with irondeficiency anemia, idiopathic thrombocytopenic purpura and vitamin B12 deficiency [13] . Several bacterial, host and environmental factors have been studied to determine clinical outcome of H. pylori infection. Among bacterial factors, virulence genes are most important, and the severity of H. pylori related disease correlates with the presence of cagA, vacA s1m1 and babA2 genotypes [14,15] . Chronic active gastritis can proceed to precancerous lesions such as gastric mucosal atrophy and intestinal metaplasia, and finally to the development of gastric adenocarcinoma. The results of recent studies support the beneficial effect of H. pylori eradication on preventing gastric cancer as well as on the regression of mucosal atrophy and intestinal metaplasia of the gastric mucosa [16] . Therefore, precancerous gastric lesions demand rapid detection of H. pylori and eradication of bacteria.
H. pylori is suggested to have also beneficial properties. Several studies and meta-analysis showed an inverse relationship between H. pylori infection and asthma occurrence [17,18] . The association was stronger for children than adults, but more prospective studies are needed to confirm the above mention relationship. In addition, H. pylori infection probably decreases the prevalence of obesity in children [19] . The association between H. pylori infection and gastroesophageal reflux disease is still unclear. Although it has previously been suggested that H. pylori eradication may cause reflux disease, the existence of such association was not confirmed recently [20] . The standard eradication therapy consists of two antibiotics and a proton pump inhibitor lasting for 7-14 d. The percentage of treatment failures is rising and major cause for this is bacterial resistance to frequently prescribed antibiotics. The frequent use of clarithromycin for respiratory tract infections has led to high H. pylori clarithromycin resistance rates [21] . Resistance to metronidazole has less clinical impact. Metronidazole resistance can be partially overcome by increasing the dose and treatment duration. The resistance of H. pylori to metronidazole has been reported between 30% and 40% [22] . The eradication levels using standard triple therapy is between 60% and 80%, the last being regarded as the minimal acceptable level according to the Maastricht guidelines [23] . Therefore, there is a great interest of developing new alternatives to eradication therapy, such as quadruple therapy or sequential therapy. Another possibility is to add the additional drug to standard therapy protocol. Several studies have examined the potential influence of probiotics as adjuncts to standard therapy on H. pylori eradication rate.
In addition, probiotics were studied to lower the frequency of side effects, because adverse events relating to H. pylori therapy are an important factor that influences compliance. The overall rate of adverse events was 53.3% in a multicentre study [24] . The most common adverse events reported are diarrhoea, nausea and vomiting, which have significant physical and social impacts, and it has been shown that side effects were significantly associated with decreased compliance and treatment failure [25] .

PROBIOTICS
The FAO/WHO definition of probiotics is that probiotics are live microorganisms which when administered in adequate amounts confer a health benefit on the host [26] . The most commonly used probiotics in humans are microorganisms belonging to genera Bififobacterium, Lactobacillus, Saccharomyces and Bacillus [27] . They are used as single species or multispecies preparation. The beneficial effects of probiotics seem to be strain-specific and dose-dependent. Clinical studies of probiotics in human are rapidly increasing. The beneficial effect of probiotics is already confirmed in diseases such as acute diarrhoea, antibiotic-associated diarrhoea, functional gastrointestinal disorders, inflammatory bowel disease, etc [28] . H. pylori infection is also a field in which particular interest in using probiotics is arising.

GASTRIC MICROBIOTA
Lactobacillus species are acid resistant and they are normally present in healthy gastric microbiota. Some strains can even adhere to gastric epithelial cells so they can stay longer than other bacteria in the stomach [29] . These has been confirmed in a study where it was possible to detect L. reuteri 55730 adhering to gastric epithelial cells of healthy volunteers a few hours after oral administration [30] . Elliott et al [31] has observed that in a rat with active gastric ulcer the local microbiota changed toward Gram-negative bacteria including E. coli while the Lactobacullus species almost disappeared. In the process of gastric mucosa healing the Lactobacillus population reappeared again and these process was accelerated by the oral lactulose administration. This study suggests that normal gastric microbiota participate in maintaining healthy mucosa. In addition, the oral intake of probiotics may reinforce protective functions in the stomach.

PROBIOTICS ANTIBACTERIAL ACTION
Probiotics can inhibit H. pylori by several immunological and non-immunological mechanisms. Probiotics are capable of modifying immunologic response of the host. Neutrophils, lymphocytes, plasma cells, and macrophages are involved in the inflammatory response to H. pylori. The consequences are increased levels of pro-inflammatory cytokines, such as IL-1β, IL-2, IL-6, IL-8 and tumor necrosis factor α in the gastric mucosa [32] . Probiotics like L. salivarius WB 1004 have in vitro reduced IL-8 secretion by gastric epithelial cells [33] . It looks like that at least in vitro L. acidophilus can improve H. pylori-induced gastric inflammation by inactivating the Smad7 and NFκB pathways [34] . Furthermore, Zhou et al [35] demonstrated that L. bulgaricus inhibited the activation of the TLR4 signaling pathway and IL-8 production induced by H. pylori lipopolysaccharide in SGC-7901 cells. The gastric inflammation can be controlled to some level by different strains of Lactobacilli through inactivating JAK2 through JAK-STAT pathways and through higher expression of SOCS protein family [36] . H. pylori also induce humoral response of gastric mucosa, which may contribute to gastric mucosal damage. Lactobacilli were able to increase the local IgA concentration and decrease specific anti H. pylori IgG antibodies in animal models [37,38] . Among non-immunological mechanisms probiotics are capable to influence on bacterial growth by secreting antibacterial substances such as lactic acid, short chain fatty acids, hydrogen peroxide and bactericins. The metabolites can diminish the number of spiral bacteria [39] . Lactic acid has probably an additional effect on H. pylori by lowering the pH and inhibiting the urease [40] . L. acidophilus CRL 639 secret an autolysin, a proteinaceous compound released after cell lysis, which has some antibacterial activity [41] . Substances, similar to isocoumarin antibiotics, are produced by B. subtilis and those can also kill H. pylori bacteria [42] . L. reuteri ATCC 55730 produce unique substance called reuterina which suppress growth of spiral bacteria [43] .
Mucins are high-molecular-weight glycoproteins that protect the gastric epithelium. The gastric surfacetype mucin is decreased in infected patients, because H. pylori suppresses the expression of MUC5AC and MUC1 genes [44] . It has been shown that L. plantarum strain 299v increases the expression of MUC2 gene and that L. rhamnosus GG stimulates the expression of MUC3 gene and the subsequent extracellular secretion of mucin by colon cell cultures [45,46] . Therefore, the ability of some probiotic strains to increase mucin production can protect the gastric mucosal barrier against the adherence of pathogenic bacteria such as H. pylori.
Adherence of H. pylori to the host tissue is of vital importance for colonization the gastric mucosa [47] . There are several proposed mechanisms of anti-adherence activity of probiotics. L. reuteri and W. confusa are capable of competing with H. pylori strains for adhesion sites. For example, L. reuteri strains, JCM 1081 and TM can lower the bacterial load in the gastric mucosa of children infected with H. pylori bacteria. Surprisingly, in 12% of children in the second group treated with S. boulardii and inulin H. pylori even the eradication was successful. The same author carried out randomized, double-blind study in 295 asymptomatic children infected with H. pylori [60] . The study compared eradication rates after 3 wk of therapy with (1) placebo juice/L. johnsonii La1; (2) cranberry juice /L. johnsonii La1; (3) placebo juice/heat-killed L. johnsonii La1; and (4) cranberry juice/heat-killed L. johnsonii La1. Except for the placebo group the eradication rates were above 14% in all tested groups, but didn't statistically significantly differ between each other. Cruchet et al [61] included 326 infected children in a similar study.
The children were divided into five groups. They were treated for one month either with live or heat-killed L. johnsonii La1 or either with live or inactivated L. paracasei ST11. The fifth group was the control group. Statistically significant changes in 13 C-urea breath test were observed only in the group of pediatric patients treated with live L. johnsonii La1 probiotics.
In conclusion, there are only a few studies evaluating the effect of probiotics as monotherapy on H. pylori eradication rate. The results of the studies suggest that specific probiotics, such as S. boulardii and L. johnsonni La1 probably diminish the bacterial load, but not completely eradicate the H. pylori bacteria.

Probiotics as adjuvant therapy in standard eradication protocols
Several systematic reviews and meta-analyses regarding effect of probiotics as adjuvant therapy to standard treatment of H. pylori infection have been published [62,63] . The authors suggested that probiotics supplementation in general probably increase the eradication rate and reduce the frequency of adverse effects due to double antibiotic therapy. However, the beneficial effects of probiotics seem to be strainspecific, thus, collecting data on different strains in meta-analysis may result in misleading conclusions. Regarding this, a better approach is to pool the data on single probiotics strain and perform a metaanalysis. Szajewska et al [64] recently published a systematic review to evaluate the effects of supplementations with S. boulardii to standard triple therapy protocol on H. pylori eradication rate. Five randomized controlled trials of good methodological quality involving 1307 patients were identified. Among them only 90 children were included. The daily dose of S. boulardii ranged from 500 mg to 1000 mg and the duration of the therapy was from 2-4 wk. From four trials the complete data on the eradication rates were available. In 80% of the included patients treated with S. boulardii along with triple therapy the eradication was confirmed by standard diagnostic tools. In the control group 9% lover absolute eradication rate 105, inhibit the binding of spiral bacteria to glycolipid receptors asialo-GMI and sulfatide [48] . In addition, Sakarya et al [49] demonstrated that S. boulardii contains neuraminidase activity, which removes surface α(2-3)linked sialic acid, the ligand for the sialic acid-binding H. pylori adhesion.

PYLORI TREATMENT
Eradication failure rate of more than 20% and high percentage of adverse effects of antibiotic therapy are main problems in standard eradication therapy protocols. Furthermore, lover compliance due to adverse events results in higher antibiotic resistance of bacterial strains. Studies published to date suggest that probiotics can have dual role in fighting against H. pylori infection. They diminish the frequency of gastrointestinal adverse events caused by antibiotic therapy and increase the eradication rate. The probiotics have been experimentally used as single therapy in eradication protocols or as therapeutic agent used concomitantly with standard eradication therapy.

Probiotics as single therapy in H. pylori treatment
The first in vitro positive results were published in 1989 [50] . Bhatia et al [50] discovered that H. pylori growth in vitro was inhibited, if L. acidophilus was present in the culture. Michetti et al [51] studied for the first time the effect of probiotics [L. acidophilus (La1)] on the H. pylori colonisation in humans. The study showed that the density of bacterial load diminishes in the probiotic group of asymptomatic patients, whereas complete eradication of H. pylori was not successful. Similarly, Wang et al [52] revealed that after intake of B. lactis Bb12 and L. acidophilus La5 in H. pylori infected adults a decrease in urea breath test values was detected. The bacterial load was evaluated by the semi-quantitative 13 C-urea breath test in subjects treated with L. johnsonii La1 [53] , L. brevis CD2 lyophilized bacteria [54] , B. bifidum BF-1 [55] , L. reuteri ATCC 55730 [43] , L. gasseri OLL 2716 [56] , and with multispecies probiotics such as a combination of L. reuteri DSM 17938 and L. reuteri ATCC PTA 6457 [57] or combination of L. rhamnosus GG, L. rhamnosus LC705, P. Freudenreichii JS and B. lactis Bb12 [58] .
Regardless of the used probiotics the authors reported significant decrease in 13 C-urea breath test values in the probiotic group of studied patients.
Gotteland et al [59] included 182 asymptomatic children infected with H. pylori and they were divided into four groups: standard triple therapy group, S. boulardii and inulin synbiotic group, L. acidophilus LB probiotic group, or control group without any therapy. Statistically significant decreases of urea breath test values were detected in two groups: the standard triple group and the S. boulardii inulin synbiotic group of children. The authors concluded that S. boulardii was detected (71%, 324 of the 455 patients). The authors concluded that compared with placebo or no intervention, S. boulardii given along with triple therapy significantly increased the eradication rate [relative risk (RR) = 1.13, 95%CI: 1.05-1.21]. The secondary endpoints of the same meta-analysis were also to determine the effect of S. boulardii on therapyrelated adverse effects. About 24.3% of patients experienced adverse effects in control group treated with triple therapy, compared to 12.9% of patients in probiotic group. Thus, the significant difference was found between the S. boulardi group and the control group with respect to the risk of overall adverse effects (five randomised control trials, n = 1305, RR = 0.46, 95%CI: 0.3-0.7). The authors analyse also the data of specific adverse effects. With regard to epigastric pain, taste disturbance/dry mouth, nausea or abdominal gas/bloating no significant difference was found between the studied groups. On the other hand, the risk of therapy related diarrhoea was statistically significantly lower in the probiotic group compared with the control group treated only with antibiotics and proton pump inhibitor (5.6% vs 12.2%, RR = 0.47, 95%CI: 0.32-0.69). The conclusions of the meta-analysis were that the concomitant use of S. boulardii with triple therapy moderately increases H. pylori eradication rates and decreases antibiotic related adverse effects, especially diarrhoea. However, more recent studies published by Song et al [65] and Zojaji et al [66] didn't confirm positive impact of S. boulardii on eradication rate. In Song's study 991 H. pylori infected patients were recruited. Patients in group A were treated only with two antibiotics and proton pump inhibitor, in group B S. boulardii was added for one month, and in group C the same regimen was used and in addition mucoprotective agent DA-9601 derived from Artemisia asiatica was concomitantly prescribed. Interestingly, the eradication rate was significantly higher in group B and C compared to group A only if intention to treat analysis was performed (P = 0.003), whereas the eradication rate difference of per protocol patients analysis was not significant. The conclusion was that supplementation with S. boulardi could be effective for improving eradication rates by reducing adverse effects thus helping completion of eradication therapy. Zojaji et al [66] included 160 adult patients. In the study protocol the probiotic S. boulardii was added to clarithromycin, amoxicillin and omeprazole for two weeks. The study showed that probiotics decrease the frequency of adverse events due to antibiotic therapy, but didn't increase the eradication rate of H. pylori. Tong et al [62] systematically evaluated the effectiveness of supplementation with different probiotics in increasing H. pylori eradication rates. In the publication they also made sub-analysis for different probiotics preparations. In eight of fourteen reported randomized trials single probiotics strain was used. In tree trials, Lactobacillus species was administered to the standard eradication therapy [67][68][69] . However, increased H. pylori eradication rate in Lactobacillus group was reported in only two studies published by Sýkora et al [69] and Canducci et al [67] . Overall in the tree studies the eradication rates were 70% in control group and 84% in probiotic supplemented group, which is a statistically significant difference (RR = 2.09, 95%CI: 1.28-3.41).
In addition, this meta-analysis revealed that adding probiotics to standard eradication protocols reduces adverse effects during treatment (25% vs 39%, RR = 0.44, 95%CI: 0.30-0.66). The positive impact on diarrhoea and taste disturbance was most prominent. The effectiveness of L. GG in children with H. pylori infection was studied in a trial from Poland [70] .
Of the 83 children tested, 34 children in a probiotics group received L. GG 10 9 twice daily for one week concomitantly with triple therapy. No significant difference in H. pylori eradication rates between the probiotic and the control group were found (RR = 0.98, 95%CI: 0.7-1.4). This result is in accordance with trials in adult population. Armuzzi et al [68] included 60 infected asymptomatic patients in a prospective study in which patients were treated with rabeprazole, clarithromycin tinidazole and L. GG or with the same triple therapy and placebo. Diarrhoea, nausea and taste disturbance were significantly reduced in the L. GG supplemented group (relative risk = 0.1, 95%CI: 0.1 ± 0.9; relative risk = 0.3, 95%CI: 0.1 ± 0.9; relative risk = 0.5, 95%CI: 0.2 ± 0.9, respectively). In another Italian study 85 asymptomatic adults were included, and the conclusion of the study was that L. GG supplementation to standard therapy beneficially affects treatment related adverse effects [71] . However, it seems that L. GG has no effect on eradication rates.
Demonstration that L. reuteri ATCC 55730 is able to colonize the stomach and duodenum prompted studies regarding the effect of this strain on H. pylori eradication rates and the frequency of side effects [30] . In a recent study conducted in Italy, Ojetti et al [72] recruited 90 patients in their study. L. reuteri supplementation was concomitantly used for 14 d with second line therapy receiving esomeprazole, levofloxacin and amoxicillin in patients infected with H. pylori. Probiotic supplementation increased the eradication rate in treated patients (group 1: 36/45, 80%; group 2: 28/45 62%; P < 0.05). In addition, the incidence of side effects associated with antibiotic therapy was also significantly lower in the probiotic group. This is in agreement with a trial that also evaluated the impact of L. reuteri ATCC 55730 (10 8 CFU for twenty days) as an adjuvant to 10-d sequential therapy in a group of 40 H. pylori infected children [73] . The Gastrointestinal Symptom Rating Score was lower in the group of children treated with L. reuteri (3.2 vs 5.8, P < 0.009). However, the use of L. reuteri as an adjunct to the sequential eradication therapy had no effect on eradication rates (17/20 vs 16/20). In 2009, Francavilla et al [43] compared the eradication rates and antibiotic adverse effects in 40 H. pylori positive subjects who were receiving for a month placebo or L. reuteri (10 8 CFU) once a day. At the end of the trial patients received standard 10-d sequential eradication therapy. Four week supplementation with L. reuteri was effective in lowering gastrointestinal adverse effects and also in reducing bacterial load, whereas no statistical significant difference in eradication rates was observed (88% vs 82%). Recently, the same group published results of the double-blind placebo-controlled randomized study using a combination of two L. reuteri strains (L. reuteri DSM 17938 and L. reuteri ATCC 55730) as an adjunct to triple eradication therapy [57] . L. reuteri DSM 17938 is a safe daughter strain of previously used L. reuteri ATCC 55730 in which two plasmids coding antibiotic resistance were removed. The new L. reuteri ATCC 55730 strain seems to have strong anti-inflammatory properties. A combination of two L. reuteri strains or placebo was given for two months concomitantly with one-week triple eradication therapy in a second part of the study. A significant reduction of adverse effects was shown in the group treated with eradication therapy and the combination of two L. reuteri strains, whereas H. pylori eradication rate was only slightly but not significantly increased in the same group of patients. In another study published by Emara et al [74] triple therapy supplemented with L. reuteri increased eradication rate by 8.6% and reduced the frequency of side effects. L. reuteri has a positive influence on gastrointestinal side effects especially diarrhoea, but conflicting reports regarding the impact of L. reuteri on H. pylori eradication rates demand further studies, especially because new strain combination was developed. The use of commercial yogurt containing B. animalis and L. casei combined with conventional triple therapy was investigated in two studies. Sheu et al [75] tested the efficacy of this yogurt as adjuvant to triple treatment. The difference in eradication rates of H. pylori infection in two groups was statistically significant in favour of probiotic group (73/80 vs 63/80, P < 0.05). Only patients supplemented with yogurt showed restoration of the percentage of Bifidobacterium in the stools at the end of the study to the level in the stools on enrolment. Goldman et al [76] was not able to confirm the important role of yogurt supplementation to standard triple therapy in a pediatric study. Contrary to Sheu study protocol, in which yogurt was administrated for five weeks, they continued with the probiotics treatment for three months. In spite of prolonged therapy they found no difference in H. pylori eradication rates among the yogurt and the placebo groups of patients (14/33 vs 13/32, P value is not significant). Effect of pre-treatment with L. gasseri OLL2716 on first-line eradication therapy was studied in a trial published by Deguchi et al [77] . About 229 infected patients were randomized into two groups, either one-week triple therapy (rabeprazole, clarithromycin, amoxicillin) or the same therapy with addition of probiotics. Overall eradication was significantly better in the studied probiotic group [intention to treat (P = 0.018)/per protocol (P = 0.041)], but more prospective studies are needed to evaluate the role of L. gasseri OLL2716 in the treatment in H. pylori infection.
Beneficial effects of adding fermented milk product containing L. casei DN-114 001 to the triple therapy on the eradication rate of H. pylori infection in children were showed in a multicentre study from the Check Republic [67] . Eighty-six symptomatic children infected with H. pylori were randomized either to receive the omeprazole, amoxicillin, clarithromycin or the same regimen with addition of probiotic for 7 d. Eradication rate was statistically significantly higher in the probiotic group (P = 0.0045). B. claussi have also been studied as a possible adjunct to standard therapy for H. pylori eradication, but the positive effect on eradication rate was not confirmed [78] . The characteristics of important studies where probiotics were used as adjuvant therapy to eradication treatment are presented in Table 1.

CONCLUSION
Chronic infection with H. pylori is a well-described risk factor for ulcer disease, gastric adenocarcinoma and MALT lymphoma. Therefore, eradication of H. pylori is a primary goal in symptomatic patients. The eradication rates achieved by classic triple therapy consisted from proton pump inhibitor and double antibiotic therapy are quite low and range from 60% to 80%, due to resistance to antibiotics and to moderate patient compliance. Antibiotic-associated gastrointestinal adverse events are the major cause for lower compliance. Therefore, probiotics were proposed as a useful adjunct to improve eradication rate and to decrease the frequency of adverse effects.
So far, mostly different types of Lactobacillus and S. boulardii were tested. The above-mentioned probiotics most probably decrease the bacterial load but don't eradicate H. pylori completely in the gastric mucosa, if they are used as monotherapy. On the contrary, some probiotics when added to classical triple therapy may increase eradication rates. A reasonable amount of evidence exists that supplementation with S. boulardii is a useful concomitant therapy in the standard H. pylori eradication treatment protocol and most probably increases the eradication rate. L. reuteri is also a good candidate for adjunctive therapy, but more positive studies are needed. The effect of other probiotics strains is less well described.