In this prospective, randomized, double-blind, placebo-controlled study we failed to show a superiority of the probiotic treatment with PPI over placebo for eradicating HP after 28 days of treatment. There was a clear trend towards higher eradication of HP with sequential quadruple therapy in patients who were initially treated with ProGastria compared to placebo but the results did not reach the desired level of statistical significance.
According to our baseline data we noticed a discrepancy regarding the rate of positivity of the four diagnostic tests for HP infection. The highest positivity was observed for the stool antigen test and the lowest for the invasive histology and rapid urease tests. This is not surprising since HP shows patchy colonization and thus the appropriate region may not have been biopsied. More importantly, 10% of the patients from both placebo and on treatment groups were found positive for stool antigen test only. According to the Maastricht IV criteria from 2012 the diagnostic accuracy of the stool antigen test and 13C-UBT are equivalent provided that a monoclonal test is used [1
]. We used a validated laboratory which implemented a monoclonal antibody test especially for our analyses. Therefore, the apprehension of using inappropriate method with low diagnostic yield is eliminated. One possible explanation for these discrepancies is that some patients might not have fasted before the UBT and that we have not biopsied the colonized mucosal region. Other studies have also shown 10-40% false negative results for 13C-UBT which can be attributed to treatment with PPI and H2-antagonists [19
]. Since all of our patients had dyspeptic symptoms some of them may have not have shared that they were on such antisecretory treatment when they were tested. Therefore, we support the notion that at least two non-invasive tests or at least one non-invasive and one invasive test should be performed for adequate diagnosis of HP infection.
After 4 weeks of treatment with PPI+ProGastria or placebo 57.7% of the patients from the former group and 62.1% from the latter group had negative stool antigen test, which is statistically insignificant (p=0.75, Pearson`s correlation test). It seems that PPI+probiotics alone are unable to suppress H. pylori
according to our results. In contrast to our study Dore et al. proved eradication in 14.2% of patients treated with PPI+L. reuteri
but the treatment period was twice as long as ours [21
] while Navaro-Rodrigez T et al. found no increase in efficacy or decreases the adverse effects of the treatment with a probiotic compound compared to placebo [22
]. The issue of anti-HP activity of probiotics
is known and investigated in several in vitro
studies. This has been associated with competing with HP adhesins, stimulating mucin production, secreting bacteriocins, lactic, acetic acids and hydrogen peroxide which lead to decrease in HP urease activity, and interacting with epithelial cells and modulating anti-inflammatory cytokines [23
]. Nevertheless, eradication of HP has been rarely documented [23
]. Boyanova et al. have studied the effect of the well-known Bulgarian probiotics Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus on HP clinical isolates in vitro
and has proven their inhibitory properties but at low pH levels [25
]. Hence, withholding from adding a PPI to a treatment with probiotic is a possible way of increasing its effectiveness.
Another possible explanation for the lack of effectiveness of our treatment regime with ProGastria could be the early testing with stool antigen test–only one week after PPI discontinuation. According to the Maastricht IV guidelines PPI should be stopped for 2 weeks before testing by culture, histology, rapid urease test, 13C-UBT or stool test and this period allows repopulation of bacteria
in the stomach and restoring the positivity of previously negative tests [1
]. However, our results showed that only three patients (10%) resumed their stool antigen testf positivity during the 8 weeks of follow-up. This fact shows that one week is a suitable period for checking for the presence of HP after treatment discontinuation.
One drawback of our study is that we did not perform a UBT test on day 36. If the results from this highly sensitive test were concordant with the negative ones from the stool antigen test, this could mean that treatment successfully eradicated the HP infection. However, if the results were discordant (the negative stool antigen test was accompanied by positive UBT) this could mean that therapy effectively suppressed HP colonization of the gastric mucosa beyond the sensitivity of stool antigen test and that UBT would be more sensitive for following-up of treated patients.
The overall eradication rate of the sequential regimen among our studied population is 60% which is lower than expected. Data from two meta-analyses from Asia and Europe showed 87.6% and 84.3% eradication rate of sequential therapy, respectively [26
], and a single-center study from Turkey which neighbors Bulgaria reported a 71.4% rate of successful treatment [28
]. Patients` compliance is an important issue and should always be considered when treatment period exceeds one week and when the medications` switch relies on patients themselves. On the other hand, antibiotic resistance should not be underestimated. Primary clarithromycin resistance for Europe is reaching 17.6% [29
], for metronidazole it is 26%, while for amoxicillin is below 1% [30
]. Data from a national study analyzing the prevalence of multidrug-resistant H. pylori
in Bulgaria showed that resistance to clarithromycin, metronidazole and amoxicillin was 18.4%, 26.5% and 4.4%, respectively. Strains, resistant to both clarithromycin and metronidazole were found only in 8.0% of the cases [31
]. Therefore, the fact that the eradication rate of the sequential treatment regimen among our patients is lower than in Europe and Asia and closer to Turkey could be attributed to a local selection of a different bacterial strain that shows slightly higher resistance to clarithromycin and amoxicillin. Macrolides
are one of the most frequent antimicrobials used for treatment of upper respiratory tract infections in children and data show that sequential therapy is able to eradicate as much as 72.5% of strains resistant to clarithromycin [27
One of the main findings in our study was that compared to placebo more patients treated for 28 days with ProGastria achieved successful eradication with 10-day sequential therapy afterwards-33.3% vs 71.4%, respectively. Unfortunately, this did not reach statistical significance (p=0.17, Fisher`s exact test). Recent data, mostly from Asia, support our results. In their meta-analyses Zheng X et al. and Wang X et al. proved that lactobacillus
-containing probiotics as an adjunct improved eradication rates and reduced the total incidence of side effects of eradication schemes [32
]. This phenomenon could be explained by the durable colonization of L. reuteri
in the gastric mucosa and the exerted antagonism towards HP which probably aids the subsequent eradication. We believe that the lack of statistical significance of our results can be attributed to the low number of patients since only 20 persons were found positive for HP after 4 weeks of treatment with ProGastria and were prescribed eradication. Although the lack of evidence for effectiveness probiotics should be added to standard treatment regimes in order to reduce side effects and one of the main concerns is that long term use of both PPIs and antibiotics are associated with Cl. difficile colitis.
In conclusion, our study showed that treatment with PPI+probiotic is ineffective in eradicating H. pylori infection
in adults. A clear trend towards better eradication was observed if patients were treated with probiotic for four weeks prior to initiation of sequential 10-day regimen.