Published online Apr 14, 2018. doi: 10.3748/wjg.v24.i14.1531
Peer-review started: January 22, 2018
First decision: February 6, 2018
Revised: February 25, 2018
Accepted: March 18, 2018
Article in press: March 18, 2018
Published online: April 14, 2018
Processing time: 81 Days and 4.3 Hours
Infection by Helicobacter pylori (H. pylori) is the leading risk factor for the development of gastric adenocarcinoma, especially in individuals infected with strains resistant to antibiotics used in primary treatment regimens. The eradication of H. pylori infection is a valid primary prevention strategy for gastric lesions, atrophy, and gastric cancer (GC). However, resistance of this microorganism to clarithromycin is associated with therapeutic failure and a major risk of GC in Colombia. Thus, although significant improvements in the efficacy of treatment regimens have been made, none of these regimens successfully eradicate the infection. A few studies have focused on the evaluation of clarithromycin-resistance mechanisms, particularly mutations of 23S rRNA gene of the infecting strains in Colombia, which are associated with treatment failure and early subsequent prevention of GC.
Taking into account that GC prevention programs are focused on the eradication of H. pylori, it is important to know the specific treatment regimens for each country seeking to apply this strategy. In Colombia, the efficacy of standard triple therapy which includes clarithromycin, amoxicillin, and a proton pump inhibitor is currently being questioned. However, there are insufficient multicenter studies suggesting alternative regimens and basic studies on antibiotic resistance mechanisms in H. pylori. Mutations in H. pylori 23S rRNA gene V domain were studied to evaluate in vitro resistance to clarithromycin. This study identified mutations not documented in the current literature, which although are not associated with in vitro resistance to clarithromycin, they are linked to the therapeutic failure of triple therapy. Punctual mutations in the Colombian strains could be useful in future studies focusing on diagnostic methods for antibiotic susceptibility and in the therapeutic efficacy of GC prevention schemes in Colombia.
In this study, the researchers characterized mutations in domain V of 23S rRNA gene in clarithromycin-resistant H. pylori and determined their association with therapeutic failure in a high-risk gastric cancer population from Tuquerres, Colombia, and in a low-risk gastric cancer population from Tumaco, Colombia. A very interesting basic study clearly showed that therapeutic failure of eradication treatment in the sampled Colombian populations was associated with mutations of 23S rRNA gene in clarithromycin-resistant H. pylori. Hopefully, these findings will help to further improve treatment success and may be applied in the future for the fast diagnosis of therapeutic failure. This study found no concordance between the presence of punctual mutations in H. pylori and in vitro resistance to clarithromycin and there was no association between the absence of mutations in the 23S rRNA gene and in vitro susceptibility to clarithromycin in both populations. These findings and the absence of mutations in 36% of the isolates resistant to in vitro clarithromycin may be explained by the occurrence of mutations outside the amplified region, a fragment located between positions 1585-2224. Among the changes associated with clarithromycin resistance, which are located outside this fragment, are A2223G, C2694A T2711C, T2288C, and T2289C, mutations that may explain the discrepancy between the presence of punctual mutations in the amplified region and in vitro resistance to clarithromycin
To achieve the objectives of this study, we used the capillary electrophoresis sequencing method of the amplified DNA fragments of the H. pylori 23S rRNA gene and the detection of its punctual mutations, which were concordant with the [13C]-Urea breath test. This method was used in a novel way to diagnose the therapeutic failure of anti-H. pylori treatment in vivo. The [13C]-Urea breath test was used during the follow-up period to evaluate the effectiveness of H. pylori treatments.
This study demonstrated that the resistant isolates from these two contrasting populations involved in the development of GC, mutations A2143G, A2142G, and A2142C, which are usually reported as the most frequent, were not found in the isolates evaluated. With regard to the design of tests, the changes A2144G, T2183C and C2196T found in these populations should be considered for use in fast-diagnostic methods of clarithromycin resistance in clinical practice.
These results are important in the definition of treatments for gastro-duodenal diseases caused by H. pylori. They suggest that the failure of anti-H. pylori treatment is mainly due to mutations in 23S rRNA gene V domain. The application of these findings could be complemented by studies on the genetics and virulence of the microorganism, as individuals with similar ancestry may not require anti-H. pylori treatment. In contrast individuals infected with strains of different evolutionary origins than their host, would benefit from additional studies on antibiotic susceptibility. These advances in basic studies tend to elucidate the African enigma, and indicate that human-H. pylori coevolution and virulence of the bacterium could explain the contrast in risk of disease observed in our study populations. These findings may contribute to the future identification of individuals at higher risk of GC and require antibiotic susceptibility studies prior to treatment of the infection and early GC prevention.
In this investigation, mutations A2144G, C2196T and T2183C were observed in 23S rRNA gene V domain of H. pylori resistant to clarithromycin and were associated with failure of eradication treatment. The mutations T2183C, A2144G and C2196T in 23S rRNA gene V domain are reported for the first time in clarithromycin-resistant isolates of H. pylori in Colombia. This study demonstrated that the therapeutic failure of H. pylori eradication treatment in high and low risk GC populations from Colombia was associated with mutations of the 23S rRNA gene of clarithromycin-resistant H. pylori. The sequencing method for the detection of punctual mutations of DNA amplified 23S rRNA gene fragments is proposed to predict therapeutic failure induced by clarithromycin-resistant H. pylori. This new knowledge allows us to propose the design of a rapid detection test for H. pylori resistance to clarithromycin where mutations A2144G, T2183C and C2196T should be considered and can be applied in clinical practice to predict therapeutic failure of anti-H. pylori treatment.
Following therapeutic failure, reinfection may occur in patients as well as medication with antagonistic drugs or others such as proton pump inhibitors, which allow the appearance of false positives. In this study, adherence to treatment and self-medication were taken into account during the follow-up period. Characterization of the mutations in the 23S rRNA gene in a larger number of Colombian populations is required, in order to confirm the mutations associated with clarithromycin resistance in H. pylori and to determine, from multicenter studies, the optimal treatment regimen in Colombia. The molecular analysis of 23S rRNA gene V domain of H. pylori and other candidate genes is required, in order predict therapeutic failure. It is possible to reproduce the method in future investigations using total DNA from gastric mucosa biopsies and validate the presence of mutations found in this study. The [13C]-Urea breath test is recommended during follow-up to evaluate the effectiveness of anti-H. pylori treatment.