Point mutations in the glycosyltransferase domain of the pbp1a gene in amoxicillin-resistant Helicobacter pylori isolates

INTRODUCTION

Helicobacter pylori (H. pylori) eradication treatment includes a proton pump inhibitor and two antibiotics: amoxicillin and clarithromycin. The goal of that treatment is to eradicate the infection in at least 90% of the patients. Failure to eradicate the infection can have multiple causes, among which is the presence of point mutations in the antimicrobial target genes.

OBJECTIVE

To characterize the mutations present in the pbp1a gene and their possible association with resistance to amoxicillin in vitro.

METHODOLOGY

Susceptibility to amoxicillin was evaluated in 147 isolates of H. pylori from the Colombian municipality of Túquerres. PCR amplification and sequencing of the glycosyltransferase domain of the pbp1a gene were carried out on Túquerres isolates, and the association between mutations and resistance was evaluated.

RESULTS

A total of 5.4% (8/147) Túquerres isolates were resistant to amoxicillin in vitro. PCR amplification of the glycosyltransferase domain of the pbp1A gene was performed on 87.5% of the amoxicillin-resistant isolates in vitro, and in the DNA sequencing analysis, a total of 2 changes of amino acids from 3 DNA mutations that encoded the PBP1A-1 protein were observed.

CONCLUSION

The present study is the first report on pbp1a gene mutations in H. pylori isolates coming from a population in Túquerres. Mutations that have not been reported in previous studies were found.

[Immunotyping of lymphocytes in the gastric mucosa of patients infected by H. pylori in two regions with contrast in the risk of developing gastric cancer]

Helicobacter pylori (H. pylori) infection involves multiple factors internal and external to the host. Among the internal factors, the immune response plays a fundamental role in the process of antigen presentation, lymphocytic response and cytokine-mediated regulatory response that are directly as sociated with disease progression and prognosis.

OBJECTIVE

To compare the immune response in gas tric mucosa of H. pylori infected patients in two regions comparing the risk of developing gastric can cer.

PATIENTS AND METHOD

71 participants with symptoms of dyspepsia were included. The samples for biopsies were collected from different regions of the gastric mucosa; the identification of H. pylori was carried out by culture and polymerase chain reaction (PCR) of the ureA gene. For the characteri zation of the histopathological alterations and the immunophenotyping of lymphocytes, anti-human mouse monoclonal antibodies specific for each antigen were used: T lymphocytes: CD3 and CD8; B lymphocytes: CD20; Natural Killer Cells: CD56; Macrophages: CD68.

RESULTS

The prevalence of H. pylori was 83.1%, the predominant types of gastritis were chronic gastritis and multifocal atrophic gastritis with intestinal metaplasia (63.4% and 22.5%, respectively). The cellular response was charac terized mainly by polymorphonuclear lymphocytes and positive anti-CD8 reactivity both in stroma and epithelium.

CONCLUSIONS

Multifocal atrophic gastritis was more prevalent in the high-risk region for gastric cancer (GC) while non-atrophic gastritis and the expression of CD3 and CD8 antigens in the foveolar epithelium was higher in the low-risk region.

Punctual mutations in 23S rRNA gene of clarithromycin-resistant Helicobacter pylori in Colombian populations

AIM

To characterize punctual mutations in 23S rRNA gene of clarithromycin-resistant Helicobacter pylori (H. pylori) and determine their association with therapeutic failure.

METHODS

PCR products of 23S rRNA gene V domain of 74 H. pylori isolates; 34 resistant to clarithromycin (29 from a low-risk gastric cancer (GC) population: Tumaco-Colombia, and 5 from a high-risk population: Tuquerres-Colombia) and 40 from a susceptible population (28 from Tumaco and 12 from Túquerres) were sequenced using capillary electrophoresis. The concordance between mutations of V domain 23S rRNA gene of H. pylori and therapeutic failure was determined using the Kappa coefficient and McNemar’s test was performed to determine the relationship between H. pylori mutations and clarithromycin resistance.

RESULTS

23S rRNA gene from H. pylori was amplified in 56/74 isolates, of which 25 were resistant to clarithromycin (20 from Tumaco and 5 from Túquerres, respectively). In 17 resistant isolates (13 from Tumaco and 4 from Túquerres) the following mutations were found: A1593T1, A1653G2, C1770T, C1954T1, and G1827C in isolates from Tumaco, and A2144G from Túquerres. The mutations T2183C, A2144G and C2196T in H. pylori isolates resistant to clarithromycin from Colombia are reported for the first time. No association between the H. pylori mutations and in vitro clarithromycin resistance was found. However, therapeutic failure of eradication treatment was associated with mutations of 23S rRNA gene in clarithromycin-resistant H. pylori (κ = 0.71).

CONCLUSION

The therapeutic failure of eradication treatment in the two populations from Colombia was associated with mutations of the 23S rRNA gene in clarithromycin-resistant H. pylori.