Absence of Helicobacter pylori high tetracycline resistant 16S rDNA AGA926-928TTC genotype in gastric biopsy specimens from dyspeptic patients of a city in the interior of São Paulo, Brazil

Pathological and Molecular Aspects to Improve Endoscopic Ultrasonography-Guided Fine-Needle Aspiration From Solid Pancreatic Lesions

Endoscopic ultrasonography-guided fine-needle aspiration (EUS-FNA) has been applied to pancreatic lesions since the 1990s, and its use is now widespread. Improvements in endoscopic devices and sampling techniques have resulted in excellent diagnostic ability for solid pancreatic lesions. However, clinical improvements alone are not responsible for it; pathological aspects have also played important roles. Rapid on-site evaluation minimizes endoscopic procedures, although its value at improving the diagnostic ratio is still debated. Diagnostic efficacy differs by sample preparations (direct smear, cytospin, liquid-based cytology, cell block, and biopsy) and by staining methods (Papanicoloau, Diff-Quik, hematoxylin-eosin, and Giemsa). Several immunocytochemistry protocols aid in diagnosing epithelial components with cytological atypia and in differentiating various tumor types. One cytopathology diagnostic system is telecytology, which uses transmitted digital images and enables real-time diagnosis of EUS-FNA samples by expert cytologists at remote locations. However, EUS-FNA samples are useful for more than just diagnoses, as molecular analysis of these samples allows the identification of prognostic markers, such as genetic alterations in K-ras and EGFR. Expression of drug-metabolizing enzymes, human equilibrative nucleoside transporter 1, correlates with the response to gemcitabine-based chemotherapy. These pathology efforts have enhanced the diagnostic efficacy of EUS-FNA, thereby leading to better outcomes for patients with pancreatic diseases.

Bacterial factors associated with Helicobacter pylori antibiotic resistance

Helicobacter pylori (H. pylori) infection is the most widespread chronic bacterial infection and is closely associated with many diseases. In recent years, however, H. pylori is becoming increasingly difficult to eradicate due to the growing antibiotic resistance. Among the reasons for the failed eradication, some factors of H. pylori itself play a main role. H. pylori can resist antibiotics by producing inactivating enzymes, changing the drug targets, preventing oxidation-reduction electron transfer, decreasing membrane permeability and activating efflux pump, changing bacterial metabolic state and so on. Elucidating the mechanism of antibiotic resistance will be helpful in developing new targeted drugs to effectively eradicate H. pylori. Here, we review the bacteria factors associated with H. pylori antibiotic resistance.

Role of Helicobacter pylori infection in gastric carcinogenesis: Current knowledge and future directions

Helicobacter pylori (H. pylori) plays a role in the pathogenesis of gastric cancer. The outcome of the infection depends on environmental factors and bacterial and host characteristics. Gastric carcinogenesis is a multistep process that is reversible in the early phase of mucosal damage, but the exact point of no return has not been identified. Therefore, two main therapeutic strategies could reduce gastric cancer incidence: (1) eradication of the already present infection; and (2) immunization (prior to or during the course of the infection). The success of a gastric cancer prevention strategy depends on timing because the prevention strategy must be introduced before the point of no return in gastric carcinogenesis. Although the exact point of no return has not been identified, infection should be eradicated before severe atrophy of the gastric mucosa develops. Eradication therapy rates remain suboptimal due to increasing H. pylori resistance to antibiotics and patient noncompliance. Vaccination against H. pylori would reduce the cost of eradication therapies and lower gastric cancer incidence. A vaccine against H. pylori is still a research challenge. An effective vaccine should have an adequate route of delivery, appropriate bacterial antigens and effective and safe adjuvants. Future research should focus on the development of rescue eradication therapy protocols until an efficacious vaccine against the bacterium becomes available.

Low Helicobacter pylori primary resistance to clarithromycin in gastric biopsy specimens from dyspeptic patients of a city in the interior of São Paulo, Brazil

BACKGROUND

Clarithromycin, amoxicillin, and a pump proton inhibitor are the most common drugs recommended as first-line triple therapy for H.pylori treatment, which results in eradication rates close to 80%, varying regionally, principally due to emergency cases and increases of clarithromycin resistant strains. Nucleotide substitutions at the H. pylori domain V of the 23S rRNA fraction are involved in the macrolide resistance and the A2142G and A2143G mutations are predominant in clinical isolates worldwide including in Brazil. As H. pylori culture is fastidious, we investigated the primary occurrence of H. pylori A2142G and A2143G rDNA 23S mutations using a molecular approach directly on gastric biopsies of dyspeptic patients consecutively attended at Hospital das Clinicas of Marilia, São Paulo, Brazil.

METHODS

Biopsy specimens obtained from 1137 dyspeptic patients, were subjected to histopathology and H. pylori diagnosis by histology and PCR. PCR/RFLP assay was used to detect A2142G and A2143G point mutations at domain V of the H. pylori 23S rDNA associated with clarithromycin resistance. Through the developed assay, a 768 bp PCR amplicon corresponding to1728 to 2495 bp of the 23S H. pylori rDNA is restricted with MboII for A2142G mutation detection and with BsaI for A2143G mutation detection. Occurrence of 23S rDNA A2142G results in two DNA fragments (418 and 350 bp) and of 23S rDNA A2143G results in three DNA fragments (108, 310 and 350pb), due to a conserved BsaI restriction site.

RESULTS

The PCR method used to diagnose H. pylori presented sensitivity, specificity and accuracy of 77,6%, 79,3% and 78,6%, respectively, compared to histology, the gold standard method for H. pylori diagnosis used in our routine. Prevalence of H.pylori with clarithromycin resistant genotypes was 2,46%, with predominance of A2143G 23S rDNA point mutation.

CONCLUSIONS

The PCR/RFLP assay was a rapid and accurate H.pylori diagnostic and clarithromycin resistance determination method useful for routine practice. As prevalence of primary resistance of H.pylori to clarithromycin due to A2142G and A2143G mutations remains low in Marilia, the standard clarithromycin containing triple therapy is still valid.

Current recommendations for Helicobacter pylori therapies in a world of evolving resistance

Occurrence of resistance, especially to clarithromycin, renders the standard triple therapy used to cure Helicobacter pylori infection ineffective. This review presents the bacteriological and pharmacological basis for H. pylori therapy and the current recommendations. The third-line treatment must be based on clarithromycin susceptibility testing. If the bacteria are still susceptible, failure may come from problems of compliance, hyperacidity or high bacterial load which can be overcome. If the bacteria are resistant, different regimens must be considered, including bismuth and non-bismuth-based quadruple therapies (sequential or concomitant), as well as triple therapies where amoxicillin is administered several times a day to obtain an optimal concentration at the gastric mucosal level. The treatments are becoming more and more complex and ecologically unsatisfactory, waiting for new agents or vaccines.