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Background  Treatment effectiveness of  Helicobacter pylori  varies regionally and is decreasing worldwide, principally as a result of antibiotic resistant bacterium. Tetracycline is generally included in second line  H. pylori  eradication regimens. In Brazil, a high level of tetracycline resistance (TetR) is mainly associated with AGA926-928TTC 16 S rDNA nucleotide substitutions. As  H. pylori  culture is fastidious, we investigated the primary occurrence of  H. pylori  16 S rDNA high level TetR genotype using a molecular approach directly on gastric biopsies of dyspeptic patients attending consecutively at Hospital das Clinicas of Marilia, São Paulo, Brazil.    Methods  Gastric biopsy specimens of 68 peptic ulcer disease (PUD) and 327 chronic gastritis (CG) patients with a positive histological diagnosis of  H. pylori  were investigated for TetR 16 S rDNA genotype through a molecular assay based on amplification of a 16 S rDNA 545 bp fragment by polymerase chain reaction and H infI  restriction fragment length polymorphism (PCR/RFLP). Through this assay, AGA926-928TTC 16 S rDNA TetR genotype resulted in a three DNA fragment restriction pattern (281, 227 and 37 bp) and its absence originated two DNA fragments (264 and 281 bp) due to a 16 S rDNA conserved H inf I  restriction site.    Results  The 545 bp 16 S rDNA PCR fragment was amplified from 90% of gastric biopsies from histological  H. pylori  positive patients. H infI  RFLP revealed absence of the AGA926–928TTC  H. pylori  genotype and PCR products of two patients showed absence of the conserved 16 S rDNA H infI  restriction site. BLASTN sequence analysis of four amplicons (two conserved and two with an unpredicted H infI  restriction pattern) revealed a 99% homology to  H. pylori  16 S rDNA from African, North and South American bacterial isolates. A nucleotide substitution abolished the conserved H infI  restriction site in the two PCR fragments with unpredicted H infI  RFLP, resulting in an E coRI  restriction site.    Conclusions   H. pylori  AGA926-928TTC 16 S rDNA gene substitutions were not found in our population. More research is required to investigate if  H. pylori  TetR has a different genetic background in our region and if the nucleotide substitutions of the uncultured  H. pylori  16 S rRNA partial sequences have biological significance.

bmc gastroenterology

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