Molecular analysis of low-level tetracycline resistance in clinical isolates of Helicobacter pylori among dyspeptic patients in South West Nigeria.

OBJECTIVES: The aim of this study was to determine the occurrence of 16S rRNA mutations associated with low-level tetracycline resistance in Helicobacter pylori isolates from adult dyspeptic patients in South West Nigeria. METHODS: Susceptibility testing to tetracycline of 50 H. pylori isolates was performed by Etest. The 535-bp conserved region of the H. pylori tetracycline-binding site of 16S rRNA was amplified by PCR, followed by sequencing and multiple sequence alignment for all 50 clinical isolates. RESULTS: Of the 50 clinical isolates examined, DNA sequence analysis revealed nucleotide substitutions in 7 isolates at positions 926-928. Of the seven isolates, two demonstrated reduced susceptibility to tetracycline with Etest minimum inhibitory concentrations (MICs) of 0.75-1.0mg/L, whilst the other five isolates were resistant with MICs of 1.5-24mg/L (resistance breakpoint >1mg/L). The two isolates with reduced susceptibility had single nucleotide substitution of A926G, whilst the five resistant isolates demonstrated double base pair substitutions of G927T/A928C and A926G/A928C and a single nucleotide substitution of A926G. CONCLUSIONS: This study shows that low-level tetracycline resistance amongst H. pylori-positive dyspeptic patients is associated with reduced susceptibility and resistance to tetracycline. This is the result of 1-bp and 2-bp differences in positions 926 and 926-928, respectively, in the 16S rRNA of H. pylori.

Helicobacter pylori strains from a Nigerian cohort show divergent antibiotic resistance rates and a uniform pathogenicity profile.

Antibiotic resistance in Helicobacter pylori is a factor preventing its successful eradication. Particularly in developing countries, resistance against commonly used antibiotics is widespread. Here, we present an epidemiological study from Nigeria with 111 isolates. We analyzed the associated disease outcome, and performed a detailed characterization of these isolated strains with respect to their antibiotic susceptibility and their virulence characteristics. Furthermore, statistical analysis was performed on microbiological data as well as patient information and the results of the gastroenterological examination. We found that the variability concerning the production of virulence factors between strains was minimal, with 96.4% of isolates being CagA-positive and 92.8% producing detectable VacA levels. In addition, high frequency of bacterial resistance was observed for metronidazole (99.1%), followed by amoxicillin (33.3%), clarithromycin (14.4%) and tetracycline (4.5%). In conclusion, this study indicated that the infection rate of H. pylori infection within the cohort in the present study was surprisingly low (36.6%). Furthermore, an average gastric pathology was observed by histological grading and bacterial isolates showed a uniform pathogenicity profile while indicating divergent antibiotic resistance rates.