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

Abstract

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.

Fig 1. Study design.

Fig 2. Characterization of H. pylori isolates.

111 isolated strains were characterized by the status of resistance, the analysis of the major virulence factors as well as their IL-8 expression. A: The bacterial resistance to amoxicillin, clarithromycin, metronidazole and tetracycline is shown as percentage. These results are based on MIC tests. B. Black: shows PCR results of the genes cagA and vacA. Grey: shows the Western blotting results of the proteins CagA, translocation of CagA into AGS cells, and VacA. C. Induction of IL-8 secretion by AGS cells in relation to H. pylori P12. Each dot illustrates one isolate. Black: isolates produce VacA, CagA, and are also able to translocate CagA. Green: isolates which produce neither VacA nor CagA and show no CagA translocation. Red: isolates which do produce VacA, but not CagA. Blue: isolates which produce and translocate CagA, but do not produce VacA. Purple: isolates which produce VacA and CagA, but are not able to translocate CagA.

Fig 3. EPIYA motifs.

EPIYA region sequences of 14 isolates including reference strains (196A, 26695, ATCC43526, and P12) are shown (red). 9 isolates show the KDKGPE motif (blue) in front of the EPIYA-A motif [28].

Fig 4. Phylogenetic tree of strains used in this study and representative strains from different populations.

All strains used in this study are represented by blue dots, cluster with the hpAfrica1 (hspWAfrica) strains 908, Gambia 94–24, and J99. Strains from other populations are color-coded as indicated.