Helicobacter pylori patient isolates from South Africa and Nigeria differ in virulence factor pathogenicity profile and associated gastric disease outcome

Helicobacter pylori is a gram-negative, spiral-shaped bacterial pathogen and the causative agent for gastritis, peptic ulcer disease and classified as a WHO class I carcinogen. While the prevalence of H. pylori infections in Africa is among the highest in the world, the incidence of gastric cancer is comparably low. Little is known about other symptoms related to the H. pylori infection in Africa and the association with certain phenotypes of bacterial virulence. We established a network of study sites in Nigeria (NG) and South Africa (ZA) to gain an overview on the epidemiological situation. In total 220 isolates from 114 patients were analyzed and 118 different patient isolates examined for the presence of the virulence factors cagA, vacA, dupA, their phylogenetic origin and their resistance against the commonly used antibiotics amoxicillin, clarithromycin, metronidazole and tetracycline. We report that H. pylori isolates from Nigeria and South Africa differ significantly in their phylogenetic profiles and in their expression of virulence factors. VacA mosaicism is intensive, resulting in m1-m2 vacA chimeras and frequent s1m1 and s1m2 vacA subtypes in hpAfrica2 strains. Gastric lesions were diagnosed more frequent in Nigerian versus South African patients and H. pylori isolates that are resistant against one or multiple antibiotics occur frequently in both countries

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

Elevated rates of horizontal gene transfer in the industrialized human microbiome

Industrialization has impacted the human gut ecosystem, resulting in altered microbiome composition and diversity. Whether bacterial genomes may also adapt to the industrialization of their host populations remains largely unexplored. Here, we investigate the extent to which the rates and targets of horizontal gene transfer (HGT) vary across thousands of bacterial strains from 15 human populations spanning a range of industrialization. We show that HGTs have accumulated in the microbiome over recent host generations and that HGT occurs at high frequency within individuals. Comparison across human populations reveals that industrialized lifestyles are associated with higher HGT rates and that the functions of HGTs are related to the level of host industrialization. Our results suggest that gut bacteria continuously acquire new functionality based on host lifestyle and that high rates of HGT may be a recent development in human history linked to industrialization.Peer reviewe

Primer sequences.

<p>Primer sequences.</p

EPIYA motifs.

<p>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 [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0176454#pone.0176454.ref028" target="_blank">28</a>].</p

Characterization of <i>H</i>. <i>pylori</i> isolates.

<p>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. <u>Black:</u> shows PCR results of the genes <i>cagA</i> and <i>vacA</i>. <u>Grey:</u> 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 <i>H</i>. <i>pylori</i> P12. Each dot illustrates one isolate. <u>Black:</u> isolates produce VacA, CagA, and are also able to translocate CagA. <u>Green:</u> isolates which produce neither VacA nor CagA and show no CagA translocation. <u>Red:</u> isolates which do produce VacA, but not CagA. <u>Blue:</u> isolates which produce and translocate CagA, but do not produce VacA. <u>Purple:</u> isolates which produce VacA and CagA, but are not able to translocate CagA.</p

Pathology analyzed by a histological grading (based on the updated Sydney System (22)) in HE stained slides.

<p>Pathology analyzed by a histological grading (based on the updated Sydney System (22)) in HE stained slides.</p