Abstracts (first author)


An adaptive evolution of Helicobacter pylori (H.pylori): what is a role Cag-A loss in the era of antibacterial treatment?

Author(s): Nijevitch AA


A resistance to antibacterial drugs is a classic demonstration of natural selection in microorganisms during the period of host-bacterial interaction and high intensity of antibiotic exposure. The aim of the study was to determine the evolutionary role of the CagA pathogenicity island (PAI) presence in the outcome of eradication treatment of H.pylori. Sixty-seven pediatric patients with upper dyspepsia (mean age 13.7 years, range 5 to 17 years, male/female 24/43) undergoing endoscopy were investigated for H.pylori presence. Gastric antral biopsy specimens were taken for histology and/or culture and one biopsy fragment was used for CagA PCR determination. H.pylori+ (positive) patients were treated with a two-week course of amoxycilline (50 mg/kg/day), bismuth subcitrate (8 mg/kg/day), nifuratel (30 mg/kg/day) plus omeprazole (1 mg/kg, once daily). The criterion for eradication of H.pylori was the negative breath ammonia test. Forty one of 67 children (61.2%) were H.pylori+. Nineteen of 41 strains (46.3%) were CagA+ (group I) and 22 were CagA– (negative) (group II) (53.7%). H.pylori was eradicated in 33 patients (80.4%). Among the patients with successful eradication 19 children were CagA+, 14 - were CagA–. Thus, significantly more patients in group II than in group I had evidence of ongoing H.pylori infection (63.6% (14/22) versus 94.7% (18/19); χ2=4.08, p=0.0021). Eight children (19.6%) remained H.pylori+. Obviously, the carriage of CagA-lacking strain was strongly associated with unsuccessful eradication (OR=10.28; 95CI, 1.148 to 92.173). The strains of H.pylori lacking the cag PAI, or parts of it, have lost the island through transformation with an empty site or through deletion mutations. It is possible, that this particular phenomenon, associated with genome plasticity, not just allows the microbe to maintain balanced relationship with the host, but also to survive in antibacterial therapy conditions.


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XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon


Computational Biology & Population Genomics Group