ISG Summer Meeting 2016

Oral Prize - Third Prize

Denise Brennan

Oral (16S146)

Can bacterial virulence factors predict antibiotic resistant H. pylori infection?


Denise Brennan1, Mark Feighery2, Ciara Treacy1, Edwin Fahy1, Joseph Omorogbe1, Mary Hussey1, Donal Tighe1, Grainne Holleran1, Colm O’Morain1, Deirdre McNamara1*, Sinead Smith1,2*. preprocess


1Trinity Academic Gastroenterology Group (TAGG), Department of Clinical Medicine, Trinity College Dublin. 2School of Pharmacy & Pharmaceutical Sciences, Trinity College Dublin. *Joint senior authors. preprocess


Virulence factors produced by H. pylori contribute to the pathogenicity of the organism. Cytotoxin-associated gene A (cagA) and vacuolating-associated gene A (vacA) are the main H. pylori virulence factors. The frequency of virulence factor genotype differs across countries and recent data suggests that the cagA and vacA virulence factors may influence H. pylori treatment outcome. preprocess


To evaluate the impact of virulence factor genotype (vacA and cagA) on the prevalence of primary H. pylori antibiotic resistance. preprocess


Following ethical approval and informed consent, DNA was isolated from gastric biopsies of treatment naïve adult patients infected with H. pylori (determined by histology) at Tallaght Hospital. Virulence factor genotyping was performed using PCR and genotypic susceptibility to clarithromycin and levofloxacin was tested using the GenoType HelicoDR assay (Hain Lifesciences). The chi-squared test was used to assess correlations between H. pylori genotypes and drug susceptibilities. preprocess


A total of 50 samples from H. pylori positive patients, average age 47.6 years, 56% male (n=28), were analysed. 38% (n=19) of samples possessed the cagA gene. The most common vacA genotype was the moderately virulent S1/M2 genotype at 36% (n=18), followed by the highly virulent genotype S1/M1 at 34% (n=17), the S2/M2 genotype at 28% (n=14) and the S2/M1 genotype at 2% (n=1). A clarithromycin resistant genotype was observed in 38% (n=19) of samples. A levofloxacin resistant genotype was observed in 6% (n=3). Resistance to both agents was found in 6% (n=3) samples. The clarithromycin resistance rate in the cagA- group was significantly higher than in cagA+ (48.3% vs 21.1%, χ=3.74, p=0.05, OR 0.2844). There was no significant difference in either the clarithromycin or levofloxacin resistance rate between vacA genotypes. preprocess


CagA- and vacA S1/M2 are the dominant genotypes in H. pylori strains in our cohort. Infection with cagA- H. pylori may predict clarithromycin resistance. This may be because cagA+ bacteria replicate at a higher rate and are therefore more susceptible to clarithromycin, so will be eradicated faster. Further study is planned to investigate the clinical relevance of virulence factors in H. pylori infection. preprocess

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