Virulence factors and antibiotic resistance of Helicobacter pylori isolated from raw milk and unpasteurized dairy products in Iran

Soolmaz Mousavi,Ebrahim Rahimi,Farhad Dehkordi

doi:10.1186/1678-9199-20-51

Abstract

BackgroundDespite the high importance of Helicobacter pylori, the origin and transmission of this bacterium has not been clearly determined. According to controversial theories and results of previous studies, animal source foods – especially milk – play an important role in the transmission of H. pylori to humans. The aim of the present study was to determine the distribution of vacA, cagA, iceA and oipA virulence factors in H. pylori strains isolated from milk and dairy products and study their antimicrobial resistance properties.MethodsA total of 520 raw milk and 400 traditional dairy product samples were cultured and tested. Those that were H. pylori-positive were analyzed for the presence of vacA, cagA, iceA and oipA virulence factors. Antimicrobial susceptibility testing was performed by the disk diffusion method.ResultsOne hundred and three out of 520 milk samples (19.8%) and 77 out of 400 dairy products samples (19.2%) were contaminated with H. pylori. The most frequently contaminated samples were ovine milk (35%) and traditional cheese (30%). Total prevalence of vacA, cagA, iceA and oipA factors were 75%, 76.6%, 41.6% and 25%, respectively. H. pylori strains of milk and dairy products harbored high levels of resistance to ampicillin (84.4%), tetracycline (76.6%), erythromycin (70.5%) and metronidazole (70%).ConclusionsHigh presence of antibiotic-resistant strains of H. pylori suggest that milk and dairy samples may be the sources of bacteria that can cause severe infection. Our findings should raise awareness about antibiotic resistance in H. pylori strains in Iran.

Highlights

Despite the high importance of Helicobacter pylori, the origin and transmission of this bacterium has not been clearly determined
Several studies have indicated the presence of H. pylori in the stomach of domestic animals in the absence of gastritis [4,5,6,7]. It was isolated in milk of sheep, goat, cow, buffalo and camel species. These findings indicate that domestic ruminants may be a natural host for H. pylori
Prevalence of Helicobacter pylori in studied samples Eight hundred and sixty milk and dairy samples were analyzed for the presence of H. pylori

Summary

Introduction

Despite the high importance of Helicobacter pylori, the origin and transmission of this bacterium has not been clearly determined. According to controversial theories and results of previous studies, animal source foods – especially milk – play an important role in the transmission of H. pylori to humans. Helicobacter pylori is a microaerophilic gram-negative bacterium with a curved spiral shape which is known as Several studies have indicated the presence of H. pylori in the stomach of domestic animals in the absence of gastritis [4,5,6,7]. It was isolated in milk of sheep, goat, cow, buffalo and camel species. The detection of H. pylori in the milk and feces of domestic animals suggests that H. pylori may be regarded as a zoonotic infection [4,5,6,7]

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