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

Background 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. The aim of the present study was to determine the distribution of vacA, cagA,iceA and oipA virulence factors inH. pylori strains isolated from milk and dairy products and study their antimicrobial resistance properties.Methods A 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 oipAvirulence factors. Antimicrobial susceptibility testing was performed by the disk diffusion method.Results One 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 ofvacA, cagA, iceA andoipA 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%).Conclusions High presence of antibiotic-resistant strains of H. pylorisuggest 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.

背景：尽管幽门螺杆菌（Helicobacter pylori）具有极高的研究与临床价值，但该菌的起源与传播途径至今尚未完全阐明。既往相关研究的结论与理论尚存争议，有观点提出动物源食品——尤其是牛乳——在幽门螺杆菌向人类的传播过程中扮演了重要角色。本研究旨在明确从牛乳及乳制品中分离的幽门螺杆菌菌株中vacA、cagA、iceA及oipA毒力因子的分布特征，并探究其抗菌药物耐药特性。方法：本研究共收集520份生鲜乳样本与400份传统乳制品样本，进行培养与检测。对幽门螺杆菌检测呈阳性的样本，进一步分析其vacA、cagA、iceA及oipA毒力因子的携带情况。采用纸片扩散法开展抗菌药物敏感性试验。结果：520份牛乳样本中，103份（19.8%）检出幽门螺杆菌污染；400份乳制品样本中，77份（19.2%）呈阳性。污染率最高的样本类型为绵羊乳（35%）与传统干酪（30%）。vacA、cagA、iceA及oipA毒力因子的总携带率分别为75%、76.6%、41.6%与25%。牛乳及乳制品来源的幽门螺杆菌菌株对氨苄西林（84.4%）、四环素（76.6%）、红霉素（70.5%）及甲硝唑（70%）呈现高水平耐药。结论：耐药幽门螺杆菌菌株的高检出率提示，牛乳及乳制品可能成为引发重症感染的细菌传染源。本研究结果有助于提升伊朗地区对幽门螺杆菌菌株耐药性的关注与认知。