Ramonaite Sigita, Tamuleviciene Egle, Alter Thomas, Kasnauskyte Neringa, Malakauskas Mindaugas
Department of Food Safety and Quality, Faculty of Veterinary Medicine, Veterinary Academy, Lithuanian University of Health Sciences, A. Mickeviciaus st. 9, LT 44307, Kaunas, LT, Lithuania.
Clinic of Children Diseases, Medicine Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania.
BMC Infect Dis. 2017 Jun 15;17(1):430. doi: 10.1186/s12879-017-2535-1.
Campylobacter (C.) jejuni is the leading cause of human campylobacteriosis worldwide. We performed a molecular epidemiological study to investigate the genetic relationship among C. jejuni strains isolated from human diarrhoeal patients, broiler products and dairy cattle in Lithuania.
The C. jejuni isolates from human clinical cases, dairy cattle and broiler products were genotyped using multilocus sequence typing (MLST). Allele numbers for each housekeeping gene, sequence type (ST), and clonal complex (CC) were assigned by submitting the DNA sequences to the C. jejuni MLST database ( http://pubmlst.org/campylobacter ). Based on the obtained sequence data of the housekeeping genes a phylogenetic analysis of the strains was performed and a minimum spanning tree (MST) was calculated.
Among the 262 C. jejuni strains (consisting of 43 strains isolated from dairy cattle, 102 strains isolated from broiler products and 117 clinical human C. jejuni strains), 82 different MLST sequence types and 22 clonal complexes were identified. Clonal complexes CC21 and CC353 predominated among the C. jejuni strains. On ST-level, five sequence types (ST-5, ST-21, ST-50, ST-464 and ST-6410) were dominating and these five STs accounted for 35.9% (n = 94) of our isolates. In addition, 51 (19.5%) C. jejuni strains representing 27 (32.9%) STs were reported for the first time in the PubMLST database ( http://pubmlst.org/campylobacter ). The highest Czekanowski index or proportional similarity index (PSI) was calculated for C. jejuni strains isolated from human campylobacteriosis cases and broiler products (PSI = 0.32) suggesting a strong link between broiler strains and human cases. The PSI of dairy cattle and human samples was lower (PSI = 0.11), suggesting a weaker link between bovine strains and human cases. The calculated Simpson's index of all C. jejuni isolates showed a high genetic diversity (D = 0.96).
Our results suggest that broiler products are the most important source of human campylobacteriosis in Lithuania. The study provides information on MLST type distribution and genetic relatedness of C. jejuni strains from humans, broiler products and dairy cattle in Lithuania for the first time, enabling a better understanding of the transmission pathways of C. jejuni in this country.
空肠弯曲菌是全球人类弯曲菌病的主要病因。我们开展了一项分子流行病学研究，以调查立陶宛从人类腹泻患者、肉鸡产品和奶牛中分离出的空肠弯曲菌菌株之间的遗传关系。
使用多位点序列分型（MLST）对从人类临床病例、奶牛和肉鸡产品中分离出的空肠弯曲菌菌株进行基因分型。通过将DNA序列提交至空肠弯曲菌MLST数据库（http://pubmlst.org/campylobacter），为每个管家基因、序列类型（ST）和克隆复合体（CC）分配等位基因编号。基于获得的管家基因序列数据，对菌株进行系统发育分析并计算最小生成树（MST）。
在262株空肠弯曲菌菌株（包括从奶牛中分离出的43株、从肉鸡产品中分离出的102株和临床人类空肠弯曲菌菌株117株）中，鉴定出82种不同的MLST序列类型和22个克隆复合体。克隆复合体CC21和CC353在空肠弯曲菌菌株中占主导地位。在ST水平上，五种序列类型（ST-5、ST-21、ST-50、ST-464和ST-6410）占主导地位，这五种STs占我们分离株的35.9%（n = 94）。此外，在PubMLST数据库（http://pubmlst.org/campylobacter）中首次报告了代表27种（32.9%）STs的51株（19.5%）空肠弯曲菌菌株。从人类弯曲菌病病例和肉鸡产品中分离出的空肠弯曲菌菌株计算出的切卡诺夫斯基指数或比例相似性指数（PSI）最高（PSI = 0.32），表明肉鸡菌株与人类病例之间存在紧密联系。奶牛和人类样本的PSI较低（PSI = 0.11），表明牛菌株与人类病例之间的联系较弱。计算出的所有空肠弯曲菌分离株的辛普森指数显示出高度的遗传多样性（D = 0.96）。
我们的结果表明，在立陶宛，肉鸡产品是人类弯曲菌病最重要的来源。该研究首次提供了立陶宛人类、肉鸡产品和奶牛中空肠弯曲菌菌株的MLST类型分布和遗传相关性信息，有助于更好地了解该国空肠弯曲菌的传播途径。
