Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, United States of America.
PLoS One. 2012;7(9):e44662. doi: 10.1371/journal.pone.0044662. Epub 2012 Sep 12.
The objective of this study was to compare the population biology of antimicrobial resistant (AR) Campylobacter coli isolated from swine reared in the conventional and antimicrobial-free (ABF) swine production systems at farm, slaughter and environment. A total of 200 C. coli isolates selected from fecal, environmental, and carcass samples of ABF (n = 100) and conventional (n = 100) swine production systems were typed by multilocus sequence typing (MLST). Sequence data from seven housekeeping genes was analyzed for the identification of allelic profiles, sequence types (STs) and clonal complex determination. Phylogenetic trees were generated to establish the relationships between the genotyped isolates. A total of 51 STs were detected including two novel alleles (glnA 424 and glyA 464) and 14 novel STs reported for the first time. The majority of the C. coli isolates belonged to ST-854 (ABF: 31, conventional: 17), and were grouped in clonal complex ST-828 (ABF: 68%, conventional: 66%). The mean genetic diversity (H) for the ABF (0.3963+/-0.0806) and conventional (0.4655+/-0.0714) systems were similar. The index of association (I(A)(S)) for the ABF (I(A)(S)= 0.1513) and conventional (I(A)(S) = 0.0991) C. coli populations were close to linkage equilibrium, indicative of a freely recombining population. Identical STs were detected between the pigs and their environment both at farm and slaughter. A minimum spanning tree revealed the close clustering of C. coli STs that originated from swine and carcass with those from the environment. In conclusion, our study reveals a genotypic diverse C. coli population that shares a common ancestry in the conventional and ABF swine production systems. This could potentially explain the high prevalence of antimicrobial resistant C. coli in the ABF system in the absence of antimicrobial selection pressure.
本研究旨在比较常规和无抗生素（ABF）猪生产系统中猪源抗微生物药物耐药（AR）空肠弯曲杆菌在农场、屠宰和环境中的种群生物学。从 ABF（n=100）和常规（n=100）猪生产系统的粪便、环境和胴体样本中选择了总共 200 株 C. coli 分离株，通过多位点序列分型（MLST）进行分型。对 7 个看家基因的序列数据进行分析，以确定等位基因谱、序列类型（ST）和克隆复合体的确定。生成系统发育树以确定基因分型分离株之间的关系。共检测到 51 个 ST，包括两个新等位基因（glnA 424 和 glyA 464）和 14 个首次报道的新 ST。大多数 C. coli 分离株属于 ST-854（ABF：31，常规：17），并被分为克隆复合体 ST-828（ABF：68%，常规：66%）。ABF（0.3963+/-0.0806）和常规（0.4655+/-0.0714）系统的平均遗传多样性（H）相似。ABF（I(A)(S)=0.1513）和常规（I(A)(S)=0.0991）C. coli 种群的关联指数（I(A)(S)）接近连锁平衡，表明这是一个自由重组的种群。在农场和屠宰场，猪与其环境之间都检测到相同的 ST。最小生成树显示，源自猪和胴体的 C. coli ST 与源自环境的 ST 紧密聚类。总之，我们的研究揭示了常规和 ABF 猪生产系统中存在遗传多样的 C. coli 种群，它们具有共同的祖先。这可能解释了在没有抗微生物选择压力的情况下 ABF 系统中高比例的抗微生物药物耐药 C. coli。
