Treilles Michaël, Châtre Pierre, Drapeau Antoine, Madec Jean-Yves, Haenni Marisa
Laboratoire d'Analyse Qualyse, Champdeniers Saint-Denis, France.
Association Régionale de Prévention contre la résistance aux Antimicrobiens, Champdeniers Saint Denis, France.
Front Microbiol. 2023 Jan 4;13:1023403. doi: 10.3389/fmicb.2022.1023403. eCollection 2022.
Colistin-resistance widely disseminated in food-producing animals due to decades of colistin use to treat diarrhea. The plasmid-borne gene has been extensively reported from bovine, swine and chicken worldwide, but smaller productions such as the goat farming sector were much less surveyed.
We looked for colistin-resistant isolates presenting plasmid-borne genes of the mcr family in both breeding (=80) and fattening farms (=5). Localization of the gene was performed using Southern blot analysis coupled to short-read and long-read sequencing.
Only the gene was identified in 10% (8/80) of the breeding farms and four over the five fattening farms. In total, 4.2% (65/1561) of the animals tested in breeding farms and 60.0% (84/140) of those tested in fattening farms presented a -positive . The gene was located either on the chromosome (32.2%) or on IncX4 (38.9%) and IncHI2 (26.8%) plasmids. As expected, both clonal expansion and plasmidic transfers were observed in farms where the gene was carried by plasmids. Tn6330 transposition was observed in the chromosome of diverse sequence types within the same farm.
Our results show that the gene is circulating in goat production and is located either on plasmids or on the chromosome. Evidence of Tn transposition highlighted the fact that chromosomal insertion does not impair the transmission capability of the gene. Only strict hygiene and biosecurity procedures in breeding farms, as well as a prudent use of antibiotics in fattening farms, can avoid such complex contamination pathways.
由于数十年来使用粘菌素治疗腹泻，粘菌素耐药性在食用动物中广泛传播。全球范围内，牛、猪和鸡中广泛报道了质粒携带的该基因，但山羊养殖等较小规模的养殖行业受调查的较少。
我们在种羊场（=80个）和育肥场（=5个）中寻找携带mcr家族质粒携带基因的粘菌素耐药分离株。使用Southern印迹分析结合短读长和长读长测序对该基因进行定位。
仅在10%（8/80）的种羊场和5个育肥场中的4个中鉴定出该基因。在种羊场检测的动物中，共有4.2%（65/1561）呈mcr阳性，在育肥场检测的动物中，60.0%（84/140）呈mcr阳性。该基因位于染色体（32.2%）或IncX4质粒（38.9%）和IncHI2质粒（26.8%）上。正如预期的那样，在该基因由质粒携带的养殖场中观察到了克隆扩增和质粒转移。在同一养殖场内不同mcr序列类型的染色体中观察到Tn6330转座。
我们的结果表明，mcr基因在山羊养殖中传播，且位于质粒或染色体上。Tn转座的证据突出了染色体插入不会损害mcr基因传播能力这一事实。只有种羊场严格的卫生和生物安全程序，以及育肥场谨慎使用抗生素，才能避免如此复杂的污染途径。
