Colistin use per farm expressed as TiDDDVet.

Background
Colistin serves as the last line of defense against multidrug resistant Gram-negative bacterial infections in both human and veterinary medicine. This study aimed to investigate the occurrence and spread of colistin-resistant Enterobacterales (ColR-E) using a One Health approach in Belgium and in the Netherlands.
Methods
In a transnational research project, a total of 998 hospitalized patients, 1430 long-term care facility (LTCF) residents, 947 children attending day care centres, 1597 pigs and 1691 broilers were sampled for the presence of ColR-E in 2017 and 2018, followed by a second round twelve months later for hospitalized patients and animals. Colistin treatment incidence in livestock farms was used to determine the association between colistin use and resistance. Selective cultures and colistin minimum inhibitory concentrations (MIC) were employed to identify ColR-E. A combination of short-read and long-read sequencing was utilized to investigate the molecular characteristics of 562 colistin-resistant isolates. Core genome multi-locus sequence typing (cgMLST) was applied to examine potential transmission events.
Results
The presence of ColR-E was observed in all One Health sectors. In Dutch hospitalized patients, ColR-E proportions (11.3 and 11.8% in both measurements) were higher than in Belgian patients (4.4 and 7.9% in both measurements), while the occurrence of ColR-E in Belgian LTCF residents (10.2%) and children in day care centres (17.6%) was higher than in their Dutch counterparts (5.6% and 12.8%, respectively). Colistin use in pig farms was associated with the occurrence of colistin resistance. The percentage of pigs carrying ColR-E was 21.8 and 23.3% in Belgium and 14.6% and 8.9% in the Netherlands during both measurements. The proportion of broilers carrying ColR-E in the Netherlands (5.3 and 1.5%) was higher compared to Belgium (1.5 and 0.7%) in both measurements. mcr-harboring E. coli were detected in 17.4% (31/178) of the screened pigs from 7 Belgian pig farms. Concurrently, four human-related Enterobacter spp. isolates harbored mcr-9.1 and mcr-10 genes. The majority of colistin-resistant isolates (419/473, 88.6% E. coli; 126/166, 75.9% Klebsiella spp.; 50/75, 66.7% Enterobacter spp.) were susceptible to the critically important antibiotics (extended-spectrum cephalosporins, fluoroquinolones, carbapenems and aminoglycosides).
Chromosomal colistin resistance mutations have been identified in globally prevalent high-risk clonal lineages, including E. coli ST131 (n = 17) and ST1193 (n = 4). Clonally related isolates were detected in different patients, healthy individuals and livestock animals of the same site suggesting local transmission. Clonal clustering of E. coli ST10 and K. pneumoniae ST45 was identified in different sites from both countries suggesting that these clones have the potential to spread colistin resistance through the human population or were acquired by exposure to a common (food) source. In pig farms, the continuous circulation of related isolates was observed over time. Inter-host transmission between humans and livestock animals was not detected.
Conclusions
The findings of this study contribute to a broader understanding of ColR-E prevalence and the possible pathways of transmission, offering insights valuable to both academic research and public health policy development.

背景
粘菌素（Colistin）是当前人类与兽医医学中对抗多重耐药革兰氏阴性菌感染的最后一线治疗药物。本研究旨在采用一体化健康（One Health）研究策略，调查比利时与荷兰境内耐粘菌素肠杆菌目细菌（ColR-E）的流行与传播情况。
方法
本跨国研究项目于2017年及2018年开展采样，共纳入998名住院患者、1430名长期护理机构（LTCF）入住者、947名日托中心儿童、1597头生猪以及1691只肉鸡，检测样本中ColR-E的存在情况；随后在12个月后，针对住院患者与畜禽开展第二轮采样。本研究通过畜禽养殖场粘菌素使用量数据，分析粘菌素使用与耐药性之间的关联。采用选择性培养法与粘菌素最低抑菌浓度（minimum inhibitory concentrations, MIC）试验鉴定ColR-E。结合短读长与长读长测序技术，对562株耐粘菌素分离株的分子特征展开分析。采用核心基因组多位点序列分型（core genome multi-locus sequence typing, cgMLST）探究潜在的传播事件。
结果
本研究在所有一体化健康相关领域均检出ColR-E。荷兰住院患者的ColR-E检出率（两次检测分别为11.3%与11.8%）高于比利时住院患者（分别为4.4%与7.9%）；而比利时长期护理机构入住者（10.2%）与日托中心儿童（17.6%）的ColR-E检出率则高于荷兰对应人群（分别为5.6%与12.8%）。生猪养殖场的粘菌素使用情况与耐粘菌素耐药性的发生存在关联。两次采样中，比利时生猪的ColR-E携带率分别为21.8%与23.3%，荷兰生猪则分别为14.6%与8.9%。荷兰肉鸡的ColR-E携带率（两次检测分别为5.3%与1.5%）高于比利时（分别为1.5%与0.7%）。在比利时7个养猪场的筛查样本中，17.4%（31/178）的生猪携带携带mcr基因的大肠杆菌（E. coli）。同时，4株与人类相关的肠杆菌属分离株携带mcr-9.1与mcr-10基因。大部分耐粘菌素分离株（大肠杆菌：419/473，占比88.6%；克雷伯菌属：126/166，占比75.9%；肠杆菌属：50/75，占比66.7%）对极重要抗菌药物——包括超广谱头孢菌素、氟喹诺酮类、碳青霉烯类与氨基糖苷类——均敏感。
研究在全球流行的高风险克隆谱系中检出了染色体介导的粘菌素耐药突变，包括大肠杆菌ST131（n=17）与ST1193（n=4）。在同一地点的不同患者、健康个体与畜禽体内均检出克隆相关分离株，提示存在局部传播。在两国不同采样点均发现大肠杆菌ST10与肺炎克雷伯菌ST45的克隆簇，提示这些克隆有可能通过人群传播耐粘菌素耐药性，或是通过接触共同的（食品）来源获得耐药性。在养猪场中，观察到相关分离株随时间持续循环传播。未检测到人类与畜禽之间的宿主间传播。
结论
本研究结果有助于更全面地理解ColR-E的流行特征与潜在传播途径，可为学术研究与公共卫生政策制定提供有价值的参考依据。