Schulz Jochen, Ruddat Inga, Hartung Jörg, Hamscher Gerd, Kemper Nicole, Ewers Christa
Institute for Animal Hygiene, Animal Welfare and Farm Animal Behaviour, University of Veterinary Medicine Hannover, Foundation Hannover, Germany.
Department of Biometry, Epidemiology and Information Processing, University of Veterinary Medicine Hannover, Foundation Hannover, Germany.
Front Microbiol. 2016 Jun 10;7:866. doi: 10.3389/fmicb.2016.00866. eCollection 2016.
In a retrospective study, 119 sedimentation dust samples stored between five and 35 years from various barns of intensive livestock farming were evaluated for the occurrence of cultivatable Escherichia coli. Growth of E. coli occurred in 54 samples. Successful cultivation was achieved in samples from as early as 1994. The frequency of detection increased from earlier to later time periods, but the concentrations, which ranged between 3.4 × 10(2) and 1.1 × 10(5) colony-forming units per gram, did not correlate with sample age (Spearman rank correlation; p > 0.05). We hypothesize that E. coli cells survived in dust samples without cell division because of the storage conditions. Dry material (dust) with low water activities (arithmetic mean < 0.6) and storage at 4°C in the dark likely facilitated long-term survival. E. coli were isolated on MacConkey agar with and without ciprofloxacin supplementation. For 110 isolates (79 from non-supplemented media and 31 from supplemented media), we determined the E. coli phylotype and antimicrobial resistance. Six phylogenetic groups were identified. Phylogroups A and B1 predominated. Compared to group A, phylogroup B1 was significantly associated with growth on ciprofloxacin-supplemented media (chi-square test, p = 0.003). Furthermore, the antibiotic resistance profiles determined by a microdilution method revealed that isolates were phenotypically resistant to at least one antimicrobial substance and that more than 50% were resistant to a minimum of five out of 10 antibiotics tested. A linear mixed model was used to identify factors associated with the number of phenotypic resistances of individual isolates. Younger isolates and isolates from fattening poultry barns tended to be resistant to significantly more antibiotics than older isolates and those from laying-hen houses (p = 0.01 and p = 0.02, respectively). Sample origin and storage conditions may have influenced the number of antimicrobial resistances. Overall, we found that under particular conditions, dust from farm animal houses can be reservoirs for antimicrobial-resistant E. coli for at least 20 years. The survival strategies that allow E. coli to survive such long periods in environmental samples are not fully understood and could be an interesting research topic for future studies.
在一项回顾性研究中，对来自集约化畜牧养殖不同畜舍、储存了5至35年的119份沉积灰尘样本进行了可培养大肠杆菌存在情况的评估。54份样本中出现了大肠杆菌生长。早在1994年的样本中就成功实现了培养。检测频率从早期到后期有所增加，但浓度范围在每克3.4×10²至1.1×10⁵菌落形成单位之间，与样本年龄无关（Spearman等级相关性；p>0.05）。我们推测，由于储存条件，大肠杆菌细胞在灰尘样本中存活但未进行细胞分裂。低水分活度（算术平均值<0.6）的干燥物质（灰尘）以及在4°C黑暗条件下储存可能有助于长期存活。在添加和不添加环丙沙星的麦康凯琼脂上分离出大肠杆菌。对于110株分离株（79株来自未添加培养基，31株来自添加培养基），我们确定了大肠杆菌的系统发育型和抗菌药物耐药性。鉴定出六个系统发育组。A组和B1组占主导。与A组相比，B1组与在添加环丙沙星的培养基上生长显著相关（卡方检验，p = 0.003）。此外，通过微量稀释法确定的抗生素耐药谱显示，分离株对至少一种抗菌物质具有表型耐药性，并且超过50%的分离株对所测试的10种抗生素中的至少5种耐药。使用线性混合模型来确定与单个分离株表型耐药数量相关的因素。较年轻的分离株以及来自育肥禽舍的分离株往往比年长的分离株以及来自产蛋鸡舍的分离株对显著更多的抗生素耐药（分别为p = 0.01和p = 0.02）。样本来源和储存条件可能影响了抗菌药物耐药性的数量。总体而言，我们发现，在特定条件下，家畜饲养舍的灰尘至少20年来可能一直是耐抗菌药物大肠杆菌的储存库。大肠杆菌在环境样本中能够长期存活的生存策略尚未完全了解，可能是未来研究的一个有趣课题。
