UCD Centre for Food Safety & Centre for Food-borne Zoonomics, UCD Veterinary Sciences Centre, University College Dublin, Belfield, Dublin 4, Ireland.
Appl Environ Microbiol. 2011 Oct;77(20):7121-7. doi: 10.1128/AEM.00601-11. Epub 2011 Aug 19.
This study describes the genotypic characteristics of a collection of 100 multidrug-resistant (MDR) Escherichia coli strains recovered from cattle and the farm environment in Ireland in 2007. The most prevalent antimicrobial resistance identified was to streptomycin (100%), followed by tetracycline (99%), sulfonamides (98%), ampicillin (82%), and neomycin (62%). Resistance was mediated predominantly by strA-strB (92%), tetA (67%), sul2 (90%), bla(TEM) (79%), and aphA1 (63%) gene markers, respectively. Twenty-seven isolates harbored a class 1 integrase (intI1), while qacEΔ1 and sul1 markers were identified in 25 and 26 isolates, respectively. The variable regions of these integrons contained aminoglycoside, trimethoprim, and β-lactam resistance determinants (aadA12, aadB-aadA1, bla(OXA-30)-aadA1, dfrA1-aadA1, dfrA7). Class 2 integrons were identified less frequently (4%) and contained the gene cassette array dfrA1-sat1-aadA1. Resistance to ampicillin, neomycin, streptomycin, sulfonamide, and tetracycline was associated with transferable high-molecular-weight plasmids, as demonstrated by conjugation assays. A panel of virulence markers was screened for by PCR, and genes identified included vt1, K5 in 2 isolates, papC in 10 isolates, and PAI IV(536) in 37 isolates. MDR commensal E. coli isolates from Irish cattle displayed considerable diversity with respect to the genes identified. Our findings highlight the importance of the commensal microflora of food-producing animals as a reservoir of transferable MDR.
本研究描述了 2007 年从爱尔兰牛群和农场环境中分离的 100 株多药耐药（MDR）大肠杆菌的基因型特征。鉴定出的最常见的抗生素耐药性是链霉素（100%），其次是四环素（99%）、磺胺类（98%）、氨苄青霉素（82%）和新霉素（62%）。耐药性主要由 strA-strB（92%）、tetA（67%）、sul2（90%）、bla(TEM)（79%）和 aphA1（63%）基因标记介导。27 株分离物携带 1 类整合酶（intI1），而 qacEΔ1 和 sul1 标记分别在 25 和 26 株分离物中鉴定出。这些整合子的可变区含有氨基糖苷类、甲氧苄啶和β-内酰胺类耐药决定因子（aadA12、aadB-aadA1、bla(OXA-30)-aadA1、dfrA1-aadA1、dfrA7）。较少鉴定出 2 类整合子（4%），并含有基因盒阵列 dfrA1-sat1-aadA1。通过接合试验证实，对氨苄青霉素、新霉素、链霉素、磺胺类和四环素的耐药性与可转移的高分子量质粒有关。通过 PCR 筛选了一组毒力标记物，鉴定出的基因包括 vt1、2 株中的 K5、10 株中的 papC 和 37 株中的 PAI IV(536)。来自爱尔兰牛的多药耐药共生大肠杆菌分离物在鉴定出的基因方面表现出相当大的多样性。我们的研究结果强调了食品生产动物共生微生物群作为可转移多药耐药性的储存库的重要性。
