背景：
食物生产动物携带抗生素抗性食源性病原体是卫生保健机构中治疗失败的众多因素之一，并且需要综合方法来研究携带食物动物中整合子的抗性病原体的携带。

方法：
使用MIC方法，PFGE分析，PCR和测序，测试了对四环素抗生素（n = 92）易感性降低的大肠杆菌分离物之间的关联，即1类整合子的携带，系统发育组附属和四环素抗性决定簇之间的关联。

结果：
Phylogroups B1和A是最常见的（分别为58.7％和19.6％），其次是D组（20.7％）和B2组（1.1％）。所有分离株都携带至少一种检测的tet基因。此外，88（95.7％）的四环素抗性分离株携带tet（A）或tet（B），而47（51.1％）和41（44.6％）分别携带tet（A）或tet（B） 。同样，携带这些基因的分离株携带1类整合子的机会较高（P <0.05）。在测试的分离株中，38个（41.3％）携带intI1基因。在27个分离株中识别出在3'-CS处具有完整基因（sul1和qacEΔ1）的经典整合子。 PCR筛选和随后的测序证明，84.2％（32/38）的intI1阳性分离株含有抗性基因盒。总之，鉴定了7个基因盒，单独或与另一个基因盒组合。最常见的基因是aadA1（10个分离株），然后是aadA1-dfrA1（7个分离株），aadA1-dfrA12（6个分离株）和aadA1-aadA2-dfrA12（3个分离株）的组合。使用PFGE的遗传分型显示出最小的克隆相关性，具有28个不同的簇和12-25个可辨别的DNA片段。

结论：
该研究为共生子的存在，系统发育群关联和共生大肠杆菌菌株中四环素抗生素抗性决定簇的特征之间的关系提供了新的见解。

BACKGROUND:
Carriage of antibiotic-resistant foodborne pathogens by food production animals is one of many contributors to treatment failure in health care settings, and it necessitates an integrated approach to investigate the carriage of resistant pathogens harboring integrons in food-producing animals.

METHODS:
Escherichia coli isolates with reduced susceptibility to tetracycline antibiotics (n = 92) were tested for associations between carriage of class1 integrons, phylogenetic group affiliation and tetracycline resistance determinants using the MIC method, PFGE analysis, PCR and sequencing.

RESULTS:
Phylogroups B1 and A were the most common (58.7 and 19.6%, respectively), followed by groups D (20.7%) and B2 (1.1%). All isolates carried at least one of the tet genes examined. In addition, 88 (95.7%) of all tetracycline-resistant isolates carried tet(A) or tet(B), while 47 (51.1%) and 41 (44.6%) harbored only tet(A) or tet(B), respectively. Likewise, isolates harboring these genes had a higher chance (P < 0.05) of carrying class 1 integrons. Of the tested isolates, 38 (41.3%) carried the intI1 gene. Classical integrons with complete genes (sul1 and qacE∆1) at the 3'-CS were recognized in 27 isolates. PCR screening and subsequent sequencing demonstrated that 84.2% (32/38) of the intI1-positive isolates harbored resistance gene cassettes. Overall, seven gene cassettes were identified, either solely or combined with another gene cassette. The most common gene was aadA1 (10 isolates), followed by a combination of aadA1-dfrA1 (seven isolates), aadA1-dfrA12 (six isolates) and aadA1-aadA2-dfrA12 (three isolates). Genetic typing using PFGE showed minimum clonal relatedness with 28 different clusters and 12-25 discernible DNA fragments.

CONCLUSIONS:
This study brings new insight into the relationships between the presence of integrons, phylogenetic group association and characteristics of tetracycline antibiotic resistance determinants in commensal E. coli strains.