New gene cassettes for trimethoprim resistance, dfr13, and streptomycin-spectinomycin resistance, aadA4, inserted on a class 1 integron
New gene cassettes for trimethoprim resistance, dfr13, and streptomycin-spectinomycin resistance, aadA4, inserted on a class 1 integron
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DOI：
10.1128/aac.44.2.355-361.2000
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发表时间：
2000-02-01
影响因子：
4.9
通讯作者：
Amyes, SGB
中科院分区：
文献类型：
--
作者：
Adrian, PV;Thomson, CJ;Amyes, SGB
在以前的调查中，357株耐甲氧苄氨嘧啶的革兰氏阴性杆菌来自粪便植物群，杂交实验表明，25%的耐甲氧苄氨嘧啶菌株，（357个中的90个）分离株不能与1、2b、3、5、6、7、8、9、10和12型二氢叶酸还原酶的特异性寡核苷酸探针杂交，随后从这些分离株中的一个质粒携带的甲氧苄啶抗性基因的克隆和测序揭示了一个新的二氢叶酸还原酶基因dfr 13，其作为以位点特异性方式整合在1类整合子中的盒出现，该基因产物与dfr 12具有84%的氨基酸同一性，并表现出与dfr 12相似的甲氧苄啶抑制谱。用对该基因具有特异性的寡核苷酸探针进行的基因探测实验表明，不与其它二氢叶酸还原酶的探针杂交的分离株中有12.3%（44/357）与该探针杂交。紧接着dfr 13的下游，鉴定了一个新的盒，即编码链霉素-壮观霉素抗性的AADA类氨基糖苷类抗性基因[ANT（3 "）（9）-I]。该基因与共有aadA1（ant（3 "）-Ia）具有57%的同一性，并被称为aadA4（ant（3"）-Id）。aadA4盒的3 '端被IS26截短，其与截短形式的Tn3邻接。在同一质粒pUK2381上，IS26的第二个拷贝与sul2缔合，这表明整合酶和转座酶活性在抗生素抗性基因dfr 13、aadA 4、bla（TEM-1）和sul2的排列和传播中起主要作用。
In a previous survey of 357 trimethoprim-resistant isolates of aerobic gram-negative bacteria from commensal fecal flora, hybridization experiments showed that 25% (90 of 357) of the isolates failed to hybridize to specific oligonucleotide probes for dihydrofolate reductase types 1, 2b, 3, 5, 6, 7, 8, 9, 10, and 12, Subsequent cloning and sequencing of a plasmid-borne trimethoprim resistance gene from one of these isolates revealed a new dihydrofolate reductase gene, dfr13, which occurred as a cassette integrated in a site-specific manner in a class 1 integron, The gene product shared 84% amino acid identity with dfr12 and exhibited a trimethoprim inhibition profile similar to that of dfr12. Gene probing experiments with an oligonucleotide probe specific for this gene showed that 12.3% (44 of 357) of the isolates which did not hybridize to probes for other dihydrofolate reductases hybridized to this probe. Immediately downstream of dfr13, a new cassette, an aminoglycoside resistance gene of the class AADA [ANT(3 ")(9)-I], which encodes streptomycin-spectinomycin resistance, was identified. This gene shares 57% identity with the consensus aadA1 (ant(3 ")-Ia) and has been called aadA4 (ant(3 ")-Id), The 3' end of the aadA4 cassette was truncated by IS26, which was contiguous with a truncated form of Tn3, On the same plasmid, pUK2381, a second copy of IS26 was associated with sul2, which suggests that both integrase and transposase activities have played major roles in the arrangement and dissemination of antibiotic resistance genes dfr13, aadA4, bla(TEM-1), and sul2.