Molecular characterization of chromosomal class C β-lactamase and its regulatory gene in Ochrobactrum anthropi
Molecular characterization of chromosomal class C β-lactamase and its regulatory gene in Ochrobactrum anthropi
复制标题
DOI：
10.1128/aac.45.8.2324-2330.2001
复制
发表时间：
2001-08-01
影响因子：
4.9
通讯作者：
Arlet, G
中科院分区：
文献类型：
--
作者：
Nadjar, D;Labia, R;Arlet, G
人类嗜铬杆菌（Ochrobactrum anthropi），以前被称为CDC Vd组，是一种产生氧化酶，革兰氏阴性，专需氧，非乳糖发酵的低毒力杆菌，偶尔引起人类感染。除亚胺培南外，它对所有β -内酰胺类药物都有高度耐药性。青霉素、氨曲南和大多数头孢菌素（包括头孢噻肟和头孢他啶）的mic值为100 ~ 128马克/毫升，头孢吡肟的mic值为64 ~ 100 ~ 128马克/毫升。将临床菌株O. amthropi SLO74基因组DNA的限制性内切片段插入pBK-CMV中，克隆出ampR和ampC两个基因，得到重组质粒pBK-OA1。该无性系对β -内酰胺类药物的耐药模式与亲本菌株相似，但对头孢吡肟（MIC, 0.5 mug/ml）的耐药模式不同。推导出的AmpC β -内酰胺酶（pI, 8.9）的氨基酸序列与其他染色体编码和质粒编码的C类β -内酰胺酶的序列同源性仅为41% ~ 52%，该β -内酰胺酶的动力学特性是该类β -内酰胺酶的典型特征。在ampC基因的上游，ampR基因编码一种蛋白质，其序列与其他ampR蛋白相同46%至62%，并且具有典型的Lys-R家族转录激活因子的氨基末端dna结合域。6株参考菌株的ampC基因的氨基酸序列与临床菌株的相同度仅为96 ~ 99%。从菌株SLO74中鉴定出的β -内酰胺酶命名为OCH-1（基因，bla(OCH-I)）。
Ochrobactrum anthropi, formerly known as CDC group Vd, is an oxidase-producing, gram-negative, obligately aerobic, non-lactose-fermenting bacillus of low virulence that occasionally causes human infections. It is highly resistant to all beta -lactams except imipenem, A clinical isolate, SLO74, and six reference strains were tested. MICs of penicillins, aztreonam, and most cephalosporins tested, including cefotaxime and ceftazidime, were > 128 mug/ml and of cefepime were 64 to > 128 mug/ml. Clavulanic acid was ineffective and tazobactam had a weak effect in association with piperacillin, Two genes, ampR and ampC, were cloned by inserting restriction fragments of genomic DNA, from the clinical strain O. amthropi SLO74 into pBK-CMV to give the recombinant plasmid pBK-OA1. The pattern of resistance to beta -lactams of this clone was similar to that of the parental strain, except for its resistance to cefepime (MIC, 0.5 mug/ml). The deduced amino acid sequence of the AmpC beta -lactamase (pI, 8.9) was only 41 to 52% identical to the sequence of other chromosomally encoded and plasmid-encoded class C beta -lactamases, The kinetic properties of this beta -lactamase were typical for this class of beta -lactamases. Upstream from the ampC gene, the ampR gene encodes a protein with a sequence that is 46 to 62% identical to those of other AmpR proteins and with an amino-terminal DNA-binding domain typical of transcriptional activators of the Lys-R family. The deduced amino acid sequences of the ampC genes of the six reference strains mere 96 to 99% identical to the sequence of the clinical strain. The beta -lactamase characterized from strain SLO74 nas named OCH-1 (gene, bla(OCH-I)).