β-lactamase genes of the penicillin-susceptible Bacillus anthracis sterne strain
β-lactamase genes of the penicillin-susceptible Bacillus anthracis sterne strain
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DOI：
10.1128/jb.185.3.823-830.2003
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发表时间：
2003-02-01
影响因子：
3.2
通讯作者：
Koehler, TM
中科院分区：
文献类型：
--
作者：
Chen, YH;Succi, J;Koehler, TM
对青霉素和其他β -内酰胺类化合物的敏感性是炭疽芽孢杆菌的共同特征。-内酰胺类药物，特别是青霉素，已在世界范围内用于治疗人类炭疽。尽管如此，对临床和土壤来源菌株的调查显示，在检测的分离株中有2%至16%对青霉素G耐药。细菌对β -内酰胺类药物的耐药性通常是由一种或多种β -内酰胺酶的产生介导的，这种酶能水解β -内酰胺环，使抗菌药物失活。在这里，我们报告了两种β -内酰胺酶（bla）基因在青霉素敏感的炭疽杆菌斯特恩菌株的存在。我们通过大肠杆菌功能克隆鉴定了bla1。bla1是一个927个核苷酸（nt）的基因，其编码的蛋白与蜡样芽孢杆菌I型β -内酰胺酶基因的同源性为93.8%。第二个基因bla2是通过在基因组研究所未完成的炭疽杆菌染色体序列数据库中搜索预测编码β -内酰胺酶的开放阅读框（orf）而确定的。我们发现部分ORF编码的蛋白质与蜡样芽孢杆菌I型β -内酰胺酶的羧基末端有显著的相似性。利用反相PCR技术克隆了部分ORF 5′端附近的DNA。bla2是一个768-nt基因，预计编码一种与蜡样芽孢杆菌II型酶具有92%同源性的蛋白。bla1和bla2基因赋予了大肠杆菌对氨苄青霉素的耐药性。和枯草芽孢杆菌在这些物种中单独克隆时。不同抗菌剂对大肠杆菌克隆的mic分析表明，两种β -内酰胺酶基因对大肠杆菌具有不同的敏感性；Bla1是一种青霉素酶，而bla2似乎是一种头孢菌素酶。含有bla启动子- lacz转录融合物的蜡样芽孢杆菌群物种的β -半乳糖苷酶活性表明，bla1在炭疽芽孢杆菌、蜡样芽孢杆菌和苏云金芽孢杆菌中转录较差。bla2基因在蜡样芽孢杆菌和苏云金芽孢杆菌中强表达，在炭疽芽孢杆菌中弱表达。综上所述，这些数据表明，炭疽芽孢杆菌菌株的bla1和bla2基因编码不同类型的功能性β -内酰胺酶，但基因表达通常不足以赋予对β -内酰胺药物的抗性。
Susceptibility to penicillin and other beta-lactam-containing compounds is a common trait of Bacillus anthracis. beta-lactam agents, particularly penicillin, have been used worldwide to treat anthrax in humans. Nonetheless, surveys of clinical and soil-derived strains reveal penicillin G resistance in 2 to 16% of isolates tested. Bacterial resistance to beta-lactam agents is often mediated by production of one or more types of beta-lactamases that hydrolyze the beta-lactam ring, inactivating the antimicrobial agent. Here, we report the presence of two beta-lactamase (bla) genes in the penicillin-susceptible Sterne strain of B. anthracis. We identified bla1 by functional cloning with Escherichia coli. bla1 is a 927-nucleotide (nt) gene predicted to encode a protein with 93.8% identity to the type I beta-lactamase gene of Bacillus cereus. A second gene, bla2, was identified by searching the unfinished B. anthracis chromosome sequence database of The Institute for Genome Research for open reading frames (ORFs) predicted to encode beta-lactamases. We found a partial ORF predicted to encode a protein with significant similarity to the carboxy-terminal end of the type I beta-lactamase of B. cereus. DNA adjacent to the 5' end of the partial ORF was cloned using inverse PCR. bla2 is a 768-nt gene predicted to encode a protein with 92% identity to the B. cereus type II enzyme. The bla1 and bla2 genes confer ampicillin resistance to E. coli. and Bacillus subtilis when cloned individually in these species. The MICs of various antimicrobial agents for the E. coli clones indicate that the two beta-lactamase genes confer different susceptibility profiles to E. coli; bla1 is a penicillinase, while bla2 appears to be a cephalosporinase. The beta-galactosidase activities of B. cereus group species harboring bla promoter-lacZ transcriptional fusions indicate that bla1 is poorly transcribed in B. anthracis, B. cereus, and B. thuringiensis. The bla2 gene is strongly expressed in B. cereus and B. thuringiensis and weakly expressed in B. anthracis. Taken together, these data indicate that the bla1 and bla2 genes of the B. anthracis Sterne strain encode functional beta-lactamases of different types, but gene expression is usually not sufficient to confer resistance to beta-lactam agents.