Gonococcal resistance to β-lactams and tetracycline involves mutation in loop 3 of the porin encoded at the penB locus
Gonococcal resistance to β-lactams and tetracycline involves mutation in loop 3 of the porin encoded at the penB locus
复制标题
DOI：
10.1128/aac.42.11.2799
复制
发表时间：
1998-11-01
影响因子：
4.9
通讯作者：
Ison, CA
中科院分区：
文献类型：
--
作者：
Gill, MJ;Simjee, S;Ison, CA
PenB是一种染色体突变，导致淋球菌对β-内酰胺类和四环素类药物耐药，降低对喹诺酮类药物的敏感性，它与孔蛋白基因(Por)连锁，需要MTR导致外排泵表达增加。将一株敏感的淋球菌(H1株)的染色体DNA转化为FA140株(Pena MTR penB；porin serovar IB1)，并将表达p-内酰胺酶的质粒进行接合转移，用Zimmermann和Rosselet(W.Zimmermann和A.Rosselet，Antimmicrob，Agents Chemther，12：368-372,1977)的方法产生用于测定青霉素平衡浓度的等基因菌株。在具有MTR和PenB表型的转化子中，青霉素的平衡浓度降低。对等基因的penB和penB(+)转化子的POR进行DNA序列分析，发现14个序列差异，其中9个差异导致氨基酸的变化。在大肠杆菌OmpF的孔收缩环3的假定淋球菌等价物中发现了三个氨基酸变化。其中两个突变(Gly-101-Ala-102-&Gt；Asp-Asp)导致POR环3的这个位置负电荷增加，将FA140株完整的por基因的聚合酶链式反应产物转化到H1-2株(Pena mtr；porin serovar IB-3)，得到的转化子具有与penB相关的抗生素敏感性表型，在染色体介导的青霉素耐药淋球菌临床分离株的环3中发现了penB样突变。我们的结论是，penB是POR环3上的一个突变，它降低了孔蛋白对亲水性抗生素的通透性，在淋球菌对青霉素和四环素的染色体耐药中发挥了重要作用。
penB is a chromosomal mutation that confers resistance to p-lactams and tetracyclines and reduced susceptibility to quinolones in Neisseria gonorrhoeae, It is linked to the porin gene (por) and requires the increased expression of an efflux pump due to mtr. Transformation of a susceptible gonococcus (strain H1) with chromosomal DNA from strain FA140 (penA mtr penB; porin serovar IB1) and conjugal transfer of a p-lactamase-expressing plasmid was used to produce isogenic strains for determination of equilibrium periplasmic penicillin concentrations by the method of Zimmermann and Rosselet (W. Zimmermann and A. Rosselet, Antimicrob, Agents Chemother, 12:368-372, 1977). In transformants with the Mtr and PenB phenotypes, equilibrium concentrations of penicillin were reduced. DNA sequence analysis of por from isogenic penB and penB(+) transformants revealed 14 sequence differences; nine of these differences resulted in amino acid changes. Three amino acid changes were found in the putative gonococcal equivalent of the pore-constricting loop 3 of Escherichia coli OmpF. Two of these changes (Gly-101-Ala-102-->Asp-Asp) result in an increased negative charge at this position in por loop 3, PCR products comprising the complete por gene from strain FA140 were transformed into strain H1-2 (penA mtr; porin serovar IB-3), with the resulting transformants having the antibiotic susceptibility phenotype associated with penB, penB-like mutations were found in loop 3 of clinical isolates of gonococci with chromosomally mediated resistance to penicillin. We conclude that penB is a mutation in loop 3 of por that reduces porin permeability to hydrophilic antibiotics and plays an important role in the development of chromosomally mediated resistance to penicillin and tetracycline in gonococci.