ampD-ampR调节基因与阴沟肠杆菌AmpC酶表达关系的研究

为了解ampD ampR调节基因与阴沟肠杆菌AmpC酶表达的关系 ,对 58株阴沟肠杆菌采用表型筛选法初筛 ,PCR法扩增AmpC酶的调节基因ampD和ampR ,并对部分PCR产物进行克隆测序。表型筛选结果显示 :去阻遏高产突变株为 50株 ,高度诱导产酶株为 3株。PCR法扩增目的基因片段显示 ,4 9株携带ampD基因 ,51株携带ampR基因。对其中 15株细菌的ampD基因和ampR基因进行克隆测序 ,发现 3株高度诱导型中 2株ampD基因存在 95位氨基酸的突变位点 ,而ampR基因未发现突变位点 ;12株去阻遏高产型中 ,8株ampD基因存在羧基端可疑的突变位点 ,5株ampR基因存在可疑的突变位点。结果提示 :ampD蛋白羧基端的氨基酸缺失或替代可能与AmpC酶的去阻遏表达有关 ,ampR基因的突变位点可能影响AmpC酶的去阻遏表达

Relationship between Expression of AmpC Beta-lactamase in Enterobacter Cloacae and ampD-ampR Regulatory Gene

The aim was to investigate the relationship between the expression of AmpC beta -lactamase i n Enterobacter cloacae and ampD-ampR regulatory gene. Phenotype screening test, PCR amplification, gene clone and DNA sequencings were performed in the 58 stra ins of Enterobacter cloacae. From the 58 strains of Enterobacter cloacae, the nu mberog de repressed strains were 50 and that of hyperinducible mutant strains were 3, resp ecti vely. 49 of the 58 strains harbored bla ampD gene and 51 of 58 strains harb ored bla_ampR gene. The results of bla_ampD gene sequencings indicated t hat hyperinducible mutant strains had an amino acid change in 95 codon(Try-95→Arg) and eight of the derepressed strains had amino acid substitutions or deletion i n the carboxy-terminal of ampD. The results of bla_ampR gene sequencin gs i ndicated that only five of the derepressed strains had the suspicious mutants in the ampR gene. The deletion and amino acid substitutions in the carboxy-termin al of ampD may result in the stably depressed expression of AmpC beta-lactamase in Enterobacter cloacae. The amino acid substitutions of ampR maybe influence t he expression of AmpC beta-lactamase.