Regulation of P. aeruginosa PoxB Oxacillinase by AmpR and a Two-Component System

描述（由申请人提供）：囊性纤维化（CF）患者慢性铜绿假单胞菌感染的两个关键标志是海藻酸盐过量产生的粘液菌落的出现和抗生素耐药性的发展。CF患者中铜绿假单胞菌分离株中抗生素耐药性的迅速出现是由于体内选择过量产生AmpC -内酰胺酶（一种水解-内酰胺的酶）的菌株，这导致了发病率和死亡率。先前利用遗传和分子生物学技术研究P. aeruginosa中amp基因的调控导致鉴定出第二种内酰胺酶PoxB oxacillinase。我们发现ampC和poxB的表达都受到AmpR的控制，AmpR是转录调控因子LysR家族的成员。我们已经证明AmpR是一个全球性的转录调节剂，它调节许多毒性基因的表达，这些基因对建立慢性感染很重要。

DESCRIPTION (provided by applicant): Two critical hallmarks of chronic Pseudomonas aeruginosa infection in patients with cystic fibrosis (CF) are the appearance of alginate over-producing mucoid colonies and the development of antibiotic resistance. A rapid emergence of antibiotic resistance in P. aeruginosa isolates in CF patients due to in vivo selection of strains that overproduce AmpC ¿-lactamase, an enzyme that hydrolyzes the ¿-lactams, contributes to both morbidity and mortality. Previous studies investigating the regulation of the amp genes in P. aeruginosa using genetic and molecular biological techniques led to the identification of a second ¿-lactamase, PoxB oxacillinase. We showed that the expression of both ampC and poxB are under the control of AmpR, a member of the LysR family of transcriptional regulators. We have demonstrated that AmpR is a global transcriptional regulator which regulates expression of many virulent genes that are important for establishing chronic infections. Our long-term goal is to establish the regulatory circuit that exists between the amp and pox genes and their role in the development of resistance to ¿-lactams and the establishment of chronic infection. To date, we know very little about the molecular mechanisms that govern the expression of pox operon. The experiments proposed in this grant will extend our understanding as they will focus on (1) characterizing the poxAB operon and determining if AmpR regulation is by transcriptional derepression, and (2) determining if expression of the poxAB operon is regulated by a previously uncharacterized two-component system. These analyses will provide invaluable insight into the bacterial adaptation to the onslaught of antibiotics and the immune response. It will likely lead to novel therapeutic approaches in combating the persistent P. aeruginosa infection that ultimately leads to the untimely death of CF patients.