Aminoglycoside Resistance in Enterococci

描述（由申请人提供）：肠球菌是美国医院感染中最常见的细菌之一。严重肠球菌感染的最佳抗菌治疗需要使用细胞壁活性剂（如氨苄西林或万古霉素）与氨基糖苷的协同组合，从而产生对肠球菌的杀菌活性。然而，许多肠球菌菌株获得了编码氨基糖苷修饰酶的氨基糖苷抗性基因，从而消除了这种协同杀菌作用。因此，在许多医疗中心，对氨基糖苷类的耐药性已成为主要的治疗挑战，阻碍了对大多数肠球菌感染的最佳治疗。肠球菌对临床上重要的氨基糖苷庆大霉素的高耐药是由APH（2”）酶介导的。我们建议对这些氨基糖苷磷酸转移酶进行详细的研究：(1)进行动力学研究和研究这些氨基糖苷修饰酶的化学机制；(2)研究保守氨基酸残基在催化机制中的作用；(3)研究其中一种肠球菌酶向更高水平和更广泛的氨基糖苷耐药方向的进化。更清楚地了解这些酶与其底物（氨基糖苷和ATP辅助因子）之间的相互作用，以及酶的进化以产生更多样化的阵列，将有助于开发新的氨基糖苷，无论是作为酶的不良底物还是作为酶抑制剂，以克服这些酶赋予的抗性。这些肠球菌氨基糖苷磷酸转移酶中的一种向更高水平和更广泛的氨基糖苷耐药的演变，将使预测哪种氨基糖苷抗生素在未来更有可能在对其他氨基糖苷的耐药演变中保持其活性。在这两个方向中的任何一个方面取得进展都将是治疗严重肠球菌感染的重要进展。有效治疗耐药肠球菌引起的严重感染已成为一项重大的临床挑战。

DESCRIPTION (provided by applicant): Enterococci are among the most common bacteria isolated in nosocomial infections in the United States. Optimal antimicrobial therapy for serious enterococcal infections requires the use of synergistic combinations of a cell wall-active agent, such as ampicillin or vancomycin, with an aminoglycoside, which results in bactericidal activity against enterococci. However, many enterococcal strains have acquired aminoglycoside resistance genes that encode aminoglycoside-modifying enzymes, which eliminate this synergistic bactericidal effect. Thus, in many medical centers resistance to aminoglycosides has emerged as a major therapeutic challenge, precluding optimal therapy for the majority of enterococcal infections. High-level resistance to the clinically important aminoglycoside gentamicin in enterococci is mediated by APH(2") enzymes. We propose to study these aminoglycoside phosphotransferases in detail by (1) performing kinetics studies and investigating chemical mechanisms of these aminoglycoside-modifying enzymes; (2) investigating the roles that conserved amino acid residues play in the catalytic mechanism; and (3) studying evolution of one of these enterococcal enzymes toward higher levels and broader spectrums of aminoglycoside resistance. A clearer understanding of the interaction between these enzymes and their substrates (both aminoglycosides and the ATP cofactor), and of the evolution of the enzymes to produce a more diverse array would facilitate the development of novel aminoglycosides, either as poor substrates of the enzymes or as enzyme inhibitors, to overcome resistance conferred by these enzymes. The evolution of one of these enterococcal aminoglycoside phosphotransferases toward higher levels and broader spectrums of aminoglycoside resistance will enable predictions of which aminoglycoside antibiotics are more likely to retain their activity in the future as resistance evolves toward other aminoglycosides. Progress in either of these directions would be an important advance in the treatment of serious enterococcal infections. Effective treatment of serious infections caused by antibiotic-resistant enterococci has become a major clinical challenge. We propose to study mechanisms of resistance in enterococci to a class of antibiotics called the aminoglycosides. Results from our study will help in the development of new antibiotics and approaches to treat enterococcal infections, which are emerging rapidly as a serious threat to public health.