Aminoglycoside Resistance in Enterococcus

描述（由申请人提供）：肠球菌是美国医院感染中分离的最常见细菌之一。严重肠球菌感染的最佳抗微生物治疗需要使用细胞壁活性剂（如氨苄青霉素或万古霉素）与氨基糖苷类的协同组合，这导致对肠球菌的杀菌活性。然而，许多肠球菌菌株已获得编码氨基糖苷类修饰酶的氨基糖苷类耐药基因，其消除了这种协同杀菌作用。因此，在许多医疗中心，对氨基糖苷类抗生素的耐药性已经成为一个主要的治疗挑战，排除了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类庆大霉素的高度耐药是由APH（2”）酶介导的。我们建议详细研究这些氨基糖苷磷酸转移酶（1）进行动力学研究，并调查这些氨基糖苷修饰酶的化学机制;（2）调查保守的氨基酸残基在催化机制中发挥的作用;和（3）研究这些肠球菌酶之一的进化向更高水平和更广泛的氨基糖苷耐药谱。更清楚地了解这些酶与其底物（氨基糖苷类和ATP辅因子）之间的相互作用，以及酶产生更多样化阵列的演变，将有助于开发新的氨基糖苷类，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类磷酸转移酶之一向更高水平和更宽谱的氨基糖苷类耐药性的演变将使预测哪些氨基糖苷类抗生素更有可能在未来保持其活性，因为耐药性向其他氨基糖苷类演变。在这两个方向中的任何一个方面的进展都将是严重肠球菌感染治疗的重要进展。有效治疗耐药肠球菌引起的严重感染已成为临床的主要挑战。 我们建议研究肠球菌对氨基糖苷类抗生素的耐药机制。我们的研究结果将有助于开发新的抗生素和治疗肠球菌感染的方法，肠球菌感染正在迅速成为对公共卫生的严重威胁。

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.