Newly Identified mechanisms of Ceftaroline Resistance in MRSA Clinical Strains

新发现的 MRSA 临床菌株头孢洛林耐药机制

• 批准号: 9320334
• 负责人: ADRIANA E ROSATO
• 金额: $ 68.36万
• 依托单位: METHODIST HOSPITAL RESEARCH INSTITUTE
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-16 至 2018-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9320334
• 关键词: Active Sites; Address; Affinity; Amino Acid Substitution; Amino Acids; Anti-Bacterial Agents; Antibiotic Resistance; Antibiotics; Binding; Carbapenems; Cell Wall; Cephalosporins; Chronic; Chronic Disease; Clinical; Code; Cystic Fibrosis; DNA; DNA biosynthesis; Data; Development; Diabetes Mellitus; Dimerization; Disease; Employee Strikes; Evolution; Exposure to; FDA approved; Gatekeeping; Genes; Genetic; Genetic Determinism; Goals; Greece; Health; Hospitals; Human; Imipenem; Incidence; Individual; Infection; Intermediate resistance; Life; Link; Mediating; Metabolic; Mismatch Repair; Molecular; Mutation; Organism; Osteomyelitis; Patients; Penicillin-Binding Proteins; Penicillins; Peptidyltransferase; Phenotype; Pneumonia; Predisposition; Research; Resistance; Role; Sequence Analysis; Signal Pathway; Skin Tissue; Soft Tissue Infections; Spain; Staphylococcus aureus; Thailand; Therapeutic; Thymidylate Synthase; Time; Treatment Failure; antimicrobial; base; beta-Lactam Resistance; beta-Lactams; community setting; cystic fibrosis patients; genome sequencing; improved; methicillin resistant Staphylococcus aureus; novel; novel therapeutics; pathogen; pressure; resistant strain; whole genome

 DESCRIPTION (provided by applicant): Methicillin-resistant Staphylococcus aureus (MRSA) is an important infectious human pathogen responsible for diseases ranging from skin and soft tissue infections to life threatening diseases. Emerging research has demonstrated that MRSA infections have a significant clinical impact on individuals with chronic underlying diseases such as cystic fibrosis (CF), diabetes and osteomyelitis in where antibiotic pressure and metabolic adaptions may favor the adaptability of S.aureus to establish long persistence. Ceftaroline (CPT) is the only FDA-approved cephalosporin targeting PBP2a with strong antibacterial activity including MRSA. We have examined the molecular basis of both CPT-high(CPT-HR) and -intermediate (CPT-IR) resistant MRSA strains isolated for the first time in the USA displaying MICs to CPT of 2-8 μg/ml and ≥32 μg/ml, respectively. Although mutations in the mecA gene have been associated to CPT resistance, the molecular mechanisms have not been fully elucidated. Our data suggest that the CPT-HR strain harbored three SNPs, two of them in the penicillin-binding pocket of PBP2a that result in replacement of amino acids directly acting as gatekeeper to the transpeptidase active site, while the third mutation localizes at the non-penicillin binding or dimerization domain. Related tochanges in mecA, non-synonymous mutations were also identified in pbp2. In addition, other relevant nonsynonymous SNPs were present in thyA (gene coding for the thymidylate synthase) and mutS and mutL (DNA mismatch repair) genes. Moreover, we determined that CPT-IR strains displayed a very significant increase in CPT-induced mecA expression that, accompanied with mutations in PBP2, together may interfere with CPT's ability to repress completely both PBP2a and PBP2a/PBP2 interactions. A common feature consistently found in CPT-IR and -HR strains was their high level of resistance to imipenem (IPM).This proposal intends to elucidate the molecular bases of CPT-HR and CPT-IR in MRSA clinical strains, and to provide new therapeutic antimicrobial combinations for the treatment of CPT-resistant MRSA infections. The Specific Aims of this proposal are: Specific Aim#1 To investigate the mechanistic significance of PBP2 perturbations in CPT-resistance Specific Aim #2 To define S. aureus metabolic adaptations linked to thyA mutations during development of CPT-resistance. Specific Aim #3 To identify the genetic determinates and analyze the role of carbapenems in the acquisition of CPT-resistance in clinical MRSA strains.

 描述（由申请人提供）：耐甲氧西林金黄色葡萄球菌 (MRSA) 是一种重要的传染性人类病原体，可导致从皮肤和软组织感染到危及生命的疾病，新兴研究表明，MRSA 感染对个体具有重大的临床影响。患有慢性基础疾病，如囊性纤维化（CF）、糖尿病和骨髓炎，其中抗生素压力和代谢适应可能有利于金黄色葡萄球菌的适应性，以建立长期的持久性。头孢洛林 (CPT) 是 FDA 批准的唯一一种针对 PBP2a 的头孢菌素，具有很强的抗菌活性，包括 MRSA。我们已经检查了针对 CPT 高 (CPT-HR) 和中 (CPT-IR) 耐药 MRSA 菌株的分子基础。尽管 mecA 基因发生突变，但在美国首次显示对 CPT 的 MIC 分别为 2-8 μg/ml 和 ≥32 μg/ml。尽管与 CPT 耐药性相关，但其分子机制尚未完全阐明，我们的数据表明 CPT-HR 菌株含有三个 SNP，其中两个位于 PBP2a 的青霉素结合袋中，导致直接替代氨基酸。转肽酶活性位点的看门人，而第三个突变位于非青霉素结合或二聚化结构域，与 mecA 的变化相关，还发现了非同义突变。此外，thyA（胸苷酸合酶基因编码）和 mutS 和 mutL（DNA 错配修复）基因中还存在其他相关的非同义 SNP。此外，我们确定 CPT-IR 菌株在 CPT 诱导下表现出非常显着的增加。 mecA 表达与 PBP2 突变一起可能会干扰 CPT 完全抑制 PBP2a 和 PBP2a/PBP2 相互作用的能力，这是一致发现的一个共同特征。 CPT-IR和-HR菌株的主要特点是对亚胺培南（IPM）具有高水平的耐药性。本提案旨在阐明CPT-HR和-HR在MRSA临床菌株中的分子基础，并为治疗提供新的治疗性抗菌组合。该提案的具体目标是： 具体目标#1 研究 PBP2 扰动在 CPT 耐药中的机制意义。目标 #2 确定 CPT 抗性发展过程中与 thyA 突变相关的金黄色葡萄球菌代谢适应。 具体目标 #3 确定遗传决定因素并分析碳青霉烯类在临床 MRSA 菌株获得 CPT 抗性中的作用。