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The mechanism of the beta-lactam resistance in Staphylococcus aureus

金黄色葡萄球菌β-内酰胺耐药机制

基本信息

批准号：
9885286
负责人：
Taeok Bae
金额：
$ 39.63万
依托单位：
INDIANA UNIV-PURDUE UNIV AT INDIANAPOLIS
依托单位国家：
美国
项目类别：
财政年份：
2020
资助国家：
美国
起止时间：
2020-08-01 至 2024-07-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9885286
关键词：
ATP-Dependent Proteases Affect Anti-Bacterial Agents Antibiotic Resistance Antibiotics Bacteria Bacterial Infections Binding Proteins Biological Assay Cell Wall Cell membrane Chromosomes Development Drug resistance Enzymes Genes Genome Goals Hypersensitivity Infection Lactams Mediating Membrane Methicillin Resistance Molecular Monobactams Mutagenesis Mutation Pathway interactions Penicillin-Binding Proteins Peptide Hydrolases Peptidoglycan Pharmaceutical Preparations Pharmacotherapy Phenotype Pneumonia Production Resistance Resistance development Role Sepsis Skin Tissue Soft Tissue Infections Staphylococcal Infections Staphylococcus aureus Staphylococcus aureus infection Suppressor Genes Suppressor Mutations Testing Therapeutic Agents Toxic Shock Syndrome base beta-Lactam Resistance beta-Lactams design enzyme activity genome sequencing infectious disease treatment lipoteichoic acid methicillin resistant Staphylococcus aureus minimal risk mutant novel novel therapeutics overexpression pathogenic bacteria protein function resistance mechanism resistance mutation resistant strain skin disorder transposon sequencing yeast two hybrid system

项目摘要

Project Summary Cell-wall targeting beta-lactam antibiotics are the largest group of antibacterial agents and have been the mainstay for treatment of bacterial infections. However, most beta-lactam antibiotics cannot be used for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections because MRSA produces a cell- wall synthesis enzyme PBP2A, which most beta-lactams cannot inactivate. Although PBP2A is the primary determinant of MRSA beta-lactam resistance, the overall beta-lactam resistance of MRSA is affected by additional bacterial factors such as FtsH, a protease in the cell membrane. Overexpression of FtsH makes MRSA sensitive specifically to beta-lactams. The beta-lactam-sensitizing effect of FtsH is due to its degradation of YpfP, an enzyme synthesizing the anchor molecule for lipoteichoic acid (LTA). The YpfP- degradation by FtsH causes the production of abnormally large LTA. On the other hand, increased production of normal LTA by deletion of the ftsH gene makes MRSA more resistant to beta-lactams. When the production of normal LTA is suppressed by inhibiting the production of the LTA synthesis enzyme LtaS, MRSA becomes hypersensitive to beta-lactams. Based on these results, this study hypothesizes that the large LTA lowers MRSA beta-lactam resistance by suppressing the enzyme activities of the cell-wall synthesis enzymes whereas the normal LTA is required for them. Even under the beta-lactam sensitizing conditions, MRSA can regain resistance to beta-lactams. Genome-sequencing of 26 such mutants showed that 16 genes are critical for MRSA beta-lactam resistance. The long-term goal of this project is to develop novel β-lactam potentiators against MRSA. The objective of this study is to understand how FtsH and the disturbance in LTA synthesis sensitize MRSA to β-lactams, and how MRSA regains β-lactam resistance. In aim 1, with the MRSA strains producing either the large LTA or reduced amount of the normal LTA, the cell wall synthesis steps affected by the LTA molecules will be determined. The effect of LTA on cell wall synthesis will be directly tested by a peptidoglycan-synthesis assay. Also, the bacterial two-hybrid analysis will determine whether the degradation of YpfP is modulated by FtsH-binding proteins. In aim 2, by generating each of the resistance mutations in the chromosome of MRSA, the mutations critical for MRSA β-lactam resistance will be determined. Also, transposon-mediated mutagenesis will identify the genes essential for MRSA to regain the β-lactam resistance. Finally, to test whether the roles of the 16 genes are universally conserved among S. aureus strains, resistant mutants will be identified from two more MRSA strains, and their genomes will be sequenced. Completion of this study will reveal the intricate network of the beta-lactam resistance regulators in MRSA and open the door to developing novel beta-lactam potentiators with minimal risk of resistance development in the treatment of MRSA infections. Such drugs are expected to reduce the burdens of antibiotic resistance.

项目总结