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Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
The Secondary Resistome of Methicillin-Resistant Staphylococcus aureus to β-Lactam Antibiotics
Nader Abdelmalek1, Sally Waheed Yousief1, Martin Saxtorph Bojer2
1Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy.
Abstract:
Background: Therapeutic strategies for methicillin-resistant Staphylococcus aureus (MRSA) are increasingly limited due to the ability of the pathogen to evade conventional treatments such as vancomycin and daptomycin. This challenge has shifted the focus towards novel strategies, including the resensitization of β-lactams, which are still used as first-line treatments for methicillin-susceptible Staphylococcus aureus (MSSA). To achieve this, it is essential to identify the secondary resistome associated with the clinically relevant β-lactam antibiotics. Methods: Transposon-Directed Insertion Site Sequencing (TraDIS) was employed to assess conditional essentiality by analyzing the depletion of mutants from a highly saturated transposon library of MRSA USA300 JE2 exposed to ½ minimal inhibitory concentration (MIC) of oxacillin or cefazolin. Results: TraDIS analysis led to the identification of 52 shared fitness genes involved in β-lactam resistance that are primarily linked to cell wall metabolism and regulatory systems. Among these, both known resistance factors and novel conditionally essential genes were highlighted. As proof of concept, transposon mutants corresponding to nine genes (sagB, SAUSA300_0657, SAUSA300_0957, SAUSA300_1683, SAUSA300_1964, SAUSA300_1966, SAUSA300_1967, SAUSA300_1692, and mazF) were grown in the presence of β-lactam antibiotics and their MICs were determined. All mutants showed significantly reduced resistance to β-lactam antibiotics. Conclusions: This comprehensive genome-wide investigation provides novel insights into the resistance mechanisms of β-lactam antibiotics, and suggests potential therapeutic targets for combination therapies with helper drugs.
Insights
Researchers identified 52 genes contributing to methicillin-resistant Staphylococcus aureus (MRSA) resistance against beta-lactam antibiotics. This discovery offers new targets for combination therapies to combat difficult-to-treat MRSA infections.
Area of Science:
- Microbiology
- Genomics
- Drug Discovery
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant therapeutic challenge due to resistance to vancomycin and daptomycin.
- Novel strategies are needed, including resensitizing bacteria to beta-lactam antibiotics, which remain effective against methicillin-susceptible Staphylococcus aureus (MSSA).
- Identifying the secondary resistome associated with beta-lactam antibiotics is crucial for developing new treatment approaches.
Purpose of the Study:
- To identify genes conferring resistance to beta-lactam antibiotics in MRSA.
- To explore novel therapeutic targets for combination therapies against MRSA.
- To understand the genetic basis of beta-lactam resistance in MRSA.
Main Methods:
- Transposon-Directed Insertion Site Sequencing (TraDIS) was used to analyze gene essentiality in MRSA USA300 JE2.
- Mutant depletion was assessed under exposure to sub-inhibitory concentrations (½ MIC) of oxacillin and cefazolin.
- The minimal inhibitory concentrations (MICs) of specific gene mutants were determined in the presence of beta-lactam antibiotics.
Main Results:
- Fifty-two shared fitness genes involved in beta-lactam resistance were identified, primarily related to cell wall metabolism and regulatory systems.
- Both known resistance factors and novel conditionally essential genes were highlighted.
- Mutants with disruptions in nine selected genes (sagB, SAUSA300_0657, SAUSA300_0957, SAUSA300_1683, SAUSA300_1964, SAUSA300_1966, SAUSA300_1967, SAUSA300_1692, and mazF) exhibited significantly reduced resistance to beta-lactam antibiotics.
Conclusions:
- This genome-wide study provides new insights into beta-lactam antibiotic resistance mechanisms in MRSA.
- The identified genes represent potential therapeutic targets for combination therapies.
- These findings could lead to the development of novel strategies to overcome MRSA resistance.
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