Related Experiment Video
Updated: May 27, 2025
Stress-induced Antibiotic Susceptibility Testing on a Chip
Published on: January 8, 2014
Diversity in Adaptive Evolution of Methicillin-Resistant Staphylococcus aureus Clinical Isolates Under Exposure to
Tala Han1, Ting Jia1, Junrui Wang1,2
1Department of Laboratory Medicine, Affiliated Hospital of Inner Mongolian Medical University, Hohhot, 010050, People's Republic of China.
Background:
Linezolid resistance in methicillin-resistant Staphylococcus aureus (MRSA) was reported frequently in recent years, but the mechanism underlying this process was less reported, especially for clinical isolates with different genetic background. Thus, this study aims to explore the adaptive evolution characteristics underlying linezolid resistance in MRSA clinical isolates exposed to continuous induction stress of linezolid in vitro.
Methods:
The in vitro susceptibility of 1032 MRSA clinical isolates to linezolid was detected using commercial VITEK-2 equipment via broth microdilution. MRSA isolates with different minimum inhibitory concentration (MIC) values for linezolid were randomly selected to perform the assay of adaptive laboratory evolution with sub-inhibitory concentrations of linezolid. Polymerase chain reaction assays and sequencing techniques were performed to detect well-known molecular determinants related to linezolid resistance, including the expression of optrA and cfr, mutations of 23S rRNA gene and ribosomal protein (L3, L4, L22) encoding genes (rplC, rplD, rplV).
Results:
After induction with sequentially increasing concentrations of linezolid, all four MRSA strains (L914, L860, L1096, and L2875) evolved into linezolid-resistant strains over various induction times (480, 384, 288, and 240 h) and universally formed small colony variants. A new mutation in the domain V region of 23S rRNA gene (C2404T) and one mutation in amino acid sequences of ribosomal protein (Met208Thr) were firstly identified among linezolid-resistant strains. Except G2576T mutations in 23S rRNA gene, the distribution of other mutations (A2451T, T2504A, C2404T, T2500A, G2447T) exhibited obvious strain heterogeneity. Furthermore, as the MIC to linezolid increased, the copy numbers of point mutations in the V region of 23S rRNA gene increased correspondingly.
Conclusion:
Strain-specific evolution of resistance to linezolid among MRSA clinical isolates was firstly identified in this study. MRSA isolates with higher MICs for linezolid evolved more easily into resistant ones, which calls for precise monitoring of linezolid resistance levels in patients receiving treatment for MRSA infections with linezolid.
Insights
This study reveals strain-specific adaptive evolution leading to linezolid resistance in methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates. Higher initial linezolid minimum inhibitory concentrations (MICs) correlated with faster resistance development, underscoring the need for careful patient monitoring.
Area of Science:
- Microbiology
- Molecular Biology
- Antimicrobial Resistance
Background:
- Linezolid resistance in methicillin-resistant Staphylococcus aureus (MRSA) is a growing concern.
- Mechanisms of linezolid resistance, particularly in diverse clinical isolates, require further elucidation.
- Understanding adaptive evolution is crucial for combating emerging resistance.
Purpose of the Study:
- To investigate the adaptive evolution of linezolid resistance in MRSA clinical isolates.
- To explore the genetic mechanisms underlying this resistance under continuous linezolid exposure.
Main Methods:
- Susceptibility testing of 1032 MRSA isolates to linezolid using broth microdilution.
- Laboratory evolution assays with sub-inhibitory linezolid concentrations on selected MRSA strains.
- Detection of known resistance determinants (optrA, cfr, 23S rRNA, and ribosomal protein gene mutations) via PCR and sequencing.
Main Results:
- All four tested MRSA strains evolved linezolid resistance, forming small colony variants.
- Novel mutations (C2404T in 23S rRNA, Met208Thr in ribosomal protein) were identified.
- Strain-specific heterogeneity in mutation distribution was observed, with increased 23S rRNA mutation copy numbers correlating with higher linezolid MICs.
Conclusions:
- This study demonstrates strain-specific adaptive evolution of linezolid resistance in MRSA.
- MRSA isolates with higher baseline linezolid MICs are more prone to developing resistance.
- Precise monitoring of linezolid resistance levels in patients is essential.
More Related Videos
Related Concept Videos
01:31Defense Against Bacterial Pathogens
Phagocytes
Phagocytes are the frontline soldiers of the immune system. They include neutrophils and macrophages. Neutrophils are the most abundant type of white blood cell and are quickly mobilized to the site of infection. Macrophages are larger cells that patrol...
00:57Antibiotic Selection