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Updated: May 12, 2025
A Fluorescence-based Method to Study Bacterial Gene Regulation in Infected Tissues
Published on: February 19, 2019
Genomic insights into the spread of methicillin-resistant Staphylococcus aureus involved in ear infections
Zhewei Sun1, Jinhong Chen2,3, Chunhong Liu4
1Department of Laboratory Medicine, Shanghai Medical College, Huashan Hospital, Fudan University, Shanghai, 200040, China.
Background:
Methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen causing ear infections. However, genomic epidemiology and determinants influencing transmission of ear infections associated MRSA (EIA-MRSA) in community remain unknown.
Methods:
In 2020-2021, 105 EIA-MRSA isolates were collected and sequenced from outpatients across different households in Shanghai, China. Antimicrobial susceptibility testing, core genome MLST, and phylodynamic analyses were conducted to characterize EIA-MRSA dissemination.
Results:
Quinolone resistance was identified as a risk factor for EIA-MRSA spread (OR 9, [95% CI 3-31]). The ST764 clone and two subclones of ST22-PT hypervirulent clone have developed an extensive quinolone-resistant (eQR) phenotype, conferring additional resistance to advanced quinolones due to the accumulation of four mutations in gyrA (S84L and either S85P, E88K, or E88G) and parC (S80F and either E84K or E84G). These ST764- and ST22-PT-eQR isolates were highly transmissible and showed increased resistance to other commonly used antimicrobials, posing potential high-risk clones. The eQR phenotype may be inherent to the ST764 lineage, which emerged in the late 1980s, coinciding with the widespread fluoroquinolone usage. The ST22-PT-eQR subclones emerged in around 2017 and are accumulating resistance genes.
Conclusion:
Vigilance is crucial for eQR high-risk clones, particularly the convergent ST22-PT-eQR subclones that accumulate resistance and virulence traits, posing risks for ear infections.
Clinical Trial Number:
Not applicable.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) causing ear infections is spreading due to quinolone resistance. High-risk clones like ST764 and ST22-PT-eQR show increased transmissibility and antimicrobial resistance.
Area of Science:
- Microbiology and Infectious Diseases
- Genomic Epidemiology
- Antimicrobial Resistance
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) is a significant cause of community-acquired ear infections.
- The genomic epidemiology and transmission dynamics of ear infection-associated MRSA (EIA-MRSA) remain poorly understood.
Purpose of the Study:
- To investigate the genomic characteristics and transmission patterns of EIA-MRSA in Shanghai, China.
- To identify risk factors and molecular determinants associated with EIA-MRSA spread.
Main Methods:
- Collection and whole-genome sequencing of 105 EIA-MRSA isolates from outpatients (2020-2021).
- Antimicrobial susceptibility testing, core genome multilocus sequence typing (MLST), and phylodynamic analyses were performed.
- Risk factors for EIA-MRSA dissemination were assessed.
Main Results:
- Quinolone resistance was a significant risk factor for EIA-MRSA spread (OR 9).
- Specific clones (ST764 and ST22-PT) developed extensive quinolone resistance (eQR) via mutations in gyrA and parC, conferring resistance to advanced quinolones.
- These eQR isolates exhibited high transmissibility and broader antimicrobial resistance, indicating potential high-risk clones.
Conclusions:
- Vigilance is essential for monitoring eQR high-risk MRSA clones, especially convergent ST22-PT-eQR subclones.
- These subclones accumulate resistance and virulence traits, posing an ongoing risk for ear infections.
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