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Published on: May 5, 2016
Correlation between mazEF Toxin-Antitoxin System Expression and Methicillin Susceptibility in Staphylococcus aureus
Aya Abd El Rahman1, Yasmine El Kholy1, Rania Y Shash1
1Department of Medical Microbiology and Immunology, Faculty of Medicine, Cairo University, Cairo 11865, Egypt.
Abstract:
Methicillin resistance in Staphylococcus aureus has become prevalent globally. Moreover, biofilm-formation makes it more difficult to eradicate bacteria by antibiotics. The mazEF toxin-antitoxin system encodes for mazF, which acts as an endoribonuclease that cleaves cellular mRNAs at specific sequence motifs (ACA), and mazE, which opposes the mazF action. Our goal was to detect mazEF expression in methicillin-resistant S. aureus (MRSA) isolates compared with methicillin-sensitive S. aureus (MSSA) isolates and determine its relation to methicillin susceptibility as well as biofilm-formation. According to their susceptibility to cefoxitin disks, 100 S. aureus isolates obtained from patients admitted to Cairo University Hospitals were categorized into 50 MSSA and 50 MRSA according to their susceptibility to cefoxitin disks (30 µg). Antimicrobial susceptibility and biofilm-formation were investigated using the disk diffusion method and tissue culture plate method, respectively. Finally, using real-time PCR, mazEF expression was estimated and correlated to methicillin susceptibility and biofilm formation. Both MRSA and MSSA isolates showed the best sensitivity results with linezolid and gentamicin, where about 88% of MRSA isolates and 96% of MSSA isolates were sensitive to linezolid while 76% of MRSA isolates and 84% of MSSA isolates were sensitive to gentamicin. MRSA isolates were significantly more able to form biofilm than MSSA isolates (p-value = 0.037). The mazEF expression was significantly correlated to methicillin resistance in S. aureus (p-value < 0.001), but not to biofilm-formation.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) shows increased biofilm formation. The mazEF toxin-antitoxin system expression is linked to methicillin resistance but not biofilm production in S. aureus.
Area of Science:
- Microbiology
- Molecular Biology
- Antimicrobial Resistance
Background:
- Methicillin resistance in Staphylococcus aureus (MRSA) is a growing global health concern.
- Biofilm formation by S. aureus complicates antibiotic treatment and eradication strategies.
- The mazEF toxin-antitoxin system, involving MazF endoribonuclease and MazE antitoxin, regulates bacterial gene expression.
Purpose of the Study:
- To compare mazEF gene expression in MRSA versus methicillin-sensitive S. aureus (MSSA) isolates.
- To investigate the correlation between mazEF expression, methicillin susceptibility, and biofilm formation in S. aureus.
Main Methods:
- Categorization of 100 S. aureus isolates into 50 MRSA and 50 MSSA based on cefoxitin disk susceptibility.
- Assessment of antimicrobial susceptibility using the disk diffusion method.
- Evaluation of biofilm formation capacity via the tissue culture plate method.
- Quantification of mazEF gene expression using real-time PCR.
Main Results:
- MRSA isolates exhibited significantly higher biofilm formation capabilities compared to MSSA isolates (p=0.037).
- A significant correlation was observed between mazEF gene expression and methicillin resistance in S. aureus (p<0.001).
- No significant correlation was found between mazEF expression and biofilm formation.
Conclusions:
- The mazEF toxin-antitoxin system's expression is significantly associated with methicillin resistance in S. aureus.
- While MRSA strains show enhanced biofilm formation, mazEF expression does not appear to be a direct factor in this process.
- Further research may elucidate the precise role of mazEF in MRSA pathogenesis and antibiotic resistance mechanisms.
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