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[Correlation between methicillin-resistance and resistance to fluoroquinolones in Staphylococcus aureus and
V Cafiso1, F Campanile, S Borbone
1Dipartimento di Scienze Microbiologiche e Scienze Ginecologiche, Catania.
Abstract:
Fluoroquinolones resistance in Staphylococci is associated to point mutations in grlA (80,84 and 116) grlB, gyrA (84,88) and gyrB genes. Almost all MRSA strains are ciprofloxacin and levofloxacin resistant while, in a lesser degree, MRCoN staphylococci show to be resistant to levofloxacin. This observation made possible to predict a different correlation between methicillin-resistance and the resistance to FQs in this two different species. In this study, we compare genomic analysis of S. aureus and S. epidermidis with the resistance to FQs. Our results show that strains of MRSA are distributed in 4 different PFGE-types while 12 MRSE strains are distributed in 9. MRSA resistant to FQs showed a unique PFGE pattern; on the contrary of FQs susceptible MRSA and MSSA. Furthermore mecA and gyrA genes are located in the same SmaI fragment in MRSA and in different in MRSE. MSSE and MRSE show more ClaI/mecA polymorphisms than MRSA. All this data confirm the clonal origin of MRSA and show that FQs resistance is linked to the presence of mec locus and both clonally spread. On the contrary in MRSE FQs-resistance is independent from MR and arise with the normal frequence of antibiotic induction.
Insights
Fluoroquinolone resistance in Staphylococcus aureus (MRSA) is linked to specific gene mutations and clonal spread. In contrast, methicillin-resistant Staphylococcus epidermidis (MRSE) exhibits fluoroquinolone resistance independently of methicillin resistance.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Context:
- Fluoroquinolone (FQ) resistance in Staphylococci is a growing public health concern.
- Resistance mechanisms involve point mutations in gyrA, gyrB, grlA, and grlB genes.
- Methicillin-resistant Staphylococcus aureus (MRSA) and Methicillin-resistant Coagulase-negative Staphylococci (MRCoNS) display varying FQ resistance patterns.
Purpose:
- To compare the genomic basis of FQ resistance in Staphylococcus aureus (MRSA) and Staphylococcus epidermidis (MRSE).
- To investigate the correlation between methicillin resistance and FQ resistance in these two species.
Summary:
- Genomic analysis revealed distinct Pulsed-Field Gel Electrophoresis (PFGE) patterns for MRSA and MRSE strains.
- MRSA strains resistant to FQs exhibited a unique PFGE pattern, unlike susceptible strains.
- In MRSA, mecA and gyrA genes were located on the same SmaI fragment, suggesting clonal spread of FQ resistance linked to the mec locus.
- Conversely, FQ resistance in MRSE was independent of methicillin resistance and arose through spontaneous mutation.
Impact:
- This study elucidates the distinct evolutionary pathways of FQ resistance in MRSA and MRSE.
- Understanding these differences is crucial for developing targeted antimicrobial strategies.
- Confirms the clonal dissemination of FQ resistance in MRSA, highlighting the importance of infection control measures.