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Characterization of methicillin resistant Staphylococcus aureus strains by a set of MRSA phages
1Department of Microbiology, Maulana Azad Medical College, New Delhi.
Abstract:
A recently developed international set of phages for typing methicillin resistant Staphylococcus aureus (MRSA) was used to characterize 300 strains of MRSA. The results were compared to that of phage typing with conventional phages and reverse phage typing. The use of MRSA phages increased the percentage typability from 17.6 per cent with the conventional set to 45.6 per cent with MRSA set and the strains were recognised as five distinct phage pattern viz., 622, M3/M5, MR8/MR12/MR25, 30/33/38 and mixed group. Phage type 622 was the most prevalent. On reverse phage typing 73 per cent strains could be typed with most strains belonging to one pattern i.e., 83A complex with limited discrimination. These 83A strains were highly resistant to erythromycin (98%) and tetracycline (93%). Our results show that MRSA phages are more useful in increasing typability and discrimination between the strains as compared to the conventional phages, reverse phage typing, and antibiogramtyping.
Insights
A new international phage set significantly improves methicillin-resistant Staphylococcus aureus (MRSA) strain typing. This advanced method offers better discrimination compared to older techniques.
Area of Science:
- Microbiology
- Bacteriology
- Epidemiology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant public health threat.
- Accurate strain typing is crucial for epidemiological surveillance and infection control.
- Conventional phage typing methods have limitations in typability and discrimination.
Purpose of the Study:
- To evaluate a newly developed international set of phages for typing MRSA.
- To compare the efficacy of the new MRSA phage set against conventional phage typing and reverse phage typing.
- To assess the discriminatory power of the MRSA phage set for characterizing MRSA strains.
Main Methods:
- Characterization of 300 MRSA strains using the international MRSA phage set.
- Comparative analysis with conventional phage typing and reverse phage typing methods.
- Antibiogram typing was also performed for correlation.
Main Results:
- The MRSA phage set increased typability from 17.6% (conventional) to 45.6%.
- Five distinct phage patterns were identified: 622, M3/M5, MR8/MR12/MR25, 30/33/38, and mixed group, with 622 being most prevalent.
- Reverse phage typing achieved 73% typability, primarily identifying the 83A complex with limited discrimination; these strains showed high resistance to erythromycin and tetracycline.
Conclusions:
- The international MRSA phage set demonstrates superior performance in increasing typability and discrimination of MRSA strains.
- MRSA phages offer a more effective tool for MRSA characterization than conventional phages or reverse phage typing.
- The findings support the utility of the new MRSA phage set for enhanced epidemiological surveillance and outbreak investigations.