Phages for methicillin-resistant Staphylococcus aureus: an international trial

Area of Science:

• Microbiology
• Bacteriology
• Epidemiology

Background:

• The international phage set for Staphylococcus aureus typing shows reduced efficacy against methicillin-resistant strains (MRSA).
• National typing centers utilize local experimental phages to overcome limitations with the international set.
• There is a need to augment the international phage set for improved MRSA characterization.

Purpose of the Study:

• To define a phage set that augments the international typing set for Staphylococcus aureus.
• To evaluate the efficacy of locally isolated experimental phages in typing MRSA strains.
• To establish a more comprehensive phage-based surveillance system for MRSA.

Main Methods:

• Distribution of 42 experimental phages to 6 international centers.
• Testing of phages against 744 clinical isolates of MRSA.
• Selection and evaluation of a subset of 10 experimental phages.

Main Results:

• The use of experimental phages increased MRSA typability from 75% to 93%.
• The number of identifiable lytic patterns rose from 192 to 424 with the experimental set.
• A subset of 10 phages achieved 91% typability and yielded 370 distinct patterns.

Conclusions:

• Experimental phages significantly enhance the typing of MRSA strains.
• A selected subset of 10 phages shows high efficacy and is suitable for international trial.
• Augmenting the international phage set with these experimental phages improves global MRSA strain characterization and surveillance.