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A new approach to establishing the set of phages for typing methicillin-resistant Staphylococcus aureus
A K Akatov1, V S Zueva, O A Dmitrenko
1Laboratory of Staphylococcal Infections, Gamaleya Research Institute of Epidemiology and Microbiology, Moscow, USSR.
Abstract:
A new approach to using experimental phages for typing methicillin-resistant S. aureus (MRSA) non-sensitive to the phages of International Basic Set (IBS) is described. The collection Includes phage 85, modified on a culture of MRSA, and 5 phages induced from MRSA strains isolated in clinics of Moscow in 1975-76. Firstly, the modified phage selects cultures according to the specific character of its restriction-modification system, then the induced phages differentiate the selected strains into 5 groups (1, 2, 3, 4, 5) based on the specificity of the prophages they contain. Group 1 strains can further be differentiated into 5 subgroups (A, B, C, D, E) by additional phages. Forty-one MRSA strains isolated in 1987-90 in various hospitals of Moscow showing no sensitivity to IBS phages, were lysed by the modified phage, 15 of them belonging to Group 2 and isolated in the traumatological hospital, 26 belonging to Group 1 and were circulating in the burn center. Twenty-three strains of Group 1 appertain to subgroup 1B and were isolated over a 4-year period from the burned surface of patients and from the throat of a medical staff carrier.
Insights
A novel phage typing method effectively identifies methicillin-resistant Staphylococcus aureus (MRSA) strains resistant to standard phages. This approach utilizes modified and induced phages for precise MRSA strain differentiation.
Area of Science:
- Microbiology
- Bacteriology
- Phage Therapy
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant public health threat.
- Existing phage typing methods, such as the International Basic Set (IBS), are insufficient for certain MRSA strains.
- Need for novel typing strategies to accurately characterize and track MRSA epidemiology.
Purpose of the Study:
- To develop and evaluate a new experimental phage typing approach for MRSA strains.
- To characterize MRSA strains non-sensitive to the International Basic Set (IBS) phages.
- To improve the differentiation and epidemiological surveillance of challenging MRSA isolates.
Main Methods:
- Utilized a modified experimental phage (phage 85) for initial MRSA strain selection based on restriction-modification systems.
- Employed five induced phages from historical MRSA isolates for differentiation into five primary groups.
- Further subdivided Group 1 strains into five subgroups (A-E) using additional phages.
Main Results:
- Successfully lysed 41 MRSA strains resistant to IBS phages using the modified phage.
- Classified 15 strains into Group 2 (isolated from a traumatological hospital) and 26 into Group 1 (from a burn center).
- Identified 23 Group 1 strains belonging to subgroup 1B, isolated over four years from burn patients and healthcare personnel.
Conclusions:
- The described experimental phage typing method is effective for classifying MRSA strains resistant to conventional IBS phages.
- This approach enhances the ability to differentiate and trace the circulation of specific MRSA strains in clinical settings.
- The findings contribute to improved epidemiological surveillance and control strategies for MRSA infections.