A New Approach to Establishing the Set of Phages for Typing Methicillin-ResistantStaphylococcus aureus

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.

Phage Therapy: What Have We Learned?

“…The structure of each phage and its infectivity for particular hosts are determined by the genome of this phage. The only host-determined features of a phage seem to be certain epigenetic modifications, namely host-specific DNA methylation patterns [ 191 , 192 ]. They strongly influence the efficiency of infection of new hosts by a phage, being responsible for the limitations of horizontal gene transfer by bacteriophages [ 86 , 191 , 193 , 194 ].…”