Additional differentiation of methicillin resistant strains of Staphylococcus aureus typed by the international phage bank

: In the methicillin resistant strains of Staphylococcus aureus (MRSA) typed by the International Set phages the host specificity of the restriction-modification of the phage 85 DNA was determined, the finger printing of the cell DNA was carried out with using two probes and the lytic spectrum of the phages induced in them was studied. Four clones with different specificity of the restriction-modification system (rm89, rm108, rm121 and rm947) differing from that of strain PS 85 which is the host of phage 85 were detected. The strains belonging to the modification types m89, m108 and m121 contained prophages (within the respective groups) with similar lytic spectra when tested with the use of the PS strains of the International Collection and had cross antiphage immunity. Six phage variants were detected among the phages induced in the strains with the modification type m947 which could be indicative of the clone heterogeneity.