Propagation of Staphylococcal Typing Phages on a Common Host , StuphyZococcus uureus

A broad range of typing phages belonging to lytic groups I, 11, 111, IV and those classified as miscellaneous produced plaques on Staphylococcus aureus strain KI. Two variant forms of this strain were compared, KIN and KIHI. Phages belonging to lytic group 11, of both A and B serology, had low efficiencies of plating (EOP) for the KiN variant but had high EOP values for the KIHI variant. In general, of phages from other lytic groups, those of B serology tended to plate with low EOP values on both variants, whereas those of A serology plated with high EOP values. Propagation of several of the phages on both KI hosts resulted in host-modifications of the phage progeny. Similar host-induced modifications were produced by propagation of the phages on ps 73. The host-modified phages showed striking losses in plating efficiency for their usual propagating hosts. The significance of these findings with respect to genetic classification of the phages and hosts is discussed.