Some physiological charcteristics of two sets of phage-propagating strains of Staphylococcus aureus.

A number of physiological characteristics were studied on some 29 strains of phage-propagating staphylococci belonging to the Basic International Series and the Seto-Wilson bovine-adapted set. All the cultures except strain 73 were coagulase-positive, with reciprocal titers ranging from 2 to 8,192. Strain 73 was again an exception with respect to phosphatase activity. Group 1 yielded high values for both phosphatase and oxygen uptake but low values for extracellular protein. Resistance to penicillin was demonstrated only by strains 80, 81, 53, 54, 75, and 77. Strain 70, one of the highest coagulase producers, alone showed no catalase activity. Mannitol was fermented by all coagulase-positive strains. Hemolysis of one or more of three kinds of erythrocytes (sheep, rabbit, and human) was a common characteristic of most strains. However, pigmentation was a nondiscriminating parameter. Although one-half of the cultures liquefied gelatin, most of them gave similar antibiotic-sensitivity tests, except the six which were penicillinase producers. There was little difference in growth rate for all strains. Comparison of coagulase production to cell size indicated that the high-titer strains were generally larger than the low producers. The foregoing evidence avers that, in addition to lytic spectrum, physiological properties can usefully characterize staphylococcal phage-propagating strains.