COMPARATIVE STUDIES ON THE COLONIAL VARIANTS OF THE SMITH STRAIN OF STAPHYLOCOCCUS AUREUS

Abstract

The Smith strain of staphylococcus, used in many laboratories for "virulence" studies, is known to be genetically unstable. The strain has been shown to have more than one colony type, and reports concerning its phage type and its phage typability have been conflicting. In our work, four "Smith" strains were obtained from four different laboratories. Three of these strains produced three colony variants—compact, diffuse, and mucoid—whereas the fourth strain produced only the compact and mucoid variants. Results with phage typing were not always consistent but the compact colony variants were much more susceptible to lysis by phage than the parent strains, and the diffuse variants appeared to be completely resistant to lysis by phage. The results confirm reports in the literature that the Smith strain is genetically unstable and gives rise to a number of different colony forms with varying phage susceptibility.