Abstract
In 1915, two years before the discovery of d'Hérelle, Twort described the following phenomenon. 2 If glycerinated calf vaccinia is streaked on agar slants, a certain number of the micrococcus colonies which grow become glassy and transparent, and degenerate into a granular material which cannot be subcultured and which, even when diluted 1,000,000 times and filtered, gives rise to the same degeneration when added to a normal culture of micrococci, and so on indefinitely.
Because of the similarity between these observations and the phenomenon of d'Hérelle, the following experiments were undertaken with the hope of obtaining from vaccinia a typical bacteriophage for staphylococci.
Several agar slants were seeded with untreated fresh green vaccinia pulp. The growth, consisting of Staphylococcus albus, Staphylococcus aureus, and B. coli, looked normal in all tubes but one, in which a few small, clarified areas were found.
Filtrates obtained from subcultures of these clarified spots were found to possess a marked inhibiting and dissolving action on the growth of staphylococci, and this lysis could be carried on indefinitely from one culture to another.
Staphylococcus is, therefore, the first Gram-positive bacterium for which an observation of transmissible autolysis has been made. Attempt to extend the lysis to other cocci has thus far been unsuccessful.
As has already been observed for other species, great variations in sensitiveness exist not only among different strains of staphylococci—certain ones remaining unaffected—but also between different organisms of a single strain, a few individuals usually being able to resist solution.
If a partially dissolved culture of staphylococcus is streaked on agar plates, it is found that in the first streak, where the lytic broth is spread abundantly together with the cocci which are still alive, the growth is poor, irregular and glassy.
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