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Many investigators find no spread of Legionnaires disease from person to person. The present study examined the question of airborne transmission of infection by Legionella pneumophila serogroup 1 from guinea pigs inoculated nasally with the agent to healthy guinea pigs. The nasal inoculation produced confluent peribronchiolar pneumonia similar to the pulmonary lesions observed in humans, but by techniques of clinical observation, serology, culture, and pathology, there was no evidence of airborne spread of infection from 26 inoculated guinea pigs to 64 uninoculated guinea pigs. The results, compatible with epidemiological studies of Legionnaires disease that fail to demonstrate airborne person-to-person transmission of the illness in humans, are useful for scientists who work with animal models of Legionnaires disease.

Hammel, Jay M. (The Pennsylvania State University, University Park) and L. N. Zimmerman. Growth stimulation of Streptococcus faecalis var. liquefaciens by canavanine. J. Bacteriol. 86:490-493. 1963.-l-Canavanine, a competitive inhibitor of arginine, was found to stimulate the growth of Streptococcus faecalis var. liquefaciens in the presence of arginine. This growth stimulation by canavanine was unique, since it previously was found to inhibit the growth of organisms which require arginine. When equimolar concentrations of arginine and canavanine were tested from 10(-7) to 10(-2)m, maximal stimulation occurred at 10(-4)m. Canavanine concentrations of 5 x 10(-6)m to 10(-2)m stimulated growth in the presence of 5 x 10(-5)m arginine. Ornithine similarly stimulated growth. Canavanine inhibited the rate of arginine degradation by the arginine dihydrolase enzyme system in intact cells. It is assumed that the mechanism of canavanine stimulation involves an inhibition of arginine desimidase of the arginine dihydrolase enzyme system, which in turn makes more arginine available for growth over a longer period of time.

A lytic enzyme active against viable, intact staphylococci is released into culture fluids upon lysis of bacteriophage-infected Staphylococcus aureus PS53 cells. This enzyme, staphylococcal phage-associated lysin (PAL), was partially purified by ammonium sulfate precipitation and gel filtration through Sephadex G-200. PAL is optimally active at pH 6.5 and 30 C, and lytic activity is greatly enhanced by the addition of reducing agents. Lytic activity was observed against all strains of staphylococci tested and against purified staphylococcal cell walls, but no activity was noted against other bacterial species. PAL possesses peptidase activity and results in the production of spheroplasts which can be osmotically stabilized for extended periods by the addition of 7.5% polyethylene glycol 4000.

l-Canavanine, an analogue of arginine, was found to stimulate the synthesis of an extracellular proteinase in Streptococcus faecalis var. liquefaciens. Cells grown in a synthetic medium containing 10(-4)m arginine and 10(-4)m canavanine produced almost twice as much proteinase as cells grown in 2 x 10(-3)m arginine alone; total growth was the same in both media. Hydrolyzed proteinase samples were analyzed for arginine and canavanine by means of paper chromatography and electrophoresis. Arginine, but not canavanine, was detected in the purified enzyme sample.