The Effect of Inorganic Salts on the Production of Small Colony Variants by Staphylococcus Aureus

Abstract

17 strains of Staph. aureus were grown in various concs. of BaCl2 made up in 4 types of media: 1) meat-infusion broth, 2) 1% peptone, 3) 1% peptone activator medium, 4) 1% peptone to which was added nicotinic acid and vitamin B1. All strains produced numerous stable and unstable small colony variants within 2 to 6 days when grown in the BaCl2 activator medium. The number and stability of these variants were, in most cases, directly proportional to the conc. of BaCl2 in which growth occurred. The other basic media gave less consistent results. Staphylococci were also grown in peptone activator medium to which was added Ba(NO3)2, Ba(NO2)2, MgCl2, CaCl2, LiCl and NaCl. Ba(NO2)2 gave results similar to BaCl2. Ba(NO3)2 stimulated growth, probably due to the energy obtained from the reduction of the nitrate to nitrite, and no small colony variants were obtained. Similarly, no small colony variants were obtained with any of the other salts except LiCl which produced them on one occasion from only one strain. Laboratory strains of Sarcina lutea, Escherichia coli, Shigella dysenteriae, Shigella paradysenteriae Flexner, Eberthella typhosa, Salmonella schottmuelleri, Pseudomonas aeruginosa and Bacillus subtilis were also tested for the production of small colony variants when grown in BaCl2 activator medium. Sarcina lutea was the only organism from which small colony variants were obtained.