Development of a Selective Enterococcus Medium Based on Manganese Ion Deficiency, Sodium Azide, and Alkaline pH

C. J. Efthymiou, S. W. Joseph
1974 Applied microbiology  
Rogosa broth, without its salt supplement and dissolved in deionized water, was adapted for the selective isolation and enumeration of enterococci. This medium supported good growth of enterococci, but it suppressed growth of other lactic acid bacteria. The sensitivity and specificity of the medium were tested after addition of various increasing concentrations of NaN3 against known strains of enterococci and other bacteria. Many strains of Streptococcus faecium showed low azide tolerance;
more » ... ide tolerance; optimal growth was obtained at a concentration of 0.01% NaNs, which totally, or partially inhibited unrelated species of lactic acid bacteria. The selectivity of the medium was further increased by pH adjustment to 9.6. Carbonate and Tween 80 were added to overcome partial inhibition of enterococcal growth by the new combination of selective conditions. The final medium was evaluated in agar form in isolations from human and animal feces, polluted water, meat, and dairy products. Counts were obtained after 16 to 17 h of incubation at 37 C. The isolates satisfactorily conformed to the group characteristics of enterococci. 0.01% NaNs. Various initial pH values were also 411 on March 23, 2020 by guest Downloaded from
doi:10.1128/aem.28.3.411-416.1974 fatcat:j4jedurzlfa6hfn5o2a4q5rwqe