Faecal Streptococcus recovery and efficiency of selective media via surface plating technique.

The recovery rate of faecal streptococci from various vehicles was studied via different selective media and surface plating technique. With the exception of thallous acetate medium, the adopted media and method were only successful for examining the highly polluted materials. Medium bearing thallous acetate at concentrations up to 1 : 500 was selected as the better means for obtaining high yield and fair selectivity. Otherwise, the tellurite medium (1 : 4,000) was found to give low yield and fair selectivity, while medium bearing sodium azide (1 : 2,000) appeared to give low yield and high selectivity. Media bearing twin combinations second low yield and high selectivity, other than media bearing one concentrating agent. However, thallous-azide combination secured better conditions for faecal streptococci recovery than the tellurite-azide combination. Addition of selective agents to the examined liquid samples for 1 hr, singly or in combination before faecal streptococci recovery, exerted no marked effect on the cut down of contaminants.