COMPARISON OF 5 METHODS FOR THE DETERMINATION OF ARGININE HYDROLYSIS BY VIRIDANS STREPTOCOCCI

Seventy-eight clinical isolates and four control strains of viridans s treptococci were tested in parallel for arginine hydrolysis by five di fferent methods, These comprised two commercial systems, the API20 STR EP and Vitek GPI card, two published methods, one based on ammonia pro duction and one on alkalisation of Moeller's decarboxylase medium, and a method based on alkalisation of a phenol-red broth medium dispensed into microtitration plates, The clinical isolates were speciated by t heir biochemical reactions in the API20 STREP and API20 ZYM systems, O ne strain produced only a weak reaction for arginine hydrolysis in the medium by ammonia production, but otherwise the results with this med ium, the API20 STREP and the microtitration plate method were identica l, Tests with the Moeller decarboxylase medium and Vitek GPI card gave negative results with isolates that were positive by other methods, I noculum size was shown to influence arginine hydrolysis obtained with Streptococcus sanguis NCTC 7863 and S. milleri 10713.