Evaluation of the El Kholy technique for grouping beta-hemolytic streptococci.

One hundred and eleven strains of beta-hemolytic streptococci of human origin were grouped by the new nitrous acid procedure described by El Kholy et al. The results were comparable to the grouping obtained by the classical Lancefield hot-hydrochloric acid method. The El Kholy technique is simple and economic and is shown to be as sensitive and specific as the Lancefield procedure. We recommend the new method for routine use in the clinical laboratory and in studies on the prevalence of Streptococcus pyogenes in a developing country such as Brazil.