Rapid identification ofStreptococcus pyogenes by flow cytometry

Flow cytometry combined with immunofluorescence ofStreptococcus pyogenes was used to assay bacteria suspended in buffer solution and in saliva derived from throat swabs of healthy volunteers. The method allowed the enumeration of as few as 5 × 10³ and 5 × 10⁴ CFU per milliliter of buffer and saliva respectively. Controls includingStreptococcus salivarius instead ofStreptococcus pyogenes or buffer instead of specific antibodies confirmed the specificity of the detection ofStreptococcus pyogenes in the samples. The results suggest that flow cytometry may serve as a basis for an automated reliable method for the diagnosis of streptococcal infections.