Potentially virulent strains and high colony counts of group A beta-haemolytic streptococci in pharyngitis patients having a delayed recovery or a complication

T serotyping and M and exotoxin genotyping were performed on strains from 3 67 streptococcal pharyngitis patients in Dutch general practice. Potentiall y virulent strains of group A beta -haemolytic streptococci, such as T1M1 a nd T3M3 subtypes and strains expressing speA and speC, and a high number of colony counts did not occur more frequently in the 166 (45%) more seriousl y ill patients, defined as those who showed a delayed recovery or a complic ation.