Prevalence of M-types and streptococcal pyrogenic exotoxin A and C genes in group A strepotococcal isolates from uncomplicated pharyngitis in Mexico City

Group A Streptococcus (GAS) is a significant cause of human morbidity worldwide associated with a variety of mild and severe diseases. Some M serotypes of GAS have been associated with invasive infections, making it important to maintain epidemiological surveillance of GAS strains in the general population. 215 GAS strains were isolated from uncomplicated pharyngitis from different hospitals in Mexico City. GAS isolates were tested by PCR for emm (M protein), sof (serum opacity factor), sic (streptococcal inhibitor of complement-mediated lysis), speA (exotoxin pyrogenic A) and speC (C) genes. The sof genotype and the RFLP profiles from emm amplicons with DdeI enzyme were used to group the isolates. The emm types were determined by analysis of the emm gene sequence. The emm12, emm1 and emm75 types represented close to 55% of the isolates. While the speC gene was detected in 76% of the isolates, the speA gene was positive in 23%. All speA and sic positive isolates were emm1 type. Hence, emm1 and emm12 types still have a high prevalence in uncomplicated streptococcal infection in our community. Molecular characterization of GAS strains can therefore be of value in epidemiological surveillance of GAS infections.