Streptococcus pyogenes emm Types and Clusters during a 7-Year Period (2007 to 2013) in Pharyngeal and Nonpharyngeal Pediatric Isolates

Abstract

Group A streptococcus (GAS) is an important cause of morbidity and mortality worldwide. Surveillance ofemmtypes has important implications, as it can provide baseline information for possible implementation of vaccination. A total of 1,349 GAS pediatric isolates were collected during a 7-year period (2007 to 2013);emmtyping was completed for 1,282 pharyngeal (84%) or nonpharyngeal (16%) isolates, andemmclusters and temporal changes were analyzed. Thirty-five differentemmtypes, including 14 subtypes, were identified. The most prevalentemmtypes identified were 1 (16.7%), 12 (13.6%), 77 (10.9%), 4 (10.8%), 28 (10.4%), 6 (6.8%), 3 (6.6%), and 89 (6.6%), accounting for 82.3% of total isolates. Rheumatogenicemmtypes comprised 16.3% of total isolates. Theemmtypes 12, 4, and 77 were more prevalent among pharyngeal isolates, and theemmtypes 1, 89, 6, 75, and 11 were more prevalent among nonpharyngeal isolates. Theemmtypes identified belonged to 13emmclusters, and the 8 most prevalent clusters comprised 97% of all isolates. There were statistically significant decreases in the prevalence ofemmtypes 12, 4, 5, and 61 and increases in the prevalence ofemmtypes 89, 75, and 11, compared with the period 2001 to 2006. The proposed 30-valent GAS vaccine, which is currently in preclinical studies, encompasses 97.2% of theemmtypes detected in our study and 97.4% of the erythromycin-resistant strains. In addition, it includes 93.3% of theemmtypes involved in bacteremia. A much greater diversity of GASemmtypes was identified in our area than described previously. Seasonal fluctuations and the introduction of newemmtypes were observed. Continuous surveillance ofemmtypes is needed in order to evaluate the possible benefits of an M protein-based GAS vaccine.