Comparative epidemiology of Streptococcus pyogenes emm-types causing invasive and noninvasive infections in French children by use of high-resolution melting-polymerase chain reaction.

BACKGROUND

This study aims to analyze the epidemiology of Group A streptococci (GAS) emm-types causing invasive and noninvasive infections in French children.

METHODS

From September 2009 to May 2011, we analyzed GAS isolates from 585 pharyngitis, 125 invasive infections and, for the first time in France, 32 healthy carriers. M protein gene (emm) typing of the isolates was carried out by a new rapid technique, combining 3 multiplex-polymerase chain reactions (PCRs) coupled to high-resolution melting (HRM) curves, able to detect 13 major emm-types (emm 1, 3, 4, 6, 11, 12, 22, 28, 75, 77, 87, 89 and 102).

RESULTS

GAS belonging to emm-type 1 were more frequently found among invasive infections than among pharyngitis (24.0% vs. 11.5%, P < 0.001); emm 4 and 89 were more common in pharyngitis than in invasive infections (emm-type 4, 17.4% vs. 6.4%, P = 0.002 and emm-type 89, 9.9% vs. 2.4%, P = 0.006, respectively) and emm 3 and 4 were more common in cases of pharyngitis associated with scarlet fever (21.6% vs. 6.0%, P < 0.001 and 29.3% vs. 14.5%, P < 0.001, respectively).

CONCLUSION

HRM method enables the rapid emm-typing of a large number of isolates in epidemiological studies. Comparison of GAS causing invasive and noninvasive infections in the same population of children displays an unbalanced repartition of emm-types.