Epidemiological and molecular analysis of Streptococcus pyogenes isolates causing invasive disease in Spain (1998-2009): comparison with non-invasive isolates

Abstract

The incidence, clinical manifestations, and circulating clones involved in Streptococcus pyogenes invasive disease was analyzed in two regions of Spain between 1998 and 2009. The annual average incidence of invasive disease was 2 episodes per 100,000 inhabitants (3.1 for children and 1.9 for adults). The most frequent clinical manifestations were cellulitis (41.3%), bacteremia without focus (19.0%), streptococcal toxic shock syndrome (12.6%), and pneumonia (7.7%). Among 247 invasive isolates analyzed, the most prevalent clones were emm1/ST28 (27.9%), emm3/ST15-406 (9.8%), and emm4/ST39 (6.5%). The emm1/ST28 clone was the only clone detected each year throughout the study period and was associated with more than one third of all fatal outcomes. When invasive isolates were compared with 1,189 non-invasive isolates, the emm1/ST28 clone was significantly associated with invasive disease. The speA and ssa genes were more frequent among invasive emm1 and emm4 isolates, respectively. Forty-two (17%) invasive isolates were resistant to erythromycin (21 harbored the mef gene and 21 the ermB or ermA genes). Twenty-two (8.9%) isolates had reduced susceptibility to ciprofloxacin (minimum inhibitory concentration [MIC] 2-8 μg/mL) and 32 (13%) were tetracycline-resistant (tetM or tetO gene). In conclusion, the emm1 type was overrepresented among invasive cases and was associated with high mortality rates.