Clinical and epidemiological aspects of invasive Streptococcus pyogenes infections in Denmark during 2003 and 2004

Active surveillance of invasive group A streptococcal (GAS) infections was conducted in Denmark during
2003 and 2004 as a part of the Strep-EURO initiative. The main objective was to improve understanding of the
epidemiology of invasive GAS disease in Denmark. During the 2 years, 278 cases were reported, corresponding
to a mean annual incidence of 2.6 cases per 100,000 inhabitants. The vast majority of isolates, 253 (91%), were
from blood, with the remaining 25 (9%) being from cerebrospinal fluid, joints, or other normally sterile sites.
The mean case fatality rate (CFR) was 20%, with the rate being higher in patients more than 70 years of age
(36.5%). For streptococcal toxic shock syndrome (STSS) and necrotizing fasciitis the CFRs were 53% and 25%,
respectively. Out of 16 T types recorded, three predominated: T28 (23%), T1 (22%), and the cluster T3/13/B3264
(14%). Among 29 different emm types, emm28 and emm1 accounted for 51% of strains, followed by emm3 (11%),
emm89 (7%), and emm12 (5.5%). Low resistance rates were detected for macrolide-lincosamide-streptogramin
B (MLSB) antibiotics (3%) and tetracycline (8%); two isolates exhibited coresistance to tetracycline and
macrolides. Of nine pyrogenic exotoxin (superantigen) genes examined, speA and speC were identified in 58%
and 40% of the strains, respectively; either of the genes was present in all strains causing STSS. Most strains
harbored speG (99%). ssa was present in 14% of the isolates only. In Denmark, as in comparable countries, GAS
invasive disease shows a sustained, high endemicity, with involvement of both established and emerging
streptococcal emm and T types.