Severe Streptococcus pyogenes infections in Norway - Molecular genetic analysis of antibiotic resistance and virulence determinants

Group A streptococci is one of the most common human pathogens that can produce a variety of diseases ranging from mild pharyngitis (strep throat) to life-threatening toxic shock syndrome and necrotizing fasciitis. The incidence of invasive streptococcal disease has been increasing in Norway in the past two decades, with marked epidemic peaks in 1988 and 1998. Especially high rates of necrotizing fasciitis have been observed. The reasons for this re-emergence of GAS are not fully understood, but acquisiti on of new virulence determinants encoded by phages and phage-like elements may be the cause of the occurrence of these epidemics. We are presently looking at the association of clinical forms of the disease, principally necrotizing fascitiis, with specif ic bacterial clones. During a 6-month stay in Dr. Musser's laboratory, Houston, Texas, the distribution of bacterial superantigens and other known virulence factors in isolates recovered from cases of necrotizing fasciitis will be compared to that in isol ates of the same M-types/sequence types obtained from pharyngitis cases. Comparative microarray analysis of M1 and M3 strains collected in Norway will be performed in the course of the USA visit in an attempt to identify novel virulence factors and gain n ew insight into understanding of GAS pathogenesis.