Molecular analysis of pyrogenic exotoxins from Streptococcus pyogenes isolates associated with toxic shock-like syndrome

Abstract

Toxic shock-like syndrome (TSLS) is characterized by hypotension or shock, fever, multiorgan system involvement, and a concurrent group A streptococcal infection. We analyzed 34 streptococcal strains isolated from patients with clinically well-documented TSLS for their pyrogenic toxin profiles and M-protein types. Although strains of nine different M types were represented in the sample, 74% of the isolates were of either M type 1 or 3. It was determined that 53% produced streptococcal pyrogenic exotoxin type A under in vitro growth conditions and that 85% contained the gene encoding this toxin. These values are in contrast to the published value of 15% for the incidence of this gene in a sample of general group A streptococcal isolates. As has been found with all group A streptococci examined to date, regardless of disease association, 100% of TSLS-associated isolates contained the gene encoding pyrogenic exotoxin type B. This toxin was detectably produced by 59% of isolates. The gene encoding pyrogenic toxin type C was found in only 21% of isolates. We conclude that the pyrogenic exotoxin type A gene is associated with group A streptococcal strains isolated from patients with TSLS and may play a causative role in this illness. However, other factors are also likely to be important, since not all strains from patients with TSLS contained the A toxin gene.

Strain variations among Streptococcus pyogenes T1—a possible explanation for bacteremia epidemics?

“…The presence of the speA gene was studied because of its in vitro stability [23] and variable occurrence in strains causing invasive disease [12,13,24,25]. All 24 isolates studied were found to contain the gene.…”

Epidemiological markers of Streptococcus pyogenes strains in Tunisia

“…Sequence analysis of emm has become an important surveillance tool for investigating the dynamics of GAS infections, and approximately 170 emm types and 750 emm subtypes have been documented [5]. Furthermore, GAS produces a range of streptococcal pyrogenic exotoxins, which are important in the pathogenesis of severe GAS infections, where they act as superantigenic toxins (SAgs) [6]. The gene distribution of SAgs has been used as an additional epidemiological tool for the exploration of genomic heterogeneity and possible correlations between toxin gene content and disease type [3].…”

Association of pyrogenic exotoxin genes with pharyngitis and rheumatic fever/rheumatic heart disease among Indian isolates of Streptococcus pyogenes

“…Studies on distribution of spe genes show that most GAS strains encode speB and speF while speA and speC occur less frequently (Iwasaki et al 1993;Norrby-Teglund et al 1994). Most of the strains associated with severe streptococcal infections have been shown to produce the speA toxin (Yu and Ferretti 1989;Hauser et al 1991;Tyler et al 1992;Inagaki et al 1997). However, other reports show that the less potent speB and speC toxins, individually or together, may also be present in such strains, posing a question regarding the role of speA as a major virulence factor (Belani et al 1991).…”