Streptococcus pyogenes Isolates Causing Severe Infections in Norway in 2006 to 2007: emm Types, Multilocus Sequence Types, and Superantigen Profiles

Abstract

To investigate the epidemiological patterns and genetic characteristics of disease caused by group A Streptococcus (GAS), all available isolates from invasive cases in Norway during 2006 to 2007 (262 isolates) were subjected to antimicrobial susceptibility testing, T serotyping, emm typing, and multilocus sequence typing and screened for known streptococcal pyrogenic exotoxin (Spe) genes, smeZ, and ssa. The average incidence rate was 3.1 cases per 100,000 individuals. The most prevalent sequence types (STs) were STs 52, 28, and 334. In association with emm types 28, 77, and 87, the serotype T-28 comprised 24.8% of the strains. emm types 28, 1, and 82 were dominating. In 2007, a sharp increase in the number of emm-6 strains was noted. All strains were sensitive to penicillin and quinupristin-dalfopristin, while 3.4% and 6.1% of the strains were resistant to macrolides and tetracycline, respectively. Furthermore, the emm-6 strains had intermediate susceptibility to ofloxacin. Isolates displayed a wide variety of gene profiles, as shown by the presence or absence of the Spe genes, smeZ, and ssa, but 48% of the isolates fell into one of three profiles. In most cases, an emm type was restricted to one gene profile. Although the incidence decreased during this study, invasive GAS disease still has a high endemic rate, with involvement of both established and emerging emm types displaying variability in virulence gene profiles as well as differences in gender and age group preferences.

The M protein of group A Streptococcus is a key virulence factor and a clinically relevant strain identification marker

“…36 Almost all M6 isolates studied in these reports were resistant to ofloxacin, while all other M types were susceptible. Another example of tight correlation between rare antibiotic resistance phenotypes and specific M types comes from a study in France which showed a unique resistance to bacitracin (paired with wide resistance to other diverse antibiotics) among M28 isolates.…”

“…Moreover, the types that are most dominant in invasive categories, and hence those responsible for the observed decrease in diversity, are almost always the same-most notably M1 and M3. 8,12,18,[32][33][34][35][36] Similar dynamics, including decreased diversity and the dominance of specific types, are apparent in studies of more specific clinical phenomena such as fatality, associated with M1, M3 and M12, 32 puerperal sepsis, associated with M28, 34,36,37 STSS, associated with M1 and M3, 12,35,38 epidemic ARF, associated with M5 and M18, 39 and geographically widespread epidemic behavior, most commonly associated with M1. 2,12 Despite genetic changes in these serotypes over time, including alterations of virulence and antibiotic resistance factors, these associations generally remain stable.…”

“…34 M28 has also been associated with puerperal sepsis in Norway. 36 A study in France found M28 in similar association with puerperal sepsis as well as other types of invasive infection, including necrotizing fasciitis, genital peritonitis, bacteremia, endocarditis and meningitis. 37 This strain was resistant to many antibiotics, including bacitracin.…”

“…46,47 Studies suggest the M type distributions of many resistance traits are not well conserved over time and space. 22,34,36,[46][47][48] However, a recent US study showed that even these highly variable traits segregate significantly with M type over shorter periods of time. 44 Macrolide resistance offers an excellent example of a phenotype that is more highly correlated with M type and for which M typing offers a significant degree of predictive power.…”

Evaluation of sclB gene variation in Streptococcus pyogenes (Lancefield group A Streptococcus) and potential for subtyping

“…The M protein is encoded by the emm gene, and sequence analysis of the 59 hypervariable portion of this gene has largely replaced the serological typing method (Beall et al, 1996). The emm type distribution varies worldwide but emm types 1, 3, 28 and 89 are the most commonly found types in reports of GAS-related disease (Imöhl et al, 2010;Meisal et al, 2010a;Siljander et al, 2010).…”