Comparison of invasive (septicemic) and non invasive strains of group A streptococci isolated during a one-year national survey in France. The Groupe d'Enquête 1995 sur les Infections Streptococciques

Epidemiology of invasive Streptococcus pyogenes infections in France in 2007

Invasive group A streptococcal (GAS) infections cause significant morbidity and mortality. A national survey was initiated to assess the burden of invasive GAS infections in France, describe their clinical characteristics, and assess the molecular characteristics of GAS strains responsible for these infections. The survey was conducted in 194 hospitals, accounting for 51% of acute care hospital admissions in France. Clinical data, predisposing factors, and demographic data were obtained, and all GAS isolates were emm sequence typed. We identified 664 cases of invasive GAS infections, with an annual incidence of 3.1 per 100,000 population. The case-fatality ratio was 14% and rose to 43% in the case of streptococcal toxic shock syndrome. Bacteremia without identified focus (22%) and skin/soft tissue infections (30%) were the most frequent clinical presentations. Necrotizing fasciitis was frequent in adults (18%) and uncommon in children (3%). The 3 predominant emm types were emm1, emm89, and emm28, accounting for 33%, 16%, and 10% of GAS isolates, respectively. The emm1 type was associated with fatal outcomes and was more frequent in children than in adults. Six clusters of cases were identified, with each cluster involving 2 invasive cases due to GAS strains which shared identical GAS emm sequence types. Four clusters of cases involved eight postpartum infections, one family cluster involved a mother and child, and one cluster involved two patients in a nursing home. Invasive GAS infection is one of the most severe bacterial diseases in France, particularly in persons aged ≥ 50 years or when associated with toxic shock syndrome.

Molecular characterization of Streptococcus pyogenes isolates to investigate an outbreak of puerperal sepsis

OBJECTIVE

To describe microbiological characteristics and epidemiologic features of an outbreak of postpartum endometritis.

METHODS

Various markers were investigated in five patients and three throat carriage isolates of Streptococcus pyogenes obtained during an outbreak of endometritis occurring in a 13-week period. Molecular characterization included biotyping, T-serotyping, emm gene sequence and restriction, pulsed-field gel electrophoresis (PFGE), and random amplified polymorphic DNA (RAPD) analysis.

RESULTS

Biotype, T-serotype, and genotypic data (emm analysis, PFGE, and RAPD analysis) revealed a close relationship among the isolates from three patients, suggesting that cross-contamination had occurred. These isolates were biotype 1, T type 28, and emm type 28. The isolates from one patient and one carrier differed from those of the index patient by minor variations of the emm amplicon restriction pattern, PFGE pattern, or RAPD pattern. The remaining isolates were phenotypically and genetically different.

CONCLUSION

Identification of different isolates demonstrated that different strains may circulate simultaneously during a true outbreak and that the predominant strain might persist for several months.

In vitro activity of midecamycin diacetate, a 16-membered macrolide, against Streptococcus pyogenes isolated in France, 1995-1999

OBJECTIVE

To compare the in vitro activity of midecamycin diacetate to that of five other macrolides (erythromycin, clarithromycin, roxithromycin, azithromycin, and josamycin) and of clindamycin against 146 clinical isolates of Streptococcus pyogenes, with regard to three different phenotypes of erythromycin resistance.

METHODS

Susceptibility pattern and resistance phenotype were determined by disk diffusion method and double disk test. Minimal inhibitory concentrations of antibiotics were obtained by the agar dilution method and evaluated according to the recommendations of the 'Comité de l'Antibiogramme de la Société Française de Microbiologie' (CA-SFM). The major determinants of erythromycin resistance in S. pyogenes (ermB, ermTR and mefA genes) were investigated by specific amplification protocols.

RESULTS

Most of the isolates of S. pyogenes collected during 1995-99 were susceptible to midecamycin (93.8%), erythromycin (90.4%), clarithromycin (93.2%), roxithromycin (91.8%), azithromycin (88.4%), josamycin (94.5%), and clindamycin (94.5%). According to the CA-SFM criteria, 132 of the 146 isolates studied were susceptible to erythromycin (MICs < or = 1 mg/L), four were intermediate (MICs 2-4 mg/L), and 10 were resistant (MICs > 4 mg/L). Only nine isolates were midecamycin resistant (MICs > 4 mg/L), and the others were susceptible. The increased activity of midecamycin (MIC90 < or = 0.06 mg/L), as compared to erythromycin (MIC90 = 0.5 mg/L) and to other 14- or 15-membered macrolides, was related to the absence of the ermB determinant in seven isolates which displayed an efflux phenotype (five isolates) or an inducible resistance phenotype due to an ermTR determinant (two isolates).

CONCLUSION

Midecamycin diacetate is active against most S. pyogenes strains isolated in France and may represent an attractive alternative to the treatment of streptococcal infections due to resistant isolates with efflux of erythromycin.