Highly virulent M1 Streptococcus pyogenes isolates resistant to clindamycin.

CONTEXT: Emm1-type group A Streptococcus (GAS), or Streptococcus pyogenes, is mostly responsible for invasive infections such as necrotizing fasciitis (NF) and streptococcal toxic shock syndrome (STSS). The recommended treatment of severe invasive GAS infections is a combination of clindamycin and penicillin. Until 2012, almost all emm1 isolates were susceptible to clindamycin. OBJECTIVES: We aimed to identify the phenotypic and genotypic characteristics of emm1 GAS clone resistant to clindamycin. METHODS: GAS strains were characterized by emm sequence typing, detection of genes encoding pyrogenic exotoxins or superantigens. Cluster analysis was performed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Antibiotic susceptibility was assessed using disk diffusion and resistance genes were detected by PCR. RESULTS: A total of 1321 GAS invasive isolates were analyzed between January 2011 and December 2012. The overall number of invasive isolates resistant to clindamycin was 52 (3.9%); seven of them were emm1 isolates. All isolates had the same genomic markers: macrolide resistance due to the presence of the erm(B) gene, emm subtype 1.0, the same toxin or superantigen profile, PFGE pattern and sequence type. CONCLUSION: This is the first description of highly virulent GAS emm1 isolates resistant to clindamycin in France. This article strengthens the need for monitoring the epidemiology of invasive GAS strains as they could lead to changes in treatment guidelines.

[Epidemiology of Streptococcus pyogenes invasive diseases in France (2007-2011)]. / Épidémiologie des infections invasives à Streptococcus pyogenes (France 2007-2011).

Group A Streptococcus (GAS) is a human pathogen responsible for a wide range of clinical manifestations. An increase of GAS invasive infections has been described since the mid 1980s. To study the French epidemiology of invasive infections (i) we characterized all GAS invasive strains received at the French National Reference Center for streptococci (CNR-Strep) between 2007 and 2011; (ii) we analyzed the epidemiological data on the corresponding strains. For each strain, emm genotype, superantigen genes and antibiotics susceptibility were determined. Among the 2 603 non redundant invasive GAS strains, 65.1 % (n=1 695) were isolated from blood culture. A streptococcal toxic shock syndrome (STSS) was described in 16.4 % (n=428) of cases, mostly associated with necrotizing fasciitis (NF), pleuropulmonary or osteoarticular infections (p ≤0.001). The case fatality rate was 10.6 %. A total of 102 different emm genotypes were identified. Three emm genotypes predominated, reaching nearly 60 % of the strains: emm 1 (26.7 %), emm 28 (16.4 %), and emm 89 (12.8 %). The proportion of each emm genotype varied according to the year and the age of patients. Among those < 15 years old, the three main genotypes were emm 1 (36.8 %), emm 12 (12.9 %) and emm 4 (9.5 %). The distribution of superantigen genes (SpeA, SpeC and Ssa) was restricted to several emm genotypes. Between 2007 and 2011, the rate of macrolides resistant GAS strains decreased from 7.8 to 5.5 %. emm 1 strains are still the most common especially in most severe clinical manifestations including STSS and NF.

Invasive group A streptococcal infections in adults, France (2006-2010).

Severe invasive group A streptococcal diseases have re-emerged during the past 10-20 years. In order to provide a better insight into the current epidemiological situation in France, we analysed the questionnaires regarding all invasive strains received at the National Reference Center for Streptococci (CNR-Strep) between 2006 and 2010 from patients aged ≥ 18 and characterized them by emm typing, spe gene detection and antibiotic resistance. Among the 1542 invasive GAS strains studied, 78% (n=1206) were from blood cultures, and a streptococcal toxic shock syndrome (STSS) was described in 22% (n=340) of cases, mainly associated with necrotizing fasciitis (NF) and pleuro-pulmonary infections (p<0.001). The in-hospital fatality rate was 15%. A total of 83 different emm types were recovered but the three predominant emm types, representing almost 60% of the isolates, were emm1 (24%), emm28 (17%) and emm89 (15%). The preponderance of each emm type varied according to the year, with a significant constant increase of emm28 strains, whereas emm1 strains, representing approximately 32% of GAS invasive isolates in 2007 and 2008, dropped to <15% in 2010 (p<0.001). The distribution of phage-associated superantigen genes (speA, speC and ssa) was linked to certain emm types. Between 2006 and 2010, the percentage that was macrolide-resistant decreased from 11% to 5%, confirming the trend observed in 2007. Fortunately, emm1 strains associated with the most life-threatening clinical manifestations remain susceptible to all anti-streptococcal antibiotics.

Chemometric labeling of cereal tissues in multichannel fluorescence microscopy images using discriminant analysis.

This paper presents a novel, semiautomatic method for microscopic identification of multicomponent samples, which allows the identification, location, and percentage quantity of each component to be determined. The method involves applying discriminant analysis to a sequence of multichannel fluorescence microscopy images via a supervised learning approach; by selecting groups of pixels that are representative for each component type in a "known" sample, a computer is "taught" how to recognize the behavior (i.e., fluorescence emission) of the various components when illuminated under different spectral conditions. The identity, quantity, and location of these components in "unknown" samples (i.e., samples with the same component types but in different ratios or distributions) can then be investigated. The technique therefore enables semiautomatic quantitative fluorescence microscopy and has potential as a quality control tool. This work demonstrates the application of the technique to artificial and natural samples and critically discusses its quality, potential, and limitations.