Restricted association between biotypes and serotypes within group A streptococci

Molecular analysis of Streptococcus pyogenes strains isolated from Chinese children with pharyngitis

Streptococcus pyogenes is an important gram-positive bacterial pathogen that causes various human diseases, of which streptococcal pharyngitis is the most common. In this work, a total of 185 S. pyogenes isolated from Chinese children with pharyngitis was analyzed by superantigen (SAg) genes, emm genotyping, and pulsed-field gel electrophoresis (PFGE). Fifty-eight (31.4%) isolates were also typed by multilocus sequence typing (MLST). The results indicate that most of the emm1 isolates possessed speA (88.5%) and speJ (83.6%), and few isolates possessed speI gene (13.1%). In contrast, none of the emm12-type isolates possessed speJ; few isolates possessed speA (5.2%); and most of the isolates possessed speI (91.7%). PFGE analysis revealed 25 different clusters, and MLST was performed for 2 predominant emm-type isolates; emm12 isolates belonged to ST36 while emm1 isolates belonged to ST28. As far as this collection is concerned, emm1 and emm12 are the prevalent genotypes among S. pyogenes strains associated with children's pharyngitis in China. Most of the pharyngitis strains can be covered by a 26-valent vaccine. A strong correspondence is found only in the direction of emm type for both SAg profiles and PFGE types but not in the reverse direction.

Epidemiological markers of Streptococcus pyogenes strains in Tunisia

To further understand the epidemiology of Streptococcus pyogenes or group A streptococcus (GAS) infections in Tunisia, phenotypic and genomic markers of GAS isolates, including antibiotic susceptibility, biotypes, T and emm types and toxin gene profiles, have been characterized. A total of 103 isolates, collected between 2000 and 2006, were investigated; 47 were recovered from invasive infections, and 56 from non-invasive infections. Rates of resistance to tetracycline, erythromycin, clindamycin and rifampin were 70.8%, 4.8%, 4.8% and 0.9%, respectively. High levels of resistance to streptomycin and kanamycin were observed in 1.9% and 4.8% of isolates, respectively. Biotype 3 was most common. Twenty different T patterns were observed, with a predominance of T3/13/B3264, and 38 different emm types. In both invasive and non-invasive isolates, emm118 (9.7%), emm42 (8.7%), emm1 (7.8%), st432 (6.8%), emm28 (5.8%) and emm76 (5.8%) were the most prevalent types; emm1, emm76 and emm18 were mainly observed among invasive infections, whereas emm118 (12.5%), emm42 (10.7%) and emm28 (8.9%) were predominant among non-invasive infections. The speB gene was detected in all isolates, but there were variable frequencies of speA, speC and ssa (20.3%, 32% and 25.2% respectively). Significant associations of emm1, emm18 and emm3 with speA and of emm4 and st432 with ssa were found. This first report from Tunisia revealed a unique emm distribution of GAS that differs from those of other regions. This information on the distribution of such emm types will be useful for the development of an appropriate vaccine in a country where the incidence of rheumatic fever remains high.

Clinical and microbial characteristics of invasive Streptococcus pyogenes disease in New Caledonia, a region in Oceania with a high incidence of acute rheumatic fever

New Caledonia is an archipelago in the South Pacific with a high prevalence of acute rheumatic fever and rheumatic heart disease. Conducted in 2006, this study aimed at characterizing clinical manifestations and microbial features of isolates obtained from invasive Streptococcus pyogenes disease. Clinical and demographic data were collected prospectively. Isolates were biotyped, T typed, emm sequenced, and tested for antibiotic susceptibility. Detection of the speA, speB, speC, and ssa genes was also carried out. The estimated annual incidence of invasive S. pyogenes disease in 2006 was high at 38 cases/100,000 inhabitants in New Caledonia. Invasive isolates were obtained from 90 patients with necrotizing fasciitis (41 cases), bacteremia with no identified focus (12 cases), myositis (10 cases), septic arthritis (9 cases), erysipelas (8 cases), postpartum infection (4 cases), myelitis and osteomyelitis (3 cases), severe pneumonia (2 cases), and endocarditis (1 case). The most frequent associated comorbidities were skin lesions (71%) and obesity (29%). Thirty-one different emm types were identified, and the following six accounted for 54% of the isolates: emm15 (15.5%), emm92 (12.2%), emm106 (8.9%), emm74 (6.7%), emm89 (5.6%), and emm109 (5.6%). The speA, speC, and ssa genes were expressed at different frequencies in the various emm types. The first epidemiological study of invasive S. pyogenes disease in New Caledonia highlights that emm type distribution is particular and should be taken into account in the development of an appropriate vaccine. These findings support the prevention of pyoderma and other cutaneous lesions in order to limit the development of both invasive disease and poststreptococcal sequelae in the South Pacific.

Biotypes of group A streptococci from patients with pharyngitis and soft tissue infections

This study determined the biotypes of group A streptococci (GAS) isolated from 66 pharyngeal and 62 skin and soft-tissue infections. Among all GAS isolates tested, the most common biotypes were 1 and 3, irrespective of the isolation source and the severity of clinical symptoms. However, compared with the pharyngeal group, a more heterogeneous distribution of biotypes was observed among the cutaneous group of isolates, including seven isolates that were non-typeable but had an identical biotype pattern, suggesting that they may represent a new biotype.

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.

Emergence of macrolide-resistant Streptococcus pyogenes strains in French children

We studied the antimicrobial susceptibility of 322 Streptococcus pyogenes throat isolates from French children and their serotype and genomic diversity. A total of 22.4% were erythromycin resistant, and 69.4, 4.2, and 26.4% of these isolates harbored ermB, ermA, and mefA, respectively. Increasing resistance in France is mainly associated with a few emm type 28 clones.

Clonal spread of emm type 28 isolates of Streptococcus pyogenes that are multiresistant to antibiotics

Fifty-three pharyngitis-related and invasive isolates of Streptococcus pyogenes that are resistant to bacitracin were collected. They were also resistant to streptomycin, kanamycin, macrolides, lincosamides, and streptogramin B. These multiresistant isolates were of emm type 28 and clonally related as shown by pulsed-field gel electrophoresis.

Biotypes of group A streptococci isolated from children

Thirty-eight isolates of group A streptococci from patients with pharyngitis, 13 isolates from patients with pyoderma and 28 carrier strains were subjected to biotyping by carbohydrate fermentation tests and production of beta-glucuronidase. Biotype 10 was observed most frequently among clinical isolates and biotypes 3 and 4 were most common among carrier isolates.

Characteristics of Streptococcus pyogenes serotype M1 and M3 isolates from patients in Japan from 1981 to 1997

Streptococcus pyogenes isolates obtained in 1981 to 1997 from patients and healthy subjects were characterized by pulsed-field gel electrophoresis (PFGE) patterns, biotyping, and the presence of spe genes encoding streptococcal pyrogenic exotoxins. Changes in the profiles were shown in the serotype M1/T1 isolates from pharyngitis over this period, but not in serotype M3/T3 isolates. The characteristics of isolates from patients with toxic shock-like syndrome (TSLS) were comparable to those of the other isolates, including those from healthy subjects. This finding suggests that further phenotypic and molecular characterization, such as investigating the genomic difference represented by the pathogenicity island, of isolates with apparently the same profiles would be necessary to determine the etiology of diseases caused by S. pyogenes, including TSLS.

Clonal differences among erythromycin-resistant Streptococcus pyogenes in Spain

The aim of this study was to determine whether the high levels of erythromycin resistance in Streptococcus pyogenes found in Spain are due to the introduction and spread of one or more clones. Phenotypic and genotypic techniques were used to characterize all erythromycin-resistant S. pyogenes (ErR) isolated in Gipuzkoa, Spain, in the last 10 years and 128 ErR isolated in Vitoria and Madrid during 1996. Of 437 ErR, 97% had the M phenotype; all 283 of the strains studied had the mefA determinant of resistance. After biotyping, T serotyping, emm typing, and genotyping, four major clones were detected. Clones B (biotype I, type T4, emm4, pulsed-field gel electrophoresis [PFGE] II) and D (biotype V, type T8.25, emm75, PFGE IV) comprised 78.8% of all ErR. The resistance of S. pyogenes to erythromycin was mainly due to an efflux mechanism of resistance (M phenotype); few clones were responsible for it.

Simplification of a locus-specific DNA typing method (Vir typing) for Streptococcus pyogenes

We describe a simplification of a highly discriminatory molecular typing method, called Vir typing, for Streptococcus pyogenes (D. Gardiner, J. Hartas, B. Currie, J. D. Mathews, D. J. Kemp, and K. S. Sriprakash, PCR Methods Appl. 4:288-293, 1995). The procedure can be completed within a day, is reproducible, and can be applied directly to colonies growing on primary culture plates, allowing rapid establishment of strain identity in an outbreak.

Molecular epidemiology of Streptococcus pyogenes in an area where acute pharyngotonsillitis is endemic

During an open clinical trial in an area where streptococcal infections are hyperendemic, we studied the genetic polymorphism of Streptococcus pyogenes isolates collected from patients and from healthy carriers living in close contact with them. The clonal diversity of isolates was analyzed by pulsed-field gel electrophoresis with three restriction enzymes (SmaI, ApaI, and SacII). The pharynx of each patient and healthy carrier was colonized by a single clone, suggesting the clonal nature of streptococcal colonization in individuals. Among 52 isolates obtained from patients with acute pharyngotonsillitis, we found 14 genetically unrelated clones, showing the genetic diversity of S. pyogenes. However, two clones belonging to the M1 and M12 serotypes represented about 70% of isolates in carriers and patients. Pharyngeal colonization in cured patients was monitored for 3 to 4 months. After the initial elimination of S. pyogenes following antibiotic therapy, the rate of recolonization was high by day 30 (about 20%) and was also at that level between days 90 and 120; this was similar to the carriage rate in family contacts. Thus, cured patients can be recontaminated by unrelated clones, suggesting that colonization of healthy carriers might be a potential source of spread and redistribution of S. pyogenes isolates.

Molecular epidemiology of impetiginous group A streptococcal infections in aboriginal communities of northern Australia

Group A streptococcal infections among the Aboriginal communities of the Northern Territory of Australia are endemic, with a concurrently high rate of the postinfection sequelae of rheumatic fever and acute post-streptococcal glomerulonephritis. The majority of the group A streptococcal isolates from the Northern Territory are not typeable by M typing. We recently developed a novel genotyping method, Vir typing. A preliminary study using this method discriminated all the M-nontypeable (MNT) isolates. Vir typing is based on restriction fragment length polymorphisms of the 4- to 7-kb Vir regulon of group A streptococci, which contains a number of genes, including emm (the gene for M protein). A total of 407 isolates of group A streptococci obtained from four Aboriginal communities over a 4-year period were typed by this genotyping method. Forty-two distinct genotypes were found among the isolates, including 22 among the MNT isolates. The correlation between Vir type and M type was good. This genotyping method allows the characterization of all group A streptococcal isolates from Aboriginal communities in the Northern Territory. We also propose that Vir typing be used in conjunction with M typing for epidemiological surveillance in geographical regions where the majority of isolates are MNT.

rRNA gene restriction patterns of Streptococcus pyogenes: epidemiological applications and relation to serotypes

The use of rRNA gene restriction fragment length polymorphism analysis (ribotyping) to subtype Streptococcus pyogenes strains was investigated. Sixty-eight S. pyogenes strains, including 17 reference strains and 51 isolates from blood, acute or chronic pharyngitis, and food-borne outbreaks, were characterized by determination of both their rDNA restriction fragment length polymorphism profiles and their serotypes (T and M). Total DNA was cleaved with five selected restriction enzymes and then probed with a digoxigenin-labeled stretch of 1,063 bp hybridizing with 16S rRNA genes. Fifteen and nine distinct patterns were generated with SacI and XhoI, respectively, and five patterns were generated with each of the three additional restriction enzymes. With the combination SacI-XhoI, a total of 21 distinct ribotypes were obtained among the 68 isolates. This number was not increased by the results obtained with the other restriction enzymes. All strains tested were typeable. All isolates from each food-borne outbreak belonged to the same ribotype, and all isolates (pre- and posttreatment) from each child with chronic pharyngitis also belonged to the same ribotype, suggesting antibiotic treatment failures. A discriminatory index was calculated for the 47 isolates which were epidemiologically unrelated, using the Hunter-Gaston formula. This index reached 0.955 when the combination SacI-XhoI was used, showing the good discriminatory power of this typing method. Therefore, ribotyping proved to be a molecular method of interest to subtype S. pyogenes. Moreover, there was some correlation between ribotyping and serotyping, as several ribotypes were related to a unique distinct M serotype.