Streptococcus Dysgalactiae Subsp. Equisimilis Isolates Research Articles

Characterization of a prophage and a defective integrative conjugative element carrying the optrA gene in linezolid-resistant Streptococcus dysgalactiae subsp. equisimilis isolates from pigs, Italy.

To investigate the optrA-carrying genetic elements and their transferability in two linezolid-resistant Streptococcus dysgalactiae subsp. equisimilis (SDSE) strains of swine origin. SDSE strains (V220 and V1524) were phenotypically and genotypically characterized. Transferability of oxazolidinone resistance genes (filter mating), genetic elements and relatedness between isolates (WGS) were analysed. Excision of the genetic elements was assayed by inverse PCR. SDSE isolates were resistant to chloramphenicol, florfenicol and linezolid, but susceptible to tedizolid and both carried the optrA gene.In SDSE V220 optrA was located on a 72.9-kb ICESdyV220 inserted in the 3' end of the chromosomal rum gene. It was 94%-96% identical (coverage, from 31% to 61%) to other optrA-carrying ICEs. In-depth ICESdyV220 sequence analysis revealed that optrA was carried by an IMESdyV220 (17.9 kb), also containing the tet(O/W/32/O) gene. Inverse PCR assays excluded the ICESdyV220 mobility. In SDSE V1524, optrA was carried by the ΦSdyV1524 prophage, integrated near the 5' end of the chromosomal had gene, showing a genetic organization similar to that of other streptococcal phage. Conjugation and transduction assays failed to demonstrate the optrA transferability to streptococcal recipients. V220 and V1524 belonged to two novel sequence types (ST704 and ST634, respectively). To the best of our knowledge, this is the first identification of the optrA gene on a prophage and an ICE in SDSE isolates from swine brain.These findings are consistent with the current belief in the key role of bacteriophages and ICEs in the streptococcal evolution and adaptation.

A New Integrative and Mobilizable Element Is a Major Contributor to Tetracycline Resistance in Streptococcus dysgalactiae subsp. equisimilis

Tetracycline resistance in streptococci is mainly due to ribosomal protection mediated by the tet(M) gene that is usually located in the integrative and conjugative elements (ICEs) of the Tn916-family. In this study, we analyzed the genes involved in tetracycline resistance and the associated mobile genetic elements (MGEs) in Streptococcus dysgalactiae subsp. equisimilis (SDSE) causing invasive disease. SDSE resistant to tetracycline collected from 2012 to 2019 in a single hospital and from 2018 in three other hospitals were analyzed by whole genome sequencing. Out of a total of 84 SDSE isolates, 24 (28.5%) were resistant to tetracycline due to the presence of tet(M) (n = 22), tet(W) (n = 1), or tet(L) plus tet(W) (n = 1). The tet(M) genes were found in the ICEs of the Tn916-family (n = 10) and in a new integrative and mobilizable element (IME; n = 12). Phylogenetic analysis showed a higher genetic diversity among the strains carrying Tn916 than those having the new IME, which were closely related, and all belonged to CC15. In conclusion, tetracycline resistance in SDSE is mostly due to the tet(M) gene associated with ICEs belonging to the Tn916-family and a new IME. This new IME is a major cause of tetracycline resistance in invasive Streptococcus dysgalactiae subsp. equisimilis in our settings.

Identification of Novel Mobile Genetic Elements Associated with Resistance to Macrolide and Lincosamide in Streptococcus dysgalactiae subsp. equisimilis

Background: Streptococcus dysgalactiae subsp. equisimilis (SDSE) is an important human pathogen. Recently, several studies have described the incidence of antibiotic resistance for SDSE worldwide, however, the data on the presence of corresponding genes and their possible association with mobile genetic elements are still limited. Objective: The objective of this research was to analyze the macrolide resistance in SDSE and to identify genetic determinants, mechanisms of resistance, and association with mobile genetic elements. Methods: A total of 9 SDSE strains from the collection of Joint Russian-Vietnamese Tropical Research and Technological Center (Hanoi, Vietnam) were used. These strains were previously isolated from throat swabs of children with pharyngotonsillitis in 6 provinces in Vietnam from 2012 to 2015. Antimicrobial resistance was tested by disk diffusion method. The presence of antibiotic resistance genes (ARG) was analyzed by PCR. The strains were characterized by emm typing and multilocus sequence typing (MLST). Illumina sequencing was employed for genome analysis of 4 representative SDSE isolates. Analysis of genetic elements with antibiotic resistance determinants was done using PubMed database and BLAST-searches. Artemis was used for comparative analysis of genetic elements. Results: In our study, we identified emm types that were similar to those reported in other studies. All SDSE isolates remained susceptible to penicillin, but presented alarming level of resistance to macrolides, tetracyclines, and fluoroquinolones. Most of the erythromycin-resistant strains were also characterized by clindamycin-resistance (MLSB phenotype). Both erm and different alleles of mef genes widely distributed among streptococcus pyogenes and Streptococcus pneumoniae were detected, except erm (TR) gene. The genetic elements carrying resistance determinants showed significant interspecies similarities, indicating conjugative transfer of antibiotic resistance genes between streptococcal species. Conclusion: Identification of the novel antibiotic resistance genes in SDSE indicates the necessity of monitoring of antibiotic resistance spreading and gene transfer in this bacterium.

Streptococcus dysgalactiae subsp. equisimilis from invasive and non-invasive infections in Spain: combining epidemiology, molecular characterization, and genetic diversity.

The purpose of this study was to characterize the antibiotic resistance, virulence, and genetic diversity among invasive and non-invasive Streptococcus dysgalactiae subsp. equisimilis (SDSE) isolates. SDSE were isolated from clinical samples of outpatients and inpatients cares in La Rioja region (Spain) during 2012-2015. The analyses performed were susceptibility testing by disc diffusion, resistance and virulence genes by PCR, emm typing by PCR and sequencing, and other molecular typing by SmaI-PFGE and MLST. Forty-two SDSE isolates were recovered (64.3% non-invasive, 35.7% invasive) that were grouped in 31 PFGE patterns, 17 ST, and 14 emm types, being stC1400, stG6792, and stG62647 the most frequent, and stC74a and stC5345 exclusive in invasive SDSE. Twenty-one SDSE were resistant to at least one antibiotic. The erm(TR) and erm(B) genes were linked with resistance to macrolides; tet(M) and tet(T) to tetracycline; dfrF to trimethoprim; ant(6)-Ia and aph(3')-IIIa to aminoglycosides; and the substitutions Asp80Ala in GyrA and Ser79Phe in ParC with resistance to levofloxacin. The sagA, slo, scpA, and ska virulence genes were amplified in 93% SDSE. Streptococcal superantigenic speGdys gene was identified in 80% of invasive and 63% of non-invasive SDSE and correlated with certain emm types (e.g., stG62647 or stG6792). SDSE invasive infections were most frequent in elderly patients, and half of our SDSE were resistant to at least one antibiotic tested. This work is the first detection of tet(T), dfrF, and new substitution in GyrA protein in SDSE. A high diversity of circulating genetic lineages was found among our SDSE.

Detection of Streptococcus pyogenes virulence genes in Streptococcus dysgalactiae subsp. equisimilis from Vellore, India.

Streptococcus dysgalactiae subsp. equisimilis (SDSE), belonging to the group C and G streptococci, are human pathogens reported to cause clinical manifestations similar to infections caused by Streptococcus pyogenes. To scrutinize the distribution of gene coding for S. pyogenes virulence factors in SDSE, 255 isolates were collected from humans infected with SDSE in Vellore, a region in southern India, with high incidence of SDSE infections. Initial evaluation indicated SDSE isolates comprising of 82.35% group G and 17.64% group C. A multiplex PCR system was used to detect 21 gene encoding virulence-associated factors of S. pyogenes, like superantigens, DNases, proteinases, and other immune modulatory toxins. As validated by DNA sequencing of the PCR products, sequences homologous to speC, speG, speH, speI, speL, ssa and smeZ of the family of superantigen coding genes and for DNases like sdaD and sdc were detected in the SDSE collection. Furthermore, there was high abundance (48.12% in group G and 86.6% in group C SDSE) of scpA, the gene coding for C5a peptidase in these isolates. Higher abundance of S. pyogenes virulence factor genes was observed in SDSE of Lancefield group C as compared to group G, even though the incidence rates in former were lower. This study not only substantiates detection of S. pyogenes virulence factor genes in whole genome sequenced SDSE but also makes significant contribution towards the understanding of SDSE and its increasing virulence potential.

Potential Factors Enabling Human Body Colonization by Animal Streptococcus dysgalactiae subsp. equisimilis Strains

Streptococcus dysgalactiae subsp. equisimilis (SDSE) is a pyogenic, Lancefield C or G streptococcal pathogen. Until recently, it has been considered as an exclusive animal pathogen. Nowadays, it is responsible for both animal infections in wild animals, pets, and livestock and human infections often clinically similar to the ones caused by group A streptococcus (Streptococcus pyogenes). The risk of zoonotic infection is the most significant in people having regular contact with animals, such as veterinarians, cattlemen, and farmers. SDSE is also prevalent on skin of healthy dogs, cats, and horses, which pose a risk also to people having contact with companion animals. The main aim of this study was to evaluate if there are features differentiating animal and human SDSE isolates, especially in virulence factors involved in the first stages of pathogenesis (adhesion and colonization). Equal groups of human and animal SDSE clinical strains were obtained from superficial infections (skin, wounds, abscesses). The presence of five virulence genes (prtF1, prtF2, lmb, cbp, emm type) was evaluated, as well as ability to form bacterial biofilm and produce BLIS (bacteriocin-like inhibitory substances) which are active against human skin microbiota. The study showed that the presence of genes coding for fibronectin-binding protein and M protein, as well as BLIS activity inhibiting the growth of Corynebacterium spp. strains might constitute the virulence factors which are necessary to colonize human organism, whereas they are not crucial in animal infections. Those virulence factors might be horizontally transferred from human streptococci to animal SDSE strains, enabling their ability to colonize human organism.

Antimicrobial susceptibility and genetic relationships among Streptococcus dysgalactiae subsp. equisimilis isolates in Rio de Janeiro

Background: Streptococcus dysgalactiae subsp. equisimilis (SDSE) has been increasingly associated with several infectious diseases, ranging from pharyngitis to life-threatening conditions, such as necrotizing fasciitis and streptococcal toxic shock syndrome. However, its molecular epidemiology in some geographical areas remains unclear.Methods: In this study, 44 isolates of SDSE, recovered from noninvasive infections (37) and from carriage (7), during 2008–2013, were submitted to antimicrobial susceptibility testing, emm typing and pulsed-field gel electrophoresis (PFGE) analysis.Results: All isolates were susceptible to ceftriaxone, levofloxacin, penicillin G and vancomycin. Resistance rates to erythromycin was 18.2% and to clindamycin was 6.8%, while 38.7% of the isolates were tetracycline non-susceptible. Macrolide resistance phenotypes were M (5 isolates), iMLSB (2) and cMLSB (1), associated with mefA/E, ermA and ermB genotypes, respectively. Seventeen emm types with 21 subtypes were found, but 6 types (stG653.0, stC1400.0 with three subtypes, stC839.0, stC36.0 with two subtypes, stG480.0 and stG840.0) were detected in 70.4% of the isolates. Six new emm subtypes were identified (stC1400.12, stC1400.13, emm152.1, emm152.2, stG652.6 and stG6792.5). Twenty-five PFGE profiles were obtained from 39 isolates.Conclusions: Congruence between both typing systems was observed, since the majority of isolates belonging to a given emm type clustered together by PFGE. Clones (at least 80% similarity) were also observed among isolates with different emm types, probably due to horizontal recombination of the emm gene. Erythromycin-resistant isolates harbored diverse emm genes and generated different PFGE profiles, showing a polyclonal dissemination of such characteristic among SDSE isolates.

Genetic Diversity in Streptococcus dysgalactiae subsp. equisimilis Isolates from Patients with Invasive and Noninvasive Infections in a Japanese University Hospital (2014-2015).

Streptococcus dysgalactiae subsp. equisimilis (SDSE) isolates with β-hemolysis and carbohydrate groups G or C are increasingly recovered from invasive infections in Japan. The aim of this study was to determine the epidemiological characteristics of SDSE isolates circulating locally among patients with invasive and noninvasive infections. We selected groups G/C β-hemolytic streptococci from a repository at the Clinical Laboratory of Kitasato University Medical Center, from May 2014 through April 2015. Thirteen isolates were identified as SDSE based on the data from API-20 Strep and 16S rRNA sequencing. The samples were from 7 sterile specimens (blood) and 6 non-sterile specimens (pus/sputum/vaginal secretion). Information about the patients with invasive or noninvasive SDSE infections was retrieved from their medical charts. We performed emm genotyping, multilocus sequence typing, a dendrogram analysis of the samples using pulsed-field gel electrophoresis (PFGE), and amplifications of the streptococcal inhibitor of a complement-mediated cell lysis-like gene (sicG) and antimicrobial resistance determinants. We identified 8 different emm genotypes, 8 different sequence types, including 4 novel types, 9 different groups in the PFGE dendrogram, the presence or absence of sicG, and 4 different resistance genotypes. Our observations indicate genetic diversity in SDSE isolates from patients with invasive and noninvasive infections in a Japanese university hospital (2014-2015).

Molecular characterization and antibiotic resistance of clinical Streptococcus dysgalactiae subsp. equisimilis in Beijing, China

Streptococcus dysgalactiae subsp. equisimilis (SDSE) is presently considered as a human pathogen associated with clinical infection. We characterized 56 SDSE isolates collected from two tertiary hospitals in Beijing, China. Sixteen distinct emm types/subtypes were detected, dominated by stG245.0 (32.1%), stG652.0 (10.7%), stG6.1 (10.7%) and stG485.0 (10.7%), and a novel stG840.0 variant type was identified. All isolates possessed virulence genes of sagA and scpA, and most carried slo (98.2%), ska (98.2%) and speGdys (35.7%). By multilocus sequence typing (MLST) analysis, 17 individual sequence types (STs) were distinguished, including 7 newly-identified STs (26.8% of isolates), of which ST127 (30.4%), ST7 (12.5%) and ST44 (10.7%) dominated. Meanwhile, pulsed-field gel electrophoresis (PFGE) analysis revealed 33 pattern types (PTs), which were further combined into 16 pattern clusters (PCs), and 59.3% of isolates were distributed into 2 dominant PCs. Notably, emm types had both close relationship and consistency with STs and PFGE PCs. Furthermore, of 56 SDSE isolates, the predominant antibiotic resistances were erythromycin (71.4%), clindamycin (71.4%) and tetracycline (60.7%). Correspondingly, the prevalent resistance genes of macrolide and tetracycline were erm(B) (78.6%) and tet(M) (73.2%). In addition, multiple point mutations of parC, one of fluoroquinolone resistance genes, were observed (accounting for 75%), and were divided into 12 types, with parC 07 as the predominant type. Our data suggested the wide molecular diversity and distinctive regional features of SDSE from clinical infection in Beijing, China.

Molecular Characterization of Invasive Streptococcus dysgalactiae subsp. equisimilis, Japan.

We collected β-hemolytic streptococci (1,611 isolates) from patients with invasive streptococcal infections in Japan during April 2010-March 2013. Streptococcus dysgalactiae subsp. equisimilis (SDSE) was most common (n = 693); 99% of patients with SDSE infections were elderly (mean age 75 years, SD ±15 years). We aimed to clarify molecular and epidemiologic characteristics of SDSE isolates and features of patient infections. Bacteremia with no identified focus of origin and cellulitis were the most prevalent manifestations; otherwise, clinical manifestations resembled those of S. pyogenes infections. Clinical manifestations also differed by patient's age. SDSE isolates were classified into 34 emm types; stG6792 was most prevalent (27.1%), followed by stG485 and stG245. Mortality rates did not differ according to emm types. Multilocus sequence typing identified 46 sequence types and 12 novel types. Types possessing macrolide- and quinolone-resistance genes were 18.4% and 2.6%, respectively; none showed β-lactam resistance. Among aging populations, invasive SDSE infections are an increasing risk.

Prevalence of emm types and antimicrobial susceptibility of Streptococcus dysgalactiae subsp. equisimilis in Austria

ObjectivesAn increase of severe infections caused by Streptococcus dysgalactiae subsp. equisimilis (SDSE) similar to infections caused by Streptococcus pyogenes has been reported over the last years. Little is known about infections with SDSE in Austria. Therefore, we investigated a collection of 113 SDSE invasive and non-invasive isolates from different infection sites and type of infections as well as patients’ characteristics. MethodsThe isolates were phenotypically identified and emm typed using the enlarged emm database from the Centers for Disease Control and Prevention. Additionally, 13 antimicrobial agents were tested using EUCAST guidelines and virulence genes were investigated. ResultsSevere SDSE infections were most common in elderly men with underlying diseases especially diabetes mellitus. With VitekMS identification of SDSE isolates was successful to the species level only. Emm typing revealed 24 different emm types, one new type and one new subtype. StG485, stG6, stC74a, stG643, and stG480 were the predominant types in this study, stC74a and stG652 in invasive infections and stG643, stC74a and stG485 in non-invasive infections. Resistance was observed to tetracycline (62%), macrolides (13%) with one M phenotype, and clindamycin (12%) presenting 6 constitutive MLSB phenotypes and 8 inducible MLSB phenotypes. Levofloxacin resistance was detected only in one isolate. All isolates tested for virulence genes were positive for scpA, ska, saga and slo. Superantigenic genes were negative except speGdys (positive 17/34; 50%). ConclusionThis paper presents the first report of SDSE infections in Austria. Severe SDSE infections were found mainly in elderly men with underlying diseases. SDSE isolates demonstrated substantial emm type diversity without association with infections site or invasiveness. Analysis of virulence genes showed no significant difference between invasive and non-invasive infections.

Group C Streptococcus dysgalactiae subsp. equisimilis in south-east Brazil: genetic diversity, resistance profile and the first report of human and equine isolates belonging to the same multilocus sequence typing lineage.

Streptococcus dysgalactiae subsp. equisimilis (SDSE) isolates are the most common group C streptococci in humans and reports of invasive infections associated with SDSE have been increasing. Molecular epidemiology studies are an important strategy to trace the emergence and spread of possible well-fit bacterial pathogens of humans and animals. In this work, we analysed the antimicrobial and clonal profiles of 115 SDSE infection and colonization isolates of human and equine origin. PFGE revealed the spread of two main clusters: clone A (57.4%) and clone A (26.1%). Remarkably, two isolates from clone B obtained from human colonization cases displayed identical PFGE patterns to those of three equine infection isolates. In addition, multilocus sequence typing allocated these isolates to ST129 (CC31). All of the SDSE isolates were susceptible to penicillin, vancomycin, gentamicin, levofloxacin and chloramphenicol. Tetracycline and erythromycin resistance rates were 65.2 and 13.9% respectively. Nevertheless, none of the isolates displaying sporadic PFGE patterns showed erythromycin resistance. The majority of erythromycin-resistant isolates from clone A had inducible resistance to macrolides, lincosamines and streptogramins B (iMLSB phenotype), which is associated with the presence of the ermA gene, whereas the resistant isolates from clone B showed the M phenotype, associated with the mefA gene. In conclusion, the data indicated that the analysed collection of SDSE isolates displayed a clonal structure and that the isolates found in human colonization cases could also be involved in equine infections.

Small plasmids in Streptococcus dysgalactiae subsp. equisimilis isolated from human infections in southern India and sequence analysis of two novel plasmids

Small plasmids are frequently found in S. pyogenes isolates from human infections in India. Streptococcus dysgalactiae subsp. equisimilis (SDSE) is a streptococcal subspecies that is genetically similar to S. pyogenes and has a similar ecology. Therefore, we determined the distribution of small plasmids in a collection of 254 SDSE isolates, comprising 44 different emm-types and emm non-typable strains, from southern India, utilizing an established PCR based method. Briefly, 1.2% (n=3) of the isolates were positive for repA (encoding the replication initiation protein A) and 1.6% (n=4) were repB positive (encoding the replication initiation protein B). One isolate (G315) showed a co-detection of repB and dysA (encoding the bacteriocin dysgalacticin) which is characteristic for previously described pDN281/pW2580-like plasmids, observed in SDSE and S. pyogenes. The remaining plasmid bearing isolates showed no characteristic co-detection of known plasmid-associated genes. Thus, plasmids pG271 and pG279, representatives for repB and repA harboring plasmids, respectively, were analyzed. The plasmids pG271 and pG279 could be assigned to the pMV158 and the pC194/pUB110 family of rolling-circle plasmids, respectively. Like the characterized small native plasmids of S. pyogenes from India, the SDSE plasmids discovered and described in this study did not carry any of the known antibiotic resistance genes. SDSE bore less of the investigated small native plasmids that were distinct from the small native plasmids of S. pyogenes of the same geographic region. This indicates a low rate of lateral transfer of these genetic elements between these two related streptococcal species.

Conjugative transfer of ICESde3396 between three β-hemolytic streptococcal species.

BackgroundIntegrative conjugative elements (ICEs) are mobile genetic elements (MGEs) that possess all genes necessary for excision, transfer and integration into recipient genome. They also carry accessory genes that impart new phenotypic features to recipient strains. ICEs therefore play an important role in genomic plasticity and population structure. We previously characterised ICESde3396, the first ICE identified in the β-hemolytic Streptococcus dysgalactiae subsp equisimilis (SDSE) and demonstrated its transfer to single isolates of Streptococcus pyogenes (group A streptococcus, GAS) and Streptococcus agalactiae (group B streptococcus, GBS). While molecular studies found the ICE in multiple SDSE and GBS isolates, it was absent in all GAS isolates examined.ResultsHere we demonstrate that ICESde3396:km is transferable from SDSE to multiple SDSE, GAS and GBS isolates. However not all strains of these species were successful recipients under the same growth conditions. To address the role that host factors may have in conjugation we also undertook conjugation experiments in the presence of A549 epithelial cells and DMEM. While Horizontal Gene Transfer (HGT) occurred, conjugation efficiencies were no greater than when similar experiments were conducted in DMEM. Additionally transfer to GAS NS235 was successful in the presence of DMEM but not in Todd Hewitt Broth suggesting that nutritional factors may also influence HGT. The GAS and GBS transconjugants produced in this study are also able to act as donors of the ICE.ConclusionWe conclude that ICEs are major sources of interspecies HGT between β-hemolytic streptococci, and by introducing accessory genes imparting novel phenotypic characteristics, have the potential to alter the population structure of these species.

Correlation of virulence genes to clinical manifestations and outcome in patients with Streptococcus dysgalactiae subspecies equisimilis bacteremia

Streptococcus dysgalactiae subsp. equisimilis (SDSE) is increasingly recognized as a human pathogen responsible for invasive infection and streptococcal toxic shock syndrome (STSS). The pathogen possesses virulence genes that resemble those found in Streptococcus pyogenes (GAS). We analyzed the association between these specific toxic genes, clinical presentations, and outcome in patients with SDSE infections. Patients (older than 18 years) with community-acquired invasive bacteremia caused by SDSE bacteremia who were undergoing treatment at China Medical University Hospital from June 2007 to December 2010 were included in this study. Multiplex polymerase chain reaction was performed to identify virulence genes of the SDSE isolates. Demographic data, clinical presentations, and outcome in patients with SDSE infections were reviewed and analyzed. Forty patients with 41 episodes of SDSE bacteremia were reviewed. The median age of the patients with SDSE infection was 69.7 years; 55% were female and 78% had underlying diseases. Malignancy (13, 33%) and diabetes mellitus (13, 33%) were the most common comorbidities. The 30-day mortality rate was 12%. Compared with the survivors, the non-survivors had a higher rate of diabetes mellitus (80% vs. 26%), liver cirrhosis (60% vs.11%), shock (60% vs.17%), STSS (60% vs. 8%), and a high Pittsburgh bacteremia score >4 (40% vs. 6%). Most isolates had scpA, ska, saga, and slo genes, whereas speC, speG, speH, speI, speK, smez, and ssa genes were not detected. speA gene was identified only in one patient with STSS (1/6, 17%). All isolates were susceptible to penicillin, cefotaxime, levofloxacin, moxifloxacin, vancomycin, and linezolid. In invasive SDSE infections, most isolates carry putative virulence genes, such as scpA, ska, saga, and slo. Clinical SDSE isolates in Taiwan remain susceptible to penicillin cefotaxime, and levofloxacin.

Genetic diversity and virulence properties of Streptococcus dysgalactiae subsp. equisimilis from different sources

A recent increase in virulence of pathogenic Streptococcus dysgalactiae subsp. equisimilis (SDSE) has been widely proposed. Such an increase may be partly explained by the acquisition of new virulence traits by horizontal gene transfer from related streptococci such as Streptococcus pyogenes (GAS) and Streptococcus agalactiae (GBS). A collection of 54 SDSE strains isolated in Italy in the years 2000-2010 from different sources (paediatric throat carriage, invasive and non-invasive diseases) was characterized by emm typing and pulsed-field gel electrophoresis (PFGE) analysis. The virulence repertoire was evaluated by PCR for the presence of GAS superantigen (spe) genes, the streptolysin S (sagA) gene, the group G fibronectin-binding protein (gfbA) gene and GAS-GBS alpha-like protein family (alp) genes; moreover, the ability to invade human epithelial cells was investigated. Resistance to tetracycline, erythromycin and clindamycin was assessed. The combined use of emm typing and PFGE proved to be a reliable strategy for the epidemiological analysis of SDSE isolates. The most frequent emm types were the same as those more frequently reported in other studies, thus indicating the diffusion of a limited number of a few successful emm types fit to disseminate in humans. The speG gene was detected in SDSE strains of different genetic backgrounds. Erythromycin resistance determined by the erm(T) gene, and the unusual, foggy MLSB phenotype, observed in one and seven strains, respectively, have never previously, to our knowledge, been reported in SDSE. Moreover, a new member of the alp family was identified. The identification of new antibiotic and virulence determinants, despite the small size of the sample analysed, shows the importance of constant attention to monitoring the extent of lateral gene transfer in this emerging pathogen.

Molecular mechanisms of Streptococcus dysgalactiae subsp equisimilis enabling intravascular persistence

Streptococcus dysgalactiae subsp. equisimilis (SDSE) can cause recurrent bacteremic infection. We have characterized novel virulence properties of an SDSE isolate of type stG485.0 that caused severe sepsis three times in a patient despite that he had opsonizing antibodies to the isolate. An infected aortic aneurysm was suspected to be the focus for the persisting bacteria. For the first time we show that this SDSE isolate, as well as other invasive SDSE isolates, aggregate human platelets and efficiently internalize into human endothelial cells. These properties may aid SDSE to persist and could explain the tendency of SDSE to cause recurrent bacteremia.