Reemergence of emm1 and a changed superantigen profile for group A streptococci causing invasive infections: results from a nationwide study

The ongoing Streptococcus pyogenes (Group A Streptococcus) outbreak in London, United Kingdom, in December 2022: a molecular epidemiology study

OBJECTIVES

Epidemiological and whole-genome sequencing analysis of an ongoing outbreak of Streptococcus pyogenes (Group A Streptococcus) in London (United Kingdom).

METHODS

Prospective identification of Group A Streptococcus cases from a diagnostic laboratory serving central and south London between 27 November and 10 December 2022. Case notes were reviewed and isolates were retrieved. Case numbers were compared with the previous 5 years. Whole-genome sequencing was performed with long-read, nanopore technology for emm typing and identification of superantigen genes. Associations of pathogen-related factors with an invasive disease were assessed by single-variable and multi-variable logistic regression.

RESULTS

Case numbers began increasing in October 2022 from a baseline of 2.0 cases per day, and in December 2022, the average daily case numbers reached 10.8 cases per day, four-fold the number usually seen in winter. A total of 113 cases were identified during the prospective study period. Three quarters (86/113, 76%) were paediatric cases, including 2 deaths. Of 113 cases, 11 (10%) were invasive. In total, 56 isolates were successfully sequenced, including 10 of 11 (91%) invasive isolates. The emm12 (33/56, 59%) and emm1 (9/56, 16%) types were predominant, with 7 of 9 (78%) emm1 isolates being from the M1uk clone. The majority of invasive isolates had superantigen genes spea (7/10, 70%) and spej (8/10, 80%), whereas, in non-invasive isolates, these superantigen genes were found less frequently (spea: 5/46, 11% and spej: 7/46, 15%). By multivariable analysis of pathogen-related factors, spea (OR 8.9, CI 1.4-57, p 0.020) and spej (OR 12, CI 1.8-78, p 0.011) were associated with invasive disease.

CONCLUSIONS

emm12 and emm1 types predominate in the ongoing outbreak, which mainly affects children. In this outbreak, the spea and spej superantigen genes are associated with the severity of presentation.

Severe acute otitis media and mastoiditis caused by group A beta-hemolytic streptococcus

OBJECTIVE

To describe the characteristics, diagnostics, treatment, and outcome of severe acute otitis media (AOM) and acute mastoiditis (AM) caused by group A beta-hemolytic streptococcus (GAS).

STUDY DESIGN

A retrospective cohort study.

METHODS

The yearly incidence of inpatient care-needing GAS AOM/AM patients in our hospital catchment area between 2002 and 2018 was investigated. A detailed analysis was performed for cases treated during the last GAS epidemic in 2017-2018. Anamnesis, signs and symptoms, pure-tone audiometry results, treatment, complications, and outcome were collected from medical charts. Patients responded to an otology-specific health-related quality of life survey (EOS-16) 1.5 to 3 years after their treatment.

RESULTS

The number of GAS infections peaks at approximately 7-year intervals. During 2017 and 2018, altogether 37 patients (29 adults and 8 children) were hospitalized due to GAS AOM/AM. AM was diagnosed in 14 (38%) patients. The disease progression was typically very rapid. At presentation, all patients had severe ear pain, 68% tympanic membrane perforation and discharge, 43% fever, and 43% vertigo. In pure-tone audiometry, there was usually a marked mixed hearing loss at presentation. There was a significant recovery in both air and bone conduction thresholds; the pure tone average improvement from presentation was 32.3 ± 14.8 dB. Rapid strep tests (RST) proved to be more sensitive than bacterial culture in identifying GAS as a cause of AOM/AM.

CONCLUSION

GAS AOM/AM has a rapid onset. Hearing loss usually includes a sensorineural component, which is usually reversible with adequate treatment. RST seems to be useful in detecting GAS from middle ear discharge.

LEVEL OF EVIDENCE

4.

Streptococcus pyogenes Infective Endocarditis-Association With Injection Drug Use: Case Series and Review of the Literature

BACKGROUND

Streptococcus pyogenes, or Group A Streptococcus (GAS), is not considered a typical cause of infective endocarditis (IE), but has anecdotally been observed in unexpectedly high rates in people who inject drugs (PWID) at our institution.

METHODS

All cases of possible or definite GAS IE per Modified Duke Criteria in adults at an academic hospital between 11/15/2015 and 11/15/2020 were identified. Medical records were reviewed for demographics, comorbidities, treatment, and outcomes related to GAS IE. The literature on cases of GAS IE was reviewed.

RESULTS

Eighteen cases of probable (11) or definite (7) GAS IE were identified; the mean age was 38 years, and the population was predominantly female (56%) and Caucasian (67%), which is inconsistent with local population demographics. Sixteen cases were in people who inject drugs (PWID; 89%); 14 were also homeless, 6 also had HIV (33%), and 2 were also pregnant. Antibiotic regimens were variable due to polymicrobial bacteremia (39%). One patient underwent surgical valve replacement. Four patients (22%) died due to complications of infection. The literature review revealed 42 adult cases of GAS IE, only 17 of which were in PWID (24%).

CONCLUSIONS

The 16 cases of possible and definite GAS IE in PWID over a 5-year period in a single institution reported nearly doubles the number of cases in PWID from all previous reports. This suggests a potential increase in GAS IE particularly in PWID and PWH, which warrants further epidemiologic investigation.

Beta-Hemolytic Streptococci and Necrotizing Soft Tissue Infections

β-hemolytic streptococci are major causes of necrotizing soft tissue infections (NSTIs), Streptococcus pyogenes (group A streptococcus; GAS) in particular. NSTIs caused by Streptococcus dysgalactiae (SD) have also been reported. In the INFECT cohort of 409 NSTIs patients, more than a third of the cases were caused by GAS (31%) or SD (7%). Risk factors of streptococcal NSTIs compared to streptococcal cellulitis have previously been largely unknown. The INFECT study confirmed blunt trauma as an important risk factor. In addition, absence of pre-existing skin lesions and a lower BMI were associated with NSTIs. The study also confirmed that septic shock is more frequent in GAS cases than in other types of NSTIs. Septic shock was also among several predictors of mortality. The role of intravenous immunoglobulin (IVIG) in streptococcal NSTIs has been unclear. In the INFECT cohort, IVIG treatment was associated with increased survival. As in other studies, a significant microbial diversity was observed, but with predominance of a few emm types. Overall, the INFECT study gives a comprehensive and contemporary picture of the clinical characteristics and the microbes involved in streptococcal NSTIs. The reported severity of disease underscores the need for new efforts aimed at identifying novel diagnostic measures and improved treatment.

Antibodies to the conserved region of the M protein and a streptococcal superantigen cooperatively resolve toxic shock-like syndrome in HLA-humanized mice

Invasive streptococcal disease (ISD) and toxic shock syndrome (STSS) result in over 160,000 deaths each year. We modelled these in HLA-transgenic mice infected with a clinically lethal isolate expressing Streptococcal pyrogenic exotoxin (Spe) C and demonstrate that both SpeC and streptococcal M protein, acting cooperatively, are required for disease. Vaccination with a conserved M protein peptide, J8, protects against STSS by causing a dramatic reduction in bacterial burden associated with the absence of SpeC and inflammatory cytokines in the blood. Furthermore, passive immunotherapy with antibodies to J8 quickly resolves established disease by clearing the infection and ablating the inflammatory activity of the M protein, which is further enhanced by addition of SpeC antibodies. Analysis of 77 recent isolates of Streptococcus pyogenes causing ISD, demonstrated that anti-J8 antibodies theoretically recognize at least 73, providing strong support for using antibodies to J8, with or without antibodies to SpeC, as a therapeutic approach.

Epidemiology and distribution of 10 superantigens among invasive Streptococcus pyogenes disease in Germany from 2009 to 2014

A nationwide laboratory-based surveillance study of invasive S. pyogenes infections was conducted in Germany. Invasive isolates (n = 719) were obtained between 2009 and 2014. Most isolates were obtained from blood (92.1%). The proportions of isolates from cerebrospinal fluid, pleural fluid, synovial fluid and peritoneal fluid were 3.9%, 1.8%, 1.7% and 0.6%, respectively. The most common emm types were emm 1 (31.8%), emm 28 (15.4%) and emm 89 (14.5%). The most common superantigen genes (speA, speC, speG, speH, speI, speJ, speK, speL, speM, ssa) identified from S. pyogenes were speG (92.1%), speJ (50.9%), and speC (42.0%). Significant associations of superantigen genes with underlying conditions or risks were observed in speG, speH, speJ, and speK. Significant associations between emm types or superantigen genes with clinical complications were observed in emm type 3 and in superantigen gene speA 1-3. Most frequent clinical manifestations included sepsis 59.4%, STSS 6.3%, meningitis 5.4%, and necrotizing fasciitis 5.0% (significantly associated with emm1).

Virulence factors of Streptococcus pyogenes strains from women in peri-labor with invasive infections

Invasive group A streptococcal (GAS) infections constitute an important epidemiological problem. Many cases occur in women during the postnatal period. The objective of this study was to evaluate the presence of the genes responsible for production of iron-chelating protein (perR) and superantigens (speA, speB, speC, speF, speG, speH, speI, speJ, speK, speL, speM, smeZ, and ssa) in S. pyogenes strains isolated from invasive infections in women after delivery. Furthermore, this study sought to verify whether S. pyogenes strains show special phenotypic and genotypic (sla, spy1325) characteristics that may play a decisive role in adherence to the genital tract epithelium. Moreover, the emm-types and antibiotic susceptibility were determined. We tested 30 invasive S. pyogenes strains isolated from postpartum invasive infection and 37 GAS control strains isolated from the genital tracts of asymptomatic multiparous women. The majority of the tested strains were shown to express two types of emm genes (1 and 28), though emm -12, -28, -75 and -89 were uniquely expressed in the group of strains isolated from invasive infections. A significantly higher prevalence of perR in the strains from puerperal fever was shown. Significant differences were also found between the two groups with respect to the incidence of the genes related to adherence; GAS strains originating from women with sepsis/puerperal fever showed presence of these genes less frequently than those of the control group. Although differences in frequencies of the gene coding for various superantigens were noted between the compared groups of GAS strains, they were not significant.

Outbreak of Streptococcus pyogenes emm type 58 in a high dependency unit of a level-1 trauma center of India

Background and Aims:

Group A Streptococcus (GAS) can cause illnesses ranging from self-limited to severe, life-threatening, invasive infections. The objective of the following study was to investigate a suspected Streptococcus pyogenes outbreak in a high dependency unit (HDU) of our trauma center.

Materials and Methods:

All the isolates of beta hemolytic Streptococci were identified by standard microbiological methods, Vitek 2 system and latex agglutination tests. Antimicrobial susceptibility testing was performed as recommended by Clinical Laboratory Standards Institute. Exotoxin genes, including speA, speB, speC, speF, smeZ, ssa, speG, speH, speJ, speL, speM and speI were detected by polymerase chain reaction (PCR). The emm types of isolates of S. pyogenes were determined by sequencing the variable 5’ end of emm gene after amplification by PCR.

Results:

In a 28 bedded poly-trauma ward with a four bedded HDU three out of four patients developed S. pyogenes emm type 58 infection. The strain was macrolide and tetracycline resistant and produced the Streptococcal pyrogenic exotoxins speB, speC, speG, speF and smeZ. Surveillance sampling was done for investigation from patients, health-care workers and environmental samples.

Conclusion:

An outbreak of GAS infections was established caused by the uncommonly reported emm type 58. The outbreak was controlled by prompt treatment, intensive surveillance, feedback and training.

Molecular markers for the study of streptococcal epidemiology

Diseases caused by Streptococcus pyogenes (Group A streptococcus, GAS) range from superficial infections such as pharyngitis and impetigo to potentially fatal rheumatic heart disease and invasive disease. Studies spanning emm-typing surveillance to population genomics are providing new insights into the epidemiology, pathogenesis, and biology of this organism. Such studies have demonstrated the differences that exist in the epidemiology of streptococcal disease between developing and developed nations. In developing nations, where streptococcal disease is endemic, the diversity of GAS emm-types circulating is much greater than that found in developed nations. An association between emm-type and disease, as observed in developed countries is also lacking. Intriguingly, comparative genetic studies suggest that emm-type is not always a good predictor of the evolutionary relatedness of geographically distant isolates. A view of GAS as a highly dynamic organism, in possession of a core set of virulence genes that contribute to host niche specialization and common pathogenic processes, augmented by accessory genes that change the relative virulence of specific lineages is emerging. Our inability to definitively identify genetic factors that contribute to specific disease outcome underscores the complex nature of streptococcal diseases.

Epidemiology of invasive Streptococcus pyogenes disease in Germany during 2003-2007

A nationwide laboratory-based surveillance study of invasive Streptococcus pyogenes infections was conducted in Germany. Invasive isolates (n=586) were obtained between 2003 and 2007. Most isolates were obtained from blood (53.9%) or skin lesions (17.6%). The most common emm types were emm 1 (30.5%), emm 28 (18.3%) and emm 3 (9.6%). Overall, speA was positive in 45.9%, speC in 44.7% and ssa in 14.8% of isolates. SpeA was common in emm type 1 (100%) and emm type 3 (96.4%), whereas speC was often observed in emm type 28 (93.5%). The most frequent clinical manifestations included sepsis (40.1%), necrotizing fasciitis (20.8%) and streptococcal toxic shock syndrome (16.6%). All isolates were susceptible to penicillin G, cefotaxime and levofloxacin. Tetracycline shows the highest rate of resistant or intermediate isolates with 11.6%, followed by clarithromycin (5.5%) and clindamycin (1.2%). The most prominent trend is the reduction of tetracycline-nonsusceptible isolates from 18.6% in 2003 to 8.9% in 2007.

A single nucleotide mutation results in loss of enzymatic activity in the hyaluronate lyase gene of Streptococcus pyogenes

Group A streptococci produce a variety of extracellular proteins, many of which are considered to be virulence factors. One of these is hyaluronate lyase (HylA), an enzyme capable of degrading the extracellular matrix of the host as well as the bacterial capsule. The current study examined three genotypes of hylA (full, truncated and deleted). Only isolates containing a full-length gene produced an enzymatically active hyaluronate lyase; however, truncation of the protein was not the reason for loss of activity. A single nucleotide substitution, resulting in an amino acid change at position 199 of the lyase was present in a highly-conserved region of the protein in isolates not producing active enzyme. In serotypes 4 and 22, those producing active enzymes, this residue was an aspartic acid, in serotypes not showing hyaluronate lyase activity, it was a valine. Site-directed mutagenesis indicated the loss of enzymatic activity of the hyaluronate lyase is in part determined by the mutation resulting in an amino acid residue change. This mutation results in an inactive form of the enzyme and is found in the more virulent serotypes of Streptococcus pyogenes, suggesting that hyaluronate lyase could interfere with the disease process, in essence being an anti-virulence factor.

Group A streptococcal puerperal sepsis: initial characterization of virulence factors in association with clinical parameters

Group A beta-hemolytic streptococcus (GAS) is an uncommon but potentially fatal source of postpartum infection. Pathogenesis in invasive GAS infections has been linked to bacterial virulence factors. In this study, we sought to provide an initial description of potential virulence factors in association with puerperal morbidity by virtue of specific M-protein type antigens. Women with confirmed GAS puerperal infection in the Salt Lake City region were prospectively identified over a 6-year interval (1991-1997). From this cohort, GAS isolates were analyzed with respect to M-serotype and presence of genes encoding the Streptococcal Pyogenic Exotoxins A and B (SPE-A and SPE-B). Bacterial isolates from 18 subjects with GAS puerperal infection underwent M-serotyping and PCR-based genotyping for the speA and speB genes. Among these, 8/18 subjects manifest criteria of severe disease. All 18 isolate strains expressed speB; 6/18 isolates expressed speA. Of the M-serotypes, 8/8 severe disease isolates expressed M-types 1 (N=3) or 28 (N=5). Pulse-field gel electrophoresis did not indicate an outbreak strain among similar isolates. We conclude that in this initial characterization, morbidity among women with GAS puerperal infection is associated with M-types 1 and 28, but not speB genotype.

Characterization of emm types and superantigens of Streptococcus pyogenes isolates from children during two sampling periods

The characteristics of 359 group A streptococcal (GAS) isolates collected from Chinese paediatric patients in two periods (1993-1994, 2005-2006) were studied. Isolates were assigned to emm types and assayed for eight superantigen (SAg) genes (speA, speC, speH, speI, speG, speJ, ssa, SMEZ). Types emm1 and emm12 were consistently the most prevalent during the two periods, while others varied in frequency. GAS isolates carrying six or more SAg genes increased from 46.53% (1993-1994) to 78.39% (2005-2006); ssa, speH and speJ genes (P<0.05) increased but speA declined (P<0.05). SAg gene profiles were closely associated with the emm type, but strains of the same emm type sometimes carried different SAg genes in the two periods. No significant difference in emm-type distribution and SAg gene profile was noted between isolates from different diseases. These data may contribute towards the development of a GAS vaccine in China.

Superantigen gene profile diversity among clinical group A streptococcal isolates

This study examines the diversity of superantigen gene profiles between and within emm-genotypes of 92 clinical group A streptococcal isolates (30 STSS, 24 sepsis, 25 erysipelas, and 12 tonsillitis) collected in Sweden between 1986 and 2001. The emm-genotype and the distribution of smeZ, speG, speJ, speA, speC, speH, speI, speK/L, speL/M, speM, and ssa genes, and the smeZ allelic variant were determined using PCR and DNA sequencing. Forty-five emm1 isolates revealed 10 superantigen gene profiles. One profile dominated and was identified in 22 isolates collected over 14 years. The results indicate that a selective advantage maintained this genotype in circulation. The superantigen content among the emm1 isolates ranged from three to seven, with smeZ-1, speG, and speA present in all but one profile. The 47 isolates of 27 other emm-genotypes exhibited 29 superantigen gene profiles. Thus, the distribution of superantigen genes was highly variable within isolates regardless of emm-genotype. Two novel emm1 subtypes and 14 novel smeZ allelic variants were identified. The 22 smeZ alleles were generally linked to the emm-genotype. The results of the investigation show that superantigen gene profiling is useful for tracking spread of clones in the community.

The intrinsic immunoglobulin g endopeptidase activity of streptococcal Mac-2 proteins implies a unique role for the enzymatically impaired Mac-2 protein of M28 serotype strains

IdeS, a secreted cysteine protease of the important human pathogen Streptococcus pyogenes, interferes with phagocytic killing by specifically cleaving the heavy chain of immunoglobulin G (IgG). Two allelic variants of the enzyme have been described, the IgG-specific endopeptidase, IdeS (or Mac-1) and Mac-2, a protein with only weak IgG endopeptidase activity, which has been suggested to interfere with opsonophagocytosis by blocking Fcgamma receptors of phagocytic cells. However, despite the fact that Mac-2 proteins interact with Fcgamma receptors, no inhibition of reactive oxygen species (ROS) production, opsonophagocytosis, or streptococcal killing by Mac-2 has been reported. In the present study, Mac-2 proteins are shown to contain IgG endopeptidase activity indistinguishable from the enzymatic activity exhibited by IdeS/Mac-1 proteins. The earlier reported weak IgG endopeptidase activity appears to be unique to Mac-2 of M28 serotype strains (Mac-2(M28)) and is most likely due to the formation of a disulfide bond between the catalytic site cysteine and a cysteine residue in position 257 of Mac-2(M28). Furthermore, Mac-2 proteins are shown to inhibit ROS production ex vivo, independently of the IgG endopeptidase activity of the proteins. Inhibition of ROS generation per se, however, was not sufficient to mediate streptococcal survival in bactericidal assays. Thus, in contrast to earlier studies, implicating separate functions for IdeS and Mac-2 protein variants, the current study suggests that Mac-2 and IdeS are bifunctional proteins, combining Fcgamma receptor binding and IgG endopeptidase activity. This finding implies a unique role for Mac-2 proteins of the M28 serotype, since this serotype has evolved and retained a Mac-2 protein lacking IgG endopeptidase activity.

Sudden death caused by fulminant bacterial infection: background and pathogenesis of Japanese adult cases

OBJECTIVE

To analyze a risk factor for the onset of fulminant bacterial infection.

PATIENTS AND METHODS

Nine unexpected acute death cases were clinicopathologically analysed. All cases represented the sudden onset of shock symptom, led to acute death within a few days, and later bacteremia was identified. Pathogens were Streptococcus pneumoniae (S. pneumoniae) (5 cases), group A beta Hemolytic Streptococcus pyogenes (S. pyogenes) (3 cases), and Vibrio vulnificus (V. vulnificus) (1 case).

RESULTS

Seven of the nine patients had underlying chronic illness. S. pneumoniae infection was associated with splenic dysfunction, and group A beta Hemolytic S. pyogenes and V. vulnificus infections were associated with alcoholic liver injury. Group A beta hemolytic S. pyogenes and V. vulnificus infections involved necrotizing fasciitis, and alcoholic liver cirrhosis was confirmed in two of the four patients.

CONCLUSION

Despite the different type of bacteria, the onset of fulminant bacterial infection depended upon depressed bacterial phagocytosis in the liver or spleen. Underlying chronic illnesses should be identified as a predisposing common risk factor. It is important to understand the relations between underlying chronic illness and the onset of fulminant infection.

Clinical and epidemiological aspects of invasive Streptococcus pyogenes infections in Denmark during 2003 and 2004

Active surveillance of invasive group A streptococcal (GAS) infections was conducted in Denmark during 2003 and 2004 as a part of the Strep-EURO initiative. The main objective was to improve understanding of the epidemiology of invasive GAS disease in Denmark. During the 2 years, 278 cases were reported, corresponding to a mean annual incidence of 2.6 cases per 100,000 inhabitants. The vast majority of isolates, 253 (91%), were from blood, with the remaining 25 (9%) being from cerebrospinal fluid, joints, or other normally sterile sites. The mean case fatality rate (CFR) was 20%, with the rate being higher in patients more than 70 years of age (36.5%). For streptococcal toxic shock syndrome (STSS) and necrotizing fasciitis the CFRs were 53% and 25%, respectively. Out of 16 T types recorded, three predominated: T28 (23%), T1 (22%), and the cluster T3/13/B3264 (14%). Among 29 different emm types, emm28 and emm1 accounted for 51% of strains, followed by emm3 (11%), emm89 (7%), and emm12 (5.5%). Low resistance rates were detected for macrolide-lincosamide-streptogramin B (MLS(B)) antibiotics (3%) and tetracycline (8%); two isolates exhibited coresistance to tetracycline and macrolides. Of nine pyrogenic exotoxin (superantigen) genes examined, speA and speC were identified in 58% and 40% of the strains, respectively; either of the genes was present in all strains causing STSS. Most strains harbored speG (99%). ssa was present in 14% of the isolates only. In Denmark, as in comparable countries, GAS invasive disease shows a sustained, high endemicity, with involvement of both established and emerging streptococcal emm and T types.

Molecular characterisation of invasive Streptococcus pyogenes isolates from Hungary obtained in 2004 and 2005

Our aim was to characterise by molecular techniques group A streptococci isolated from invasive infections in Hungary in 2004-2005. Twenty-six nonduplicate invasive GAS isolates were selected and examined. The mortality rate proved high (52.3%) for those cases (n = 21) where data were available. Predominant emm types were emm1 (n = 13, 50%) and emm80 (n = 5, 19.2%), but other M types (emm4, emm28, emm66, emm81.1, emm82, emm84) were also identified. Eight different PFGE types were distinguished, and each emm type showed an individual PFGE pattern. Our results show that--similarly to results obtained in several other countries--emm type 1 strains predominate among invasive GAS isolates, and that emm 1 type strains recovered from severe streptococcal infections were associated with the presence of the speA gene. The rate for macrolide resistance proved low: only two isolates showed elevated MICs for erythromycin.

emm Types, virulence factors, and antibiotic resistance of invasive Streptococcus pyogenes isolates from Italy: What has changed in 11 years?

To investigate the epidemiology and characteristics of invasive group A streptococcal (GAS) disease over 11 years in Italy, this study compared the emm types and the superantigen toxin genes speA and speC as well as the erythromycin, clindamycin, and tetracycline susceptibilities of 207 invasive GAS strains collected during two national enhanced surveillance periods (1994 to 1996 and 2003 to 2005) and the time between each set of surveillance periods. The present study demonstrated that emm1 strains were consistently responsible for about 20% of invasive GAS infections, while variations in the frequencies of the other types were noted, although the causes of most cases of invasive infections were restricted to emm1, emm3, emm4, emm6, emm12, and emm18. During the 1994 to 1996 surveillance period, an emm89 epidemic clone spread across the northern part of Italy. A restricted macrolide resistance phenotype-type distribution of the bacteriophage-encoded speA toxin as well as of macrolide resistance genes was noted over time. Indeed, the recent acquisition of macrolide resistance in previously susceptible emm types was observed.

Case of bacteraemic cellulitis by a non-haemolytic strain of Streptococcus pyogenes

Erysipelas and bacteraemia with what initially was diagnosed as a non-haemolytic streptococcus is reported. As neither colony morphology nor clinical picture was characteristic of non-haemolytic streptococci, the isolate was sent to a reference laboratory. 16S rRNA sequencing and phenotypic characterization identified the strain as a streptolysin S-deficient S. pyogenes..

emm typing of invasive T28 group A streptococci, 1995-2004, Finland

A total of 985 group A streptococcus (GAS) bacteraemia isolates collected in Finland during 1995-2004 were T-serotyped, and of these, 336 isolates of serotype T28 were subjected to further emm typing. The total number of isolates referred per year showed an increase within the study period, from 43 in 1995 to 130 in 2004. The annual incidence of invasive GAS (iGAS) bacteraemia showed a general increase during the study period, from 1.1 to 2.5 per 100 000 population. Serotype T28 remained among the most common serotypes, in addition to serotypes TB3264 and T1. The serotype T28 isolates were found to be distributed across six distinct emm types: emm28, emm77, emm53 (including subtypes 53.2 and 53.4), emm87, emm2 and emm4. The serotype distribution and the emm type distribution of serotype T28 fluctuated over time. Within the study period, the proportion of T28/emm28 isolates became the most prominent. During periods of low emm28 incidence, emm types 77 and 53 seemed to show a resurgence. emm typing revealed T28 isolates to be a genetically heterogeneous group harbouring a variety of distinct M proteins. This study confirms that T serotyping alone is not a sufficient method for epidemiological surveillance of iGAS.

Invasive group A streptococcal infection in injecting drug users and non-drug users in a single UK city

OBJECTIVES

Injecting drug users (IDU) represent an increasing proportion of patients with invasive group A streptococcal (GAS) disease. Our aims were to characterise the clinical presentation and strains causing GAS bacteremia in IDU from a single UK city (Brighton and Hove), and to compare this patient group with non-drug users (non-DU) with GAS bacteremia.

METHODS

Consecutive GAS blood culture isolates from twenty-two IDU and twenty-two non-DU presenting to the city hospital were studied. Clinical features, strain emm typing and superantigen toxin genotyping were investigated.

RESULTS

GAS invasive disease presented differently in IDU compared to non-DU with a predominance of injection site abscesses and lower mortality in IDU. GAS strains from IDU were predominantly emm82 and emm83 types, which are uncommon in the UK and emm82 strains appeared clonal. The non-DU GAS strains demonstrated a broader range of emm types including most frequently emm1 and emm89. There was no major difference in superantigen gene profile between the isolate groups.

CONCLUSION

The distinct presentation of invasive GAS disease in IDU compared with non-DU was associated with distinct emm types, a predominance of abscesses, and low mortality, although the small numbers preclude definitive conclusions. Further study is required to establish if these findings reflect strain differences or epidemiological differences in colonisation patterns and injecting practice.

Group A streptococci from invasive-disease episodes in Poland are remarkably divergent at the molecular level

Forty-one clinical isolates of group A streptococcus (GAS) were recovered in Poland from patients with severe invasive infections and were analyzed by phenotypic and genotypic techniques. All isolates were characterized by determining their susceptibilities to antimicrobial agents and by determining their types by pulsed-field gel electrophoresis, multilocus sequence typing, emm typing, and the detection of five streptococcal pyrogenic exotoxin genes (speA, speB, speC, speF, ssa). The isolates studied were fully susceptible to penicillin G, levofloxacin, quinupristin-dalfopristin, and linezolid. Resistance to tetracycline, chloramphenicol, and erythromycin was detected in 46.3, 12.1, and 9.8% of the isolates, respectively. A total of 23 different emm sequence types were identified, of which emm1 and emm12 (19.5% each) were the most common, followed by emm81, emm44/61, and emm85. All the emm1 isolates had the speA2 allele. Twenty-three unrelated sequence types (STs) were identified, with the most frequent STs, ST28 and ST36, corresponding to emm1 and emm12, respectively. Six newly found STs (STs 375, 376, 377, 378, 379, and 385) corresponded to emm types 74, 102, 77, 76, 84 and 63, respectively. The emm1 type and the presence of speA2 gene were associated with the severity of GAS infections. This work presents the first molecular study on Polish invasive GAS isolates.