Streptococcal Toxic Shock Syndrome Caused by Streptococcus dysgalactiae subsp. equisimilis-related Empyema: A Novel Case Report

Streptococcal toxic shock syndrome (STSS) caused by Streptococcus dysgalactiae subsp. equisimilis (SDSE)-related empyema is rare but can result in shock vitals, acute kidney injury, and extensive erythema. In the present case, a 92-year-old woman with empyema caused by SDSE developed STSS after pleural drainage and antibiotic therapy. Despite temporary improvement with clindamycin and pleural drainage, the patient ultimately died due to malnutrition. Autopsy findings suggested that the infection was well controlled, but infections with Streptococcus spp., including SDSE, can trigger STSS in patients with empyema.

Incidence, seasonal pattern, and clinical manifestations of Streptococcus dysgalactiae subspecies equisimilis bacteremia; a population-based study

Streptococcus dysgalactiae subspecies equisimilis (SDSE) is a human pathogen causing severe invasive infections. Population-based studies on SDSE bacteremia are limited. The purpose of this study was to investigate the incidence, seasonal pattern, clinical manifestations, and recurrence of SDSE bacteraemia. Records regarding patients aged ≥ 18 years with SDSE bacteremia in the Pirkanmaa health district in August 2015 to July 2018 were retrospectively reviewed. A total of 230 SDSE bacteremia episodes were identified, with 217 episodes (involving 211 patients) available for analysis. The mean annual incidence rate of SDSE bacteremia was 16.9/100 000 inhabitants. Most episodes (33%) were detected in the summer (June to August) (p = 0.058). Episodes with bacteremic cellulitis were statistically significantly more common during the summer compared with other seasons (p = 0.008). Cellulitis was the most common presenting clinical manifestation of SDSE bacteremia (68% of all episodes). Risk factors of recurring bacteremia were chronic eczema and/or skin erosion (OR 3.96 [95% CI 1.11-14.1]), heart disease (OR 3.56 [95% CI 1.22-10.4]), diabetes (OR 3.77 [95% CI 1.35-10.5]) and a history of cellulitis. We found a remarkably high incidence of SDSE bacteraemia in the Pirkanmaa health district. Bacteraemic cellulitis, which was the predominant clinical manifestation is more often occurred in the summer. Risk factors of recurring SDSE bacteremia were a history of cellulitis, chronic eczema or skin erosion, diabetes, and heart disease.

Clonal Expansion of Multidrug-Resistant Streptococcus dysgalactiae Subspecies equisimilis Causing Bacteremia, Japan, 2005-2021

Incidence of Streptococcus dysgalactiae subspecies equisimilis (SDSE) bacteremia is increasing in the Kyoto-Shiga region of Japan. We retrospectively analyzed clinical features of SDSE bacteremia and conducted comparative genomic analyses of isolates collected from 146 bacteremia episodes among 133 patients during 2005-2021. Of those patients, 7.7% required vasopressor support, and 7.0% died while in the hospital. The prevalence of isolates resistant to erythromycin, minocycline, and clindamycin increased from 8.6% during 2005-2017 to 21.6% during 2018-2021. Our genomic analysis demonstrated that sequence type 525 and clonal complex 25 were predominant in SDSE isolates collected during 2018-2021. In addition, those isolates had acquired 2 antimicrobial-resistance genes, ermB and tetM, via Tn916-like integrative and conjugative elements (ICEs). Phylogenetic analysis revealed clonal distribution of Tn916-like ICEs in SDSE isolates. Our findings suggest that Tn916-like ICEs contributed to the emergence and recent increase of multidrug-resistant SDSE bacteremia in this region of Japan.

Major risk factors for Streptococcus dysgalactiae subsp. equisimilis bacteremia: a population-based study

BACKGROUND

Streptococcus dysgalactiae subspecies equisimilis is a human pathogen causing severe invasive infections. Detailed information on S. dysgalactiae subsp. equisimilis bacteremia and especially of predisposing factors are lacking. The purpose of the study is to investigate the risk factors of S. dysgalactiae subsp. equisimilis bacteremia compared to the general population in Finland.

METHODS

We retrospectively reviewed all patients older than 18 years with S. dysgalactiae subsp. equisimilis bacteremia in the Pirkanmaa health district from August 2015 to July 2018. The risk factors for S. dysgalactiae subsp. equisimilis bacteremia were investigated with respect to the normal population in Finland using the Finhealth study data provided by the Finnish institute for health and welfare. The study group was matched with the Finhealth study by age and sex.

RESULTS

Altogether 230 cases of S. dysgalactiae subsp. equisimilis bacteremia were detected. The medical records of 217 episodes of S. dysgalactiae subsp. equisimilis bacteremia (involving 211 patients) were available for analysis. Obesity was a statistically significant risk factor for S. dysgalactiae subsp. equisimilis bacteremia (Odds Ratio 2.96 [95% CI 2.22-3.96]). Diabetes and coronary artery disease were also associated with an increased risk of S. dysgalactiae subsp. equisimilis bacteremia (OR 4.82 [95% CI 3.62-6.42]) and (OR 3.03 [95% CI 2.18-4.19]).

CONCLUSIONS

We found obesity, diabetes, and coronary artery disease to be associated with an increased risk for S. dysgalactiae subsp. equisimilis bacteremia. These results provide an increased understanding of risk factors for S. dysgalactiae subsp. equisimilis bacteremia.

Pyogenic spondylitis caused by Streptococcus dysgalactiae subspecies equisimilis in a patient with nasopharyngeal cancer

In the treatment of head and neck cancer, radiation therapy is an effective modality and is often used in routine clinical practice. Although rare, pyogenic spondylitis has been reported as a complication of radiation therapy. Here, we report a case of nasopharyngeal carcinoma resulting in pyogenic spondylitis from a catheter-related bloodstream infection after chemoradiotherapy. The initial symptoms were fever and posterior cervical pain. Streptococcus dysgalactiae subspecies equisimilis was detected in blood cultures. Magnetic resonance imaging showed abnormal enhancement of the C6 and C7 vertebrae and an anterior epidural abscess. The infection was successfully treated with antibacterial therapy.

Erythematous rash and postinfectious acral desquamation due to Streptococcus dysgalactiae subspecies equisimilis infection in a child

Streptococcus dysgalactiae subspecies equisimilis infection is an emerging pathogen. Cutaneous and systemic manifestations resemble those of other pyogenic streptococci. However, the rapid group A antigen detection test used to diagnose Streptococcus pyogenes infection is usually negative, making the diagnosis difficult. If clinical suspicion of streptococcal infection is high, a tonsillar culture should be performed to confirm the diagnosis.

High prevalence of pharyngeal bacterial pathogens among healthy adolescents and young adults

The pharyngeal mucosa can be colonized with bacteria that have potential to cause pharyngotonsillitis. By the use of culturing techniques and PCR, we aimed to assess the prevalence of bacterial pharyngeal pathogens among healthy adolescents and young adults. We performed a cross-sectional study in a community-based cohort of 217 healthy individuals between 16 and 25 years of age. Samples were analyzed for Group A streptococci (GAS), Group C/G streptococci (SDSE), Fusobacterium necrophorum, and Arcanobacterium haemolyticum. Compared to culturing, the PCR method resulted in more frequent detection, albeit in most cases with low levels of DNA, of GAS (20/217 vs. 5/217; p < 0.01) and F. necrophorum (20/217 vs. 8/217; p < 0.01). Culturing and PCR yielded similar rates of SDSE detection (14/217 vs. 12/217; p = 0.73). Arcanobacterium haemolyticum was rarely detected (3/217), and only by PCR. Overall, in 25.3% (55/217) of these healthy adolescents and young adults at least one of these pathogens was detected, a rate that is higher than previously described. Further studies are needed before clinical adoption of PCR-based detection methods for pharyngeal bacterial pathogens, as our findings suggest a high incidence of asymptomatic carriage among adolescents and young adults without throat infections.

Invasive infection due to Streptococcus dysgalactiae subspecies equisimilis causing endocarditis and ventriculitis: A case report

We aim to raise awareness of the role of Streptococcus dysgalactiae subsp. equisimilis (SDSE) in causing endovascular and central nervous system infections, and to promote recognition of SDSE as a pathogen that may cause serious invasive infections.

Association between bacterial finding, antibiotic treatment and clinical course in patients with pharyngotonsillitis: a registry-based study in primary healthcare in Sweden

Background

The role of non-group A streptococci and Fusobacterium necrophorum in pharyngotonsillitis has been disputed and few prospective studies have evaluated the effect of antibiotic treatment. This study uses registry data to investigate the relation between antibiotic prescription for pharyngotonsillitis in primary healthcare and return visits for pharyngotonsillitis, complications, and tonsillectomy.

Methods

Retrospective data were extracted from the regional electronic medical record system in Kronoberg County, Sweden, for all patients diagnosed with pharyngotonsillitis between 2012 and 2016. From these data, two cohorts were formed: one based on rapid antigen detection tests (RADT) for group A streptococci (GAS) and one based on routine throat cultures for β-haemolytic streptococci and F. necrophorum. The 90 days following the inclusion visit were assessed for new visits for pharyngotonsillitis, complications, and tonsillectomy, and related to bacterial aetiology and antibiotic prescriptions given at inclusion.

Results

In the RADT cohort (n = 13,781), antibiotic prescription for patients with a positive RADT for GAS was associated with fewer return visits for pharyngotonsillitis within 30 days compared with no prescription (8.7% vs. 12%; p = 0.02), but not with the complication rate within 30 days (1.5% vs. 1.8%; p = 0.7) or with the tonsillectomy rate within 90 days (0.27% vs. 0.26%; p = 1). In contrast, antibiotic prescription for patients with a negative RADT was associated with more return visits for pharyngotonsillitis within 30 days (9.7% vs. 7.0%; p = 0.01). In the culture cohort (n = 1 370), antibiotic prescription for patients with Streptococcus dysgalactiae ssp. equisimilis was associated with fewer return visits for pharyngotonsillitis within 30 days compared with no prescription (15% vs. 29%; p = 0.03).

Conclusions

Antibiotic prescription was associated with fewer return visits for pharyngotonsillitis in patients with a positive RADT for GAS but with more return visits in patients with a negative RADT for GAS. There were no differences in purulent complications related to antibiotic prescription.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06511-y.

In-hospital mortality among patients with invasive non-group A β-hemolytic Streptococcus treated with clindamycin combination therapy: a nationwide cohort study

Aim

Combination treatment with clindamycin is recommended in patients with invasive group A Streptococcus infection; however, whether the same treatment is effective in invasive group B Streptococcus and S. dysgalactiae subspecies equisimilis infections remains unknown. We aimed to investigate whether clindamycin added to standard of care therapy would be effective in patients with invasive non-group A β-hemolytic Streptococcus infections.

Methods

This was a nationwide retrospective cohort study using the Japanese Diagnosis Procedure Combination inpatient database focusing on the period between 2010 and 2018. We extracted data on patients diagnosed with sepsis due to non-group A β-hemolytic Streptococcus. One-to-four propensity score-matching was undertaken to compare patients who were treated with clindamycin within 2 days of admission (clindamycin group) and those who did not (control group). The primary outcome was in-hospital mortality.

Results

We identified 3754 eligible patients during the study period. The patients were divided into the clindamycin (n = 296) and control groups (n = 3458). After one-to-four propensity score matching, we compared 289 and 1156 patients with and without clindamycin, respectively. In-hospital mortality did not significantly differ between the two groups (9.7% versus 10.3%; risk difference 0.3%; 95% confidence interval, -3.5% to 4.2%).

Conclusions

This nationwide database study showed that combination therapy involving the use of clindamycin was not associated with lower in-hospital mortality in patients with invasive non-group A β-hemolytic Streptococcus.

Beta-Haemolytic Group A, C and G Streptococcal Infections in Southern Hungary: A 10-Year Population-Based Retrospective Survey (2008-2017) and a Review of the Literature

Introduction

Pyogenic β-hemolytic streptococci (including Group A, C and G Streptococcus) are some of the most important Gram-positive bacterial pathogens in human medicine. Although effective therapy is available, invasive streptococcal infections are associated with a significant disease burden.

Methods

In this retrospective study, the epidemiological characteristics of invasive Group A (iGAS) and Group C and G (iGCGS) streptococci, along with tonsillo-pharyngitis-causing pGAS and pGCGS infections, were assessed in Southern Hungary. A total of 1554 cases of streptococcal tonsillo-pharyngitis infections (26.5–44.1/100,000 persons, pGAS: 95.5%; n=1484) and 1104 cases of invasive streptococcal infections were detected (12.5–31.4/100,000 persons, iGAS: 77.9%; n=861).

Results

The average age of the affected patients in the various groups were the following: pGAS: 13.2±13.1 years, pGCGS: 21.0±15.0 years (p=0.039), iGAS: 49.1±12.8 years, iGCGS: 58.7±18.5 years (p>0.05). iGAS isolates originated from abscesses (47.1%), blood culture samples (24.1%), surgical samples (16.7%), biopsies (4.6%), pleural fluid (3.5%), pus (2.0%), synovial fluid (1.3%) and cerebrospinal fluid samples (0.7%). In contrast, iGCGS isolates mainly originated from blood culture samples (53.8%), abscesses (22.9%), surgical samples (12.3%), synovial fluid (5.1%), pleural fluid (3.7%), pus (1.8%) and cerebrospinal fluid samples (0.4%). All respective isolates were susceptible to benzyl-penicillin; overall resistance levels for erythromycin (10.5% for GAS, 21.4% for GCGS) and clindamycin (9.2% for GAS, 17.2% for GCGS) were significantly higher in GCGS isolates, while resistance levels for norfloxacin were higher in GAS isolates (13.5% for GAS, 6.9% for GCGS).

Conclusion

The rates of resistance to macrolides and clindamycin are a cause for concern (especially among GCGS isolates); however, resistance levels are still relatively low, compared to Southern European countries.

Molecular subtyping and antimicrobial susceptibility of Streptococcus dysgalactiae subspecies equisimilis isolates from clinically diseased pigs

Background

Streptococcus dysgalactiae subspecies equisimilis (SDSE) acts as an etiological agent for lameness, neurological signs, and high mortality in pigs. Despite its importance in pig industries and zoonotic potential, little is known about the effects of this pathogen.

Objectives

This study aimed to determine the molecular characteristics and antimicrobial resistance of SDSE strains isolated from diseased pigs.

Methods

A total 11 SDSE isolates were obtained from diseased pigs. Bacterial identification, PCR for virulence genes, emm typing, and antimicrobial resistance genes, multilocus sequence typing, and antimicrobial susceptibility test were performed.

Results

Nine isolates were from piglets, and 8 showed lameness, sudden death, or neurological signs. The isolates were PCR-positive for sla (100%), sagA (100%), and scpA (45.5%), and only 1 isolate amplified the emm gene (stL2764). Eight different sequence types were detected, categorized into 2 clonal complexes and 4 singletons. All the isolates in this study were included in a small cluster, which also contained other strains derived from humans and horses. The minimum inhibitory concentrations for the tested beta-lactams were low, while those for macrolides, tetracyclines, and fluoroquinolones were relatively high. PCR analysis of the macrolide and tetracycline resistance genes demonstrated that the isolates carried erm(B) (18.2%, n = 2), mef(A/E) (9.1%, n = 1), tet(M) (18.2%, n = 2), and tet(O) (90.2%, n = 10). Two isolates presented a mutation in parC, which is associated with fluoroquinolone resistance.

Conclusion

This study provided insight into swine-derived SDSE, as it is related to veterinary medicine, and elucidated its zoonotic potential, in the context of molecular epidemiology and antimicrobial resistance in public health.

Anti-streptococcal antibody and T-cell interactions with vascular endothelial cells initiate the development of rheumatic carditis

The role of group A streptococcal and Streptococcus dysgalactiae subspecies equisimilis M-protein specific Abs and T-cells in endothelial cell activation was investigated using cultured rat aortic endothelial cells, and in a rat model of autoimmune valvulitis. Heat inactivated serum and mononuclear cells from streptococcal M-protein immunized rats independently induced upregulation of the endothelial cell adhesion molecules, vascular cell adhesion molecule (VCAM)-1 and intercellular adhesion molecule (ICAM)-1 in cultured cells. We also observed T-cell migration across endothelial cell monolayers incubated with serum from M-protein-immunized rats. Furthermore, we observed VCAM-1 and ICAM-1 expression in the myocardium of rats injected with M-protein compared to control animals. These observations support the contention that initial interactions between streptococcal M-protein specific Abs and/or T-cells with the heart endothelium lead to endothelial cell activation followed by transmigration of M-protein specific T-cells into heart tissue leading to an inflammatory process that leads to carditis in rheumatic fever and rheumatic heart disease.

Immunoglobulin Attenuates Streptokinase-Mediated Virulence in Streptococcus dysgalactiae Subspecies equisimilis Necrotizing Fasciitis

Background

Necrotizing fasciitis (NF) retains a very high mortality rate despite prompt and adequate antibiotic treatment and surgical debridement. Necrotizing fasciitis has recently been associated withStreptococcus dysgalactiae subspeciesequisimilis (SDSE).

Methods

We investigated the causes of a very severe clinical manifestation of SDSE-NF by assessing both host and pathogen factors.

Results

We found a lack of streptokinase-function blocking antibodies in the patient resulting in increased streptokinase-mediated fibrinolysis and bacterial spread. At the same time, the clinical SDSE isolate produced very high levels of streptokinase. Exogenous immunoglobulin Gs (ex-IgGs) efficiently blocked streptokinase-mediated fibrinolysis in vitro, indicating a protective role against the action of streptokinase. In vivo, SDSE infection severity was also attenuated by ex-IgGs in a NF mouse model.

Conclusions

These findings illustrate for the first time that the lack of specific antibodies against streptococcal virulence factors, such as streptokinase, may contribute to NF disease severity. This can be counteracted by ex-IgGs.

Pathologic and molecular characterization of Streptococcus dysgalactiae subsp. equisimilis infection in neonatal piglets

Streptococcus dysgalactiae subspecies equisimilis (SDSE) is an emerging pathogen in animals and humans. Herein, we describe two clinical swine cases of SDSE infection presenting with lameness, neurological signs, or sudden death. Pathological examination indicated suppurative arthritis, encephalitis, and multifocal abscesses in kidney and heart. The β-hemolytic colonies obtained from joint samples of each case were identified as SDSE. The two isolates had low minimum inhibitory concentrations for β-lactams, and they presented the same virulence gene profile (slo⁻/sagA⁺/pSTKP8⁺). Molecular analysis by multilocus sequence typing identified the SDSE isolates from cases 1 and 2 as sequence types 315 and 252, respectively.

Molecular characterization and antibiotic resistance of Streptococcus dysgalactiae subspecies equisimilis isolated from patients with streptococcal toxic shock syndrome

Streptococcal toxic shock syndrome (STSS) is a severe invasive infection characterized by the sudden onset of shock, multiorgan failure, and high mortality. Although STSS is mainly caused by Streptococcus pyogenes, group G streptococcus identified as S. dysgalactiae subsp. equisimilis (SDSE) causing STSS has also been reported; however, no study has analyzed >100 isolates of SDSE causing STSS. Therefore, we characterized the emm genotype of 173 SDSE isolates obtained from STSS patients in Japan during 2014-2016 and performed antimicrobial susceptibility testing using the broth microdilution method and emm gene typing. The predominant emm genotype was found to be stG6792, followed by stG485, stG245, stG10, stG6, and stG2078. These six genotypes constituted more than 75% of the STSS isolates. The proportion of each emm genotype in STSS isolates correlated with that in invasive isolates previously reported. We found that 16.2% of the isolates showed clindamycin resistance. The proportion of clindamycin-resistant SDSE isolates was significantly higher than that of S. pyogenes isolates. Thus, while treating STSS caused by SDSE, it is necessary to consider the possibility of clindamycin resistance and to ensure judicious use of the drug.

Biofilm formation of beta-hemolytic group G Streptococcus dysgalactiae subspecies equisimilis isolates and its association with emm polymorphism

Biofilm formation has been well known as a determinant of bacterial virulence. Group G Streptococcus dysgalactiae subspecies equisimilis (SDSE), a relevant pathogen with increasing medical importance, was evaluated for the biofilm-forming potential. Microtiter plate assay was used to assess the most feasible medium for group G SDSE to form a biofilm. Among 246 SDSE isolates examined, 46.7%, 43.5%, 33.3%, and 26.4% of isolates showed moderate or strong biofilm-forming abilities using tryptic soy broth (TSB), brain heart infusion broth (BHI), Todd-Hewitt broth (THB), and C medium with 30 mM glucose (CMG), respectively. The addition of glucose significantly increased the biofilm-forming ability of group G SDSE. FCT (fibronectin-collagen-T-antigen) typing of SDSE was first undertaken and 11 FCT types were found. Positive associations of stG10.0 or negative associations of stG245.0, stG840.0, and stG6.1 with biofilm-forming ability of SDSE were, respectively, found. This was the first investigation demonstrating biofilm-forming potential in clinical group G SDSE isolates; also, some significant associations of biofilm-forming ability with certain emm types were presented.

Streptococcal toxic-shock syndrome due to Streptococcus dysgalactiae subspecies equisimilis in breast cancer-related lymphedema: a case report

BACKGROUND

Breast cancer-related lymphedema often causes cellulitis and is one of the most common complications after breast cancer surgery. Streptococci are the major pathogens underlying such cellulitis. Among the streptococci, the importance of the Lancefield groups C and G is underappreciated; most cases involve Streptococcus dysgalactiae subspecies equisimilis. Despite having a relatively weak toxicity compared with group A streptococci, Streptococcus dysgalactiae subspecies equisimilis is associated with a mortality rate that is as high as that of group A streptococci in cases of invasive infection because Streptococcus dysgalactiae subspecies equisimilis mainly affects elderly individuals who already have various comorbidities.

CASE PRESENTATION

An 83-year-old Japanese woman with breast cancer-related lymphedema in her left upper limb was referred to our hospital with high fever and acute pain with erythema in her left arm. She showed septic shock with disseminated intravascular coagulation. Blood culture showed positive results for Streptococcus dysgalactiae subspecies equisimilis, confirming a diagnosis of streptococcal toxic-shock syndrome. She survived after successful intensive care.

CONCLUSIONS

To the best of our knowledge, this case represents the first report of Streptococcus dysgalactiae subspecies equisimilis-induced streptococcal toxic-shock syndrome in a patient with breast cancer-related lymphedema. Breast cancer-related lymphedema is a common problem, and we must pay attention to invasive streptococcal soft tissue infections, particularly in elderly patients with chronic disease.

Beta-haemolytic group A, C and G streptococcal infections in Western Norway: a 15-year retrospective survey

Pyogenic streptococci cause significant morbidity and mortality, and the incidence of invasive group C and G streptococcal disease appears to be increasing. In this retrospective study we describe the epidemiological characteristics of invasive group A, C and G, along with non-invasive group C and G streptococcal infections in Western Norway from 1999 to 2013. A total of 512 invasive streptococcal infections were identified, of these 297 (58%) were group A (GAS), 24 (5%) group C (GCS) and 188 (37%) group G streptococci (GGS). In the non-invasive group, 4935 GCS and GGS-infections were identified. GCS and GGS were treated as one group (GCGS) for statistical purposes. All microbial categories displayed increasing incidence with age, seasonal variation and a male predominance. The incidence of invasive GCGS infections increased significantly from 1.4/100,000 inhabitants in 1999 to 6.3/100,000 in 2013 (p <0.001). Conversely, the annual rates of invasive GAS infection exhibited marked fluctuations, ranging from 2.7/100,000 (2000) to 8.3/100,000 (1999), but no significant temporal trends were observed. The incidence of non-invasive GCGS infections decreased significantly during the study period (p <0.001). The most frequently encountered emm-types among the 209 iGAS-isolates analysed were emm1 (24%), emm3 (14%) and emm28 (14%); whereas stG643 (19%), stG485 (15%) and stG6 (13%) were most prevalent among the 122 iGCGS-isolates available for typing. The increasing burden of invasive β-haemolytic streptococcal disease in our community calls for sustained attentiveness to the clinical and molecular aspects of GAS, GCS and GGS infections.

Distribution of virulence factors and association with emm polymorphism or isolation site among beta-hemolytic group G Streptococcus dysgalactiae subspecies equisimilis

Distribution of virulence factors and association with emm polymorphism or isolation site among beta-hemolytic group G Streptococcus dysgalactiae subspecies equisimilis. Streptococcus dysgalactiae subspecies equisimilis (SDSE), the dominant human pathogenic species among group G streptococci, is the causative agent of several invasive and non-invasive diseases worldwide. However, limited information is available about the distribution of virulence factors among SDSE isolates, or their association with emm types and the isolation sites. In this study, 246 beta-hemolytic group G SDSE isolates collected in central Taiwan between February 2007 and August 2011 were under investigation. Of these, 66 isolates were obtained from normally sterile sites and 180 from non-sterile sites. emm typing revealed 32 types, with the most prevalent one being stG10.0 (39.8%), followed by stG245.0 (15.4%), stG840.0 (12.2%), stG6.1 (7.7%), and stG652.0 (4.1%). The virulence genes lmb (encoding laminin-binding protein), gapC (glyceraldehyde 3-phosphate dehydrogenase), sagA (streptolysin S), and hylB (hyaluronidase) existed in all isolates. Also, 99.2% of the isolates possessed slo (streptolysin O) and scpA (C5a peptidase) genes. In addition, 72.8%, 14.6%, 9.4%, and 2.4% of the isolates possessed the genes ska (streptokinase), cbp (putative collagen-binding protein, SDEG_1781), fbp (putative fibronectin-binding protein, SDEG_0161), and sicG (streptococcal inhibitor of complement), respectively. The only superantigen gene detected was spegg (streptococcus pyrogenic exotoxin G(dys) ), which was possessed by 74.4% of the isolates; these isolates correlated with non-sterile sites. Positive correlations were observed between the following emm types and virulence genes: stG10.0 and stG840.0 with spegg, stG6.1 and stG652.0 with ska, and stG840.0 with cbp. On the other hand, negative correlations were observed between the following: stG245.0, stG6.1, and stG652.0 types with spegg, stG10.0 with ska, and stG10.0, stG245.0, and stG6.1 types with cbp. The prevalence of emm types of SDSE in central Taiwan was investigated for the first time. Moreover, the distribution of virulence factors among beta-hemolytic group G SDSE isolates, as well as their association with emm types or isolation sites were also examined.

Antibiotic susceptibility pattern and erythromycin resistance mechanisms in beta-hemolytic group G Streptococcus dysgalactiae subspecies equisimilis isolates from central Taiwan

BACKGROUND/PURPOSE

Information concerning antibiotics susceptibilities of beta-hemolytic group G Streptococcus dysgalactiae subspecies equisimilis (SDSE) clinical isolates in central Taiwan was limited.

METHODS

Totally, 246 SDSE isolates were collected from mainly five regional hospitals, from February 2007 to August 2011. Disk diffusion method, broth microdilution method, and clindamycin induction test (D test) were respectively performed according to the guidelines of the Clinical and Laboratory Standards Institute. Polymerase chain reaction was used to detect the corresponding erythromycin resistance genes.

RESULTS

All isolates were susceptible to penicillin, cefotaxime, and vancomycin. The rate of erythromycin resistance was 24.0% (59/246), whereas that of clindamycin resistance was 12.2% (30/246). The resistance rates of isolates from different hospitals varied from 15.0% to 45.5% for erythromycin and from 7.1% to 36.4% for clindamycin. For erythromycin-resistant SDSE isolates, three different phenotypes with resistance to macrolides (M), lincosamides (L), and type B streptogramins (SB) were observed: M (49.2%), constitutive MLSB (cMLSB, 35.6%), and inducible MLSB (iMLSB, 15.3%). All M phenotypic isolates carried mefA. The most prevalent genotypes among cMLSB and iMLSB phenotypic isolates were ermB, followed by ermTR. One isolate with cMLSB phenotype carried both ermB and ermTR, whereas one isolate with iMLSB phenotype carried both ermB and ermC.

CONCLUSION

This is the first trial investigating the antimicrobial susceptibility pattern and erythromycin resistance mechanisms of beta-hemolytic group G SDSE isolates in central Taiwan. The resistance rates for both erythromycin and clindamycin varied significantly among hospitals located in this area and should be monitored continuously in the future.