Bacteraemia due to different groups of beta-haemolytic streptococci: a two-year survey and presentation of a case of recurring infection due to Streptococcus "equisimilis"

Comparison of Characteristics of Streptococcus dysgalactiae subsp. equisimilis Isolates Causing Repetitive vs Single Infections

No study has described Streptococcus dysgalactiae subsp. equisimilis (SDSE) isolates that cause repetitive infections (recurrence and reinfection). We compared the microbiological characteristics of SDSE causing repetitive infections with those causing single infections. Three patients with invasive infections were identified based on their medical records, and multiple SDSE isolates were collected at intervals over three weeks, using a laboratory repository. Isolates from 12 patients with single-episode infections served as controls. Six isolates were collected from three patients with first and second episodes of infection. All isolates causing either repetitive or single-episode infection were subjected to emm typing, multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), and random amplified polymorphic DNA (RAPD) analyses. Amplification of five virulence genes (sicG, prtF1, prtF2, lmb, and cbp), biofilm formation (BF), and cell invasion abilities (CIAs) were measured as virulent phenotypes. We observed close genetic similarities in the data obtained by emm typing, MLST, PFGE, and RAPD in four isolates from two patients, suggesting recurrence, whereas two isolates from one patient indicated genetic differences in these data, suggesting re-infection. The presence of the five virulence genes and the BF and CIA measurements appeared not to contribute to repetitive infections, compared with isolates causing single-episode infection. In conclusion, clinicians encountering patients with repetitive infections should be aware of both possibilities: recurrence with closely related strains and reinfection with different strains.

Delineation of Streptococcus dysgalactiae, its subspecies, and its clinical and phylogenetic relationship to Streptococcus pyogenes

The taxonomic status and structure of Streptococcus dysgalactiae have been the object of much confusion. Bacteria belonging to this species are usually referred to as Lancefield group C or group G streptococci in clinical settings in spite of the fact that these terms lack precision and prevent recognition of the exact clinical relevance of these bacteria. The purpose of this study was to develop an improved basis for delineation and identification of the individual species of the pyogenic group of streptococci in the clinical microbiology laboratory, with a special focus on S. dysgalactiae. We critically reexamined the genetic relationships of the species S. dysgalactiae, Streptococcus pyogenes, Streptococcus canis, and Streptococcus equi, which may share Lancefield group antigens, by phylogenetic reconstruction based on multilocus sequence analysis (MLSA) and 16S rRNA gene sequences and by emm typing combined with phenotypic characterization. Analysis of concatenated sequences of seven genes previously used for examination of viridans streptococci distinguished robust and coherent clusters. S. dysgalactiae consists of two separate clusters consistent with the two recognized subspecies dysgalactiae and equisimilis. Both taxa share alleles with S. pyogenes in several housekeeping genes, which invalidates identification based on single-locus sequencing. S. dysgalactiae, S. canis, and S. pyogenes constitute a closely related branch within the genus Streptococcus indicative of recent descent from a common ancestor, while S. equi is highly divergent from other species of the pyogenic group streptococci. The results provide an improved basis for identification of clinically important pyogenic group streptococci and explain the overlapping spectrum of infections caused by the species associated with humans.

Predictors of mortality in beta-hemolytic streptococcal bacteremia: a population-based study

OBJECTIVES

Several factors associated with mortality in Lancefield group A beta-hemolytic streptococcal bacteremia have been described in population-based surveillance studies, whereas such reports on group B, C, and G streptococcal are scant.

METHODS

In this population-based study all 314 episodes of beta-hemolytic streptococcal bacteremia in adult patients in the Pirkanmaa area, Finland, during the 10-year period 1995-2004 were retrospectively reviewed.

RESULTS

The 30-day case-fatality rate was 13%, being highest in group C (22%); in group A it was 15%, in group B 7%, and in group G 15%. Confusion, unconsciousness and dyspnea as the first sign or symptom were associated with increased case-fatality, while fever seemed to be a protecting factor for death. Alcoholism and ultimately or rapidly fatal underlying disease were significantly associated with increased case-fatality. Among infections of the skin and soft-tissues, necrotizing fasciitis had the highest risk of death (38%), while patients with cellulitis had a case-fatality of 8%. A history of previous cellulitis seemed to protect against death (case-fatality of 3% as compared to 16% among those without such a history (p=0.014)).

CONCLUSION

A history of previous cellulitis seemed to be a protecting factor against death. Fever was also associated with a good prognosis.

Group C streptococcal endocarditis

Group C streptococcus is found in many domestic animals and rarely causes infection in human beings. Severe infections caused by these bacteria are associated with high morbidity and mortality rates. We present a case of group C streptococcus endocarditis with sequelae, right-eye endophthalmitis, and multilobar pneumonia caused by septic embolization from the infected mitral valve.

Beta-hemolytic streptococcal bacteremia: a review of 241 cases

Bacteremia with beta-hemolytic Streptococci groups A, B, C and G has a mortality rate of approximately 20%. In this study we analyzed the association of various patient risk factors with mortality. Records from 241 patients with beta-hemolytic streptococcal bacteremia were reviewed with particular attention to which predisposing factors were predictors of death. A logistic regression model found age, burns, immunosuppressive treatment and iatrogenic procedures prior to the infection to be significant predictors of death, with odds ratios of 1.7 (per decade), 19.7, 3.6 and 6.8, respectively. In bacteremic patients with erysipelas, mortality increased from 8% to 50% when bullae were observed. No HIV-positive patients or IVDUs died as a result of their bacteremic episode. Surprisingly, we found 49% resistance to tetracycline.

Clinical presentation and outcome of bacteraemia caused by beta-haemolytic streptococci serogroup G

There has been a considerable increase in annual cases of bacteraemia caused by beta-haemolytic streptococci serogroup G (GGS) and we therefore undertook a retrospective case review in the Danish County of Northern Jutland. During a 19-year period (1981-1999) 94 cases were identified in a regional bacteraemia register, and the annual incidence rose from 3.0 per 106 inhabitants in 1981-1987 to 7.4 in 1988-1993 and 17.2 in 1994-1999. Clinical charts were available for 92 cases. The male/female ratio was 52/40 and the median age 71 years, range 15-97 years. Twenty-seven patients had reduced functional capacity. Fifty-two cases were community-acquired. The most common site of infection was the skin followed by the lungs and the urogenital tract. Eleven patients had no apparent site of infection. Underlying disease was present in 81 patients, who shared 149 co-morbid conditions, and the overall one-month case fatality rate was 23% (95% confidence limits 15-33%). We conclude that GGS are of increasing importance as a cause of bacteraemic infections and first and foremost affect patients who are aged, debilitated, or suffer from severe or multiple underlying diseases.

Analysis of a case of recurrent bacteraemia due to group A Streptococcus equisimilis by pulsed-field gel electrophoresis

An 86-year-old woman with a history of metastatic breast cancer developed two episodes of streptococcal bacteraemia and erysipelas separated by an interval of 3 months. The isolates belonged to Lancefield group A but were biochemically identified as Streptococcus equisimilis. The similarity of the two isolates was established by DNA macrorestriction analysis and pulsed-field gel electrophoresis, indicating that the second episode was due to relapse and not reinfection.