Severe group A streptococcal infections associated with a toxic shock-like syndrome and scarlet fever toxin A

Invasive group A streptococcal infections in Ontario, Canada. Ontario Group A Streptococcal Study Group

BACKGROUND

Several reports suggest that the incidence of invasive group A streptococcal infections, including streptococcal toxic shock syndrome and necrotizing fasciitis, is increasing.

METHODS

During 1992 and 1993 we conducted prospective, population-based surveillance of invasive group A streptococcal disease in Ontario, Canada. We reviewed clinical and laboratory records, searched for secondary cases of invasive disease, and cultured specimens from household contacts.

RESULTS

We identified 323 patients with invasive group A streptococcal infections, for an annual incidence of 1.5 cases per 100,000 population. The rates were highest in young children and the elderly. Fifty-six percent of the patients had underlying chronic illness. Risk factors for disease included infection with the human immunodeficiency virus, cancer, diabetes, alcohol abuse, and chickenpox. The most common clinical presentations were soft-tissue infection (48 percent), bacteremia with no septic focus (14 percent), and pneumonia (11 percent). Necrotizing fasciitis occurred in 6 percent of patients, and toxic shock in 13 percent. The mortality rate was 15 percent overall, but it was 29 percent among those over 64 years of age (P<0.001) and 81 percent among those with toxic shock (P<0.001). Fourteen percent of the cases were nosocomial, and 4 percent occurred in nursing home residents, often in association with disease outbreaks. Invasive disease occurred in 2 household contacts of patients with infection, for an estimated risk of 3.2 per 1000 household contacts (95 percent confidence interval, 0.39 to 12 per 1000).

CONCLUSIONS

The elderly and those with underlying medical conditions are at greatest risk for invasive group A streptococcal disease, toxic shock, and necrotizing fasciitis. Invasive steptococcal infection is associated with a substantial risk of transmission in households and health care institutions.

Streptococcal erythrogenic toxins induce neopterin formation in human peripheral blood mononuclear cells but not in the human myelomonocytoma cell line THP-1

We tested whether the exposure of human monocytic cells to streptococcal erythrogenic toxins A, B, C and a streptococcal-derived Mitogert BX is associated with synthesis of neopterin in vitro. Neopterin production was not induced when the human myelomono-cytoma cell line THP-1 was stimulated with these toxins, and there was only a slight co-stimulatory effect of streptococcal erythrogenic toxin A together with interferon-gamma stimulation. However, these toxins induced interferon-gamma and further neopterin production in peripheral blood mononuclear cells of three healthy individuals. This neopterin formation could be blocked by anti-human interferon-gamma. From our investigations we conclude that there is no direct effect of streptococcal erythrogenic toxins on neopterin production by monocytic cells. However, the data obtained in peripheral blood mononuclear cell culture imply that these toxins are able to stimulate neopterin production in humans via the induction of huge amounts of interferon-gamma.

Necrotizing fasciitis

Necrotizing fasciitis is an uncommon soft-tissue infection, usually caused by toxin-producing, virulent bacteria, which is characterized by widespread fascial necrosis with relative sparing of skin and underlying muscle. It is accompanied by local pain, fever, and systemic toxicity and is often fatal unless promptly recognized and aggressively treated. The disease occurs more frequently in diabetics, alcoholics, immunosuppressed patients, i.v. drug users, and patients with peripheral vascular disease, although it also occurs in young, previously healthy individuals. Although it can occur in any region of the body, the abdominal wall, perineum, and extremities are the most common sites of infection. Introduction of the pathogen into the subcutaneous space occurs via disruption of the overlying skin or by hematogenous spread from a distant site of infection. Polymicrobial necrotizing fasciitis is usually caused by enteric pathogens, whereas monomicrobial necrotizing fasciitis is usually due to skin flora. Tissue damage and systemic toxicity are believed to result from the release of endogenous cytokines and bacterial toxins. Due to the paucity of skin findings early in the disease, diagnosis is often extremely difficult and relies on a high index of suspicion. Definitive diagnosis is made at surgery by demonstration of a lack of resistance of normally adherent fascia to blunt dissection. Treatment modalities include surgery, antibiotics, supportive care, and hyperbaric oxygen. Early and adequate surgical debridement and fasciotomy have been associated with improved survival. Initial antibiotic therapy should include broad aerobic and anaerobic coverage. If available, hyperbaric oxygen therapy should be considered, although to our knowledge, there are no prospective, randomized clinical trials to support this. Mortality rates are as high as 76%. Delays in diagnosis and/or treatment correlate with poor outcome, with the cause of death being overwhelming sepsis syndrome and/or multiple organ system failure.

Orthopaedic manifestations of invasive group A streptococcal infections complicating primary varicella

The incidence of invasive group A streptococcal (GAS) infections in primary varicella appears to be increasing. GAS infections complicating varicella range from cellulitis, abscess, and septic arthritis to life-threatening necrotizing fasciitis and pyomyositis in association with GAS toxic shock syndrome (TSS). Four patients admitted in 1 year to the Children's Hospital and Medical Center in Seattle, whose care included evaluation and treatment by the Orthopaedic service, are presented to illustrate this spectrum. Three had a delay in diagnosis, including discharge from previous emergency department visits. One patient with polyarticular septic arthritis was treated with diagnostic aspiration and intravenous antibiotics. The remainder required urgent surgical debridement for treatment of deep infection. Patients with necrotizing fasciitis or pyomyositis had life-threatening complications of TSS, including hypotension, adult respiratory distress syndrome (ARDS), coagulopathy, and acute renal failure. These patients required aggressive fluid resuscitation and prolonged intensive care unit support. Diagnostic imaging studies were obtained in one patient with necrotizing pyomyositis but may have served only to delay definitive treatment. Recognition of the potential for secondary GAS infections and a high index of suspicion for the presence of necrotizing soft-tissue infection are essential in the evaluation of any child with fever and localized extremity pain with varicella.

Recombinant, octavalent group A streptococcal M protein vaccine

One of the major obstacles to the development of group A streptococcal M protein vaccines is the multiplicity of M serotypes expressed by these organisms. In this study, we have constructed a recombinant, hybrid M protein that contains type-specific aminoterminal fragments of eight different M proteins. We show that the purified hybrid recombinant protein is immunogenic in rabbits and evokes antibodies that react with native M proteins from the respective streptococcal serotypes. In addition, the immune sera evoked by the octavalent protein opsonized six of the eight serotypes of streptococci, indicating that the majority of the M protein fragments contained protective epitopes that retained their native conformations in the hybrid protein. None of the antisera raised against the octavalent protein crossreacted with human heart tissue. These studies indicate that multivalent, hybrid M proteins may be used to elicit broadly protective immune responses against multiple serotypes of group A streptococci.

Acute ventilatory failure in Lambert-Eaton myasthenic syndrome and its response to 3,4-diaminopyridine

Respiratory failure is a common manifestation of myasthenia gravis but is infrequent in Lambert-Eaton myasthenic syndrome (LEMS), where it is often related to the use of paralytic agents or intercurrent pulmonary pathology. Therapies that are effective acutely in myasthenia gravis are usually of minimal benefit in LEMS. We describe a patient with respiratory failure secondary to LEMS who responded to 3,4-diaminopyridine and review the 12 previously reported cases of ventilatory failure in LEMS.

Phylogenetic distribution of streptococcal superantigen SSA allelic variants provides evidence for horizontal transfer of ssa within Streptococcus pyogenes

Phylogenetic analyses recently found the gene encoding the streptococcal superantigen SSA of Streptococcus pyogenes to occur in several well-differentiated clones comprising 10 (12.5%) of 80 clonal lineages examined. To determine if distinct clonal lineages carried the same ssa coding sequence or harbored a group of allelic variants, ssa was sequenced from 23 S. pyogenes strains representing the 10 clones identified by multilocus enzyme electrophoresis. Three alleles of ssa were found in natural populations of S. pyogenes. ssa-1 and ssa-3 differed by a single synonymous substitution in codon 94; both encoded SSA-1. Each of these alleles was present in phylogenetically diverse clones that had not shared a recent common ancestor. ssa-2 was present in a single clonal lineage. It was identical to ssa-3 at codon 94 but had a nonsynonymous substitution at codon 28 that changed the second amino acid of the mature protein from serine to arginine. This substitution altered the predicted isoelectric point and affected the apparent molecular mass during sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Despite sequence variation both upstream of and within the ssa locus, all ssa-positive lineages expressed either SSA-1 or SSA-2. The observed patterns of ssa allele-clone distribution provide evidence for individual incidences of horizontal transfer and recombination of ssa among distinct group A streptococcal lineages. Although the extensive homology of SSA to the staphylococcal superantigen SEB raises the possibility of intergeneric gene transfer, a search for ssa in 68 genetically diverse clones of Staphylococcus aureus did not identify the gene. Moreover, the absence of ssa among 119 representative strains of Lancefield group B, C, or G streptococci suggests that ssa is confined to S. pyogenes.

Fatal group A streptococcal infection with toxic shock syndrome: complicating minor orthopedic trauma

Since 1987, reports have appeared of a streptococcal toxic shock syndrome in various clinical settings. None have appeared in the orthopaedic literature. Between 1989 and 1991 at our institution three patients with relatively minor orthopaedic injuries or procedures died of group A streptococcal infections complicated by toxic shock syndrome. The manifestations of this syndrome included rapid progression of systemic sepsis, necrotizing soft-tissue infections, acute renal failure, adult respiratory distress syndrome, and coagulopathy. All three patients died despite aggressive resuscitative measures and surgical debridement. Optimal treatment of this life-threatening process requires early recognition, aggressive surgical debridement, appropriate antibiotic management, and intensive care unit support.

Streptococcal toxic shock syndrome in a postpartum woman. Case report and review of the literature

A case of streptococcal toxic shock syndrome in a 29-year-old postpartum woman is described. The patient presented with hypotension, coagulation defects, adult respiratory distress syndrome and scarlet exanthema as a complication of hemolytic group A streptococcal endometritis. One hundred and twenty-two other cases of streptococcal toxic shock syndrome in the literature are reviewed and the criteria of the syndrome discussed. Streptococcal toxic shock syndrome seems to be increasing along with more frequent invasive streptococcal infections in several countries. It is therefore important to recognize and treat the infection as early as possible to minimize the risk of mortality.

Risk factors for invasive group A streptococcal infections in children with varicella: a case-control study

OBJECTIVE

To identify characteristic clinical manifestations and potential risk factors for invasive group A streptococcal (GAS) disease in children with varicella.

DESIGN AND PARTICIPANTS

A case-control study was conducted in Los Angeles and Orange Counties, CA. Cases were children with varicella who developed invasive GAS disease between January 1 and May 3, 1994 (n = 25). Controls were acquaintance, neighborhood or schoolmate children with uncomplicated varicella during the study period (n = 62). Cases were compared with controls with regard to underlying illness, child care practices, parental home health practices, health care-seeking behaviors, sociodemographic characteristics and clinical characteristics.

RESULTS

Controlling for age we found that cases were more likely than controls: (1) to be cared for in the home vs. out-of-home child care (odds ratio (OR), 4.4 (95% confidence interval (95% CI), 1.1 to 17)); (2) to report having asthma (OR, 6.2 (95% CI, 1.2 to 41.0)) and to be taking albuterol (OR, 11.6 ((95% CI, 1.0 to 581)); (3) to be secondary varicella cases within a household (OR, 7.3 (95% CI, 2.2 to 25)); (4) to report fever after Day 2 of varicella; and (5) to have contacted their health care provider later than controls (Day 3.8 rather than Day 1.7, P < 0.001).

CONCLUSIONS

To our knowledge this is the first case-control study exploring potential risk factors for invasive GAS disease in children with varicella. Both previously healthy children with varicella and those with underlying medical problems, including asthma, may be at increased risk for GAS complications. Interventions should be targeted to parents and health care providers to increase awareness of early signs and symptoms of invasive GAS disease in children with varicella. Additional studies are needed to confirm the associations suggested by this study between GAS complications of varicella and asthma, in-home child care, secondary vs. primary varicella household cases and delayed contact with medical care providers.

Invasive group A streptococcal infections in children with varicella in Southern California

OBJECTIVE

To describe demographic and clinical features of invasive group A streptococcal (GAS) infections in children with varicella in Southern California in early 1994.

METHODS

From hospitals of Los Angeles and Orange Counties, children with invasive GAS infections after varicella between January 1 and April 8, 1994, were identified by hospital infection control nurses. Medical records of patients were reviewed, and any available GAS isolate was further tested.

RESULTS

Twenty-four cases were identified; 54% were male, 50% were Hispanic and the median age was 3 years (range, 0.5 to 8). Four cases died before hospitalization. The other 20 were hospitalized for a median of 10 days (range, 4 to 50): 14 presented with cellulitis (1 with concomitant epiglottitis), 2 with myositis/necrotizing fasciitis, 2 with pneumonia and 2 with bacteremia without apparent source. Five had evidence of multiorgan involvement including two patients fulfilling criteria of streptococcal toxic shock-like syndrome. Of 19 patients with blood cultures, 10 (53%) had GAS bacteremia. Onset of GAS infection was suggested, as a median, on Day 4 of varicella, with fever, vomiting and localized swelling being commonly reported. The mean maximum temperature on the day of admission was 39.4 degrees C (102.9 degrees F). Four GAS isolates were M1T1 and one was M3T3. Five isolates produced streptococcal pyrogenic exotoxins A and B.

CONCLUSIONS

Invasive GAS disease, including streptococcal toxic shock-like syndrome, is a serious complication of varicella. Physicians should be alert for the complication of GAS when fever and localized swelling or signs of cellulitis develop 3 days or more after the onset of varicella. Widespread use of varicella vaccine may decrease invasive GAS infections in this setting.

The reemergence of serious group A streptococcal infections and acute rheumatic fever

Acute rheumatic fever and life-threatening group A streptococcal infections have reemerged during the past 15 years to once again become a serious health threat in the developed countries of the world. Reports of outbreaks of acute rheumatic fever in many parts of this country and others have shattered the complacency that the health-care community had acquired related to this devastating sequela of streptococcal pharyngitis. Invasive streptococcal infections, often associated with loss of limbs of life despite optimal antibiotic therapy, have underscored the potential virulence of these organisms. A new clinical entity, streptococcal toxic shock syndrome, has emerged as a consequence of the new invasive strains of group A streptococci. In this article, the authors summarize the recent changes in the epidemiology of group A streptococcal infections and rheumatic fever and review the potential reasons for the increased virulence of these organisms. In addition, they discuss prospects for a streptococcal M protein vaccine designed to control these infections and their sequelae.

Genetic heterogeneity of M type 3 group A streptococci causing severe infections in Tayside, Scotland

To explain the worldwide increase in the frequency of severe infections by group A streptococci, molecular techniques are increasingly being employed to evaluate the genetic relationships of strains. We used restriction endonuclease analysis, pulsed-field gel electrophoresis (PFGE), the PCR, ribotyping, and DNA sequence analysis in a study of 13 group A streptococci isolated from a cluster of cases of serious infections over a 3-month period in Tayside, Scotland. Eight of the strains were M type 3; molecular characterization identified two subclones. The first, displaying PFGE profile 4, has been observed in Northern Scotland and has been circulating in New Zealand for over a decade. The second subclone has been documented only in the United Kingdom; it was first seen in 1993 in Scotland. Sequence analysis of emm-3 genes further differentiated the PFGE 4 subclone. DNA sequence analysis of virulence factors supports the suggestion that they may have recently been acquired by horizontal gene transfer.

Streptococcal toxic shock-like syndrome. Report of two cases from Italy

Two cases of streptococcal toxic shock-like syndrome that occurred at our hospital are described. They represent the second and third cases reported from Italy. Both patients were women, had a portal of entry from cutaneous infection of a limb and suddenly developed high degree fever, severe hypotension, necrotizing fasciitis, acute renal failure, hepatic damage, thrombocytopenia and bleeding from a stress-related duodenal ulcer. One patient was leukopenic. The first patient needed resuscitation in the intensive care unit and emergency surgical debridement of the affected limb, whereas the second improved with medical therapy, but needed duodenal surgery for uncontrolled bleeding. Both patients slowly recovered and survived. Finally, a short update on the pathogenesis of the syndrome is also presented.

Molecular population genetic analysis of emerged bacterial pathogens: selected insights

Research in bacterial population genetics has increased in the last 10 years. Population genetic theory and tools and related strategies have been used to investigate bacterial pathogens that have contributed to recent episodes of temporal variation in disease frequency and severity. A common theme demonstrated by these analyses is that distinct bacterial clones are responsible for disease outbreaks and increases in infection frequency. Many of these clones are characterized by unique combinations of virulence genes or alleles of virulence genes. Because substantial interclonal variance exists in relative virulence, molecular population genetic studies have led to the concept that the unit of bacterial pathogenicity is the clone or cell line. Continued new insights into host parasite interactions at the molecular level will be achieved by combining clonal analysis of bacterial pathogens with large-scale comparative sequencing of virulence genes.

Incidence and severity of group A streptococcal bacteremia in a medical center in Israel, 1981-1994

To determine recent trends in the incidence and severity, group A streptococcal (GAS) bacteremia was studied over the last 14 years (1981-1994). There were 116 events of GAS bacteremia, representing 1.7% of all bacteremic episodes, without an increase in recent years. A total of 108 patients were available for study. Underlying conditions were found in 95 patients (88%), including mainly malignant diseases, chronic obstructive pulmonary disease, congestive heart failure and diabetes mellitus. A source of the bacteremia was noted in 71 patients (66%), with skin and soft tissue infection being the major portal of entry. All isolates were susceptible to penicillin. Overall mortality was 21%. Mortality had not increased in recent years, but depended significantly on several clinical factors: increased age; admission temperature; source of bacteremia (highest for GAS bacteremia without an identified source); and underlying conditions (highest for diabetes mellitus and chronic pulmonary disease, absent for patients with no underlying disease). This study shows that neither the incidence nor the severity of GAS bacteremia has increased in recent years. Severity is significantly affected by the source of bacteremia and the presence of underlying conditions.

Trends in incidence of AIDS associated with transfusion of blood and blood products in Europe and the United States, 1985-93

OBJECTIVE

To quantify patterns and trends in incidence of AIDS associated with transfusion of blood and its products in 14 European countries and the United States.

DESIGN

Data were derived from the World Health Organisation's European non-aggregate AIDS dataset and, for the United States, from the Centers for Disease Control AIDS public information dataset. Rates were standardised by using the world standard populations and adjusted for reporting delays in each country.

SUBJECTS

Cases of AIDS in patients with haemophilia and recipients of transfusions.

RESULTS

Overall, between 1985 and 1993 almost 6000 cases of AIDS associated with transfusions were registered in the 14 European countries considered and over 8000 in the United States between 1985 and 1992. Most European countries had annual age adjusted rates lower than 0.5 per million children aged 12 or less and between 1 and 2 per million adults. The United States had rates around 1 per million children and 5 per million adults in the most recent period. For children, the highest rates were generally reached in 1985-7, whereas in adults the highest rates were in the late 1980s. France had the highest overall incidence of AIDS related to transfusion in Europe (3.3 per million). Romania had a major epidemic in children (over 30 cases per million children in 1988-90). Incidence rates of AIDS associated with transfusion were still increasing in some southern European countries in the early 1990s.

CONCLUSIONS

Apart from in France and Romania it is clear that rates of bloodborne AIDS in European countries are lower than those registered in the United States.

Streptococcal gangrene of the eyelids and orbit

PURPOSE

Streptococcal gangrene, also termed streptococcal necrotizing fasciitis, is resurgent but remains exceedingly rare. Ophthalmologists and dermatologists must be aware of streptococcal gangrene, as eyelids are the most commonly affected area of the head and neck.

METHODS

We studied two cases of streptococcal gangrene of the orbit with clinical manifestations indistinguishable from common nonnecrotizing orbital cellulitis.

RESULTS

Infection progressed with dramatic rapidity to produce eyelid necrosis, respiratory failure, sepsis, and severe permanent visual loss caused by ophthalmic artery occlusions. Histopathologic analysis disclosed vascular thrombosis, necrosis, acute inflammation, and the presence of gram-positive cocci. Cultures grew heavy group A beta hemolytic Streptococcus. The first patient was infected with M type 1 carrying exotoxins A and B. The second patient was also infected with Streptococcus carrying exotoxin A.

CONCLUSION

Early diagnosis of this life-threatening infection is of paramount importance because survival may depend on early surgical debridement.

A cluster of cases of streptococcal necrotizing fasciitis in Gloucestershire

We describe the first cluster of cases of necrotizing fasciitis (NF) in this century in the United Kingdom (UK). Between 1 January and 30 June 1994 there were six cases (five confirmed, one probable) of Streptococcus pyogenes NF in west Gloucestershire, population 320,000. Two cases died. The first two patients probably acquired their infections during the course of elective surgery performed in the same operating theatre, possibly from a nasopharyngeal carrier amongst the theatre staff. The remaining infections were community-acquired. Of 5 S. pyogenes isolates there were 2 M1 strains, 1 M3, 1 M5 and 1 M non-typeable strain. S. pyogenes NF had not been recorded in west Gloucestershire in the preceding 10 years and the incidence of S. pyogenes bacteraemia in England and Wales had not risen in the past 5 years. The two presumably theatre-acquired infections raised several issues. The need for detailed bacteriological investigation of all cases of post-surgical NF was confirmed. Clusters of S. pyogenes infection following surgery should be managed by closure of the operating theatre until all staff have been screened for carriage. Closure of an operating theatre and screening of staff following a sporadic case is probably not justified because of the infrequency of surgical cross-infection with S. pyogenes. Regular, routine screening of theatre staff is neither practical nor necessary.

Regulation of virulence by environmental signals in group A streptococci: influence of osmolarity, temperature, gas exchange, and iron limitation on emm transcription

Transcription of the gene encoding the antiphagocytic M protein (emm) of the group A streptococci has been shown to be regulated by CO2 (M. G. Caparon, R. T. Geist, J. Perez-Casal, and J. R. Scott, J. Bacteriol. 174:5693-5701, 1992). We tested the influence of additional environmental growth conditions on emm expression. Increased osmolarity, low temperature, growth with free exchange of gasses, or the restricted availability of iron resulted in decreased transcription from the emm promoter.

Evidence for a streptococcal superantigen-driven process in acute guttate psoriasis

Recent studies have suggested that T cells play a critical role in the pathogenesis of psoriasis. Guttate psoriasis is a well-defined form of psoriasis frequently associated with streptococcal throat infection. This study tested the hypothesis that T cells in acute guttate psoriasis skin lesions may be activated by streptococcal superantigens. Peripheral blood as well as lesional and perilesional skin biopsies were analyzed for T cell receptor V beta repertoire using monoclonal antibodies against 10 different V beta families. Skin biopsies from all patients with acute guttate psoriasis, but not skin biopsies from patients with acute atopic dermatitis or inflammatory skin lesions induced in normal subjects with sodium lauryl sulfate, demonstrated selective accumulation of V beta 2+ T cells (P < 0.05). The expansion of V beta 2+ T cells occurred in both the CD4+ and the CD8+ T cell subsets. Sequence analysis of T cell receptor beta chain genes of V beta 2-expressing T cells from skin biopsies of patients with guttate psoriasis showed extensive junctional region diversity that is more compatible with a superantigen rather than a conventional (nominal) antigen-driven T cell response. All streptococcal isolates from patients with guttate psoriasis secreted streptococcal pyrogenic exotoxin C, a superantigen known to stimulate marked V beta 2+ T cell expansion. These data support the concept that acute guttate psoriasis is associated with superantigenic stimulation of T cells triggered by streptococcal superantigen(s).

Molecular structure of staphylococcus and streptococcus superantigens

Staphylococcus aureus and streptococci, notably those belonging to group A, make up a large family of true exotoxins referred to as pyrogenic toxin superantigens. These toxins cause toxic shock-like syndromes and have been implicated in several allergic and autoimmune diseases. Included within this group of proteins are the staphylococcal enterotoxins, designated serotypes A, B, Cn, D, E, and G; two forms of toxic shock syndrome toxin-1 also made by Staphylococcus aureus; the group A streptococcal pyrogenic exotoxins, serotypes A, B, and C; and recently described toxins associated with groups B, C, F, and G streptococci. The nucleotide sequences of the genes for all of the toxins except those from the groups B, C, F, and G streptococcal strains have been sequenced. The sequencing studies indicate that staphylococcal enterotoxins B and C and streptococcal pyrogenic exotoxin A share highly significant sequence similarity; staphylococcal enterotoxins A, D, and E share highly significant sequence similarity; and toxic shock syndrome toxin-1 and streptococcal pyrogenic exotoxin B and C share little, if any, sequence similarity with any of the toxins. Despite the dissimilarities seen in primary amino acid sequence among some members of the toxin family, it was hypothesized that there was likely to be significant three-dimensional structure similarity among all the toxins. The three-dimensional structures of three of the pyrogenic toxin superantigens have been determined recently. The structural features of two of these, toxic shock syndrome toxin-1 and enterotoxin C3, are presented. Toxic shock syndrome-1 exists as a protein with two major domains, referred to as A and B. The molecule begins with a short N-terminal alpha-helix that then leads into a clawshaped structure in domain B that is made up of beta strands.

Clonal structure of invasive Streptococcus pyogenes in Northern Scotland

We have used molecular techniques to characterize 51 group A streptococci from Scotland and 17 'serious disease' isolates from other countries, in order to establish the clonal structure of invasive Streptococcus pyogenes strains circulating between 1986 and 1993. Strains were grouped by restriction endonuclease analysis, pulsed field gel electrophoresis and ribotyping patterns, and were examined for the presence of alleles of the speA gene by polymerase chain reaction and DNA sequence analysis. Serious and fatal infections in Scotland were caused by several clones. One clone (9 of 51 strains) was M type 1 and possessed the speA gene allele 2. This was the clone previously identified as causing severe infection in the USA. Another clone (5 of 51 strains) was M type 3 and had speA gene allele 3. In view of the clear association of more than one clone with severe, invasive and fatal infections, horizontal gene exchange between genotypes merits further investigation.

Septic pulmonary thrombosis in streptococcal toxic shock syndrome

A 60-year-old woman who was previously in good health presented with a sore throat, fever, and a flu-like syndrome. Treated initially with acetaminophen and fluids for a presumed viral infection, she had a syncopal episode 4 days later, was admitted to the hospital, and died 3 hours after admission. Laboratory test results suggested sepsis with disseminated intravascular coagulation (DIC), whereas blood cultures grew group A beta-hemolytic streptococci. A postmortem diagnosis of streptococcal toxic shock syndrome was established. It was of particular interest that the pulmonary microcirculation was filled with thrombi that contained numerous gram-positive cocci. Although death from sepsis with DIC is not uncommon, septic pulmonary thrombosis has not been previously described. We speculate that this paradox may reflect unique properties of the virulent strains of Streptococcus pyogenes that are associated with streptococcal toxic shock syndrome.

Tumor necrosis factor production by human T-cells stimulated with bacterial superantigens

Tumor necrosis factor (TNF) production from T-cells stimulated with superantigenic exotoxins, staphylococcal enterotoxin B and streptococcal pyrogenic exotoxin A was investigated in the presence of cells bearing distinct isotypes of HLA class II molecules. The main T-cell subset for TNF production was investigated in parallel. Similarly high levels of TNF production were induced upon stimulation with the toxins in the presence of DR+ or DQ+ cells, but only marginal levels of TNF production were induced in the presence of DP+ cells. Although both CD4+ T-cells and CD8+ T-cells produced TNF-alpha and TNF-beta in response to toxin stimulation in the presence of HLA class II+ cells, the former T-cell subset was the major source of producers of TNF-alpha and TNF-beta.

In vivo effects of superantigens

Superantigens are potent immunostimulatory molecules that activate both T cells and antigen presenting cells. The consequences of superantigen exposure range from induction of T cell proliferation, massive cytokine release and systemic shock to immunosuppression and tolerance. Superantigens have been directly implicated in a number of human conditions including food poisoning and toxic shock. In addition, there is evidence to suggest that superantigens are involved in the initiation of autoimmunity, and the immune dysfunction associated with HIV infection. Because of their possible role in human disease, and their potential use in immune therapy, it is important that we more completely understand the in vivo effects of superantigens.

Streptococcal preseptal cellulitis complicated by the toxic Streptococcus syndrome

BACKGROUND

After decades of decline in the incidence of severe infections secondary to group A streptococci, a dramatic increase in the frequency and severity of infections with these organisms has been reported since 1984, including a "toxic Streptococcus syndrome," resembling staphylococcal toxic shock syndrome. To the authors' knowledge, this entity has never been described after ocular infection.

METHODS

In a previously healthy 3-year-old boy, preseptal cellulitis developed secondary to minor trauma to the eyelid, progressing rapidly to hypotension, respiratory distress, and an erythrodermic desquamating rash. Ocular and blood cultures grew group A beta-hemolytic streptococci. Appropriate antibiotic coverage and management of systemic manifestations led to rapid improvement, although necrosis developed in the right upper anterior eyelid, requiring skin grafts.

RESULTS

More than 3 years since the incident, the patient is free of infection and has a good cosmetic result after skin grafting and revisions for scarring and adhesions.

CONCLUSIONS

Streptococcal preseptal cellulitis is not unusual, particularly after trauma. Ophthalmologists must be aware of the re-emergence of more virulent organisms with increased potential for morbidity and mortality.

Distinct profiles of immunoglobulin G-binding-protein expression by invasive serotype M1 isolates of Streptococcus pyogenes

Analysis of immunoglobulin G (IgG)-binding-protein expression by invasive group A streptococcal isolates of the M1 serotype collected as part of a Centers for Disease Control and Prevention surveillance study revealed two distinct phenotypes. One group of type M1 isolates expressed a surface protein reactive with all four human IgG subclasses (type IIo), while a second group expressed a surface protein demonstrating significant reactivity only with human IgG3 (type IIb). The functional forms of IgG-binding protein were antigenically related, and both were recognized by a rabbit polyclonal antiserum to serotype M1 but not by normal rabbit serum. While the quantities of antigenic M1 protein present in the extracts of representative isolates displaying each phenotype differed, the functional differences were found to be qualitative and not solely quantitative. The IgG-binding properties of these antigenically related M1 proteins could be readily distinguished from those of another IgG-binding protein, protein H. Type M1 isolates of the IIb phenotype differed from those of the IIo phenotype by secreting larger amounts of a casein-hydrolyzing protease into culture supernatants.

Toxic shock syndrome: an opportunity for nursing intervention

Toxic Shock Syndrome (TSS) is a potentially fatal illness caused by a particular strain of Staphylococcus aureus. The clinical presentation is similar to that of septic shock. The incidence of TSS peaked in the late 1970s and early 1980s, probably as a result of availability of super absorbent tampons. Although most commonly associated with menstruation, the overall incidence of menstrual and nonmenstrual TSS in men and women ranges from 1 to 3 per 100,000. There are almost equal numbers of menstrual and nonmenstrual cases of TSS identified annually. S aureus, the causative microorganism in cases of TSS, has been isolated from many body tissues. Toxic shock syndrome presents as a flu-like illness with high fever, vomiting, diarrhea, general malaise, and muscle weakness. Nursing and medical management focus on controlling or preventing potentially serious complications, such as adult respiratory distress syndrome, renal failure, electrolyte imbalances, disseminated intravascular coagulation, encephalopathy, and cardiomyopathy. Judicious use of tampons and barrier contraceptive devices may decrease the risk of developing TSS.

Cutaneous colonization with staphylococci influences the disease activity of Sézary syndrome: a potential role for bacterial superantigens

It has previously been shown that circulating Sézary cells respond in vitro to superantigenic staphylococcal exotoxins in a manner that is restricted by their V beta usage. This study was conducted to examine whether cutaneous colonization with Staphylococcus aureus influences the activity of the skin lesions of Sézary syndrome, and whether S. aureus isolated from patients with Sézary syndrome stimulates circulating Sézary cells in vitro. Two patients with Sézary syndrome, whose skin was colonized with S. aureus, were treated with antibacterial agents, and the relation between the severity of the skin disease and the degree of S. aureus colonization was assessed. In addition, the patients' peripheral blood mononuclear cells were cultured in the presence of mitomycin C-treated S. aureus or superantigenic staphylococcal toxins. The antibacterial treatment improved the skin disease, and eliminated S. aureus in both patients. In one patient, 98% of the peripheral blood mononuclear cells bore V alpha 2V beta 17 of the T-cell receptor, indicative of the presence of an extremely high percentage of circulating Sézary cells. The peripheral blood lymphocytes from this patient responded well in vitro to superantigenic staphylococcal enterotoxin (SE), but not to SEA or toxic shock syndrome toxin-1, or to mitomycin-treated S. aureus isolated from the same patient. Cutaneous colonization by S. aureus influences the disease activity of CTCL, possibly by activation of Sézary cells by bacterial superantigenic exoproteins.

Bacterial pyrogenic exotoxins as superantigens

The recent discovery of the mode of interaction between a group of microbial proteins known as superantigens and the immune system has opened a wide area of investigation into the possible role of these molecules in human diseases. Superantigens produced by certain viruses and bacteria, including Mycoplasma species, are either secreted or membrane-bound proteins. A unique feature of these proteins is that they can interact simultaneously with distinct receptors on different types of cells, resulting in enhanced cell-cell interaction and triggering a series of biochemical reactions that can lead to excessive cell proliferation and the release of inflammatory cytokines. However, although superantigens share many features, they can have very different biological effects that are potentiated by host genetic and environmental factors. This review focuses on a group of secreted pyrogenic toxins that belong to the superantigen family and highlights some of their structural-functional features and their roles in diseases such as toxic shock and autoimmunity. Deciphering the biological activities of the various superantigens and understanding their role in the pathogenesis of microbial infections and their sequelae will enable us to devise means by which we can intervene with their activity and/or manipulate them to our advantage.

Antibiotic resistance in group A streptococci

Although erythromycin resistance in GABHS has been a major problem in Japan and in Finland, it has not been a problem in the United States. The susceptibility of GABHS to the newer macrolide antibiotics seems to be similar to that of erythromycin. Comprehensive, community-wide programs to continuously monitor for erythromycin resistance in GABHS would be difficult to justify; however, because little is known about how erythromycin resistance in GABHS is acquired or spread, it would be reasonable to periodically monitor isolates of GABHS for erythromycin resistance. Despite more than four decades of use of penicillin in treating GABHS infections, no significant change has occurred in the in vitro susceptibility of GABHS to penicillin. The resurgence of severe, invasive GABHS infections and of acute rheumatic fever is not attributable to the emergence of strains of GABHS with increased resistance to penicillin. A substantial proportion of GABHS are currently resistant to tetracyclines, and these agents are inappropriate for treating GABHS infections. Although little recent information is available about the susceptibility of GABHS to sulfonamides, these agents have been shown to be ineffective in eradicating GABHS form the upper respiratory tract regardless of the in vitro sensitivities. GABHS have not been shown to be resistant to any of the commonly used oral cephalosporins; however, a great deal of variability exists among these agents in their activity against GABHS. Clindamycin resistance in GABHS has remained unusual. This agent is an alternative for treating GABHS infections due to macrolide-resistant strains in patients who cannot be treated with beta-lactam antibiotics.

Determinants of mortality for necrotizing soft-tissue infections

OBJECTIVE

The authors determined the risk factors of mortality in patients with necrotizing soft-tissue infections (NSTIs) and examined the incidence and mortality from NSTI secondary to Streptococcus pyogenes.

METHODS

All patients with NSTIs who were treated between January 1989 and June 1994 were analyzed for presentation, etiology, factors important in pathogenesis and treatment, and mortality.

RESULTS

Sixty-five patients were identified with NSTIs secondary to postoperative wound complications (18), trauma (15), cutaneous disease (15), idiopathic causes (10), perirectal abscesses (3), strangulated hernias (2), and subcutaneous injections (2). Necrotizing soft-tissue infections were polymicrobial in 45 patients (69%). S. pyogenes was isolated in only 17% of the NSTIs, but accounted for 53% of monomicrobial infections. Eight of ten idiopathic infections were caused by a single bacterium (p = 0.0005), whereas 82% of postoperative infections were polymicrobial. An average of 3.3 operative debridements per patient and amputation in 12 patients were necessary to control infection. The overall mortality was 29%; mortality from S. pyogenes infection was only 18%. The average time from admission to operation was 90 hours in nonsurvivors versus 25 hours in survivors (p = 0.0002). Other risk factors previously associated with the development of NSTIs did not affect mortality.

CONCLUSIONS

Early debridement of NSTI was associated with a significant decrease in mortality. S. pyogenes infection was the most common cause of monomicrobial NSTI, but was not associated with an increased mortality.

Maternal death following epidural anaesthesia for caesarean section delivery in a patient with unsuspected sepsis

Sepsis in the parturient may be difficult to recognize in light of the physiological changes associated with pregnancy. The purposes of this report are to highlight the signs and symptoms which indicate an underlying septic process and the management of these patients in the peripartum period. This 32-yr-old GII PI woman with twin gestation presented at 36 wk in labour. Her temperature was 35.3 degrees C, she was normotensive and had a normal white blood cell count. After epidural anaesthesia was administered for Caesarean section, she became apnoeic, pulseless and unresponsive. Despite aggressive cardiopulmonary resuscitation, neither she nor her twin babies survived. Post mortem blood work revealed a considerable left shift of her white blood count (> 60% bands) and an anion gap acidosis. Autopsy revealed evidence of widespread Group A beta-haemolytic streptococcal sepsis. Diagnosis of sepsis in the parturient involves assessment of the patient's temperature, WBC and differential and acid-base status. Evaluation of the intravascular volume must precede anaesthetic intervention. Epidural anaesthesia may be considered in the labouring and Caesarean section patient who has been fluid-resuscitated. Emergency operative delivery may result in cardiovascular compromise in the patient with severe sepsis.

Diagnosis and treatment of group a streptococcal pharyngitis

Pharyngitis caused by the group A streptococcus requires accurate diagnosis and timely treatment to prevent acute rheumatic fever. Clinical signs and symptoms often do not distinguish pharyngitis caused by group A streptococci from pharyngitis caused by other microorganisms. Rapid antigen detection or throat culture are recommended for diagnosis except when viral signs and symptoms are prominent. Therapy with penicillin, the drug of choice, is associated with prevention of rheumatic fever, more rapid clinical improvement, and prompt loss of contagiousness. Bacteriologic treatment failure occurs despite universal sensitivity of group A streptococci to penicillin. The cause of treatment failure (and of chronic carriage) remain to be determined. Newer, more expensive antibiotics do not substantially enhance treatment success and need not be prescribed for most patients.