Invasive group A streptococcus infections

Group A streptococcal isolate 64/14 expresses surface plasmin-binding structures in addition to Plr

A recombinant plasmin receptor (Plr) gene product originally cloned from group A streptococcal isolate 64/14 was analysed for its ability to bind plasmin(ogen) and to account for all the surface plasmin-binding properties of streptococcal isolate 64/14. Functional analysis of recombinant Plr demonstrated that the protein exhibited equal reactivity with human Lys-plasmin and Lys-plasminogen, but significantly lower reactivity with Glu-plasminogen. Plasmin-binding was both inhibitable and elutable by lysine or lysine analogs, and active plasmin bound to recombinant Plr was not neutralized by alpha 2-antiplasmin. Thus, the plasmin-binding properties of recombinant Plr correlated with the plasmin-binding phenotype of the intact streptococcal isolate 64/14. In addition, fluid-phase recombinant Plr could completely inhibit binding of plasmin to either immobilized recombinant Plr or group A streptococcal isolate 64/14 with equal efficiency, indicating that surface-expressed Plr could account for all the plasmin-binding properties of the intact organism. An IgM monoclonal antibody to recombinant Plr that specifically recognized a surface structure on streptococcal isolate 64/14 significantly inhibited the binding of plasmin to the recombinant protein; however, the antibody was not successful at inhibiting plasmin-binding to the intact bacteria, indicating the presence of other plasmin-binding structures on the bacterial surface in addition to Plr.

Diagnostic value of cerebrospinal fluid examination in children with peripheral facial palsy and suspected Lyme borreliosis

Our objective was to determine the diagnostic value of CSF examinations in the diagnosis of neuroborreliosis in children with peripheral facial palsy (PFP). Paired serum and CSF samples from 21 children with PFP were investigated for antibody responses to Borrelia burgdorferi antigens using three different ELISA systems and one Western blot assay. Twenty of the children (95%) had detectable immunoglobin (Ig) M or IgG in the acute-phase serum, but discrepancies between serologic assays were noted in 33% for IgM and 22 to 50% for IgG. Intrathecal specific-antibody production was detected in five of the 20 seropositive children (25%). These five patients showed seroconversion in convalescent sera in at least one assay. Similar seroconversion suggesting recent infection with B. burgdorferi was observed in eight of the 10 children (80%) without intrathecal specific-antibody production, from whom convalescent serum samples could be obtained. All patients with intrathecal antibodies or seroconversion had shown lymphocytic pleocytosis in the acute phase of PFP. In the acute phase of PFP the detection of intrathecal production of antibodies to B. burgdorferi allows prompt diagnosis of neuroborreliosis. For patients with lymphocytic pleocytosis but no detectable intrathecal antibodies, analysis of convalescent serum may help to establish this diagnosis.

Role of mga in growth phase regulation of virulence genes of the group A streptococcus

To determine whether growth phase affects the expression of mga and other virulence-associated genes in the group A streptococcus (GAS), total RNA was isolated from the serotype M6 GAS strain JRS4 at different phases of growth and transcript levels were quantitated by hybridization with radiolabeled DNA probes. Expression of mga (which encodes a multiple gene regulator) and the Mga-regulated genes emm (which encodes M protein) and scpA (which encodes a complement C5a peptidase) was found to be maximal in exponential phase and shut off as the bacteria entered stationary phase, while the housekeeping genes recA and rpsL showed constant transcript levels over the same period of growth. Expression of mga from a foreign phage promoter in a mga-deleted GAS strain (JRS519) altered the wild-type growth phase-dependent transcription profile seen for emm and scpA, as well as for mga. Therefore, the temporal control of mga expression requires its upstream promoter region, and the subsequent growth phase regulation of emm and scpA is Mga dependent. A number of putative virulence genes in JRS4 were shown not to require Mga for their expression, although several exhibited growth phase-dependent regulation that was similar to mga, i.e., slo (which encodes streptolysin O) and plr (encoding the plasmin receptor/glyceraldehyde-3-phosphate dehydrogenase). Still others showed a markedly different pattern of expression (the genes for the superantigen toxins MF and SpeC). These results suggest the existence of complex levels of global regulation sensitive to growth phase that directly control the expression of virulence genes and mga in GAS.

Population-based surveillance for group A streptococcal necrotizing fasciitis: Clinical features, prognostic indicators, and microbiologic analysis of seventy-seven cases. Ontario Group A Streptococcal Study

PURPOSE

To determine the incidence of group A streptococcal necrotizing fasciitis in Ontario, Canada, and to describe the clinical features, outcome, and microbiologic characteristics of this infection.

PATIENTS AND METHODS

Prospective, population-based surveillance for invasive group A streptococcal infections was conducted in Ontario from November 1991 to May 1995. All 77 patients meeting clinical and/or histopathologic criteria for streptococcal necrotizing fasciitis were included. Demographic and clinical information was obtained by patient interviews and chart review. Group A streptococci were characterized by M-protein and T-agglutination typing, and polymerase chain reaction (PCR) detection of streptococcal pyrogenic exotoxin genes A and C (speA; speC).

RESULTS

The incidence of group A streptococcal necrotizing fasciitis increased during the study from 0.085 per 100,000 population in the first year to 0.40 per 100,000 population in the last year (P < 0.001). The median age of cases was 57.5 years and the rate of disease increased with increasing age. Seventy-nine percent of cases were community-acquired, 11% were nosocomial, and 10% were acquired in a nursing home. Forty-seven percent of cases were associated with the presence of streptococcal toxic shock syndrome (Strep TSS) and 46% were bacteremic. Thirty-four percent of cases died and mortality was correlated with increasing age (P = 0.006), presence of hypotension (P = 0.01), and bacteremia (P = 0.03). The most common streptococcal serotypes were M1 (35%) and M3 (25%). Forty-one percent of strains possessed the speA gene and 30% the speC gene. Outcome was not correlated with M-type or the presence of spe genes.

CONCLUSIONS

The incidence of necrotizing fasciitis caused by group A streptococcus increased in Ontario between 1992 and 1995. Elderly individuals were more likely to acquire the disease and to die from it. Mortality because of streptococcal necrotizing fasciitis was also associated with the presence of hypotension, Strep TSS, or bacteremia, but not with M-type or the presence of pyrogenic exotoxin genes.

Superantigenicity of helper T-cell mitogen (SPM-2) isolated from culture supernatants of Streptococcus pyogenes

A superantigen (Streptococcus pyogenes mitogen-2; SPM-2) that stimulates human helper T cells bearing unique types of variable domains of T-cell receptor beta-chain (TCR V beta) was isolated from the culture supernatant of S. pyogenes strain T12. The active molecule isolated by diethylaminoethyl (DEAE)-cellulose chromatography and isoelectric focusing was a protein with a molecular weight (MW) of 29,000 and isoelectric point (pl) of 6.0. This new superantigen was found to activate preferentially V beta 4+, 7+, and 8+ T cells, whereas recombinant streptococcal pyrogenic exotoxin A and C activated V beta 12+ and V beta 2+ T cells, respectively, as determined by flow cytometry and reverse transcriptase-polymerase chain reaction (RT-PCR) methods. This proliferative response was significantly inhibited by anti-HLA-DR monoclonal antibody, and required paraformaldehyde-fixed antigen-presenting cells (APC), indicating that this action is dependent on major histocompatibility complex (MHC) class II molecules without processing. Analysis of the amino-terminal amino acid sequence of the molecule failed to find any identical or significantly homologous proteins. We have previously reported that cytoplasmic membrane-associated protein (CAP), a streptococcal superantigen isolated from the cell membranes of S. pyogenes T12 strain, stimulated mainly V beta 8+ T cells. Both SPM-2 and CAP preferentially stimulated helper T cells, and rabbit antiserum against SPM-2 completely neutralized the T-cell-stimulating activities of CAP, suggesting that SPM-2 and CAP belong to a family of streptococcal mitogenic proteins. The SPM-2 activity with stimulation of V beta 8+ T cells was detected extensively in the culture fluids of group A streptococci, but not in those of other streptococcal species, including groups B and D streptococci, and most of the activities detected were completely inhibited by anti-SPM-2 serum. These results indicate that SPM-2 may be a newly discovered superantigen molecule, which can be commonly synthesized by group A streptococci.

Streptococcal toxic shock syndrome complicating preseptal cellulitis

PURPOSE

Although substantial morbidity is uncommon in preseptal cellulitis, the incidence of severe infection resulting from group A streptococcal infection is increasing.

METHODS

A 62-year-old man was initially examined for preseptal cellulitis sustained after minor trauma to his brow. The patient rapidly experienced shock and multisystem organ failure. Intensive medical therapy prevented circulatory collapse and death.

RESULTS

A diagnosis of streptococcal toxic shock syndrome secondary to group A beta hemolytic streptococcal infection was made based on culture results and clinical course.

CONCLUSIONS

The ophthalmologist plays an essential role in diagnosing this condition. Aggressive and timely treatment are essential to preventing death.

The role of nitric oxide in experimental murine sepsis due to pyrogenic exotoxin A-producing Streptococcus pyogenes

Nitric oxide (NO) produced by inducible NO synthase (iNOS) mediates hypotension in endotoxemia. In this study, NO induction by a toxin-producing Streptococcus pyogenes isolate, H250, and by recombinant streptococcal pyrogenic exotoxin A (rSPEA) has been examined, both in vitro and in vivo. Streptococcal supernatants, but not rSPEA, induce production of nitrite by murine macrophages when both are coincubated with gamma interferon. Intraperitoneal injection of rSPEA did not cause significant production of NO. However, an elevated level of nitrate in serum was detected in a model of streptococcal fasciitis due to live H250. iNOS was localized to Kupffer cells, hepatocytes, and renal tubular cells by immunostaining. Administration of a NOS inhibitor, N(G)-monomethyl-L-arginine (L-NMMA), reduced peak concentrations of nitrate in serum but did not affect survival. NO is induced by H250, both in vitro and in vivo, mainly via SPEA-independent mechanisms. In this model, iNOS is expressed predominantly in the liver. Furthermore, in this model L-NMMA is not protective.

New aspects of exanthematous diseases of childhood

The childhood exanthems include a spectrum of common and uncommon disorders caused by a variety of pathogens. In this article, timely issues relating to immunization for measles and varicella are discussed. Recently reported exanthematous illnesses, including papular-purpuric gloves and socks syndrome, unilateral laterothoracic exanthem, and eruptive pseudo-angiomatosis, are described. The current research and debate about bacterial toxins as the cause of Kawasaki syndrome are presented.

Pediatric dermatology: advances in therapy

Several recent therapeutic advances in pediatric dermatology have been made. Of particular importance are new developments in the use of antimicrobials, antivirals, antifungals, retinoids, calcipotriene, and intravenous gamma globulin. We review safety and efficacy data of these drugs in their use in children with cutaneous disease.

Changing epidemiology of invasive Streptococcus pyogenes infections in southern Israel: differences between two ethnic population groups

BACKGROUND

Two ethnic populations (westernized Jews and Bedouins in transition from semi-nomadic to sedentary life conditions) living in Southern Israel and receiving inpatient services in the only medical facility of the region.

OBJECTIVE

To determine whether the incidence and severity of Streptococcus pyogenes infections among Jewish and Bedouin children have changed over the years.

STUDY DESIGN

Retrospective (1980 to 1994), population-based. Medical charts of children younger than 15 years of age hospitalized with S. pyogenes bacteremia and/or severe invasive infection were reviewed. Incidence rates of bacteremia among Jewish and Bedouin children were calculated separately.

RESULTS

The incidence of S. pyogenes bacteremia was 2.82/100,000 between 1980 and 1984, was 2.58/100,000 between 1985 and 1989 and rose significantly during 1990 through 1994 to 4.82/100,000 (P < 0.01). The observed increment was the result of a significant increase among the Jews, whereas the incidence among the Bedouin population remained relatively stable. Streptococcal toxic shock syndrome was diagnosed in three Jewish patients between 1992 and 1994. No predominance of any particular streptococcal M-type was observed.

CONCLUSIONS

The incidence of pediatric S. pyogenes bacteremia has increased in Southern Israel in recent years. This increase has occurred among the Jewish population, among which the first cases of streptococcal toxic shock syndrome have recently occurred. The increased incidence observed is not the result of dissemination of a single virulent streptococcal clone.

Serotyping and susceptibility to macrolides and other antimicrobial drugs of Streptococcus pyogenes isolated from patients with invasive diseases in southern Israel

Fifty-seven strains of Streptococcus pyogenes isolated from septic patients and 52 isolates from nonbacteremic patients in southern Israel were investigated for their susceptibility to new macrolides and other antimicrobial drugs. In addition, typing of the isolates by M protein and T antigen was performed. All organisms were susceptible to penicillin and chloramphenicol, 59% to tetracycline, and 7% to trimethoprim-sulfamethoxazole. All isolates but one (99%) were susceptible to clarithromycin, azithromycin, erythromycin, and clindamycin. The MIC90 of clarithromycin, erythromycin, and clindamycin was 0.064, 0.125, and 0.094 microgram/ml, respectively. Overall, 96% of the isolates could be typed by T antigen, but only 43% were M-protein typeable. No predominance of any particular M-protein type was observed. No significant differences between blood isolates and organisms derived from other sources were observed in the antibiotic susceptibility patterns or the distribution of serotypes. It is concluded that invasive Streptococcus pyogenes infections in southern Israel are caused by multiple unrelated strains. The organism remains susceptible to macrolides and clindamycin.

A clinical study of beta-haemolytic groups A, B, C and G streptococcal bacteremia in adults over an 8-year period

All of the 88 episodes of beta-haemolytic streptococcal bacteremia (2.9% of all bacteremias) in adult patients during the years 1987-94 in a university hospital were reviewed. 38 bacteremias (43%) were caused by group A, 24 (27%) by group B, 3 (4%) by group C, and 23 (26%) by group G beta-haemolytic streptococcal. There was a statistically significant increase in group A and decrease in group C and G bacteremias (p < 0.02) compared to an earlier 8-year period in the same hospital, although the total number of streptococcal bacteremias remained the same. The most common T types of group A streptococcal strains were T11 (26%), T28 (14%), T6 and T1 (11% each), and T12 (8%). Cardiovascular disease, skin lesions, malignancy, and alcohol abuse were the most common underlying conditions. The most usual types of infection were skin (47%) and respiratory tract infections (23%). The overall mortality was 16%. It was highest in group A (24%) and lowest in group C (0%), 38% of patients with pneumonia died. All streptococcal strains were sensitive to penicillin, vancomycin, and cephalosporins. 11% of group A and 12% of all the strains had decreased sensitivity to erythromycin, 14 and 38% to tetracycline, and 0 and 2% to clindamycin, respectively.

The toxins of group A streptococcus, the flesh eating bacteria

Streptococcus pyogenes causes a wide variety of infections in individuals of all ages in most countries of the world. Because of the frequency with which these infections occur, physicians are quite familiar with the diversity of clinical presentations associated with the Group A streptococcus. Yet in the late 1980's, a severe form of streptococcal infection, the Streptococcal Toxic Shock Syndrome, emerged and has persisted for the last 10 years. This syndrome is associated with invasive soft tissue infections and the early onset of shock and organ failure. The purpose of this paper is to briefly describe the epidemiologic and clinical features of the Streptococcal Toxic Shock Syndromes and to emphasize the role that toxins produced by S. pyogenes play in the pathogenesis of this disease.

Superantigens: their role in infectious diseases

In the last 10 years many of the superantigens of the microbial world have been defined and the mechanisms of cellular interaction between lymphocytes and antigen presenting cells has been elucidated in great detail. The consequences of superantigen stimulation of the immune system, though less well defined, can be considered in three separate stages: T-cell proliferation, apoptosis, and recovery. Understanding these stages may explain why diverse superantigens may cause markedly different clinical processes ranging from acute shock to chronic arthritis and may form the basis for novel treatments of these diverse diseases.

Acquisition of iron from host proteins by the group A streptococcus

To identify mammalian iron-binding proteins that can serve as iron sources for Streptococcus pyogenes, the group A streptococcus (GAS), we used a plate assay. Ferritin, hemin, hemoglobin, myoglobin, and catalase can support growth of GAS on iron-depleted medium. However, growth was not detected when iron was provided as iron-saturated transferrin or lactoferrin or bound to cytochrome c. Therefore, it appears that GAS can use the intracellular iron sources available in the human body, which is consistent with its ability to cause tissue destruction during infection.

The toxic shock syndromes

Because of the frequency with which Staphylococcus aureus and Streptococcus pyogenes infections occur, physicians are quite familiar with the diversity of their clinical presentations. In the 1970s, however, shock associated with multiorgan failure was described in menstruating female patients as well as in male patients following a variety of surgical procedures, such as rhinoplasty. This previously undescribed presentation of S. aureus infection, termed staphylococcal toxic shock syndrome, was associated with unique strains of S. aureus. In the mid-1980s, the emergence of streptococcal toxic shock syndrome was heralded by several case reports describing patients with group A streptococcal infections associated with shock and organ failure. This article compares the differences in the epidemiologic, clinical, and pathophysiologic features of the toxic shock syndromes.

Temperature regulation of the streptococcal pyrogenic exotoxin A-encoding gene (speA)

The gene encoding the bacterial superantigen streptococcal pyrogenic exotoxin A is often found in streptococcal strains associated with the recently described streptococcal toxic shock syndrome. Here we demonstrate that this gene is expressed at approximate fourfold higher levels in cells grown at 37 degrees C when compared to cells grown at 26 degrees C. This suggests there is increased production of this toxin when Streptococcus pyogenes is found in infections of the soft tissues and bloodstream, as opposed to S. pyogenes that have not breached the epithelial layers and are living on the surface of the skin.

Evidence for the presence of streptococcal-superantigen-neutralizing antibodies in normal polyspecific immunoglobulin G

Recently we demonstrated that normal polyspecific immunoglobulin given intravenously (IVIG) and plasma samples from patients treated with IVIG neutralize the mitogenic and cytokine-inducing activities of group A streptococcal (GAS) superantigens. Here we investigated whether this neutralizing activity is mediated by antibodies to these superantigens. IVIG and plasma samples collected from a patient with GAS necrotizing fasciitis post-IVIG infusions markedly inhibited the mitogenic activity elicited by the streptococcal pyrogenic exotoxins SpeB and SpeC, as well as by GAS culture supernatant. Immunoblot analysis showed marked increases in the levels of antibodies to SpeC and proteins in the GAS culture supernatant in post-IVIG over those of pre-IVIG plasma samples. Removal of antisuperantigen antibodies in IVIG by adsorption to SpeC- and GAS culture supernatant-coupled Sepharose markedly reduced the neutralizing ability of IVIG against respective stimuli. The neutralizing activity was totally recovered in the eluted antibodies. By contrast, although pre- and post-IVIG plasma samples contained antibodies to SpeA, these antibodies did not block the activity of this superantigen. Nonspecific immunomodulatory activity of IVIG was ruled out because neither the IVIG nor the affinity-purified antibodies significantly inhibited the response to the polyclonal T-cell mitogen phytohemagglutinin A. These data provide direct evidence that the neutralizing activity in IVIG, and in patient plasma samples following IVIG treatment is mediated by antibodies to superantigens and indicate that the quality rather than the quantity of these antibodies may be more clinically relevant.

Necrotizing fasciitis due to group A streptococci: a clinicopathological study of six patients

The recent worldwide appearance of invasive group A streptococcal infections has again called attention to streptococcal necrotizing fasciitis. However, in contrast to polymicrobial necrotizing fasciitis, the streptococcal form has not been thoroughly studied clinically. The objective of the study was to elucidate the characteristic features of recent cases of necrotizing fasciitis due exclusively to pure group A streptococci. We encountered six patients with these criteria at a single hospital in Japan during the last 12 years. A clinicopathological analysis was performed in these six patients. In three patients, the clinical signs and the laboratory findings were characteristic of systemic toxicity. In this group, the clinical presentation was a pale or blue-gray lesion associated with severe intravascular coagulation histologically involving the vessels in the lesion. In the three patients without signs of systemic toxicity, a swollen, erythematous skin lesion persisted for as long as one week; histologically, the intravascular coagulation within these lesions was mild. In clinicopathological terms, the entity in these six patients could be clearly classified as either fulminant or subacute. In the fulminant type, immediate surgical debridement of necrotic fascia is required; in the subacute type, incision and drainage alone are sufficient.

Necrotizing soft-tissue infections

Necrotizing soft-tissue infections may be rapidly fatal because of toxin-induced circulatory collapse. Because of the often nonspecific clinical presentation, prompt diagnosis may be difficult but is imperative as prompt treatment can be lifesaving. This article discusses necrotizing fasciitis and clostridial myonecrosis, and highlights pathogenesis, clinical presentation, diagnosis, and treatment.

Necrotizing group A streptococcal infections associated with streptococcal toxic shock syndrome

BACKGROUND

Group A streptococci (GAS) cause a variety of life-threatening infectious complications, including necrotizing fasciitis (NF), purpura fulminans (PF), and streptococcal toxic shock syndrome (strepTSS), in which bacteremia is associated with shock and organ failure.

METHODS

We reviewed our experience in the management of patients with necrotizing GAS infections from 1991 to 1995.

RESULTS

Eight adult patients (6 NF, 2 PF) were identified. Patients presented with fever, leukocytosis, and severe pain, and rapidly developed shock and organ dysfunction. The diagnosis of strepTSS was confirmed in 6 cases. A total of 54 surgical procedures were required, including widespread debridements and amputations. Two patients died (25%).

CONCLUSIONS

Recognition of the need for aggressive diagnosis and surgical treatment of this most rapidly progressive surgical infection is necessary for successful management.

Joseph Jones: infection with flesh eating bacteria

A Confederate Army surgeon, Joseph Jones, is generally credited to have provided the first modern description of necrotizing fasciitis, then known as hospital gangrene. This is a soft tissue infection characterized by a rapid and progressive course. In the 1990s, this entity has been popularized by the media as representing infection with "flesh eating bacteria." Certain patients are at particular risk to develop necrotizing soft tissue infections. Those with impaired immunity, diabetes mellitus, and intravenous drug abuse are particularly vulnerable, but these infections can also occur in previously healthy patients. Diagnostic radiographic testing is often helpful, including the use of plain radiographs, computed tomographic (CT) scan and magnetic resonance imaging (MRI). The most frequent infecting bacterial organism is Group A beta-hemolytic streptococcus, and there are indications to suggest that this organism may be acquiring greater virulence. Many infections, however, involve several bacterial pathogens. The keys to successful outcome are early diagnosis and surgical debridement. Fluid resuscitation and administration of broad spectrum antibiotics should be initiated as soon as the diagnosis is suspected.

Musculoskeletal complications of varicella

Varicella, commonly known as chickenpox, is a common viral infection in children. An estimated 3.5 million cases occur annually in the United States. Serious musculoskeletal complications such as osteomyelitis and necrotizing fasciitis, although uncommon, can be life and limb-threatening. The purpose of the current study was to determine the association between varicella and serious musculoskeletal complications necessitating operative treatment and to characterize these infections in otherwise healthy children. We retrospectively reviewed the records of all patients who had been admitted to the Children's Hospital in San Diego because of varicella and its complications during the eleven-year period from 1984 through 1994. All records with an inpatient discharge diagnosis code for varicella were identified. Twenty-seven (6 per cent) of the 417 admissions for varicella were for musculoskeletal complications of the disease necessitating operative treatment. There were seven admissions for osteomyelitis, four for septic arthritis, five for necrotizing fasciitis, ten for a deep-tissue abscess, and one for toxic shock syndrome leading to multiple limb amputations. Seventy-nine (19 per cent) of the 417 admissions occurred in 1994. Eleven (41 per cent) of the twenty-seven musculoskeletal complications that led to operative treatment occurred in 1994, representing a significant increase in the number of such complications compared with the numbers in previous years of the study (p < 0.01). Bacterial pathogens were identified as the cause of twenty-five of the twenty-seven complications that led to operative treatment. Of these twenty-five, twenty-one (84 per cent) were found, on culture, to be caused by group-A beta-hemolytic streptococcus. This pathogen was the cause of the infection in five of the seven patients who had osteomyelitis while Staphylococcus aureus was the cause in only one. Group-A beta-hemolytic streptococcus was also the causative organism in two of the four patients who had septic arthritis, three of the five who had necrotizing fasciitis, and all ten who had a deep-tissue abscess. Nine of the eleven musculoskeletal complications leading to operative treatment in 1994 had group-A beta-hemolytic streptococcus as the causative organism. An understanding of the trends of and a high level of suspicion for potentially serious secondary infections in children who have varicella is necessary for prompt recognition and appropriate treatment.

Hyaluronic acid capsule and the role of streptococcal entry into keratinocytes in invasive skin infection

It has been suggested that entry of pathogenic bacteria, including streptococci, into epithelial cells may represent an early stage of invasive infections. We found that poorly encapsulated wild-type strains and unencapsulated mutants of group A Streptococcus entered cultured human keratinocytes with high efficiency, while strains that produced large amounts of hyaluronic acid capsule did not, regardless of M-protein type or clinical source of the isolate. However, encapsulated streptococci produced extensive local necrosis and systemic infection in a mouse model of skin infection, while an isogenic acapsular strain did not. The results implicate the hyaluronic acid capsule as a virulence factor in soft tissue infection. Entry of poorly encapsulated group A Streptococcus into human epithelial cells does not appear to represent an initial step in invasive disease; rather, the capacity of encapsulated strains to avoid uptake by epithelial cells is associated with enhanced virulence in skin and soft tissue infection.

Children hospitalized for varicella: a prevaccine review

OBJECTIVES

To describe varicella complications in healthy and previously ill children hospitalized for varicella and to explore trends in group A beta-hemolytic streptococcus complications of varicella.

METHODS

A retrospective record review of children hospitalized for varicella between January 1, 1990, and March 31, 1994, was conducted in nine large acute care hospitals in Los Angeles County, California.

RESULTS

We identified 574 children hospitalized for varicella in study hospitals during the 4.25-year study period (estimated risk of hospitalization, approximately 1 in 550 cases of varicella); 53% of the children were healthy before the onset of varicella and 47% were previously ill with underlying cancers or other chronic illnesses. Children were hospitalized for treatment of complications (n = 427, 74%) or for prophylactic antiviral therapy or observation (n = 147, 26%). Systems involved in complications included skin/soft tissue (45%), neurologic (18%), respiratory (14%), gastrointestinal (10%), and hematologic, renal, or hepatic (8% or less). The mean age of children with skin/soft tissue infections was 2.7 years (range < 1 to 16 years) compared with 4.7 years (< 1 to 18 years) for other complications. Children with skin/soft tissue and neurologic complications were more often previously healthy (p < 0.05), whereas those with respiratory complications were more often previously ill (p < 0.001). Hospitalizations for skin/soft tissue infections increased during the study period. The proportion of complications as a result of group A beta-hemolytic streptococcus infection increased from 4.7% before 1993 to 12.2% for the remainder of the study period (p = 0.02).

CONCLUSIONS

Prior health status was predictive of the type of complications experienced by children with varicella requiring hospitalization. Our data suggest a recent increase in skin/soft tissue complications of varicella requiring hospitalization and an increase in the proportion of complications related to group A beta-hemolytic streptococcus. Wide-scale vaccine use should reverse this trend and reduce the overall impact of varicella on both healthy and previously ill children.

Toxic shock syndrome due to group C streptococci. A case report

BACKGROUND

Streptococcal toxic shock-like syndrome is a life-threatening illness which is on the increase. In early reports, only group A beta-hemolytic streptococcus was associated with the disease, but recent evidence indicates non-A streptococci groups are also involved.

OBSERVATIONS

We describe the first reported case of streptococcal toxic shock-like syndrome caused by a group C strain in Italy. Prior to the disease, the patient, a 46-year-old man, had been in good health and had only a 3-day history of sore throat, low grade fever, vomiting, diarrhea, and myalgia before admission. Initially, diagnosis was based only on clinical evidence: shock, multiorgan failure, profound hypothermia, and no apparent signs of infection. Toxic cardiomyopathy was also present.

RESULTS

Positive throat swab and blood culture confirmed a "definite case" following established criteria. Anamnesis showed a diagnosis of monoclonal gammopathy. Antibiotic treatment was begun immediately on admission of the patient, who was discharged 20 days later in good health.

CONCLUSIONS

This case illustrates how an early diagnosis and prompt antibiotic therapy can determine a more favorable outcome.

Advances in medical and antibiotic management of infective endocarditis

Infective endocarditis remains a serious medical problem despite advancements in laboratory detection, echocardiographic techniques, and newer antibiotic agents. This article summarizes the microbial agents in infective endocarditis, in addition to developments in medical and antibiotic management.

Insertional inactivation of Streptococcus pyogenes sod suggests that prtF is regulated in response to a superoxide signal

In establishing an infection, Streptococcus pyogenes has the capacity to bind to the host extracellular matrix protein fibronectin via its protein F adhesin. Previous studies have suggested that the expression of protein F is stimulated during aerobic growth or upon addition of superoxide-generating agents to the culture under O2-limited conditions. To further explore the role of superoxide, we have examined the transcription of the gene which encodes protein F (prtF), as well as the expression of superoxide dismutase (SOD) under conditions which promote or repress protein F expression. These studies show that prtF transcription is regulated in response to superoxide concentration and that SOD is regulated in different environments in a manner which directly parallels the expression of protein F. A mutant deficient in SOD activity was constructed by insertional mutation into the gene which encodes SOD (sod). The resulting mutant was sensitive to superoxide and aerobic conditions, showed hypersensitive induction of prtF in response to superoxide, and expressed prtF under normally unfavorable O2-limited conditions. These findings suggest that a streptococcal signal transduction system which senses superoxide may coordinately control expression of prtF and sod.

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.

Identification of isp, a locus encoding an immunogenic secreted protein conserved among group A streptococci

The protein Mga (mga), which is required for transcription of several virulence genes of group A streptococci (GAS), including the antiphagocytic M protein, was suggested to act as the response regulator element of a bacterial two-component pathway. To investigate whether a gene encoding a cognate sensor protein is located upstream of mga, 3.1 kb of DNA 5' of the mga translational start site was cloned from serotype M6 GAS strain JRS4. Sequence analysis of this region revealed two adjacent open reading frames, a previously described orf and a new locus, isp (immunogenic secreted protein), which could encode proteins of 9 and 59 kDa, respectively. Inactivation of either open reading frame had no significant effect on transcription of the gene encoding M protein (emm) under normal growth conditions, suggesting that neither isp nor orf is involved in the Mga regulatory circuit. A protein migrating at an apparent molecular weight of 65,000 was produced when isp was transcribed and translated in vitro. The predicted isp product (Isp) contains an amino-terminal signal sequence region homologous to that found in bacterial secreted proteins, and expression of isp in Escherichia coli resulted in the presence of Isp in the periplasmic fraction. Convalescent-phase serum from a patient with an active GAS infection recognized forms of Isp both from the periplasm of E. coli and the supernatant of a GAS strain. Both isp and orf are highly conserved among strains of GAS, as shown by hybridization analyses.

Susceptibility of macrolide and beta-lactam antibiotics of Streptococcus pyogenes strains isolated over a four-year period in central Italy

In vitro susceptibility to erythromycin, azithromycin, penicillin G, ceftriaxone and ceftibuten was investigated in 190 Streptococcus pyogenes strains isolated over a 4-year period (1991-1994) from patients attending a university hospital located in central Italy. The rate of susceptibility to macrolide antibiotics of the S. pyogenes strains showed a progressive decrease (from 90.3% in 1991 to 79.5% in 1994), while all strains were susceptible to the three beta-lactam antibiotics. Owing to the reduced prevalence of macrolide-susceptible S. pyogenes strains, in vitro susceptibility testing of streptococcal isolates appears to be always necessary before starting a macrolide-based chemotherapy. Concerning beta-lactams, ceftriaxone presented minimum inhibitory concentrations (MIC) always equal to or lower than those of penicillin G, while the oral long-acting cephalosporin, ceftibuten, had MICs higher than those of the other beta-lactams, although in the susceptible range. Results of in vitro susceptibility testing are discussed in relation to their implications for antimicrobial chemotherapy of S. pyogenes infections.