Group A streptococcal infections and acute rheumatic fever

Inhibition of human peripheral blood mononuclear cell proliferation by Streptococcus pyogenes cell extract is associated with arginine deiminase activity

Streptococcus pyogenes (group A Streptococcus) cell extracts (CE) have a remarkably powerful and dose-dependent inhibitory effect on antigen, superantigen, or mitogen-stimulated human peripheral blood mononuclear cell (PBMC) proliferation in vitro. Purification of the inhibitory component present in S. pyogenes type M5 (Manfredo strain) CE by anion-exchange chromatography followed by gel filtration chromatography showed that the inhibitor had an approximate native molecular mass of 100 kDa. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified inhibitory fractions followed by silver staining gave a single band with an approximate molecular mass of 47 kDa, indicating that the inhibitor is composed of two identical subunits. NH2-terminal sequencing of the protein revealed that it was identical to the previously characterized streptococcal acid glycoprotein (SAGP); this protein possesses between 31.5 and 39.0% amino acid identity with arginine deiminase (AD) from Mycoplasma hominis, Mycoplasma arginini, Pseudomonas putida, and Pseudomonas aeruginosa. AD enzyme activity was present in unfractionated CE prepared from a range of streptococcal strains, and partially purified inhibitory fractions of Manfredo CE also had high levels of activity. The inhibitory effect of Manfredo CE was overcome by the addition of L-arginine to proliferation assays in which human PBMC were stimulated with phytohemagglutinin. We conclude that SAGP, or its homolog, possesses AD activity and that the potent inhibition of proliferation of human T cells by streptococcal CE is due to activity of this enzyme.

Increasing incidence of streptococcal impetigo in atopic dermatitis

Streptococcal impetigo associated with atopic dermatitis has dramatically increased from 1989 to 1994 in outpatients visiting our hospital, totalling 174 cases. The most frequent causative agents were group A streptococci (Streptococcus pyogenes, 70.7%) followed by group G (19.5%) and group B (9.8%). Streptococcus was isolated singly in 28.2% of cases and in concomitant with Staphylococcus aureus (S. aureus) in 71.8%. Major clinical features of streptococcal impetigo, especially caused by group A streptococci, were non-bullous pustules with thick crusted ceiling. Impetigo caused by group G or B streptococci generally formed smaller sized pustules of fewer numbers. Impetigo was usually present, associated with severe eczematous lesions. Various degrees of fever were noticed in 32.8% (group A, 39.8%; group G, 17.6%; group B, 11.8%) during active stages. The lesions on the face often resembled Kaposi's varicelliform eruption in any group. Systemic antimicrobial agents were administered in 71.3% of cases and the remainder were treated with topical antibiotics (oxytetracycline hydrochloride) or disinfectants (povidone-iodine). Recurrence occurred within a month in 38.0% of cases treated with topical agents only and in 17.7% treated with systemic antimicrobial agents. Antimicrobial susceptibility tests and the results of treatment seem to indicate that cephems, as well as penicillins, are the first choice of treatment for streptococcal impetigo.

Group A streptococcal Vir types are M-protein gene (emm) sequence type specific

The M-protein genes (emm genes) of 103 separate impetiginous Streptococcus pyogenes isolates were sequenced and the sequence types were compared to the types obtained by Vir typing. Vir typing is based on restriction fragment length polymorphism (RFLP) analysis of a 4- to 7-kb pathogenicity island encoding emm and other virulence genes. By using both HaeIII and HinfI to generate RFLP profiles, complete concordance between Vir type and emm sequence type was found. Comparison of the emm sequences with those in GenBank revealed new sequence types sharing less than 90% identity with known types. Diversity in the emm sequence was generated by corrected frameshift mutations, point mutations, and small in-frame mutations.

Streptococcal toxic shock syndrome presenting as suspected child abuse

Natural disease processes can predispose individuals to develop external body lesions that mimic traumatic injury. This can be particularly problematic in pediatric cases in which clinicians are alerted to the problems of child abuse. Streptococcal toxic shock syndrome is a systemic infectious illness that can manifest itself with erythematous and necrotizing skin lesions. We report a fatal case of streptococcal toxic shock syndrome in a 4-year-old girl who presented with skin lesions that were initially thought to be traumatic in origin. A report of possible child abuse was filed with the state. Based on the morphologic findings and bacteriologic culture results at autopsy, these lesions and the cause of death in this case were instead determined to result from streptococcal toxic shock syndrome.

Molecular epidemiology of Streptococcus pyogenes in an area where acute pharyngotonsillitis is endemic

During an open clinical trial in an area where streptococcal infections are hyperendemic, we studied the genetic polymorphism of Streptococcus pyogenes isolates collected from patients and from healthy carriers living in close contact with them. The clonal diversity of isolates was analyzed by pulsed-field gel electrophoresis with three restriction enzymes (SmaI, ApaI, and SacII). The pharynx of each patient and healthy carrier was colonized by a single clone, suggesting the clonal nature of streptococcal colonization in individuals. Among 52 isolates obtained from patients with acute pharyngotonsillitis, we found 14 genetically unrelated clones, showing the genetic diversity of S. pyogenes. However, two clones belonging to the M1 and M12 serotypes represented about 70% of isolates in carriers and patients. Pharyngeal colonization in cured patients was monitored for 3 to 4 months. After the initial elimination of S. pyogenes following antibiotic therapy, the rate of recolonization was high by day 30 (about 20%) and was also at that level between days 90 and 120; this was similar to the carriage rate in family contacts. Thus, cured patients can be recontaminated by unrelated clones, suggesting that colonization of healthy carriers might be a potential source of spread and redistribution of S. pyogenes isolates.

Acute rheumatic fever. Still a challenge

At the end of the 20th century, after an apparent decline, acute rheumatic fever (ARF) now constitutes a great challenge for developed and developing countries. It is caused by a group A beta-hemolytic Streptococcus upper airways infection, but the exact pathogenetic mechanisms are not yet clear. The role of the immune system in the pathogenesis of ARF is understood better than genetic host factors. ARF can mimic many other diseases, and the diagnosis is based on clinical criteria. It is still overdiagnosed and underdiagnosed in different settings. Penicillin has greatly contributed to the reduction in the incidence and recurrence of this disease. Current schemes of prophylaxis, however, present many problems, and failures are common. Future efforts to reduce the burden of this disease should induce public health measures the vaccine strategies.

Erythromycin resistance of group A streptococci from throat samples is related to age

BACKGROUND

Factors associated to increased antimicrobial resistance among bacterial pathogens have been widely discussed and need to be evaluated. In Finland resistance to erythromycin in group A streptococci has become an important problem among outpatients. The aim of this study was to investigate whether occurrence of erythromycin resistance among group A streptococci isolated from noninvasive infections correlates with the patients' age and sex.

METHODS

Group A streptococci isolated from 10 162 patients were tested for erythromycin resistance in 21 regional microbiologic laboratories located throughout Finland. The age of every patient and the sex of 8121 (80%) patients were known. The statistical significance of the association between the patients' age or sex and the occurrence of erythromycin resistance in group A streptococci, isolated from throat swab samples (8568 isolates) or pus samples (1594 isolates), was measured by logistic regression analysis.

RESULTS

When erythromycin resistance of the isolates was regressed with the patients' age and sex, the age of the patient was a clearly significant predictor for the throat isolates (beta coefficient = -0.0114, SD 0.0029, observed value of t test statistic = -3.89, P = 0.0001) but not for the pus isolates. The odds ratio for age was 0.99 with a 95% confidence interval of 0.98 to 0.99. Thus the expected risk of erythromycin resistance on a group A streptococcal throat isolate decreased with increasing age by 1% per year. No significant association between the patients' sex and the occurrence of erythromycin resistance was found.

CONCLUSIONS

Significant differences may exist between different age groups in the frequency of antibiotic-resistant isolates among outpatients, perhaps caused by differences in antibiotic prescribing. Thus overall resistance levels do not necessarily represent all age groups, especially children.

Mitogenic factor secreted by Streptococcus pyogenes is a heat-stable nuclease requiring His122 for activity

The gene encoding a mitogenic factor, termed MF, was cloned from Streptococcus pyogenes and the recombinant MF was overexpressed in Escherichia coli. Both the natural and recombinant MF had heat-resistant nuclease activity. The nuclease activity of MF was characterized using the recombinant protein. MF showed endonuclease activity, digesting ssDNA, dsDNA and tRNA. The optimal pH for the DNase activity of MF was 9.5. The DNase activity was enhanced approximately tenfold by the simultaneous presence of two divalent cations, Mg2+ and Ca2+, compared to either alone and was inhibited by EDTA or NaCl. The heat stability of MF was biphasic; the DNase activity was heat-stable from 0 to 50 degrees C over 80 degrees C but very unstable at around 60 degrees C. DNA digested by MF possessed 5'-phosphorylated and 3'-hydroxylated termini, identical to those obtained by digestion of DNA by pancreatic deoxyribonuclease I. A mutant clone revealed that His122 was a residue essential to the nuclease activity.

Five-Day Spiramycin vs Seven-Day Penicillin V in the Treatment of Streptococcal Tonsillitis in Children

Because of the frequency of penicillin allergies in children receiving β-lactam antibacterial agents, the macrolides are frequently chosen as alternatives in patients with group A β-haemolytic streptococcal (GABHS) infections. Spiramycin, amacrolide widely used in paediatrics, achieving remarkably high tonsillar tissue concentrations, was evaluated in this study in comparison with penicillin V (Phenoxymethylpenicillin). 298 children aged 1.5 to 14 years with acute tonsillitis and a positive rapid antigen test for GABHS were randomised to receive either a 5-day course of spiramycin 100 000 IU/kg twice daily or a 7-day course of penicillin V 25 000 IU/kg 3 times daily. Clinical and bacteriological assessments were recorded at inclusion (day 1), at the end of the treatment visit (days 8 to 12), and at the follow-up visit (days 25 to 35). GABHS isolated during the study were analysed by total DNA restriction fragment length polymorphism analysis. Of the 237 children with a positive GABHS culture at day 1,210 (88.6%) were evaluable for complete clinical and bacteriological efficacy at the end of treatment. Clinical efficacy was evident in 96.1% (98 of 102) for spiramycin and in 98.1% (106 of 108) for penicillin V. Bacteriological eradication was achieved in 79.4% (81 of 102) for spiramycin and in 89.8% (97 of 108) for penicillin V. Three failures occurred in the spiramycin group. In intent-to-treat analysis, the success rate (clinical cure and bacteriological eradication) for spiramycin was 77.9% (116 of 149) and that for penicillin V was 83.9% (125 of 149). At the follow-up visit, 182 children were evaluable for efficacy. Clinical cure with or without asymptomatic carriage of GABHS was observed in 97.7% (86 of 88) for spiramycin and in 89.4% (89 of 94) for penicillin V. Three relapses and 1 reinfection occurred in the penicillin V group. Adverse events, mainly gastrointestinal, occurred in 10.7% of spiramycin patients versus 12.8% of penicillin V patients. These results show that a 5-day treatment regimen with spiramycin twice daily is effective and well tolerated in GABHS tonsillitis, and is an alternative to penicillin V when necessary in children.

Non-group A streptococci: are they pathogens in the throat?

A total of 3,184 paediatric patients with sporadic pharyngitis was studied at King Khalid University Hospital in Riyadh, Saudi Arabia. In addition, 478 children without pharyngitis who were matched for age and sex were included as controls. Group A beta-haemolytic streptococci (beta HS) were detected significantly more often among the children with pharyngitis than among the controls (8.4% vs 2.3%; p < 0.0001). In contrast, total non-group A and group C beta HS were isolated at lower frequency from the sick than control children (0.9% vs 2.5% and 0.2% vs 1.2% respectively; p < 0.01) while other non-group A beta HS such as groups B, G and F were each isolated in similar frequency from both the sick and control children. We conclude that non-group A beta HS appear not to be as important as aetiological agents of sporadic pharyngitis in these children.

Preferential recognition of human myocardial antigens by T lymphocytes from rheumatic heart disease patients

Acute rheumatic fever (ARF) and rheumatic heart disease (RHD) are autoimmune sequelae of upper respiratory infections with group A streptococci (GAS). To gain a better understanding of the pathogenesis of these diseases, we examined the in vitro proliferative responses of peripheral blood mononuclear cells (PBMC) from RHD patients to human myocardial proteins in a T-cell Western assay. A number of myocardial proteins fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis were recognized by PBMC from both patients and controls. However, PBMC from a significant percentage of RHD patients (40%) responded to a discrete band of myocardial proteins migrating with an apparent molecular mass of 50 to 54 kDa while none of the control subject PBMC responded to this protein band (P < or = 0.0001). To further investigate the link between infections with GAS and autoimmune carditis, we studied the proliferative responses of PBMC from patients and controls to myocardial proteins before and after in vitro stimulation of the cells with opsonized GAS isolated from ARF patients. Priming of PBMC with rheumatogenic GAS caused the percentage of RHD patients responding to the 50- to 54-kDa myocardial proteins to increase from 43 to 90% (P < or = 0.0284). By contrast, PBMC from control subjects failed to recognize the 50- to 54-kDa myocardial proteins even after stimulation with the opsonized streptococci (P < or = 0.0001). The assay sensitivity was increased from 40 to 90% after priming of a patient's cells with opsonized GAS, but the positive predictive value was 100% in both unprimed and primed cultures. Antibodies generated to partially purified 50- to 54-kDa myocardial proteins did not cross-react with either streptococcal homogenates, purified M protein, myosin, laminin, or vimentin, suggesting a lack of cross-reactivity at the humoral level. This study suggests that the 50- to 54-kDa myocardial proteins contain a putative antigen that is preferentially recognized by T cells from RHD patients and demonstrates that exposure to streptococcal antigens enhances the ability of patients to recognize these proteins.

Coiled-coil structure of group A streptococcal M proteins. Different temperature stability of class A and C proteins by hydrophobic-nonhydrophobic amino acid substitutions at heptad positions a and d

M proteins and M-like proteins, expressed on the surface of group A streptococci and binding to human plasma proteins, can be divided into two classes, A and C, depending on the structure of the central repeated regions. The class C proteins have been shown to be dimers with a coiled-coil structure. In this work, we have compared the structure and binding of a class A protein, Mrp4, and a class C protein, Arp4, expressed by the same bacterial strain. Circular dichroism spectra, gel filtration, and binding assays showed that both proteins had a coiled-coil dimer configuration and a high-affinity binding at 20 degrees C. However, striking differences were seen at 37 degrees C. The class A protein, Mrp4, was still a coiled-coil dimer with high affinity binding activity, whereas the class C protein, Arp4, had lost both the coiled-coil structure and binding activity. Raising the temperature even higher, Mrp4 retained the coiled-coil structure up to 70-90 degrees C. Furthermore, a recombinant protein, Mrp(C), in which the A-repeats of Mrp4 were replaced by the C-repeats of Arp4, lost its coiled-coil structure and fibrinogen-binding around 40-45 degrees C. These results suggest a high thermal stability of class A proteins and a low stability of class C proteins and that the structural basis for this can be found partly in the A- and C-repeats. Analysis of the amino acid sequences of the A- and C-repeats, revealed a large difference, 87% and 45%, respectively, in the content of hydrophobic amino acid residues in the positions regarded as important for the formation of the coiled-coil structure. In particular, several alanine residues in the A-repeats were replaced by serine residues in the C-repeats. Our results suggest that important structural and functional changes within the M protein family have evolved by specific hydrophobic-nonhydrophobic amino acid replacements.

Immunologic and clinical correlations in rheumatic fever and rheumatic heart disease

The intimate relationship of Streptococcus pyogenes and rheumatic fever is well-established, but the precise pathogenesis of rheumatic fever and rheumatic heart disease continues to elude intense investigative efforts by students of the disease worldwide. Technologic advances in molecular biology, not thought possible two decades ago, have given additional insight into the immunologic aspects of the disease. On the clinical side echocardiography has proved to be a marvelous, non-invasive technique to evaluate cardiac anatomy and function. We are now able to gain a closer correlation of the clinical presentation and the autoimmune response. The increased understanding acquired both from the "bench" and the "bedside" are making this perplexing disease somewhat less mysterious. We seem tantalizingly close to grasping a complete understanding of the pathogenesis of rheumatic fever and rheumatic heart disease.

The fibronectin-binding protein of Streptococcus pyogenes, SfbI, is involved in the internalization of group A streptococci by epithelial cells

Streptococcus pyogenes organisms (group A streptococci) are considered to be highly adhesive extracellular pathogens. However, it has recently been reported that S. pyogenes has the capacity to efficiently invade eukaryotic cells. In this study, we demonstrate that the interaction of S. pyogenes fibronectin-binding protein (SfbI) with fibronectin on nonphagocytic HEp-2 cells triggers bacterial internalization. Blocking of the SfbI adhesin by either antibodies against the whole protein or antibodies against the fibronectin-binding domains of SfbI, as well as pretreatment of HEp-2 cells with purified SfbI protein, prevents both S. pyogenes attachment and internalization. Inert latex beads precoated with the purified SfbI protein are ingested by eukaryotic cells, demonstrating that SfbI is per se enough to trigger the internalization process. Experiments performed with a recombinant SfbI domain encompassing the two fibronectin-binding regions of the SfbI molecule demonstrated that these binding regions are essential and sufficient to activate uptake by HEp-2 cells. These results demonstrate that the fibronectin-binding protein SfbI is involved in both S. pyogenes' attachment to and ingestion by HEp-2 cells and contribute to elucidation of the underlying molecular events leading to eukaryotic cell invasion by S. pyogenes.

Group A streptococcal bacteraemia: experience at a university hospital in Riyadh

A recent increase in the frequency and severity of group A beta-haemolytic streptococcal (GABHS) infections has been reported from several parts of the world. A retrospective analysis of bacteraemic GABHS infections encountered at a major teaching hospital in Riyadh, Saudi Arabia between 1982 and 1993 was performed. The epidemiologic, clinical and laboratory aspects of 29 episodes of GABHS bacteraemia were reviewed, and the differences between frequency and severity of these episodes were compared between the initial (1982-1989) and the late (1990-1993) periods of the study. The overall frequency of GABHS bacteraemia was 0.14 episodes per 1000 admissions with no difference between the initial and the late periods. Seventeen patients were adults and 12 were paediatrics. Adults were mostly females (82%) and paediatrics were predominantly males (75%). Seven episodes (24%) were nosocomial. Most patients (72%) had a predisposing factor for GABHS infections. Primary bacteraemia occurred in 13 patients (45%); and the skin and throat were the major sources of the bacteraemia in the rest of the patients. Shock complicated five episodes (17%) and acute renal failure developed in six (21%) patients. The overall case fatality rate was 21%. All five episodes complicated by shock were in the late period, and the rate of acute renal failure as well as the case fatality rate have doubled in the late vs. the early periods. Although no recent increase in frequency of GABHS bacteraemia was found, invasive GABH infections may have become more severe.

Analysis of human T cell responses to group A streptococci using fractionated Streptococcus pyogenes proteins

Cell extract and spent culture supernatant proteins from Streptococcus pyogenes Manfredo strain (type M5) were each separated to give 22 narrow range molecular weight fractions by blot-elution from SDS-polyacrylamide gels. Eluted samples and unfractionated proteins were screened for T cell stimulatory activity using human peripheral blood mononuclear cells (PBMC) from healthy adults in proliferation assays. Responses were measured in 4- and 7d cultures. Responses to a wide range of cell extract proteins were revealed by fractionation, the degree of response to each fraction varying between donors. Unfractionated culture supernatant proteins elicited proliferative responses by PBMC from all individuals examined. Responses to culture supernatant fractions containing 25-33 kDa proteins could be attributed to known superantigens. Furthermore, samples from culture supernatants containing higher molecular weight fractions (> 45 kDa) elicited responses in 50% of donors in 7d cultures, suggesting that these fractions contained common recall antigens. The efficacy of using electroeluted samples to identify T lymphocyte stimulatory proteins was confirmed by demonstrating that a known superantigen of S. pyogenes Manfredo strain, streptococcal pyrogenic exotoxin C (SPEC), could be fractionated successfully using this method and its activity recovered. Our results show that human T cell responses to group A streptococci involve a remarkably wide range of both cell-associated and released streptococcal proteins.

Use of Tn917 to generate insertion mutations in the group A streptococcus

The Enterococcus faecalis transposon Tn917 is functional in a broad range of bacteria, including both Gram-positive and Gram-negative species. We cloned Tn917-LTV3, a derivative carrying a promoterless lacZ (beta-galactosidase gene), into the thermosensitive shuttle replicon pG+host4 and assayed for chromosomal insertions in group A streptococcus (GAS). Tn917 transposed into the GAS chromosome at a frequency of (2.8 +/- 3.2) x 10(-5) per colony forming unit (cfu). Transposition products were predominantly simple insertions and no target site preference was detectable. Some transcriptional fusions were identified in which the promoterless lacZ of the transposon appeared to be expressed from an external promoter.

Susceptibility of Streptococcus pyogenes from throat cultures to macrolide antibiotics and influence of collection criteria

OBJECTIVE: To assess the incidence of resistance to erythromycin and to the three other macrolide antibiotics most extensively used in Italy (azithromycin, clarithromycin and roxithromycin) among clinical strains of Streptococcus pyogenes freshly isolated from throat cultures of pediatric patients in an area of Central Italy. METHODS: Two sets of isolates were examined. The strains of the first set (n=100) were collected according to a protocol admitting only throat swabs from untreated patients with symptoms of acute pharyngotonsillitis. The second set (n=180) consisted of strains isolated from throat cultures during the routine activity of diagnostic laboratories, no particular protocol being applied. RESULTS: A trimodal distribution of strains was observed in relation to their macrolide susceptibility levels: two clusters were constituted by highly susceptible and highly resistant strains, respectively; a third, middle cluster consisted of strains displaying low-level resistance (or even intermediate susceptibility, in a minority of isolates, to clarithromycin). The distribution of individual isolates in the three modal clusters was the same with all four drugs. Both MIC ranges and MIC50s almost overlapped in the isolates of the two sets, whereas MIC90s were far higher in the strains of the second set (4 micro g/mL for clarithromycin, 8 micro g/mL for erythromycin and azythromycin, and 16 micro g/mL for roxithromycin) than in those of the first (0.125 micro g/mL for all four drugs). Resistant strains were 5% among the isolates of the first set and three times as many among those of the second. CONCLUSIONS: The lower incidence of macrolide resistance recorded in the first set is probably more reliable: the threefold incidence observed in the second set may be overestimated due to the lower frequency of strains involved in drug-responsive infections and to the increased occurrence of strains from unsuccessfully treated patients.

Septic shock

PURPOSE

Many patients with sepsis require surgery for their management, often on an urgent or emergency basis. Anaesthetists are commonly required to manage patients with sepsis and septic shock in the operating room, past anaesthesia recovery area, and the intensive care unit. Since little has been written in the Anaesthesia literature on sepsis and septic shock, a review of this topic was considered appropriate.

SOURCE

References were obtained from computerized searches on the National Library of Medicine (English language), recent review articles and personal files. PRINCIPLES FINDINGS: Septic shock is a common cause of morbidity and mortality. Its presentation may be subtle or catastrophic. Successful management depends on an understanding of the pathophysiology of the syndrome, allowing rapid, appropriate resuscitation. This often requires aggressive correction of volume deficit, maintenance of adequate perfusion pressure with inotropic and vasopressor therapy, mechanical ventilation and correction of coagulopathy. Appropriate cultures must be taken and antibiotic therapy started, often empirically. Anaesthetic management should include careful haemodynamic monitoring. Anaesthesia induction and maintenance must be tailored to the haemodynamically unstable patient.

CONCLUSIONS

The management of the septic patient in the perioperative period presents a challenge for the anaesthetist. Haemodynamic and respiratory instability should be anticipated. Management requires multisystem intervention and careful anesthetic management.

Antigenic epitope mapping of the M24 protein of Streptococcus pyogenes: implications for serodiagnosis of rheumatic fever

Rheumatic fever continues to be a significant problem in Australian Aboriginal communities and developing countries worldwide. Early diagnosis could facilitate the institution of penicillin prophylaxis resulting in the prevention of recurrences of rheumatic fever. An overlapping biotinylated peptide bank of 82 peptides, based on the known sequence of Streptococcus pyogenes M24 protein, was used in a standard enzyme immunoassay. A total of 82 sera were tested from both aboriginal and non-aboriginal subjects with clinically proven rheumatic fever, rheumatic heart disease and matched controls. Two peptides with significant sequence homology at the C-terminal end were found to be discriminatory between aboriginal cases and controls. It is proposed that these peptides could be the basis of a serological test for rheumatic fever.

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.

Pharyngitis

This article reviews the commonly encountered agents causing acute inflammation of the pharynx and tonsils, with special attention to a practical approach for identifying and dealing with the group A beta-hemolytic streptococcus. Ubiquitous viral agents such as Epstein-Barr virus, rhinovirus, and adenovirus are reviewed. Some agents such as group A beta-hemolytic streptococcus and Epstein-Barr virus are susceptible to treatment. Additionally, unusual infectious agents and noninfectious causes of pharyngitis are enumerated.

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.

Definition of the mitogenic factor (MF) as a novel streptococcal superantigen that is different from streptococcal pyrogenic exotoxins A, B, and C

Human T cell activation by recombinant mitogenic factor (rMF) was investigated in comparison with that by recombinant streptococcal pyrogenic exotoxins (rSPE) A, B, and C. Recombinant MF, rSPEA, and rSPEC were mitogenic for peripheral blood mononuclear cells (PBMC), whereas rSPEB was not. Recombinant MF required only HLA-DR for the stimulation of PBMC, as determined using monoclonal antibodies (mAb) to HLA class II molecules and the mouse L cells transfected with HLA class II molecules. Recombinant SPEA and rSPEC required HLA-DR or HLA-DQ molecule. Recombinant MF selectively stimulated V beta 2, V beta 7, V beta 8, V beta 18 and V beta 21-bearing T cells, whereas rSPEA and rSPEC activated V beta 2 and V beta 6-bearing T cells as evaluated by the quantitative T cell receptor (TCR) analytical method. No clonality was observed in the nucleotide sequences of complementarity determining region 3 of TCR V beta in T cells responding to rMF. The profiles of cytokine production by PBMC in response to rMF, rSPEA, and rSPEC were quite similar. In summary, these results demonstrate that both HLA class II molecules and the TCR V beta required for rMF-mediated T cell activation are distinct from those required for rSPEA or rSPEC-mediated activation. Therefore, the MF is a novel streptococcal super-antigen which is different from SPEA, SPEB, and SPEC.

Streptococcal diagnostic testing and antibiotics prescribed for pediatric tonsillopharyngitis

BACKGROUND

This study examined a 1-year cross-sectional sample of Kentucky Medicaid claims for the use of streptococcal diagnostic tests for pediatric tonsillopharyngitis and the empiric use of antibiotics.

METHODS

Subjects were individuals older than 3 and younger than 18 years old seen in an ambulatory setting for tonsillopharyngitis; 3478 individuals accounted for the 5067 separate outpatient and emergency room encounters for pediatric tonsillopharyngitis; 849 encounters coded as streptococcal sore throat were also examined.

RESULTS

Diagnostic tests for group A streptococcal tonsillopharyngitis were performed in only 22% (n = 1130) of the tonsillopharyngitis encounters and 36% (n = 306) of the streptococcal sore throat encounters. Urban physicians were more likely than rural physicians to use a diagnostic test (P = 0.0001). Emergency room encounters and outpatient encounters were not significantly different in the likelihood of having a diagnostic test (P = 0.16). In encounters for tonsillopharyngitis antibiotics were prescribed in 72% of the total encounters and in 73% of the encounters without a diagnostic streptococcal test. In encounters for streptococcal sore throat, antibiotics were prescribed for 68% of the total encounters and 69% of the encounters without a diagnostic streptococcal test.

CONCLUSIONS

Current practices in the Kentucky Medicaid program do not follow the American Academy of Pediatrics guidelines for streptococcal tonsillopharyngitis.

The frequency of resistance to erythromycin in group A streptococci in Ankara

The frequency of resistance to erythromycin of group A beta-haemolytic streptococci in the last 7 years was determined in three medical centres in Ankara. While all group A beta-haemolytic streptococci strains were susceptible to penicillin, a gradual increase in resistance to erythromycin until 1992 was observed. However, a substantial increase in erythromycin resistance occurred in 1993 when newer macrolides became available and were widely used in the latter part of 1992.

CONCLUSION

The data show that frequent testing for resistance to erythromycin of group A beta-haemolytic streptococci is required for the use of this antibiotic in our country.

Biventricular assist for severe acute rheumatic pancarditis

Severe heart failure in acute rheumatic myocarditis is rare. It may be rapidly reversible with treatment, so maximal medical treatment and, if necessary, mechanical support should be given before heart transplantation is considered.

Iron starvation causes release from the group A streptococcus of the ADP-ribosylating protein called plasmin receptor or surface glyceraldehyde-3-phosphate-dehydrogenase

In many pathogenic bacteria, iron starvation serves as an environmental signal that triggers the expression of virulence factors, many of which are found on the cell surface or secreted into the culture supernatant. Using the chelating agent nitrilotriacetic acid, we have established conditions for iron starvation of the important human pathogen Streptococcus pyogenes (the group A streptococcus) and determined that iron limitation results in the specific appearance of several new proteins in the culture supernatant. One of these supernatant proteins is the ADP-ribosylating protein known as streptococcal plasmin receptor (Plr) or as the streptococcal surface glyceraldehyde-3-phosphate-dehydrogenase because of its other activities. Upon iron starvation, Plr is specifically released into the culture supernatant in a time-dependent manner, and its appearance in the supernatant is not accompanied by induction of plr mRNA synthesis. Release of Plr from the bacteria may be important for the virulence of group A streptococci and the manifestation of diseases.

Outbreak of acute glomerulonephritis in children: observed association with the T1 subtype of group A streptococcal infection in northern Kyushu, Japan

Group A streptococcal infection is associated with the occurrence of acute glomerulonephritis (AGN) and rheumatic fever (RF). A surveillance study in the Saga area, in northern Kyushu, Japan, showed a small variation in the reported number of group A streptococcal infections in the period 1988-94. However, of the AGN cases reported in this period, more than half were observed in 1992. In order to examine whether some change had occurred in the serotype distribution of Streptococcus pyogenes during the period, patients in the Saga area diagnosed as having group A streptococcal infection and patients with AGN or RF were analyzed. Serological T-typing of S. pyogenes was carried out for patients with group A streptococcal infections, and the association between the occurrence of AGN or RF and the distribution of each different T subtype was analyzed. M-typing of S. pyogenes was also carried out and the correlation between T and M types was examined. From 1988 to 1994, the annual number of patients with group A streptococcal infections in the Saga area showed a small variation, range 65-100 patients/year. Of the 42 patients with AGN and three with RF observed in this period, 27 with AGN (64%) and one with RF (33.3%) were detected in 1992. Only the T1 subtype increased in 1992; the other T subtypes showed little variation in incidence. The number of patients with the T1 subtype was significantly correlated with the occurrence of AGN by regression analysis (P < 0.01). Of the 170 subjects tested for both T and M subtypes, 44 of the 45 T1-typed subjects had the M1 protein. Our epidemiological study suggested that the T1 subtype of streptococcal infection was associated with an outbreak of AGN in 1992 in the Saga area.

Analysis of the superantigenic activity of mutant and allelic forms of streptococcal pyrogenic exotoxin A

Infections with Streptococcus pyogenes (group A streptococcus) can result in the recently described streptococcal toxic shock syndrome (STSS), which is characterized by rashes, hypotension, multiorgan failure, and a high mortality rate. S. pyogenes isolates associated with STSS usually produce streptococcal pyrogenic exotoxin A (SpeA), a bacterial superantigen capable of stimulating host immune cells. Most of the symptoms of STSS are believed to result from cytokine release by the stimulated cells. To better understand the pathogenesis of STSS, we began studies on the SpeA-immune cell interaction. We generated 20 mutant forms of SpeA1 (SpeA encoded by allele 1), and the mutant toxins were analyzed for mitogenic stimulation of human peripheral blood mononuclear cells, affinity for class II major histocompatibility complex molecules (DQ), and disulfide bond formation. Residues necessary for each of these functions were identified. There are four alleles of speA, and STSS strains usually contain either allele 2 or allele 3. The product of allele 2, SpeA2, had slightly higher affinity for the class II MHC molecule compared with SpeA1 but not significantly greater mitogenic activity. SpeA3, however, was significantly increased in mitogenic activity and affinity for class II MHC compared with SpeA1. Thus, we have evidence that the toxin encoded by some of the highly virulent S. pyogenes STSS-associated isolates is a more active form of SpeA.

Penicillin tolerance and treatment failure in group A streptococcal pharyngotonsillitis

Failure of treatment of group A streptococcal pharyngitis and tonsillitis is well documented. One of the possible explanations for treatment failure is penicillin tolerance in group A streptococci. Reports on the prevalence of penicillin tolerance among group A streptococci (0-100%) and the presumed relationship with therapeutic failure vary considerably. Therefore, it appears worthwhile to review pharyngotonsillitis studies, devoting special attention to the variables of MIC-MBC laboratory determinations such as inoculum preparation, composition and volume of test medium, and the criteria used to define penicillin tolerance. Alternative methods (gradient-replica plate method, beta-lactamase disk test, time-kill assay, and cell-lysis assay) are discussed. It is concluded that technical factors and the definitions used influenced the reported rates of penicillin tolerance. The epidemiological data suggest that tolerance is not limited to a single streptococcal serotype. Furthermore, there is not sufficient data to support a correlation between in vitro penicillin tolerance of group A streptococci and treatment failure, either in clinical cases or in animal studies. On the other hand, evidence to exclude penicillin tolerance as a cause of treatment failure is also not available. Therefore, at present penicillin tolerance cannot be ruled out as a cause of penicillin treatment failures.

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.

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.

Human heart-infiltrating T-cell clones from rheumatic heart disease patients recognize both streptococcal and cardiac proteins

BACKGROUND

beta-Hemolytic streptococcal infection in developing countries still causes thousands of causes of rheumatic heart disease, demanding surgical valve correction. Antigenic mimicry between self and streptococcal components has been proposed as the triggering factor leading to autoimmunity in individuals with genetic susceptibility. Although heart streptococcal-M protein cross-reactive antibodies have been demonstrated, heart tissue damage seems to be T lymphocyte-dependent. We studied the infiltrating T lymphocytes in rheumatic heart lesions with the aim of understanding the role of cellular immune response at the site of the lesions.

METHODS AND RESULTS

We obtained 107 T-cell clones from surgical fragments of cardiac tissue from four rheumatic heart disease patients. We tested their capacity to recognize streptococcal M protein-derived synthetic peptides and heart proteins. We found eight infiltrating T-cell clones from all four patients that simultaneously recognize streptococcal M and heart proteins. Among the M-protein sequences tested, only synthetic peptides corresponding to regions 1 through 25, 81 through 103, and 163 through 177 were simultaneously recognized with heart protein fractions. Interestingly, regions 81 through 103 and 163 through 177 have been known to bear heart cross-reactive epitopes at the antibody level. Five of these clones are CD4+, and one is CD8+.

CONCLUSIONS

The presence of heart-M protein cross-reactive T-cell clones in rheumatic heart lesions suggests their direct involvement in the pathogenesis of this disease. The dissection of protective and pathogenic epitopes of streptococcal M protein is an important step in allowing the development of a safe anti-streptococcal synthetic vaccine.

Analysis of immunoglobulin G-binding-protein expression by invasive isolates of Streptococcus pyogenes

Invasive group A streptococcal isolates collected as part of a Centers for Disease Control and Prevention surveillance study were analyzed for expression of immunoglobulin G (IgG)-binding proteins. Two IgG-binding phenotypes of group A isolates of the M1 serotype were identified. The first group expressed a surface protein that bound all four human IgG subclasses (type IIo) and was recognized by rabbit anti-serotype M1-specific antiserum but not by normal rabbit serum. The second group expressed an IgG-binding protein that was also recognized by the anti-serotype M1 antiserum but demonstrated significant nonimmune reactivity only with human IgG3 (type IIb). Analysis of extracts of the isolates for reactivity with human IgA, fibrinogen, and albumin was also performed. The importance of the binding of human plasma proteins to pathogenic group A streptococci remains to be established.

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.

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.

The patterns of oropharyngeal microflora in patients with homozygous sickle cell disease

A controlled prospective study was carried out between 16 July 1991 and 31 January 1992 to evaluate the oropharyngeal flora in homozygous sickle cell disease (SS). Throat swabs for cultures were taken from 163 asymptomatic SS patients attending sickle cell clinics (90 children and 73 adults). Throat swabs were also taken from 84 asymptomatic healthy individuals as a control group (44 children and 40 adults). Group A beta hemolytic Streptococci were isolated from 16.6% of children with SS compared to 4.5% of children without SS (P<0.05). Staphylococcus aureus was isolated from 16.4% of adults with SS compared to 0% of adults without SS (P<0.0001). Group G beta hemolytic Streptococci and nongroupable Streptococci were also isolated from 11% and 13.7% of adults with SS compared to 0% and 2.5% of adults without SS respectively. Several other organisms were isolated only from SS patients. We conclude that the oropharyngeal flora of patients with SS is disturbed. This disturbance may contribute to morbidity of these patients.

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.