Invasive group A streptococcus infections

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.

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

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

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.

C5a peptidase alters clearance and trafficking of group A streptococci by infected mice

Group A streptococcal C5a peptidase (SCPA) specifically cleaves the human serum chemotaxin C5a at the polymorphonuclear leukocyte (PMNL) binding site. This study tested the proposal that SCPA contributes to virulence by retarding the influx of inflammatory cells and clearance of streptococci during the first few hours after infection. To investigate the specific contribution of SCPA to the virulence of group A streptococci, scpA insertion and deletion mutants were created by directed plasmid insertion into scpA and gene replacement. The precise locations of insertion and deletion mutations were confirmed by PCR and DNA sequence analysis. The impact of mutation on virulence was investigated with a mouse air sac model of inflammation. Experiments evaluated clearance of streptococci from the air sac within 4 h after infection. SCPA- streptococci were cleared more efficiently than wild-type bacteria. Localization of streptococci in lymph nodes and spleens of infected mice revealed a significant difference between mutant and wild-type streptococci. PMNLs and other granulocytes that infiltrated the air sac were quantitated by single-color flow cytometry. The total cellular infiltrate was greater and PMNLs dominated the granulocytic infiltrates of air sacs inoculated with SCPA- mutant bacteria. The data obtained are consistent with the possibility that SCPA- streptococci are initially cleared from the site of infection primarily by PMNLs. Moreover, mutant and wild-type streptococci followed different paths of dissemination. SCPA- bacteria were transported to lymph nodes, whereas wild-type streptococci avoided transport to the lymph nodes and rapidly spread to the spleen.

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

OBJECTIVE

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

DESIGN AND PARTICIPANTS

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

RESULTS

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

CONCLUSIONS

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

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 gangrene of the eyelids and orbit

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Molecular subtyping of prevalent M serotypes of Streptococcus pyogenes causing invasive disease

Reproducible methodologies and a scheme for high-resolution genotyping of Streptococcus pyogenes were defined with respect to a study of six predominant M serotypes causing invasive group A streptococcal disease in the United Kingdom. Serotype reference strains were compared with nine clinical isolates of each serotype from patients with diseases such as pneumonia, puerperal sepsis, toxic shock-like-syndrome, cellulitis, or necrotizing fasciitis. Four enzymes were evaluated for their discriminatory power in 16S rRNA gene-specific ribotyping. Discriminatory power was greatest with EcoRI, which generated serotype-specific ribotypes, and with SacI, which could subdivide strains of the same M serotype. Twenty-five combined ribotypes were found among the 60 strains, and the indices of discriminatory power (D values) of this method varied from 0.51 within serotype M1 to 0.98 within strains of serotype M5. Macrorestriction with the rarely cutting endonuclease SmaI and pulsed-field gel electrophoresis gave D values varying from 0.37 within serotype M1 to the maximal 1.0 within serotype M5. Comparison of macrorestriction profiles revealed various degrees of genetic heterogeneity within M serotypes. Strains of M1, M3, M6, and M11 exhibited clonally related macrorestriction profiles, while those of R28 and M5 strains were consistent with polyphyletic origin.

Molecular structure of staphylococcus and streptococcus superantigens

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

Specific binding of the activator Mga to promoter sequences of the emm and scpA genes in the group A streptococcus

Transcription of the surface-associated virulence factors of the group A streptococcus (GAS) Streptococcus pyogenes, M protein (emm) and the C5a peptidase (scpA), is activated by a protein called Mga (formerly Mry or VirR). To determine whether Mga binds directly to the promoters of the genes it regulates, a protein resulting from the fusion of Mga to the C-terminal end of maltose-binding protein was purified from Escherichia coli. Specific binding to the promoter regions of the scpA and emm alleles of the type M6 GAS strain JRS4 was demonstrated by electrophoresis of the DNA-protein complex. Competition studies showed that the region upstream of scpA bound MBP-Mga with a slightly higher affinity than did the region upstream of emm. DNase I protection experiments identified a single 45-bp binding site immediately upstream of and overlapping the -35 region of both promoters. Sequences homologous to the protected regions were found in the promoters of many emm, scp, and emm-like genes from strains of different serotypes of GAS, and a consensus Mga binding site was deduced.

Clonal structure of invasive Streptococcus pyogenes in Northern Scotland

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

Septic pulmonary thrombosis in streptococcal toxic shock syndrome

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

Invasion of cultured human cells by Streptococcus pyogenes

The invasive capacity of streptococcal strains belonging to groups A and B was evaluated by infecting human epithelial and endothelial cells and monitoring the number of viable intracellular bacteria at different times postinfection. All strains tested entered eukaryotic cells (HeLa, HEp2 and HUVE), with Streptococcus pyogenes exhibiting a higher invasion efficiency than group B streptococci (GBS). No intracellular multiplication was observed, and GBS remained viable 24 h postinfection, whereas S. pyogenes were gradually killed. We found that cytochalasin D almost completely inhibited internalization of all bacterial strains, whereas colchicine had no effect, indicating that host microfilaments play a major role in bacterial internalization. Moreover, the use of the lysosomotropic agent ammonium chloride enabled us to demonstrate that a pH increase in the intracellular vesicles did not affect streptococcal entry. These results were documented by electron microscopic observations which revealed the different steps in the invasion pathway, including a fusion event between phagosomes containing S. pyogenes and lysosomes.

A case of necrotizing fasciitis due to Streptococcus pneumoniae

We report a patient suffering from necrotizing fasciitis. The principal pathogen was Streptococcus pneumoniae. As far as we are aware, this is the first reported case of necrotizing fasciitis (NF) attributable to this organism. We discuss the pathogenesis of NF, and review the literature relating to this disorder.

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.

Non-instrumental immunoassay based on coloured polyacrolein latex: application to group-specific polysaccharide of Streptococcus pyogenes

Non-instrumental immunoassay methods based on immunofiltration and microtiter particle agglutination (MPA) techniques have been developed using coloured polyacrolein latex. These methods have been applied to the quantification of the group-specific polysaccharide, A-PS, of S.pyogenes (group A Streptococcus) and compared to the standard ELISA tests. The assay with the ability to detect the lowest concentration of antigen was MPA; as little as 0.05 ng A-PS/ml or 10(4) cells/ml could be detected in 1.5 h. In comparison to ELISA test the sensitivity of MPA was 10 times higher and the procedure of the assay was much more simple. The sensitivity of the immunofiltration assay using both enzyme and latex markers was shown to be the same (50 ng A-PS/ml) and the duration of the assay 3-5 min. No cross-reactions of latex conjugates with non A Streptococcus cell lysates have been observed. The developed methods are easy to perform and require neither sophisticated equipment nor specially trained personal.

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

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

Membrane cofactor protein (CD46) is a keratinocyte receptor for the M protein of the group A streptococcus

The pathogenic Gram-positive bacterium Streptococcus pyogenes (group A streptococcus) is the causative agent of numerous suppurative diseases of human skin. The M protein of S. pyogenes mediates the adherence of the bacterium to keratinocytes, the most numerous cell type in the epidermis. In this study, we have constructed and analyzed a series of mutant M proteins and have shown that the C repeat domain of the M molecule is responsible for cell recognition. The binding of factor H, a serum regulator of complement activation, to the C repeat region of M protein blocked bacterial adherence. Factor H is a member of a large family of complement regulatory proteins that share a homologous structural motif termed the short consensus repeat. Membrane cofactor protein (MCP), or CD46, is a short consensus repeat-containing protein found on the surface of keratinocytes, and purified MCP could competitively inhibit the adherence of S. pyogenes to these cells. Furthermore, the M protein was found to bind directly to MCP, whereas mutant M proteins that lacked the C repeat domain did not bind MCP, suggesting that recognition of MCP plays an important role in the ability of the streptococcus to adhere to keratinocytes.

Genetic diversity and relationships among Streptococcus pyogenes strains expressing serotype M1 protein: recent intercontinental spread of a subclone causing episodes of invasive disease

Chromosomal diversity and relationships among 126 Streptococcus pyogenes strains expressing M1 protein from 13 countries on five continents were analyzed by multilocus enzyme electrophoresis and restriction fragment profiling by pulsed-field gel electrophoresis. All isolates were studied for the presence of the gene encoding streptococcal pyrogenic exotoxin A by PCR. Strain subsets were also examined by automated DNA sequencing for allelic polymorphism in genes encoding M protein (emm), streptococcal pyrogenic exotoxin A (speA), streptokinase (ska), pyrogenic exotoxin B (interleukin-1 beta convertase) (speB), and C5a peptidase (scp). Seven distinct emm1 alleles that encode M proteins differing at one or more amino acids in the N-terminal variable region were identified. Although substantial levels of genetic diversity exist among M1-expressing organisms, most invasive disease episodes are caused by two subclones marked by distinctive multilocus enzyme electrophoretic profiles and pulsed-field gel electrophoresis restriction fragment length polymorphism (RFLP) types. One of these subclones (ET 1/RFLP pattern 1a) has the speA gene and was recovered worldwide. Identity of speA, emm1, speB, and ska alleles in virtually all isolates of ET 1/RFLP type 1a means that these organisms share a common ancestor and that global dispersion of this M1-expressing subclone has occurred very recently. The occurrence of the same emm and ska alleles in strains that are well differentiated in overall chromosomal character demonstrates that horizontal transfer and recombination play a fundamental role in diversifying natural populations of S. pyogenes.

Invasive Group a Streptococcal Soft Tissue Infection and the Streptococcal Toxic Shock Like Syndrome

A recent increase in the number of patients with severe group a streptococcal soft tissue infections and the streptococcal toxic shock like syndrome (stsls) in Edmonton sparked the interest to review eight cases that occurred between March 1991 and December 1993, including two patients after cosmetic surgery. These cases were felt to be sporadic and not linked. Four of the eight patients (age range 25 to 64 years), including one patient following upper blepharoplasties, developed invasive infection without shock. These patients presented one to seven days after the initiating event with only mild fever, but severe pain and localized erythema and swelling in the affected area which progressed quickly with the formation of bullae. Two streptococcal specimens were serotyped as M1 and contained streptococcal pyrogenic exotoxins (spe) a and B. Management included surgical debridement, penicillin, and clindamycin (interferes with M-protein and toxin production). All four patients recovered. The other four patients, including one patient following rhytidectomy, (age range 45 to 83 years) were much more ill and developed stsls. They rapidly developed septic shock within 12 to 24 h and progressed to multiorgan involvement despite surgical debridement. One streptococcal specimen was serotyped as M1 and positive for spe a and B, another specimen as M12 and positive for spe B, and another specimen as M-nontypable and positive for spe B. Two patients died within five days of presentation. The other two patients recovered following lengthy hospitalization, reconstructive surgery and rehabilitation.

The group A streptococcal virR49 gene controls expression of four structural vir regulon genes

Within a genomic locus termed the vir regulon, virR genes of opacity factor-nonproducing (OF-) group A streptococci (GAS) are known to control the expression of the genes encoding M protein (emm) and C5a peptidase (scpA) and of virR itself. Within the corresponding genomic locus, opacity factor-producing (OF+) GAS harbor additional emm-related genes encoding immunoglobulin G- and immunoglobulin A-binding proteins (fcrA and enn, respectively). The virR gene region of the OF+ GAS M-type 49 strain CS101 was amplified by PCR, and 2,650 bp were directly sequenced. An open reading frame of 1,599 bp exhibited 76% overall homology to published virR sequences. By utilizing mRNA analysis, the 5' ends of two specific transcripts were mapped 370 and 174 bp upstream of the start codon of this open reading frame. The deduced sequences of the corresponding promoters and their locations differed from those of previously reported virR promoters. Transcripts from wild-type fcrA49, emm49, enn49, and scpA49 genes located downstream of virR49 were characterized as being monocistronic. The transcripts were quantified and mapped for their 5' ends. Subsequently, the virR49 gene was inactivated by specific insertion of a nonreplicative pSF152 vector containing recombinant virR49 sequences. The RNA from the resulting vir-mut strain did not contain transcripts of virR49, fcrA49, emm49, or enn49 and contained reduced amounts of the scpA49 transcript when compared with wild-type RNA. The mRNA control from the streptokinase gene was demonstrated not to be affected. When strain vir-mut was rotated in human blood, it was found to be fully sensitive to phagocytosis by human leukocytes. Thus, the present study provides evidence that virR genes in OF+ GAS could be involved in the control of up to five vir regulon genes, and their unaffected regulatory activity is associated with features postulated as crucial for GAS virulence.

Primary group A streptococcal peritonitis

Primary peritonitis caused by Group A beta-haemolytic streptococci (GAS) is extremely rare and is usually only seen in the presence of underlying disease. This report describes the case of a previously fit young woman who developed primary GAS peritonitis. She had a laparotomy performed at which large amounts of intra-peritoneal pus was identified but no focus of infection was found. Broad spectrum antibiotics were initially used, these were changed to intravenous benzylpenicillin when GAS was isolated. She made a good recovery and was discharged 2 weeks after admission on oral amoxycillin. The organism was serotyped as T3/M3/R3 (opacity factor negative) and it is interesting that the same serotype was isolated from a throat swab taken from her daughter. We also discuss the possible routes of infection and the epidemiology of invasive GAS disease.

Streptococcal toxic-shock syndrome: spectrum of disease, pathogenesis, and new concepts in treatment

Since the 1980s there has been a marked increase in the recognition and reporting of highly invasive group A streptococcal infections with or without necrotizing fasciitis associated with shock and organ failure. Such dramatic cases have been defined as streptococcal toxic-shock syndrome. Strains of group A streptococci isolated from patients with invasive disease have been predominantly M types 1 and 3 that produce pyrogenic exotoxin A or B or both. In this paper, the clinical and demographic features of streptococcal bacteremia, myositis, and necrotizing fasciitis are presented and compared to those of streptococcal toxic-shock syndrome. Current concepts in the pathogenesis of invasive streptococcal infection are also presented, with emphasis on the interaction between group A Streptococcus virulence factors and host defense mechanisms. Finally, new concepts in the treatment of streptococcal toxic-shock syndrome are discussed.

Comparative study of cytokine release by human peripheral blood mononuclear cells stimulated with Streptococcus pyogenes superantigenic erythrogenic toxins, heat-killed streptococci, and lipopolysaccharide

The differences between toxic or septic shocks in humans during infections by streptococci and gram-negative bacteria remain to be fully characterized. For this purpose, a quantitative study of the cytokine-inducing capacity of Streptococcus pyogenes erythrogenic (pyrogenic) exotoxins (ETs) A and C, heat-killed S. pyogenes bacteria, and Neisseria meningitidis endotoxin (lipopolysaccharide [LPS]) on human peripheral blood mononuclear cells (PBMC) and monocytes has been undertaken. The levels of interleukin-1 alpha (IL-1 alpha), IL-1 beta, IL-6, IL-8, tumor necrosis factor alpha (TNF-alpha), and TNF-beta induced by these bacterial products and bacteria were determined by using cell supernatants. The capacity of ETs to elicit the monocyte-derived cytokines IL-1 alpha, IL-1 beta, IL-6, and TNF-alpha was found to depend on the presence of T lymphocytes, because of the failure of purified monocytes to produce significant amounts of these cytokines in response to ETs. PMBC elicited large amounts of these cytokines, as well as IL-8 and TNF-beta, with an optimal release after 48 to 96 h. The most abundant cytokine produced in response to ETA was IL-8. In contrast to the superantigens ETA and ETC, LPS and heat-killed streptococci stimulated the production of significant amounts of IL-1 alpha, IL-1 beta, IL-6, and TNF-alpha, with optimal production after 24 to 48 h in monocytes, indicating no significant involvement of T cells in the process. ETs, but neither LPS nor streptococci, were potent inducers of TNF-beta in PBMC. This study outlines the differences in the pathophysiological features of shock evoked by endotoxins and superantigens during infection by gram-negative bacteria and group A streptococci, respectively. The production of TNF-alpha was a common pathway for LPS, streptococcal cells, and ETs, although cell requirements and kinetics of cytokine release were different.

Beta haemolytic group A streptococci causing urinary tract infection

OBJECTIVE

To describe the clinical and laboratory findings in patients with Group A streptococci (GAS) bacteriuria.

PATIENTS

Patients with GAS bacteriuria seen in a tertiary care hospital in southern India between 1988 and 1993 were identified. Data were collected from the hospital records.

RESULT

GAS were isolated from 15 women and 11 men. Clinical data were available for 24 of these. The condition presented as asymptomatic bacteriuria (nine patients), dysuria or frequency (12), and fever without localizing signs (three). All infections occurred in individuals with systemic or local conditions predisposing to urinary tract infection. All patients responded well to antimicrobial therapy.

CONCLUSION

GAS bacteriuria is rare and occurs only in individuals with other predisposing conditions. Patients with this infection respond well to therapy.

Production and partial characterization of monoclonal antibodies against erythrogenic toxins type A and C from Streptococcus pyogenes

Hybridoma cell lines producing monoclonal antibodies against streptococcal erythrogenic toxins type A and C were established from fusions of immunized BALB/c mice splenocytes with P3X63-Ag8.653 myeloma cells. Six MAbs recognize ETA and 11 MAbs bind to ETC. Two MAbs (designated ETA-2 and ETC-10) were produced in ascitic fluid and further characterized. ETA-2 (IgG2a) binds to ETA with an affinity constant of 1.8 x 10(10) M-1 and ETC-10 (IgG1) binds to ETC with an affinity constant of 3.5 x 10(9) M-1. The specificities of the MAbs were evaluated by ELISA and immunoblotting. Both MAbs ETA-2 and ETC-10 are useful in developing specific double-sandwich ELISAs, in which the MAbs were used as solid-phase capture antibodies for the quantitative determinations of ETA and ETC.

Invasive group A streptococcus carriage in a child care centre after a fatal case

After a fatal case of invasive group A streptococcal disease, serotype T-1, in a child care centre, group A streptococcal T-1 prevalence was measured and risk factors for carriage were determined. A total of 87% (224/258) had throat culture tests. Group A streptococcus was isolated from 57 (25%), and of the 50 isolates serotyped, 38 (76%) were T-1. Group A streptococcal T-1 prevalence was 18% (38/217) and six of nine rooms had children with group A streptococcal T-1 isolates. The risk of group A streptococcal T-1 carriage was increased for children who shared the index case's room (odds ratio (OR) = 2.7; 95% confidence interval (CI) = 0.8 to 9.4) and for each additional hour per week in child care (OR = 1.03; 95% CI = 1.001 to 1.061); and decreased in children taking antibiotics in the preceding four weeks (OR = 0.2; 95% CI = 0.1 to 0.9). Carriage of the invasive group A streptococcal strain could not be determined by identified risk factors alone.

New pathogens in pneumonia

It appears that many commonly recognized syndromes such as the ARDS may well be caused by agents that have only recently emerged as respiratory pathogens. HPS represents one such entity. It appears likely that the increasing pressure of antibiotic use as well as the reemergence of certain pathogens will continue to challenge the clinician. Paramount to the identification and treatment of unusual pneumonias will be the degree with which an effort is made to make an etiologic diagnosis through sputum examination, transtracheal aspirate, bronchoscopy, or lung biopsy. Although pneumococcal pneumonia is the most common community-acquired pneumonia seen by practicing physicians, in all likelihood from time to time a physician will encounter pneumonia caused by one of the unusual pathogens described in this article or else by an altogether new pathogen.

M protein and protein F act as important determinants of cell-specific tropism of Streptococcus pyogenes in skin tissue

The pathogenic gram-positive bacterium Streptococcus pyogenes (group A streptococcus) causes numerous diseases of cutaneous tissue, each of which is initiated after the interaction of the bacterium with the cells of the epidermis. In this study, we show that different surface proteins of S. pyogenes play important roles in determining the cell-specific tropism of the bacterium in skin. Using streptococcal strains with defined mutations in the genes which encode surface proteins in combination with primary cultures of human skin and an in situ adherence assay which uses histological sections of human skin, we show that the M protein of S. pyogenes mediates the binding of the bacterium to keratinocytes, while a second streptococcal surface protein, protein F, directs the adherence of the organism to Langerhans' cells. Characterization of binding revealed that adherence was inhibited by purified streptococcal proteins and pretreatment of both host cells with the protease trypsin. Adherence was only slightly affected by the state of keratinocyte differentiation in vitro, but was considerably modulated in response to environmental conditions known to regulate expression of M protein and protein F, suggesting that the interaction between these bacterial cell-surface structures/adhesins and keratinocytes and Langerhans' cells may play an important role in streptococcal skin disease.

Dual infections with Staphylococcus aureus and Streptococcus pyogenes causing toxic shock syndrome. Possible synergistic effects of toxic shock syndrome toxin 1 and streptococcal pyrogenic exotoxin C

We describe a 35-year-old woman with clinical, microbiologic, and serologic findings suggesting that the patient developed toxic shock syndrome as a result of dual infections caused by toxin-producing strains of Staphylococcus aureus and Streptococcus pyogenes. Certain aspects of the pathogenesis of this toxin-related syndrome are reviewed.

Serious group A beta-hemolytic streptococcal infections complicating varicella

STUDY OBJECTIVE

To alert practicing emergency physicians to an important and possibly increasing relationship between life-threatening group A beta-hemolytic streptococcal (GABHS) infections and children recovering from varicella.

DESIGN

A case series of six patients managed from January through March 1993.

SETTING

A university-affiliated pediatric specialty emergency department.

TYPE OF PARTICIPANTS

Six previously healthy immunocompetent children between 1 and 5 years of age seen in our ED over a nine-week period.

RESULTS

Six children had onset of varicella two days to two weeks before developing a serious life-threatening GABHS infection. Children presented with clinical symptoms of invasive GABHS infection with bacteremia (one patient); streptococcal toxic shock syndrome with negative blood culture (two), pneumonia with pleural effusion and streptococcal toxic shock syndrome (one), pneumonia with pleural effusion (one), and pyomyositis of the thigh (one). Four of six patients required intensive care admissions and aggressive support of vital signs. All six survived.

CONCLUSION

Emergency physicians should be aware of the association between varicella and serious GABHS infections and be prepared to recognize and aggressively manage serious complications should they occur.

The identification of rofA, a positive-acting regulatory component of prtF expression: use of an m gamma delta-based shuttle mutagenesis strategy in Streptococcus pyogenes

Binding of the Gram-positive pathogenic bacterium Streptococcus pyogenes (group A streptococcus) to respiratory epithelium is mediated by the fibronectin-binding adhesin, protein F. Most strains of streptococci regulate the expression of protein F in response to oxygen levels and redox potential; however, JRS4 constitutively binds high levels of fibronectin under all environmental conditions. In this study, we have examined the regulation of protein F expression in JRS4 using a shuttle mutagenesis strategy novel to S. pyogenes. Cloned DNA representing the chromosomal loci adjacent to the gene which encodes protein F (prtF) was subjected to transposon mutagenesis in Escherichia coli using a derivative of transposon m gamma delta that was modified to contain a streptococcal antibiotic-resistance gene. mutagenized DNA was then returned to the streptococcal chromosome by allelic replacement. Analysis of the resulting fibronectin-binding phenotypes revealed that insertions in a region upstream of prtF abolished the constitutive phenotype. However, these mutants now demonstrated regulation in response to both oxygen levels and redox potential. Because these insertions define a locus responsible for the constitutive phenotype, it has been designated rofA (regulator of F). Chromosomal interruption studies using integrational plasmids together with complementation data from a previous study (VanHeyningen et al., 1993) suggested that rofA acts as a positive trans-acting regulator of prtF. Construction of prtF-lacZ fusions indicated that transcription of prtF is constitutive in JRS4 but is regulated in rofA mutants. Analysis of the DNA sequence defined by the rofA insertions revealed a 1495 bp open reading frame, whose predicted product (RofA) possessed both a putative helix-turn-helix motif and limited homology to two other transcriptional activators (Mry, PrgR) of Gram-positive surface proteins. Sequences homologous to rofA were found in regulated strains of S. pyogenes, which suggests that rofA may act as an activator of prtF in response to an unidentified environmental signal. We speculate that the allele reported here contains a mutation that renders it constitutively active.