Invasive group A streptococcus infections

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.

Streptococcal toxic shock-like syndrome: case report and review of the literature

Streptococcal toxic shock-like syndrome is a newly recognized complication of infections by group A beta-haemolytic streptococci (GABHS). Previous reports of this syndrome have originated from developed countries, predominantly North American and Europe. This report describes a 5-year-old Saudi child who developed this syndrome in association with streptococcal pharyngitis. It indicates that the recent resurgence of severe GABHS diseases is a global phenomenon.

Analysis of Streptococcus pyogenes promoters by using novel Tn916-based shuttle vectors for the construction of transcriptional fusions to chloramphenicol acetyltransferase

We have developed a series of shuttle vectors based on the conjugative transposon Tn916 that have been designed for the analysis of transcriptional regulation in Streptococcus pyogenes and other gram-positive bacteria. Designated the pVIT vectors (vectors for integration into Tn916), the vectors are small, stable plasmids in Escherichia coli to facilitate the fusion of promoters from cloned S. pyogenes genes to a promoterless gene which encodes chloramphenicol acetyltransferase. The vectors each contain one or more small regions of Tn916 to direct the integration of the transcriptional fusion into the transposon via homologous recombination following transformation of S. pyogenes or other suitable gram-positive hosts. Integration can be monitored by the inactivation or replacement of an antibiotic resistance determinant in modified derivatives of Tn916. Promoter activity can then be quantitated by the determination of chloramphenicol acetyltransferase-specific activity. In addition, since integration is into loci that do not disrupt the conjugative transpositional functions of Tn916, the vectors are useful for analysis of regulation in strains that are difficult or impossible to transform and can be introduced into these strains by conjugation following transformation of an intermediate host. The promoters for the genes which encode both the M protein and protein F of S. pyogenes were active in pVIT vectors, as was the region which controls transcription of mry, a trans-acting positive regulator of M protein expression. However, neither of the two characterized promoters for mry demonstrated activity when independently analyzed in pVIT-generated partial diploid strains, suggesting that regulation of mry is more complex than predicted by current models. The broad host range of Tn916 should make the pVIT vectors useful for analysis of regulation in numerous other bacterial species.

Adherence and fibronectin binding are environmentally regulated in the group A streptococci

The ability of the pathogenic Gram-positive bacterium Streptococcus pyogenes (group A streptococcus) to bind fibronectin and adhere to respiratory epithelial cells is dependent on a surface protein called protein F. In this study, we have examined the regulation of expression of protein F and have shown that it is environmentally regulated in response to alterations in atmosphere. In six recent clinical isolates expression of protein F was repressed during growth under reduced concentrations of O2. Expression in an anaerobic environment was induced by both superoxide-generating and redox-altering reagents. However, regulation did not involve mry, a gene that controls expression of several streptococcal surface proteins. Protein F was constitutively expressed in one of two laboratory-passaged strains analysed, and in a complementation analysis using an allele of the gene that encodes protein F (prtF) cloned from a regulated strain and expressed in a constitutive strain, the constitutive phenotype was shown to be dominant in trans. Regulation, as monitored by fusion of prtF to a promoterless chloramphenicol acetyltransferase gene, involved transcriptional control. Environmentally induced alterations in protein F expression affected the ability of the bacterium to adhere to epithelial cells, which suggests that the ability to regulate expression of protein F may be important during infection.

Cleavage of interleukin 1 beta (IL-1 beta) precursor to produce active IL-1 beta by a conserved extracellular cysteine protease from Streptococcus pyogenes

Streptococcal pyrogenic exotoxin B (SPE B), a conserved extracellular cysteine protease expressed by the human pathogenic bacterium Streptococcus pyogenes, was purified and shown to cleave inactive human interleukin 1 beta precursor (pIL-1 beta) to produce biologically active IL-1 beta. SPE B cleaves pIL-1 beta one residue amino-terminal to the site where a recently characterized endogenous human cysteine protease acts. IL-1 beta resulting from cleavage of pIL-1 beta by SPE B induced nitric oxide synthase activity in vascular smooth muscle cells and killed of the human melanoma A375 line. Two additional naturally occurring SPE B variants cleaved pIL-1 beta in a similar fashion. By demonstrating that SPE B catalyzes the formation of biologically active IL-1 beta from inactive pIL-1 beta, our data add a further dimension to an emerging theme in microbial pathogenesis that bacterial and viral virulence factors act directly on host cytokine pathways. The data also contribute to an enlarging literature demonstrating that microbial extracellular cysteine proteases are important in host-parasite interactions.

A novel superantigen isolated from pathogenic strains of Streptococcus pyogenes with aminoterminal homology to staphylococcal enterotoxins B and C

Streptococcus pyogenes (group A Streptococcus) has re-emerged in recent years as a cause of severe human disease. Because extracellular products are involved in streptococcal pathogenesis, we explored the possibility that a disease isolate expresses an uncharacterized superantigen. We screened culture supernatants for superantigen activity with a major histocompatibility complex class II-dependent T cell proliferation assay. Initial fractionation with red dye A chromatography indicated production of a class II-dependent T cell mitogen by a toxic shock-like syndrome (TSLS) strain. The amino terminus of the purified streptococcal superantigen was more homologous to the amino termini of staphylococcal enterotoxins B, C1, and C3 (SEB, SEC1, and SEC3), than to those of pyrogenic exotoxins A, B, C or other streptococcal toxins. The molecule, designated SSA, had the same pattern of class II isotype usage as SEB in T cell proliferation assays. However, it differed in its pattern of human T cell activation, as measured by quantitative polymerase chain reaction with V beta-specific primers. SSA activated human T cells that express V beta 1, 3, 15 with a minor increase of V beta 5.2-bearing cells, whereas SEB activated V beta 3, 12, 15, and 17-bearing T cells. Immunoblot analysis of 75 disease isolates from several localities detected SSA production only in group A streptococci, and found that SSA is apparently confined to only three clonal lineages as defined by multilocus enzyme electrophoresis typing. Isolates of one of these lineages, (electrophoretic type 2) are strongly associated with TSLS. The data identify SSA as a novel streptococcal superantigen that appears to be more related structurally to staphylococcal enterotoxins than to streptococcal exotoxins. Because abundant SSA production is apparently confined to only three streptococcal clonal lineages, the data also suggest that the SSA gene has only recently been acquired by S. pyogenes.

The in vitro antibacterial activity of ceftriaxone against Streptococcus pyogenes is unrelated to penicillin-binding protein 4

The in vitro activities of penicillin and ceftriaxone were compared against 29 strains of Streptococcus pyogenes with the result that ceftriaxone showed greater activity than penicillin. The morphological changes induced by 1/2 and 1x MIC concentrations of penicillin and ceftriaxone, respectively, were very similar using scanning electron microscopy. Competitive binding studies using 'cold' penicillin or ceftriaxone as inhibitors of radiolabeled penicillin binding demonstrated that ceftriaxone had a very low affinity for penicillin binding protein (PBP) 4 compared to that of penicillin. Since ceftriaxone had greater antibacterial activity, this suggests that PBP 4 may not be important to the in vitro activity of ceftriaxone. In contrast, the IC50 for ceftriaxone was much lower (> 200 fold) for PBPs 2 and 3 compared to PBP 4, suggesting greater avidity of these high molecular mass PBPs for ceftriaxone. These data may at least in part explain the superior in vitro activity of ceftriaxone compared to penicillin against S. pyogenes. These data, together with the observation that PBP 1 was saturated at a lower concentration of penicillin than any of the other PBPs, suggest that the inhibition of PBPs 1, 2, and 3 mediates the bactericidal activity of beta-lactam antibiotics against group A streptococci.

Effect of anti-TNF-alpha treatment in an antibiotic treated murine model of shock due to Streptococcus pyogenes

Experimentally, Gram-negative septic shock can be prevented by the prophylactic use of an anti-TNF-alpha monoclonal antibody. The clinical similarity between Gram-negative and Gram-positive septic shock suggested that anti-TNF-alpha therapy might have a wide application. Increased levels of TNF-alpha were seen in a murine model of septic shock due to Streptococcus pyogenes but administration of an anti-TNF-alpha monoclonal antibody had no beneficial effect on the outcome.

T cell activation and cytokine release in streptococcal toxic shock-like syndrome

A 5-year-old girl with streptococcal toxic shock-like syndrome during varicella infection had high levels of tumor necrosis factor alpha and interleukin-6 but no interleukin-1 or interleukin-2 in the serum. Intravenous administration of gamma-globulin coincided with clinical improvement and with reduction of the levels of tumor necrosis factor alpha and interleukin-6. The data suggest that streptococcal pyrogenic exotoxins trigger synthesis of tumor necrosis factor alpha and interleukin-6 in vivo; intravenously administered gamma-globulin may down-regulate the cytokine response.

Streptococcal toxic shock-like syndrome presenting with hypoglycemia and reversible paralysis

A patient with pharyngitis progressive to Toxic Shock-Like Syndrome presented to the emergency department with a chief complaint of lower extremity paralysis. This paraplegia was completely reversed with the administration of intravenous glucose. Hypoglycemia-induced paraplegia has not previously been reported in the medical literature, and this report emphasizes the importance of considering low-blood glucose as a potential etiology for patients who present with these neurological symptoms.

Common bacterial skin infections. Diagnostic clues and therapeutic options

Prompt, accurate characterization of skin infections can help avoid serious, more invasive complications. With appropriate empirical therapy, treatment failure can be prevented. The authors of this article discuss several common skin infections, including bite wound infections, and recommend various drug regimens to consider when planning initial therapy.

Association between expression of immunoglobulin G-binding proteins by group A streptococci and virulence in a mouse skin infection model

In this study, we developed a mouse model of skin infection to test the association between expression of immunoglobulin-binding proteins by and infectivity of group A streptococci. Group A streptococci capable of crossing tissue barriers and establishing a lethal systemic infection in mice showed a higher level of immunoglobulin-binding protein expression. The group A streptococci recovered from the spleen of a mouse that died following a skin infection were found to be more virulent when injected into the skin of naive mice. Together, these results suggest that immunoglobulin-binding protein expression by group A streptococci correlates with their ability to establish invasive skin infections.

Temporal relationship of cytokine release by peripheral blood mononuclear cells stimulated by the streptococcal superantigen pep M5

We undertook this study to determine the quality, quantity, and temporal relationship of pep M5-induced cytokine release. The ability of pep M5 to stimulate interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF-alpha) production by a T-cell-depleted, monocyte- and B-cell-enriched cell population was dependent on the presence of T cells. The requirement for T cells could be met by addition of exogenous gamma interferon (IFN-gamma). In the presence of IFN-gamma, pep M5 induced the release of TNF-alpha, IL-1, and IL-6, TNF-alpha levels peaked at 24 h, while IL-1 and IL-6 levels peaked at 48 h. pep M5 induced T cells to produce IFN-gamma, which may have accounted for the ability of the super antigen to induce the production of IL-1, IL-6, TNF-alpha, and TNF-beta by peripheral blood mononuclear cells (PBMC). The addition of excess IFN-gamma to cultures of pep M5 and PBMC did not further increase the release of these cytokines at 24 and 48 h but resulted in sustained higher levels at 72 h. Interestingly, TNF-beta production occurred only in the presence of pep M5 and exogenous IFN-gamma. The ability of pep M5 to induce cytokine production was compared with that of a potent super antigen, staphylococcal enterotoxin B (SEB). SEB was a 2- to 14-fold-more-potent inducer of IFN-gamma production. Furthermore, the profile of cytokine released by PBMC in response to this super antigen mimicked that seen with pep M5 in the presence of exogenous IFN-gamma. In conclusion, pep M5 induces the production of cytokines that are involved in immune regulation and inflammation. These cytokines also play a major role in human T-cell responses to this super antigen.

Novel, rapid optical immunoassay technique for detection of group A streptococci from pharyngeal specimens: comparison with standard culture methods

A novel immunoassay system based on the changes in the reflection of light, termed an optical immunoassay (OIA), was utilized to directly detect group A streptococcal (GAS) carbohydrate antigen from clinical specimens. In two studies, a total of 1,275 throat swabs were tested for the presence of this antigen with the Strep A OIA rapid detection system and the results were compared with those of standard culture methods. In both studies, the Strep A OIA yielded more positive results than plating of the throat swab onto a selective agar, Trypticase soy agar containing sheep blood, or an enriched broth. In one study, the sensitivity and specificity of Strep A OIA compared with those of the broth-enriched culture were 97.4 and 95.6%, respectively. In a second study a sensitivity of 98.9% and a specificity of 98.6% were achieved. It was also shown that the carbohydrate antigen could be detected in the absence of viable GAS organisms. The Strep A OIA is an easily interpretable method and was shown to be more sensitive than routine culture methods for detecting GAS infections directly from throat swabs.

Positive transcriptional control of mry regulates virulence in the group A streptococcus

Transcription of the antiphagocytic M protein in the group A streptococcus (Streptococcus pyogenes) is environmentally regulated in response to CO2 and requires Mry, a trans-acting positive regulatory protein. We have examined the role of Mry in environmental regulation by analysing the factors that regulate expression of the gene that encodes Mry (mry). By employing a strategy that utilizes integrational plasmids, it was found that expression of mry requires the participation of DNA sequences that extend 473 base pairs upstream of the Mry coding region. Transcription of mry, as analysed in S1 nuclease protection assays, is initiated from two separate promoters located within this extended regulatory region. Construction and analysis of transcriptional fusions between the mry promoters and a promoterless chloramphenicol acetyltransferase gene demonstrated that mry is autoregulated and environmentally regulated in response to the level of CO2. These data suggest a model for the regulation of virulence in S. pyogenes where positive transcriptional control of mry in response to environmental stimuli regulates the expression of the M protein.

Erythrogenic toxins A, B and C: occurrence of the genes and exotoxin formation from clinical Streptococcus pyogenes strains associated with streptococcal toxic shock-like syndrome

We report the study of 53 clinical isolates of group A streptococci, all from patients with streptococcal toxic shock-like syndrome. The strains were analysed for the occurrence of the genes of erythrogenic toxins (pyrogenic exotoxins) types A, B and C and in vitro production of these toxins. In contrast to reports indicating that 85% of the toxic shock-like syndrome-associated isolates contained the erythrogenic toxin A gene, only 58.5% of our strains harboured this gene. The erythrogenic toxin C gene was detected in 22.6% of the isolates. Erythrogenic toxin A and erythrogenic toxin B were produced by 68.7% and 58.3% of the strains containing either gene. For all group A streptococci, irrespective of clinical association, the erythrogenic toxin B gene was detected in all the isolates tested. Thus, it is difficult to define a specific role for erythrogenic toxin B in toxic shock-like syndrome as there was no clear correlation between this disease and the presence of toxin genes. Our results suggest the existence of other pathogenic factor(s) produced by group A streptococci which may stimulate human peripheral T lymphocytes in a manner similar to that of erythrogenic toxins, thus explaining different observations in previous epidemiological genetic studies.

Expression of protein F, the fibronectin-binding protein of Streptococcus pyogenes JRS4, in heterologous streptococcal and enterococcal strains promotes their adherence to respiratory epithelial cells

In a previous study we reported the identification of protein F, a fibronectin-binding protein that was essential to the ability of Streptococcus pyogenes JRS4 to adhere to respiratory epithelial cells (E. Hanski and M. Caparon, Proc. Natl. Acad. Sci. USA, 89:6172-6176, 1992). To further evaluate the role of protein F in the adherence of the group A streptococci, we screened other group A streptococcal strains, including six recent clinical isolates, and one strain of Enterococcus faecalis for their capacity to bind fibronectin and for the presence of the gene encoding protein F (prtF). Seven of eight group A streptococcal strains analyzed, including all recent clinical isolates, both bound fibronectin at high affinity and contained DNA sequences that hybridized with a prtF-specific probe. One group A streptococcal isolate and the strain of E. faecalis examined neither contained a prtF-related gene nor bound fibronectin. These two strains also could not efficiently adhere to respiratory epithelial cells. However, upon the introduction of the cloned prtF gene, both of these strains gained the capacity to bind fibronectin and to adhere to respiratory epithelial cells. These results suggest that protein F is an important adhesin, which may have a general role in the virulence of the group A streptococci.

Streptococcal infection in general practice

The last 30 years have been changes in emphasis in the study of streptococci and streptococcal diseases. Earlier work concentrated mainly on the sources and methods of cross-infection and descriptive epidemiology of Streptococcus pyogenes in its major manifestations of respiratory, cutaneous and invasive infection and in the complications of rheumatic fever (RF), scarlet fever (SF) and post-streptococcal glomerulonephritis (PSGN).

Environmental regulation of virulence in group A streptococci: transcription of the gene encoding M protein is stimulated by carbon dioxide

We have found that different atmospheres can have significant effects on the transcription of emm, the gene that encodes M protein, the major virulence factor of the group A streptococcus (Streptococcus pyogenes). Expression of emm was monitored by constructing a transcriptional fusion of the promoter for emm6.1 from S. pyogenes JRS4 to a promoterless chloramphenicol acetyltransferase gene. Transcription, as measured by determining chloramphenicol acetyltransferase specific activity, was stimulated by as much as 25-fold by increased carbon dioxide tension. Expression was greater in the latter stages of growth and was not affected by growth at 30 instead of 37 degrees C. Insertional inactivation of mry, a gene encoding a positive regulator of emm6.1, reduced chloramphenicol acetyltransferase activity below the detectable level. We conclude that expression of emm is influenced by environmental factors and that the level of carbon dioxide is one signal that may influence expression of M protein during infection.

First reported case of Streptococcus pyogenes infection with toxic shock-like syndrome in Italy

A 43-year-old male who sustained a superficial hand injury developed streptococcal toxic shock-like syndrome and died within 48 hours. The clinical course of the illness in this previously well patient was rapid and fulminant. The organism responsible was a group A beta-hemolytic streptococcus which was identified as opacity factor negative, M serotype 1, T type 1. The organism produced streptococcal pyrogenic exotoxins B and C, but no detectable exotoxin A although it carried speA, the gene for exotoxin A. This is the first case reported in Italy, and further emphasizes the virulence of these organisms and the rapidity with which the illness can progress.

In-vitro stimulation of TNF-alpha from human whole blood by cell-free supernatants of gram-positive bacteria

Gram-positive bacteria are being recognized increasingly as the cause of shock-like syndromes, clinically indistinguishable from those seen in association with Gram-negative endotoxic shock. Much clinical and experimental data link tumour necrosis factor-alpha (TNF-alpha) with the pathogenesis of endotoxic shock, and a number of studies of individual Gram-positive species have also implicated TNF-alpha. We report here the first systematic study of the ability of cell-free supernatants of common Gram-positive bacteria to induce TNF-alpha from human peripheral blood monocytes in vitro. Almost all the 63 strains were able to induce TNF-alpha, although the levels were substantially lower than those obtained from supernatants of Gram-negative bacteria, used as controls. Streptococcus pneumoniae, S. pyogenes, viridans streptococci and coagulase-negative staphylococci were consistently more active than group B and D streptococci. TNF-alpha induction did not correlate with conventional markers of pathogenicity; amongst strains of Staphylococcus aureus, commensal and blood culture isolates did not induce significantly different amounts of TNF. We conclude that cell-free supernatants of most Gram-positive bacteria are capable of inducing TNF-alpha from human peripheral blood monocytes in vitro, but the significance of this finding remains to be determined.