Invasive group A streptococcal infections

[A rare cause of acute abdomen in a young immunocompetent woman]

Streptococcus pyogenes is a human pathogenic, gram positive bacterium that primarily leads to pharyngitis or soft tissue infections. Primary peritonitis caused by S. pyogenes infection is rare and there are only a few published cases worldwide. Primary peritonitis due to other pathogens occurs in immunosuppressed conditions such as HIV or other chronic diseases. However, younger, healthy women are more likely to be affected by S. pyogenes peritonitis. At present, the underlying molecular mechanisms can only be speculated on. One possibility is that, similar to the clinical picture of streptococcal toxic shock syndrome (STSS), a specific serotype of the M protein in combination with inhibition of the cell response of neutrophil granulocytes could play a role. In addition to peritonitis, the clinical picture may include other organ manifestations such as acute kidney damage or circulatory dysregulation. In terms of treatment, rapid pathogen-directed empirical antibiotic therapy is the treatment of choice. If there is no indication of secondary peritonitis, diagnostic laparoscopy can be dispensed with in the further diagnostic work-up.

"Emergency" definitive reconstruction of a necrotising fasciitis thigh debridement defect with a pedicled TRAM flap

INTRODUCTION

Necrotising fasciitis (NF) is a rare, severe, rapidly progressing and life-threatening synergistic infection primarily affecting the superficial fascia. A novel method of definitive and aesthetic reconstruction of NF thigh defects by using a pedicled transverse rectus abdominis myocutaneous (TRAM) flap without recourse to temporising skin grafts is presented.

PRESENTATION OF CASE

A 30-year-old parous woman presented in extremis with fulminant NF of her left anteromedial thigh. Following emergency radical debridement and intensive care stabilisation she was reconstructed 48h later in a single stage with a pedicled TRAM flap islanded on the ipsilateral deep inferior epigastric vessels. There was excellent contour restoration of her thigh and coverage of the exposed femoral vessels.

DISCUSSION

Pedicled flaps based on the rectus abdominis muscle provide a large, readily available reconstructive option for correction of substantial regional defects as herein illustrated. They are robust when based on dominant inferior vascular pedicle with a long reach and wide arc of rotation when designed transversely (as a TRAM flap).

CONCLUSION

This case also illustrates that definitive flap reconstruction of NF can be successfully undertaken in the emergent setting, thereby negating the need for large areas of skin grafting which can lead to contractures with consequent functional impairment and suboptimal aesthetic results.

Investigation of a group A streptococcal outbreak among residents of a long-term acute care hospital

BACKGROUND

In January 2008, a long-term acute care hospital (LTACH) in New Mexico reported a cluster of severe group A Streptococcus (GAS) infections.

METHODS

We defined a case as illness in a patient in the LTACH from 1 October 2007 through 3 February 2008 from whom GAS was isolated from a usually sterile site or with illness consistent with GAS infection and GAS isolated from a nonsterile site. To identify carriers, we swabbed the oropharynx and skin lesions of patients and staff. We observed facility procedures to assess possible transmission routes and adherence to infection control practices. We also conducted a case-control study to identify risk factors for infection with use of asymptomatic patients who were noncarriers as control subjects.

RESULTS

We identified 11 case patients and 11 carriers (8 patients and 3 staff). No carriers became case patients. Significant risk factors for infection in univariate analysis included sharing a room with an infected or colonized patient (6 [55%] of 11 case patients vs 3 [8%] of 39 control subjects), undergoing wound debridement (64% vs 13%), and receiving negative pressure wound therapy (73% vs 33%). Having an infected or colonized roommate remained associated with case patients in multivariable analysis (odds ratio, 15.3; 95% confidence interval, 2.5-110.9). Suboptimal infection control practices were widespread.

CONCLUSIONS

This large outbreak of GAS infection was the first reported in an LTACH, a setting that contains a highly susceptible patient population. Widespread infection control lapses likely allowed continued transmission. Similar to the situation in other care settings, appropriate infection control and case cohorting may help prevent and control outbreaks of GAS infection in LTACHs.

Crystal structure of Spy0129, a Streptococcus pyogenes class B sortase involved in pilus assembly

Sortase enzymes are cysteine transpeptidases that mediate the covalent attachment of substrate proteins to the cell walls of Gram-positive bacteria, and thereby play a crucial role in virulence, infection and colonisation by pathogens. Many cell-surface proteins are anchored by the housekeeping sortase SrtA but other more specialised sortases exist that attach sub-sets of proteins or function in pilus assembly. The sortase Spy0129, or SrtC1, from the M1 SF370 strain of Streptococcus pyogenes is responsible for generating the covalent linkages between the pilin subunits in the pili of this organism. The crystal structure of Spy0129 has been determined at 2.3 Å resolution (R = 20.4%, Rfree  = 26.0%). The structure shows that Spy0129 is a class B sortase, in contrast to other characterised pilin polymerases, which belong to class C. Spy0129 lacks a flap believed to function in substrate recognition in class C enzymes and instead has an elaborated β6/β7 loop. The two independent Spy0129 molecules in the crystal show differences in the positions and orientations of the catalytic Cys and His residues, Cys221 and His126, correlated with movements of the β7/β8 and β4/β5 loops that respectively follow these residues. Bound zinc ions stabilise these alternative conformations in the crystal. This conformational variability is likely to be important for function although there is no evidence that zinc is involved in vivo.

Release of SpeA from Streptococcus pyogenes after exposure to penicillin: Dependency on dose and inhibition by clindamycin

The amount and time course of SpeA release from group A streptococci (GAS) was studied at different starting inoculate after exposure to different doses of penicillin, clindamycin or a combination of the 2. The release was related to the bacterial concentration and killing rate. A clinical GAS strain was exposed to benzylpenicillin, 2 and 1000 x MIC, clindamycin, 2 and 32 x MIC, or combinations of the 2. Samples for viable counts and SpeA analyses were drawn before and after the addition of antibiotics and at 3, 6 and 24 h. The SpeA release was higher at low than at high concentrations of penicillin and the combination (both, p<0.05). The addition of clindamycin to penicillin reduced SpeA production at both concentrations (p<0.01). Most SpeA was released before 3 h, and for penicillin and the combination, the amount correlated to the number of killed bacteria during this period (r=0.50; p<0.05). A positive correlation was found between the inoculum size and the SpeA concentration at time zero (r=0.54; p<0.05). The SpeA concentration was dependent on the initial number of bacteria, the class of antibiotic, the dose of penicillin and the killing rate.

Differentiation of PSRA due to Group A and due to Nongroup A Streptococci in Patients with Early Arthritis and Elevated Antisteptolysin-O at Presentation

A study was performed of consecutive patients presenting to a Dutch early arthritis clinic with a primary suggested diagnosis of reactive arthritis due to streptococci between April 1998 and January 2003, in a well-defined reference population consisting of 600 000 inhabitants. At 1 year after presentation out of 45 acute arthritis patients with initially an elevated antistreptolysin-O and without an alternative rheumatic diagnosis only 9 patients (20%) were not diagnosed as PSRA; 16 cases (36%) were due to NGAS, 20 cases (44%) due to GAS. The estimate of the annual incidence rate of PSRA in the Netherlands during the study was 1.26 per 100 000: 0.70 GAS-related. A diagnostic set of criteria was formulated based on the original Ayoub&Ahmed criteria by adding a serological criterium ASO/antiDNaseB ratio <1.4 and excluding a clinical criterium on chronicity/recurrency of arthritis: likelihood ratio for a positive test 7.9 [95% confidence interval (95%CI: 2.7–22.7)], for a negative test 0.06 [95%CI: 0.009–0.39].

High burden of invasive beta-haemolytic streptococcal infections in Fiji

We undertook a 5-year retrospective study of group A streptococcal (GAS) bacteraemia in Fiji, supplemented by a 9-month detailed retrospective study of beta-haemolytic streptococcal (BHS) infections. The all-age incidence of GAS bacteraemia over 5 years was 11.6/100,000. Indigenous Fijians were 4.7 times more likely to present with invasive BHS disease than people of other ethnicities, and 6.4 times more likely than Indo-Fijians. The case-fatality rate for invasive BHS infections was 28%. emm-typing was performed on 23 isolates: 17 different emm-types were found, and the emm-type profile was different from that found in industrialized nations. These data support the contentions that elevated rates of invasive BHS and GAS infections are widespread in developing countries, and that the profile of invasive organisms in these settings reflects a wide diversity of emm-types and a paucity of types typically found in industrialized countries.

Group A streptococcal surface GAPDH, SDH, recognizes uPAR/CD87 as its receptor on the human pharyngeal cell and mediates bacterial adherence to host cells

Streptococcal surface dehydrogenase (SDH) is a multifunctional, anchorless protein present on the surface of group A Streptococcus (GAS). It plays a regulatory role in GAS-mediated intracellular signaling events in human pharyngeal cells. Using ligand-binding assays, we have identified an approximately 55 kDa protein as an SDH-specific receptor protein on the surface of Detroit human pharyngeal cells. LC-MS/MS analyses identified this SDH-binding pharyngeal cell-surface-exposed membrane-bound protein as uPAR (urokinase plasminogen activator receptor)/CD87. Ligand-binding assays also revealed that only the N-terminal domain (D1) of uPAR bound to SDH. uPAR-D1 more specifically bound to the C-terminal alpha-helix and two immediate flanking regions of the S-loop of the SDH molecule. Site-directed mutagenesis in GAS resulting in SDH with altered C-terminal ends, and the removal of uPAR from pharyngeal cells by phosphatidylinositol-phopsholipase C treatment decreased GAS ability to adhere to pharyngeal cells. When compared to uninfected Detroit pharyngeal cells, GAS-infected pharyngeal cells showed a transient but a significant increase in the expression of uPAR-specific mRNA, and a prolonged recycling process of uPAR on the cell surface. Together, these results indicate that the specific streptococcal surface protein-pharyngeal cell receptor interaction mediated by SDH and uPAR is modulated during GAS infection of human pharyngeal cells. This interaction significantly contributes to bacterial adherence and thus may play a significant role in GAS pathogenesis by regulating intracellular signaling events in pharyngeal cells.

Dynamics of anti-M antibody response in a mouse model following intranasal infection with group A Streptococcus M-18

Dynamics of anti-M antibody response following intranasal infection with group A Streptococcus (GAS) M-18 were investigated in a Swiss albino mouse model. Mice arranged in three groups were inoculated intranasally with 2.0x10(7) c.f.u. ml-1 of GAS M-18 on 1, 2 alternate and 3 alternate days. Plasma collected from the retro-orbital plexus was tested for antibodies by an in-house indirect ELISA. The antibody titres of the plasma samples varied from 1 : 8 to 1 : 1024 in the 1 day dose, from 1 : 4 to 1 : 256 in the 2 day dose and from 1 : 4 to 1 : 128 in the 3 day dose. Peak titres were seen on day 42 or 56 and in all cases the titres had declined by day 84. Swiss albino mouse can thus serve as a useful animal model to study different aspects of type-specific anti-M immune responses against GAS disease when designing candidate streptococcal vaccines.

Role of macrophages in host resistance to group A streptococci

Macrophages provide the first line of defense against invading pathogens. The aim of this study was to determine the role of macrophages during infection with group A streptococci (Streptococcus pyogenes) in mice. Here, we report that resident macrophages can efficiently take up and kill S. pyogenes during in vivo infection, as demonstrated by immunofluorescence and electron microscopy, as well as colony counts. To evaluate the contribution of macrophages to the resolution of experimental infection with S. pyogenes, we compared the susceptibility of BALB/c mice rendered macrophage deficient by treatment with carrageenan with that of intact mice. The results show that depletion of macrophages enhanced the susceptibility of BALB/c mice to S. pyogenes infection, as evidenced by 100% mortality of macrophage-depleted mice compared to 90% survival of nondepleted control animals. The in vivo depletion of macrophages strongly enhanced bacterial loads in the blood and systemic organs. Resistance to S. pyogenes can be restored in macrophage-depleted mice by adoptive transfer of purified macrophages. The in vivo blocking of the macrophage phagocytic function by treatment with gadolinium III chloride also resulted in enhanced susceptibility to S. pyogenes. Interestingly, depletion of macrophages prior to or during the first 24 h of infection decreased survival dramatically; in contrast, no mortality was observed in infected nondepleted animals or mice depleted after 48 h of infection. These results emphasize the important contribution of macrophages to the early control of S. pyogenes infection.

Successful treatment of necrotizing fasciitis associated with diabetic nephropathy

A 50-year-old woman with a 15-year history of type 2 diabetes mellitus was admitted to our hospital due to high fever and a skin lesion with severe pain, swelling and a sensation of heat in the right thigh. Laboratory examination showed elevated C-reactive protein (CRP), thrombocytopenia, nephrotic syndrome and renal dysfunction. Her blood glucose level had been well controlled. Streptococcus agalactiae was detected in both the skin lesion and blood culture, and pathological examination revealed neutrophil infiltration in the fascia and muscle layer. The patient was diagnosed with necrotizing fasciitis, septic shock and disseminated intravascular coagulation. A combination therapy of antibiotics and surgical debridement resulted in the improvement of symptoms as supported by laboratory findings, and the skin lesion also showed improvement. Although group A streptococcus is well known to be implicated in the pathogenesis of necrotizing fasciitis, only S. agalactiae, belonging to group B streptococcus, was isolated from the tissue and blood cultures in this case. Although this organism is not virulent and rarely causes a necrotizing fasciitis, both the superficial fascial layer and underlying muscle were affected in this case. There have been only a few reports of necrotizing fasciitis due to S. agalactiae in patients with diabetes mellitus. Although the blood glucose level was well controlled in our patient, this disease might be caused by other factors, including diminished sense of touch and pain, abnormality of microcirculation and hypogammaglobulinemia due to nephrotic syndrome.

Fulminant infection and toxic shock syndrome caused by Streptococcus pyogenes

Two patients presented to the Emergency Department (ED) with features of toxic shock syndrome, including hypotension, acute respiratory distress syndrome (ARDS), renal and hepatic insufficiency and disseminated intravascular coagulation (DIC). Computed tomography (CT) scan identified the source of infection in one patient. At laparotomy, pelvic peritonitis and massive edema of the pelvic retroperitoneal tissue was found. The other patient had myonecrosis of the forearm necessitating amputation. Intra-operative cultures of tissue in each case yielded Streptococcus pyogenes, Group A. These patients were treated early with clindamycin and intensive supportive care as well as surgery, and both made a full recovery. Because of the necessity of early recognition of the varied presentation of these infections, the clinical features as well as essential interventions are emphasized. We review the pathophysiology of invasive Group A streptococcal infection to increase awareness of these uncommon but fulminant and often lethal infections.

Invasive group a streptococcal infections, Israel

We conducted a prospective, nationwide, population-based study of invasive group A streptococcal infections in Israel. We identified 409 patients (median age 27 years; range <1-92), for an annual incidence of 3.7/100,000 (11/100,000 in Jerusalem). The mortality rate was 5%. Bacteremia occurred in 125 cases (31%). The most common illnesses were soft-tissue infection (63%) and primary bacteremia (14%). Thirty percent of patients had no identifiable risk factors for infection. Eighty-seven percent of pharyngeal carriers had the same serotype as the index patient. M types included M3 (25%), M28 (10%), and M-nontypable (33%). A marked paucity of M1 serotype (1.2%) was detected. The results highlighted concentrated pockets of invasive disease in the Jewish orthodox community (annual incidence 16/100,000).

Toxic shock syndrome and bacterial superantigens: an update

Toxic shock syndrome (TSS) is an acute onset illness characterized by fever, rash formation, and hypotension that can lead to multiple organ failure and lethal shock, as well as desquamation in patients that recover. The disease is caused by bacterial superantigens (SAGs) secreted from Staphylococcus aureus and group A streptococci. SAGs bypass normal antigen presentation by binding to class II major histocompatibility complex molecules on antigen-presenting cells and to specific variable regions on the beta-chain of the T-cell antigen receptor. Through this interaction, SAGs activate T cells at orders of magnitude above antigen-specific activation, resulting in massive cytokine release that is believed to be responsible for the most severe features of TSS. This review focuses on clinical and epidemiological aspects of TSS, as well as important developments in the genetics, biochemistry, immunology, and structural biology of SAGs. From the evolutionary relationships between these important toxins, we propose that there are five distinct groups of SAGs.

Invasive streptococcal infection of the periorbita and forehead

Recent epidemiological reports suggest an increased frequency of invasive streptococcal infections linked to the appearance of a dominant group A Streptococcus serotype. Necrotizing streptococcal infections involving the skin and soft tissues of the face are uncommon. This case demonstrates the aggressive and invasive nature of these infections. The patient presented with symptoms of angioedema and was treated with corticosteroids. Her condition worsened and plastic surgery was consulted. There was extensive necrosis of the periorbital and forehead soft tissue, requiring extensive debridement to control the invasive process. Multiple reconstructive procedures were performed to close the defects and to preserve function of the facial muscles and eyelids. The literature indicates less than 50 reported cases of necrotizing streptococcal infections limited to the periorbita. This case reflects the importance of rapid diagnosis, and emphasizes the need for prompt and appropriate surgical treatment.

[Severe Streptococcus pyogenes cutaneous infections]

Streptococcus pyogenes is the first bacteria encountered in severe cutaneous infections in children. They enclose erysipela (papillar derma concerned more than hypoderma, lymphatic involvement) and necrotising fasciitis NF (focus on fascia and muscles with extension to hypoderma and reticular derma; venous thrombosis; hypodermic and aponevrotic necrosis). A skin lesion is the entrance of infection: varicella lesions are a major factor of NF. In France, sporadic cases in children are observed. The annual incidence of S. pyogenes invasive diseases is 1/100,000 children under 5 years of age and 0.6/100,000 children under 15 years of age. In North America, resurgence has been notified during the past ten years with mortality and morbidity due to NF and toxic shock syndromes. Interaction between bacteria and host, natural reservoir, explains the physiopathology. During the past ten years, some serotypes have become more invasive and virulent. Any cutaneous lesion interrupt the dermal barrier. Bacterial wall, proteins M and adhesins permit colonisation. Four pyrogenic exotoxins are superantigens; some facilitate inflammation, tissular lesions and shock; other participate to bacterial extension. In young children, immune response is immature. Albeit causal link between non-steroids anti-inflammatory drugs and NF in varicella children was not clearly demonstrated, caution should be kept in mind. Diagnosis of erysipela is clinical: sudden appearance of an inflammatory zone, most often on legs, with high fever and pain; sometime peripheral surelevation, lymphangitis, adenopathia. Other aspects open discussion with NF. In NF are in favour, added to high fever, huge pain, erythema and oedema: rapid extension of lesions, cutaneous hypoesthesia appearance, gap between intense severe general status (toxic shock syndrome) and paucity of local signs. NF is a medico-surgical emergency. Early surgery with complete excision of necrotic tissues permit survival. Magnetic resonance is useful in subacute NF. Microbiological diagnosis is possible in 20 to 80% of cases, using combined methods. Blood cultures identify the bacteria in 5 to 20%, skin lesion samples in 30%. Local samples are less useful even with modern techniques. Therapeutic strategy depends on initial diagnosis. Intra-venous antibiotics are necessary: penicillin (G, A or M) is first line therapy. In erysipela, ten days allow a rapid cure without sequellae. In NF, antibiotics are associated with intensive care and surgery. A late diagnosis, a too late surgery explain 16 to 36% of deaths encountered.

Antibiotic prophylaxis for group A streptococcal burn wound infection is not necessary

BACKGROUND

Historically, group A beta-hemolytic streptococci (GAS) burn wound infection has been a major source of morbidity and mortality in burn patients and has prompted the prophylactic administration of antibiotics to children with burns. Wound monitoring, surveillance cultures, and early excision of deep wounds may have changed this. Our objective in this project was to determine the efficacy of routine antibiotic prophylaxis in the era of early excision and closure of deep burn wounds.

METHODS

Two cohorts of burned children were compared: all children admitted during calendar years 1992 through 1994 (group 1) and during calendar years 1995 through 1997 (group 2). All group 1 children received routine GAS antibiotic prophylaxis. Only those group 2 children with documented positive admission or surveillance cultures for GAS were treated.

RESULTS

There were 511 children in group 1 and 406 children in group 2. They were well matched for age (4.7 +/- 0.21 years vs. 5.3 +/- 0.26 years, p = 0.06) and burn size (11.0% +/- 0.7% vs. 12.4% +/- 0.8%, p = 0.18). GAS species were recovered at admission or during hospitalization from 11 (2.6%) of group 1 children and 18 (4.4%) of group 2 children (p = 0.05), indicating a marginally higher rate of carriage in group 2. Nevertheless, in group 1 there were three (0.6%) who developed GAS wound infection and in group 2 there were four (0.98%, p = 0.71). The incidence of GAS infection in those patients with positive admission cultures was three (27%) of group 1 and four (22%) of group 2. No child developed fulminant GAS infection.

CONCLUSION

Routine antibiotic prophylaxis of burn wounds in children in not effective in further reducing a low baseline incidence of GAS wound infection if admission screening by culture is used to identify those children who carry the organism and early excision of deep burns is practiced.

Pathogenesis of group A streptococcal infections

Group A streptococci are model extracellular gram-positive pathogens responsible for pharyngitis, impetigo, rheumatic fever, and acute glomerulonephritis. A resurgence of invasive streptococcal diseases and rheumatic fever has appeared in outbreaks over the past 10 years, with a predominant M1 serotype as well as others identified with the outbreaks. emm (M protein) gene sequencing has changed serotyping, and new virulence genes and new virulence regulatory networks have been defined. The emm gene superfamily has expanded to include antiphagocytic molecules and immunoglobulin-binding proteins with common structural features. At least nine superantigens have been characterized, all of which may contribute to toxic streptococcal syndrome. An emerging theme is the dichotomy between skin and throat strains in their epidemiology and genetic makeup. Eleven adhesins have been reported, and surface plasmin-binding proteins have been defined. The strong resistance of the group A streptococcus to phagocytosis is related to factor H and fibrinogen binding by M protein and to disarming complement component C5a by the C5a peptidase. Molecular mimicry appears to play a role in autoimmune mechanisms involved in rheumatic fever, while nephritis strain-associated proteins may lead to immune-mediated acute glomerulonephritis. Vaccine strategies have focused on recombinant M protein and C5a peptidase vaccines, and mucosal vaccine delivery systems are under investigation.

Streptoccocus pyogenes: a forgotten cause of severe community-acquired pneumonia

We report a case of severe community-acquired pneumonia caused by Streptococcus pyogenes (Lancefield Group A streptoccocus) that was complicated by a streptococcal toxic shock syndrome. Although this micro-organism is an uncommon cause of community-acquired pneumonia, previously well individuals may be infected and the clinical course may be fulminant. A household contact was the likely point of infection. Invasive group A streptococcal disease continues to remain an important cause of morbidity and mortality in the community and therefore will continue to be encountered by intensive care physicians. Treatment of Group A streptococcal infection remains penicillin; however, clindamycin should be added in severe infection.

Non-haemorrhagic obstetric shock

The causes of non-haemorrhagic obstetric shock (pulmonary thromboembolism, amniotic fluid embolism, acute uterine inversion and sepsis) are uncommon but responsible for the majority of maternal deaths in the developed world. Clinically suspected pulmonary thromboembolism should be treated initially with heparin and objective testing should be performed. If the diagnosis is confirmed, heparin is usually continued until delivery, following which anticoagulation in the puerperium is achieved with either warfarin or heparin. Amniotic fluid embolism is a rare complication of pregnancy, occurring most commonly during labour. The management of amniotic fluid embolism involves maternal oxygenation, the maintenance of cardiac output and blood pressure, and the management of any associated coagulopathy. Acute uterine inversion arises most commonly following mismanagement of the third stage of labour. The shock in uterine inversion is neurogenic in origin, although there may also be profound haemorrhage. The management of this condition includes maternal resuscitation and replacement of the uterus either manually, surgically or by hydrostatic pressure. Genital tract sepsis remains a significant cause of maternal death, the most common predisposing factor being prolonged rupture of the fetal membranes. The management of septic shock in pregnancy includes resuscitation, identification of the source of infection and alteration of the systemic inflammatory response.

Therapeutic Approaches to Streptococcal Toxic Shock Syndrome

The streptococcal toxic shock syndrome (STSS) is a severe, life-threatening condition characterized by hypotension and multiorgan system dysfunction associated with infection by the group A Streptococcus (GAS) or rarely by streptococci of other Lancefield serogroups. It is associated with a soft tissue infection, such as necrotizing fasciitis, in about half of the cases; the remainder are secondary to a variety of other invasive and noninvasive GAS infections. Although the pathophysiology of STSS is not yet fully understood, there are compelling reasons to believe that the syndrome results at least in part from the action of the streptococcal pyrogenic exotoxins, which act as superantigens. Patients with STSS should be admitted to an intensive care unit for support of cardiovascular, respiratory, and renal function as required. In experimental models of overwhelming GAS infection, clindamycin has greater efficacy than penicillin, and therapy with this agent is recommended. Penicillin, to which GAS are uniformly susceptible, may be used in addition to clindamycin. Limited clinical experience, most of which is anecdotal, suggests marked improvement in some STSS patients after administration of intravenous immunoglobulin. Even in the absence of conclusive data, the potential benefits of intravenous immunoglobulin in this highly lethal disease make its use reasonable in life-threatening cases. Other experimental approaches are also discussed, such as the use of anti-tumor necrosis factor monoclonal antibodies and plasmapheresis.

A Streptococcus pyogenes outbreak caused by an unusual serotype of low virulence: the value of typing techniques in outbreak investigations

OBJECTIVES

To investigate and stop the spread of an outbreak of Streptococcus pyogenes infection in a district general hospital, involving 19 patients and two nurses over a 20-day period.

METHODS

All suspected persons were investigated using conventional bacteriological techniques, followed by M, T and exotoxin gene-typing of the isolates in a national reference laboratory.

RESULTS

11 patients and both nurses were associated with the acute surgical ward on one floor of the hospital. They were infected with serotype M 9/T B3264, a strain with apparently low virulence, which has not been previously associated with outbreaks. Two other patients on the same floor each had different types and there were two clusters of another S. pyogenes serotype on other floors, each involving two patients. Two (unrelated) patients yielded other types of S. pyogenes. The patients were not seriously ill but had some delay in wound healing.

CONCLUSIONS

The value of typing the isolates of S. pyogenes in this outbreak was in defining which patients were involved. No added value could be ascribed to the exotoxin gene-typing results.

Secondarily infected wounds and dermatoses: a diagnosis and treatment guide

Secondary bacterial skin infections are common complications of primary dermatoses, primary nonbacterial skin infections, traumatic lesions, ulcers, cutaneous infestations, and other miscellaneous skin diseases. Most diagnoses are based on information obtained by patient history and physical examination. Secondary bacterial skin infections may be polymicrobial, commonly include the pathogens Staphylococcus aureus and Streptococcus pyogenes, and require proper antibiotic treatment. The use of topical antibiotics avoids the risk of systemic allergic reactions or generalized side effects, and provides a high antibiotic concentration at the site of infection. Therefore, topical antibiotics should be considered as potential primary therapy in the emergency department. When systemic therapy is indicated, most commonly used agents for secondary skin infections are the penicillinase-resistant semi-synthetic penicillins; the first-generation cephalosporins, the macrolides; and combination antibacterials, such as amoxicillin/ clavulanate potassium and trimethoprim/sulfamethoxazole.

Sudden death associated with group A streptococcal infection in an 8-year-old girl with undiagnosed hypertrophic cardiomyopathy

An 8-year-old girl died suddenly without prior symptoms. Post-mortem examination identified both systemic group A streptococcal infection and hypertrophic cardiomyopathy. She had no history of cardiac symptoms and was not in a high-risk group for sudden death due to hypertrophic cardiomyopathy. We believe the disseminated but asymptomatic group A streptococcal infection precipitated her early death from hypertrophic cardiomyopathy. Sudden unexpected death during systemic infection should be followed by post-mortem examination to look for evidence of hypertrophic cardiomyopathy, as this diagnosis has genetic implications for other family members.

Bacterial arthritis due to beta-hemolytic streptococci of serogroups A, B, C, F, and G. Analysis of 23 cases and a review of the literature

The clinical features, essential laboratory findings, management, and outcome of all 23 cases of septic arthritis caused by different serogroups of beta-hemolytic streptococcus (BHS) seen at the Stanford Medical Center, Stanford, CA, from July 1, 1985, through October 31, 1996, were reviewed and compared to those found in the literature. Group A streptococci (GAS) accounted for 9 (40%) of our cases; group B (GBS), for 7 (30%); and Group G (GGS), for 7 (30%). No cases were caused by Group C (GCS) or F (GFS) during this period. During the same period, GAS accounted for 66 (33%) of 200 cases of bacteremia due to BHS, GBS, for 98 (49%); GCS, for 12 (6%); GFS, for 4 (2%); and GGS, for 20 (10%). A review of potential risk factors revealed that, with the exception of GGS, male and female patients were almost equally distributed among each of the serogroups. Patients aged 50 years and older comprised 56%-77% of each group. Associated conditions and risk factors were present among most patients (19/23, 83%); autoimmune diseases and a chronic skin wound or trauma were notably present among patients with GAS, while diabetes mellitus and malignancy were more common among patients with GBS. Infected prosthetic implants were present in 7 patients, including 4/7 patients with GGS. All patients had positive cultures of synovial fluid, and 11/23 (49%) had positive blood cultures (GAS, 5/9; GBS, 6/7; and GGS, 0/7). The clinical presentation and hospital course of patients infected with the different serogroups varied. Patients infected with GAS had the most severe disease and those with GGS the least severe. Necrotizing fascitis, shock, DIC, and admission to the intensive care unit were found only among patients infected with GAS. Despite aggressive management with antimicrobial therapy and surgery, 4/23 patients died (3 patients with GAS; 1 with GBS). The isolates from our patients were not available for study; investigations by others of the biology of BHS suggest that the production of 1 or more of the streptococcal pyrogenic exotoxins by isolates of GAS may account for the differences in the severity of disease among our patients with septic arthritis caused by different serogroups of BHS. Although septic arthritis due to BHS is uncommon, such patients provide a valuable model to study features of the host-parasite interaction that may contribute to the observed differences in severity of disease.

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

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