The Treatment of Severe Group A Streptococcal Infections

Pediatric Pyomyositis: A Rare but Important Complication of Varicella

Varicella is a common viral infection in children and most of them recover without sequelae, but serious complications can follow this infection and 6% have been reported to be musculoskeletal. A previously healthy 3-year-old Caucasian male presented with odynophagia, anorexy, fever, refusal to bear weight, and vesicular exanthema. Varicella was diagnosed, but he sustained fever around 39°C and local tenderness on the proximal lateral portion of the right leg maintaining an antalgic position. Ultrasonography and plain radiography were performed, but the magnetic resonance imaging (MRI) was performed due to the clinically worsening diagnosed pyomyositis. He was subjected to surgical debridement, and we started intravenous antibiotherapy. Streptococcus pyogenes grew in the microbiologic culture. At a 6-month follow-up, the boy did not suffer from any sequelae. The regular course of varicella is benign; however, it can occasionally develop into a more serious illness. The initial presentation of pyomyositis is often subacute, and the first symptoms may be vague. The awareness of musculoskeletal complications is imperative, and the combination of varicella's exanthema and fever followed by some limb complaint should lead to an alert attitude.

Increased β-haemolytic group A streptococcal M6 serotype and streptodornase B-specific cellular immune responses in Swedish narcolepsy cases

BACKGROUND

Type 1 narcolepsy is a neurological disorder characterized by excessive daytime sleepiness and cataplexy associated with the HLA allele DQB1*06:02. Genetic predisposition along with external triggering factors may drive autoimmune responses, ultimately leading to the selective loss of hypocretin-positive neurons.

OBJECTIVE

The aim of this study was to investigate potential aetiological factors in Swedish cases of postvaccination (Pandemrix) narcolepsy defined by interferon-gamma (IFNγ) production from immune cells in response to molecularly defined targets.

METHODS

Cellular reactivity defined by IFNγ production was examined in blood from 38 (HLA-DQB1*06:02(+) ) Pandemrix-vaccinated narcolepsy cases and 76 (23 HLA-DQB1*06:02(+) and 53 HLA-DQB1*06:02(-) ) control subjects, matched for age, sex and exposure, using a variety of different antigens: β-haemolytic group A streptococcal (GAS) antigens (M5, M6 and streptodornase B), influenza (the pandemic A/H1N1/California/7/09 NYMC X-179A and A/H1N1/California/7/09 NYMC X-181 vaccine antigens, previous Flu-A and -B vaccine targets, A/H1N1/Brisbane/59/2007, A/H1N1/Solomon Islands/3/2006, A/H3N2/Uruguay/716/2007, A/H3N2/Wisconsin/67/2005, A/H5N1/Vietnam/1203/2004 and B/Malaysia/2506/2004), noninfluenza viral targets (CMVpp65, EBNA-1 and EBNA-3) and auto-antigens (hypocretin peptide, Tribbles homolog 2 peptide cocktail and extract from rat hypothalamus tissue).

RESULTS

IFN-γ production was significantly increased in whole blood from narcolepsy cases in response to streptococcus serotype M6 (P = 0.0065) and streptodornase B protein (P = 0.0050). T-cell recognition of M6 and streptodornase B was confirmed at the single-cell level by intracellular cytokine (IL-2, IFNγ, tumour necrosis factor-alpha and IL-17) production after stimulation with synthetic M6 or streptodornase B peptides. Significantly, higher (P = 0.02) titres of serum antistreptolysin O were observed in narcolepsy cases, compared to vaccinated controls.

CONCLUSION

β-haemolytic GAS may be involved in triggering autoimmune responses in patients who developed narcolepsy symptoms after vaccination with Pandemrix in Sweden, characterized by a Streptococcus pyogenes M-type-specific IFN-γ cellular immune response.

[Lethal streptococcal toxic shock syndrome in pediatrics. Presentation of 3 cases]

Three cases of children admitted to the Pediatric Intensive Medicine Unit in the months of February to March 2004 with the diagnosis of streptococcal toxic shock syndrome are presented. Two were under 2 years of age and the initial symptoms suggested viriasis. They evolved towards septic shock with early multiorganic failure and then death due to massive hemoptysis, ventricular fibrillation due to hyperkaliemia. Streptococcus pyogenes with serotypes M1T1 was isolated in all the cases and the patients had the clinical criteria of streptococcal toxic shock syndrome. Their course was unfavorable in spite of the resuscitation steps, early antibiotic treatment and artificial support of the different organic failures. We stress the rareness of the cases, early age, its appearance in a short period of time, its sudden onset and the null response to treatment initiated.

Regulation of Apoptosis by Gram-Positive Bacteria: Mechanistic Diversity and Consequences for Immunity

Apoptosis, or programmed cell death (PCD), is an important physiological mechanism, through which the human immune system regulates homeostasis and responds to diverse forms of cellular damage. PCD may also be involved in immune counteraction to microbial infection. Over the past decade, the amount of research on bacteria-induced PCD has grown tremendously, and the implications of this mechanism on immunity are being elucidated. Some pathogenic bacteria actively trigger the suicide response in critical lineages of leukocytes that orchestrate both the innate and adaptive immune responses; other bacteria proactively prevent PCD to benefit their own survival and persistence. Currently, the microbial virulence factors, which represent the keys to unlocking the suicide response in host cells, are a primary focus of this field. In this review, we discuss these bacterial "apoptosis regulatory molecules" and the apoptotic events they either trigger or prevent, the host target cells of this regulatory activity, and the possible ramifications for immunity to infection. Gram-positive pathogens including Staphylococcus, Streptococcus, Bacillus, Listeria, and Clostridia species are discussed as important agents of human infection that modulate PCD pathways in eukaryotic cells.

Molecular diagnosis of necrotizing fasciitis by 16S rRNA gene sequencing and superantigen gene detection

We report the use of molecular techniques in the diagnosis of a case of culture-negative necrotizing fasciitis occurring in a 32-year-old female with no significant past medical history and who died within 36 hours of admission. Paraffin-embedded tissue sections from the popliteal fossa region obtained at autopsy showed hemorrhage, necrosis, and mild inflammation by hematoxylin and eosin staining. Tissue gram stain showed numerous gram-positive organisms arranged in clusters. The sequences of the first 500 bp of bacterial 16S rRNA gene amplified from the lesion were identical to a Lancefield group A beta-hemolytic Streptococcus pyogenes. Streptococcal pyrogenic exotoxin A and B superantigen genes were detected and an emm type 1 was determined by polymerase chain reaction and sequencing from the lesion. This confirmed the etiology of the patient's rapid deterioration with multisystem organ failure.

[Streptococcal toxic shock syndrome: ten years' experience at a tertiary hospital]

INTRODUCTION

In the last two decades there has been a reported increase in the incidence of streptococcal toxic shock syndrome (STSS). The objective of this study was to determine the clinical and epidemiological characteristics of this infection.

METHODS

Retrospective study of all cases of STSS diagnosed at a single tertiary hospital over the last ten years.

RESULTS

We report 13 cases of STSS (8 men, mean age 62 years). The mean annual incidence was 0.19 episodes/100,000 population from 1994 to 1998 and 0.53 episodes/100,000 population from 1999 to 2003 (p = 0.059). All patients had at least one underlying disease and there were no intravenous drug users. The most common portals of entry were the skin and soft tissues (85%) and all but one patient had a positive blood culture. Two cases were nosocomial and five patients required surgery (amputation and/or debridement). There was a high mortality rate (85%) and a rapid course from onset to death; nine patients died within four days after establishing the diagnosis.

CONCLUSION

The incidence of SSTS has increased over the last five years at our hospital. Elderly patients with underlying medical conditions were more susceptible to acquiring this infection. Early mortality was very high.

Progressive and nonresolving pneumonia

PURPOSE OF REVIEW

Patients with progressive and/or nonresolving community-acquired pneumonia are at risk for increased morbidity and mortality. It is critical to be able to identify patients at risk to institute early appropriate therapy. The purpose of this review is to summarise the most updated developments in this area.

RECENT FINDINGS

This review will glean from the recent literature clinical, laboratory, and radiologic findings that help identify patients at risk for such complications of their pneumonia. New studies will be reviewed that have identified some of the causes for treatment failures including the type of pathogen and discordant antimicrobial therapy. It will also discuss newly recognised and emerging infectious diseases that may result in progressive or nonresponding pneumonia including severe acute respiratory syndrome, avian influenzae, severe group A streptococcal disease, and community-acquired methicillin-resistant Staphylococcus aureus. Promising treatments have been identified for patients with progressive pneumonia due to an overwhelming host immune response including activated protein C and intravenous immunoglobulin.

SUMMARY

Both progressive and nonresolving pneumonia represent treatment failure as a result of inappropriate initial therapy, a noninfectious cause, or an overwhelming immune response. It is critical to be able to identify patients with nonresponding pneumonia and to identify patients at risk for progressive pneumonia to institute appropriate therapy.

egc-Encoded superantigens from Staphylococcus aureus are neutralized by human sera much less efficiently than are classical staphylococcal enterotoxins or toxic shock syndrome toxin

PCR was employed to determine the presence of all known superantigen genes (sea, seq, and tst) and of the exotoxin-like gene cluster (set) in 40 Staphylococcus aureus isolates from blood cultures and throat swabs; 28 isolates harbored superantigen genes, five on average, and this strictly correlated with their ability to stimulate T-cell proliferation. In contrast, the set gene cluster was detected in every S. aureus strain, suggesting a nonredundant function for these genes which is different from T-cell activation. No more than 10% of normal human serum samples inhibited the T-cell stimulation elicited by egc-encoded enterotoxins (staphylococcal enterotoxins G, I, M, N, and O), whereas between 32 and 86% neutralized the classical superantigens. Similarly, intravenous human immunoglobulin G preparations inhibited egc-encoded superantigens with 10- to 100-fold-reduced potency compared with the classical enterotoxins. Thus, there are surprisingly large gaps in the capacity of human serum samples to neutralize S. aureus superantigens.

Necrotizing Soft Tissue Infections

Necrotizing soft tissue infections are characterized by necrosis of skin and associated structures. Despite advances in the diagnosis and treatment of these infections, the mortality remains high. There have been increasing reports of necrotizing fasciitis caused by group A Streptococcus over the past decade. Recent information supports the role of superantigens in the pathogenesis of this infection. The approach to management requires expeditious evaluation with early surgery and appropriate antimicrobial agents. Limited data suggest that surgical debridement may be delayed in selected patients until the patient is stable by the use of intravenous immunoglobulin, which can neutralize superantigens.

Molecular basis of group A streptococcal virulence

The group A streptococcus (GAS) (Streptococcus pyogenes) is among the most common and versatile of human pathogens. It is responsible for a wide spectrum of human diseases, ranging from trivial to lethal. The advent of modern techniques of molecular biology has taught much about the organism's virulence, and the genomes of several GAS types have now been deciphered. Surface structures of GAS including a family of M proteins, the hyaluronic acid capsule, and fibronectin-binding proteins, allow the organism to adhere to, colonise, and invade human skin and mucus membranes under varying environmental conditions. M protein binds to complement control factors and other host proteins to prevent activation of the alternate complement pathway and thus evade phagocytosis and killing by polymorphonuclear leucocytes. Extracellular toxins, including superantigenic streptococcal pyrogenic exotoxins, contribute to tissue invasion and initiate the cytokine storm felt responsible for illnesses such as necrotising fasciitis and the highly lethal streptococcal toxic shock syndrome. Progress has been made in understanding the molecular epidemiology of acute rheumatic fever but less is understood about its basic pathogenesis. The improved understanding of GAS genetic regulation, structure, and function has opened exciting possibilities for developing safe and effective GAS vaccines. Studies directed towards achieving this long-sought goal are being aggressively pursued.