Mycotic Aneurysm Caused by Streptococcus constellatus subsp. constellatus

An infected mycotic aneurysm due to Streptococcus constellatus subsp. constellatus has not previously been reported. We report on this condition in an 87-year-old woman who had aggravating abdominal pain and a large fusiform aneurysm over the thoracic-abdominal aorta with mural thrombus. Isolates from two sets of blood cultures and the debrided tissue were identified as S. constellatus subsp. constellatus by their biochemical reaction profiles, compatible 16S rRNA gene sequencing results, and sequencing results for the partial groESL gene and the 16S-23S intergenic spacer region.     

Mycotic Keratitis Due to Aspergillus nomius

We report the first known case of fungal keratitis caused by Aspergillus nomius. Ocular injury was known as a predisposing factor. The patient was treated with natamycin and econazole eye drops, itraconazole eye ointment, and oral ketoconazole. A therapeutic penetrating keratoplasty was performed 16 days after presentation. A sequence-based approach was used to assign the isolate to a species.     

Management of Infections Due to Antibiotic-Resistant Streptococcus pneumoniae

Antibiotic-resistant strains of Streptococcus pneumoniae are becoming more prevalent throughout the world; this has resulted in modifications of treatment approaches. Management of bacterial meningitis has the greatest consensus. Strategies for treating other systemic infections such as pneumonia, bacteremia, and musculoskeletal infections are evolving, in part related to the availability of new antibiotics which are active in vitro against isolates resistant to penicillin and the extended-spectrum cephalosporins. However, there are currently very limited data related to the clinical efficacy of these new agents. The studies upon which current recommendations are based are reviewed. Otitis media represents the single most common infection due to S. pneumoniae. Recommendations for treatment of acute otitis media due to drug-resistant strains and the rationale for these recommendations are discussed.     

Molecular and Clinical Diagnosis of Group A Streptococcal Pharyngitis in Children

Group A Streptococcus (GAS) pharyngitis is a very common condition causing significant morbidity in children. Accurate diagnosis followed by appropriate antimicrobial therapy is recommended to prevent postinfectious sequelae. Diagnosis of GAS pharyngitis by a rapid antigen detection test (RADT) or culture in the absence of discriminating clinical findings remains challenging. Validation of new sensitive rapid diagnostic tests is therefore a priority. The performance of a loop-mediated isothermal amplification (LAMP) assay (illumigene assay) for the diagnosis of GAS pharyngitis was compared with that of a RADT and standard culture in 361 pediatric throat swab samples. Discrepant results were resolved using an alternate molecular assay. Test results were correlated with clinical presentations in patients positive by either method. The closest estimate of the true prevalence of GAS pharyngitis was 19.7% (71/361 samples). The illumigene assay alone detected 70/71 GAS-positive samples; RADT and culture detected 35/71 and 55/71 samples, respectively. RADT followed by culture confirmation of RADT-negative specimens detected 58/71 cases. The illumigene assay increased identification among children eligible for testing by American College of Physicians (ACP)/American Academy of Family Physicians (AAFP) criteria from 31 to 39 positive cases, five of which were false positives. Analysis of clinical data in GAS-positive patients indicated that a significantly greater proportion of children with McIsaac scores of ≥4 tested positive by the illumigene assay versus RADT and culture. Overall, the illumigene assay was much more sensitive and was similarly specific for GAS detection, compared to culture alone, RADT alone, or the ACP/AAFP RADT/culture algorithm. Combining high sensitivity with rapidly available results, the illumigene GAS assay is an appropriate alternative to culture for the laboratory diagnosis of GAS pharyngitis in patients for whom testing is clinically indicated.     

Cardiac Tamponade Due to Rupture of a Subepicardial Aneurysm Following Myocardial Infarction

A 71 year old male died of cardiac tamponade due to cardiac rupture 22 days after onset of acute myocardial infarction. Autopsy revealed rupture of an unusual ventricular aneurysm characterized by abrupt interruption of the myocardium, a narrow neck, a thin fibrous outer wall partially showing myocardial fibers, and lack of adhesion between the epicardium and pericardium. A review of the literature revealed that 11 among 32 autopsy cases of false aneurysm showed a similar morphology to the present case, these being classifiable as subepicardial aneurysm. Acta Pathol Jpn 41: 52 58, 1991.     

Detection of Streptococcus pyogenes by Use of Illumigene Group A Streptococcus Assay

The performance of the Illumigene group A Streptococcus assay was evaluated by comparing it to culture using 437 consecutive throat swabs. The Illumigene assay was also directly compared to PCR with 161 samples. This Illumigene assay is rapid and easy to perform. The assay also has high sensitivity (100%) compared to culture or PCR and high specificity (99.2%) compared to PCR. A total of 8.8% of the isolates were erythromycin resistant, and 6.9% were clindamycin resistant.     

A highly sensitive immuno-PCR assay for detecting Group A Streptococcus

A highly sensitive hybrid assay, based on immuno polymerase chain reaction (immuno-PCR) and enzyme-linked immunosorbent assay (ELISA) techniques, was developed for the detection of pathogenic Group A Streptococcus (Strep A). Cells were disrupted by sonication and then coated onto the walls of Maxisorp microtiter plates. Next, biotinylated anti-Group A monoclonal antibody (mAb) was bound to the antigen and then linked, via a streptavidin (STV) bridge, to biotinylated reporter DNA. After extensive washing, the denatured reporter DNA was transferred to PCR tubes, amplified, electrophoresed, and used as the signal for detection of bacteria. The minimum detection limit of this assay is the equivalent of approximately one one-thousandth of a Streptococcus pyogenes cell, even in the presence of 100,000 Escherichia coli cells. The combination of multiple antigens per cell and PCR amplification provides the extreme sensitivity in this immuno-PCR assay. No cross-reaction was found with other Streptococcus species. We also directly linked the anti-Group A monoclonal antibody to DNA using succinimidyl 4-[N-maleimidomethyl]-cyclohexane-1-carboxylate (SMCC). The sensitivity using directly linked antibody-reporter DNA was approximately 10 cells. Because this assay could be adapted for detection of many different bacteria in a variety of sample types, we tested the potential for interference from substances that could be present in clinical, food, and environmental samples. Sonicated meat or human plasma did not inhibit detection; however, extracts of concentrated soil samples were somewhat inhibitory. This highly specific, sensitive, and robust assay could be applied to clinical detection of Group A Streptococcus and serves as a model for other immuno-PCR assays.     

Characterization of Pneumonia Due to Streptococcus equi subsp. zooepidemicus in Dogs

Streptococcus equi subsp. zooepidemicus has been linked to cases of acute fatal pneumonia in dogs in several countries. Outbreaks can occur in kenneled dog populations and result in significant levels of morbidity and mortality. This highly contagious disease is characterized by the sudden onset of clinical signs, including pyrexia, dyspnea, and hemorrhagic nasal discharge. The pathogenesis of S. equi subsp. zooepidemicus infection in dogs is poorly understood. This study systematically characterized the histopathological changes in the lungs of 39 dogs from a large rehoming shelter in London, United Kingdom; the dogs were infected with S. equi subsp. zooepidemicus. An objective scoring system demonstrated that S. equi subsp. zooepidemicus caused pneumonia in 26/39 (66.7%) dogs, and most of these dogs (17/26 [65.4%]) were classified as severe fibrino-suppurative, necrotizing, and hemorrhagic. Three recently described superantigen genes (szeF, szeN, and szeP) were detected by PCR in 17/47 (36.2%) of the S. equi subsp. zooepidemicus isolates; however, there was no association between the presence of these genes and the histopathological score. The lungs of S. equi subsp. zooepidemicus-infected dogs with severe respiratory signs and lung pathology did however have significantly higher mRNA levels of the proinflammatory cytokines tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), and interleukin 8 (IL-8) than in uninfected controls, suggesting a role for an exuberant host immune response in the pathogenesis of this disease.Infectious respiratory disease in dogs is usually caused by infection with one or more viruses, such as canine parainfluenza virus (CPIV) or canine herpesvirus (CHV), or bacteria, most notably Bordetella bronchiseptica, and results in the clinical syndrome termed canine infectious respiratory disease (CIRD) (7). CIRD has a multifactorial etiology and is most prevalent in shelters where stress, due to overcrowding, results in animals becoming more susceptible to infection (8). The disease is often highly contagious with high morbidity but is rarely fatal, and recovery from mild clinical signs usually occurs within a few weeks (8). The list of pathogens associated with CIRD is extensive and continues to grow; however, for many agents, the pathogenesis and specific associated lesions are poorly defined.Streptococcus equi subsp. zooepidemicus has been shown to be associated with respiratory disease in dogs for a number of years (11); however, more recently, its significance has been highlighted by reports from several countries implicating the bacteria in a number of fatal outbreaks in shelter dogs (5, 6, 15, 24). Clinically, S. equi subsp. zooepidemicus causes severe acute respiratory distress, often with high morbidity and sometimes high mortality. At necropsy, affected dogs are usually diagnosed with severe, acute fibrino-suppurative, necrotizing, and/or hemorrhagic pneumonia.Between 1999 and 2001, as part of a study into the causes of respiratory disease in a large rehoming kennel in London, United Kingdom, a kennel where respiratory disease was endemic, Chalker et al. (6) isolated S. equi subsp. zooepidemicus from the lungs of 48/215 dogs (22.3%) and showed that the presence of S. equi subsp. zooepidemicus was associated with increasing severity of clinical respiratory disease. Streptococcus canis was also present in some dogs but was not associated with respiratory disease (6).The rapid onset of disease and fast deterioration in the clinical condition in many dogs infected with S. equi subsp. zooepidemicus are similar to human toxic shock syndrome caused by Streptococcus pyogenes (18). While the main site of inflammation in toxic shock syndrome is often the subcutaneous tissue, there are common clinical features of an acute illness characterized by pyrexia, hypovolemia, and coagulopathy (18).Pyrogenic exotoxins produced by some streptococci, including S. pyogenes, act as superantigens by binding simultaneously to major histocompatibility complex (MHC) class II receptors on macrophages and T-cell receptors, bypassing conventional antigen presentation, and leading to the activation of a large proportion of T lymphocytes (9). The ensuing cytokine “avalanche” includes the production of proinflammatory cytokines, such as interleukin 1β (IL-1β), interleukin 6 (IL-6), and tumor necrosis factor alpha (TNF-α) (12, 20).The presence of superantigen genes in strains of S. pyogenes has been linked to increased virulence and has also been suggested to contribute to the pathogenesis of “strangles,” a severe disease of horses caused by S. equi subsp. equi (4, 19, 21, 23). Superantigen genes have also been detected in some isolates of S. equi subsp. zooepidemicus (2, 13, 17). One canine isolate of S. equi subsp. zooepidemicus (isolate SzBHS5) was recently shown to encode three novel superantigen genes, szeF, szeN, and szeP, the products of which share 59%, 34%, and 49% amino acid sequence identity with the superantigens SpeH, SpeL, and SpeM of S. pyogenes, respectively (23a).The aims of this study were (i) to characterize systematically the microscopic changes in canine lungs following infection with S. equi subsp. zooepidemicus, (ii) to test for possible associations between the severity of clinical signs, lung pathology, and the presence of S. equi subsp. zooepidemicus, and (iii) to investigate whether severe lung pathology is linked to the presence of superantigen genes in S. equi subsp. zooepidemicus isolates and/or the upregulation of the proinflammatory cytokines TNF-α, IL-8, and IL-6.We demonstrate the following. (i) S. equi subsp. zooepidemicus in dogs most often causes severe fibrino-suppurative, necrotizing, and hemorrhagic pneumonia. (ii) Marked elevation of the mRNA of proinflammatory cytokines TNF-α, IL-8, and IL-6 is observed in dogs with S. equi subsp. zooepidemicus-induced pneumonia. (iii) As many as three superantigen genes are prevalent in canine isolates of the bacterium.     

Group B Streptococcal Pharyngitis in the Compromised Adult: Therapeutic Considerations

Group B streptococci (GBS) have been infrequently recognized as a cause of pharyngitis. We report three cases of GBS pharyngitis in patients with underlying diseases, two of whom were treated with and responded incompletely to oral beta-lactam antibiotics. The susceptibility of 20 clinical isolates of GBS was tested by a broth dilution method to six antibiotics which could conceivably be used in the therapy of GBS pharyngitis. Penicillin G, clindamycin, and erythromycin were most active with mean minimal inhibitory concentrations (MIC) of 0.06 μg/ml or less. Rifampin and cefaclor were least active with mean MICs of 0.71 ug/ml or more. Ampicillin was intermediate in its activity. Therapy traditionally used for Group A streptococcal (GAS) pharyngitis may, at times, be suboptimal for GBS pharyngitis in compromised patients. This may be due to higher minimal bactericidal concentrations (MBC) of GBS than GAS, to inadequate penetration of penicillins into pharyngeal tissues or to host factors. It is suggested that GBS can cause pharyngitis in adults, particularly the compromised patient, and that in cases where there is a poor response to penicillin or ampicillin therapy, alternative drugs (erythromycin or clindamycin) may be used.     

A型链球菌(GAS)毒素调控因子及其调控机制

A型链球菌是一类革兰氏阳性病原菌,其产生的多种毒素因子是导致人体多重感染的重要原因.这些菌毒素因子的表达直接或间接地受多个毒素调控系统调控,各个调控系统之间存在相互关联并对病原菌与宿主的相互作用产生影响.干扰毒素的产生或调控通路对于发展特异的抗A型链球菌感染药物具有重要的意义.     

Group A Streptococcus Induces Apoptosis in Human Epithelial Cells

Internalization of group A streptococcus (GAS) by epithelial cells may have a role in causing invasive diseases. The purpose of this study was to examine the fate of GAS-infected epithelial cells. GAS has the ability to invade A-549 and HEp-2 cells. Both A-549 and HEp-2 cells were killed by infection with GAS. Epithelial cell death mediated by GAS was at least in part through apoptosis, as shown by changes in cellular morphology, DNA fragmentation laddering, and propidium iodide staining for hypodiploid cells. A total of 20% of A-549 cells and 11 to 13% of HEp-2 cells underwent apoptosis after 20 h of GAS infection, whereas only 1 to 2% of these cells exhibited spontaneous apoptosis. We further examined whether streptococcal pyrogenic exotoxin B (SPE B), a cysteine protease produced by GAS, was involved in the apoptosis of epithelial cells. The speB isogenic mutants had less ability to induce cell death than wild-type strains. When A-549 cells were cocultured with the mutant and SPE B for 2 h, the percentage of apoptotic cells did not increase although the number of intracellular bacteria increased to the level of wild-type strains. In addition, apoptosis was blocked by cytochalasin D treatment, which interfered with cytoskeleton function. The caspase inhibitors Z-VAD.FMK, Ac-YVAD.CMK, and Ac-DEVD.FMK inhibited GAS-induced apoptosis. These results demonstrate for the first time that GAS induces apoptosis of epithelial cells and internalization is required for apoptosis. The caspase pathway is involved in GAS-induced apoptosis, and the expression of SPE B in the cells enhances apoptosis.     

Point-of-Care Testing for Group A Streptococcus Infection and Influenza

Point of care (POC) testing has emerged as a critical tool in the early and rapid diagnosis and treatment of infectious diseases. While the mainstay of these POC tests has been lateral-flow-based antigen detection assays, recent technological advances in nucleic acid detection combined with regulatory changes has allowed more sensitive detection of infectious etiologies in the near-patient setting. This advancement is particularly impactful in the ambulatory setting, where rapid diagnosis can ensure appropriate treatment at the early stages of infection, both preventing more serious sequelae and also improving physician workflow and patient satisfaction. Along with this new technology come concerns about quality of testing, nucleic acid contamination, and the appropriate use of POC tests. This review covers the clinical manifestations of disease, the current state of POC testing, and the impact of molecular testing for both group A Streptococcus infection and influenza.     

Cytokine Response to Group B Streptococcus Infection in Mice

This study was undertaken to better understand the complex relationship between specific and non-specific host defence mechanisms and group B streptococci (GBS). A comprehensive kinetics analysis of cytokine mRNA expression was performed, by Northern blot assay, in peritoneal exudate cells (PEC) and spleen cells (SC) recovered from CD-1 mice at various times during the course of an intraperitoneal infection with a lethal dose (5 × 10³ microorganisms/mouse) of type Ia GBS, reference strain 090 (GBS-Ia). Analysis of cytokines involved in the development of a specific T_H response shows that GBS-Ia in PEC induce only a weak increase of IL-2 mRNA expression and in SC a cytokine pattern characterized by IL-2, IFN-γ and IL-12 in the absence of IL-4, IL-5 and IL-10. This selected cytokine pattern could provide appropriate conditions for the development of a T_H1 response. Analysis of inflammatory cytokines, which are usually induced early during an in vivo infection, shows that there is a significant expression of mRNA specific for IL-1β, TNFα and IL-6, both in PEC and SC only at 24 h which persists at a high level until 36 h. This delayed cytokine induction, accompanied by the contemporary activation of splenic phagocytic cells, occurs only when the number of GBS-Ia is extremely high. In fact, at 24 h GBS-Ia have heavily colonized all organs. In vitro infection of thioglycollate-elicited peritoneal macrophages confirms that the ability of GBS-Ia to induce a strong inflammatory cytokine response depends strictly on the number of infecting microorganisms. Indeed, macrophages respond to GBS-Ia with a very rapid induction of IL-1β and TNFα mRNA when infected at a ratio of 1:10, but not at 100:1. Two major observations emerged from this study: (1) GBS-Ia, by inducing a cytokine pattern which seems to favour development of a T_H1 response, could evade antibody production essential for resistance to GBS; and (2) inflammatory cytokine response is induced when a heavy microbial invasion of the host has already occurred. These novel features of GBS-Ia could contribute to the development and progression of lethal infection in mice.     

Group A Streptococcus (Streptococcus pyogenes): the Most Interesting Pathogen in the World

Group A Streptococcus, or Streptococcus pyogenes, is a facultatively anaerobic Gram-positive coccus and one of the most common causes of bacterial infection in humans. The introduction of antibiotics has greatly reduced the morbidity and mortality associated with this organism, but despite uniform susceptibility to treatments of choice, it remains a significant human pathogen. It is particularly problematic in underdeveloped and lower socioeconomic status countries, where hygiene may be suboptimal. This review covers a wide range of topics related to the organism, including diagnosis, treatment, and clinical manifestations. Where possible, the review addresses less conventional and often controversial topics that have not been extensively reviewed elsewhere, such as the activity of trimethoprim sulfamethoxazole against the species, penicillin tolerance, and the use of protein synthesis inhibitors to reduce toxin production and improve outcomes.