Necrotic activity of ExhC from Mammaliicoccus sciuri is mediated by specific amino acid residues.

Mammaliicoccus sciuri, a commensal and pathogenic bacterium of significant clinical and veterinary relevance, expresses exfoliative toxin C (ExhC), a specific glutamyl endopeptidase belonging to the chymotrypsin family as the principal virulence factor. However, unlike most members of this family, ETs are inactive against a wide range of substrates and possess exquisite specificity for desmoglein-1 (Dsg1), a cadherin-like adhesion molecule that is crucial to maintain tissue integrity, thereby preventing the separation of skin cells and the entry of pathogens. ExhC is of clinical importance since in addition to causing exfoliation in pigs and mice, it induces necrosis in multiple mammalian cell lines, a property not observed for other ETs. Previous experiments have implicated the ExhC79-128 fragment in causing necrosis. Site-directed mutagenesis of specific residues within this fragment were studied and led to the design of an ExhC variant containing four-point mutations (ExhCmut4) lacking necrotic potential but retaining nearly wild-type (wt) levels of enzymatic activity. Moreover, the determination of the ExhCwt and ExhCmut4 crystal structures identified the conformation in the necrosis-linked region. These results constitute an important step toward the understanding of the mechanisms underlying the necrotic and epidermolytic activity of ExhC.

Prevalence of Panton-Valentine leucocidin ( pvl) and exfoliative toxin A ( eta) gene within methicillin resistant and susceptible Staphylococcus aureus in an urban tertiary hospital: A molecular epidemiology pilot study.

Background: Staphylococcus aureus is well known to cause a multitude of clinical manifestations, from mild to severe bloodstream infections that could lead to death. Infections are common, either in community-acquired or hospital-acquired settings, and treatment remains a challenge due to methicillin-resistant Staphylococcus aureus (MRSA). The pathogenesis of S. aureus is mediated by several cell-surface and secreted virulence factors. The virulence factors discussed in this study are Panton-Valentine leucocidin ( pvl) and exfoliative toxin A ( eta). Identifying both pvl and eta gene may help in studying bacterial pathogenesis and biology thus creating possible therapeutic pathway or intervention.Our pilot study aimed to observe pvl and eta as virulence gene prevalence in a North Sumatera tertiary referral health center. Methods: Our study was a descriptive-analytical observational study with a cross-sectional design in which we collected isolates over a single time period. The frequency of genes is reported as a percentage comparison between MRSA and methicillin-susceptible S. aureus (MSSA). Qualitative gene prevalence analysis was carried out using the polymerase chain reaction (PCR). Results: Our results showed that from 38 MRSA sample isolates, 32 samples were found to be pvl-positive, or 84,3% of the total samples. From 40 MSSA sample isolates, one sample was found to be pvl-positive MSSA, or 97,5%. Regarding eta, from 38 MRSA sample isolates, 81,6% of the total sample did not have eta, while from 40 MSSA sample isolates, all samples were found to be positive for eta. We found that both pvl and eta were significantly more likely to be expressed in the MSSA strain. Conclusions: Our study shows that pvl and eta are more likely expressed in MSSA strains than in MRSA strains in Indonesia.

Detección de genes de toxinas pirogénicas y toxinas exfoliativas en aislamientos clínicos de Staphylococcus aureus en Colombia / Detection of genes of pyrogenic toxins and exfoliating toxins in clinical isolation for Staphylococcus aureaus in Colombia

Introducción: staphylococcus aureus está asociado con graves enfermedadessistémicas causadas por superantígenos (toxinas pirogénicas y exfoliativas).Métodos: 100 aislamientos clínicos de S. aureus se identificaron por métodoautomatizado y PCR, la prevalencia de genes de superantígenos por PCR múltiple y las correlaciones mediante la prueba exacta de Fischer.Resultados: en 38 aislamientos se observó que la prevalencia de los genes de enterotoxinas, toxina del síndrome de choque tóxico y toxinas exfoliativas fue 44%, 7% y 4%, respectivamente. La única correlación significativa (p = 0,045) fue entre la presencia de los genes de superantígenos y los aislamientos hospitalarios.Conclusiones: existe una alta prevalencia de genes de enterotoxinas y una baja de genes de toxinas exfoliativas y del síndrome de choque tóxico en aislamientos de S. aureus en esta población. Esta es la primera investigación que presenta datosde prevalencia de superantígenos en Colombia, y proporciona nueva información para América Latina.

Síndrome estafilocócico de la piel escaldada. Nuestra experiencia en 10 años / Staphylococcal scalded skin syndrome (SSSS). Our 10-year experience

El síndrome estafilocócico de la piel escaldada (SEPE) es una enfermedad cutánea aguda infrecuente, causada por toxinas exfoliativas del Staphylococcus aureus. El objetivo de este estudio es describir las características epidemiológicas, clínicas y terapéuticas de los pacientes con diagnóstico de SEPE en nuestro medio.Material y métodos.Se realizó un estudio retrospectivo, descriptivo y observacional, en el que se revisaron las historias clínicas de los pacientes con diagnóstico de SEPE vistos entre mayo de 2000 y mayo de 2010, atendidos en la Sección de Dermatología Pediátrica del Hospital Ramos Mejía, y entre mayo de 2005 y mayo de 2010 en el Servicio de Dermatología del Hospital Alemán.Resultados.Se incluyó un total de 62 pacientes, cuya edad media al momento del diagnóstico fue de 22 meses. No se observó predilección por sexo ni estación del año. El 13% de los pacientes recibió corticoides sistémicos previo al diagnóstico de SEPE. Todos los pacientes excepto uno, realizaron tratamiento antibiótico luego del diagnóstico de esta entidad. El 92% recibió cefalosporinas de primera generación. El 23% de los pacientes requirió internación y el 100% evolucionó satisfactoriamente.Conclusiones.El SEPE es una entidad poco frecuente. Si bien en nuestro medio no hallamos datos epidemiológicos sobre esta entidad, los datos demográficos encontrados en este estudio difieren de los publicados en la literatura mundial. Debe sospecharse en recién nacidos y niños pequeños con eritrodermia aguda y afectación peribucal o conjuntival.

Staphylococcal scalded skin syndrome (SSSS) is a rare cutaneous disease caused by exfoliativetoxins of Staphylococcus aureus. The aim of this study is to describe the epidemiology, clinicalmanifestations and treatment of patients with the diagnosis of SSSS in our community.Methods. We conducted a retrospective, descriptive and observational study, reviewing the clinicalrecords of patients with a diagnosis of SSSS, as seen between May 2000 and May 2010 atthe Pediatric Dermatology Section of the Hospital Ramos Mejía, and between May 2005 and May2010 at the Dermatology Unit of the Hospital Alemán.Results. A total of 62 patients were included, whose average age at the time of diagnosis was22 months. No predilection for sex or season of the year was observed. Thirteen percent of thepatients received systemic steroids prior to SSSS diagnosis. All but one of the patients received antibiotictreatment after the diagnosis of this entity. First generation cephaloporins were given to92% of patients; 23% of them required hospitalization and all of them had a satisfactory outcome.Discussion. SSSS is an infrequent entity. Even though there are no epidemiological studies inour country concerning SSSS, the data we gathered differs with world-wide published literature.SSSS must be suspected in new-borns and in young children with an acute onset of erythroderma,perioral affectation and conjunctivitis.