Video Experimental Relacionado
Updated: Jul 9, 2026
13:00
The Insect Galleria mellonella as a Powerful Infection Model to Investigate Bacterial Pathogenesis
Published on: December 11, 2012
Streptolysin S y las infecciones necrotizantes producidas por estreptococos del grupo G
Deepali Humar1, Vivekananda Datta, Darrin J Bast
1Department of Medicine, Division of Infectious Diseases, University of California, San Diego 92093, USA. vnizet@ucsd.edu
Lancet (London, England)
|January 26, 2002
Resumen
El estreptococo del grupo beta-hemolítico G causa infecciones necrotizantes graves de los tejidos blandos similares al estreptococo del grupo A. Esto se debe a la exotoxina de la estreptolisina S (SLS), codificada por un operón genético compartido, que contribuye a la patogénesis de la enfermedad.
Área de la Ciencia:
- Microbiología Microbiología.
- Enfermedades infecciosas Enfermedades infecciosas.
- La patogénesis y la patogénesis.
Sus antecedentes:
- Se observaron infecciones necrotizantes graves de los tejidos blandos (ISTN) en tres pacientes.
- Las infecciones fueron causadas por el grupo beta-hemolítico G Streptococcus.
- La presentación clínica imitaba las infecciones invasivas por estreptococos del grupo A.
Objetivo del estudio:
- Para determinar la base genética de la actividad beta-hemolítica en el grupo G Streptococcus.
- Para investigar el papel del grupo G Streptococcus beta-haemolysin en la causa de las infecciones necrotising.
- Para comparar los mecanismos patógenos de los estreptococos del grupo G y del grupo A.
Principales métodos:
- Se emplearon la hibridación, la secuenciación del ADN y la mutagénesis dirigida para identificar los genes responsables de la beta-hemólisis.
- Los estudios complementarios confirmaron la base genética del fenotipo observado.
- Se utilizó un modelo murino para evaluar la necesidad de beta-hemolisina en el desarrollo de infecciones.
Principales resultados:
- Streptococcus del grupo G posee un homólogo del grupo A Streptococcus sag operon, que codifica la estreptolisina S (SLS).
- La mutagenesis del gen sagA abolió la actividad beta-hemolítica en el grupo G Streptococcus.
- Los ratones infectados con cepas de tipo salvaje desarrollaron necrosis, mientras que los infectados con mutantes SLS-negativos no lo hicieron.
Conclusiones:
- El estreptococo del grupo beta-hemolítico G puede causar infecciones graves de los tejidos blandos necrotizantes, clínicamente indistinguibles de las causadas por el estreptococo del grupo A.
- La exotoxina estreptolisina S (SLS), codificada por un homólogo operón sag funcional, es responsable del fenotipo beta-hemolítico en el grupo G Streptococcus.
- La expresión de SLS es un factor clave en la patogénesis de las infecciones de los tejidos blandos necrotizantes por estreptococos.
Videos de Conceptos Relacionados
01:13Special Staining Techniques
Specialized staining techniques play a vital role in microbiology by enabling the visualization of specific bacterial structures that remain undetectable with standard microscopy methods. These techniques not only enhance the structural visualization of bacterial cells but also provide critical insights into their pathogenicity and classification. Additionally, they support diagnostic and research endeavors in microbiology by identifying key bacterial features.Capsule Staining for Virulence...
01:30Bacterial Phylum Spirochaetes
Spirochetes, unique bacteria in the phylum Spirochaetes, are gram-negative, motile, tightly coiled, slender, and flexible. They inhabit aquatic sediments and animals, with some causing diseases like syphilis. Spirochetes are classified into eight genera based on habitat, pathogenicity, phylogeny, and characteristics.Their distinctive motility arises from endoflagella, located within the cell’s periplasm. These endoflagella anchor at the cell poles and extend along the cell length, encased by a...
01:30Bacterial Phylum Actinobacteria
Coryneform bacteria are gram-positive, aerobic, nonmotile rods that exhibit irregular, club-shaped, or V-shaped arrangements. Their V-shape results from snapping division, where the inner cell wall layer forms the cross-wall, while the outer layer remains intact until it ruptures on one side, causing the daughter cells to bend away.The primary genera are Corynebacterium and Arthrobacter. Corynebacterium includes diverse species, ranging from saprophytes to pathogens like Corynebacterium...
01:26Bacterial Phylum Bacteroidota
The phylum Bacteroidota includes over 700 species classified into four primary orders: Bacteroidales, Cytophagales, Flavobacteriales, and Sphingobacteriales. These gram-negative, non-sporulating rods exhibit saccharolytic capabilities and can be aerobic or fermentative, encompassing obligate aerobes, facultative aerobes, and obligate anaerobes. Many species display gliding motility, though some are nonmotile or use flagella. The genus Bacteroides is well-studied due to its significant role in...
01:12Bacterial Toxins
Bacterial toxins are sophisticated virulence factors that enable pathogenic bacteria to interact with, invade, and damage host tissues. These toxins fall broadly into two types: protein exotoxins, which are secreted into the environment and target specific host receptors, and lipopolysaccharide endotoxins, which are structural components of the bacterial outer membrane released primarily during bacterial lysis or membrane shedding. Exotoxins generally act more selectively, binding to cell...
01:18Bacterial Gastroenteritis
Bacterial gastroenteritis, characterized by diarrhea, abdominal cramps, and vomiting, is often caused by ingestion of contaminated food or water and is frequently associated with pathogenic Escherichia coli strains. These microbes exploit two principal mechanisms to inflict disease.Shiga toxin–producing E. coli, also referred to as STEC—notably O157:H7—release Shiga toxins that target ribosomes, blocking protein synthesis. The B subunit of the toxin binds the host glycolipid receptor...