7 Gênero Streptococcus Sistemas de classificação Quanto à hemólise Quanto ao determinante antigênicoQuanto à apresentação clínicaQuanto às provas bioquímicasRebecca LancefieldClassificação de Streptococcus beta-hemolíticos pelo Carbohidrato da parede celular grupo-específicoSorogrupos A a H e K a VGrupos A, B, C, D, e G mais importantes
8 Classificação de Lancefield - Streptococcus Beta-Hemolíticos Grupo A Streptococci:Streptococcus pyogenesUm dos patógenos mais importantesDoenças Supurativas: Faringite; Escarlatina;Infecções cutâneas & de tecidos moles; doenças sistêmicasNão-Supurativas:FRA,GNDAGrupo B Streptococci:Streptococcus agalactiaeDoenças sistêmicas, cutâneas, ITUDoenças NeonataisComplicações obstétricasREVIEW
13 Determinantes de Patogenicidade Fatores de Virulência Celulares CápsulaAntiphagocytic; Nonspecific adherenceHyaluronic acid (polysaccharide) mimics animal tissueÁcido LipoteicoicoCytotoxic for wide variety of cellsAdherence: Complexes with M protein (LTA-M) and binds to fibronectin on epithelial cellsProteína MLTA-M protein is adhesinAntiphagocyticInhibits alternate C’ pathway and opsonizationProteínas M-like: bind IgM and IgGProteína F: mediates adherence
14 Fatores de Virulência Extracelulares Exotoxinas:Estreptolisina O (SLO):Hemolytic and CytolyticPrototype of oxygen-labile and thiol-activated cytolytic exotoxins (e.g., Streptococcus, Bacillus, Clostridium, Listeria)Lytic for variety of cells: bind to cholesterol-containing membranes and form arc- or ring- shaped oligomers that make cell leaky (RBC's, WBC’s, PMN's, platelets, etc.)Causes sub-surface hemolysis on BAPStimulate release of lysosomal enzymesSLO titer indicates recent infection ( in pediatric populations)
15 Fatores de Virulência Extracelulares Exotoxinas:Estreptolisina S (SLS):Hemolytic and CytolyticOxygen stable, non-antigenicLytic for red and white blood cells and wall-less forms (protoplast, L- forms)Causes surface hemolysis on BAPLisogenia: Lysogenized bacteriophages play key role in directing synthesis of various Group A streptococcal enzymes and toxinsPyrogenic Exotoxin (erythrogenic toxin)Phage-associated muralysins (lyse cell walls) produced by both Groups A and C
16 Fatores de Virulência Extracelulares Exotoxinas:Exotoxinas Pirogênicas (Eritrogênicas) (A, B &C)Produced by more than 90% of Grp A strepLysogeny: Structural gene is carried by temperate bacteriophage, as is the case with diphtheria toxinMediate pyrogenicity (fever)Causes scarlet fever (scarletiniform) rashIncrease susceptibility to endotoxic shockType C toxin increases permeability of blood-brain barrierEnhance DTHMitogenic for T lymphocytes (cause cell division), myocardial and hepatic necrosis, decrease in antibody synthesisImmunomodulators (superantigens): stimulate T cells to release cytokinesToxina Cardiohepática
17 Fatores de Virulência Extracelulares Enzimas:Nucleases: Four antigenic types (A,B,C,D)Facilitate liquefication of pus generating growth substratesNucleases A, C have DNase activityNucleases B, D also have RNase activityEstreptoquinases: Two different formsLyse blood clots: catalyze conversion of plasminogen to plasmin, leading to digestion of fibrinC5a Peptidase: destroys C’ chemotactic signals (C5a)Hialuronidase: hydrolyzes hyaluronic acidOthers: Proteinase, NADase, ATPase, phosphatase, etc.
18 Nonsuppurative Sequelae of Acute Group A Streptococcal Infection Acute Rheumatic Fever (ARF)Inflammatory reaction characterized by arthritis, carditis, chorea (disorder of CNS with involuntary spastic movements), erythema marginatum (skin redness with defined margin), or subcutaneous nodulesWithin 2-3 weeks following pharyngitisEpidemic pharyngitis: ARF in as many as 3%Sporadic pharyngitis: ARF in 1 per 1000Morbidity & mortality linked to subsequent disease of heart valve (Rheumatic Heart Disease)Poorly understood pathogenesis with several proposed theories including cross-reactivity of heart tissues & strep AGNs?? (Type ?? hypersensitivity, exotoxins, direct invasion)IIREVIEW
19 Nonsuppurative Sequelae of Acute Group A Streptococcal Infection (cont Acute GlomerulonephritisFollows either respiratory (pharyngitis) or cutaneous (pyoderma) streptococcal infectionAssociated with well-defined group of M-typesIncidence varies from <1% to 10-15%Most often seen in children manifesting as dark, smoky urine with RBC's, RBC casts, white blood cells, depressed serum complement, decreased glomerular filtration rateLatent period: 1-2 weeks after skin infection and 2-3 weeks after pharyngitisGranular accumulations of immunoglobulin due to deposition of immune complexes within the kidney(Type ?? Hypersensitivity)IIIREVIEW
20 Streptococcus agalactiae Group B StreptococcusStreptococcus agalactiae
Your consent to our cookies if you continue to use this website.