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GRAM POSİTİVE COCCİ Non-motile, Non-Sporing and Facultative anaerobes …

- - - - TOXİN:
        CYTOTOXİNS: (alpha, beta, delta, gamma, and
        Panton-Valentine leukocidin), cytolytic toxins have been described as hemolysins,firrst four toxins are not restricted solely to red blood cells, and P-V leukocidin is unable to lyse erythrocytes,Toxic for many cells, including erythrocytes,
        fibroblasts, leukocytes, macrophages, and platelets
        HEMOLYSİNS: hemolysis is caused by cytotoxins, particularly alpha toxin,cause lysis of red blood cells
        LEUKOCİDİNS: Panton-Valentine leukocidin toxin
        Creates pores in leukocytes (WBC),WBC necrosis,Common in lungs,
        TOXİC SHOCK SYNDROME TOXİN:
        Associated with prolonged use of vaginal tampons or nasal packing
        TSST-1 is a superantigen that crosslinks MHC II and T-cell receptor, resulting in polyclonal T-cell activation, uncontrolled inflammation,Massive release of cytokines from both macrophages and t cells
        Toxic Shock Syndrome
        fever, vomiting, rash, desquamation, shock, end-organ failure
        NOTE: Superantigens are a class of antigens that result in excessive activation of the immune system,specifically they cause non-specific activation of T-cells resulting in polyclonal T cell activation and massive cytokine release
        EXFOLİATİN A AND B: destroys keratinocyte attachments in the stratum granulosum,damage Desmoglein-1 that connects
        Keratinocytes, Scalded skin syndrome:no bacteria on the lesions because the lesion is due to a toxin not at the presence of a multiplication of the bacteria, typically affects infants and young children ,children <6-year-old ,blisters ,no bacteria
        ENTEROTOXİN :Gastroenteritis/food poisoning
        is an intoxication rather than an infection
        Preformed, superantigens; capable of inducing nonspecific activation of T cells and massive cytokine release
        intoxication
        Numerous distinct staphylococcal enterotoxins (A to X)
        have been identifed, with enterotoxin A most commonly associated with food poisoning.
        enterotoxin B causes staphylococcal pseudomembranous enterocolitis
        Heat stable, not destroyed by cooking,
        Short incubation period (2- 6 hr), followed by vomiting and abdominal cramps (more common) and diarrhea (rare),
        Meats, mayonnaise, and custard are food source,
        improper food handling result from contamination of the food by a human carrier
        staphylococcal skin infection to prepare food
        after the staphylococci have been introduced into the food through a sneeze or contaminated hand
        Supportive
        Antibiotics are unnecessary for food poisoning ; Since it is the preformed enterotoxins and not the bacterium that cause symptoms, antibiotics have no effect
      - İNFECTİONS : SKİN İNFECTİONS:
        S. aureus is a part of normal skin flora
        Problems arise when there are big breaks in the skin and
        there are many S. aureus bacteria in the skin
        bullous impetigo:is a localized form of SSSS
        have localized blisters that are culture positive
        we have the presence of many bacterial cell
        infants and young children
        Folliculitis : impetigo involving hair follicles
        Furuncles or boils: large, painful, pus filled cutaneous nodules
        Carbuncles: Coalescence of furuncles with extension into subcutaneous tissues and evidence of systemic disease (fever, chills, bacteremia)
        PNEUMONİA:especially after upper respiratory tract infection,such as influenza
        ACUTE ENDOCARDİTİS : common in IV drug users,Tricuspid valve is usually affected
        SEPTİC ARTHRİTİS
        OSTEOMYELİTİS
        SEPSİS: if it gets into the blood and can lead to sepsis or death,the body's extreme response to an infection
        overwhelming immune response to the infection
        Sepsis is diagnosed using blood and urine cultures
        Toxic shock syndrome is diagnosed with blood cultures or samples from the infection itself
        TSS is the result of exotoxins of the bacteria themselves
- - - - STREPTECOCCUS PYOGENES: (GROUP A ) :
        Gram + cocci in pairs or chains
        Beta-hemolytic
        Pyrrolidonyl arylamidase (PYR) +
        Bacitracin sensitive
        lancifield grouping according to their cell wall antigens : A :group specific
        group-specific carbohydrate (A antigen) and type-specific proteins (M protein) in cell wall
        Pharyngitis and soft-tissue infections typically caused by strains with different M proteins
        normally colonize peacefully : skin ,mucous, pharynx,vagina
        grows on enriched blood agar
        Person-to-person spread by respiratory droplets (pharyngitis) or through breaks in skin after direct contact with infected person, fomite, or arthropod vector
        Hyaluronic acid capsule: inhibits phagocytosis
        which is a common component of human connective tissue.Thus, Streptococcus pyogenes can evade host detection as the capsule is non-immunogenic
        Protein M: Main virulence factor for strep. pyogenes,Inhibits phagocytosis and activation of complement, type specific cell wall antigen
        Streptolysin (Hemolysin) O: oxygen-labile hemolysin , Lyses RBCs (causing beta-hemolysis)
        cutaneous infections do not develop ASO antibodies
        Streptolysin S: oxygen-stable hemolysin, can lyse erythrocytes, leukocytes, and platelets. responsible for the characteristic β-hemolysis seen on blood agar media.
        streptokinase: virulence factor that converts plasminogen to plasmin which in turn degrades fibrin, preventing development of a fibrin barrier at the site of infection,
        Enables more spread from initial site of infection
        Antibodies directed against
        these enzymes (anti-streptokinase antibodies) are a useful marker for infection
        DNase: not cytolytic but can depolymerize free deoxyribonucleic
        acid (DNA) present in pus.reduces the viscosity of the abscess material and facilitates spread. Antibodies developed against DNase B are an important marker of S. pyogenes infections
        particularly for patients with cutaneous infections, because
        they fail to make antibodies against streptolysin O
        (anti-DNase B test)
        SUPPURATİVE İNFECTİONS
        Pharyngitis (bacterial strep throat): most common cause of bacterial pharyngitis
        Scarlet Fever : complication of streptococcal pharyngitis; occurs when the infecting strain is lysogenized by
        a bacteriophage that mediates production of a pyrogenic exotoxin; strawberry tongue
        Impetigo
        Erysipelas
        Cellulitis
        Necrotizing fasciitis
        Streptococcal Toxic Shock Syndrome: production of pyrogenic exotoxins; this toxin act as a superantigen
        Bacterimia
        NON SUPPURATİVE
        Rheumatic fever: is a nonsuppurative complication of S.
        pyogenes pharyngitis not skin infections, characterized by inflammatory changes involving the heart, joints, blood vessels, and subcutaneous tissues.
        mitral valve generally infected
        antibodies against M protein or other virulence factors (e.g. streptolysin O) can attack self-tissues
        Similarity of M protein to self-cells is due to molecular mimicry
        Type ıı sensitivity reaction
        Poststreptococcal Glomerulonephritis
        Usually occurs 1-2 weeks after GAS infection(e.g. skin, pharynx)
        Type III Hypersensitivity Reaction
        TREATMENT : penicilin
        
        DIAGNOSIS:
        MICROSCOPY :
        Gram stains of affected tissue can be used to make a rapid preliminary diagnosis of S. pyogenes soft-tissue infections
        but not pharyngitis or nonsuppurative complications
        many species of streptococci are part of the
        normal oropharyngeal fora, so observation of streptococci
        in a respiratory specimen from a patient with pharyngitis has
        no diagnostic significance.
        ANTIGEN DETECTION:
        antibodies that react with the group-specific carbohydrate in the bacterial cell wall can be used to detect group A streptococci directly in throat swabs.These tests are rapid, inexpensive, and specific.
        Antigen tests are not used for cutaneous or nonsuppurative
        diseases.
        Direct tests for the group A antigen are useful for the diagnosis of streptococcal pharyngitis
        NUCLEIC ACID BASED:
        Commercial nucleic acid probe assay and nucleic acid amplification assays are available for the detection of S. pyogenes in pharyngeal specimens.
        CULTURE:
        IDENTIFICATION:
        Differentiation of S. pyogenes from other species of streptococci with the group-specific A antigen can be determined by their susceptibility to bacitracin or the presence of the enzyme L-pyrrolidonyl arylamidase (PYR).
        ANTIBODY DETECTION:
        measurement of antibodies against streptolysin O (ASO test) is useful for confirming rheumatic fever or acute glomerulonephritis resulting from a recent streptococcal pharyngeal infection.
        anti-DNase B test should be performed pharyngitis or soft tissue infection