GRAM POSITIVE COCCI Gram positive and negative bacteria
GRAM POSITIVE COCCI • Gram positive and negative bacteria: The cell wall very different: . Peptidoglycan very strong, thick and rigid. . Teichoic acid surface antigen.
Species cause of human disease: • • Staphylococcus aureus Streptococcus pneumoniae Streptococcus pyogenic ect
Structure and function • Capsule antiphagocytosis • Peptidoglycan stimulate production of endogenous pyrogens • Protein spesific: A, M, F antiphagocytosis, anticomplementary • Teichoic acid attachment to mucosal
Pathogenesis and Immunity The virulence is determined by: a variety of structural molecule and elaborated toxins and enzymes. virulence factors
• Toxins - Exotoxin : 1. Cytotoxin 2. Enterotoxin food poisoning. resistant to gastric &jejunal enzymes. . heat stable. stimulate intestinal peristalsis
• Enzymes. Coagulase fibrin layer. Catalase H 2 O 2. Hyaluronidase spreading factors. Lipase. Fibrinolysin. Penicillinase. Ig A protease. Hemolysin : Streptolysin O antigenic
Important features of pathogenesis • Staphylococcus aureus 1. Pyogenic (abscess) - local skin infection surgical wound infection - disseminated sepsis 2. Toxigenic food poisoning
• Staphylococcus epidermidis Pyogenic iv catheter sites & prostetic devices • Staphylococcus saprophyticus Pyogenic UTI(Urinary Tract Infection )
• Streptococcus pyogenes 1. Pyogenic. Local : skin, pharing. Disseminated : sepsis 2. Toxigenic 3. Immune-mediated(post Streptococcal infection, non suppurative)
Poststreptococcal disease Immunologic response to streptococcal M protein that cross-react with human tissues. 1. Acute Glomerulonephritis antigen-antibody complexes on glomerular. 1. Acute Rheumatic Fever autoimmune disease
• Streptococcus pneumoniae Pyogenic : . Pneumonia. Otitis media. Meningitis
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