Virulence Factors Lecture - Menoufia University PDF

VIRULENCE FACTORS Faculty of Medicine Menoufia University  Bacteria Saprophytic Parasitic Commensal Pathogenic  Bacteria Saprophytic bacteria: live free in nature and not causing disease Pathogenic bacteria : bacteria cause disease Normal flor...

VIRULENCE FACTORS Faculty of Medicine Menoufia University  Bacteria Saprophytic Parasitic Commensal Pathogenic  Bacteria Saprophytic bacteria: live free in nature and not causing disease Pathogenic bacteria : bacteria cause disease Normal flora (Commensal) : live on or in human bodies, and ordinarily do not cause human diseases  Opportunistic bacteria: Commensal bacteria may cause disease under certain conditions and should be considered as potential pathogens. if host defense decreased or if resident flora disturbed= moved from its site and enter another site (S. epidermidis flora of skin but cause urinary infection)  Normal microbial flora micro-organisms that inhabit the skin and mucus membrane of healthy normal person. Two groups of normal flora: 1. Resident normal flora 2. Transient normal flora  Virulence factors Certain structures or products that helps bacteria to cause disease  Adherence factors Pili Invasive Bacterial biofilm Virulence Factors Factors Antiphagocytic factors Toxin Extracellular production enzymes  I -ADHERENCE FACTORS They are specialized structures as Pilli that help bacterial adhesion to host cell mucous membranes. 1- pili Hair-like appendages extending from the bacterial cell surface Pili of Neisseria gonorrhoeae and E. coli help the attachment to urinary tract epithelium  2-BIOFILM Millions of microorganisms in which cells stick to each other and so to a surface especially to foreign surface and surrounds themselves by surfaces and this called the biofilm as in Urinary catheters and Biofilms The longer the urinary catheter remains in place, the greater bacteria to develop biofilms and infection Urinary catheters and Biofilms The longer the urinary catheter remains in place, the greater bacteria to develop biofilms and infection Dental plaque build up on the teeth.  II. INVASIVE FACTORS They help bacteria to invade the tissues, multiply and spread rapidly causing inflammation 1. Antiphagocytic Factors Capsule: prevents phagocytosis = intake by WBCs S.pnumonae-N.meningitidid-H.imflunza ‫كل ميكروبات المسببة اللتهاب سحاءي لها هذا الغاء‬.  2-Extracellular Enzymes 1- Collagenase and hyaluronidase: degrade collagen & hyaluronic acid and allow spread through subcutaneous tissues 2-Streptokinase: (fibrinolysin)‫الجلطات‬ ‫حقن سيولة‬ l III-TOXINS There are two types : Exotoxins and endotoxins.