Microbiology – Lecture 2 Normal Flora

Objectives 1. 2. 3. Define the terms: Normal Flora, Resident flora, Transient flora and carrier state Know the origin of normal flora. Know the importance of normal flora with examples, including importance as: Source of opportunistic infection., Immunostimulation, Nutrition: Vitamins production, Production of Carcinogens, Protection against external invaders. 4. 5. Know areas of the body with normal flora (GIT, Urogenital tract, and skin) and most common types of organism in these areas and relation to pathogenicity of these organism. Know sites of the body with no normal flora e.g. sterile body sites and the importance of this fact in relation to interpretation of culture results. What is Normal flora? They are a population of microorganisms that are frequently found on the skin ,mucous and other sites in a normal healthy individual. Some are found in association with humans and animals. The Majority are bacteria. • Has symbolic relationship with the host. • • Subject to constant changes. Altered by antimicrobial agents. Beneficial Effects of Normal Flora 1- Immunostimulation (antibody production) 2- Exclusionary effect (vacuum effect ) and protection from external invaders. دودحلا سرح يز 3- Antagonize other bacteria through the production of substances that inhibit or kill non-indigenous bacteria. 4-Production of essential nutrients (Vitamin K & B) by some normal intestinal flora eg. Eschericia coli ( E.coli). Origin of Normal Flora: 1) Newborn is sterile in uterus. 2) After birth , newborn is exposed to flora of mother’s genital tract, skin, respiratory tract, flora of those handling him , and the organisms in the environment. Normal flora Facts About Normal Flora May be a source of opportunistic infections in patients with impaired defense mechanisms. eg. Staphylococcus epidermidis & E.coli. Found in skin Some may cross react with normal tissue components ,eg. antibodies to various ABO group arise because of cross reaction between intestinal flora and the antigens of A & B blood substances. Production of Carcinogens: Some normal flora may modify through their enzymes chemicals in our diets into carcinogens. eg. artificial sweeteners may be enzymatically modified into bladder carcinogens. Affected by antibiotics, tissue damage, m