Normal Flora of Human Body PDF

Bacterial Normal Flora of Human Body NF lives on or within the body with out causing disease in healthy person. Commonly they are found on skin, nose, mouth, intestine (GIT), URT, urogenital tract Internal organs and tissues are normally sterile - May play an important role in protecting the hos...

Bacterial Normal Flora of Human Body NF lives on or within the body with out causing disease in healthy person. Commonly they are found on skin, nose, mouth, intestine (GIT), URT, urogenital tract Internal organs and tissues are normally sterile - May play an important role in protecting the host from pathogenic microbes - Acquired rapidly during and shortly after birth from the mother and environment (food, air etc.,).  Flora vary based on age, diet, hormonal state, health and personal hygiene. Normal f lora can be grouped in to two A. Resident flora - consists relatively f ixed types and regularly found in a given area and age A. Transient normal f lora - may be non pathogenic or potential pathogenic - may stay for hours, days or weeks If resident f lora is disturbed transient organisms may colonize and cause disease Distribution of Normal Flora in Human Body Adopted from Samuel Baron “Medical Microbiology” Advantages of normal flora prevents colonization by potential pathogens by 1. Skin bacteria produce fatty acids 2. gut bacteria releases factors which has antibacterial activity ( bacteriocins, colicins, metabolic waste product) 3. Vaginal lactobacillus maintain an acid environment 4. Occupy receptors which may be utilized by pathogens  Gut bacteria release organic acid which may have some metabolic value to the host Produce B vitamins and vitamin K and aid absorption Give antigenic stimulation (antibodies which cross reacts) Competition for nutrient, Disadvantages a. May spread to previously sterile parts of the body and cause disease E.g. - When Intestine is perforated or skin/MM is broken - During certain surgical procedures like teeth extraction b. May cause disease when - The local environment pH changes (stomach, vagina) - The immune system become ineffective - Transferred to unusual site (Organisms such as E. coli may ascend from perianal skin to urethra and cause UTI)