Normal Human Flora (Human Microbiome) Dr.Sarmad M.H. Zeiny Baghdad College of Medicine 2014-2015
Objectives Describe important human normal flora. Demonstrate the epidemiology of human normal flora. Determine the benefits & harmful effects of normal flora.
Normal Flora: Introduction Normal flora is the term used to describe the various bacteria and fungi that are permanent residents of certain body sites. The viruses and parasites are usually not considered members of the normal flora. Commensals!!
Medically Important Members of the Normal Flora: Location Important Organisms 1 Less Important Organisms 2 Skin Staphylococcus epidermidis Staphylococcus aureus, Corynebacterium (diphtheroids), various streptococci, Nose Staphylococcus aureus 3 S. epidermidis, Corynebacterium (diphtheroids), various streptococci Mouth Viridans streptococci Various streptococci, Eikenella corrodens Dental plaque Streptococcus mutans Prevotella intermedia, Porphyromonas gingivalis Gingival crevices Various anaerobes, e.g., Bacteroides, Fusobacterium, streptococci, Actinomyces Throat Viridans streptococci Various streptococci (including Streptococcus pyogenes and Streptococcus pneumoniae), Neisseria species, Haemophilus influenzae, S. epidermidis Colon Bacteroides fragilis, Escherichia coli(e. coli) Bifidobacterium, Eubacterium, Fusobacterium, Lactobacillus, various aerobic gram-negative rods, Enterococcus faecalis and other streptococci, Clostridium Vagina Lactobacillus, E. coli, 3 group B streptococci 3 Various streptococci, various gram-negative rods. B. fragilis, Corynebacterium (diphtheroids), C. albicans Urethra S. epidermidis, Corynebacterium (diphtheroids), various streptococci, various gram-negative rods, e.g., E. coli 3 Eye S. epidermidis, S. aureus, Corynebacteria (diphtheroids) and S. pneumoniae.
Normal flora paralleled with: The term "carrier" implies that an individual harbors a potential pathogen and therefore can be a source of infection of others. The term "colonization" :the colonization of the individual with a new organism. In a sense, we are all colonized by the normal flora organisms, but this term "colonization" typically refers to the acquisition of a new organism then what?
MEMBERS OF THE NORMAL FLORA PLAY A ROLE BOTH IN THE MAINTENANCE OF HEALTH AND IN THE CAUSATION OF DISEASE:
BENEFICIAL FUNCTIONS OF NORMAL FLORA 1) It is unlikely that, in a healthy person, an invading pathogen could compete for nutrients and receptor sites. 2) Some bacteria of the bowel produce antimicrobial substances to which the producers themselves are not susceptible. 3) Bacterial colonization of a newborn infant acts as a powerful stimulus for the development of the immune system. 4) Bacteria of the gut provide important nutrients, such as vitamin K, and aid in digestion and absorption of nutrients.
BENEFICIAL FUNCTIONS OF NORMAL FLORA
Clinical problems caused by normal flora arise in the following ways: The organisms are displaced from their normal site in the body to an abnormal site. Potential pathogens gain a competitive advantage due to diminished populations of harmless competitors. Harmless, commonly ingested food substances are converted into carcinogenic derivatives by bacteria in the colon. When individuals are immunocompromised, normal flora can overgrow and become pathogenic.
Summary: Normal flora are those microorganisms that are the permanent residents of the body that everyone has. Carriers (also called chronic carriers) are those individuals in whom pathogenic organisms are present in significant numbers and therefore are a source of infection for others. Members of the normal flora play a role both in the maintenance of health and in the causation of disease.
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