Normal Flora CLS 212: Medical Microbiology Mrs. Amany Ahmed Niazy
Relationships between microOrganisms • Symbiosis: living together • The relationship (association) between two different organism living close together. • Symbiotic relationship (associations) can be one of several forms: • Neutralism, mutualism, commensalism and parasitism.
Relationships between microOrganisms Synergism: Sometimes, two (or more) microorganism may work together “team up” to produce a disease that neither could cause by itself.
What are Normal Flora (=normal microbiota)? • Normal flora (normal microbiota) are: • They includes all the microbes (bacteria, fungi, protozoa, and viruses) mainly bacteria. • They are the population of microorganisms routinely found growing on the body of healthy individuals. They can be either: • Resident microbiota inhabit body sites for extended periods. • Transient microbiota only temporary fond in a body site. • Under normal conditions in a healthy human they are harmless and may even be beneficial. • Also called Commensalsi.e. organisms that dine together or Microflora.
Stuff about Normal Flora • A fetus is sterile when born (No Normal Flora), then newborn start having the normal flora from its mother, air, food and the environment. • Once established, the composition of the normal flora is dynamic. Changesin bacterial pupulations (quantity and composition) occure in response to: • Physiological variations within the host, such as hormonal changes. • Type and amount of food consumed (obes people vs lean people) • Thus normal flora differ from one human to another depending on age, diet, and geographic habitat. • Our internal organs are sterile like the lung, spleen, liver, pancreas, bladder, CSF, and blood unless during infection. • When the number of resident normal flora is greatly reduced, opportunistic microbes can easily cause infections in these areas e.g.Candida albicans in the vagina.
Why Should We Know About Normal Flora? • We all should know about the types and distribution of normal flora in our bodies because: • It gives us better understanding of the possible infections that result from injury to a specific body site. • As well as the possible sources and significance of microorganisms isolated from the site of an infection.
Transient Normal Flora Transient microbes are just passing through. They are non-pathogenic or potentially pathogenic. Although they may attempt to colonize the same areas of the body as do resident microbiota, transients are unable to remain in the body for extended periods of time due to: • Why are these microbes temporary?? • They may be washed from external areas by bathing, or handwashing. • They may not be able to compete with resident normal flora. • They may be killed by substances produced by the resident normal flora. • They may not survive in the acidic or alkaline pH of the site. • They may be flushed away by bodily secretions like tears, sweat, oil, urine, feces,..).
Where Can We find Normal Flora? • Resident normal flora are found in sites exposed to the outside world (external environment). • Skin • Eyes (conjunctiva) and Ears • Upper Respiratory Tract (nose and throat) • Oral Cavity (Mouth) • Gastrointestinal Tract • Urogenital Tract
SKIN Normal Flora • The skin is typically dry and salty, providing an environment inhospitable to many microorganisms. • Skin can acquire any transient bacteria from the environment but it either get washed off or die because the skin inhospitable environment. • Resident bacteria of the skin can be in any layer of the skin. • The surface of the skin itself comprises several distinct environments. Areas such as the axilla (armpit), the perineum (groin) and the toe webs provide typically moister regions for bacterial growth. These "tropical forest" environments often harbor the largest diversity amongst the skin flora.
SKIN normal flora • Most of the microbial skin inhabitants can be categorized in three groups: • Diptheroids • Staphylococci • Yeasts/fungi
SKIN normal flora • Diptheroids: • Theyare responsible for body odor, caused by their breakdown of substances in sweat, which is odorless when it is first secreted. • an example of diptheroids is: • Propionibacteriumacneswhich lives in hair follicle where conditions are anaerobic. Its growth is enhanced by the oily secretion of the sebaceous glands.
SKIN normal flora • Staphylococci: • Staphylococci are the salt-tolerant organisms that grow well on the salty skin surface. The are able to grow aerobicaly and the most common of species is: • e.g. Staphylococci epidirmitidis. • They protect the skin from other pathogens by outcompeting them for space on the skin and by secreting substances that inhibit the growth of other organisms.
SKIN normal flora • Yeasts/fungi • Tiny lipophilic, meaning oil-requiring, yeasts, almost universally inhabit the normal human skin from late childhood onward. • Some fungi and yeasts can cause opportunistic infections • e.g. Candida albicans& Malasezia furfur. Malaseziafurfur. It is generally harmless but can cause dandruff
Skin Normal Flora Skin normal flora are generally harmless but it might cause bloodstream infections if skin was penetrated. or opportunistic infections in immuno-compromised individuals.
Eye normal flora • Normal healthy people commonly have no bacteria on their conjunctivae, because of the frequent automatic washing of the eye with lysozyme-rich tears and from the eyelids blinking reflex, which cleans the eye. • Any organisms recovered from the normal conjunctiva are usually few in number and originate form the skin flora.
Normalflor of the ear • The middle ear and inner ear: are usually sterile. • The outer ear and the auditory canal: contain the same normal flora of the skin. • When the person coughs, sneezes, or blows his nose, these microbes may move into the middle ear where they cause infection.
Normal flora of the respiratory tract • Lower respiratory tract: • Sinuses, trachea, bronchi, bronchioles , and alveoli are sterile. • Upper respiratory tract: • Nasal cavity, nasopharynx and pharynx (throat) are colonized by many bacterial species.
Normal flora of the respiratory tract • Upper respiratory tract: • The moist warm mucous membrane in this aria provide a very good environment for the growth of many varied population of microorganisms. • These organisms include: Diphtheroids, Staphylococcus spp., Micrococcus spp., and Streptococcus spp. • Some people are carriers for some potentially pathogenic organisms such as: • Nasopharynx: S.pneumoniae, S.pyogenes. • Nose: about 20% of people carry S.aureus in their nose.
Normal flora of the mouth • Many organisms can be found in the oral cavity. Aerobic and anaerobic bacteria, even some fungi, viruses and protozoa. • But the most common indigenous normal flora of the mouth are Streptococcal species. • Poor dental hygiene help bacteria to grow and cause dental caries (tooth decay), gingivitis (gum disease). • After dental surgeries, there might be a risk of bloodstream infection that might cause endocarditis.
Oral microflora form biofilm on food stuck over teeth. • They use O2 and create anaerobic condition. • Many anaerobic bacteria proliferate and live their. • Organic acid is produced by bacteria and lower the pH of tooth surface. • Tooth calcium phosphate is dissolved. • This is the cause of tooth decay (dental caries) and it caused by S.mutans.
Gastrointestinal Tract • Stomach: • Only few bacteria are present in the • stomach due to gastric enzymes and • acidic pH. • Small intestine: • Only few normal flora are present in • the upper part of small intestine because • bile kills them. Lower parts have more no. • of normal flora. • Large intestine: • Has more bacteria than any other part of the body. • 99% of normal flora in the large intestine are anaerobic Bacteroides spp. • Also many fungi, protozoa, and viruses can live there. • Many of the normal flora are opportunistic: i.e. if they move to other areas e.g.E.colicause urinary infection.
Normal flora of the Urogenital Tract Urinary Tract • Kidneys, Ureters and Urinary Bladder are sterile. • Lower Urethra and external opening Many bacteria, yeast, and viruses. Has the same bacteria present on the skin. As a rule these organisms dose not invade bladder because they urethra is always flushed by acidic urine
Normal flora of the Urogenital Tract • Genital Organs • Male and female genitals are sterile except vagina. • Vagina microflora varies with the stage of sexual development, influenced by the action of estrogen hormones. • Lactobacillus spp. keeps the pH acidic to protect the vagina from opportunistic infections such as: Candida albicans(yeast vaginitis), Bacteroides, or Gardnerellavaginalis(bacterial vaginosis).
Beneficial Functions of Normal Flora • Protect our organs and systems that are in direct contact with the external environment from invading pathogens. Some normal flora produce substances that kills pathogens and others compete for with them for nutrients. • In newborns, normal flora stimulates the development of immune system. • Normal flora of the gut provides important nutrients such as Vitamin K which aid in digestion and absorption of nutrients.
Harmful Effect of Normal Flora • When the normal flora are displaced from their normal site of the body: • Bloodstream infections by S. epidermidis. • UTI by E.coli. • When potential pathogens gain a competitive advantage due to diminished populations of harmless competitors; • C.difficilegrowing in the gut after antibiotic therapy. • Candida albicansin vagina when lactobacilli are diminished. • When harmless, commonly ingested food substances are converted into carcinogenic derivatives by bacteria in the colon. • Sweetener cyclamate. • When individuals are immunocompromised, normal flora can overgrow and become pathogenic.