dr.t.v.rao md normal human flora dr.t.v.rao md 1
TRANSCRIPT
DR.T.V.RAO MD 1
Dr.T.V.Rao MD
NORMAL HUMAN FLORA
DR.T.V.RAO MD 2
HUMAN MICROBIOME• The human microbiome (or human micro biota) is the
aggregate of microorganisms that reside on the surface and in deep layers of skin, in the saliva and oral mucosa, in the conjunctiva, and in the gastrointestinal tracts. They include bacteria, fungi. Some of these organisms perform tasks that are useful for the human host. However, the majority have no known beneficial or harmful effect. Those that are expected to be present, and that under normal circumstances do not cause disease, but instead participate in maintaining
health, are deemed members of the normal flora
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• More bacterial than human cells in the body• provide some nutrients
(vitamin K)
• stimulate immune system, immunity can be cross-reactive against certain pathogens
• Prevent colonization by potential pathogens (antibiotic-associated colitis, Clostridium difficile)
NORMAL BACTERIAL FLORA
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OVERVIEW OF HUMAN-MICROBIAL INTERACTIONS
• Microbial flora of the healthy human host
1) The reasons for understanding the normal flora of the healthy human body Normal flora vs. human body ▶
Some normal flora: opportunistic pathogens ▶
when injury occurred, when resistance of body decreased, when moved to another site
2) Origin of the normal flora 3) Relationship between normal flora and human host 4) Distribution and occurrence of the normal flora
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WHERE TO FIND MICROBE?EVERYWHERE!
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INTRODUCTION OF NORMAL FLORA
1. A diverse microbial flora =>
• Human body Area: the skin and mucous membranes
• Time: shortly after birth until death
• Number: 1014 bacteria =>1013 host cells
• 2. Normal flora may:
• a. Aid the host
• b. Harm the host (in sometimes)
• c. Exist as commensals (no effect to the host)
3. Viruses and parasites => NOT normal microbial flora
• Most investigators consider that they are not commensals and do not aid the host.
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Colonization vs. Infection
Colonization: establishment of a site of reproduction of microbes on a person without necessarily resulting in tissue invasion or damage.
Infection: growth and multiplication of a microbe in or on the body of the host with or without the production of disease.
Outcomes of exposure to a microorganism:1. Transient colonization2. Permanent colonization 3. Disease
Normal Flora and Pathogenesis
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SIGNIFICANCE OF NORMAL FLORA
• 1.The normal flora influences the anatomy, physiology,
susceptibility to pathogens, and morbidity of the host.
• 2. The effect of the normal flora on the host was not well
• understood until germ-free animals became available.
• Cesarean Section => Germ-free animals => Isolators
w/o detectable pathogens (viruses, bacteria & others)
• 3. Two interesting observations:
• a. the germ-free animals lived almost twice as
long as their conventionally maintained
counterparts.
• b. the major causes of death were different in the
• two groups.
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1. Local Environment (pH, temperature, redox potential, O2, H2O, and nutrient levels…).
2. Diet
3. Age
4. Health condition (immune activity…)
5. Antibiotics,…..etc
FACTORS INFLUENCING NORMAL FLORA
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Significance of Normal Flora
Normal flora may aid the host in several ways:
• Aid in digestion of food• Help the development of mucosa
immunity • Protect the host from colonization with
pathogenic microbes.106 pathogenic microbes
GI infection
w/ normal flora
GI infection
w/ reduced flora afterStreptomycin treatment
10 pathogenic microbes
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COMPOSITION OF THE NORMAL FLORA
• The normal flora of humans are exceedingly complex and consist of more than 200 species of bacteria. The makeup of the normal flora may be influenced by various factors, including genetics, age, sex, stress, nutrition and diet of the individual. Three developmental changes in humans, weaning, the eruption of the teeth, and the onset and cessation of ovarian functions, invariably affect the composition of the normal flora in the intestinal tract, the oral cavity, and the vagina, respectively. However, within the limits of these fluctuations, the bacterial flora of humans is sufficiently constant to a give general description of the situation
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• A human first becomes colonized by a normal flora at the moment of birth and passage through the birth canal. In utero, the fetus is sterile, but when the mother's water breaks and the birth process begins, so does colonization of the body surfaces. Handling and feeding of the infant after birth leads to establishment of a stable normal flora on the skin, oral cavity and intestinal tract in about 48 hours.
WHEN WE GET COLONIZED WITH NORMAL FLORA
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• The composition of a child’s bacterial flora is dependent on the mother’s micro flora, since she is the primary source for the child’s bacteria at the outset
A NEW BORN CHILD'S FLORA IS DEPENDENT ON MOTHER
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• It has been calculated that a human adult houses about 1012 bacteria on the skin, 1010 in the mouth, and 1014 in the gastrointestinal tract. The latter number is far in excess of the number of eukaryotic cells in all the tissues and organs which comprise a human. The predominant bacteria on the surfaces of the human body are listed in Table 3. Informal names identify the bacteria in this table.
DENSITY OF NORMAL FLORA IN HUMANS
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• Resident flora • Reflects sex
of person
Normal Flora
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POTENTIAL COLONIZATION SITES
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HUMANS AS HABITATS • Colonization (and infection) frequently begin at mucous
membranes
•These are found throughout the body. Consist of single or multiple layers of epithelial
cells, tightly packed cells in direct contact with the external
_____________________________.
Bacteria may
associate loosely
or firmly
Breaches in the
______________
_ barrier can
result in infection
(pathogenesis)by
opportunistic
pathogens
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UPPER RESPIRATORY TRACT – AND LOWER RESPIRATORY TRACT
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COMMON SKIN BACTERIUM MAY BE NEW OPPORTUNISTIC PATHOGEN*
•Helococcus kunzii is a recently identified bacterium that is thought to be a nonpathogenic member of normal human skin flora and is rarely associated with skin infections. In the study though, the researchers report the isolation of the organism from an infected cyst on the breast of a 57-year-old immunocompromised woman.
• Finding provides further support for the opportunistic role of H. kunzii in causing infection in both immunosuppressed and immunocompetent patients," say the researchers.•A.H. Chagla, A.A. Borczyk, R.R. Facklam, and M. Lovgren. 1998. Breast abscess associated with Helocococcus kunzii. Journal of Clinical Microbiology. 36:2377-2379.)
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• E. coli is the best known bacterium that regularly associates itself with humans, being an invariable component of the human intestinal tract. Even though E. coli is the most studied of all bacteria, and we know the exact location and sequence of 4,288 genes on its chromosome, we do not fully understand its ecological relationship with humans
ASSOCIATIONS BETWEEN HUMANS AND THE NORMAL FLORA
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• Sometimes the relationship between a member of the normal flora an its host cannot be deciphered. Such a relationship where there is no apparent benefit or harm to either organism during their association is referred to as
a commensal relationship. Many of the normal flora that are not predominant in their habitat, even though always present in low numbers, are thought of as commensal bacteria. However, if a presumed commensal relationship is studied in detail, parasitic or mutualistic characteristics often emerge.
COMMENSAL RELATIONSHIP.
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NORMAL FLORA ARE MUTUALISTIC• Much is not known about the nature of the associations between
humans and their normal flora, but they are thought to be dynamic interactions rather than associations of mutual indifference. Both host and bacteria are thought to derive benefit from each other, and the associations are, for the most
part, mutualistic. The normal flora derive from their host a steady supply of nutrients, a stable environment, and protection and transport. The host obtains from the normal flora certain nutritional and digestive benefits, stimulation of the development and activity of immune system, and protection against colonization and infection by pathogenic microbes.
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NORMAL FLORA OF THE GASTROINTESTINAL TRACT (GIT)
• In bottle-fed infants
• Bifidobacteria are not predominant. When breast-fed infants are switched to a diet of cow's milk or solid food, bifidobacteria are progressively joined by:
1. Enterics
2. Bacteroides
3. Enterococci
4. Lactobacilli
5. Clostridia
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NORMAL MICROBIAL FLORA OF THE GASTROINTESTINAL TRACT
• Functions and Products of Intestinal Flora• Intestinal microbes carry out a variety of
essential metabolic reactions that produce various compounds
• The type and amount produced is influenced by the composition of the intestinal flora and the diet
• Compounds produced include
• vitamins B12 and K
• gas
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THE FLORA OF THE LARGE INTESTINE (COLON)
1. Enterococci2. Clostridia 3. lactobacilli 4. Bacteroides 5. Bifidobacterium (Bifidobacterium
bifidum)6. Escherichia coli 7. Methanogenic bacteria 8. Viridans streptococci
9. Staphylococcus sp.
10. Proteus sp.
11. Candida albicans (Yeast)12. Mycoplama sp.
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NORMAL FLORA OF THE RESPIRATORY TRACT
A) The nares (nostrils)
1. Staphylococcus epidermidis 2. Corynebacterium3. Staphylococcus aureus
4. Neisseria sp.
5. Haemophilus sp
6. Streptococcus pneumoniae
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NORMAL FLORA OF THE RESPIRATORY TRACT
B) The upper respiratory tract (nasopharynx).
1. Non-hemolytic streptococci2. Alpha-hemolytic streptococci3. Neisseria sp.4. Streptococcus pneumoniae5. Streptococcus pyogenes6. Hemophilus influenzae7. Neisseria meningitidis
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NORMAL FLORA OF THE RESPIRATORY TRACT
• C) The lower respiratory tract (trachea, bronchi, and pulmonary tissues):
• Usually sterile.
• The individual may become susceptible to infection by pathogens descending from the nasopharynx e.g.
• H. influenzae
• S. pneumoniae).
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NORMAL FLORA OF THE HUMAN ORAL CAVITY
• Oral bacteria include:
1. Viridans streptococci2. Lactobacilli
3. Staphylococci (S. aureus and S. epidermidis)
4. Corynebacterium sp.
5. Bacteroides sp.
6. Streptococcus sanguis (dental plaque)
7. Streptococcus mutans (dental plaque)
8. Actinomyces sp.
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SITES OF HUMAN BODY THAT THE NORMAL FLORA
MICROBES COLONIZE• Respiratory tract and head
• outer ear, eye, mouth, oropharynx, nasopharynx
• Sterile sites: sinuses, middle ear, brain, lower respiratory tract (trachea, bronchiole, lung)
• Gastrointestinal tract
• esophagus, stomach, small intestine, large intestine
• Genitourinary system
• anterior urethra, vagina
• Sterile sites: bladder, cervix, uterus
• Skin
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• Especially in hosts rendered
susceptible by:
• 1. Immuno-suppression
(AIDS & SCID)
• 2. Radiation therapy &
Chemotherapy
• 3. Perforated mucous
membranes
• 4. Rheumatic heart
disease…etc.
NORMAL FLORA MAY ACT AS OPPORTUNISTIC PATHOGENS
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Sterile tissues
In a healthy human, the internal tissues such as:
• blood• brain
• muscle
• cerbrospinal fluid (csf.)
are normally free of microorganisms.
Normal Flora absent in …
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1. They constitute a protective host defense mechanism
by occupying ecological niches.
Importance of The Normal Flora (Advantages)
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NORMAL FLORA OF THE SKIN
• The most important sites are:
1.Axilla
2.Groin
3.Areas between the toes
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The oral flora contribute to immunity by inducing low levels of circulating and secretory antibodies that may cross react with pathogens.
IMPORTANCE OF THE NORMAL FLORA (ADVANTAGES)
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1. They can cause disease in the following:a) When individuals become immunocompromised or debilitated.b) When they change their usual anatomic location.
IMPORTANCE OF THE NORMAL FLORA (DISADVANTAGES)
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FECAL BACTERIOTHERAPY• Fecal bacteriotherapy, which is now officially and
scientifically known as fecal micro biota transplantation and is also referred to as fecal micro biota therapy, fecal transfusion, fecal transplant, stool transplant, fecal enema or human probiotic infusion (HPI), is a medical treatment for patients with pseudomembranous colitis (caused by Clostridium difficile), or ulcerative colitis that involves restoration of colon homeostasis by reintroducing normal bacterial flora from stool obtained from a healthy donor.
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• Fecal micro biota transplantation (FMT) -- also known as fecal bacteriotherapy, among other names -- is an effort to calm a troubled bowel by reintroducing the vast diversity of collaborative bowel inhabitants after the usual mix has been disturbed. More than 1,000 different strains of bacteria co-exist peacefully in the typical healthy bowel. But when the delicate balance is altered, by antibiotics or other causes, a few strains can become dominant, leading to severe diarrhea, inflammation and tissue damage.
FECAL MICRO BIOTA TRANSPLANTATION
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• Like an organ transplant, fecal microbiota transplantation begins with finding a donor, often a family member. The treatment team collects a fresh stool sample, at least 200 to 300 grams. The sample is mixed with salt water in a blender and filtered to remove particulate matter. It can be administered to the recipient through a colonoscopy, as an enema, or -- when the inflamed region is higher in the colon -- through a naso-gastric tube.
MICROBIOTA TRANSPLANTATION
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• Programme created by Dr.T.V.Rao MD for Medical and Paramedical students in the
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