Transcript Normal flora

NORMAL HUMAN
FLORA
Dr.T.V.Rao MD
DR.T.V.RAO MD
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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
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flora
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NORMAL BACTERIAL FLORA
• 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)
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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 =>
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Human body Area: the skin and mucous membranes
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Time: shortly after birth until death
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Number: 1014 bacteria =>1013 host cells
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2. Normal flora may:
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a. Aid the host
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b. Harm the host (in sometimes)
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c. Exist as commensals (no effect to the host)
3.
Viruses and parasites => NOT normal microbial flora
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Most investigators consider that they are not commensals and
do not aid the host.
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Normal Flora and Pathogenesis
Outcomes of exposure to a microorganism:
1. Transient colonization
2. Permanent colonization
3. Disease
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.
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SIGNIFICANCE OF NORMAL FLORA
•
1.The normal flora influences the anatomy, physiology,
susceptibility to pathogens, and morbidity of the host.
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2. The effect of the normal flora on the host was not well
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understood until germ-free animals became available.
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Cesarean Section => Germ-free animals => Isolators
w/o detectable pathogens (viruses, bacteria & others)
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3. Two interesting observations:
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a. the germ-free animals lived almost twice as long as
their conventionally maintained counterparts.
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b. the major causes of death were different in the
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two groups.
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FACTORS INFLUENCING
NORMAL FLORA
1. Local Environment (pH,
temperature, redox
potential, O2, H2O, and
nutrient levels…).
2. Diet
3. Age
4. Health condition
(immune activity…)
5. Antibiotics,…..etc
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Significance of Normal Flora
Normal flora may aid the host in several ways:
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Aid in digestion of food
•
Help the development of mucosa immunity
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Protect the host from colonization with
pathogenic microbes.
106
pathogenic
w/ normal flora microbes
10 pathogenic
microbes
w/ reduced flora after
Streptomycin treatment
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GI infection
GI infection
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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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WHEN WE GET COLONIZED WITH
NORMAL FLORA
• 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.
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A NEW BORN CHILD'S FLORA IS
DEPENDENT ON MOTHER
• 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
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DENSITY OF NORMAL FLORA IN
HUMANS
• It has been calculated that a
human adult houses about 10 12
bacteria on the skin, 10 10 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.
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Normal Flora
• Resident flora
• Reflects sex
of person
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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
_____________________________.
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Bacteria may
associate loosely
or firmly
Breaches in the
_______________
barrier can result
in infection
(pathogenesis)by
opportunistic
pathogens 18
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.
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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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ASSOCIATIONS BETWEEN HUMANS AND THE
NORMAL FLORA
• 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
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COMMENSAL RELATIONSHIP.
•
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.
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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.
2.
3.
4.
5.
Enterococci
Clostridia
lactobacilli
Bacteroides
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. Corynebacterium
3. 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 streptococci
2. Alpha-hemolytic streptococci
3. Neisseria sp.
4. Streptococcus pneumoniae
5. Streptococcus pyogenes
6. Hemophilus influenzae
7. 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
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Oral bacteria include:
1. Viridans streptococci
2. 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
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Respiratory tract and head
outer ear, eye, mouth, oropharynx, nasopharynx
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Sterile sites: sinuses, middle ear, brain, lower
respiratory tract (trachea, bronchiole, lung)
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Gastrointestinal tract
•
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esophagus, stomach, small intestine, large intestine
Genitourinary system
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anterior urethra, vagina
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Sterile sites: bladder, cervix, uterus
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Skin
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NORMAL FLORA MAY ACT AS
OPPORTUNISTIC PATHOGENS
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Especially in hosts
rendered susceptible by:
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1. Immuno-suppression
(AIDS & SCID)
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2. Radiation therapy &
Chemotherapy
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3. Perforated mucous
membranes
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4. Rheumatic heart
disease…etc.
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Normal Flora absent in …
Sterile tissues
In a healthy human, the
internal tissues such as:
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blood
•
brain
•
muscle
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cerbrospinal fluid (csf.)
are normally free of
microorganisms.
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Importance of The Normal Flora
(Advantages)
1.
They constitute a
protective host
defense
mechanism
by occupying
ecological niches.
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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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IMPORTANCE OF THE NORMAL FLORA
(ADVANTAGES)
The oral flora
contribute to
immunity by
inducing low levels
of circulating and
secretory
antibodies that
may cross react
with pathogens.
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IMPORTANCE OF THE NORMAL FLORA
(DISADVANTAGES)
1. They
can
cause
disease in the following:
a) When individuals
become
immunocompromised or
debilitated.
b) When they change
their usual anatomic
location.
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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
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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 coexist 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.
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MICROBIOTA TRANSPLANTATION
• 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.
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• Programme created by Dr.T.V.Rao MD for
Medical and Paramedical students in the
Developing World
•
Email
[email protected]
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