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NORMAL FLO
RA OF
BODY
DR
YU
GA
ND
AR
WHAT IS NORMAL FLORA ?
mixture of microorganisms regularly
found at on / within the body of a healthy person.
Some of these microorganisms are found in association with humans / animals
only.
Normal Flora• Definition
Normal flora is the mixture
of microorganisms (bacteria
and fungi) that are regularly
found at any anatomical site
of human body
ROLE OF NORMAL FLORA
Immunostimulation
a) They produce antibodies which may contribute to host defenses.b) Some of these antibodies may
cross react with normal tissue components.
May be source of opportunistic infections
e.g : In Patients with impaired defense Mechanisms
Protection from External Invaders a) Because of the normal flora occupy bodys
epithelial surfaces,they are able to prevent other bacteria by blocking receptors
b) competing for essential nutrients c) producing anti-bacteria substances
e.g : Fatty acids, peroxides , Bacteriocins.Nutrition Some of the normal intestinal flora e.g. E. coli & Bacteroids produce Vitamin K in the gut
which is available for use by host.
Production of Carcinogens
Some normal flora may modify, through their enzymes, some chemicals in our diets into carcinogens
e.g. Artificial sweeteners may be enzymatically
modified into bladder carcinogens.
Stimulate development of certain tissues:
Caecum and lymphatic tissues (Peyer’s patches) in GIT
ORIGIN OF NORMAL FLORA
Healthy fetus, in utero, is essentially free of MOs
Infant exposed immediately to MOs when passing
through mothers vaginal tract and then to MOs in
environment
Within few hours, oral and nasopharyngeal flora of
neonate established
Within one day, resident flora of lower intestinal
tract established
NORMAL FLORA
Human body 1013 cells 1014 bacteria
Numbers represent the number of organisms per gram of homogenized tissue or fluid or per square centimeter of skin surface.
NORMAL FLORA OF SKIN
Human adult has 2 square meters of skin
Overall, a hostile environment toward bacteria
Eccrine (simple sweat) glands release Nacl solution : hyperosmotic surface
Apocrine glands : sweat & nutrients,secrete lactic acid pH3-5
Sebaceous glands : a/w hair follicles secrete lipids ,bacteria convert it into unsaturated fatty acids which have antimicrobial activity and
strong odor
MOs that normally live on or in any part of the body
with out causing disease
Two basic types of NF:
Resident NF – normally GROW on/in indicated body site,
presence fixed in body
Transient NF – only TEMPORARILY PRESENT on/in
indicated body site, usually don’t become firmly
attached but simply die within hours
NORMAL FLORA OF SKIN
Transient microbes: in contact with environment
Resident microbes Areas of high moisture content
Axilla, groin, toe webs, perineum, scalp Superficial layers of the epidermis, upper parts of hair follicles, sebaceous glands
Staph epidermidis; Staph aureus; Corynebacteria (Propionibacterium acnes); Streptococci; Clostridium spp. (perineum and upper thighs)
Skin: 3 main micro environments
Axilla, perineum, toe webs
Hands, face and trunk
Upper arms and legs
S. epidermidis
Major inhabitant making up more than 90% of the flora
S. aureus
Nose, perineum, vulva skin
Occurrence in nasal passages varies with age being greatest in
newborns, less in adults
Neither profuse sweating nor washing significantly modifies normal
skin flora
Soap or disinfectant (hexachlorophene) diminish microbial population Soap - 30 second scrubbing
Soap: physically removes organisms Disinfectants: bactericidal
But NF rapidly replenished from sebaceous and sweat glands
Pathogenic organisms eliminated (?)
Re-exposure needed to colonize
Nosocomial infections dramatically diminished or eliminated
Antiseptics applied to the skin, as in the preparation of operation sites
generally remove the transient flora and reduce the resident organisms
Key organisms to learn in skin –
Staphylococcus epidermidis (coagulase-negative
staphylococci);
Propionibacterium sp.,
Corynebacterium sp.
SKIN NORMAL FLORA
Staphylococcus epidermidis
Staphylococcus aureus
C+, clusters
SKIN NORMAL FLORA
Propionibacterium acnes
B+, anaerobic
Diphteroids (club shaped)
Branching bacilli
SKIN NORMAL FLORA
Candida albicans
Yeast, budding
Soil & air
SKIN NORMAL FLORA
Streptococcus species
C+, pairs, chains
SKIN NORMAL FLORA
Corynebacterium
B+, aerobic
Diphtheroids
Numerous bacterial colonies on blood agar plate after swabbing from normal human skin
Staphylococcus aureus, a predominant normal microflora of skin.
HUMAN BENEFITS FROM NORMAL FLORA
Prevention of colonization by more pathogenic species
(colonization resistance).
Competition for receptors (tropism)
Competition for nutrients (interference)
Direct antagonism through bacteriocins, toxic chemical byproducts
Example of protective effect
Normal mouse - requires ~106 Salmonella to become infected
Germ free mouse - infectious dose is ~10 Salmonella
Competitive Protective Role of Normal Microflora
Kloos and Schleifer scheme, Baird–Parker system for
classifying staphylococci and micrococci
Kloos and Schleifer : Staph species are able to produce
acid aerobically from glycerol in the presence of
erythromycin
they are sensitive to lysostaphin and nitrofuran at defined
concentrations, whereas Micrococcus species are not.
NORMAL FLORA - CONJUNCTIVA
Variety of bacteria: low numbers present
High moisture
Blinking mechanically removes bacteria
Lachrymal secretions include lysozyme
Staph epidermidis and Propoinibacterium acnes dominate
Staph aureus, Haemophilus sp. and Neisseria sp.
occasionally found
NORMAL FLORA - RESPIRATORY TRACT
Nares (nostrils)
20% of human population are carriers for Staphylococcus aureus Staphylococcus epidermidis and corynebacteria
Nasopharynx (above soft palate)
Small numbers of Streptococci, Neisseria spp., Haemophilus
influenzae Strep pneumoniae, Strep pyogenes, Haemophilus influenzae, Neisseria meningitidis, Mycoplasma spp.,
pneumococci, Bordetella pertussis, C.diphtheriae
Oropharynx: between soft palate and upper edge of epiglottis
Large numbers of Staphylococcus aureus and S. epidermidis
Alpha-hemolytic streptococci, diphtheroids, Neisseria sp
NORMAL FLORA OF LOWER RT
Usually sterile
Ciliated epithelium
Mucus blanket: entrapment
Removed by coughing, sneezing
Contains lysozyme
Alveolar macrophages If breached: opportunistic infections, H. influenzae,
Streptococcus pneumoniae,
Ecology : Normal flora of Oral Cavity
Birth: sterile mouth
Neonate Within 4-12 hours (lactobacilli, streptococci)
Colonized from environment (especially first feeding)
Streptococcus salivarius, staphylococci, Neisseriae, Moraxella
catarrhalis
Normal flora of Oral Cavity
NORMAL FLORA OF ORAL CAVITY
Teeth appear Tooth is nondesquamating surface
Streptococcus mutans, Streptococcus parasanguis Gingival crevice area (supporting structures of teeth)
Anaerobic species, yeasts
Puberty Bacteroides, spirochetes
108 bacteria/mL of saliva; potentially >700 species
ORAL & OP NORMAL FLORA
Resist mechanical removal by adhering to various
surfaces such as gums and teeth
MOs that can’t resist mechanical flushing of oral cavity,
swallowed, destroyed by HCl in stomach
Comfortable environment for MOs due to availability of
water and nutrients
Key organisms to learn:
Mouth - Strep viridans (e.g. S. sanguis, salivarius, mutans, mitis)
Nose - Staphylococcus aureus
NORMAL FLORA - GASTROINTESTINAL TRACT
Ecology Birth: sterile
Breast-fed - Bifidobacteria species
Switch to cow’s milk
Bifidobacteria species joined Enteric, bacteroides, enterococci, lactobacilli and clostridia
Switch to solid food
Microflora similar to parents
GI ecology : Varies along the tract (longitudinal levels)
Varies along horizontal level: lumen vs. epithelium
Esophagus
Microbes associated with saliva and food
Stomach
Low pH limits population numbers (10 bacteria/ml) , Helicobacter
pylori, acid-tolerant lactobacilli
Reduction of acidity (increase alkalinity)
Increases population of resident flora
Small intestine Proximal small intestine (duodenum and jejunum)
Sparse (<103 bacteria/ml fluid) due to acid from stomach,
bile and pancreatic secretions
Lactobacilli, Enterococcus faecalis Distal small intestine (ileum)
Increases (108 bacteria/ml) due to pH change
Lactobacilli, Enterococcus faecalis, coliforms,
Bacteroides, bifidobacteria
Large intestine 109-1011/ml
>350 species
E. coli = 0.1% of total population Primarily anaerobic
Facultative aerobes deplete oxygen Adult excretes 3x1013 bacteria/day
25%-35% of fecal mass = bacteria
NORMAL FLORA - GASTROINTESTINAL TRACT
Location (adult) Bacteria/gram
contents
duodenum 103-106
jejunum and ileum 105-108
cecum and transverse colon 108-1010
sigmoid colon and rectum 1011
In the normal adult colon, 96–99% of the resident
bacterial flora consists of anaerobes:
bacteroides species, especially B fragilis;
fusobacterium species;
anaerobic lactobacilli, e.g., bifidobacteria; clostridia
(C perfringens); and
anaerobic gram-positive cocci (Peptostreptococcus
species).
Site
skin
large intestine
vagina
Ratio of Anaerobes:
Aerobes
~ 1:1
1000:1
10:1
ANAEROBIC NORMAL FLORA
BACTERIAL PROCESSES OCCURRING IN GUT
Process Examples
Vitamin Synthesis Thiamine, riboflavin, pyridoxine, B12, K
Gas Production CO2, CH4, H2
Odor production H2S, NH3, amines, indole, butyric
Organic Acid production Acetic, propionic, butyric
Polysaccharide metabolism Extraction of calories from otherwise indigestible polysaccharides
Steroid metabolism Esterification, dehydroxylation, oxidation, reduction, inversion
Colonocyte nutrition - provides protection against cancer and ulcerative colitis. May affect obesity
Butyric Acid production, esp by Firmicutes (GP organisms).
Key colonizing organisms to learn:
Stomach - Helicobacter pylori
Colon -Facultative anaerobes - Escherichia coli, Enterococcus sp.
Obligate anaerobes - Bacteroides fragilis
Normal Flora of the Gastrointestinal Tract (GIT)
• In breast-fed Bifidobacteria account for more than 90% of the total intestinal bacteria.
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. Enterics2. Bacteroides3. Enterococci4. Lactobacilli5. Clostridia
Normal Flora of the Gastrointestinal Tract
(GIT)• The proximal small intestine
1.Lactobacilli2.Enterococcus
faecalis3.Coliforms4.Bacteroides
Normal Flora of the Gastrointestinal Tract (GIT)
In the upper GIT of adult humans
• mainly acid-tolerant lactobacilli
e.g. Helicobacter pylori
Recent studies have also shown that the composition of
your gut flora can also affect how much you weight.
Persons with more Firmacutes (primarily gram positive
organisms) are more obese than those with more
Bacteroides (primarily gram negative).
NORMAL FLORA OF UROGENITAL TRACT
Upper urinary tract (kidneys, ureters, bladder) usually sterile
Male anterior urethra
Low numbers (102-104/ml)
Staphylococcus epidermidis, Enterococcus faecalis,
Escherichia coli, Proteus Male anterior urethra Same as Skin + enteric + enterococcus
NORMAL FLORA OF UROGENITAL TRACT
Vagina: complex microbiota
At birth: glycogen,pH5(Lactobacillus spp.)Same as mother (PH 5)
Neonate (one month) to puberty - (pH neutral),Same as skin + enteric
+ strept (PH 7)
At puberty
L. acidophilus, corynebacteria, pepto streptococci, staphylococci,
streptococci, and Bacteroides L. acidophilus converts glycogen to lactic acid Lowers to pH 5
At menopause : return to prepuberty flora
Normal flora of the Urogenital Tract
a) The anterior urethra1. Staphylococcus
epidermidis2. Enterococcus faecalis3. Alpha-hemolytic
streptococci. 4. Some enteric bacteria
(e.g. E. coli, Proteus sp.)5. Corynebacteria sp.6. Acinetobacter sp.7. Mycoplasma sp.8. Candida sp.9. Mycobacterium
smegmatis
Normal flora of the Urogenital Tract
b) The vagina 1. Corynebacterium sp.2. Staphylococci3. Nonpyogenic
streptococci4. Escherichia coli5. Lactobacillus
acidophilus6. Flavobacterium sp.7. Clostridium sp.8. Viridans streptococci9. Other Enterobacteria
Key organism to learn in
GUT - Lactobacillus sp
LACTOBACILLUS SPP. FOUND IN UROGENITAL SYSTEM
HAIR FOLLICLES
inhabited by anaerobes (Propionibacterium sp)
in their deeper parts and nearer the surface aerobic cocci,Malassezia species of yeasts.
Propionibacteria are anaerobic, Grampositive, rod-shaped organisms,
P. acnes, and P. granulosum
widespread, follicles that have large sebaceous glands
over the face and upper trunk.
both been associated with acne lesions
The third species, P. avidum, is found in moist sites,
particularly the axillae and groins. Its pathogenic
potential unclear
Propionibacterium species require the increased skin
lipid levels of puberty before becoming established
Present at very low levels before the onset of puberty.
Propionibacterium acnes & Gram-positive cocci are
capable of hydrolysing lipids of sebum to produce
free fatty acids
The acidic milieu which results inhibits the growth of
other organisms such as Streptococcus pyogenes
NORMAL FLORA OF EAR
External auditory meatus
In addition to coagulase-negative staphylococci and coryneforms
Proteus species, Escherichia coli, Neisseria,Psuedomonas
NORMAL FLORA OF EAR
Pseudomonas aeruginosa frequently isolated from ear
NORMAL FLORA OF AXILLA
supports a very high level of bacterial colonization
mostly staphylococci, micrococci and coryneforms
Propionibacterium acnes is usually present and
P. avidum is often found
NORMAL FLORA OF TOE CLEFTS
In shoe wearers, 4 toe cleft is often hyperhydrated and
the skin macerated.
large number of bacteria present
The toe web is an important site for Brevibacterium
species, and not surprisingly Acinetobacter species are often
isolated, as are Alkaligenes species.
In the elderly and in tropical Climates coliforms and other
organisms of the intestinal flora may be present
NORMAL FLORA OF UMBILICUS
The umbilicus of the newborn is frequently colonized by
Staphylococcus aureus shortly after birth
The umbilicus of the newborn may also be colonized by
Streptococcus pyogenes, and look normal
The organisms can readily spread from infant to infant in a
hospital nursery.
Searches for the source of infection in a maternity unit
should always include umbilical swabs from the babies.
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.
Importance of The Normal Flora
2. The oral flora of humans may harm their host since some of these bacteria are pathogens
NORMAL FLORA - RISKS AND OPPORTUNISTIC
Clinical conditions that may be caused by members of the normal flora
“viable microbial food supplement that beneficially influences the
health of the host”
Oral administration of living organisms to promote health
Mechanism speculative: competition with other bacteria;
stimulation of nonspecific immunity
Examples:
Lactobacillus augments protective gut barrier function against
diarrheagenic E. coli
Lactobacillus stimulate IgA secretion, providing protection
against pathogens such as rotavirus
.
PROBIOTICS
PREBIOTICS Non- digestible food ,Non essential food components used to affect microbial populations
Increases bifidobacteria and lactobacillus bacteria
Typically a carbohydrate: soluble fiber
(e.g. non digestible oligosaccharides)
Result in formation of short chain fatty acids that affect lymphocyte proliferation, cytokine production etc
ORGANISMS PER GRAM OF HOMOGENIZED TISSUE OR FLUID OR PER SQUARE CENTIMETER OF SKIN SURFACE
Noncolonized areas: Blood, body fluids, tissues,
internal organs Lower respiratory tract Upper urinary tract
Sterile tissuesIn a healthy human,
the internal tissues such as:
• blood• brain• muscle• cerbrospinal fluid
(csf.) are normally free of
microorganisms.
Normal Flora
GNOTOBIOLOGY
Gnotobiotic animals : “germfree”
Fetus is sterile Caesarean sections to obtain fetus
Fetus growing in sterile isolator
Not anatomically or physiologically normal
Poorly developed lymphoid system, thin intestinal wall, enlarged
caecum, low antibody titers
Die of intestinal atonia,Require vitamin K and B comp
No dental caries or plaque More susceptible to pathogens
WHY ARE ARMPITS SMELLY?
1. Anaerobic bacteria in the pit use sebum
from sweat glands to produce short
chain fatty acids
2. The sweat and sebum produced by the
pit is naturally aromatic
3. Use of deodorants with antibacterial
substances, inhibit growth of G(+), may
lead to growth of G(-) MOs and infection
WHAT DO YOU THINK HAPPENS TO THE FLORA ON YOUR SKIN WHEN IT IS COVERED WITH AN OCCLUSIVE BANDAGE FOR A FEW DAYS?
A waterproof plaster applied to a cut on the forearm
for one or two days causes an increase in the
resident population - increase in gram negative
bacilli
Removal of particlesincluding microorganismsby rapid passage of airover cilia in nasopharynx
Skin is a physical barrier,produces antimicrobial fattyacids, and its normal florainhibit pathogencolonization
Stomach acidity(pH 2) inhibitsmicrobial growth
Normal floracompete withpathogens
Flushing of urinarytract preventscolonization
Lysozyme in tears andother secretions dissolvescell walls
Mucus, cilia lining tracheasuspend and move micro-organisms out of the body
Mucus and phagocytesin lungs prevent colonization
Blood and lymphproteins inhibitmicrobial growth
Rapid pH changeinhibits microbialgrowth
Normal flora compete with pathogens in the gut
.
Methods of sampling :
Simple qualitative studies by swabbing
The number of organisms is increased by the duration of
rubbing, pressure exerted and moistening the swab
The best quantitative estimates of the total bacterial flora are
determined by applying an open-ended cylinder of known
cross sectional area to the skin, introducing a small,
known volume of suitable liquid vehicle and scrubbing
the surface of the skin to free the organisms
Full-thickness skin-biopsy material should be the best sample
Disposal of organisms can be studied quantitatively by air sampling techniques using either settle plates or an impaction
sampler
PCR
ISOLATION MEDIA
use of ordinary blood
serum agar for aerobic organisms
solid Brewer’s thioglycolate medium without indicator
1% Tween 80 indicator for Propionibacterium
acnes
VARIABLES AFFECTING NORMAL MICROFLORA - GENETICS
Relatedness of colonic bacterial flora in identical twins (even twins living apart) is higher
than that of unrelated persons, fraternal twins or married persons
VARIABLES AFFECTING NORMAL MICROFLORA - RACES
Racial differences have been demonstrated in the nasal carriage of S. aureus in children
white individuals being more likely carriers than black individuals
VARIABLES AFFECTING NORMAL MICROFLORA - AGE
Bacterial flora develops in orderly succession from birth
to stable adult flora : Example : mouth microflora
Infant - mouth sterile at birth
Rapidly develops flora, primarily from mother
Strep salivarius (on tongue); lactobacilli
Changes with eruption of teeth(Strep sanguis; mutans)
Ecologic system develops- micro environments of anaerobic
and aerobic flora
Neonates are covered with vernix caseosa contain the antimicrobial peptide cathelicidin
and also lysozyme,Skin is sterile
VARIABLES AFFECTING NORMAL MICROFLORA - GENDER AND STRESS
Gender - Examples
Presence of different mucosal surfaces (esp.
genitourinary)
Hormonal effects on flora in females - e.g. change in
vaginal flora with onset of puberty
Stress - Examples
Alterations in bowel flora recognized with severe stress
There is evidence that males carry higher numbers of bacteria, aerobic organisms than
females
Men are more likely to be disseminators of Staphylococcus aureus than females
VARIABLES AFFECTING NORMAL MICROFLORA - NUTRITION AND DIET OF HOST
Examples : Infant feeding
Breast-fed infants - GI flora is predominantly
Bifidobacterium sp. (anaerobic gram positive bacillus)
Bottle-fed infants - GI flora more closely resembles that of
adults (enteric gram negative bacilli, mixed anaerobes,
staph) Adult diets
Predominant species found in colonic flora differs among
vegetarians, fish eaters, and omnivores
Limburger cheese is made from the same bacteria (Brevibacterium sp.) that grow between your toes
NORMAL FLORA TRIVIA
NORMAL FLORAAcquired rapidly during & after birth
Reflects sex of person
Reflects environment of person
90% is S. epidermidis; S. aureus, may be in moist areas
Reflects genetics of person, nutrition of person, age of person
Changes continuously through out life
Protection against other bacteria
THANK YOU