1.
NORMAL FLORA OF HUMAN BODY
PRESENTED BY PRANZLY

2.
• Normal flora are the microorganisms that live on another living Organism
for example (human or animals) or in--animate object without causing
disease.
• The mixture of Organism regularly found at any anatomical site referred to
as normal flora
• Also known as Indigenous microbiota
• They consist of few eukaryotic fungi and protest but bacteria are the most
numerous and obvious microbial component of normal flora
• The human body which contains 1013 cells routinely harbours 1014 bacteria
these bacteria population constitute the normal microflora
INTRODUCTION

3.
TYPES
RESIDENT MICROFLORA
•inhabits for extended period
•consists of relatively fixed type of
microorganism regularly found in
given area at a given age
• if disturb it promptly re-
establishes itself
•Example- found in upper
respiratory tract, nose, mouth,
bronchi, trachea, epiglottis
TRANSIENT MICROFLORA
inhabits temporarily
consist of non pathogenic or
potentially pathogenic
microorganisms that inhabit the
skin or mucous membrane for
hours days weeks
it is derived from the environment
does not produce disease and
does not establish itself
permanently on the surface
if resident flora is
disturbed transcend
flora may colonize
Proliferate and
produce disease

4.
ASSOCIATION BETWEEN HUMAN AND NORMAL FLORA
• , • .
1. There is a dynamic interaction rather than association mutual indifference both host
and bacteria are thought deserve benefits from each other and their association is
MUTUALISTIC
HUMAN
nutritional and digestive benefits
stimulation of development of
activity immune system
protection against colonization and
infection by pathogenic microbes
NORMAL FLORA
supply nutrients
stable Environment
Protection and transport
2. Benefits some of them are PARASITIC Live at the expense of their host
and 3. some are PATHOGENIC capable of producing disease
• Disease produced by normal flora in their host are endogenous disease

5.
• Many endogenous bacterial disease are opportunistic
infection
the Organism must be given a special opportunity of weakness
or let down in the host defense in order to infect.
Example- chronic bronchitis in smokers due to weakened lungs
4. sometimes the relationship between a member of the normal
flora and the host cannot be deciphered (no apparent benefit or
harm to either Organism) is termed as COMMENSAL relationship
Example- it happens with the bacteria which are present in low
number

6.
CHARACTERISTICS OF NORMAL FLORA
1.TISSUE SPECIFICITY
• most members prefer to colonize certain tissue and not others and show
the phenomena of TISSUE TROPISM
Bacteria prefer certain tissue for growth host essential nutrients and growth
factors for bacterium like
o Suitable oxygen,
o pH and
o temperature for growth
Example- lactobacillus acidophilus Informally known as doderlein’s bacilli
colonized vagina, because glycogen produced in vagina provide the bacteria
the source of sugar which it ferments to lactic acid and thus results in the
lower pH.

7.
2. SPECIFIC ADHERENCE
• Host bacteria can colonize a specific tissue or side because they can adhere
to it which involves complementary chemical interaction between two
surfaces.
• The receptor on human cells or tissue are usually glycoprotein molecules
located on the host cell or tissue surface

8.
3. BIOFILM FORMATION
• some of the indigenous bacteria are able to construct biofilm on the tissue
surface or they are able to colonize a biofilm built by another bacterial species
• Biofilm usually occurs when one bacterial species attaches specifically or non
specifically to a surface and secrets carbohydrates slime (exopolymer) that
embeds the bacteria and attract other microbes to the biofilm for protection or
nutritional advantage.
Example- formation of dental plaque on the teeth
Plaque is a naturally constructed biofilm in which the consortia of bacteria may
reach a thickness of 300 to 500 cells on the surface of the teeth

9.
NORMAL FLORA OF SKIN
• the human is skin is constantly and continuously bombarded by Organism present in the
environment
Density and composition of normal flora of skin varies with the anatomical location
• the higher moisture content of axilla, groin area (between toes) have relatively high
density of bacterial cell as compared to other parts which is fairly low.
• most bacteria are sequestered in sweat glands
• skin microbes found in most superficial layer of the epidermis and upper part of the hair
follicles are gram positive (Staphylococcus and Micrococcus and Corynebacterium like
Propionibacterium
• Staphylococcus and Propionibacterium produce fatty acids that inhibit the growth of fungi
and yeast on the skin.
• If Propionibacterium become trapped in hair follicle it may grow rapidly and cause
inflammation and acne.

10.
NORMAL FLORA OF ORAL CAVITY
• The presence of nutrients secretion epithelium debris make it favorable.
• Oral bacteria include Streptococcus, Staphylococcus and Corynebacterium
• Streptococcus salivarius is dominant may make up to 98% of total oral flora
• The eruption of teeth leads to colonization of Streptococcus mutans
• The oral flora also show ANTAGONISM against non indigenous species by
production of inhibitory substances such as fatty acid, peroxides, bacteriocins.

11.
NORMAL FLORA OF CONJUNCTIVA
• The conjunctiva is relatively free from Organism due to the flushing action of
tears
• blinking wipes it every few seconds mechanically washing away foreign
objects including bacteria
• BLINKING wipes it every few seconds mechanically washing away foreign
objects including bacteria lacrimal secretion tears also contain bacterial
substances lysozyme
• Newborns are prone to bacterial infection
• Chlamydia and Neisseria might be present on cervical and vagina
• therefore SILVER NITRATE or antibiotic may put on new bonds to avoid
infection after passage through birth canal

12.
NORMAL FLORA OF RESPIRATORY TRACT
• Nasal are always colonized by Staphylococcus epidermis,
Corynebacterium and often with Staphylococcus aureus
• the healthy sinuses in contrast are sterile.
• Any bacteria reaching the lower Respiratory tract are swept upward by the
action of mucociliary blanket that line the bronchi to remove by coughing
sneezing swallowing etc.

13.
NORMAL FLORA OF GASTROINTESTINAL TRACT
• In humans there are difference in composition of flora which are influenced by
age diet culture condition and the use of antibiotics in upper GI tract of adult
humans
• The esophagus contain only bacteria swallowed with saliva and food
• Because of the high acidity of the gastric juice very few bacteria can be
cultured from normal stomach.
• Helicobacter pylori causes gastric ulcers and can also cause gastric and
duodenal cancer
• At birth the entire intestinal tract is sterile
• But bacteria enters with the first feed in breastfeed- there is 90% of
Bifodobacterium, Enterobacteriaceae and Enterococcus in a small proportion.

14.
NORMAL MICROFLORA OF UROGENITAL TRACT
• urine is sterile since the urinary tract is flushed with urine every few hours
microorganism not grow
• Anterior urethra is inhabited by Staphylococcus epidermidis, Enterococcus
faecalis and some alpha-hemolytic Streptococci
• during reproductive life from puberty to menopause the vaginal epithelium
contains glycogen due to the action of circulatory estrogens doderlein’s
bacillus also known as Lactobacillus acidophilus metabolized glycogen to
lactic acid and this is the protective effect of normal flora which prevents
the establishment of bacteria by resulting in lower pH.
• Mycobacterium smegmatis a harmless commensal is found in the smegma
of the genitalia of both men and women.
• During pregnancy there is an increase in Staphylococcus epidermidis ,
doderlein’s bacilli and yeasts.

15.
BENEFICIAL EFFECT OF NORMAL FLORA
 It synthesize and excrete vitamins-
o enteric bacteria produce vitamin K and B12.
o lactic acid bacteria produce vitamin B
 It prevents colonization of pathogen by competing for attachment sites or for
essential nutrients
 It antagonizes other bacteria through the production of substances which
inhibit or kill the non indigenous species
o they produce fatty acid peroxides to highly specific bacteriocins which
inhibit and kill other bacteria
 Production of natural antibodies and act as an antigen in animal which in turn
induce an immunological response
 they stimulate the development of certain tissue
o the cecum lymphatic tissue payers patches in the GI tract immunological
stimulation is poor in germ free animals

16.
HARMFUL EFFECT OF NORMAL FLORA
1. BACTERIAL SYNERGISM between members of normal flora and
potential pathogen one Organism help another to grow or survive and
this phenomena is known as cross feeding
• Example- staph-protected infection- penicillin resistant
Staphylococcus shares its resistance drug with other pathogen that
are otherwise susceptible to the drug come
2. Competition for nutrients-Bacteria absorbs some of the host nutrients
for their own needs
3. Introduction of a low grade toxemia minute amount of toxins example
endotoxins are found in circulation these stimulate natural antibodies
4. Maybe a agent of disease cause endogenous disease if they enter
compromised areas.

17.
DISEASE CAUSED BY NORMAL FLORA
1.DENTAL PLAQUE- Streptococcus sanguis and Streptococcus
mutans are responsible for plaque formation.
it is initiated by a weak attachment of streptococcal cells to the
salivary glycoproteins forming a pellicle on the surface of the teeth
2. DENTAL CARIES- the destruction of the enamel, cementum of the
teeth due to bacterial activities.
Plaque leads to the formation of lactic acid which de-mineralized
the enamel of the teeth