M
MICROBIOLOGY & PARASITOLOGY
C3
MIDTERMS NORMAL FLORA OF THE HUMAN BODY
MICROBIAL ECOLOGY environment
- Ecology is the study of the relationships
between microorganisms and their
environment.
NORMAL FLORA Normal Flora found on skin
- Normal flora consists of the group of organisms Staphylococcus Major skin inhabitant,
that inhabit the body of a normal healthy epidermidis comprising
individual in the community. approximately 90% of
- may be non-pathogenic or pathogenic and may resident aerobic flora
at times behave as opportunistic pathogens. Staphylococcus Most commonly found
- inhibit the growth of pathogenic organisms by aureus in nose and perineum;
priming the immune system of newborns. in the nose, number
- protects the body's organs and systems that varies with age
are in direct contact with the external (greater in newborns
environment than in adults)
- subject to the attack of invasive organisms. Micrococci Accounts for 20%-
- synthesize important vitamins that are (Micrococcus 80% of micrococci in
essential to humans luteus) the skin
- secretes vitamin K for clotting factors Diphtheroids Classified into:
- Two types: (Coryneforms) lipophilic (common in
o Resident flora: organisms that are axilla) or non-
relatively of fixed types and are regularly lipophilic (more
found in a given area of the body at a common on glabrous
given age. or hairless skin such
o Transient flora: inhabit the skin and as palms of hands)
mucous membrane temporarily for hours,
days, or weeks and are derived from the Anaerobic
environment. diphtheroids
Other benefits of Normal Flora (Propionibacterium
1. Normal flora can prevent pathogenic acnes) - areas
organisms from attaching to and penetrating rich in sebaceous
the skin and other tissues by producing glands
mucin which make it difficult for the Gram-negative Seen in moist
pathogenic organisms to attach to the tissues Bacilli intertriginous areas
to produce disease. (Enterobacter, such as toe webs and
2. Normal flora in the intestines aid in the Klebsiella, axilla
digestion of food by producing enzymes such Escherichia coli,
as cellulase, galactosidase, and glucosidase. and Proteus spp.)
3. Intestinal flora also help in the metabolism of Nail Flora Similar to that of the
steroids. skin
NORMAL FLORA IN DIFFERENT BODY REGIONS Fungi may also be
Skin present (Aspergillus,
- Most exposed in microorganisms Penicillium,
- Factors that eliminate transient flora in Cladosporium,
skin: Mucor)
o Lysozyme in skin Micrococcus, Other bacteria found
o Acidic pH of the skin Acinetobacter, on skin
o Sweat Brevibacterium;
o Free fatty acids in sebaceous secretions Candida (fungus),
o Constant sloughing off of the skin and Malassezia
- Consists mainly of bacteria and fungi (fungus)
- Microorganisms are found on superficial layer
stratum corneum and hair follicles Mouth
Regions of Skin - Abundant moisture, warmth, and the constant
Axilla, perineum, toe - Higher moisture presence of food make the mouth an ideal
webs levels environment that supports very large and
- Has more diverse microbial populations on the tongue,
microorganisms cheeks, teeth, and gums.
compared to others - Biting, chewing, tongue movements, and
- Higher levels of salivary flow dislodge microbes. Saliva contains
surface lipids several antimicrobial substances.
- Predominantly - Tongue and buccal mucosa are mostly
inhibited by gram- inhabited by:
negative bacilli o Streptococcus Viridans Group
Hand, Face, Trunk - Has diverse flora S. mutans,
Upper arms, Legs because of their S. milleri,
exposure to the S. salivarius,
Hannah Adan 1
, M
MICROBIOLOGY & PARASITOLOGY
C3
MIDTERMS NORMAL FLORA OF THE HUMAN BODY
S. sanguis. diphtheroids, Propionibacterium,
Corynebacterium, streptococci, and
NOTE Micrococcus
- Although they are part of the
normal flora of the mouth, the Digestive Tract
viridans streptococci have been Esophagus
implicated in the pathogenesis - Contains transient mouth flora
of dental caries.
- The gingival crevices and the tonsillar crypts
are primarily inhabited by anaerobic flora.
Stomach
Other microorganisms found in mouth - Minimal bacteria
Lactobacillus, Actinomyces, Bacteroides, only because of
Veillonella, Neisseria, Haemophilus, the hostile
Fusobacterium, Treponema, environment in
Staphylococcus, Corynebacterium, and the stomach
Candida (fungus) - Bacteria that in
the stomach are
Nose and Throat (Upper Respiratory System) those that may
- The normal flora be swallowed
of the pharynx with the food or
and trachea are those that are dislodged from the mouth.
similar to those - Certain bacteria are able to survive the acidic
found in the oral environment of the stomach
cavity. o Helicobacter pylori
- There may most common cause of duodenal
transient flora in ulcer.
pharynx that is Produces urease that causes
potentially alkalinization of the gastric acid
pathogenic that enables them to colonize the
Haemophilus influenzae, stomach
Streptococcus pneumoniae, Small Intestine
Neisseria meningitidis, - scanty flora may
Mycoplasma. be found due to
- Although some normal microbiota are potential the constant
pathogens, their ability to cause disease is peristaltic
reduced by microbial antagonism. movement of the
- Nasal secretions kill or inhibit many microbes, intestines
and mucus and ciliary action remove many - Most of the
microbes bacteria cultured
Other microorganisms found in nose and in the small
throat intestine include:
Staphylococcus aureus, S. epidermidis, (all transient)
and aerobic diphtheroids in the nose; S. o streptococci,
epidermidis, S. aureus, diphtheroids, o lactobacilli,
Streptococcus pneumoniae, o Bacteroides
Haemophilus, and Neisseria in the throat
Large Intestine
Eyes (Conjunctiva) - The large intestine contains the largest
- The normal flora in the conjunctivae are very numbers of resident microbiota in the body
scanty because they are held in check by the because of its available moisture and nutrients.
flow of tears that contain lysozyme. - Mucus and periodic shedding of the lining
- The lysozyme may interfere with the cell wall prevent many microbes from attaching to the
synthesis of organisms. lining of the gastrointestinal tract, and the
- some bacteria may transiently colonize mucosa produces several antimicrobial
the conjunctiva chemicals
o Neisseria, - The colon is inhabited predominantly by
o Moraxella anaerobes (95%-99%) which includes:
o Corynebacterium o Bacteroides fragilis (most common),
o Staphylococci and streptococci o Bifidobacterium/Lactobacillus
- The conjunctiva, a continuation of the skin or bifidum (predominant in breast-fed
mucous membrane, contains basically the infants),
same microbiota found on the skin. o Eubacterium,
- Tears and blinking eliminate some microbes or o Peptostreptococcus,
inhibit others from colonizing o Clostridium.
- About 1%-4% of the flora of the colon are
Other microorganisms found in eyes facultative aerobes, predominantly
Staphylococcus epidermidis, S. aureus,
Hannah Adan 2
MICROBIOLOGY & PARASITOLOGY
C3
MIDTERMS NORMAL FLORA OF THE HUMAN BODY
MICROBIAL ECOLOGY environment
- Ecology is the study of the relationships
between microorganisms and their
environment.
NORMAL FLORA Normal Flora found on skin
- Normal flora consists of the group of organisms Staphylococcus Major skin inhabitant,
that inhabit the body of a normal healthy epidermidis comprising
individual in the community. approximately 90% of
- may be non-pathogenic or pathogenic and may resident aerobic flora
at times behave as opportunistic pathogens. Staphylococcus Most commonly found
- inhibit the growth of pathogenic organisms by aureus in nose and perineum;
priming the immune system of newborns. in the nose, number
- protects the body's organs and systems that varies with age
are in direct contact with the external (greater in newborns
environment than in adults)
- subject to the attack of invasive organisms. Micrococci Accounts for 20%-
- synthesize important vitamins that are (Micrococcus 80% of micrococci in
essential to humans luteus) the skin
- secretes vitamin K for clotting factors Diphtheroids Classified into:
- Two types: (Coryneforms) lipophilic (common in
o Resident flora: organisms that are axilla) or non-
relatively of fixed types and are regularly lipophilic (more
found in a given area of the body at a common on glabrous
given age. or hairless skin such
o Transient flora: inhabit the skin and as palms of hands)
mucous membrane temporarily for hours,
days, or weeks and are derived from the Anaerobic
environment. diphtheroids
Other benefits of Normal Flora (Propionibacterium
1. Normal flora can prevent pathogenic acnes) - areas
organisms from attaching to and penetrating rich in sebaceous
the skin and other tissues by producing glands
mucin which make it difficult for the Gram-negative Seen in moist
pathogenic organisms to attach to the tissues Bacilli intertriginous areas
to produce disease. (Enterobacter, such as toe webs and
2. Normal flora in the intestines aid in the Klebsiella, axilla
digestion of food by producing enzymes such Escherichia coli,
as cellulase, galactosidase, and glucosidase. and Proteus spp.)
3. Intestinal flora also help in the metabolism of Nail Flora Similar to that of the
steroids. skin
NORMAL FLORA IN DIFFERENT BODY REGIONS Fungi may also be
Skin present (Aspergillus,
- Most exposed in microorganisms Penicillium,
- Factors that eliminate transient flora in Cladosporium,
skin: Mucor)
o Lysozyme in skin Micrococcus, Other bacteria found
o Acidic pH of the skin Acinetobacter, on skin
o Sweat Brevibacterium;
o Free fatty acids in sebaceous secretions Candida (fungus),
o Constant sloughing off of the skin and Malassezia
- Consists mainly of bacteria and fungi (fungus)
- Microorganisms are found on superficial layer
stratum corneum and hair follicles Mouth
Regions of Skin - Abundant moisture, warmth, and the constant
Axilla, perineum, toe - Higher moisture presence of food make the mouth an ideal
webs levels environment that supports very large and
- Has more diverse microbial populations on the tongue,
microorganisms cheeks, teeth, and gums.
compared to others - Biting, chewing, tongue movements, and
- Higher levels of salivary flow dislodge microbes. Saliva contains
surface lipids several antimicrobial substances.
- Predominantly - Tongue and buccal mucosa are mostly
inhibited by gram- inhabited by:
negative bacilli o Streptococcus Viridans Group
Hand, Face, Trunk - Has diverse flora S. mutans,
Upper arms, Legs because of their S. milleri,
exposure to the S. salivarius,
Hannah Adan 1
, M
MICROBIOLOGY & PARASITOLOGY
C3
MIDTERMS NORMAL FLORA OF THE HUMAN BODY
S. sanguis. diphtheroids, Propionibacterium,
Corynebacterium, streptococci, and
NOTE Micrococcus
- Although they are part of the
normal flora of the mouth, the Digestive Tract
viridans streptococci have been Esophagus
implicated in the pathogenesis - Contains transient mouth flora
of dental caries.
- The gingival crevices and the tonsillar crypts
are primarily inhabited by anaerobic flora.
Stomach
Other microorganisms found in mouth - Minimal bacteria
Lactobacillus, Actinomyces, Bacteroides, only because of
Veillonella, Neisseria, Haemophilus, the hostile
Fusobacterium, Treponema, environment in
Staphylococcus, Corynebacterium, and the stomach
Candida (fungus) - Bacteria that in
the stomach are
Nose and Throat (Upper Respiratory System) those that may
- The normal flora be swallowed
of the pharynx with the food or
and trachea are those that are dislodged from the mouth.
similar to those - Certain bacteria are able to survive the acidic
found in the oral environment of the stomach
cavity. o Helicobacter pylori
- There may most common cause of duodenal
transient flora in ulcer.
pharynx that is Produces urease that causes
potentially alkalinization of the gastric acid
pathogenic that enables them to colonize the
Haemophilus influenzae, stomach
Streptococcus pneumoniae, Small Intestine
Neisseria meningitidis, - scanty flora may
Mycoplasma. be found due to
- Although some normal microbiota are potential the constant
pathogens, their ability to cause disease is peristaltic
reduced by microbial antagonism. movement of the
- Nasal secretions kill or inhibit many microbes, intestines
and mucus and ciliary action remove many - Most of the
microbes bacteria cultured
Other microorganisms found in nose and in the small
throat intestine include:
Staphylococcus aureus, S. epidermidis, (all transient)
and aerobic diphtheroids in the nose; S. o streptococci,
epidermidis, S. aureus, diphtheroids, o lactobacilli,
Streptococcus pneumoniae, o Bacteroides
Haemophilus, and Neisseria in the throat
Large Intestine
Eyes (Conjunctiva) - The large intestine contains the largest
- The normal flora in the conjunctivae are very numbers of resident microbiota in the body
scanty because they are held in check by the because of its available moisture and nutrients.
flow of tears that contain lysozyme. - Mucus and periodic shedding of the lining
- The lysozyme may interfere with the cell wall prevent many microbes from attaching to the
synthesis of organisms. lining of the gastrointestinal tract, and the
- some bacteria may transiently colonize mucosa produces several antimicrobial
the conjunctiva chemicals
o Neisseria, - The colon is inhabited predominantly by
o Moraxella anaerobes (95%-99%) which includes:
o Corynebacterium o Bacteroides fragilis (most common),
o Staphylococci and streptococci o Bifidobacterium/Lactobacillus
- The conjunctiva, a continuation of the skin or bifidum (predominant in breast-fed
mucous membrane, contains basically the infants),
same microbiota found on the skin. o Eubacterium,
- Tears and blinking eliminate some microbes or o Peptostreptococcus,
inhibit others from colonizing o Clostridium.
- About 1%-4% of the flora of the colon are
Other microorganisms found in eyes facultative aerobes, predominantly
Staphylococcus epidermidis, S. aureus,
Hannah Adan 2
