Microbial Ecology
study of the relationship between microorganisms and their environment
Normal flora
consists of the group of organisms that inhabit the body of a normal healthy individual in the community.
indigenous flora
may be non-pathogenic or pathogenic and may times behave as opportunistic pathogens
resident flora
transient flora
What are the two types of flora?
Resident flora
organisms that are relatively of fixed types and are regularly found in a given area of the body at given age.
Transient flora
inhabit the skin and mucous membrane temporarily for hours, days or weeks and are derived from the environment.
Normal flora are beneficial to human body because?
inhibit the growth of pathogenic organisms by priming the immune system of newborns
protects the body’s organs and systems that are in direct contact with external environment therefore subject to attack of invasive organisms
vitamin K
Normal intestinal flora secrete ______________ that are needed for the activity of some clotting factors.
mucin
Normal flora can prevent pathogenic organisms from attaching and penetrating the skin and other tissues by producing _________ which make it difficult for the pathogenic organisms to attach to the tissues to produce disease
cellulase, galactosidase, and glucosidase
Normal flora in the intestine aid in the digestion of food by producing enzymes such as
steroids
Intestinal flora help in the metabolism of?
cerebrospinal fluid (CSF)
synovial fluid
blood
Body fluids that are sterile
urinary bladder
uterus
fallopian tubes
middle ear
paranasal sinuses
Sterile tissues include
Skin
part of the human body that is constant contact with the environment making it the most exposed to microorganisms
lysozyme in the skin
acidic pH of the skin due to sweat
free fatty acids in sebaceous secretions
constants sloughing off of the skin
certain factors that eliminate non-resident flora from the skin
bacteria and fungi
normal flora of the skin consists mainly of
axilla, perineum, and toe webs
hand, face and trunk
upper arms and legs
Skin may be divided into three regions
axilla, perineum, and toe webs
These skin regions have more microorganisms
predominantly inhabited by gram-negative bacilli
characterized by having
high moisture levels
higher body temp
higher levels of surface lipids
hands, forearms, feet, legs
Dry sites
have diverse flora because of their exposure to the environment
Staphylococcus epidermis and Staphylococcus hominis
Predominant flora in these dry site (hands, forearms, feet, legs) areas include ?
stratum corneum and hair follicles
Most microorganisms in the skin are found in its superficial layers such as?
Staphylococcus epidermis
Staphylococcus aureus
Microcci (Micrococcus luteus)
Diptheroids (Coryneforms)
Gram-negative Bacilli (Enterobacter, Klebsiella, Escherichia coli, Proteus spp.)
Nail flora
Enumerate: Normal flora found on the skin
Staphylococcus epidermis
major skin inhabitant
compromising approximately 90% of resident aerobic flora
Staphylococcus aureus
most commonly found in nose and perineum; in the nose, number varies with age (greater in newborns than in adults)
Microcci (Micrococcus luteus)
Accounts for 20%-80% in the skin
Diptheroids (Coryneforms)
classified into: lipophilic or non lipophilic
lipophilic
common in axilla
non-lipophilic
more common on glabrous or hairless skin such as palm of hands
Anaerobic diphtheroids (Propionibacterium acnes)
rich in sebaceous glands
Gram-negative Bacilli (Enterobacter, Klebsiella, Escherichia coli, Proteus spp.)
seen in most intertriginous areas such as toe webs and axilla
Nail flora
similar to that of the skin
fungi may also be present ( aspergillus, penicillium, cladosporium, mucor)
Streptococcus viridans group
tongue and buccal mucosa are inhabited mostly by
S. mutans
S. milleri
S. salivarius
S. sanguis
Enumerate: Streptococcus viridans group that part of the normal flora on the mouth
viridans streptococci
have been implicated in the pathogenesis of the dental caries.
gingival crevices and tonsillar crypts
primarily inhabited by anaerobic flora in the mouth
Haemophilus influenzae
Streptococcus pneumoniae
Nisseria meningitidis
Mycoplasma
Enumerate: Transient flora in the pharynx
Neisseria meningitidis
Corynebacterium diphtheriae
Bordetella pertussis
Enumerate: upper respiratory tract initial colonization by pathogenic organisms
lower respiratory tract
usually sterile and organisms that reach this region are usually destroyed by the defense mechanisms of the body such as alveolar macrophages
lysozyme
the normal flora in the conjunctivae are very scanty because they are held in check by the flow of tears that contain?
this may interfere with the cell wall synthesis of organisms
Neisseria
Moraxella
Corynebacterium
Staphylococci
Streptococci
Enumerate: Transient flora in the conjunctiva
transient mouth flora
The esophagus contains
bacteria
minimal_____ may be found in the stomach due to the relatively hostile environment in the stomach.
gastric acid
The acidity in the environment of the stomach is further increased after meals because of the release of
Helicobacter pylori
survive in the acidic environment of the stomach
most common cause of duodenal ulcer
produces urease causes alkalinization of gastric acid thereby enabling it to colonize the stomach
streptococci
lactobacilli
bacteroids
Enumerate: Transient flora found in the small intestine
Bacteroides fragilis
Bifidobacterium/Lactobacillus bifidum
Eubacterium
Peptostreptococcus
Clostridium
Enumerate: The colon is inhabited predominantly by anaerobes which includes
Bifidobacterium/Lactobacillus bifidum
predominant in breast-fed infants
Bacteroides fragilis
most common in the human colon
Lactobacillus acidophilus
predominant intestinal flora n bottle-fed infants
Escherichia coli and other Enterobacteriaceae
about 1%-4% of the flora of the colon are facultative aerobes, predominantly include?
synthesis of vitamin B complex and vitamin K
conversion of bile into bile acids
competition with transient flora for nutrients
prevention of colonization of the intestines by transient flora
production of potentially pathogenic end-products of metabolism that are toxic to transient flora.
Intestinal flora play important role in the body, namely?
urinary tract
sterile above the distal 1 cm of the urethra
S. epidermidis
enterococci
diphtheroids
Enumerate: Flora of the anterior urethra
Mycobacterium smegmatis
in both males and females
may be found as normal commensals in their secretions
Gardnerella vaginalis
bacteroides
alpha streptococci
found in penile urethra
female urethra
either sterile or contains staphylococcus epidermidis
age, hormonal levels, vaginal pH of the host
Vaginal flora varies depending on the
Lactobacillus spp
predominant vaginal flora in female infants
Staphylococcus epidermidis
Streptococci
diephtheroids
Escherichia coli
from 1 month of age until puberty microorganisms that may inhabit vagina include
Lactobacillus acidophilus
corynebacteria
peptostreptococci
streptococci
Bacteroides
staphylococci
Enumerate: Predominant flora in vagina at puberty
Lactobacillus
plays a crucial role in preventing gonococcal infection by producing lactic acid that adds to the acidity of the vagina
Young girls
are more prone to the development of gonococcal infection compared to adult women because the normal acidic pH of vagina as well as the normal vaginal flora are not yet developed
glycogen
After menopause, the vaginal pH increases once more due to the lessened production of?
Torulpsis and Candida
fungi such as ___________ and __________may also be found (10%-30%)
overgrowth of these fungi can lead to vaginal infections such as vaginitis