Unit 5 Flashcards
What is a microbiome
Total community of microorganisms in an environment or location on the body
What is normal flora
Microorganisms that are present either in or on an animal that is “healthy” that undergoes constant change
The relationship between normal flora and the host is described as
Symbiosis
What is symbiosis
An association of two or more different species of organisms
In microbiology this refers to:
Bacteria/fungi/yeast and animals/plants
What are ectosymbionts
Organisms that live on the host
What are endosymbionts
Organisms that live in the host
What is mutualism and give an example
Type of symbiosis When both organism benefits from the relationship
Ex. Rumen bacteria
What is commensalism
Type of symbiosis where only one of the organisms benefits from the relationship and the other is neither helped or harmed
The commensal is the organism that is helped
What is competition
Occurs when 2 or more organisms share a space and have to compete for the available resources (space and nutrients)
What are two possible outcomes of competition
One will out compete the other
Both will exists in lower levels
What are the 4 roles of normal flora
Aids in digestion
Provide essential nutrients
Stimulates the immune response
Protects against infection
Why is normal floras role in digestion important in ruminants
To digest insoluble fiber from plants
How does normal flora provide essential nutrients
GI flora synthesize vitamins and essential amino acids
How does normal flora stimulate the immune response
Maintains a low level of ongoing immune activity so they can respond faster to infection
How does normal flora protect against infection by more virulent microbes
Through competition
Altering pH to inhibit growth
Producing anti-microbial factors that prevent colonization
Maintain low level of immune activity
Bind to and block pathogenic bacteria from binding to receptors on cell surfaces
What are bacteriocins
Antimicrobial factors produced by normal flora
What are the 2 ways normal flora in controlled
Competition
Immune system: balance between immune system and normal flora
What are 3 instances of disturbance of the normal flora
When there is too much notmal flora
When there us too little normal flora
When normal flora moved to a new location it is not normally found
What is the most common cause of overgrowth of normal flora
Decreased function if the immune system
What are some other causes of overgrowth of normal flora
When normal flora moves to a new location
What is it called when normal flora cause disease
The normal flora are now called an opprotunistic pathogen
The disease is called an opprotunistic infection
What are the two examples of loss of normal flora
Can be a decrease in overall numbers of bacteria or decreased number of different species
What does a loss of normal flora result in
Lack of competition
Lack of bacteriocins
More space for pathogenic bacteria (allows colonization)
What are some examples of loss of normal flora
Oral antibiotics causes Clostridial enteritis
Loss if skin bacteria leads to yeast overgrowth
True or false
Animals grown in labs without normal flora have a very low risk of infection
FALSE
They have a very high risk
Where are normal flora found in the nose
Only in the nostrils
describe the normal flora in the oro-nasopharynx
Combination of aerobic or anaerobic bacteria, mostly non-pathogenic unless the get onto tissues that are sterile (sinuses, middle ear, brain)
Describe normal flora in the trachea
Transiently colonized by bacteria from the oronasopharynx, continually removed by the mucociliary elevator
What is the role of the mucociliary elevator
The mucus traps microbes and particles
Cilia on the mucosal epithelial cells sweep the mucus upwards to the oral cavity where it is spit out or swallowed
Keeps microbes out of the lower airways
What does damage to the trachea cause and what are some examples of possible damage
Viral infection, smoke inhalation
Increases risk of infection
Describe the normal flora in the lower respiratory tract
Generally sterile (no normal flora)
Transiently colonized by bacteria from the upper resp. Tract but often cannot establish
What are 3 ways microbes are continuously removed from the lower respiratory tract
Mucociliary elevator
Phagocytosis by alveolar macrophages (WBCs in alveoli)
Lysozyme in mucus (hydrolyzes bonds in peptidoglycans of bacteria)
What are some risk factors of microbial colonization in the lower respiratory tract
Acute or chronic aspiration
Damage to the mucus generating cells and cilia of the respiratory tract
What is acute or chronic aspiration from and what are the risk factors
Inhaling infectious materials into the lungs, normally from the oral cavity or esophagus/stomach
Increased risk with megaesophagus, gastroesophageal reflux, chronic vomit, cleft palate
What are some causes of damage to the mucus generating cells and cilia of upper respiratory tract
Traumatic/chemical injury (smoke inhalation)
Primary viral infections (kennel cough shipping fever in cattle)
Inflammation (asthma)
Why is there very few normal flora on the skin
Due to the hostile environment from:
Dryness
Oils (pH of sweat is antibacterial)
Sloughing of skin cells (also sloughs bacteria)
Tends to be transiently colonized
What are found in the moist areas of skin
Fungi (malasrzzia-yeast) in areas such as armpits, groin, and flank folds
What happens to the normal flora with abnormal skin (warm or moist)
Increased bacteria and yeast which can cause pathology
Breach of intact skin allows bacteria to attach to underlying subcutis and proliferate
If yeast populations go into overgrowth it can causes disease (bacterial pyoderma - hot spots)
What is the normal flora of hair, fur and wool
Contaminated by anything in the environment
True or false
Hair, fur and wool is always considered a contaminant
True
True or false
There are the same flora found in the external hair and the hair follicle
FALSE
they are DIFFERENT
Can hair fur and wool support its own biofilm?
Yes, under certain environmental conditions on the fur
Describe the normal Flora on the eye
There are always a small amount of bacteria present on the conjunctiva
Numbers are held in check by lysozyme in the tears
Describe the normal flora on the external ear
Similar bacteria and yeast thats found on the skin, most commonly Staphylococcus
Describe the normal flora of the mouth
Hundred to thousands of different species of microbes
Aerobic: on the teeth
Facultative anaerobes and anaerobes: on the peridontiun (in gums)
What is bacterial plaque on teeth
A mat of microbes (biofilm) solidly attached to teeth
Can extend subgingivally if it extensive and will change from aerobic to anaerobic
What increases risk of bacterial plaque on teeth
Enamel wears/scratches
Malocclusion
Diet high in fermentable carbohydrates
Poor hygiene
Why are there small amounts of normal flora in the monogastric stomach
Because the stomach acid keeps it mostly sterile
What is an iatrogenic cause of change in numbers of normal flora of the stomach
Antibiotics
What does the normal flora of the rumen allow the cow to do
Digest and extract nutrients from cellulose (straw/hay/grass)
Allow animal to digest the microbes for macronutrients
Survive very harsh nutritional/environmental condistions
Describe the normal flora in the rumen
10^12 microbes/ml (alot)
Composed of bacteria, protozoa, fungu, archaea, viruses
Mostly gram negative
E. coli is very common in normal flora
Anaerobic bacteria ferment the sugars to alcohols and acids that can be absorbed
Lactobacilli produce building blocks for milk sugar
What are archaea
“Old” prokaryotic organisms
Make up 3% of microbial mass (separate from bacteria)
Convert hydrogen gas and CO2 to methane (by products of cellulose fermentation) (belched out)
What are the viruses/bacteriophages in rumen flora
Bacteriophage are viruses that infect and kill bacteria
Causes cells to lyse, cell contents are then used as nutrients for the animal
True or false
Colonization of the rumen is fast
FALSE
It is slow
How are microbes of the rumen passed between aniamls
Nursing
Transfering cud
What is the primary factor determining the bacteria profile of the rumen
Diet
Why must diet changes be slow
Proper microbes required to digest the new diet take 2-3 weeks to establish
What can you do to cause rapid colonization
Rumen fluid/microbe transfer
Describe the normal flora in the small intestine
Very few numbers in the duodenum and increase in numbers as it moves distally to the cecum
Made of bacteria, fungi and protozoa
Mixture of anaerobes (more strict anaerobes vs facultative anaerobes)
May have small numbers of pathogenic bacteria (salmonella) which are associated with food poisoning
What are the 6 functions of the small intenstine flora
Vitamin synthesis (vit K, B9 and B12)
Contributes to digestion (mainly fiber)
Enhance segmental contractions and peristalsis
Inhibit colonization by pathogenic bacteria (competition, bacteriocins)
Stimulates immune tissue in SI
Druge metabolism pathways
Describe the normal flora of the large intestine (colon)
Has the largest microbial population in the body (10^11 bacteria/gram of feces)
Mostly anaerobic (strict and facultative) Dominant species is E.coli
Colonization starts at birth with ingestion of birth canal secretions and feces or through nursing, changes with diet and inflammation of GIT
What happens with significant loss of normal flora due to oral antibiotics
Tend to see clostridial overgrowth which leads to diarrhea and/or colitis
What contributes to irritable bowel disorder
Lack of balance between normal flora and the immune system
Describe coliforms
Rod shaped Gram negative Motile Non-spore forming bacteria Can ferment lactose Normally found in feces, water, soil, vegetation (indicates fecal contamination when in environment)
What is small intestinal bacterial overgrowth (SIBO)
When normal flora of the small intestine starts to resemble the colon
Occurs when there is decreased peristalsis or damage to the cecum which allows large intestine flora to migrate to the small intestine
What happens when there is colon flora in the small intestine
Creates gas, which causes distension
Interferes with digestion/absorption
Increased competition for nutrients
Results in inflammation, diarrhea, colic etc
Describe the normal flora of the liver
STERILE
What is biliary cholestasis and what does it cause in the liver
Lack of proper bile acid flow through the biliary ducts
Bacteria that was in the gall bladder could potentially enter the liver
After death, what happens to the liver
There is rapid contamination of the liver from intestinal bacteria
Describe the normal flora of the prepuce
Contaminated, also contains normal bacteria found on the skin and fur
Can harbor chronic asymptomatic pathogens not considered normal flora
What bacteria does the vulva contain
Mix of bacteria found on vagina and skin
What causes changes to the normal flora of the vagina and cervix
Cycling estrogen levels
Describe normal flora of the distal urethra
Normal flora consistent with skin microbes
Colonization with normal flora from intestinal tract can cause disease
Normal flora of proximal urethra and bladder in males
Sterile
Normal flora of the proximal urethra and bladder in females
Supposedly sterile but is transiently colonized by flora from the distal urethra (very low numbers)
Colonization in the proximal urethra and bladder is with microbes from the
Skin, fur, external genitalia and feces
Why is there more colonization of the proximal urethra and bladder in females than males
Because of the shorter distance between the proximal and distal urethra in females
How is colonization in urethra and bladder prevented
Flushing during urination
Distance from the outside
Urine pH inhibits growth (6.2-6.5)
Epithelial cells produce antimicrobial substances that inhibit bacteria from attaching and replicating
What does urease do
Some bacteria produce urease which cleaves urea to increase pH of urine to make it more hospitable for colonization
Describe the normal flora of the kidneys, ureters, prostate and uterus
Always sterile (any microbes present are considered pathogenic)
What does the prostate secrete to protect from colonization
Produce its own prostatic antibacterial factors
How is the uterus protected from colonization
The cervix
Production of acid from lactobacillus in vaginal mucosa (pH)
What do changes in the cervix and vagina during estrus cause
An increased risk of bacteria entering the uterus
What are STDs
When pathogens colonize in the genital tract
Describe the normal flora of mammary glands in dry cows
Certain bacteria in the mammary galnds prevent colonization of teats with pathogenic bacteria
Why are the mammary glands in milking cows at constant risk of infection
Milk is the ideal culture media
Trauma to the teat during milking allows bacteria to enter
What are some internal tissues that are microbe free
Brain, spinal cord Bone, muscles, joints Heart, blood Inside of the eyeball Kidneys, liver, spleen Peritoneum, pleural space
What are some areas of the lower respiratory tract that are microbe fee
Bronchi
Bronchioles
Lung parenchyma
What are some areas of the upper urogenital tract that are microbe free
Proximal urethra and bladder Ureters Kidneys Uterus Prostate
What are Axenic animals (germ free animals) and how are they kept germ free
Animals that are totally free if microorganisms (no normal flora)
Animals is born by c-section under complete aspesis, transferred to sterile environment with sterile food, air, bedding and water
Used for research
Very high risk of infection in the normal environment
What are gnotobiotic animals
Used for research, these are axenic animals that are exposed to only know, specific microbes
Results in animals with only known identities if normal flora and other microbes
Must be kept in sterile environments to prevent introduction of other microorganisms
What are specific pathogen free (SPF) animals
Used for research, animals that do not have a specific microbe/pathogen
When that specific microbe is introduced to the animals, any changes are caused by that microve/pathogen
