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Microbio > Lecture 5 > Flashcards

Lecture 5 Flashcards

1
Q

Microbiome

A

Microbiome– total community of microorganisms in an environment or body location

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2
Q

Normal flora

A

Microorganisms that are present either in or on an animal that is “healthy”
Constant change in numbers and species within the body
Relationship between the normal flora and host is described as SYMBIOSIS
Mutualism
Commensalism

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3
Q

Symbiosis

A

An association of two or more different species of organisms
In Microbiology, refers to:
1) Bacterial/virus/yeast
2) Animal/plant
Relationship can be positive or negative

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4
Q

Ectosymbionts

A
  • live on the host
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5
Q

Endosymbionts

A

live in the host

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6
Q

Mutualism

A

Both organisms benefit from the relationship
Eg. rumen bacteria

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7
Q

Commensalism

A

Type of symbiosis where only one of the organisms benefits from the relationship
The other is neither helped nor harmed
“Commensal” is the organism that is helped

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8
Q

Competition between micro-organisms

A

Occurs when 2 or more microorganisms share a space
Compete for the available resources (nutrients, space

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9
Q

Outcomes of competition between microorganisms

A

1 one will out-compete the other

#2 both will exist at lower levels

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10
Q

Roles of normal flora

A

Aids with digestion of food products
- Especially important in ruminant ability to digest insoluble fiber
Provides essential nutrients
- GI flora synthesize vitamins, essential amino acids
Stimulates the immune response
- Maintains a low-level of ongoing immune activity so can respond faster in an infection
Protect against infection by more virulent microbes

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11
Q

How does normal flora fight against infection

A

Through competition for space, nutrients
Bacteria can alter pH of environment to inhibit growth of other microbes
Bacteria produce their own anti-microbial factors (bacteriocins) that prevent colonization by less desirable bacteria
Maintain low levels of immune stimulation
Bind to and block pathogenic bacteria from binding to receptors on cell surfaces

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12
Q

How do you control normal flora

A

Competition
- Each population exists in lower numbers than if only one population was present
The immune system
- Balance between normal flora and the immune system
- Immune system maintains normal flora at acceptable levels

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13
Q

Diseases are caused when by normal flora

A

There is too little normal flora
There is too much normal flora
Normal flora moves to a new location where it is not normally found

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14
Q

Overgrowth of normal flora

A

Most common cause is decreased function of the immune system
Can’t keep levels of normal flora in check
Can also occur if normal flora moves to a new location
When normal flora causes disease, it is now called an opportunistic pathogen
An infection caused by normal flora is called an opportunistic infection

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15
Q

Loss of normal flora

A

Can be decrease in overall numbers of bacteria or decreased number of species
Results in lack of competition, lack of bacteriocins, pathogenic bacteria have space to attach…
Allows for pathogenic species to colonize or allows increase in numbers of one species normally present in low numbers
Eg. Oral antibiotics can cause Clostridial enteritis
Eg. Loss of skin bacteria leads to yeast overgrowth
Animals grown in labs without normal flora have very high risk of infection/disease

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16
Q

Normal flora in nose

A

Staphylococcus aureus and Staphylococcus epidermidis
Found just inside nostrils

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17
Q

Normal flora in oro-pharnyx

A

Combination of aerobic and anerobic bacteria
Common e.g. - Staphylococcus, Streptococcus, Haemophilus
Mostly non-pathogenic bacteria unless they gain access to tissues are that normally sterile (sinuses, middle ear, brain)

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18
Q

Normal flora in trachea

A

“Transiently colonized” by bacteria from the oronasopharynx
Microbes are continually being removed by the mucociliary elevator
Mucus traps microbes and particles
Cilia located on mucosal epithelial cells sweep the mucus upwards into the oral cavity where it can be spit out or swallowed
One of the main mechanisms that keeps microbes out of the lower airways
Damage (virus infection, smoke inhalation, etc.) will increase risk of infection

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19
Q

Normal flora in lower resp tract and how are microbes removed

A

NO normal flora - generally sterile
May transiently colonize with bacteria from the upper respiratory tract, but these bacteria cannot establish
Microbes are continuously removed by:
Mucociliary elevator
Phagocytosis by alveolar macrophages (WBC in alveoli)
Lysozyme in mucus

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20
Q

Risk factors for microbial colonization of the lower respiratory tract are

A

Acute or chronic aspiration
Inhaling infectious materials into the lungs, usually from the oral cavity or esophagus/stomach
Increased risk with megaesophagus, gastroesophageal reflux, chronic vomit, cleft palate
Damage to the mucus-generating cells and cilia of the upper respiratory tract
Traumatic/chemical injury (e.g., smoke inhalation)
Primary viral infection causes damage to cells (seen in kennel cough, shipping fever in cattle)
Inflammation (asthma)

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21
Q

Normal flora skin

A

Few normal flora due to hostile environment
Dry
Oils, pH of sweat is anti-bacterial
Sloughing of skin cells - adhered bacteria also fall off
Normal flora tends to be transient

22
Q

Common flora on skin

A

Staphylococcus intermedius
Staphylococcus aureus
Fungi (Malasezzia) in moist areas, such as armpits, groin, flank folds
Less often: Corynebacterium, Clostridium perfringens,Streptococcus, Micrococcus

23
Q

Abnormal skin flora

A

If skin becomes warm/moist, there will be increased bacteria and yeast -can cause pathology
Breach of intact skin allows bacteria to adhere to underlying subcutis and proliferate
If bacterial population is disrupted, yeast population may go into “overgrowth” and cause disease

24
Q

Normal hair flora

A

Contaminated by anything in the environment
Always considered a contaminant
Different flora with external hair versus hair follicle
Bacteria, mites (demodex)
Can support its own biofilm under certain environmental conditions

25
Q

Normal eye flora

A

From birth throughout life, there are small numbers of bacteria present on the conjunctiva
Includes Staphylococcus and Streptococcus
Numbers held in check by lysozyme in tears

26
Q

Normal external ear flora

A

Similar bacteria and yeast as found on skin
Most common:Staphylococcus
Also Streptococcus, Pseudomonas, Enterobacteriacae (Gram negative intestinal bacteria), Malasezzia (yeast)

27
Q

Normal mouth flora

A

Contains hundreds to thousands of different species of microbes
Divided into 2 populations:
Aerobic – associated with teeth
Facultative anaerobes, anaerobes – periodontium
Bacterial plaque = mat of microbes (biofilm) solidly attached to teeth
Increased colonization if enamel wear/scratches, malocclusion, diet high in fermentable carbohydrates, poor hygiene
If plaque is extensive, will extend subgingivally where it changes from aerobic to anaerobic populations

28
Q

Normal monogastric stomach flora

A

Limited number of normal flora
Most common are Lactobacillus, Enterococcus, Helicobacter felis

29
Q

Rumen flora

A

Distinct and complex normal flora
Allows animal to digest and extract nutrients from cellulose (e.g. hay, grass)
Microbes themselves are also digested by the animal to provide macronutrients
Ability to derive nutrition from cellulose and normal flora enable ruminants to survive under very harsh nutritional/environmental conditions (deserts, arctic tundra, rocky mountains)
10^12 microbes/ml rumen fluid
Composed of bacteria, protozoa, fungi, archaea and viruses
Gram negative bacteria predominate
Most common bacteria are E. coli, Lactobacilli, Streptococcus bovis, Bacteroides
Fibrolytic microbes break down cellulose
Mostly strict (some facultative) anaerobes
Anaerobic bacteria ferment sugars to alcohols and acids that are absorbed through the rumen wall
Lactobacilli produce building blocks for milk sugar production

30
Q

Archaea

A

Archaea are evolutionarily “old” prokaryotic organisms
Make-up ~3% of microbial mass
Convert hydrogen gas and CO2 (by-products of cellulose fermentation) to methane:
H2+ CO2 → CH4
Methane is belched out during rumination

31
Q

Viruses in rumen flora

A

Bacteriophage are viruses that infect and kill bacteria
Causes cells to lyse
Contents are then used as nutrients by the animal

32
Q

Normal flora in small intestine

A

Bacteria, fungi, protozoa
Very few microbes in the duodenum
Microbe numbers increase moving distally towards cecum
Mixed anaerobes
Strict anaerobes > facultative anaerobes
Enterococcus, E. coli, Enterobacteriacae, Clostridium, Lactobacillus
Some pathogenic bacteria may be present in very small numbers in healthy animals (
Salmonella, Campylobacter– both associated with food poisoning)

33
Q

Function of small intestine flora

A

Vitamin synthesis
Vitamin K production
Vitamin B9 (folate), B12 (cobalamin)
Contribute to digestion, especially fiber
Enhance segmental contractions, peristalsis
Inhibit colonization by pathogenic bacteria
Competition
Production of bacteriocins
Stimulate immune tissues in the small intestine
Take part in drug metabolism pathways

34
Q

Normla flora in large intestine

A

Largest microbial population in body
10^11 bacteria / gram feces
Mostly anerobic bacteria (strict and facultative)
Dominant species is E. coli in cats, dogs, bovids
Also fecal Streptococcus ,Enterococcus ,Klebsiella, Bacteroides, Clostridium, Lactobacillus, Bifidobacterium, Enterobacteriaceae
Also Candida (yeast), enterovirus, adenovirus
Strains of E. coli that are pathogenic to humans found in 30% of dog feces sampled in one study
Also present in cattle feces
Colonization starts at birth with ingestion of birth canal secretions and feces
Also acquired through nursing
Profile of flora changes with diet
Will also change with GI inflammation
Rapidly affected by oral antibiotics
Oral antibiotics will ALWAYS affect the normal GI flora
If enough of the normal flora is eliminated, tend to see Clostridial overgrowth, which can lead to diarrhea and/or colitis
Lack of balance between normal flora and the immune system can contribute to Irritable Bowel Disorder

35
Q

Coliforms

A

Rod-shaped
Gram negative
Motile
Non-spore-forming bacteria
Can ferment lactose
Normally found in feces
Also can be found in water, soil, on vegetation when found in the environment, it is an indicator that there was fecal contamination

36
Q

Fecal coliforms include

A

Escherichia, Enterobacter, Klebsiella

37
Q

SIBO stands for and is caused by

A

Small Intestinal Bacteria Overgrowth
When the normal flora of the small intestine starts to resemble the colon
Occurs when there is decreased peristalsis and/or damage to the cecum –> allows normal large intestinal flora to migrate into small intestine

38
Q

Colon bacteria affects of coliforms

A

Create gas → cause gas distension
Interfere with digestion/absorption
Compete for nutrients

39
Q

Contamination by coliforms results in

A

Inflammation, diarrhea, colic

40
Q

Normal flora of liver

A

The liver is sterile (no normal flora)
If there is biliary cholestasis (lack of proper bile acid flow through the bilary ducts), bacteria that was in the gallbladder could potentially enter the liver
After death there is rapid contamination of the liver from intestinal bacteria

41
Q

Normal flora of perpuce

A

Contaminated
Normal flora: Staphylococcus aureus, Mycoplasma spp.; also bacteria normally found on skin and fur
Can habor chronic asymptomatic pathogens that are NOT considered normal flora

42
Q

Normal flora of vulva

A

Mix of bacteria found on skin and vagina

43
Q

Normal flora in vagina and cervix

A

Flora changes with cycling estrogen levels
Lactobacillus, Streptococcus canis, Staphylococcus aureus

44
Q

Normal flora in urethra

A

Distal urethra
-Normal flora consistent with skin microbes
-Colonization with normal flora from the intestinal tract tends to cause disease
Proximal urethra and bladder in males
-sterile
Proximal urethra and bladder in females
-Supposedly sterile, in reality is transiently colonized by flora from the distal urethra
-numbers are very, very low

45
Q

Colonization of the urethra and bladder are caused by and prevented by

A

Colonization in the proximal urethra and bladder is with microbes from the skin, fur, external genitalia and feces
Colonization is usually prevented by:
Flushing during urination
Distance from the outside
Urine pH inhibits growth of microbes
Normal urine pH is 6.2-6.5
Some bacteria can produce urease, which cleaves urea to increase the pH of the urine so it is more hospitable to colonization
Epithelial cells produce antimicrobial substances that inhibit bacteria from attaching and replicating

46
Q

Flora in ureters, prostate, uterus, and kidneys

A

Always sterile - any microbes present are always considered pathogenic
Prostate secretes its own prostatic anti-bacterial factor
Uterus is protected by the cervix
Production of acid by Lactobacillus in the vaginal mucosa also prevents colonization by other bacteria
Changes to the cervix and vagina during estrus increase risk that bacteria can enter uterus
Many persistent pathogens can potentially colonize the genital tract (i.e., STDs)
May be present in otherwise healthy animals but are never considered normal flora

47
Q

Normal flora in dry cow mammary glands

A

Bacillus spp. and Staphylococcus hominis most important
Prevent colonization of teats with pathogenic bacteria

48
Q

Normal flora in milking cows mammary glands

A

Mammary glands at constant risk of infection,
Milk is an ideal culture medium
Trauma to the teat ends during milking allow bacteria to enter readily

49
Q

Microbe free tissues

A

Internal tissues
Brain, spinal cord
Bone, muscle, joints
Heart, blood
Inside of the eyeball
Kidneys, liver, spleen
Peritoneum, pleural space
Lower respiratory tract
Bronchi, bronchioles, lung parenchyma
Upper urogenital tract
(Proximal urethra and bladder), ureters, kidneys, uterus, prostate

50
Q

Axenic animals are and used for

A

AKA germ-free animals
Used to describe an animal that is totally free of microorganisms
NO infection
NO normal flora
Animal is born by cesarean under complete asepsis → transferred to sterile environment (sterile air, food, bedding, water)
Used for research
Very high risk of infection if exposed to the normal environment

51
Q

Gnotobiotic animals are and used for

A

Used for research
These are axenic animals, to which known, specific microbes are introduced
Result is an animal with known identities of all normal flora and other microbes
Must be maintained in otherwise sterile environments to prevent introduction of unknown microbes

52
Q

SPF is and used for

A

Specific Pathogen Free
Used for research
Animals that definitely do not have a specific microbe/pathogen
If that microbe/pathogen is introduced to the animal, any change that occurs is specifically attributed to the introduction of the new microbe/pathogen

Microbio (11 decks)

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