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MICR 121 > Pathogen-Host Interactions > Flashcards

Pathogen-Host Interactions Flashcards

1
Q

Pathogen

A

ALWAYS causes disease

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2
Q

Examples of pathogens (many)

A

Neisseria gonorrhoea

Ebola virus

HIV

Lyme disease

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3
Q

Potential Pathogen

A

does not always lead to disease

needs to be the right time and place

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4
Q

Example of a potential pathogen

A

E. coli

primary cause of UTI

but we all have E. coli in our gut

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5
Q

Non-pathogen

A

generally don’t cause disease except in RARE cases

in immunocompromised

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6
Q

Examples of non-pathogens (2)

A

1) Lactobacillus
-in yoghurt and cheese

2) Carnobacterium
-in tinned fish

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7
Q

Virulence factors

A

factors that help organisms cause disease or avoid immune responses

e.g. toxin production, capsule, biofilm

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8
Q

Normal flora/ Microbiota definition

A

organisms that are typically found at a body site

may cause disease if in OTHER sites

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9
Q

More about normal flora

A

bacteria are everywhere

certain organism live in specific sites in/on the body

protect us

mucous membranes tract all have bacteria that reside in those ecological niches

BUT mucosal sites also act as the potential portals of entry for most bacteria

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10
Q

Mucous membranes/routes of exposure (4 main ones)

A

1) respiratory, oral (mouth, nose)

2) direct inoculation - sharps

3) GI tract

4) genital tract

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11
Q

T or F: The majority of the routes of exposure all have normal flora.

A

TRUE

Important to examine these sites to see what defences exist that maintain the BALANCE of normal flora and help to control the entry of pathogens

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12
Q

What type of flora would you expect BELOW the belt?

A

Gram -

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13
Q

What type of flora would you expect ABOVE the belt?

A

Gram +

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14
Q

In a hospitalized patient, what type of flora would you expect in a patient in the respiratory tract?

A

Gram -

patient lying down

has to do with gravity

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15
Q

Normal Flora of the Skin with examples

A

Gram +
-bacilli - Corynebacteria AKA “diptheroids”
-cocci - Staphylococci

Below the belt: Gram -

Organisms that can cause infection colonies the skin including pathogens like Staphylococcus aureus but usually Saphylococci non-aureus predominate

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16
Q

Respiratory tract examples

A

Staphylococcus

Streptococcus
-Streptococcus pneumoniae
-Viridans Streptococcus

Haemophilus

Anaerobes

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17
Q

Normal flora of the respiratory tract and oral flora

A

oral health plays a big role in the bacterial populations of the oral flora

anaerobes:
-oxygen is toxic
-produce gases and bad breath
-live in the crevices between teeth
-why babies don’t get bad breath

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18
Q

Flora in the GI tract depend on ________

A

the site

upper vs lower GI tract

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19
Q

Normal Flora of the GI Tract

A

digest food so we can absorb nutrients

UPPER GI
Facultative aerobes
-grows anaerobically AND aerobically

LOWER GI
-anaerobes

few gram POSITIVE bacteria in the GI tract (although Enterococci are present as they are resistant to bile)

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20
Q

GI Tract examples (many)

A

Anaerobes

Enterococcus

Enterobacteriaceae
-E. coli
-Klebsiella

Streptococcus
-Streptococci anginosus

Lactobacillus

Candida

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21
Q

Normal flora of the Genitourinary tract

A

urine washes organism from the urethra to maintain a sterile bladder

bladder doesn’t have a ton of bacteria, if it does –> UTI

vaginal flora changes with age

prepubescent and postmenopausal women
-Flora similar to skin flora

Women of child bearing age
-many bacterial species with a predominance of lactobacillus

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22
Q

Genitourinary tract examples (2)

A

1) Lactobacillus

2) Streptococcus
-Streptococcus agalactiae

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23
Q

pH of the female genital tract in prepubescent women

A

pH of 7

same as skin

menopause - not longer have Lactobacillus

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24
Q

pH of the female genital tract in pubescent women

A

pH of 4 (hella acidic!)

gets colonized by Lactobacillus, produces lactic acid

prevents bacteria from being able to colonize and infect

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25
Visible under a microscope, this is an indicator of abnormal flora in the genitourinary tract...
clue cells cells coated with bacteria
26
What happens if the pH in the female genital tract goes up?
UTIs HIV syphilis yeast infections bacterial vaginosis
27
Normal flora offer _____________ from potential pathogens
protection
28
Disrupting the normal flora - example C. difficile
leading cause of antibiotic associated diarrhea EUBIOSIS -normal flora in GI tract -prevent colonization by pathogens -prevent onset of disease antibiotics wipe out the normal flora and allow the C. difficile spores to colonize the gut DYSBIOSIS -produces toxins that can lead to significant disease in the colon (ulcerative colitis) and can even lead to death
29
Eubiosis
normal microbiome state of balance in the gut microbiota, where beneficial microbes outnumber harmful ones
30
Dysbiosis
disruption of the normal microbiome
31
Risk factors for C. difficile (3)
1) antibiotic use 2) being in the hospital 3) age
32
Bad clinical manifestations of C. difficile infection (2)
1) ulcerative colitis 2) death
33
Non-specific host defences
non-immune normal flora mediated by non-specific immune cells damage results in damage signals these damage signals recruit cells initiation of an immune response
34
Non-specific host defense barriers (3)
1) structural 2) enzymatic 3) pH of the environment
35
Examples of non-specific host defences (many)
Tears -protein break down bacteria Sneezing Mucociliary elevator -ciliated cells move material towards larynx and swallowed Coughing reflex -works in conjunction with mucocilary elevator Fever Stomach pH (1.5) Peeing -washes organisms from the urethra to maintain a sterile bladder Skin Acidity of vagina Lysozyme -breaks peptidoglycan -Lactoferrin: binds free iron and limits bacteria from obtaining iron Secretory Ig -antibody in secretions Inflammation and cellular recruitment to the site of damage -neutrophils and ROS (toxic to cells)
36
What is the best non-specific host defense?
acidity of stomach pH of 1.5
37
What is the highest burden of infection from?
eating
38
Where are the most immune cells located in the body?
GI
39
Properties of skin that make it a good non-specific host defence
1) waterproof 2) good against UV light 3) heat tolerant 4) cold tolerant 5) impact tolerant (scratch skin and nothing happens)
40
Portals of entry (many)
resp eyes ear genitals - urinary tract gut (not as much)
41
Innate (non-specific) immunity defences (2)
1) first-line defences 2) second-line defences
42
First-line defences
EXTERNAL - Barriers at the body surface Skin Mucous membranes Secretions Reflexes Normal microbiota
43
Second line defences
inflammation phagocytes fever complement system interferon
44
Phagocytosis
inflammatory response - cellular recruitment to the site of infection phagocytosis - ingest the bacteria bacteria are ingested into specific vacuoles or “pockets” in the cell that contain digestive enzymes (lysozyme)
45
Innate WBC
neutrophils* -most abundant -destroy bacteria eosinophil basophil monocyte
46
Acquired (specific) immunity
3rd line of defence how vaccines work has long-term memory! T cell lymphocytes [cell-mediated] -kill virally infected cell, foreign cells, tumour cells, cells with internal bacteria or parasites B cell lymphocytes [humoral] -produce antiBodies antibodies
47
Innate vs Acquired
Innate -rapid response -no memory -non-specific Acquired -initial slow response (building a memory, building an army) -subsequent rapid response -long-term memory -specific
48
Why wouldn't you always want an adaptive immune response?
don’t want to keep the response if you don’t need it need to feed, remove wastes, monitor etc. expand, contract, then keep a small portion - memory cells that replicate
49
Humoral/Antibody-Mediated Response
generate an antibody against an antigen immunoglobulins (antibodies = IgG, IgM, IgA, IgE and IgD) respond to an antigen IgM = early, short-lived IgG = late and long lasting IgA = in mucosal, tears, mouth, genital secretions Agglutinate, precipitate, etc promote other factors to help Immunoglobulins.
50
Antibody-mediated response in the COVID vaccine
giving spike protein antibodies against the spike protein debilitate the virus
51
Cell-mediated immunity
Several different types of cells involved including: -Cytotoxic T-cells -Regulatory T cells -NK cells important as a defence in combination with antibody but may also be important alone
52
Cytotoxic T-cells
destroy altered cells by recognizing FOREIGN PROTEIN SEQUENCES presented on the cell surface
53
How are host immune responses overcome?
bacterial and viral evolution
54
Biofilm production
polysaccharide formed when organisms stick to a surface and produce an extracellular matrix area for bacteria to communicate mechanism of immune evasion and prevents the penetration of antibiotics and other cellular factors
55
Where does biofilm production often occur?
prosthetic devices don't have immune surveillance need to do revision antibiotics don't help
56
Capsules
help avoid phagocytosis thick polysaccharide layer that resides outside of the cell prevents it from being internalized by macrophage e.g. Streptococci pneumoniae
57
More direct method to avoid phagocytosis
toxin production
58
Toxin production
small proteins or polysaccharides that are able to arrest cellular functions or lyse host cells e.g. C-difficile e.g. Group A staph
59
Types of toxins (2)
1) Endotoxin 2) Exotoxin
60
Endotoxin
stay within the bacteria structural components of the outer membrane of Gram Negative bacteria Lipid A component of LPS Heat stable - e.g. bulging can
61
Exotoxin
released into the environment Exotoxin - excreted toxins Enterotoxins - exotoxin with effects in the gut
62
How do VIRUSES evade the immune response?
antigenic drift antigenic shift dramatic changes in sequences
63
Antigenic drift
gradual change in antigen e.g. COVID why most vaccines work with the next strain
64
Antigenic shift
major changes e.g. H1N1 to H3N2? vaccines wouldn't work at all

MICR 121 (15 decks)

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