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Microbiology > Chapter 16 Host - Microbe Interactions > Flashcards

Chapter 16 Host - Microbe Interactions Flashcards

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Biology 101 flashcards
1
Q

Pathology

A

Study of disease

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2
Q

Etiology

A

Cause of the disease

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3
Q

Pathogenesis

A

How the disease develops

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4
Q

Pathogen

A

Organism that can cause disease

1) Pathogenicity- ability to cause disease
2) Virulence - ability to cause harm (severity of disease)

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5
Q

Infection

A

Growth of pathogens in the body

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6
Q

Disease

A

An abnormal state where the body is not capable of performing normal functions

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7
Q

Human Microbiota (the human microbiome)

A

A typical human body has approx.. 1x10(13) human cells and harbors approx.. 1x10(14) bacteria

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8
Q

Normal Microbiota

A

Permanent residents

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9
Q

Transient Microbiota

A

Not permanent residents, but may be present for days, weeks or months

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10
Q

Microbiota General Information

A
  • Is localized to certain parts of the body
  • Generally exposed areas (Ex. Skin, respiratory, intestinal and urinary tracts
  • Internal tissues (blood, muscle, brain, etc.) are normally free of microbes
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11
Q

Microbiota benefit the host by:

A

Benefit the host by preventing growth of pathogens

  • Microbial Antagonism - members of the microbiota produce substances harmful to invading microbes
  • Competitive exclusion - microbiota use up available nutrients preventing growth of pathogens
  • Ex. Clostridium difficile - is inhibited by the normal microbiota of the large intestine
    1) If normal microbiota is eliminated (antibiotic treatments) C. difficile can cause infection
    2) Can lead to fatal inflammation of the colon
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12
Q

Other benefits of the microbiota

A
  • Some bacteria produce enzymes that aid digestion

- E. coli in the large intestine makes vitamin K and B

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13
Q

Opportunistic Pathogens

A
  • Microbes that are part of the normal microbiota
  • Do not usually cause disease
  • Can cause disease if:
    1) Transferred to another part of the body
    2) Human host becomes immune - compromised
    3) Normal microbiota is disturbed
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14
Q

Examples of Opportunistic Pathogens

A

1) E. coli - normal resident of the large intestine
- but if transferred to urinary tract can cause infection
2) Streptococcus pneumonias is a normal resident of the respiratory tract
- When host is already weakened (After having a cold)
- Can cause pneumonia

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15
Q

Symptoms (Classification of disease)

A

What patient feels
Ex. Pain. malaise
Subjective and variable

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16
Q

Signs (Classification of disease)

A

An objective change a physician can measure

Ex. Lesion, swelling, fever, paralysis

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17
Q

Syndrome (Classification of disease)

A

A specific group of symptoms and signs that always accompany a particular disease

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18
Q

Communicable Disease (Classification of disease)

A

Disease that spreads from one host to another

Example: Chicken pox and Measles

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19
Q

Non-Communicable disease (Classification of disease)

A

Does not spread between people

Example: Slmonellosis

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20
Q

Incubation Period (Progression of infectious Disease)

A

Time between infection and first signs or symptoms

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21
Q

Prodromal Period (Progression of infectious Disease)

A

Early, Mild symptoms – Malaise

22
Q

Period of Illness (Progression of infectious Disease)

A
  • Most severe signs and symptoms
  • Active immune response - may cause some signs and symptoms (like fever)
  • If disease is not overcome - results in death
23
Q

Period of decline (Progression of infectious Disease)

A
  • Signs and symptoms subside
  • Can last hour or days
  • Patient vulnerable to secondary infections
24
Q

Period of Convalescence (Progression of infectious Disease)

A
  • Recovery occurs

- Pathogens can still be present and spread to others – can carry pathogens for months or years

25
Q

Acute (Duration of Symptoms)

A

Rapidly developing, short duration (Influenza)

26
Q

Chronic (Duration of Symptoms)

A

Slow to develop, continual duration (Tuberculosis)

27
Q

Latent (Duration of Symptoms)

A

Inactive for a period of time, can be reactivated ( Cold sores which is the herpes virus)

28
Q

Number of Microbes is Important

A
  • If too few microbes enter, immune system it will fight them off and prevent disease
  • Likelihood of disease increases as microbe numbers increases
  • Virulence and pathogenicity of a microbe can be expresses numerically:
    1) Infectious dose
    2) Potency of a Toxin
29
Q

Infectious Dose

A
  • ID(50) - cause infection in 50% of the population
  • Ex. Bacillus anthracis
    1) By ingestion - ID(50) = 250,000 to 1,000,000 endospores
    2) By inhalation - ID(50) = 10,000 to 20,000 endospores
    3) Through a cut in the skin- ID(50) = 10-20 endospores
30
Q

Potency of a Toxin

A

Expresses as lethal dose

LD(50) = kills 50% of the infected population

31
Q

Localized Infection

A

Confined to small area of the body

32
Q

Systemic infection

A

Microbes or toxins are spread throughout the body

33
Q

Septicemia

A

Systemic infection of the blood

1) Bacteremia - Bacteria in the blood
2) Toxemia - Viruses in the blood

34
Q

Sepsis

A

Life threatening systemic inflammatory response, usually due to bacteremia
Example: Clostridium retain causes infection of a cut.
Releases toxins into the blood

35
Q

Koch’s Postulates

A
  • Based on the germ theory of disease
  • Allows determination of specific microorganisms that cause disease
    1) The same pathogen should be present in every case of the disease
    2) The pathogen must be isolated and grown in pure culture
    3) Pathogen from the pure culture should cause disease when inoculated into a healthy lab animal
    4) The same microbe should be isolated again from the inoculated individual
36
Q

Exceptions to Koch’s Postulates

A

1) Some bacteria will not grow in pure culture
- Ex. Treponema pallidum - cause agent of syphilis
2) Some pathogens cannot be used to infect lab animals
-Ex. HIV
3) Sometimes several different microorganisms can cause the same diseases
Ex. Streptococcus progenes- causes Strep throat, skin infections, and scarlet fever

37
Q

Adherence

A

Surface molecules that allow a pathogen to attach - adhesions

  • Often stick to specific receptors on host cell surface
  • Ex. Bacterial capsules, pili and fimbriae
  • Ex. Viral spikes
38
Q

Invasiveness

A
  • Ability of a pathogen to invade and multiply in tissues
  • Two types of molecules promote invasiveness:
    1) Extracellular Enzymes - Exoenzymes
    2) Invasions
39
Q

Extracellular Enzymes - Exoenzymes

A
  • Degrade or alter host cells and tissues
  • Fibrinolysin - degrades fibrin clots
  • Collagenase - degrades connective tissue
  • Coagulase - Promote blood clots and around the bacterial cell
40
Q

Invasions

A
  • Surface proteins that cause rearrangement of host cell cytoskeleton
  • Forces host cell to take in the bacterium
  • Ex. Salmonella enterica forces “ruffling” by intestinal cells
41
Q

Mucous Membranes (Portals of Entry)

A

-Respiratory Tract - most common portal of entry (Microbes inhaled into nose or mouth - ex. Colds, Influenza)
- Gastrointestinal Tract
Germs enter in food or water
Most are destroyed by acid (in stomach) or by bile (in intestine)
Some can survive: ex. Vibrio cholera
- Genitourinary Tract - STI’s
Most pathogens require a broken mucous membrane
Ie. A cut or a microbrasion
- Conjunctiva - membrane covering the eye

42
Q

Skin (Portals of Entry)

A
  • Unbroken skin is impenetrable by most microbes
  • Some microbes can cause infections of hair follicles
  • Most require a wound for entry
43
Q

Parenteral Route

A
  • Microbes deposited directly into tissues when skin or membranes are broken
  • Ex. Tick bite can introduce bacteria into host - Lyme disease
  • Ex. Intravenous injection with contaminated syringe - HIV
44
Q

Damage to the Host

A

Bacteria can do direct or indirect damage:

1) Indirect - inducing an immune response and causing inflammation
2) Direct - Production of exoenzymes or toxins (toxin- poisonous substance produced by a microorganism)

45
Q

Exotoxins (Damage to the Host)

A
  • Proteins excreted by bacteria
  • Generally heat sensitive
  • Can be extremely toxic - among most lethal substances known
  • Ex. Clostridium botulinum - cause botulism (Botulinum toxin - 1 mg can kill 1,000,000 guinea pigs
46
Q

Neurotoxins (Category of Exotoxins)

A

-Interfere with nerve impulses
- Botulinum toxin causes flaccid paralysis
Muscles permanently relax
Heart stops beating, breathing stops
-Tetanus Toxin (Clostridium tetani) - causes rigid paralysis
Uncontrollable muscle contractions (spasms) - results in lockjaw
Death usually occurs due to spasms of respiratory muscles

47
Q

Enterotoxins (Category of Exotoxins)

A
  • Modify intestinal cells so they continuously secrete water

- Example: Cholera toxin causes severe watery diarrhea

48
Q

Cytotoxins (Category of Exotoxins)

A
  • General cell killers
  • Ex. Diphtheria toxin (Corynebacterium diphtheria) - interferes with protein synthesis killing cells - kills cells in the respiratory tract - diphtheria
49
Q

Endotoxin

A
  • Lipopolysaccharide - Part of the outer membrane of Gram negative bacteria
  • Does not cause any problems when embedded in the membrane
    Released when bacteria die
    Can trigger fever, inflammation, hemorrhaging, shock
    -Not as potent as exotoxins - need much more to cause symptoms
50
Q

Example of Endotoxin

A

Ex. Salmonellosis (Salmonella enterica)

  • Food borne illness
  • Symptoms are caused by endotoxin released from millions of dying bacteria
  • Antibiotic treatment may do more harm than good
51
Q

Comparing Exotoxins and Endotoxins

A

Exotoxins: Proteins, released outside the cell, extremely toxic- often lethal

Endotoxins: Lipopolysaccharide, only released when bacteria die, not as toxic - not usually lethal

52
Q

Damage Caused by Viral Infections

A
  • Cytopathic effects (CPE) - visible effects of viral infection
  • Disruption of cell processes –Ex. Herpes viruses - stop host cell division
  • Destruction of intracellular structures (ex. The nucleus)
  • Can form inclusion bodies- consist of viral parts
  • Synctium formation - several cells fuse to form one giant cell (Ex. measles)
  • Host cell lysis
  • Indirect damage caused by the inflammatory response

Microbiology (17 decks)

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