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BIOL334 > Environmental Pathogens Lecture 1 > Flashcards

Environmental Pathogens Lecture 1 Flashcards

1
Q

Define a pathogen

A

A biological agent that causes disease or illness in a host. Can be bacteria, fungi, protozoan or viruses.

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2
Q

What is an environmental pathogen?

A

Microorganisms that normally spend a substantial amount of their lifecycle outside of human hosts, but when introduced to humans cause disease with measurable frequency.

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3
Q

Give some examples of bacteria

A

Staphylococcus aureus- from the skin, an opportunistic pathogen. e.g., MRSA
Campylobacter jejune- found in chicken farms, causes gastroenteritis.
Legionella pneumophilia- causes Legionnaires- found in AC units, taps, showers. Can be free living or an intracellular pathogen (protozoan and alveolar macrophages).
Borrelia burgdorferi- causes Lyme disease- tick borne and temperature effects their population

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4
Q

Normal Resident Flora

A
  • microbes that engage in mutual/commensal associations (indigenous flora and microbiota).
  • Includes bacteria, fungi, protozoa and viruses. Most areas of the body in contact with the environment harbour microbes.
  • Bacterial flora provide a benefit by preventing overgrowth of harmful microbes–microbial antagonism
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5
Q

What is microbial antagonism?

A
  • Resident flora (bacteria) prevent overgrowth of other harmful microbes
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6
Q

How much bacteria colonises the human body?

A
  • 10^14 microbial cells are associated with the human body, 80% of which have been cultured.
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7
Q

What is the Gut microbiota?

A

Gut microbiota are the microorganisms, including bacteria and archaea, that live in the digestive tracts.

  • Breaking of foetal membrane exposes the infant.
  • Post gut is transformed and acquisition is random not predetermined
  • Host provides bacteria with nutrients
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8
Q

Describe the changing gut microbiota with age

A

Birth: delivery and mode of feeding affects composition of the gut. E.coli colonises in first 14 hours
Early childhood- new strains outcompete old ones, rapid increase in diversity. Shifts in response to diet, illness, hormones
Adult microbiota- Highly distinct, changes slower
Elderly- substantially different than your
Few microbes are pathogenic

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9
Q

Factoring influencing intestinal flora

A

Delivery method at birth, antibiotics, diet, stress, contraceptives, bactericidal chemicals in drinking water, heavy metals

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10
Q

Define infection

A

a condition in which pathogenic microbes penetrate host defences, enter tissues and multiply causing disease

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11
Q

Define Disease

A

Any deviation from health, disruption of a tissue or organ.

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12
Q

Define pathogenicity

A

An organisms ability to cause disease

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13
Q

Define virulence

A

A measure of the degree of disease that a pathogen causes

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14
Q

Define ‘true pathogens’ and give examples

A

Capable of causing disease in healthy person with normal immune defences- influenza virus, malaria

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15
Q

Define opportunistic pathogens and give examples

A

Cause disease when hosts defences are compromised or grow in a part of the body not natural to them.
E.g., Pseudomonas and Candida albicans

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16
Q

Name the 5 modes of transmission of pathogens

A

Person to person- direct contact, STIs, respiratory infections (coughing/sneezing)

Waterborne transmission*- drinking water/swimming (ingestion), faecal oral route (contamination of water)

Foodborne transmission*- insufficient cooking, ingestion of raw/unwashed food, poor sanitation or hygiene. 6million cases/year US

Airborne transmission*- Aerosols, wastewater treatment plants, sludge, showers e.g., Legionella

Vector borne transmission*- bite of an animal host- Malaria, African sleeping sickness, Yellow fever

*denotes environmental routes

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17
Q

Portals of entry of microbes

A 
Skin- abrasions
GI tract- food/drink 
Respiratory tract 
Urogenital (sexual) 
Transplacental
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18
Q

Define Infectious Dose (ID)

A
  • Minimum number of microbes required for an infection to proceed.
  • Microbes with smaller ID have greater virulence
  • Varies between species, genus and strain
  • Cholera ID: 10^8 cells, Measles 1 virus,
19
Q

Describe the 3 stages of infection

A
  1. Attaching to the host via adhesion- dependent on binding between specific molecules on the host and pathogen. e.g., fimbrae, flagella, slimes/capsules, pills.
  2. Surviving host defences- initial response from host comes from phagocytes.
    - Antiphagocytic factors are used to avoid this.
    - Species of Staphylococcus and Streptococcus produce leukocidins- toxic to WBCs.
    - Slime layer/capsule makes phagocytosis difficult
    - Ability to survive intracellular phagocytosis Legionella pneumophilia.
  3. Causing disease- Virulence factors e.g., exoenzymes digest epithelial tissues and promote invasion of pathogens, toxigenicity- ability to produce toxins at site of multiplication (endotoxin-LPS, exotoxins secreted by gram +ve and -ve).
    - Antiphagocytic factors
20
Q

Describe the four phases of infectious disease

A
  1. Incubation period- time from initial contact to appearance of symptoms (several hours-several years).
  2. Prodromal stage: mild symptoms, unspecific, feelings of discomfort.
  3. Period of invasion: multiplication high level, specific symptoms
  4. Convascelent period: a person begins to respond to infection, symptoms decline.
21
Q

Define localised infection

A

Microbes enter the body and remain confined to a specific tissue

22
Q

Define systemic infection

A

Infection spreads to several sites and tissue fluids usually in the bloodstream

23
Q

Define focal infection

A

When infectious agents break loose from a local infection and is carried to other tissues

24
Q

Define mixed infection

A

Several microbes grow simultaneously at the infection site-poly microbial

25
Q

Define secondary infection

A

Another infection by a different microbe (after primary/initial infection).

26
Q

Define acute infection

A

Comes on rapidly, with severe but short lived effects

27
Q

Define chronic infection

A

progress and persist over a long period of time

28
Q

Portals of exist (spread/transmission)

A
  • Respiratory- mucus, nasal drainage, saliva
  • Skin scales
  • Faecal exit
  • Urogenital tract
  • Removal of blood
29
Q

Define Latency

A

after the initial symptoms in certain chronic diseases, the microbe can periodically become active and produce a recurrent disease; person may or may not shed it during the latent stage

30
Q

Chronic carrier

A

Person with a latent infection who sheds the infectious agent

31
Q

Define reservoir

A

Primary habitat of pathogen in the natural world, human or animal carrier, soil, water, plants

32
Q

What is the ‘source’ in the context of infection

A

individual or object from which an infection is actually acquired

33
Q

Define vector

A

A live animal (other than a human) that transmits an infectious agent from one host to another

34
Q

Biological vector

A

actively participate in pathogens life cycle

35
Q

Mechanical vector

A

not necessary to the life cycle of an infectious agent and merely transports it without being infected

36
Q

Define zoonosis

A

An infectious indigenous to animals but naturally transmissible to humans

  • An infectious disease that is transmitted between species (sometimes by a vector) from animals other than humans to humans
  • 150 zoonoses worldwide, make up 70% of new emerging diseases
  • Impossible to eradicate without eradicating the animal reservoir
37
Q

Define prevalence

A

Total number of existing cases with respect to the entire population represented by a percentage of the population (n:100,000)

38
Q

Define incidence

A

Measures the number of new cases over a certain time period, as compared with the general healthy population
(n:100,000/time)

39
Q

Define mortality rate

A

The total number of deaths in a population due to a certain disease

40
Q

Define morbidity ratee

A

number of people affected with a certain disease

41
Q

Principal agencies responsible for keeping track of infectious diseases

A

World health organisation (global)

USA (Centers for disease control and prevention (CDC))

Europe (European centre for disease and prevention control)

UK (Public Health England)

41
Q

Principal agencies responsible for keeping track of infectious diseases

A

World health organisation (global)

USA (Centers for disease control and prevention (CDC))

Europe (European centre for disease and prevention control)

UK (Public Health England)

42
Q

Endemic scale

A

disease that exhibits a relatively steady frequency over a long period of time in particular geographic locale

43
Q

Sporadic disease

A

When occasional cases are reported at irregular intervals

BIOL334 (9 decks)

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