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Introduction to Medical Microbiology > Lecture 2: Host-Parasite Relationship > Flashcards

Lecture 2: Host-Parasite Relationship Flashcards

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1
Q

Define Symbiosis?

A

Organise that need each other to survive

Close association of two dissimilar organisms

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2
Q

Mutualism?

A

All participants benefit

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3
Q

Commensalism?

A

One benefits and the other is not harmed

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4
Q

Parasitism?

A

Parasite benefits and other is harmed

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5
Q

Predation?

A

Parasite actively hunts host

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6
Q

Competition?

A

Organisms fight against each other

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7
Q

What type of environment is human body for microbes?

A

Is a diverse environment in which specific niches are present and dynamic relationships exist.

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8
Q

What organisms make up the normal microbiota of human body?

A

Mainly bacteria (+1000 species). Few eukaryotic fungi (algae) and protists (protozoa). Some ArchaeBacteria at lower G.I tract.

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9
Q

Micro-biome?

A

All genes of host & microbiota

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10
Q

Total Microbial load of human body?

A

Greater than 100 trillion microbial cells

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11
Q

Reasons to study human microbiota?

A

Gain insight into possible infection resulting from injury.

Understand consequences of overgrowth of microbes usually absent.

Increase awareness of role-played by indigenous microbes in stimulating immune responses.

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12
Q

Factors influencing the composition of normal flora?

A 
Anatomical site.
Age.
Sex.
Diet & Nutrition.
Environmental.
Developmental changes.
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13
Q

What is Nosocomial?

A

Something picked up from hospital or health facility.

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14
Q

What is a opportunistic pathogen?

A

normal microbiota that produce disease under certain conditions

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15
Q

What does normal flora have to gain from host?

A
  • Supply of Nutrients
  • Stable environment
  • Constant Temperature
  • Protection
  • Transport
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16
Q

What does the host obtain from normal flora in mutualism?

A
  • Nutritional benefits
  • Stimulation of the immune system
  • Exclusion of potential pathogens
  • Antagonism of pathogens
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17
Q

Benefits of having normal flora in human body?

A
  • Provide essential nutrients
  • Prevent colonisation by pathogens
  • Antagonise other bacteria
  • Stimulate development of immune system
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18
Q

What is tissue tropism?

A

This is specific organisms at specific sites.

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19
Q

Describe the environment of skin?

A

It is generally considered to be an inhospitable environment with slight acidic pH. It has high concentration of NaCl and is generally low moisture environment. Bacteria numbers are usually low.

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20
Q

What areas of skin will have the highest number of microbes?

A

Areas high in moisture most protected from the outside environment.

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21
Q

What is a microbiota called that is not usual found at the site of interest?

A

Transient Microbes.

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22
Q

Microbiota that are usually found at site of interest?

A

Residential Microbes.

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23
Q

What types of microflora are found at entrance of orifice?

A

Mixed flora

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24
Q

What is the main type of microbiota found on the skin?

A

Consists largely of Micrococci and corynebacteria.

  • Staphylococcus Epidermis (90%)
  • Micrococcus luteus
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25
Q

What type of microflora live below skin follicles, sweat and sebaceous glands?

A

Anaerobes (eg. Propionibacterium acnes)

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26
Q

What microflora are usually found at the face, hands and nasal cavities? What percentage of people usually have them?

A

Staphylococcus aureus which is an opportunistic bacteria. Found in 20-40% of population

27
Q

Define Conjunctiva? Is there many organisms usually present?

A

Thin membrane covering eyes and inside of eyelids. Low number of organisms present.

28
Q

What are the main microbiota found at the conjunctiva?

A

Staphylococcus epidermis, S. aureus.

29
Q

How is the microbiota kept with in healthy levels in the Conjunctiva?

A
  • Blinking (mechanical cleaning)

- Lachrymal secretions containing lysozyme.

30
Q

Define the term ‘commensalism’.

A

This is a form of symbiosis by which one organism benefits where the other is harmed.

31
Q

List a member of the normal human microbial flora (full genus and species) that is a major cause of human infection and list where it is normally found?

A

Streptococcus pneumonia is a pathogen found in the upper respiratory tract and can cause infection if population are too high

32
Q

A patient with a suspected urinary tract infection is asked to provide a mid- stream urine specimen. Why?

A

This is because mid stream part of urine is most likely to reflect the microbiome that the patient has as it is the microbes that are residential in the urine tract as the temporary one will be flushed out in first part of urine.

33
Q

What is a nosocomial infection?

A

A nosocomial infection is something picked up from a hospital or health facility. These are usually dangerous

34
Q

The lower respiratory tract is normally sterile. Why?

A

This is because the lower respiratory tract has mechanism in place to prevent microbiome from living growing there. These include cleansing action of ciliated epithelium & mucocilliary blanket. Sneezing, coughing and swallowing. Phagocytic actions of alveolar macrophages and lysosome in mucus.

35
Q

What is lysozyme and its role in tears?

A

This is enzyme that act as a chemical barrier released in lachrymal that prevents against pathogens and microbes by breaking down bacterial cell walls.

36
Q

Which bacteria (full genus and species) is the most common cause of urinary tract infections?

A

Candida Albicans

37
Q

List one pathogen (full genus & species) that may be found as a member of the normal flora of the upper respiratory tract?

A

Neisseria meningitidis

38
Q

Main microbiota found in Nasal cavity and Nasopharynx?

A

Staphylococcus epidermis & corynebacteria. (Staphylococcus aureus)

39
Q

Bacteria in sinus?

A

Healthy sinus are sterile.

40
Q

Is there a large number of bacteria species in the upper respiratory tract?

A

Yes a large number :)(:

41
Q

What is an example of microbiota found in respiratory tract?

A
  • Alpha heamolytic streptococci

- Neissera meningitidis

42
Q

Pathogens found in the upper respiratory tract?

A
  • Streptococcus pneumonia
  • Streptococcus pyagenes
  • Haemophilus influenza
43
Q

What type of enviroment is expected to be found in the lower respiratory tract?

A

The lower respiratory tract is virtually pathogen free with a low number of microbiota.

44
Q

How is the lower respiratory tract kept virtually pathogen free?

A

These include

  • cleansing action of ciliated epithelium & mucocilliary blanket.
  • Sneezing, coughing and swallowing.
  • Phagocytic actions of alveolar macrophages
  • lysosome in mucus.
45
Q

What type of pathogens could the lower respiratory tract be susceptible?

A

These can be susceptible to pathogens of upper respiratory tract.

46
Q

What variety of bacteria occupy the oral cavity?

A

A large number of bacteria occupy the oral cavity. streptococci, lactobacilli and a great number of anaerobes(candida)

47
Q

What colonises the oral cavity at birth?

A

Streptococcus salivarius

48
Q

What bacteria is responsible for initiating dental decay?

A

S. mutans

49
Q

Explain the activities leading to dental decay?

A
  • Produces hydrolytic enzymes that breakdown sucrose → lactic acid (↓pH). More acidic enviroment renders teeth more vunerable to decay
  • Organism secretes insoluble glucans/polysaccharides = biofilm of glycoprotein and bacteria – in the oral cavity → plaque build up
50
Q

What type of environment is the urogenital tract?

A

Urogenital tract is usually sterile.

51
Q

Normal flora occupy that anterior (distal) urethra?

A
  • Staphylococcus epidermidis

* Enterococcus faecalis

52
Q

What microbiota colonise female genital tract soon after birth?

A
  • staphylococci
  • streptococci
  • E. coli
53
Q

In the Female genital tract what microbiota dominate between Puberty to menopause?

A

Lactobacillus acidophilus

54
Q

Candida albicans are normally present in low numbers in the Female genital tract and responed to changes in?

A
  • pH changes
  • hormonal changes
  • normal flora changes
55
Q

What bacteria are present in the Gastrointestinal Tract in breast fed infants?

A

bifidobacteria (90%)

56
Q

What other factors does human milk contain?

A

Human milk contains a growth factor that enriches for growth of bifidobacteria and
prevents colonisation of intestinal tract by non-indigenous or pathogenic species

57
Q

When breast fed infants are swapped to solids or cows milk what microbiota join the bifidobacteria?

A

bifidobacteria are progressively joined by:

  • enterics
  • Bacteroides
  • enterococci
  • lactobacilli
  • clostridia
58
Q

What kind of bacteria is found in the Oesophagus?

A

only the bacteria swallowed with saliva and food

59
Q

Name bacteria found in stomach and what it can lead to?

A

Helicobacter pylori, causes gastric ulcers, gastric and duodenal cancers

60
Q

Flora in the proximal small intestine?

A

relatively sparse Gram-positive flora
 lactobacilli
 enterococci

61
Q

Flora of the distal small intestine?

A 
Distal small intestine contains greater variety and numbers of bacteria compared to proximal.
 lactobacilli,
 enterococci,
 Coliforms
-Protozoa
62
Q

Amount of large intestine flora?

A

10^12/g faeces wet weight

63
Q

Prodominate organisms in the large intestine?

A

Predominant organisms are:
 Bacteroides
 anaerobic lactic acid bacteria
 Bifidobacterium

64
Q

Infection by Normal Flora is facilitated by?

A
  • Damage to the epithelium and mucosal surfaces
  • Presence of a foreign body
  • Transfer of normal flora to another anatomical site
  • Suppression/impaired immune system
  • Secondary bacterial infections
  • Use of antimicrobial chemotherapy
  • Nosocomial infections

Introduction to Medical Microbiology (7 decks)

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