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EMS > Lecture 22: Micro-organisms in Health: Normal microbiota > Flashcards

Lecture 22: Micro-organisms in Health: Normal microbiota Flashcards

1
Q

How many human cells does the average 70kg human have?

A

30 trillion human cells

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2
Q

How many bacterial cells does the average 70kg human have?

A

39 trillion bacterial cells

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3
Q

what varies at different sites of the body?

A

Organism density

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4
Q

What areas harbour fewer organisms?

A

Dry, exposed areas of skin

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5
Q

What area harbours more organisms on the body?

A

‘moist’ or protected areas of skin such as armpits, the groin area or between the toes.

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6
Q

Where is organism density greatest in the body?

A

oral cavities and colon

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7
Q

What is normal flora/ normal microbiota?

A

Organisms found in a given location in a state of health

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8
Q

What is colonisation?

A

Establishment at a site in the body

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9
Q

What is microbiota?

A

All the organisms in a given community

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10
Q

What is microbiome?

A

All the genes present within the microbiota

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11
Q

What is symbiosis?

A

Two or more organisms co-exist in close physical association.

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12
Q

What is the relationship between the human ‘host’ and normal flora described as?

A

Symbiotic

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13
Q

What is infection?

A

Infection is the presence of microorganisms causing damage to body tissues, usually in the presence of acute inflammation (pain, swelling, redness, heat and loss of function)

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14
Q

What is mutualism?

A

Both organisms benefit from symbiosis

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15
Q

What is neutralism?

A

Neither organism derives benefit or harm

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16
Q

What is commensalism?

A

One organism benefits, the other derives neither benefit nor harm

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17
Q

What is parasitism?

A

One organism (parasite) benefits at the expense of the other (host)

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18
Q

What is Dysbiosis?

A

Shift in microbiota which is representative of a disease state
Pathobiont (cause harm under certain circumstances)

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19
Q

Give an example of mutualism?

A

Nitrogen fixing bacteria and legumes

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20
Q

What type of flora are found in non-sterile sites?

A

Have normal flora

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21
Q

What type of flora are found in sterile sites?

A

No normal flora

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22
Q

What are characteristics of non- sterile sites?

A

Exposed to the environment
- Directly
- Indirectly
No mechanism in place to maintain sterility

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23
Q

During pregnancy, till when is sterility maintained?

A

Until birth

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24
Q

When does the acquisition of normal flora begin?

A

At birth

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25
Q

What produces differences in normal flora at the beginning of life?

A

Caesarean vs birth canal
Breast vs bottle feeding

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26
Q

What type of flora is acquired from birth?

A

Predominantly bifidobacteria and lactobacillus. Bottle-fed more Enterobacteriacea.

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27
Q

Name some non-sterile sites?

A

Skin
Vagina
Conjunctiva
Nasopharynx
Vagina
GI tract

28
Q

How are sterile sites maintained?

A
  1. Sterility maintained by surface cleaning
    - Open to the environment e.g. lower respiratory tract
  2. Sterility maintained by barriers (allow uni-directional flow)
    - Adjacent to non-sterile sites e.g. upper genital tract protected by the cervix
  3. Sterility maintained by physical separation from non-sterile sites
    - Closed cavities e.g. pleural cavity, peritoneal cavity, spinal cord and meninges
29
Q

How do you collect Blood cultures/CSF/ Pleural fluid?

A

obtained by passing a needle through the skin into the relevant ‘sterile’ site. Potential for contamination with skin organisms

30
Q

How do you collect a sputum sample?

A

obtained by expectoration of lower airways secretions (‘sterile site’) through the upper airway (‘non-sterile site’) – risk of contamination

31
Q

How do you collect a urine sample?

A

obtained by passing urine from the bladder/upper urinary tract (‘sterile site’) via the terminal urethra (‘non-sterile site’). Risk of contamination reduced by collecting Mid Stream Urine (MSU) sample

32
Q

What are microenvironments?

A

Different sites, Within sites

33
Q

What is tissue tropism?

A

Propensity for a particular organism to grow in a particular habitat

34
Q

Factors that influence what organisms colonise what areas?

A

Moisture
Temperature
pH
O2 availability
Nature of surface

35
Q

Characteristics of skin?

A

Variable temperature
Dry
Subject to abrasion
Aerobic environment
Nutrient-poor
Skin surface components

36
Q

Name 3 types of skin flora?

A
  1. Coagulase-negative staphylococci (Staphylococcus epidermis)
  2. Staphylococcus aureus (esp. in nasal carriers)
  3. Cutibacterium acnes (Propionibacterium acnes)
37
Q

what bacteria may be similar to bacteria in an orifice?

A

The bacteria on the skin near any body orifice

38
Q

Characteristics of gingival crevice?

A

Constant temperature
Moist
Few physical challenges (toothbrush)
Anaerobic environment
Bathed in nutrients
Mucosal surface components

39
Q

Where are higher proportions of Actinomyces found: Teeth or soft tissue?

A

Teeth

40
Q

Is the microenvironment of the gingival crevice similar to the microenvironment of the tongue and saliva?

A

No.
The microenvironment of the gingival crevice differs greatly from the bacteria present on the tongue and again form those present within saliva

41
Q

Give 3 examples of mouth flora?

A

Viridans/oral streptococci
Anaerobes
Red complex bacteria

42
Q

Give 5 examples of Red complex bacteria?

A

Porphyromonas gingivalis
Tannerella forsythia
Treponema denticola
Aggregatibacter actinomycetemcomitans,
Prevotella intermedia

43
Q

How does flora of the mouth benefit from the host?

A

By gaining nutrients

44
Q

What does flora of the mouth provide the host with?

A

Essential vitamins that are synthesised by bacterial species.

45
Q

What can established normal flora of the mouth prevent?

A

Colonisation of pathogenic flora.

46
Q

What are the consequences of overgrowth of oral sreptococci?

A
  • Biofilms on teeth
  • Conversion of sugar to lactic acid
    Damages enamel and erodes the tooth
47
Q

What are the 2 sites of Nasopharyngeal flora?

A

Nostrils

Pharynx

48
Q

What are the types of bacteria found in the nostrils?

A

Skin flora
S.aureus

49
Q

What are the types of bacteria found in the Pharynx?

A

Respiratory and other pathogens
- Streptococcus pyogenes (group A)
- Haemophilus influenzae
- Streptococcus pneumoniae
- Neisseria meningitidis 7-34% in UK university
students1
- Staphyloccus aureus

50
Q

What can be a consequence of damage to the respiratory tract epithelium?

A

If respiratory tract epithelium becomes damaged, these species can cause infections in the lower respiratory tract.
E.g. Bronchitis, pneumonia

51
Q

What type of flora is found in pre-puberty vagia?

A

Skin flora
Lower GI flora
Mainly E. coli

52
Q

What type of flora is found in post-puberty vagina?

A

Lactobacillus spp. Lactobacillus acidophilus
Skin flora
A few C. albicans

53
Q

What is produced post puberty due to circulating oestrogens?

A

Glycogen

54
Q

How is low pH beneficial in the vagina?

A

Low pH beneficial in preventing infection by opportunistic pathogens e.g. overgrowth of C. albicans – causing Thrush

55
Q

What does low gastric pH inhibit?

A

Bacterial growth

56
Q

What type of bacteria is found in the GI tract (Stomach and small intestine)?

A

Predominantly aerobic bacteria
- acid-tolerant Lactobacilli
- Helicobacter pylori
Few or no anaerobes

57
Q

How does H. Pylori cause a gastric ulcer?

A

H. pylori can survive the highly acidic nature of the stomach by producing urease to convert urea into ammonia and carbon dioxide.

58
Q

What percent of the population is H. Pylori found in?

A

30 - 50%

59
Q

What percent of people with H. Pylori colonised to develop ulcers?

A

less than 20%

60
Q

How many species have been identified in the large intestine?

A

At least 400

61
Q

What percent of flora in the large intestine are anaerobes?

A

95-99%

62
Q

What other type of flora is found in the large intestine aside from Anaerobes?

A

Aerobic bacteria
(Enteric Gram-negative bacilli)

63
Q

What prevents overgrowth of pathogens in the large intestine?

A

Colonisation resistance by normal gut microflora prevents overgrowth of pathogens. Notably the hospital acquired infection Clostridium difficile

64
Q

When are changes in healthy microbiota in hospital likely to occur?

A

The process usually begins around day 4 of admission; this is why after 4 days of admission the antibiotics for hospital acquiredinfections change. It is not because the severity of the illness isdifferent.

65
Q

What are the benefits of normal flora to metabolism?

A

Synthesis secondary metabolites/vitamins
e.g. vitamins K and B12 secreted by enteric bacteria
Fermenting unused energy substrates (SCFA)

66
Q

What are the benefits of normal flora to colonisation resistance?

A

Environmental manipulation
e.g. low pH
Antibacterial agents
e.g. colicins, bacteriocins, fatty acids, metabolic waste products

EMS (54 decks)

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