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Microbiome > MHD9 Respiratory microbiota > Flashcards

MHD9 Respiratory microbiota Flashcards

1
Q

What three parts make up the pharynx?

A

nasopharynx
oropharynx
epiglottis

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2
Q

Name all of the components of the respiratory system from top to bottom

A 
Nasal cavity
Pharynx (nasopharynx
oropharynx
epiglottis)
oral cavity
larynx
oesophagus
trachea
bronchi
lung
stomach
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3
Q

Describe the function of the pharynx

A

A part of the throat that is behind the mouth and nasal cavity

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4
Q

Describe the function of the nasopharynx

A

The upper part of the throat that lies behind the nose

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5
Q

Describe the function of the oropharynx

A

A part of the pharynx between the nasopharynx and the epiglottis

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6
Q

Describe the function of the epiglottis

A

A flap of elastic cartilage in the throat that prevents food from entering the trachea

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7
Q

Describe the function of the larynx

A

The voice box

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8
Q

Describe the function of the oesophagus

A

Commonly known as food pipe

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9
Q

Describe the function of the trachea

A

The windpipe

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10
Q

Describe the function of the bronchi

A

Conducts the air into the lungs

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11
Q

On each breath, how much of the air is exchanged?

A

~Roughly 20%

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12
Q

Describe how microbial colonisation of lower airways occurs

A

The upper airways are covered in a layer of mucus, this mucus and resident & inhaled microbes, flows with salvia into the GI tract. Whilst air is diverted into the trachea. A significant number of aerosols are created from the constant flow of air and fluid. The microaspiration of these aerosols is responsible for much of the microbial colonisation of the lower airways

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13
Q

What temperature are the upper trachea and bronchi compared to core body temperature?

A

Lower; due to cold air drawn in

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14
Q

What is the total SA of the bronchial?

A

70m^2

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15
Q

What are alveoli coated in?

A

surfactant, lipid-rich lipoprotein complex (phospholipoprotein)

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16
Q

What is the pH of the stomach, duodenum, terminal ileum, caecum and rectum?

A 
stomach 2
duodenum 6
terminal ileum 7.4
caecum 5.7
rectum 6.7
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17
Q

What is the pH of the lungs?

A

7.4, very similar to the blood

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18
Q

Where is the migration of microbes under healthy conditions in respirational systems vs Gastrointestinal system?

A

RS
Bidirectional:
- the mucus and the vast majority of the resident and inhaled microbes flow with saliva into the GI tract
- the mucus from the bronchial tree flows towards the oropharynx

GI
Unidirectional
- From the mouth to the anus

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19
Q

What is the SA of GI?

A

32m^2

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20
Q

What are the O2 levels in GI and RS?

A

GI: very low, mostly anaerobic
RS: aerobic in healthy condition

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21
Q

Which location in RS has highest amount of Firmicutes?

A

Nasal

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22
Q

Which location in RS has highest amount of Bacteroidetes?

A

Lung

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23
Q

Which location in RS has highest amount of Actinobacteria?

A

Nasal

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24
Q

What are the most dominant members of the nasal microbiota?

A

Propionibacteria
Corynebacteria
Staphylococcus
Moraxella

25
Q

What species have been identified in the nasal cavity?

A 
Propionibacteria acnes
Corynebacteria accolens
Corynebacteria kropenstedtii
Staphylococcus aureus
Staphylococcus epidermitidis
26
Q

How does the nasal microbiome alter in diseased status?

A

Significantly different microbiotia in individuals with exacerbated asthma, nonexacerbated asthma and heathy controls

27
Q

What four species of bacteria are associated with asthma activity?

A

Prevotella buccalis
Dialister invisus
Gardnerella vaginalis
Alkanindiges hongkongensis

28
Q

Name the different bacterial habits in the human mouth

A 
teeth
sift palate
tonsil
hard palate
uvula
cheek
tongue
gingiva (gum)
29
Q

How many different species are there in the oral cavity?

A

Around 600, with different clusters of microbes dominating at different oral habitats

30
Q

What species of bacteria are commonly detected in the mouth?

A 
Prevotella
Veillonella
Streptococcus
Haemophilus
Fusobacterium
Neisseria
Corynebacteria
31
Q

What metabolites have been observed in human saliva? How were these detected?

A

NMR and MS techniques

  • short chain organic acids (e.g. acetate, acetoacetate, butyrate, citrate, formate, lactate, propionate and pyruvate)
  • amino acids (e.g. alanine, valine, phenylalanine, methionine)
  • amines (e.g. dimethylamine, methylamine), sugars, etc.
32
Q

Relative to the gut, what is the bacterial biomass of the lungs?

A

Low
Ranging from 4.5 to 8.25 log copies per/ml in the bronchoalveolar lavage
1-10 bacterial cells/100 human cells

33
Q

The composition of the lung microbiome is determined by what three main factors?

A

1) microbial immigration
2) microbial elimination
3) local growth environment

34
Q

Where have potential sources of the lung microbiota arisen from? (microbial immigration)

A

Inhaled air, microaspiration, and direct dispersion through the respiratory tract mucosa
(2nd and 3rd are the major sources)

35
Q

the human lung microbiome of a healthy individual is more similar to _______, compared with the microbiome of the inhaled air, the nasopharynx or the lower gastrointestinal tract

A

the oropharynx microbiome

36
Q

What usually contributes little to lung communities in healthy individuals?

A

Nasal microbiota

37
Q

When may the lung microbiome e more similar to the nasal?

A

in certain diseases, for example rhinorrhea, a condition where the nasal cavity is filled with a significant amount of mucus fluid

38
Q

What is the primary source of the bacteria composition of the lungs?

A

The oral microbiome

-> onstant flow of saliva carrying resident and ingested oral microbes (~2 litres per day!)

39
Q

What are the predominant phyla in the lungs?

Kings Play Chess On Fine Glass Sets

A

Bacteroidetes and Firmicutes

40
Q

What are the dominant bacteria genera in the lower airways?

A

Prevotella, Veillonella, Streptococcus, Fusobacteria and Haemophilus, particularly with Prevotella spp

41
Q

What is microbial elimination is determined by?

A

Mucociliary clearance, cough and immune status

42
Q

What can markedly affect the dynamics of microbial elimination from the airways, increase airway temperatures and also create anaerobic zones for microbial growth in the lungs?

A

Diseases or activities such as chronic obstructive pulmonary disease that destroy ciliary function, reduce the cough reflex, increase lower airway mucus secretion or increase the viscosity of the mucus.

43
Q

What type of bacteria dominates the nasal cavity?

A

Firmicutes and Actinobacteria

44
Q

What can lung disease do to the microbial population

A

Microbial immigration, microbial elimination and the local growth environment of the microbial ecosystem of the lung

45
Q

What is COPD?

A

Chronic obstructive pulmonary disease (COPD) is characterised by chronic inflammation of the small airways and is the third leading cause of death worldwide

46
Q

What are the main features of COPD?

A

Although repeated airway infection and hypersecretion of mucus are the main features of COPD, the relationship between COPD exacerbation and acute bacterial infection of the airway is disputed

47
Q

What bacteria are in relatively high abundance increased during exacerbations in contrast to periods of clinical stability of COPD?

A

Relative abundances of Haemophilus, Pseudomonas and Moraxella increased during exacerbations in contrast to periods of clinical stability

48
Q

Does exposure to viruses increase risk to COPD?

Explain

A

May also increase the risk of COPD exacerbations, but the link between viral infection, microbiome composition and the ability of host immune defence remain poorly understood: they found that sputum acquired post viral exposure (in this case it is (rhinovirusexposure)) exhibited a shift towards the Proteobacteria phylum, suggesting a complex crosstalk among virus, bacteria and the host, and providing a potential explanation for the increased presence of Pseudomonas spp. observed in COPD patients during exacerbations.

49
Q

Explain the asthma

A

Airways narrow and swell and produce extra mucus. This can make breathing difficult and trigger coughing, wheezing and shortness of breath. It is a common, long-term or chronic, inflammatory disease of the airways of the lungs. It affects about 5 million people in the UK.

50
Q

What are the changes in microbial composition of asthma patients?

A

Proteobacteria, in particular Haemophilus in the bronchial tree are higher in asthma patients compared with controls, and there is a decrease in Bacteroidetes. Airway microbiome of asthmatic patients was more diverse that non-asthmatic controls.

51
Q

What do Moraxella catarrhalis, Haemophilus influenzae, or Streptococcus pneumoniae have in common?

A

Cultured from the oropharynx samples obtained from one-month old infants and found that these bacteria were associated with a significant increase in their odds ratio. These organisms are also strongly associated with asthma exacerbations.

52
Q

The gut-lung axis is mainly mediated by what?

A

The immune response

53
Q

Describe the immune response of unhealthy of an unhealthy gut-lung axis

A

The unbalanced microbial community fails to prime the DC and then affect the proliferation and activation of T cell subsets, as well as impaired T cell homing. This may result in impaired innate immunity and pulmonary infection. In addition, production of bacterial[BEL1] metabolites such as short chain fatty acids could also affect the gut-lung axis as these products get to the lung and alter the inflammatory environment. The bar on the bottom of the figure shows the factors that can influence the gut microbial composition and activity, including diet, antibiotics and GI infection.

54
Q

Describe the immune response of unhealthy of an unhealthy gut-lung axis

A

The unbalanced microbial community fails to prime the DC and then affect the proliferation and activation of T cell subsets, as well as impaired T cell homing. This may result in impaired innate immunity and pulmonary infection. In addition, production of bacterial[BEL1] metabolites such as short chain fatty acids could also affect the gut-lung axis as these products get to the lung and alter the inflammatory environment. The bar on the bottom of the figure shows the factors that can influence the gut microbial composition and activity, including diet, antibiotics and GI infection.

55
Q

What is one of the major challenges in studying the lung microbiome?

A

The avoidance of contamination: due to the high sensitivity of the next generation sequencing methods and polymerase chain reaction (PCR), slight contamination from the mouth could result in false readouts.

56
Q

How are lung microbiome samples collected?

A

bronchoscope and it remains difficult to avoid the contamination from the oral cavity when passing the bronchoscope through the mouth.

57
Q

What may a solution be to avoiding false readouts from lung samples?

A

Researchers have used two bronchoscopes and the statistical methods to select organism enriched in the lung, but no one approach is widely accepted and used for controlling the contamination.

58
Q

Who could have a higher risk of developing infection in the airway?

A

Someone who has had bowel disease for a prolonged period. His microbial composition and activity are likely to be unbalanced. This would affect the immune system and hence increase the risk of developing respiratory disease.

59
Q

What is the best practice for avoiding contamination in the samples for microbiome studies?

A

Using sterile tool

Microbiome (10 decks)

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