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Respiratory Pathogens Flashcards

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1
Q

Name 6 pathogens that contribute to lower respiratory tract infections

A
  • haemophilus influenza
  • strep. Pneumoniae
  • legionella pneumophila
  • mycobacterium tuberculosis
  • mycoplasma pneumonia
  • chlamydia pneumonia
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2
Q

What are the two factors that affect the degree of pathogenicity of a disease causing organism?

A
  • the proteins it expresses

- how effectively it can integrate environmental information

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3
Q

What does bacterial adhesion involve?

A

Surface interactions between specific receptors on the mammalian cell membrane (usually carbohydrates) and ligands (usually proteins) on the bacterial surface

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4
Q

What is bacterial invasion?

A

Bacteria invasion refers to the penetration of host cells and tissues, and is mediated by a complex array of molecules called invasins

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5
Q

What molecules mediate bacterial invasion?

A

Invasins

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6
Q

Mechanisms that result in the evasion of host defences (x5)

A
  • immunity at mucosal surfaces
  • destruction of immune cells
  • interference with inflammatory response
  • evasion of innate immunity
  • overcome acquired immune responses
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7
Q

How does the bacteria overcome acquired immune responses?

A

Phase/Antigen variation - switching between on and off forms of a gene / allowing the bacterium to change the sequence of a gene

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8
Q

What are endotoxins?

A

Lipopolysaccharides complexed to proteins that occur in the outer membrane of the envelope of gram negative bacteria

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9
Q

Principal antibody type produced at mucosal surfaces? What molecules cleave these immunoglobulin?

A

IgA

Proteases

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10
Q

Incubation period of Diphtheria

A

2-6 days

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11
Q

What does corynebacterium diphtheria cause/what is it characterised by?

A

Infects mucous membranes (tonsils) - toxin produces acute inflammation and formation of pseudomembrane

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12
Q

Early symptoms of corynebacterium diphtheria

A

Sore throat
Low fever
Swollen neck glands

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13
Q

Late symptoms of corynebacterium diphtheria (x3)

A

Airway obstruction
Difficulty breathing
Shock -> hypotension, tachycardia, pale, cold skin, sweating, anxious

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14
Q

What are diphtheria outbreaks associated with? (X2)

A

Unsanitary/crowded conditions

Immunity gaps, vaccination failure

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15
Q 
Is corynebacterium diphtheria 
I) gram positive or gram negative
II) cocci or bacilli
III) aerobic or anaerobic
IV) motile or non-motile
V) growth medium
A 
Gram positive
Bacilli
Aerobic
Non-motile 
Grows in tellurite agar, which is toxic for other throat flora
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16
Q

How is corynebacterium diphtheria transmitted?

A

Direct contact droplets/skin

Indirect via contaminated object

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17
Q

Treatment of Diphteria (x2)

A
  • immediate inoculation with diphtheria anti-toxin

- administer penicillin or erythromycin to eliminate the bacteria

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18
Q

Prevention of diphtheria

A

Active immunisation

Diphtheria Formal Toxoid (DFT Vaccine) - part of multiple vaccine - given at 2,3,4 months ; booster jab at 5 years

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19
Q

How does diphtheria enters the cell?

A

Endocytosis - proteolytic cleavage takes place in the cell, resulting in 2 fragments

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20
Q

Which bacteria causes whooping cough?

A

Bordetella Pertusis

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21
Q

Describe the appearance of B. Pertussis (x3)

A

Small,
Gram-negative
Cocci

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22
Q

Transmission of Bordetella Pertussis

A

Infection by exposure to infected individual

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23
Q

Clinical features of B. Pertussis infection (x4)

A
  • insidious onset
  • catarrhal stage with common cold symptoms
  • paroxysmal coughing
  • residual cough
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24
Q

What may adults suffering from bordetella pertussis experience? (X4)

A
  • shortness of breath during coughing
  • nocturnal coughing
  • tingling sensation in back of throat
  • post-tussive vomitting
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25
Route of infection of B. Pertussis
The organism infects the ciliated epithelial layer of the respiratory tract without invading deeper, resulting in an acute tracheobronchitis
26
What mediates the action of B. Pertusis? (X2)
- filamentous hemagglutinin (FHA) | - cell bound pertussis toxin (PTx)
27
What is pertactin (PRN)?
The outer membrane protein that promotes the attachment of B. Pertussis to tracheal epithelial cells
28
What is the outer membrane protein that promotes the attachment of B. Pertussis to tracheal epithelial cells
Pertactin
29
Name 4 toxins involved with bordetella pertussis
1. Pertussis toxin 2. Adenylate cyclase/hemolysin 3. Tracheal cytotoxin (TCT) 4. Lipopolysaccharide (endotoxin)
30
Pathogenesis of B. Pertussis
- Growth on ciliate epithelial and toxin production, killing the ciliate epithelial cells and inducing mucous secretions - Stimulates inflammatory response - Kills leucocytes
31
What does the action of Pertussis Toxin result in?
Kills leucocytes, resulting in disruption of cell function, increased mucous secretion, incapacitating phagocytes function Systemic consequences: increase in insulin and sensitivity to histamine
32
Diagnosis of Bordetella Pertussis (x2)
Hold BG culture plate in front of mouth when coughing | Perinasal swab of posterior pharyngeal walls
33
Treatment of B. Pertussis
Erythromycin for 14 days Skilled nursing, removal of mucous and vomit Antibiotic therapy for secondary infections Vaccination
34
Growth requirements of haemophilus influenza (x4)
- chocolate or cooked blood agar - aerobic conditions - nutritional factor X - haematin - nutritional factor V - nicotinamide adenine dinucleotide (NAD)
35
Comparison between haemophilus influenza growth in cooked blood agar plates vs normal blood agar plates
Larger colonies are produced in cooked blood agar than in normal blood agar. This is because the V factor, Nicotinamide adenine dinucleotide, is imprisoned in intact RBCs
36
Appearance of haemophilus influenza
Small Gram negative Bacillus - considerable pleomorphism (Non-motile)
37
Route of transmission of H. Influenza
Direct contact with patient | Respiratory droplets
38
Name 3 diseases caused by H. Influenza
1. Meningitis 2. Bronchitis 3. Pneumonia
39
Mode of action of haemophilus influenza
Bacteria attaches to epithelial cells and penetrates sub mucosa of the nasopharynx, causing local inflammation and swelling. It can then spread from the initial site to infect bones, joints and CNS.
40
Significance of the capsule of haemophilus influenza
Polyribosyl Ribotol Phosphate (PRP) capsule protects the bacteria from phagocytosis, reducing its susceptibility to the antibacterial role of serum
41
Name 3 factors promoting the adhesion of haemophilus influenza to mucosa
1. P2 (+ other outer membrane proteins) 2. Fimbriae / Pili 3. Non-pilus adhesins
42
What does P2 target?
Sialic acid oligosaccharides in mouth
43
What does fimbriae/Pili and non-pilus adhesins target in the adhesion of H. Influenza to mucosa?
Mucosal cells of the nasopharynx
44
Treatment of H. Influenza (x2)
Antibiotics | Immunisation - Hib (capsule type B) vaccine given at 2,3,4 months
45
Antibiotics for treating H. Influenza caused meningitis
Cefotaxime | Cephalosporins e.g. Ceftriaxone
46
Antibiotics for treating H. Influenza caused bronchitis
Amoxicillin/Erythromycin
47
Antibiotics for treating H. Influenza caused pneumonia
Flucloxacillin / Amoxycillin
48
What is pneumonia?
An acute inflammation of the lungs, where the alveoli and branchioles of the lungs become plugged with a fibrous exudate
49
Appearance of Streptococcus Pneumoniae
Encapsulated Gram positive cocci Oval/lancet shaped Arranged in pairs (diplococci)
50
Haemolytic activity of strep. Pneumoniae
Alpha-hemolytic
51
Is s. Pneumoniae - Optochin sensitive/resistant? - catalase positive/negative?
Optochin sensitive | Catalase negative
52
Who are more likely to present with pneumococcal pneumonia?
The very young and very old
53
Mode of action of pneumococcal pneumonia
- invasion of lower respiratory tract by aerosol - normally bypass ciliated epithelial - progress to alveolar and cell wall - promotes binding to cells expressing the platelet activating factor receptor - teichoic acids are exposed on cell surface and present in the cell wall - overcomes IgA through secretion of proteases - overcomes mucociliary escalator by the production of cytotoxin that kills ciliated epithelial cells (pneumolysin) - bacteria multiplies in nutrient-rich oedema fluid - erythrocytes, neutrophils and macrophages accumulate as the fluid becomes purulent
54
Name 5 virulence factors involved in phagocytic survival of S. Pneumoniae
- cell wall initiates inflammation - teichoic acid activates C5a and alternative complement pathway - pneumolysin - pore forming (type II) toxin - disrupts membrane and inhibits oxidative burst - hydrogen peroxide - phosphorycholine - present on cell wall; binds to PAF receptor and induces receptor mediated endocytosis - capsule
55
Symptoms of pneumonia (x6)
- normally preceded by 1-3 days of viral respiratory infection - abrupt onset - severe shaking chill, sustained fever at 39-41deg - productive cough with blood tinged sputum - chest pain - lobar pneumonia - confined to lower alveolar lobes - 5% mortality rate - bacteraemia may occur, in 25-30% of patients with pneumonia
56
Treatment of pneumonia (x3)
- amoxicillin - erythromycin - more advanced beta-lactams (eg cephalosporins)
57
Control of pneumonia
Vaccination - pneumococcal vaccine at 2, 4, 13 months - anti-capsular vaccine consisting 23 capsular polysaccharides
58
What is Legionnaires disease caused by?
Legionella pneumophila
59
What does legionella pneumophila cause? (X2)
Legionnaire's disease | Pontiac fever
60
Where can legionella be found? (X4)
- circulating water droplets - cooling towers - warm water baths - decorative fountains
61
Route of transmission of legionella
Via inhalation of water droplets | No person-person spread
62
What is Legionnaire's disease?
Atypical, acute lobar pneumonia with multi-system symptoms
63
What is Pontiac fever?
Non-pneumonic legionellosis
64
Symptoms of Pontiac fever (x5)
``` Dry cough Malaise Headache Fever GI problems ```
65
Describe the appearance of Legionella Pneumophila
``` Gram negative Facultative intracellular Slender unencalsulated rods Cocco-bacillary appearance Strict aerobes Fastidious ```
66
Symptoms of Legionnaire's disease (x6)
- cough, fever, swears, loss of appetite, headache, general pains - rapidly degenerates, yellow/green sputum can be stained with blood - tight chest, breathlessness, sharp pain in the side of chest - confusion and diarrhoea - complications: heart, brain, kidneys
67
Diagnosis of Legionella pneumophila (x3)
- culturing - direct antibody test - rRNA identification
68
Treatment of legionella pneumophila
Erythromycin/Azithromycin | PONTIAC FEVER IS NOT TREATED
69
Control of legionella
Clean water systems Monitor hot water systems Hot water to be above 50 deg as bacteria thrive in 20-45deg
70
Name 6 upper respiratory tract infection pathogens
- strep. Pyogenes - corynebacterium diphtheria - bordetella pertussis - haemophilus influenza - oral spirochaetes - fusobacterium

MICROBIO (16 decks)

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