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MICROBIO > Respiratory Pathogens > Flashcards

Respiratory Pathogens Flashcards

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
Q

Route of infection of B. Pertussis

A

The organism infects the ciliated epithelial layer of the respiratory tract without invading deeper, resulting in an acute tracheobronchitis

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26
Q

What mediates the action of B. Pertusis? (X2)

A
  • filamentous hemagglutinin (FHA)

- cell bound pertussis toxin (PTx)

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27
Q

What is pertactin (PRN)?

A

The outer membrane protein that promotes the attachment of B. Pertussis to tracheal epithelial cells

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28
Q

What is the outer membrane protein that promotes the attachment of B. Pertussis to tracheal epithelial cells

A

Pertactin

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29
Q

Name 4 toxins involved with bordetella pertussis

A
  1. Pertussis toxin
  2. Adenylate cyclase/hemolysin
  3. Tracheal cytotoxin (TCT)
  4. Lipopolysaccharide (endotoxin)
30
Q

Pathogenesis of B. Pertussis

A
  • Growth on ciliate epithelial and toxin production, killing the ciliate epithelial cells and inducing mucous secretions
  • Stimulates inflammatory response
  • Kills leucocytes
31
Q

What does the action of Pertussis Toxin result in?

A

Kills leucocytes, resulting in disruption of cell function, increased mucous secretion, incapacitating phagocytes function
Systemic consequences: increase in insulin and sensitivity to histamine

32
Q

Diagnosis of Bordetella Pertussis (x2)

A

Hold BG culture plate in front of mouth when coughing

Perinasal swab of posterior pharyngeal walls

33
Q

Treatment of B. Pertussis

A

Erythromycin for 14 days
Skilled nursing, removal of mucous and vomit
Antibiotic therapy for secondary infections
Vaccination

34
Q

Growth requirements of haemophilus influenza (x4)

A
  • chocolate or cooked blood agar
  • aerobic conditions
  • nutritional factor X - haematin
  • nutritional factor V - nicotinamide adenine dinucleotide (NAD)
35
Q

Comparison between haemophilus influenza growth in cooked blood agar plates vs normal blood agar plates

A

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
Q

Appearance of haemophilus influenza

A

Small
Gram negative
Bacillus - considerable pleomorphism
(Non-motile)

37
Q

Route of transmission of H. Influenza

A

Direct contact with patient

Respiratory droplets

38
Q

Name 3 diseases caused by H. Influenza

A
  1. Meningitis
  2. Bronchitis
  3. Pneumonia
39
Q

Mode of action of haemophilus influenza

A

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
Q

Significance of the capsule of haemophilus influenza

A

Polyribosyl Ribotol Phosphate (PRP) capsule protects the bacteria from phagocytosis, reducing its susceptibility to the antibacterial role of serum

41
Q

Name 3 factors promoting the adhesion of haemophilus influenza to mucosa

A
  1. P2 (+ other outer membrane proteins)
  2. Fimbriae / Pili
  3. Non-pilus adhesins
42
Q

What does P2 target?

A

Sialic acid oligosaccharides in mouth

43
Q

What does fimbriae/Pili and non-pilus adhesins target in the adhesion of H. Influenza to mucosa?

A

Mucosal cells of the nasopharynx

44
Q

Treatment of H. Influenza (x2)

A

Antibiotics

Immunisation - Hib (capsule type B) vaccine given at 2,3,4 months

45
Q

Antibiotics for treating H. Influenza caused meningitis

A

Cefotaxime

Cephalosporins e.g. Ceftriaxone

46
Q

Antibiotics for treating H. Influenza caused bronchitis

A

Amoxicillin/Erythromycin

47
Q

Antibiotics for treating H. Influenza caused pneumonia

A

Flucloxacillin / Amoxycillin

48
Q

What is pneumonia?

A

An acute inflammation of the lungs, where the alveoli and branchioles of the lungs become plugged with a fibrous exudate

49
Q

Appearance of Streptococcus Pneumoniae

A

Encapsulated
Gram positive cocci
Oval/lancet shaped
Arranged in pairs (diplococci)

50
Q

Haemolytic activity of strep. Pneumoniae

A

Alpha-hemolytic

51
Q

Is s. Pneumoniae

  • Optochin sensitive/resistant?
  • catalase positive/negative?
A

Optochin sensitive

Catalase negative

52
Q

Who are more likely to present with pneumococcal pneumonia?

A

The very young and very old

53
Q

Mode of action of pneumococcal pneumonia

A
  • 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
Q

Name 5 virulence factors involved in phagocytic survival of S. Pneumoniae

A
  • 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
Q

Symptoms of pneumonia (x6)

A
  • 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
Q

Treatment of pneumonia (x3)

A
  • amoxicillin
  • erythromycin
  • more advanced beta-lactams (eg cephalosporins)
57
Q

Control of pneumonia

A

Vaccination

  • pneumococcal vaccine at 2, 4, 13 months
  • anti-capsular vaccine consisting 23 capsular polysaccharides
58
Q

What is Legionnaires disease caused by?

A

Legionella pneumophila

59
Q

What does legionella pneumophila cause? (X2)

A

Legionnaire’s disease

Pontiac fever

60
Q

Where can legionella be found? (X4)

A
  • circulating water droplets
  • cooling towers
  • warm water baths
  • decorative fountains
61
Q

Route of transmission of legionella

A

Via inhalation of water droplets

No person-person spread

62
Q

What is Legionnaire’s disease?

A

Atypical, acute lobar pneumonia with multi-system symptoms

63
Q

What is Pontiac fever?

A

Non-pneumonic legionellosis

64
Q

Symptoms of Pontiac fever (x5)

A 
Dry cough
Malaise
Headache
Fever
GI problems
65
Q

Describe the appearance of Legionella Pneumophila

A 
Gram negative
Facultative intracellular
Slender unencalsulated rods
Cocco-bacillary appearance 
Strict aerobes
Fastidious
66
Q

Symptoms of Legionnaire’s disease (x6)

A
  • 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
Q

Diagnosis of Legionella pneumophila (x3)

A
  • culturing
  • direct antibody test
  • rRNA identification
68
Q

Treatment of legionella pneumophila

A

Erythromycin/Azithromycin

PONTIAC FEVER IS NOT TREATED

69
Q

Control of legionella

A

Clean water systems
Monitor hot water systems
Hot water to be above 50 deg as bacteria thrive in 20-45deg

70
Q

Name 6 upper respiratory tract infection pathogens

A
  • strep. Pyogenes
  • corynebacterium diphtheria
  • bordetella pertussis
  • haemophilus influenza
  • oral spirochaetes
  • fusobacterium

MICROBIO (16 decks)

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