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Flashcards in Respiratory Pathogens Deck (70):
1

Name 6 pathogens that contribute to lower respiratory tract infections

- haemophilus influenza
- strep. Pneumoniae
- legionella pneumophila
- mycobacterium tuberculosis
- mycoplasma pneumonia
- chlamydia pneumonia

2

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

- the proteins it expresses
- how effectively it can integrate environmental information

3

What does bacterial adhesion involve?

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

4

What is bacterial invasion?

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

5

What molecules mediate bacterial invasion?

Invasins

6

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

- immunity at mucosal surfaces
- destruction of immune cells
- interference with inflammatory response
- evasion of innate immunity
- overcome acquired immune responses

7

How does the bacteria overcome acquired immune responses?

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

8

What are endotoxins?

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

9

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

IgA
Proteases

10

Incubation period of Diphtheria

2-6 days

11

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

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

12

Early symptoms of corynebacterium diphtheria

Sore throat
Low fever
Swollen neck glands

13

Late symptoms of corynebacterium diphtheria (x3)

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

14

What are diphtheria outbreaks associated with? (X2)

Unsanitary/crowded conditions
Immunity gaps, vaccination failure

15

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

Gram positive
Bacilli
Aerobic
Non-motile
Grows in tellurite agar, which is toxic for other throat flora

16

How is corynebacterium diphtheria transmitted?

Direct contact droplets/skin
Indirect via contaminated object

17

Treatment of Diphteria (x2)

- immediate inoculation with diphtheria anti-toxin
- administer penicillin or erythromycin to eliminate the bacteria

18

Prevention of diphtheria

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

19

How does diphtheria enters the cell?

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

20

Which bacteria causes whooping cough?

Bordetella Pertusis

21

Describe the appearance of B. Pertussis (x3)

Small,
Gram-negative
Cocci

22

Transmission of Bordetella Pertussis

Infection by exposure to infected individual

23

Clinical features of B. Pertussis infection (x4)

- insidious onset
- catarrhal stage with common cold symptoms
- paroxysmal coughing
- residual cough

24

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

- shortness of breath during coughing
- nocturnal coughing
- tingling sensation in back of throat
- post-tussive vomitting

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