How Micro-Organisms Cause Disease

Front 1

What are 3 ways in which microbes cause disease?

Back 1

1. Contact or enter host cells and directly kill them (e.g. viruses inhibiting cellular nucleic acid synthesis &/or causing cell lysis)
2. Release factors that indirectly kill cells (e.g. exotoxins & endotoxins)
3. Induce a host response that harms the host as well as the microorganism (e.g. suppuration, scarring, allergic reaction)

Front 2

What are the 2 main types of acute inflammatory responses to infection?

Back 2

Suppurative
(pus formation, with
oedema, fibrin, neutrophils…)
E.g. Acute lobar pneumonia:
1. Congestion & Consolidation
2. Red hepatisation
3. Grey hepatisation
4. Resolution or organisation

Necrotizing
(rapid/severe tissue destruction; little time for inflammation)
E.g. Clostridium perfringens (strong
toxins)

Front 3

What are the 3 main types of chronic inflammatory responses to infection?

Note: One type has 2 sub-types.

Back 3

Cytopathic & Cytoproliferative
(viral damage in the absence of host inflammatory response)
E.g.
• Inclusion bodies (CMV);
• Cell fusion (RSV);
• Blisters (HSV);
• Cell proliferation (warts)

Mononuclear & Granulomatous
1. Mononuclear
• Lymphocytes (e.g. viral)
• Plasma cells (e.g. syphilis)
2. Granulomatous
• Slow-dividing organisms (e.g. TB)
• Large size (e.g. helminths)

Chronic Inflammation & Scarring

Front 4

What are 3 ways in which microbes cause disease?

Back 4

1. Contact or enter host cells and directly kill them (e.g. viruses inhibiting cellular nucleic acid synthesis &/or causing cell lysis)
2. Release factors that indirectly kill cells (e.g. exotoxins & endotoxins)
3. Induce a host response that harms the host as well as the microorganism (e.g. suppuration, scarring, allergic reaction)

Front 5

What are the 2 main types of acute inflammatory responses to infection?

Back 5

Suppurative
(pus formation, with
oedema, fibrin, neutrophils…)
E.g. Acute lobar pneumonia:
1. Congestion & Consolidation
2. Red hepatisation
3. Grey hepatisation
4. Resolution or organisation

Necrotizing
(rapid/severe tissue destruction; little time for inflammation)
E.g. Clostridium perfringens (strong
toxins)

Front 6

What are the 3 main types of chronic inflammatory responses to infection?

Note: One type has 2 sub-types.

Back 6

Cytopathic & Cytoproliferative
(viral damage in the absence of host inflammatory response)
E.g.
• Inclusion bodies (CMV);
• Cell fusion (RSV);
• Blisters (HSV);
• Cell proliferation (warts)

Mononuclear & Granulomatous
1. Mononuclear
• Lymphocytes (e.g. viral)
• Plasma cells (e.g. syphilis)
2. Granulomatous
• Slow-dividing organisms (e.g. TB)
• Large size (e.g. helminths)

Chronic Inflammation & Scarring

Front 7

Upper Respiratory Tract diseases
Acute otitus media: Name infecting organisms, with corresponding comments

Note: Acute Sinusitis has similar aetiology and pathogenesis.

Back 7

Viruses
(esp. Respiratory syncytial virus)
[Cause at least 50% of URTs]

Streptococcus pneumoniae
Haemophilus influenzae
Moraxella catarrhalis
Streptococcus pyogenes
Staphylococcus aureus
[Generally secondary infection; most commonly nasopharyngeal residents; fluid often stays in middle ear for weeks to months (glue ears)]

Front 8

Upper Respiratory Tract diseases
Otitus externa: Name infecting organisms, with corresponding comments

Back 8

Staphylococcus aureus
Candidiasis albicans
Gram -ve pathogens
[External ear canal contains normal flora, warm moist environment]

Front 9

Upper Respiratory Tract diseases
Acute epiglottis: Name infecting organisms, with corresponding comments

Back 9

Haemophilus influenzae (type b)
[Organism spreads from nasopharynx to epiglottis]

Front 10

Upper Respiratory Tract diseases
Pharyngitis: Name infecting organisms, with corresponding comments

Back 10

Viruses
[Cause ~70% of sore throats]

Streptococcus pyogenes
[10-20% acute cases, sudden onset]

Neisseria gonorrahoeae
[Often asymptomatic, usu. via orogenital contact]

Corynebacterium diphtheriae
[Mild but toxic illness, can be severe]

Haemophilus influenzae
[Epiglottis]

Front 11

Name 4 normal flora of the mouth

Back 11

Streptococcus mitis & other Streptococci (including Viridans)
Candida albicans
Bacteroides spp.
Lactobacillus spp.

Front 12

Name 7 normal flora of the nasal cavity and throat

Back 12

Staphylococcus epidermidis
Staphylococcus aureus (carriers)
Streptococci (including Viridans)
Corynebacterium spp.
Moraxella spp.
Haemophilus spp.
Neisseria spp.

Front 13

Name 3 pathogens of the mouth

Back 13

Fusobacterium spp.
Actinomyces
Candida albicans (opportunistic infection)

Front 14

Name 7+ pathogens of the nasal cavity and throat

Back 14

Staphylococcus aureus
Streptococcus pyogenes
Corynebacterium diphtheriae
Haemophilus influenzae
Streptococcus pneumoniae
Moraxella catarrhalis
Viruses: e.g. adenoviruses, rhinoviruses, influenza, RSV…

Front 15

Streptococcus pyogenes (Group A Strep)
Describe bacteria, disease, and complications

Back 15

• Gram +ve cocci, β – haemolytic, bacitracin sensitive
• Major cause of pharyngitis (‘strep throat’)
• Complications include otitis media, sinusitis, acute
glomerulonephritis, scarlet fever & rheumatic fever

Front 16

Streptococcus pyogenes (Group A Strep)
Describe virulence factors

Back 16

Front 17

Streptococcus pneumoniae:
Describe virulence factors

Back 17

Front 18

Streptococcus pneumoniae
Describe bacteria, disease, and complications

Back 18

• Gram +ve cocci, α – haemolytic, optochin sensitive
• Acute otitis media, sinusitis, LRTI’s (pneumonia), meningitis
• 23-valent & 7-valent vaccines available (23-valent doesn’t work in children < 2 yrs old)

Front 19

Haemophilus influenzae:
Describe bacteria, disease, complications, and virulence factors

Back 19

• Gram –ve rods, can be capsulated or non-capsulated
• Acute otitis media, sinusitis, epiglottitis, LRTI’s (pneumonia), meningitis…
• Virulence factors: capsule, outer membrane proteins, endotoxin, fimbrial & non-fimbrial adhesins,
IgA protease, autolysins
• Hib vaccine available (against type b capsule); however, non-typable strains have ~40-80% nasopharyngeal carriage, and are a significant cause of otitis media

Front 20

Moraxella catarrhalis:
Describe bacteria, disease, complications, and virulence factors

Back 20

• Gram –ve coccobacilli
• Acute otitis media & sinusitis in children (especially high colonization/carriage rates in indigenous children)
• Virulence factors: Capsule, outer membrane proteins, adhesins, endotoxin

Front 21

Corynebacterium diphtheriae:
Describe bacteria, disease, complications, and virulence factors

Back 21

• Gram +ve rods (distinctive black colonies on tellurite agar)
• Diphtheria – rare in developed world
• Virulence factors: diphtheria toxin (inhibits protein synthesis); toxoid = basis for vaccination

Front 22

What is over 50% of the "common cold" cases caused by?

Back 22

Rhinoviruses and coronaviruses

Front 23

What can Viral Upper Resp Tract Infection (URTI) can progress to?

Back 23

Viral pneumonia

Front 24

Viral respiratory infections:
"Restricted to surface" types
- Give examples
- Name consequences

Back 24

Common cold viruses
Influenza
Streptococci in throat
Candida albicans (thrush)

Local spread
Local (mucosal) defenses important
Adaptive (immune) response sometimes too late to be important in recovery
Short incubation period (days)

Front 25

Viral respiratory infections:
"Spread through body" types
- Give examples
- Name consequences

Back 25

Measles, munmps, rubella
Q fever

Little or no lesion at entry site
Microbe spreads through body, returns to surface for finall multiplication and shedding, e.g. salivary glands (mumps, CMV, EBV), resp tract (measles)
Adaptive immune responce important in recovery
Longer incubation period (weeks)

Front 26

Which levels of the respiratory tract can resp viruses infect?

Back 26

Any level, although preferred sites exist
- e.g. URT for Rhinoviruses.

Front 27

List 6 antimicrobial defences in resp system, and the factors that impair each one.

Back 27

1. Cough reflex (stroke, brain tumours, laryngeal cancer, etc.)
2. Filtering by nasal cavity
3. Mucociliary action (impaired by viral infection, cigarette smoke, etc.)
4. Phagocytosis by alveolar macrophages (smoke, alcohol, oedema, etc.)
5. General host immunity (immunosuppressed states)
6. Normal flora - URT only

Front 28

UP TO CASE 10 P19 - PATHOPLYSIOLOGY OF MIDDLE...

Back 28

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