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MICR2209 > 16 - Airborne bacterial diseases > Flashcards

16 - Airborne bacterial diseases Flashcards

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1
Q

Upper respiratory tract

A
  • Anaerobes outnumber aerobes 10:1
  • May include pathogens in low numbers
  • Contains normal flora
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2
Q

How does normal flora exclude pathogens

A
  • Occupy the same site
  • Secreting bactericidal chemicals that kill pathogens
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3
Q

Lower respiratory tract

A

Maybe sterile (trachea and lungs)

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4
Q

Physical defences of the respiratory tract

A
  • nasal hair
  • mucous layer
  • ciliary action
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5
Q

Chemical defences of the respiratory tract

A

Lysozyme (saliva, tears)

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6
Q

Immunological defences of the respiratory tract

A
  • Alveolar macrophages (lungs)
  • Secretory IgA (saliva, tears)
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7
Q

Mechanical defences of the respiratory tract

A

Cough, sneeze

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8
Q

Pathogen that causes Diphtheria

A

Corynebacterium diphtheriae

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9
Q

Pathogen that causes Legionnaires’ disease

A

Legionella pneumophila

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10
Q

Pathogen that causes Streptococcal diseases

A

Streptococcus pyogenes

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11
Q

Pathogen that causes Pertussis (whooping cough)

A

Bordetella pertussis

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12
Q

Pathogen that causes Tuberculosis

A

Mycobacterium tuberculosis

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13
Q

Pathogens that cause Meningitis

A
  • Neisseria meningitidis
  • Haemophilus influenzae
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14
Q

Pathogens that cause Bacterial pneumonias

A
  • Streptococcus pneumoniae
  • Haemophilus influenzae
  • Legionella sp
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15
Q

Clinical symptoms of Diphtheria

A
  • Pharyngitis (sore throat), fever
  • Swelling of neck, formation of membrane which
    occludes the airway and results in asphyxiation
  • Diphtheria toxin may cause cardiac arrest
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16
Q

Diphtheria transmission

A

Affects unvaccinated people living in crowded conditions via respiratory secretions

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17
Q

Diphtheria treatment and control

A
  • Vaccine containing diphtheria toxoid (inactivated toxin)
  • Antibiotics such as penicillin, erythromycin
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18
Q

Diagnostic characteristics of diphtheria

A
  • Gram-positive rod containing polyphosphate granules
  • Snapping cell division results in cells in palisades (or “Chinese letters”)
  • Fastidious, difficult to grow in the lab
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19
Q

Virulence determinants of diphtheria

A

Diphtheria toxin DT

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20
Q

Characteristics of diphtheria toxin

A
  • Secreted as a polypeptide, chains A and B linked by
    a disulphide bond
  • B contains receptor domain, binds to host cell receptor
  • Toxin taken into cell into endocytic vacuole
  • Vacuole acidifies, B cell transmembrane domain
    allows A chain to enter cytosol
  • A (active enzyme) blocks protein synthesis in host
    cell cytosol
  • Causes death of host cell
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21
Q

Transmission of Legionnaires’ disease (legionellosis)

A
  • Found in soil, water, AC systems, showers, spas
  • Live within amoebae, protozoa, and macrophages
  • Optimum temp 35ºC
  • Spread via aerosols from environment
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22
Q

Diagnostic characteristics of Legionnaires’ disease (legionellosis)

A

Gram negative rods

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23
Q

Clinical symptoms of Legionnaires’ disease (legionellosis)

Study These Flashcards
A
  • High fever, cough, headache, bronchopneumonia
  • Death in 5 to 30% of cases
24
Q

Diagnosis of Legionnaires’ disease (legionellosis)

Study These Flashcards
A
  • Doesn’t grow on blood agar, special media required
  • Serology can be used to detect a rise in antibodies on blood, or legionella antigens in urine
25
Treatment and control of Legionnaires' disease (legionellosis)
- Antibiotics such as macrolides - Prevention depends on identifying and eliminating environmental source
26
Pathogenesis of Legionnaires' disease (legionellosis)
- Bacteria reside inside alveolar macrophages - Tissue destruction via a protease toxin
27
Diseases caused by Streptococcus pyogenes
- Strep throat - Scarlet fever
28
Clinical symptoms of Streptococcus pyogenes
- Pharyngitis, tonsillitis, otitis - Fever
29
Which group is Streptococcus pyogenes
Group A streptococci
30
Streptococcus pyogenes sequelae (poststreptococcal diseases)
- Rheumatoid arthritis - Rheumatic fever (damage to heart valves) - Gangrene - Glomerulonephritis (kidney damage)
31
Treatment of Streptococcus pyogenes
Antibiotics (penicillin)
32
Diagnostic characteristics of Streptococcus pyogenes
- Gram-positive coccus (chains or diplococci) - Beta-haemolytic on blood agar - Antigen detection from throat swabs
33
Virulence factors of Streptococcus pyogenes
- Erythrogenic toxin genes carried in a phage genome - Polysaccharide capsule and M protein inhibit phagocytosis - M protein and other proteins mediate bacterial attachment to host cells
34
Exotoxins of Streptococcus pyogenes
- streptolysin (a haemolysin) - streptokinase (dissolves blood clots)
35
Clinical symptoms of Pertussis (whooping cough)
- Similar to common cold - Mild cough developing into severe whoop/gasp - Death due to apnea (breathing interruption) - Mainly a childhood disease
36
Transmission of Pertussis
- Respiratory droplets - Infections peak in Winter
37
Treatment and control of Pertussis
- Vaccine: acellular subunit vaccines (components of pathogen e.g. pertussis toxin), combined with diphtheria and tetanus - Antibiotics
38
Diagnosis of Pertussis
- Gram negative coccobacillus - Fastidious, difficult to culture - Diagnosis by culture, and PCR for gene encoding pertactin (an outer membrane protein)
39
Virulence determinants of Pertussis
- Filamentous haemagglutinin (FHA) adhesin mediates adhesion to respiratory epithelium - Cytotoxin stops cilia from beating - Pertussis toxin
40
Effects of Pertussis toxin
- Leads to increase in cyclic AMP (cAMP) which impairs function of immune effector cells - Contributes to mucus production - In conjunction with other toxins causes whooping type cough
41
Clinical symptoms of TB
- Weight loss, coughing up bloody sputum - Fatigue, fever, death
42
Treatment and control of TB
- BCG vaccine (live attenuated Mycobacterium bovis) - Antibiotics (limited due to multidrug resistant TB)
43
Epidemiology of TB
- One of the top microbial killers of people world-wide - 1/3 of world’s population infected - In developed countries, most common in homeless, prisons, alcoholics, elderly
44
Diagnostic characteristics of TB
- Gram positive rod, cell wall has high lipid content (mycolic acid) - Extremely slow growth (6-10 weeks on agar plates) - detection of mycobacterium antigens and mycolic acid directly from sputum
45
Virulence determinants of TB
- Cell wall lipids are toxic to host cells and create hydrophobic barrier, protective against host defences - Survives within macrophages
46
Meningitis
Inflammation of brain or spinal cord meninges
47
Clinical symptoms of Meningitis
- Initial respiratory illness - Stiff neck - Onset of coma - Sequelae: blindness, deafness, gangrene - Meningococcemia (systemic infection)
48
Treatment and control of Meningitis
- Antibiotics: immediate treatment is essential - Vaccines: effective against multiple serotypes
49
Diagnostic characteristics of Meningitis
Gram negative diplococci
50
Transmission of Meningitis
- Respiratory secretions from carriers - 5-15% humans carry meningococcus in nasopharynx - Close contact, prisons, student residential halls, bars - Young adults susceptible, as well as children and aged
51
Diagnosis of Meningitis
- Culture organism from cerebral spinal fluid (CSF), blood or throat - PCR, serology
52
Virulence factors of Meningitis
- Attachment and invasion of epithelial cells of the nasopharynx: Type IV pili are required - Establishment of bacteraemia in the bloodstream: capsule protects against phagocytosis - Crossing the meninges: Type IV pili are required
53
Bacterial pneumonias
Lung inflammation, cough, chest pain, fever, difficulty breathing
54
Streptococcus pneumoniae
- Gram positive diplococcus - Main cause of bacterial pneumonia and a leading cause of infectious disease deaths in developed countries - Alpha-haemolytic on blood agar
55
Haemophilus influenzae
- Gram negative rods/coccobacilli - Also causes meningitis - Controlled by Hib vaccine

MICR2209 (26 decks)

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