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MICR2209 > 16 - Airborne bacterial diseases > Flashcards

16 - Airborne bacterial diseases Flashcards

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)

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

Diagnosis of Legionnaires’ disease (legionellosis)

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
Q

Treatment and control of Legionnaires’ disease (legionellosis)

A
  • Antibiotics such as macrolides
  • Prevention depends on identifying and eliminating environmental source
26
Q

Pathogenesis of Legionnaires’ disease (legionellosis)

A
  • Bacteria reside inside alveolar macrophages
  • Tissue destruction via a protease toxin
27
Q

Diseases caused by Streptococcus pyogenes

A
  • Strep throat
  • Scarlet fever
28
Q

Clinical symptoms of Streptococcus pyogenes

A
  • Pharyngitis, tonsillitis, otitis
  • Fever
29
Q

Which group is Streptococcus pyogenes

A

Group A streptococci

30
Q

Streptococcus pyogenes sequelae (poststreptococcal diseases)

A
  • Rheumatoid arthritis
  • Rheumatic fever (damage to heart valves)
  • Gangrene
  • Glomerulonephritis (kidney damage)
31
Q

Treatment of Streptococcus pyogenes

A

Antibiotics (penicillin)

32
Q

Diagnostic characteristics of Streptococcus pyogenes

A
  • Gram-positive coccus (chains or diplococci)
  • Beta-haemolytic on blood agar
  • Antigen detection from throat swabs
33
Q

Virulence factors of Streptococcus pyogenes

A
  • 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
Q

Exotoxins of Streptococcus pyogenes

A
  • streptolysin (a haemolysin)
  • streptokinase (dissolves blood clots)
35
Q

Clinical symptoms of Pertussis (whooping cough)

A
  • Similar to common cold
  • Mild cough developing into severe whoop/gasp
  • Death due to apnea (breathing interruption)
  • Mainly a childhood disease
36
Q

Transmission of Pertussis

A
  • Respiratory droplets
  • Infections peak in Winter
37
Q

Treatment and control of Pertussis

A
  • Vaccine: acellular subunit vaccines (components of pathogen e.g. pertussis
    toxin), combined with diphtheria and tetanus
  • Antibiotics
38
Q

Diagnosis of Pertussis

A
  • Gram negative coccobacillus
  • Fastidious, difficult to culture
  • Diagnosis by culture, and PCR for gene encoding
    pertactin (an outer membrane protein)
39
Q

Virulence determinants of Pertussis

A
  • Filamentous haemagglutinin (FHA) adhesin mediates
    adhesion to respiratory epithelium
  • Cytotoxin stops cilia from beating
  • Pertussis toxin
40
Q

Effects of Pertussis toxin

A
  • 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
Q

Clinical symptoms of TB

A
  • Weight loss, coughing up bloody sputum
  • Fatigue, fever, death
42
Q

Treatment and control of TB

A
  • BCG vaccine (live attenuated Mycobacterium bovis)
  • Antibiotics (limited due to multidrug resistant TB)
43
Q

Epidemiology of TB

A
  • 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
Q

Diagnostic characteristics of TB

A
  • 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
Q

Virulence determinants of TB

A
  • Cell wall lipids are toxic to host cells and create hydrophobic barrier, protective against host defences
  • Survives within macrophages
46
Q

Meningitis

A

Inflammation of brain or spinal cord meninges

47
Q

Clinical symptoms of Meningitis

A
  • Initial respiratory illness
  • Stiff neck
  • Onset of coma
  • Sequelae: blindness, deafness, gangrene
  • Meningococcemia (systemic infection)
48
Q

Treatment and control of Meningitis

A
  • Antibiotics: immediate treatment is essential
  • Vaccines: effective against multiple serotypes
49
Q

Diagnostic characteristics of Meningitis

A

Gram negative diplococci

50
Q

Transmission of Meningitis

A
  • 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
Q

Diagnosis of Meningitis

A
  • Culture organism from cerebral spinal fluid (CSF),
    blood or throat
  • PCR, serology
52
Q

Virulence factors of Meningitis

A
  • 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
Q

Bacterial pneumonias

A

Lung inflammation, cough, chest pain, fever, difficulty breathing

54
Q

Streptococcus pneumoniae

A
  • 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
Q

Haemophilus influenzae

A
  • Gram negative rods/coccobacilli
  • Also causes meningitis
  • Controlled by Hib vaccine

MICR2209 (26 decks)

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