M22 - Pathogens of the Resp tract 2

Question 1

What bacteria are involved in upper respiratory tract infections?

Answer 1

– Streptococcus pyogenes
– Corynebacterium diptheria
– Bordetella pertusis
– Haemophilus influenza

Question 2

What bacteria are involved in lower respiratory tract infections?

Answer 2

– Haemophilus influenza

– Streptococcus pneumoniae

Question 3

What range of disease does haemophilia influenza cause?

Answer 3

–  Epiglotitis
–  Bacteremia
–  Sinusitis
–  Tracheobronchitis
–  Pneumoniae
–  Cellulitis
–  Meningitis

Question 4

Describe some features of haemophilus influenza.

Answer 4

•  Exclusive human parasite
–  Difficult to observe,
–  Small, pleomorphic, Gram-ve bacilli 
–  non-motile
–  Specific growth requirements

Question 5

Describe the non-invasive H.influenza (75% carriage).

Answer 5

– H. influenzae non-encapsulated strains
– Opportunistic infection of ear, sinuses, or eye
– Secondary invaders of damaged tissue e.g. virus, smoking, mucocilliary escalator impaired
– Bronchopneumonia & chronic bronchitis

Question 6

Describe the invasive H.influenza (2-3% carriage).

Answer 6

– Capsulate strain causes acute primary infections
– Sore throat with fever, may obstruct airway
– Pneumonia, Bacteremia, Purulent Arthritis, Meningitis

Question 7

Describe how an individual is infected with H.influenza.

Answer 7

– Infection from respiratory droplet or direct contact with patient
– Bacteria attach to epithelial cells
– Organism penetrates to submucosa (nasopharynx)
– Causes local inflammation & swelling
– 50% of cases present as headache, fever & stiff neck
– Usually confined to epiglottis, facial & neck tissue
– Spreads from initial site to infect bones, joints, CNS

Question 8

Describe features of meningitis.

Answer 8

• Winter disease (commonest)
• Children 2 months to 2 years
– (gap between maternal Antibody & raising of Antibody to capsule)
• 6% Mortality, 20% of survivors have permanent damage, e.g. hearing loss

Question 9

Describe encapsulated and non-encapsulated forms of H.influenza.

Answer 9

– Polysaccharide capsule (a,b,c,d,e,f, serotypes)
– Serotype B originally responsible for 95% of invasive infections, largely pediatric (<5 years).
– Haemophilus influenza type B i.e Hib

Question 10

what is the virulence related to capsule formation.

Answer 10

– PRP (polyribosyl ribotol phosphate) Capsule
– Protects bacteria from phagocytosis
– Reduces susceptibility to antibacterial role of serum

Question 11

what is the target for P2 and other outer membrane proteins?

Answer 11

Sialic acid oligosaccharides

in mucin

Question 12

what is the target for fimbriae/pili?

Answer 12

mucosal cells of nasopharynx

Question 13

what is the target for non-pillus adhesins?

Answer 13

mucosal cells of nasopharynx

Question 14

Describe the tissue invasion of H.influenza.

Answer 14

• H. influenza can be isolated from sub- epithelial layers without damaging epithelium.
– Passes between cell junctions Paracytosis
– Adheres & enters non-ciliated epithelium cells
– Viable bacteria detected in macrophage cells

Question 15

what are the antibiotic treatments for H.influenza diseases?

Answer 15

• Bronchitis- amoxycillin or erythromycin
• Pneumonia - flucloxacillin and amoxycillin
• meningitis - cephtriaxone

Question 16

What is the immunisation for H.influenza diseases?

Answer 16

– Hib (capsule type B) vaccine given at 2,3 & 4 months

Cell wall LPS also important for immunity

Question 17

What is pneumonia?

Answer 17

An acute inflammation of the lungs, often caused by inhaled pneumococci of the species Streptococcus pneumoniae. The alveoli and bronchiles of the lung become plugged with a fibrous exudate

Question 18

what are the 2 main cause of pneumonia?

Answer 18

• community-acquired pneumonias - (Streptococcus pneumoniae)

- Hospital -aquired pneumonias (Star aureus, gram negative bacilli)

Question 19

Describe the structure of strep pneumoniae.

Answer 19

•  Encapsulated Gm+ve cocci
•  Oval or lancet shaped
•  Arranged in pairs (diplococci)
•  Colonies α-heamolytic
–  Encapsulated strains large
•  Round & mucoid
–  Non encapsulated small
•  Flat
•  Fastidious (prefers 5% CO2)
–  Grows on media enriched with blood products, Catalase negative * requires catalase in the media to prevent build up of H2O2

Question 20

How do you identify S.pneumoniae?

Answer 20

• Deoxycholate (bile) sensitivity
• Optochin sensitivity
• Diplococci
• Gm +ve staining α-heamolytic (aerobic)

Question 21

what is S.pneumoniae a commensal of?

Answer 21

oropharynx

Question 22

what population does S.pneumoniae affect the most?

Answer 22

– Age related decrease in carriage – Peak 10 year olds (55%)

Question 23

How does S.pneumoniae bind?

Answer 23

Bound to surface carbohydrates :

• N-acetyl-glycosamine
• Neuraminidase A

Question 24

How is S. pneumoniae transferred?

Answer 24

horizontal transfer from resistant to susceptible

Question 25

What disease can S. pneumonia cause?

Answer 25

– Pneumonia – Ottis media – Meningitis (rare but significant)

Question 26

Describe pneumococcal pneumonia.

Answer 26

* Invasion of lower respiratory tract by aerosol * Normally bypass ciliated epithelial * Progress to alveolus, & cell wall promotes binding to cells expressing the Platelet Activating Factor receptor. * Teichoicacidsare exposed on cell surface & present in the cell wall

Question 27

what does pneumococcal pneumonia overcome?

Answer 27

* Overcomes IgA through the secretion of proteases | * Overcomes mucociliary escalator by the production of cytotoxin that kills ciliated epithelial cells (& Phagocytes

Question 28

Name the virulence factors of pneumococcal pneumonia.

Answer 28

> Cellwallinitiates inflammation – Teichoic acid & PG • Activate C5a • Alternative complement pathway ``` > Pneumolysin, pore forming (typeII) toxin > Hydrogen Peroxide > Phosphorycholine – Present on cell wall – Binds to PAF receptor – Induces receptor mediated endocytosis ```

Question 29

what is key to phagocytic survival?

Answer 29

``` • Capsule (smooth) – Key to virulence – Complex 83 serotypes – Inhibits Complement & Ab responses • Pneumolysin – Disrupts membranes – Inhibits oxidative burst ```

Question 30

What are symptoms of pneumonia?

Answer 30

* Normally preceded by 1-3 days of viral respiratory infection. * Abrupt onset * Severe shaking chill, sustained fever 39 ̊ to 41 ̊C * Productive cough with blood-tinged sputum * Chest pain (pleurisy) * Lobar pneumoniae confined to lower alveolar lobes

Question 31

what is the mortality rate of pneumonia?

Answer 31

5%

Question 32

what percentage of patent with pneumonia develop bacteraemia?

Answer 32

25-30%

Question 33

what is the treatment of pneumonia?

Answer 33

• Amoxycillin or Erythromycin – Resistance is now a major problem in USA • Cephtriaxol (chloramphenicol) for Meningitis

Question 34

what is the prevention and control of pneumonia ?

Answer 34

– PCV7, 7 surface antigens better for young children some limitations (racial). – Pneumococcal Vaccine 2, 4, 13 months – Anti-capsular vaccine consisting of 23 capsular polysaccharides covers 94% of all strains

Question 35

what is legionnaires disease (Pontiac fever)?

Answer 35

Atypical, acute lobar pneumonia with multi- system symptoms

Question 36

How does legionnaires disease (Pontiac fever) occur?

Answer 36

Occurs as sporadic cases or as outbreaks

Question 37

who does legionnaires disease (Pontiac fever) affect?

Answer 37

Immuno or pulmonary compromised

Question 38

what percentage of people exposed to legionnaires disease (Pontiac fever) develop the disease?

Answer 38

1-5%

Question 39

what is the case fatality of legionnaires disease (Pontiac fever)?

Answer 39

5-30%

Question 40

how is infection caused in legionnaires disease (Pontiac fever)?

Answer 40

– Inhalation of water droplets | – No person to person spread

Question 41

How can outbreaks of legionnaires disease (Pontiac fever) occur?

Answer 41

``` – Circulating water droplets – Whirlpool spars & warm water baths – Decorative fountains – Cooling Towers – Nebulisers & Humidifiers – Potting compost in Australia ```

Question 42

What are the symptoms of legionnaires disease (Pontiac fever)?

Answer 42

* Incubation period 2-10 days * Cough, fever, sweats, loss of appetite, headache, general pains. * Rapidly degenerates, yellow/green sputum can be stained with blood, tight chest, breathless, a sharp pain in the side of the chest * Confusion & diarrhea are possible symptoms * Complications include heart, brain & kidneys

Question 43

How would you describe Pontiac fever?

Answer 43

– Non-pneumonic Legionellosis | – Dry cough, Malaise, headache, fever, GI problems – Acute illness that resolves in 2-5 days

Question 44

what are the symptoms of non-respiratory infections?

Answer 44

– Wound infections after immersion in contaminated water – Hematogenous spread to extra pulmonary sites

Question 45

Describe the pathogenesis of Pontiac fever.

Answer 45

* Failure to clear inhaled organism (conc, virulence) * Contact with alveolar macrophages * Phagocytose bacteria, but phagosome fails to mature * L. pneumophila multiply within infected phagocyte * Lyse phagocyte and re-infect * Spread through lymph & blood

Question 46

Describe legionella pnemophila.

Answer 46

* Facultative intracellular parasite * Slender unencapsulated rods * Appear coccobacilliary in clinical material * Gm-ve but stain poorly with carbol fuchsin (Gimenez staining instead) * Strict aerobes * Fastidious

Question 47

What stimulates growth of legionella pneumophila and can grow inside amoebae and protozoa?

Answer 47

Blue-green algae

Question 48

Describe the diagnosis of Pontiac fever/ pneumonia.

Answer 48

- Culturing - direct Abody test - rRNA identification

Question 49

What is the treatment for pneumonia?

Answer 49

- Erythromycin | - Azithromycin

Question 50

what is the treatment for Pontiac fever?

Answer 50

not treated

Question 51

what is the control of Pontiac fever/pneumonia?

Answer 51

– Clean water systems, hot water systems monitored | – Hot water >50 ̊C as thrive between 20 ̊C to 45 ̊C

Question 52

what is the significance of legionella?

Answer 52

Legionella spp detected in dental water supplies. (UK, Germany, USA)

Question 53

Summary slide.

Answer 53

• Upper & Lower Respiratory tract infections • Haemophilus infleunza : – Gram-negative – Upper respiratory associated infectionto pneumonia – Capsular type & Hib vaccination • Streptococcus pneumonia – Usually follows viral infection – Single,doubly pneumonia &meningitis – Relatively recent control through vaccine but antibiotic resistance a problem • Legionella – Environmental source,grows within single celled eukaryotes, water lines, air conditioning etc.