L5- Spread of respiratory infection

Question 1

What are the main types of viruses causing the common cold?

Answer 1

• Rhinovirus
• Influenza virus
• Coronavirus
• Echovirus
• Adenovirus

Question 2

What happens in infection with a common cold virus (upper respiratory tract infection)?

Answer 2

• Viruses have surface molecules that bind them to host cells
• Virus multiplication and spread occurs after entry
• Viral replication leads to acute inflammation and thus epithelial damage
• Causes increased vascular permeability and serum leakage into nasal secretions

Question 3

Which viruses can invade the lower respiratory tract?

Answer 3

• Influenza

* Respiratory syncytial virus

Question 4

What are other URTI’s?

Answer 4

• Pharyngitis and tonsilitis- adenoviruses, cytomegaloviruses, epstein-barr virus
• Pharyngitis and tonsilitis- S. pyogenes bacteria also causes scarlet and rheumatic fever

Question 5

What happens in diptheria infection?

Answer 5

• Infections usually affect tonsils, pharynx and less commonly the larynx
• Bacteria multiply on the surface of these sites and don’t deeply invade tissues
• Toxins destroy epithelial cells

Question 6

How does C. diptheriae toxin kill cells?

Answer 6

• Toxin has subunit A and B
• Toxin binds to host membrane and is taken in
• Cleavage of toxin frees subunit A
• Leads to ribosylation of elongation factor 2, addition of ADP-ribose halts protein synthesis and kills host cell
• Ulcer forms and extensive inflammation and swelling hampers breathing

Question 7

What are acute and chronic LRTI’s?

Answer 7

• Acute- short lasting infection with a rapid onset e.g pneumonia
• Chronic- frequently recurs or never resolves e.g tuberculosis

Question 8

Why is airborne transmission of TB effective?

Answer 8

• Actively infected people cough up enormous mycobacterial cell numbers
• M. TB has a wax rich outer coat that withstands drying to survive outside the body for long periods
• Infectious dose is a single bacterial cell

Question 9

What is the process of infection of TB?

Answer 9

• Phagocytosis of pathogen by alveolar macrophage
• Granuloma forms of mononuclear cells with many immune cells and collagen
• Infection contained until a factor adversely affects host immune system (old age, malnutrition, HIV)
• Granuloma bursts and release infectious bacilli into airways

Question 10

What is laryngitis and tracheitis?

Answer 10

• Hoarseness and sore throat
• Caused by parainfluenza virus, RSV, adenovirus
• Bacterial causes- less common but can be due to streptococci, staph. aureus and haemophilus influenzae

Question 11

What is the whooping cough?

Answer 11

• Severe disease of childhood
• Caused by bacterium bordetella pertussis
• Produces many toxins that damage cells

Question 12

What is pneumonia?

Answer 12

• Inflammation affecting the alveolar exchange region of the lungs
• Can be caused by viral, bacterial or other organisms
• bacteria most common e.g streptococcus pneumoniae, haemophilus influenzae
• Treatment by penicillin was good to treat s. pneumoniae