respiratory diseases

lecture 19 (module 4, lec 4)

through what method do respiratory diseases most efficiently spread

aerosols

what are the two methods bacteria have for preventing desiccation in aerosols

polysaccharide capsule and waxy cell wall

example of bacterial pathogen with a polysaccharide capsule

streptococcus pneumoniae

example of bacterial pathogen with a waxy cell wall

mycobacterum tuberculosis

serious disease results from infection where

lower respiratory tract

factors that contribute to success of establishing infection (3)

• intrinsic virulence of the pathogen

• dose of pathogen

• strength of defenses

effect of vaccines on respiratory viruses (e.g. MMR)

frequency of infection decreases

demographic targets of S. pneumoniae

immunocompromised people and elderly

3 diseases caused by S. pneumoniae

1. Pneumonia

2. Meningitis

3. Otitis media

what occurs first to allow S. pneumoniae to be the secondary infection

Influenza A kills ciliated airway cells

what is the general role of cilia on the airway cells

interactions with secreted mucus

what is the S. pneumoniae capsule

polysaccharide structure outside the cell wall

what does the capsule prevent?

phagocytosis and killing of the bacterium by macrophages

what is C3b

element of human ‘complement system’

what is the function of C3b

binds to the peptidoglycan of the cell wall and stimulates ingestion by macrophages

host defence mechanisms that prevent most bacteria from colonising the lower respiratory tract (2)

• ciliated airway cells

• ingestion and killing by lung macrophages

what is the main effect of S. pneumoniae infection

inhibition of O2 exchange and blood not becoming oxygenated

why are vaccines for S. pneumoniae difficult to develop

variation in capsule type, therefore different antibodies are needed