00:01
The subject of this lecture are lung infections
and particularly pneumonia. The lung is exposed
to the environment continually, and there
are two main forms for that, one is through
the inhaled air that we will breath in every day,
repeatedly and the other is that is actually
connected to the upper respiratory tract,
and the upper respiratory tract is colonized
heavily with bacteria and this means that the lungs
are continually bombarded with microbial
pathogens of different sorts. Through inhaled
air it will breath in infected droplets from
people who are sneezing or coughing who are
infected with viruses, mycoplasma, chlamydia
or tuberculosis, and in addition, there are
fungal spores which are pretty ubiquitous
in the atmosphere, and will be breathed in
when you breathe normally.
00:48
Bacterial pathogens tend to come from the
back of the throat, so they are part of the
normal commensal flora living in the pharynx
and the upper respiratory tract, and they
get into the lung by microaspiration. Small
droplets of the secretions from the upper
respiratory tract make their way past the larynx,
down into the lungs, and could potentially
cause infection. However, because of our normal
immune mechanisms
the lungs, generally speaking, are kept sterile
despite this constant bombardment of microbial
organisms. But those immune mechanisms do
break down and infections are common, and
in fact, three of the most are common pathogens
causing infections across the world, and causing
death due to microbial infection across the
world, are due to respiratory tract infections,
Mycobacterium tuberculosis, Influenza A, those
are the subject of another talk on lung infections,
Streptococcus pneumoniae is the most
common cause of pneumonia.
01:48
About 3 million people per year, worldwide,
die as a result of pneumonia,
with a large portion of those due to
Streptococcus pneumoniae.