LECTURE OVERVIEW
• Normal flora of the URT
• Primary and secondary bacterial invaders
• Clinical manifestations, associated microorganisms and treatment options for common URTI
• Streptococcus pyogenes (Group A Strep): virulence factors
• Case study: laboratory diagnosis of streptoco...
OUR upper respiratory tract is heavily colonized with commensals.
The commensals we find in the upper respiratory tract are staphylococcus, candida albicans.
In the lower respiratory tract, we find no commensals, and this is because it should be a
sterile environment.
There should be no bacteria present in the deep lung where the alveoli are present, this
should be a sterile environment.
Occasionally we get pathogens that migrate into there but our immune system deals with it.
There should be no colonizing commensals in the lower respiratory tract, and if there are
something is wrong.
LECTURE OVERVIEW
• Normal flora of the URT
• Primary and secondary bacterial invaders
• Clinical manifestations, associated microorganisms and treatment options for
common URTI
• Streptococcus pyogenes (Group A Strep): virulence factors
• Case study: laboratory diagnosis of streptococcal (group A) tonsillitis; the diagnostic
template
• Important to know what the normal flora is so that we can see what it is we are
looking for.
• Extra-reading – other microorganisms causing infections in the upper respiratory
tract.
RESPIRATORY TRACT.
These are all the different infections of the respiratory tract that you can get.
Upper respiratory tract infections:
Sinustitis.
Ottis – infection of ear
Tonsilitis – infection of tonsils.
Epiglottitis.
Pharyngitis. – sore throat
Laryngitis. - infection of larynx.
Tracheitis- infection of trachea.
Below the trachea is where the lower respiratory tract begins.
Lower respiratory tract infections:
Bronchiolitis
Pleurisy- inflammation of the pleura, which is the sac around the outside of your lungs.
Bronchitis. – infection of the larger bronchi which goes down into the lungs.
Bronchiolitis- infection of the bronchioles. Impact's ability to be able to breathe.
Pneumonia- deep seated infection in the alveoli of the lungs which should have been a
sterile environment.
, COMMON BACTERIA ASSOCIATED WITH THE URT.
1. Common residents (>50% of normal people)
• Viridans streptococci
• Anaerobic microorganisms (eg.Bacteroides sp)
• Haemophilus influenzae
• Candida albicans (mouth)
2. Occasional residents (<10% of normal people)
• Streptococcus pyogenes (Group A Streptococcus)
• Streptococcus pneumoniae
3. Organisms associated with colonisation of URT following antibiotic treatment (<1%)
• Coliforms (E.coli)
• Pseudomonas sp.
• Candida albicans (oral thrush)
Common residents of the URT
Virdians streptococci- these are commensals that live in the URT and do not cause us
probleums.
Anaerobic microorganisms such as Bacteroides.
We expect to find these in the URT therefore if we conduct a throat swab we will expect to
see these things.
Occasional residents- these are the things we would expect to find less frequently.
Streptococcus pyogenes.
Streptococcus pneumoniae.
Organisms associated with colonization of URT following antibiotic treatment.
This is if you have had a broad-spectrum antibiotic and you have decolonized your upper
respiratory tract of the commensals that you would expect to find up there, with a broad-
spectrum antibiotic, it will indiscriminately eradicate bacteria in the upper respiratory tract.
As a result of this you can end up with coliforms infections like E.COLI, PSEUDOMONAS SP,
and candida albicans (oral thrush).
There will be an imbalance of the microbiota of the upper respiratory tract of the buccal
cavity, because you have killed off all the bacteria, using broad spectrum antibiotics, this
gives yeast in our mouth an opportunity to thrive because of the imbalance.
It is common for people who have broad spectrum antibiotics to develop thrush.
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