Background 3 Flashcards
what makes up the upper respiratory tract
nasal cavity, pharynx, larynx
what makes up the lower respiratory tract
trachea, primary bronchi, lungs
list some acute upper respiratory tract infections
rhinitis, pharyngitis/tonsillitis and laryngitis - or the common cold
how long is the onset of symptoms for URTIs
1-3 days
how long do URTIs tend to last
7-10 days
What can pharyngitis/tonsillitis (strep throat) be caused by - where theres a sudden onset, fever, etc
beta haemolytic streptococcus group a
what symptoms dont present with strep throat
a runny nose, voice changes or cough
in unvaccinated patients what are some pathogens for URTIs?
bordetella pertussis or corynebacterium diphtheriae
what does bordetella pertussis cause
whooping cough
what does corynebacterium diphtheriae cause
diphtheria
how is a throat swab collected
sterile swap up and down the back of throat
once in the lab what is done with the throat swab
plated on blood agar, disc with antimicrobial agent (bacitracin) placed on surface of agar, incubate overnight @ 37
if the organisms causing diptheria are suspected where is the throat swab placed and for how long?
media containing tellurite, incubated in air for 48 hours at 37 degrees
if whooping cough is suspected as the URTI, what type of swab is taken
pernasal swab
where is a pernasal swab placed
on media containing charcoal
how long is a pernasal swab placed on charcoal and with what
it is incubated for 3-5 days in humid co2 at 37 degrees
after incubation of a URTI bacteria, the blood plate is observed for
beta haemolytic colonies
which type of bacteria is sensitive to bacitracin and doesnt grow close to the paper disc
streptococcus pyogenes
normal throat flora includes other haemolytic organisms but these are not sensitive to
bacitracin
the possible URTI bacteria can be serogrouped using
Lancefield streptococcal grouping kit
If a beta haemolytic streptocccus group a is isolated the clinicial is informed due to
potentially hazardous seleque and infectiousness of the organism
what can beta haemolytic streptococcus group a result in
rheumatic fever, glomerulonepheritis
what is diphtheria characterised by
sore throat, low fever, adherent membrane (pseudomembrane) on tonsils, pharynx
what can a pseudomembrane do
form across the airway and cause obstruction
what causes diptheria
coynebacterium diphtheriae
is a vaccination available for diphtheria?
yes
what type of bacteria is corynebacterium diphtheria
short gram positive rod
the toxin from corynebacterium diphtheria is detected using what type of test?
elek test
for lower respiratory tract infections what is the best sample to use
sputum
what are sputum samples placed on due to potential contamination with normal flora or upper resp
blood agar, choc agar, indicator agar and sabourauds agar
specimens for the isolation of mycobacterium tuberculosis and other mycobacteria are inoculated on which type of media
lowenstein jensen media
why are sputum samples diluted prior to routine culture or decontaminated prior to mycobacterial culture
because they are usually contaminated with normal resp tract flora
a sputum culture is mixed with what to digest the mucins in the specimens thus making it a homogeneous suspension
sputalysin
where is digested sputum placed
onto various agars
what type of disc is placed on chocolate agar with the sputum
optochin disc
the plates are exmamined the next day and what is picked off for appropriate biochemical and sensitivity testing
potential pathogens
what is an aid to the presumptive identification of streptococcus pneumoniae?
optochin
why is optochin a presumtpive identification for streptococcus pneumoniae?
s. pneumonia is sensitive to optochin and therefore has a zone of inhibition around the disc
what colour is streptococcus pneumoniae on blood agar or chocolate agar
it is green alpha haemolytic
is streptococcus pneumoniae gram pos or gram neg
gram pos
describe the morphology of streptococcus pneumoniae
it is diplococci
is streptococcus pneumoniae sensitive to optochin
yes
what colour is haemophilus influenzae on chocolate agar
grey colonies with a distinctive smell
does haemophilus influenzae grow on blood agar
no fam
is haemophilus influenzae oxidase pos or oxidase neg
slowly oxidase pos
what is haemophilus influenzae dependent upon
x and v dependent on x and v factors plate
what is legionella caused by
legionella pneumophila
how is legionella transmitted
by contaminated water from shower heads and air conditioning units
how many types of influenza virus are there
three virus a , b and c
what does influenza virus a cause
epidemic type
what does influenza type b cause
a miler disease usually in the winter
what does influenza type c cause
nothing, unlikely to be a human pathogen
what does the influenza virus envelope contain that can be used to type infleuzna
neuraminidase and haemagglutinin
how is influenza transmitted
through respiratory secretions
is vaccination possible with influenza
yes
the influenza vaccine contains inactivated virus from
two currently circulating strains of influenza a and a strain of influenza b
the influenza vaccine is a short lived vaccine and does not cover
all strains of influenza a
pre processing of sputum for mycobacterial culture involves decontaminating it with
sodium hydroxide and then buffered in distilled water
the solution for mycobacterial sputum cultures is centrigued at
300rpm for 30 minutes
what are the two main methods for culturing mycobacteria
culture on solid media - lowenstein jensen slopes, culture in liquid - similar to blood culture
what is the mycobacterial culture stained with once heat fixed
ziehl neelson (cold)
after 4-10 weeks of incubation of mycobacterial culture it becomes
positive
what is the growth of mycobacterial stained with to ensure it is acid alcohol fast?
ziehl neelson
a few weeks after the mycobacterial positive result what happens
sensitivity pattern and final identification of the species is confirmed
what is tuberculosis caused by
mycobacterium tuberculosis
what do symptoms of tuberculosis include
night sweats and coughing blood (haemoptysis)
what is the treatment for tuberculosis
multiple drug therapy for up to 12 months
why does mycobacterium tuberculosis not stain using gram stain
has a waxy cell wall
describe mycobacterium tubercolusos
acid alcohol fast rods
mycobacterium is slow growing, how long does it take
6-10 weeks
what specialist media is mycobacterium tuberculosis grown on
lowenstein-jensen
