Background 2 Flashcards
in sensitivity testing after how many hours will the lawn of bacteria be visible
24 hours
if an organism is sensitive to an anitibiotic there will be what around the disc?
a zone of clearing
if the organsm is resistant to the antibiotic it will
grow close to the disc
the size of the zone is dependent on the size of the antibiotic molecule and how far it can
diffuse in the agar
what is meningitis
the inflammation of the meninges caused by bac, fungi or viruses
which bacteria has become a less common cause of meningitis due to vaccination
haemophilus influenzae type b
how is meningitis diagnosed
CSF taken by lumbar puncture
a sample of CSF is examined for the presence of
red and white cells
why is CSF gram stained
to look for the presence of possible organisms as CSF is usually sterile
what is done on day 1 of receiving the csf sample
cell count, centrifuged films are made to differentiate white cells and a gram stain is performed, sample plated out to blood and choc agar + sensitivity test
what is done on day 2 of receiving the csf sample
plates read, gram stained again, simple biochemistry performed, confirmatory tests set up
what is done on day 3 of receiving a csf sample
further tests interpreated, result issues to ward
is neisseria meningitidis gram negative or gram positive
gram negative
what does neisseria meningitidis appear like
intracellular diplococci
is neisseria meningitidis oxidase positive or oxidase negative
positive
what else can neisseria meningitidis cause
septicaemia
septicaemia is most common in the young by neisseria meningitidis and meningitis is common in
adolescents
what is available against some strains of neisseria meningitidis
a vaccine
haemophilus influenzae type b is gram negative or gram positive
gram negative
describe the morphology of haemophilus influenzae type b
rod
where does haemophilus influenzae type b grow
on chocolate agar but not on blood agar
haemophilus influenzae type b is dependent on what when tested on a factors plate?
x and v dependent
does haemophilus influenzae type b have a vaccine
yes
is Streptococcus pneumoniae gram positive or gram negative
gram positive
describe the morphology of Streptococcus pneumoniae
diplococci
what is Streptococcus pneumoniae sensitive to
optochin
Streptococcus pneumoniae strains causing meningitis often have what
a capsule
meningitis caused by Streptococcus pneumoniae is most common in the
very young and elderly
what is a capsulated yeast which can cause meningitis in patients with HIV
cryptococcus neoformans
which staining allows cryptococcus neoformans to be seen in CSF
india ink staining highlights the capsule
which agar does cryptococcus neoformans grow on
sabarauds agar
how may hours before sufficient bacterial growth is seen with blood cultures
at least 4 hours can be up to 3 or 4 days
when there is a positive signal from the machine regarding blood cultures what happens
a sample is taken from the bottle and gram stained
once a sample is gram stained from a blood culture what happens
sample plated onto blood culture and other plates as relevant and a sensitivity test prepared
what happens on day 2 of blood culture labs
plates from day 1 are read, gram stained again, biochemistry is performed, sensitivity results analysed
