Volume 22 • Issue 01 • 2018
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Place wrapped slides in a sealed sample
envelope to avoid formalin-fume
contamination.
Formalin-fume contamination severely
compromises the efficacy of the FAT
Smear Examination
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Examine Diff-Quick stain first to determine
if any clostridial-like organisms present, if
so estimate numbers.
Only 4 species of clostridia available
in the FAT assay (Clostridium chauvoei,
Clostridium novyi, Clostridium septicum)
Must correlate FAT results to all other
assays performed.
Avoid basing diagnosis solely on the FAT
result.
False negative FAT results
1. Poor bacterial recovery (reason why
examine Diff-Quick slide 1st)
2. Low bacterial load at sample site,
pathology initiated by clostridial toxins
False positive results
1. Post mortal proliferation
2. Concurrent Clostridium perfringens
myositis
Anaerobic culture
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A block of subcutaneous and/or muscle
tissue/fluid/charcoal swab is collected from
the site where the impression smears weere
prepared.
There was no significant difference in the
ability to isolate clostridia between these
sample types.
All samples need to have oxygen excluded as
soon as possible
For subcutaneous / muscle tissues, block
sample should be a minimum of 4cm3, as
this favours the maintenance of anaerobic
conditions at the centre of the block.
Place tissue block in a sample envelope
which is then folded to exclude oxygen and
sealed.
Fluid samples are collected into a sterile
syringe, air is then expelled and the needle
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bent back on itself or plugged.
When using charcoal swabs ensure that the
swab is inserted deep into the transport
medium.
Solid tissue samples should be transported
at 4ºC, while fluids should not be sent on ice
as oxygen dissolves better in fluids at low
temperatures.
Histopathology
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Artefactual changes as a consequence
of asynchronous contraction of muscle
following immersion of muscle tissue in
formalin can interfere with interpretation of
interstitial emphysema or oedema.
Collect block of subcutaneous tissue /
muscle, that must not exceed 1cm in
thicknes