Agriculture Reference
In-Depth Information
3
Show pathological changes on post-mortem inspection
that lead to doubt as to the suitability of the meat for
human consumption, even though the animal was
found healthy on ante-mortem inspection
4
Have been shown by bacteriological tests to have been
excreting food-poisoning organisms prior to slaughter
or which emanate from a herd in which the presence of
food-poisoning organisms has been officially reported
5
Have not been eviscerated within 1 hour of slaughter
or where the parts of the slaughtered animal necessary
for post-mortem examination are absent or have
been handled in such a way as to make satisfactory
judgement impossible
Microbiological sampling and interpretation
Provided care is taken in the interpretation of results,
microbiological examination of meat is of value in the
assessment of wholesomeness, of the integrity of the
hygienic processing system and methods adopted during
slaughter, of dressing and processing techniques and of
the efficiency of methods of preservation. It can also
indicate the potential shelf life and help to identify
potential health hazards.
One of the difficulties associated with microbiological
examination is the lack of a standard technique accepted
and applied uniformly between different countries.
There are variations in sampling techniques, times of
sampling, culture media, parts of carcase to be exam-
ined, number of samples, which bacteria to assess, count-
ing methods, etc., all of which require standardisation if
comparisons are to be drawn and if the results are to be
uniformly interpreted. Sampling methodologies are
stipulated by both legislative and customer specifica-
tions, as are the interpretations of the analyses.
The bacterial status of the meat is dependent on a
number of factors, namely, the condition of the animal at
slaughter, the spread of contamination during slaughter
and the processing and temperature during storage and
distribution. Thus, as discussed previously, meat may be
contaminated with a range of bacteria which may be
significant in spoilage or may be pathogenic. The quality
and safety of meat is dictated by the nature and numbers
of spoilage and pathogenic species which form the total
flora. The microbiology of meat is therefore normally
considered under two criteria:
Total bacterial counts
(TBC) also known as aerobic
colony count (ACC)
,
aerobic plate count (APC) and total
viable count (TVC)
provide an indication of gross levels
of contamination.
Specific counts
of species of spoilage or pathogenic
bacteria of particular significance, for example,
Salmonella
spp., Enterobacteriaceae and generic
E. coli
.
Before microbiological analysis can be carried out,
it is necessary to obtain samples from the carcase under
investigation. This may be achieved by taking either
superficial or deep samples, or both if necessary.
Superficial samples
may be taken by removing primar-
ily destructive (surface samples) or non-destructive
(swab or sponge) samples. They provide an indication
of the levels of surface contamination present on the
carcase. Surface contamination may originate from
contact with contaminated surfaces, tools, operatives
and airborne contamination. These organisms are of
environmental as well as of faecal origin and generally
contain the organisms which will form a spoilage flora -
for example,
Pseudomonas
, lactic acid bacteria and
Material submitted
The following samples may be taken for submission to
the laboratory for bacteriological examination:
1
Two
complete muscles
, with their fascia, one from a
forequarter and one from a hindquarter, or cubes of
muscle, each side measuring not less than 7.5 cm
2
The
prescapular or axillary lymph node
from the other
forequarter of the carcase and the
internal iliac node
from the other hindquarter, including the surround-
ing fat and connective tissue of the nodes
3
The
spleen
, which should not be incised except in cases
where the organ is considerably enlarged, in which
case a piece as large as the hand should be taken.
4
A
kidney
5
In the case of small animals
, the whole
liver
with the
gall bladder; in other animals, a portion of liver twice
the size of a fist and including the portal vein, or the
caudate lobe and including the portal vein, and also
the portal lymph nodes and gall bladder
6
Parts showing pathological change
and which, in view
of their position, are suspected of containing patho-
genic bacteria, together with the associated lymph
nodes (e.g. in the case of pneumonia, a portion of the
lung and associated lymph nodes)
7
A portion of the
small intestine
along with a number of
mesenteric lymph nodes
in those cases where animals
have suffered from enteritis and have been reported to
be excretors of
Salmonella
organisms or animals known
to emanate from a herd infected with such pathogens.
Laboratory experience has shown that the
liver
frequently
contains intestinal bacteria which have gained entry by way
of the portal vein. As this invasion may occur after slaugh-
ter, the demonstration of organisms in the liver is of no real
significance unless the organisms isolated are of a specific
pathogenic type. Similarly, the
kidney
should theoretically
be of value in bacteriological examinations, but in practice,
bacterial invasion rarely occurs
post-mortem
.
