3. Resultsthe slaughterhouse, altogether 240 Campylobacter quantification
analyses were conducted on neck-skin samples (10 carcasses/batch,
six slaughter batches, sampled at 5 sampling positions along processing
line), 60 analyses for Campylobacter presence in corresponding
caeca and 8 analyses for Campylobacter presence in
slaughterhouse environment and equipment samples. The results
illustrating C. jejuni carcass contamination dynamics during
slaughtering and carcass processing of six monitored batches are
shown in Fig. 1.
The C. jejuni-negative flock was processed first on the slaughterhouse
day schedule. C. jejuni could not be isolated from the caeca
from this flock (n ¼ 10) and also carcasses from this batch (B4)
remained C. jejuni-negative throughout the slaughtering and also
following the chilling and packaging procedure. In other batches,
all caecal samples from broilers originating from C. jejuni -positive
farms (n ¼ 50) tested C. jejuni-positive also during slaughtering and
C. jejuni neck-skin contamination was confirmed in all corresponding
carcass samples from the evisceration room, with
Campylobacter numbers ranging from 1.6 103 (batch 2, pFR) to
1.4 104 CFU/g (batch 3, pPL; 10 carcasses per batch average;
Fig. 1). Enumeration results for the neck-skin sampled sequentially
at three successive sampling positions in the evisceration room
(shown as CFU/g average calculated from 50 positive carcasses from
the positive batches) revealed the highest contamination level at
the entrance to the evisceration room (pPL, i.e. after plucking:
average 6.6 103 C. jejuni CFU/g; 3.82 log), slightly lower immediately
after evisceration (pEV: average 6.1 103; 3.78 log) and the
lowest in the samples taken after the final carcass wash before
cooling (pFR: average 4 103; 3.6 log). A marked CFU reductionwas
observed in carcasses refrigerated for three days: 8.8 102 CFU/g;
2.94 log (a 4.5-fold decrease compared with the contamination
level detected at the exit from the evisceration room) and in carcasses
frozen for three days: 28 CFU/g; 1.44 log (a 143-fold
decrease, again compared with the contamination level detected
at the exit from the evisceration room). Analyses of individual
batches in the evisceration room show that two batches (B3 and B6)
had the highest CFU counts immediately at the first sampling point
(after plucking) while two batches (B2 and B5) peaked at the second
sampling point (after evisceration). Increasing CFU counts
were recorded at positions pPL and pEV when the three successive
batches were compared at each individual sampling point, both in
the spring and autumn samples.
All the slaughterhouse environment samples resulted
Campylobacter-negative before slaughtering and positive after
slaughtering. The only exception was the scalding tank water,
which remained negative also after slaughtering (data not
shown).
The genetic heterogeneity of C. jejuni isolates from caeca and
carcasses was low: three dominant pulsotypes (designated A, B and
C) were found in caeca and were usually typical for each batch (one
pulsotype per batch). The pulsotypes detected in the neck-skin
samples of a slaughtered batch corresponded to the pulsotypes
present in the caeca of that particular batch. The pulsotype typical
for the last slaughtered batch (pulsotype C from B3 in spring and
from B6 in autumn) also prevailed among the slaughterhouse
environment isolates, with two small additional genetic groups (D,
E) detected in the spring samples (Table 1).
On farms, C. jejuni was detected in broiler faeces in five out of six
flocks; one of the autumn flocks (B4) remained negative. At the
positive farms, C. jejuni was isolated from every faecal sample. At