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Summary
Prevalence of L. monocytogenes from Farm and Fresh Meat at Slaughterhouse
Title of Project
and Epidemiological Analysis by Molecular Method
Key Words
Farm, Slaughterhouse, Listeria monocytogenes, Virulence gene, Genetic homology
Institute
Sookmyung Women’s University
Project Leader
Yohan Yoon
Project Period
2014. 10. 21 ∼ 2015. 11. 30
Listeria monocytogenes has been recognized as important foodborne pathogen. The pathogen
is isolated from fresh meat and poultry, and it can be transmitted to processed meats. Hence,
the prevalence of L. monocytogenes needs to be evaluated through food chain. The objective
of present study was to investigate prevalence of L. monocytogenes in slaughterhouses and
farm, and genetic correlations of the isolates to elucidate the correlations of transformation from
farm to human. Two hundred samples from cecum, and cattle and pig carcasses were collected
from 9 slaughterhouses(central, SW, SE Korea), and 11 human isolates were obtained from
domestic hospitals of university and Korea center for disease control and prevention(CDC).
2,018 of farm samples were collected from feces(677), soil(680), silage(647) and sludge(14) of
domestic farms including L. monocytogenes-positive farms, and it was collected seasonally(more
than two times). L. monocytogenes were identified by amplifying Listeria-specific genes (hly and
prs) by PCR and eventually confirmed by 16s rRNA analysis. The presence of virulence genes
such as actA, inlA, inlB, plcB, and hlyA were analyzed by PCR, and the serotypes were
determined by multiplex-PCR and agglutination assay. Genetic correlations were also evaluated
by PFGE patterns formed by Asc I, and the PFGE patterns were compared among slaughter
isolates and the slaughter isolates were compared with the patterns from human isolates. Of
290 slaughterhouse samples, 15 samples (5.17%) were L. monocytogenes positive, and including
previously-isolated 72 isolates, 87 slaughterhouse isolates were used for further experiments.
three of L. monocytogenes was isolated from farm samples(0.15%). All isolates had
virulence-related genes such as actA, inlA, inlB, plcB and hlyA. Interestingly, size of actA in
slaughterhouse isolates was different from the one of human isolates. Serotypes of human
isolates were mainly 1/2a(18%), 1/2b(27%), and 4b(27%) which is known as foodborne
disease-related serotypes, while 1/2c(72.4%) was most frequent serotype in slaughterhouse
isolates. Prevalence of 1/2a and 1/2b was 9.2% and 13.8% respectively, and serotype of the
isolates from farms was 3a, 4ab has low pathogenic characteristic. Genetic correlations among
slaughterhouse isolates mostly ranged 85% to 100%, and some of the isolates had genetic
correlations with human isolates(95%-100%). However, there was no geographical correlation
and had different actA size. These results indicate that there is very low possibility for
transmission from farm to carcasses in slaughter houses and from carcasses to human because
the prevalence of L. monocytogenes in farms were very low, and the isolates had different size
of actA. Thus, it can be suggested that L. monocytogenes contamination on carcasses could be
caused by cross-contamination, which can be supported by no isolates from cecum samples.
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