COMPARATIVE EFFECT OF BACTERIOPHAGE AND NISIN ON Listeria monocytogenes IN CHICKEN AND FISH
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Date
2014
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COLLEGE OF VETERINARY AND ANIMAL SCIENCES-MANNUTHY,THRISSUR
Abstract
In the present study, isolation of Listeria monocytogenes from chicken, fish and
sewage was undertaken to understand its prevalence using standard culture method and
confirmation by polymerase chain reaction (PCR). About 60 samples of chicken were
collected and screened for the evaluation of the L. monocytogenes and none of the
samples were found positive. Out of the 60 samples of fish collected from retail outlets
from markets of Thrissur, Kozhikode and Palakkad, 5 samples were found positive for
Listeria spp and out of which one isolate was confirmed as L.monocytogenes. The other
four samples were confirmed as L.innocua. All positive samples were obtained from the
municipal markets of Kozhikode. A total of 110 samples of sewage were screened for the
presence of L. monocytogenes and three positive samples were obtained and the isolates
were confirmed as L.innocua using PCR. The prevalence rate of Listeria in sewage was
found to be 8.33 per cent.
Sewage samples (110) were screened for the presence of Listeria specific
bacteriophages and plaques could be isolated from 18 samples. The standardisation of
PCR for the isolates was done using lysZ5gene. However, none of the isolated samples
were found positive to this gene and was detected only in the standard culture (ATCC23074 B1).
Comparative effect of bacteriophage and nisin on L.monocytogenes in chicken
and fish were assessed. Bacteriophage (103
pfu/ml) and nisin (1 per cent) was added on
the substrates at 10µl, 20µl and 30µl levels. Bacteriophage at 20µl level could completely
inhibit the growth of L.monocytogenes on day 14 and day 7 of storage in chicken and fish
respectively. But on addition of 30µl of nisin complete inhibition of bacteria was
observed on 14th and 3rd day of storage in chicken and fish. However regrowth of bacteria
was observed on further storage upto 21 days. Hence these antimicrobial substances have
a great potential to control the growth of bacteria in foods.
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