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Virulence characteristics of food processing relevance in
isolates of Listeria monocytogenes and Escherichia
coli 0157: H7 strains isolated from ‘wara’ a West
African soft cheese
V. O. Adetunji
Department of
Veterinary Public Health and Preventive Veterinary Medicine,
University of Ibadan, Ibadan, Nigeria. E-mail:
vadetunji@gmail.com.
Accepted 13 January, 2010 |
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Three strains
of Escherichia coli 0157:H7 and eleven strains of
Listeria monocytogenes isolated from West African wara
cheese were analysed for cellulose production, fimbriae
formation, zetapotential and biofilm formation which are of
relevance in food processing. E. coli c produced no
fimbria, very low cellulose and significantly lower
zetapotential (-3.1) among the three strains. The L.
monocytogenes (b) had the highest zetapotential (-39.1)
and cellulose production at 24 h of incubation. Next to it
was L.
monocytogenes (f) which also had a higher
cellulose production at 72 h incubation. A positive
correlation exists between zetapotential and cellulose
production in the E. coli strains (R2 =
0.67) while Listeria monocytogenes strains gave a
negative correlation (R2 = -0.08). There was no
significant difference in biofilm formation in the L.
monocytogenes strains (P < 0.05), however the L.
monocytogenes (a) had the highest at 48 h incubation.
Weak positive correlation (R˛) values of 0.0397, 0.002 and
0.0011 were obtained for 24, 48 and 72 h incubation for
Listeria monocytogenes
counts (cfu/ml) and cellulose measurements. This study
further accentuate and confirmed the presence of E. coli
and L. monocytogenes
with
virulent factors that of relevance to the method of
processing
in West African soft cheese. The need for
an improved hygiene during processing and sale of this
product to prevent the transmission of these pathogenic
organisms to humans is therefore emphasized.
Key words:
West African soft cheese, Escherichia coli, Listeria
monocytogenes, virulent strains |
