الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
A total of 450 samples ( including 200 milk samples, 100 icecream
and 100 kariesh cheese samples and 50 nasal swabs from human
food handlers) were collected from different localities in Assiut
governorate, Egypt. The samples were examined bacteriologically for the
enumeration, isolation and identification of S. aureus, detection of
protein profiles of staphylococcal enterotoxins by SDS-PAGE and
detection of S. aureus enterotoxins genes (A, B, C, D, G and H) by PCR.
Using Baird-Parker medium (directly without enrichement on broth),
S. aureus could be detected in 44%, 80%, 60%, 54%, 50%, 30%, 80%,
60% and 80% of the examined samples of milk obtained directly from
animals, dairy farms, dairy shops and street distributers, street vendors’
ice-cream and small scale producers’ ice-cream, street distributers’ kariesh
cheese and grocery shops’ kariesh cheese and nasal swabs from human
food handlers, respectively. The maximum counts in milk and dairy
products were 2x105, 2.8x105, 2x104, 1.7x104, 4x103, 2x102, 5x105 and
2x105 cfu/ ml or gm, respectively. So, the highest percentage of S. aureus
was observed in milk samples taken from dairy farms and in kariesh
cheese from street distributers (80%) and the highest maximum count was
observed in kariesh cheese from street distributers (5x 105 cfu/gm).
After enrichement on Staphylococcus broth media, the percentages of
S. aureus on Baird- Parker agar were 36%, 72%, 56%, 48%, 40%, 30%,
76%, 56% and 70 % , respectively, while on Mannitol salt agar the
percentages of S. aureus were 40%, 70%, 56%, 50%, 26%, 22%, 58%,
44% and 80%, respectively. There was a significant difference between
the percentage of S. aureus isolated on B-PA and MSA in ice-cream and
cheese samples.
After confirmation of suspected S. aureus isolates by coagulase test
and latex agglutination test for clumping factor, protein A and capsular
polysaccharides, CPS was detected in 220 out of 450 total examined
samples (48.9%). It was detected in 100 out of 200 raw milk samples
(50%), 35 out of 100 samples of ice-cream (35%), 65 out of 100 samples
of kariesh cheese (65%) and 20 out of 50 nasal swabs from human
handlers of milk and its products (40%). So, the highest percentage of
CPS in different samples was observed in kariesh cheese.
SDS-PAGE was used to detect the toxigenic isolates out of the 220
coagulase positive S. aureus isolates (200 CPS isolates from milk and
dairy products+20 CPS isolates from human food handlers’ nasal swabs) .
Out of the 200 CPS isolates from milk and its products, 99 isolates
(49.5%) were toxigenic and out of the 20 nasal swabs, 10 isolates (50 %)
were toxigenic.
The percentage of enterotoxigenic isolates were 68.8%, 57.1%, 32%,
41.7%, 40.9%, 46.2%, 65.8%, 37% and 50% of the examined samples of
milk obtained directly from animals, dairy farms, dairy shops and street
distributers, street vendors’ ice-cream and small scale producers’ icecream,
street distributers’ kariesh cheese and grocery shops’ kariesh
cheese and nasal swabs from human food handlers, respectively. So, the
highest percentages of toxigenic isolates were observed in milk samples
taken directly from the animals (68.8%) and in kariesh cheese from street
distributers (65.8%).
PCR technique was applied to all toxigenic isolates ( 99 isolates
from milk and dairy products and 10 isolates from nasal swabs). All of
them were positive for one or more enterotoxin genes (A, B, C, D, G
and H)
In milk and dairy products, the major classical enterotoxin genotype
was SEA which was detected in 29/99 isolates ( 29.3%) followed by
SEC that was detected in 16/99 isolates (16.1%) and SED that was
detected in 10/99 isolates (10.1%) . Enterotoxin B gene was not
detected in any sample. For the newly described genes, SEG was
detected in 10 isolates (10.1%) followed by SE H which was detected in
7 isolates (7.1%). The mixed forms were found in eight isolates (8.1%)
for SE(A+C) genes another eight isolates (8.1%) for SE(A+C+D) genes
, five isolates (5.04%) for SE (A+G+H) genes and two isolates only
(2.02%) for SE(G+H) genes .
In the 10 toxigenic isolates of nasal swabs, the major classical
enterotoxin genotype was SEA that was detected in four isolates (40%) .
SEC and SED were detected in one isolate (10%). However, SEB could
not be detected. For the newly described genes one isolate (10%)
showed SEG and another one showed SEH gene (10%). In the mixed
forms, only one isolate (10%) showed SE(A+C) and another one
showed SE ( A+G+H).
The public health significance of the organism and the precautions,
which should be taken to control this organism in dairy industry as well
as the recommended sanitary measures, were also discussed