الفهرس 
Contents
Biochemical reactionsOnly 14 pages are availabe for public view
 |  | from | 113 |  |  |
| | | from | 113 | | |
Abstract
A total of 270 random samples of raw milk and some milk products including 90 raw milk samples (Dairy farms, Dairy shops and Street vendors), 60 cheese samples (Damietta and Kareish ), 90 ice cream samples (Large scale, Small scale and Street vendors) (30 samples each) and 30 milk
powder samples, were collected from different localities in Assiut City.
These samples were examined bacteriologically for enumeration, isolation
and identification of Citrobacter, Proteus and Serratia species using two
media: MacConkey agar and Eosin Methylene Blue (EMB) agar media.
The average counts of Citrobacter species on MacConkey agar were
2.8×102, 8.4×105 & 3.3×105; 6.3×105 and 1.9×104 & 9.2×103 cfu/ml or g for
Dairy farms, Dairy shops, Street vendors raw milk samples, Kareish cheese,
Small scale and Street vendors ice cream samples, respectively. While on
EMB agar, they were 1.2×102 , 3.0×106 & 7.8×105 ; 2.0×106 and 1.0×104 &
1.0×104 cfu/ml or g for the concerning samples, respectively, Damietta
cheese samples were negative for Citrobacter species on both media. The
obtained results revealed that 3 (10.0%), 4 (13.3%), 5 (16.7%), 2 (6.7%), 10
(33.3%), 0 (0%), 0 (0%), 5 (16.7%) and 4 (13.3%) of the examined samples
of Dairy farms, Dairy shops, Street vendors raw milk, Damietta, Kareish
cheese, Large scale, Small scale, Street vendors ice cream and milk powder
samples, respectively, were contaminated with Citrobacter species on
MacConkey agar (Isolation method). However, the incidence of Citrobacter
species on EMB agar was 2 (6.7%) in Dairy farms, 6 (20.0%) in Dairy
shops, 7 (23.3%) in Street vendors milk samples, 1 (3.3%) and 11 (36.7%) in
Damietta and Kareish cheese samples, respectively, 0 (0%) in Large scale, 6
(20.0%) in Small scale, 3 (10.0%) in Street vendors ice cream and 1 (3.3%)
in milk powder samples (Isolation method). Citrobacter freundii was
detected in percentages: 6.7, 10.0 & 6.7; 3.3 & 13.3; 0, 10.0 & 6.7 and 0% in
Dairy farm, Dairy shops, Street vendors raw milk, Damietta , Kareish
cheese, Large scale, Small scale and Street vendors ice cream and milk
powder, respectively, by using MacConkey agar. On EMB agar, the
previous organism was existed in samples of Dairy farm, Dairy shops, Street
vendors raw milk, Damietta cheese, Kareish cheese, Large scale, Small
scale, Street vendors ice cream and milk powder as: 6.7, 10.0 & 10.0; 3.3 &
20.0; 0, 10.0 & 3.3 and 3.3%, respectively. Regarding Citrobacter diversus
was recorded as 3.3, 3.3 & 10.0% in Dairy farm, Dairy shops and Street
vendors raw milk, respectively. 3.3 & 20.0% of Damietta cheese and
Kareish cheese respectively. The organism was detected 0, 6.7 & 6.7 and 0%
in Large scale, Small scale, Street vendors ice cream and milk powder,
respectively, on MacConkey agar. While, by using EMB agar the organism
was represented as 0, 10.0 & 13.3; 0 & 16.7; 0, 10.0 & 6.7 and 0% in the
previous examined samples.
By using MacConkey agar, the average counts of Proteus species in
Dairy shops and Street vendors raw milk samples, were 1.6×105and 1.8×104
cfu/ ml, 2.3×105 cfu/g, 1.4×104 and 2.9×104 cfu/g, for Kareish cheese, Small
scale and Street vendors ice cream samples, respectively. On the other hand,
the average counts on EMB agar a were 1.2×102 , 1.5×105& 1.5×105;
1.6×105& 1.0×105 and 4.7×103 & 4.0×104 cells / ml for Dairy farms, Dairy
shops, Street vendors milk samples, Damietta, Kareish cheese, Small scale
and Street vendors ice cream samples, respectively. None of the Large scale
ice cream samples and milk powder samples were contaminated with
Citrobacter and Proteus organisms by using both media, also all of the
examined Dairy farms milk and Damietta cheese samples were free from
Proteus species on MacConkey agar. Furthermore, the incidences of Proteus
species on MacConkey agar were 0.0, 16.7 and 6.7% in Dairy farms, Dairy
shops and Street vendors raw milk samples, respectively. In Damietta and
Kareish cheese: one sample (3.3%) and 4 samples (13.3%) were
contaminated with Proteus species, respectively. While, none of the
examined samples of Large scale were positive for Proteus species, 4
(13.3%) and 8 (26.7%) for Small scale and Street vendors ice cream
samples, respectively. All of the examined samples of milk powder were
free from this microorganism. On the other hand, by using EMB agar,
Proteus species were represented as 6.7, 10.0 & 13.3; 13.3 &6.7; 0, 16.7
&20.0 and 0% of Dairy farms, Dairy shops, Street vendors milk samples,
Damietta, Kareish cheese, Large scale, Small scale, Street vendors ice cream
and milk powder samples, respectively (Isolation method). None of the
examined Dairy farm raw milk samples were represented Proteus vulgaris,
Proteus mirabilis, Proteus morganii and Proteus rettgerii on MacConkey
agar. Proteus vulgaris was detected only in Dairy shops, Street vendors raw
milk and Small scale ice cream in the same percentages (3.3%) but in
Kareish cheese and Street vendors ice cream was 10.0 and 6.7%,
respectively. Proteus mirabilis in Dairy shops, Street vendors raw milk,
Damietta, Kareish cheese, Large scale, Small scale and Street vendors ice
cream and milk powder were 10.0 & 3.3; 3.3 & 3.3; 0, 10.0 & 13.3 and 0%,
respectively. Proteus morganii only detected in Street vendors ice cream
3.3% but Proteus retttgerii was represented in the same percentage in Dairy
shops and Street vendors ice cream (3.3%). On the other hand, by using
EMB agar, Proteus morganii was not detected in all of examined samples.
While, Proteus vulgaris in Dairy farm and Street vendors raw milk was 3.3
and 10.0%, respectively, 3.3% in both of Damietta cheese and Small scale
ice cream and 10.0% in Street vendors ice cream. Moreover, Proteus
mirabilis was represented in percentages 3.3% in both of Dairy shops and
Street vendors raw milk, 6.6% only in Kareish cheese, in Small scale and
Street vendors ice cream in the same percentages 10.0%. Proteus rettgerii
was detected in Dairy farm, Dairy shops, Damietta cheese and Small scale
ice cream as 3.3, 6.7, 10.0 and 3.3%, respectively.
Concerning Serratia species, the average counts in Dairy farms, Dairy
shops and Street vendors milk samples by using MacConkey agar were
1.0×103, 1.4×106 & 4.6×105bacteria / ml, respectively. On EMB agar, the
average values were 1.9×106 and 1.2×106 cfu/ml for Dairy shops and Street
vendors milk samples, respectively. The average counts in case of Kareish
cheese samples on MacConkey and EMB agars media were 1.0×106 and
2.2×106 cfu/g, respectively. In Damietta cheese samples, 1.5×105 cfu/g was
the average count by using MacConkey agar. Small scale ice cream samples,
the average value on MacConkey agar was 5.9×102 cfu/g, while in Street
vendors samples, the average counts on MacConkey and EMB agars were
5.1×103 and 2.1×105 cfu/g, respectively. Serratia species had average count
of 8.3×103 cfu/g in milk powder samples by using EMB agar. No Serratia
species could be detected on EMB agar in Dairy farms milk samples and
Damietta cheese. On both media, these organisms were not recovered from
Large scale samples of ice cream. Moreover, all of examined samples of
milk powder were free from Serratia species by using MacConkey agar. The
percentages of Serratia species on MacConkey agar in Dairy farms, Dairy
shops and Street vendors raw milk samples were 6.7, 6.7 and 20.0%,
respectively. Two samples (6.7%) each of Damietta and Kareish cheese, one
sample (3.3%) of Large scale ice cream, 2 (6.7%) samples of Small scale, 7
(23.3%) samples of Street vendors ice cream and one (3.3%) sample of milk
powder contained these bacteria. On the other hand, the organism was
detected on EMB agar in percentages 1 (3.3), 3 (10.0) & 8 (26.6); 2 (6.7) &
3 (10.0); 1 (3.3), 1 (3.3) & 3 (10.0) and 2 (6.7%) samples in Dairy farm,
Dairy shops, Street vendors raw milk, Damietta, Kareish cheese, Large
scale, Small scale, Street vendors ice cream and milk powder samples,
respectively (Isolation method). By using MacConkey agar, Serratia
marcescens was detected as 3.3, 6.7, 13.3, 6.7, 3.3, 3.3, 13.3 and 3.3% in
Dairy farm, Dairy shops , Street vendors raw milk, Kareish cheese, Large
scale, Small scale, Street vendors ice cream and milk powder, respectively.
While Serratia liquefaciens was represented in the same result 3.3% in
Dairy farm, Street vendors raw milk, Damietta cheese and Small scale ice
cream. Also, Serratia rubidae was detected only in Street vendors raw milk,
Damietta cheese as 3.3%, while, 10.0% in Street vendors ice cream samples.
On the other hand, on EMB agar, no Serratia rubidae was detected in all of
examined samples. Serratia marcescens was recorded in Dairy farms, Dairy
shops, Street vendors raw milk, Kareish cheese, Small scale, Street vendors
ice cream and milk powder samples as 3.3, 6.7, 16.7, 6.7, 3.3, 6.7 and 6.6%,
respectively. While Serratia liquefaciens was represented 3.3, 10.0, 3.3, 3.3,
6.7 and 3.3% in Dairy shops, Street vendors raw milk, Damietta, Kareish
cheese, Large scale and small scale scale ice cream samples.
from the obvious results, it is clear that Citrobacter, Proteus and
Serratia species were well isolated on EMB agar in both types of cheese
samples, while MacConkey agar is the best medium for isolating the 3
species of the organisms in Street vendors ice cream samples. By
comparing the efficiency of the two media used for the enumeration and
isolation of Citrobacter, Proteus and Serratia species, it was found that
MacConkey and EMB agars media are considered complementary for
each other.
These results revealed the presence of Citrobacter, Proteus and
Serratia species in the examined samples of raw milk and other milk
products. This could be attributed to neglected sanitary control during
handling, manufacture and distribution. The economic importance and the
public health significance of these organisms and steps, which should be
taken to control their occurrence in the dairy industry, as well as, the
recommended sanitary measures were also dis